General aspects of Wound Healing
Selvig KA, Torabinejad M. Wound healing after mucoperiosteal surgery in the cat. J Endod 1996;22:507-515.
Novaes AB Jr, Novaes AB. Superficial bone resorption: a negative or positive factor in wound healing ? Intern J Periodont Restor Dent 1996; 16: 79-86
Wirthlin M, Yeager J, Hancock EB, Gaugler R. The healing of gingival wounds in miniature swine. J. Periodontol. 51:318-327, 1980.
Ohta S, Yamada S, Matuzaka K, Inoue T. The behavior of stem cells and progenitor cells in the periodontal ligament during wound healing as observed using immunohistochemical methods.J Periodontal Res. 2008 Aug 14. [Epub ahead of print]
Bosch JA, Engeland CG, Cacioppo JT, Marucha PT. Depressive symptoms predict mucosal wound healing. Psychosom Med. 2007 Sep-Oct;69(7):597-605. Epub 2007 Aug 31.
Engeland CG, Bosch JA, Cacioppo JT, Marucha PT. Mucosal wound healing: the roles of age and sex. Arch Surg. 2006 Dec;141(12):1193-7; discussion 1198.
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Aukhil I. Biology of wound healing. Periodontol 2000 2000;22:44-50. (Review)
What is the healing response of various oral tissues in contact with implanted tooth roots? What factors seem to influence the type of healing tissue found adjacent to tooth roots?
Houston F, Sarhed G, Nyman S, et al. Healing after root reimplantation in the monkey. J. Clin. Periodontol. 12:716-727, 1985.
Karring T, Nyman S, Lindhe J. Healing following implantation of periodontitis - affected roots into bone tissue. J. Clin. Periodontol. 7:96-105, 1980.
Nyman S, Karring T, Lindhe J, Planten S. Healing following implantation of periodontitis- affected roots into gingival connective tissue. J. Clin. Periodontol. 7:394-401, 1980.
Isidor F, Karring T, Nyman S, Lindhe J. New attachment - reattachment following reconstructive periodontal surgery. J Clin Periodontol 1985;12:728-735.
Squier CA, Collins P. The relationship between soft tissue attachment, epithelial downgrowth and surface porosity. J. Periodontal Res. 16:424- , 1981.
Blumenthal NM, Singiser RT. The enhancement of guided tissue regeneration by altering root surface topography. Int J Periodont Rest Dent 1993; 13:361-370.
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Blomlof L, Friskopp J, et al. Influence of granulation tissue, dental calculus and contaminated root cementum on periodontal wound healing. J Clin Periodontol 1989;16:27-32.
Pettersson E, Aukhil I. Citric acid conditioning of roots affects guided tissue regeneration in experimental periodontal wounds. J. Periodontal Res. 21:543- , 1986
Wang H, Hamilton R, Castelli W, Chiego D, Smith B. Effect of root conditioning on periodontal wound healing with and without guided tissue regeneration: A pilot study. Histological evaluation. Int J Periodont Rest Dent 1993;13:551-561.
What are the basic principles/tenets of GTR?
Bjorn H, et al. Tissue regeneration in patients with periodontal disease. Odontol. Revy. 16: 317-326, 1965.
Ellegard B, et al. New periodontal attachment procedure based on retardation of epithelial migration. J. Clin. Periodontol. 1:75-88, 1974.
McHugh WD. The effects of exclusion of epithelium from healing periodontal pockets. J. Periodontol. 59:750-757, 1988.
Wikesjo UME, Nilveus RE, Selvig KA. Significance of early healing events on periodontal repair. A review. J Periodontol 1992; 63:158-165. (Review)
Do local or systemic antibiotics influence the clinical and/or histologic results with GTR? How does bacterial colonization on the membrane influence the outcome of GTR?
Machtei EE, Dunford RG, Norderyd OM, Zambon JJ, Genco RJ. Guided tissue regeneration and anti-infective therapy in the treatment of Class II furcation defects. J Periodontol 1993; 64:968-973.
Demolon I, Persson G, Ammons W, Johnson R. Effects of antibiotic treatment on clinical conditions with guided tissue regeneration: One-year results. J Periodontol 1994;65:713-717
Dastoor SF, Travan S, Neiva RF, Rayburn LA, Giannobile WV, Wang HL. Effect of adjunctive systemic azithromycin with periodontal surgery in the treatment of chronic periodontitis in smokers: a pilot study. J Periodontol. 2007 Oct;78(10):1887-96
Sander L, Voigt E, Frandsen G, Arnbjerg D, Warrer K, Karring T. Effect of local metronidazole application on periodontal healing following guided tissue regeneration. Clinical findings. J Periodontol 1994;65:914-920
Mombelli A, Zappa U, Bragger NP. Systemic antimicrobial treatment and guided tissue regeneration. Clinical and microbiological effects in furcation defects. J Clin Periodontol 1996; 23: 386-396
Nowzari H, MacDonald ES, et al. The dynamics of microbial colonization of barrier membranes for guided tissue regeneration. J Periodontol 1996;67:694-702.
DeSanctis M, Zucchelli G, Clauser C. Bacterial colonization of bioabsorbable barrier material and periodontal regeneration. J Periodontol 1996;67: 1193-1200
What are some of the biologic modulators you know of that re used in periodontal regeneration? Discuss their applications and success in periodontal regenerative therapy.
Dennison K, Vallone D, Pinero G, Rittman B, Caffesse R. Differential effect of TGF-B1 and PDGF on proliferation of periodontal ligament cells and gingival fibroblasts. J Periodontol 1994:65:641-648
Sigurdsson T, Lee M, Kubota K, Turek T, Wozney J, Wikesjo U. Periodontal repair in dogs: Recombinant human bone morphogenetic protein-2 significantly enhances periodontal regeneration. J Periodontol 1995;66:131-138
Terranova V, Wikesjo U. Extracellular matrices and polypeptide growth factors as mediators of function of cells of the periodontium. A review. J. Periodontol. 58:371, 1987. (Review)
Bosshardt DD. Biological mediators and periodontal regeneration: a review of enamel matrix proteins at the cellular and molecular levels. J Clin Periodontol. 2008 Sep;35(8 Suppl):87-105. (Review).
Carlson NE, Roach JR, RB. Platelet-rich plasma. Clinical applications in dentistry. JADA 2002;133:1383-1386. (Review).
Marx RE, Carlson ER, et al. Platelet-rich plasma: growth factor enhancement for bone grafts. Oral Surg, Oral Med, Oral Path 1998;85:638-646.
Cochran DL, Wozney JM. Biological mediators for periodontal regeneration. Periodontol 2000. 1999 Feb;19:40-58. (Review).
Marx RE. Platelet-rich plasma: evidence to support its use. J Oral Maxillofac Surg. 2004 Apr;62(4):489-96.
Kao RT, Murakami S, Beirne OR. The use of biologic mediators and tissue engineering in dentistry. Periodontol 2000. 2009;50:127-53.
General aspects of Wound Healing
Purpose: To examine reattachment of the mucoperiosteal flap tissues to the cervical root surfaces and the denuded surfaces of the alveolar process in the cat.
Materials and methods: Ten adult cats were used. A full thickness triangular flap with a single vertical incision distal of the cuspid and an intrasulcular incision extending to the distal of the second premolar were elevated bucally on all 4 quads. Flaps were retracted for 30 minutes placing a wet gauze between the flap and the bone surface, then reapproximated and sutured.
Block biopsies were obtained at 1, 3 days, 1, 2 and 4 weeks. From each specimen sections representing a location buccal to one of the roots were selected for analysis. Measurements of wound dimensions, distance (if present) between the wound space and the hard tissues, tissue reaction – epithelial healing, organization of the blood clot, connective tissue healing, hard tissue resorption and repair were assessed.
Results: The incision had severed the dentogingival fibers at a distance 0.5-2mm from the root surface. In no distance had the cementum surface been completely denuded. Variables amount of soft tissue remained on the bone close to the bone crest area, but the bone was completely denuded in the region of the alveolar mucosa.
In operated specimens:
1 day: wound space that separates the flap from the root retained fibers and the cortical surface of the alveolar process. Wound space contained a clot composed of fibrin mesh and erythrocytes and a distinct lining of fibrin along the wound margins. Leukocytes showed higher density in periphery areas than in the center of the clot.
3 days: incisional wound was bridged by an epithelial layer 2 to 3 cells in thickness. Collagen within the clot.
1week: epithelialization of the wound surface appeared complete. A fine network of new collagen and distinct fiber structures were identified. A cell-rich granulation tissue or incompletely organized coagulum was present on the bone surface. Superficial bone resorption.
2-4weeks: healing of gingival connective tissue and junctional epithelium appeared complete and little further change could be detected between week 2 and 4. Gingival margin had a rounded profile as compared with the more knife-edge profile of the gingival margin of the unoperated ligual aspect. Location of the incision was frequently demarcated by deep epithelial projection. At 4 weeks gingival fiber structure appeared indistinguishable from than on the unoperated lingual aspect of the same teeth. Although fiber repair was complete at the bone crest, areas of persisting coagulum and inflammatory reaction were present adjacent to the bone surface in mucosal areas in 2 and 4 weeks at several specimens. Bone repair was evident at 4 weeks.
Conclusion: The rate of healing in more rapid in areas where the wound bed consists of some CT (Free gingival area and where there are intact periosteal fibers). Reattachment to denuded bone is delayed and the slowest rate of tissue repair occurs in the alveolar mucosa region.
The slower reparative reaction along the buccal surface of the alveolar process is, presumably, a consequence of the inert nature of this cortical surface. The compact nature of the cortical bone, and consequently the limited nutritional supply to the granulation tissue from this surface, as well as the sparseness of fibers attachng the periosteum to the bone that made it very easy to elevate the mucoperiosteal flaps, may account for a poor wound bed for formation and attachment of new collagen fibers. Thus, the potential for adequate response to injury may be less than in the supracrestal region).
Purpose: To examine the importance of the participation of the bone in wound healing and to discuss the possible result of removal of the periosteum.
D: Discussion on wound healing patterns and the effect of stimulation factors on wound healing patterns. The author reaches the following conclusions based on reviewing the literature:
Periosteum, in addition to protecting the bone surface, actively participates in the healing process through its rich vascularization.
Histologically all of the elements in the periosteum are also present in the marrow spaces because the endosteum is quite similar to the periosteum, reason why marrow spaces represent a source of regeneration.
Early superficial bone resorption (1st and 2nd week after surgery) generally considered a negative factor, may in fact be a positive factor and contributes to the regeneration process (up to 2 weeks), since it opens the communication between the elements of the marrow spaces and area treated.
Small bone perforations (even through the periosteum) induce an earlier participation of the marrow spaces and prevent a delay in healing time
CT reconstruction, including a return of the vessels that are removed will be complete after bone exposure.
In favor of removing the periosteum and perforating the cortical plate to promote communication between marrow spaces and the receptor bed surfaced for bone regeneration thru the periosteum.
P: To quantitatively evaluate the healing of standard incisional wounds through the AG and the gingival margin, and wounds of partial excision of the dentogingival junction (DGJ).
M&M: Wounds were made in 6 miniature swine. Vertical Incision, Vert. Inc. + sulcular incisions (pedicle flap) w/ excision of sulcular epithelium. The healing from the 1st to the 14th day was described clinically and histologically. The wounds on the right side had the ends of tension gauges inserted in the pedicle flaps that were sharpened to resemble surgical skin hooks. The hooks were inserted mesial and distal to the vertical incisions. The vertical incisions were freshened and tension was applied and the point of rupture of the gingiva from the attachment to the tooth was noted.
R: Clinically, at day 7 both simple incision and pedicle flap wounds were practically indistinguishable from unwounded tissue. Histologic findings of normal unwounded gingival tissue presented parakeratinized gingival margins. Cervical cementum was cellular. Pedicle flap at day 0 had appearance of typical internal bevel incision. At 2 days there was a thin fibrin clot on the cut CT surface, epithelial migration begun at the basal layer of the cut oral epithelium. At 7 days increased cellularity of CT, average epithelization from gingival margin to CEJ was 97%. At 14 days regeneration of epithelium was complete (99%). In the pedicle flaps there was linear, SS, increase in rupture strengths from day 0-14. At day 14 equal to unwounded gingiva. In the vertical incisions no rupture analysis was sig.
BL: Basal cells of oral sulcular epithelium are the main elements in the regeneration of the new DGJ. Early wound strength is due to epithelial adhesion and not to fibrin of clot. The close adaptation of the flap to the tooth contributes to early wound strength recovery.
Purpose: To identify stem cells or progenitor cells in the periodontal ligament and to investigate their behavior in the PD: during wound healing of bone defects created experimentally in the alveolar process.
Materials and methods: 25 rats were used in the study. A skin incision was made along the inferior border of the mandible, and the anterior portion of the masseter muscle was reflected to expose the lateral surface of the alveolar bone overlying the mesial root of the 1st molar. Then an intradentinal cavity about 1mm in diameter was made using a round bur, debris was washed out and flaps were sutured. Animals were sacrificed 1, 3, 5, 7 and 14 days after the operation and histologic specimen were prepared for light microscopy observations. Anti-CD44s , anti-CD34 and anti-c-KIT were used as primary antibodies in immunohistochemistry. (CD44 is adhesion molecule expressed by bone marrow mesenchymal stem cells. CD34 and c-KIT that are produced by bone marrow hematopoietic stem cells). 10 rats were given a single injection of 5-bromo-2-deoxyuridine (incorporated into nuclear DNA during the S phase, used to label proliferating cells) 1d after the operation and killed after 2, 4, 6d later. Samples were incubated to block endogenous peroxidase activity and anti-5-bromo-2-deoxyuridine were used as the primary antibody.
PCNA and Cbfa-1 scores were calculated for each of the 5 areas described in the picture above.
Cbfa-1: a transcription factor activated at the onset of osteogenesis and considered to be a robust marker of osteogenic commitment.
STRO-1:early marker of different bone marrow mesenchymal stem cells and pre-osteogenice populations. Expression of this molecule is progressively lost after differentiation into mature osteoblasts in vitro. Therefore Cbfa-1 and STRO-1 may be progenitor cells.
PCNA: it is required for DNA synthesis
Results:
Control: A few Cd34-, c-KIT and CD44 positive cells were observed in cells of alveolar bone marrow, but not in cells of PDL ligament. Cbfa-1-positive cells were observed in cells at the surface of the bone and around blood vessels in the apical side of the PDL.
Experimental:
On Day 1 many STRO-1, PCNA- and Cbfa-1-positive cells were observed on the cut surface of the crown side PDL and apical side PDL.
At 3 days, PCNA- and Cbfa-1 positive cells appeared in all 3 PDL cavities.
At 5 days CD44s-positive cells were found along the alveolar bone in the alveolar bone cavity and numerous PCNA- and Cbfa-1-positive cells were observed to be present diffusely in the cavities.
At 7 days, CD34- and c-KIT-positive cells were found close to the dentin in the dentin cavity, CD44s-positive cells were not found in the dentin cavity.
At 14 days, newly formed cementum was observed along the dentin surface in the dentin cavity, and newly formed PDL. PCNA-positive cells were observed mainly in the dentin cavity and Cbfa-1-positive cells were observed in the newly formed bone and blood vessels.
Findings suggest that bone marrow stem cells (CD44s, CD34- and C-KIT-positive) , do not exist in the PDL and that these cells might not be involved in the regeneration of the periodontium.
5-bromo-2-deoxyuridine-positive cells were observed in the PDL 3 days after the operation, a number of them in the PDL cavity at 5 days and osteoblasts, fibroblasts, and endothelial cells in the newly formed bone and blood vessels in the dentin cavity were positive at 6 days.
Conclusion: Bone marrow mesenchymal stem cells and bone marrow hematopoietic stem cells in the bone marrow may not be involved in the regeneration of the periodontium. Cells that migrate from the residual PDL regenerate new alveolar bone at an early stage and the regeneration around dentin in the cavity occurs later than in other parts of the PDL.
Purpose: To investigate the associations between loneliness (the negative emotional experience of being socially isolated), dysphoria (experiencing depressive symptoms), and wound healing.
Materials and methods:
193 undergraduates (mean age = 20.1 years, range: 18-31 years, n = 98 females) were recruited.
The selection criteria resulted in a study sample enriched with participants high on loneliness and/or depressive scores.
A 3.5 mm circular oral wound was placed on the hard palate under local anesthesia, approximately 3 mm from the marginal gingiva of the first and seconds molars, using a 3.5 mm tissue punch.
Psychological measures used included the BDI-SF: a widely used and well-validated self-report measure of depressive symptoms.
Loneliness was measured using the UCLA-R Loneliness Scale.
Wounds were videographed daily between approximately 10 am and 11 am using an intra-oral camera.
Participants were signaled 7 times a day by a preprogrammed wristwatch and instructed to immediately take a saliva sample by placing a cotton roll in the mouth until soaked, and complete a short questionnaire on current mood and activities.
Determinations were made using Cortisol Coat-A-Count RIA kits.
Results:
The number of valid cases was 183. At 7 days post-wounding, approximately 50% of all participants were healed.
Logistic regression showed a significant association between depressive symptoms and the time needed to heal. Scores on the UCLA-R Loneliness Scale and cortisol secretion were not significantly associated with healing status.
BL: There is a 50% increased likelihood of having slower healing with each standard deviation increase in depressive symptoms.
Engeland 2006 ARTICLE age and sex
P: To examine age and sex differences in the healing of standardized mucosal wounds created on the hard palate.
M&M: 212 pts divided into 2 groups based on age. Younger: aged 18-35 y.o (52M, 67F) Older: aged 50-88 y.o (33M, 60F). Demographic and HHX questionnaires were administered to each pt. High surgical risk and immediate needs pts were excluded. Local anesthesia administered, and a periodontist created palatal wounds b/w the 1st and 2nd molars ~ 3mm from marginal gingival. Wounds were created using a 3.5mm tissue punch. A scalpel was subsequently used to remove surface epithelium, creating a uniform wound 1.5mm in depth. Wounds were left undressed and pts were instructed to resume normal toothbrushing protocols immediately (NSSD in OH b/w 2 grps or sexes). Wounds were videographed at 24 hr intervals for 1 week or until an inspector considered them to be healed.
R: Older adults showed significantly slower rate of healing compared to the younger population. This remained consistent even among pts taking prescription meds or having existing medical conditions. Regardless of pts age, women healed more slowly than men. These results were all independent of demographic factors including alcohol/nicotine use, BMI, or ethnicity.
BL: Wound healing is delayed significantly in older adults and women
Wong 1996 ARTICLE review articles
Integrated processes responsible for soft tissue healing (Review)
Organization of events in tissue healing:
Phases I and II: Wounding and Inflammation
Tissue injury initiates the inflammatory phase through the activation of several cascades including the coagulation cascade, the tissue complement system, and kinin cascade
The different inflammatory cascades alter the local environment, produce vasodilation of adjacent vessels, decrease the pH level and oxygen tension, and increase local lactate concentrations.
Phase III proliferation:
Activated products of the complement system attract macrophages to the wound. Growth factors secreted by macrophages in turn stimulate migration of fibroblasts and epithelial and endothelial cells. Fibroblast proliferation and secretion of different types of collagen in combination with the development of new blood vessels (angiogenesis) from endothelial cells leads to the formation of granulation. The different cell types present after epidermal wounding include fibroblasts, endothelial cells, and epithelial cells.
Phase IV: Remodeling:
Soft tissue repair involves a conversion of the initial healing tissues to the formation of scar tissue
Selected Growth Factors in Wound Healing:
Platelet-derived growth factor (PDGF) is stored in the α -granules of platelets and released after activation of the platelets at sites of tissue injury. They are chemotactic for fibroblasts and monocytes as well as mitogenic for fibroblasts and vascular smooth muscle cells. Activates marcophages. Stimulates fibrolasts to secrete type I and III collagen.
Transforming growth factor- β (TGF- β): chemotactic to monocites, neutrophils, T-cells, fibroblasts, and marcophages as well as mitogenic to fibroblast, mesenchymal cells. Accelerate collagen deposition. Modulates PDGF, FDF, TNK, IL-1, enhances deposition ECM activity.
Basic fibroblast growth factor (bFGF): Chemotactic and mitogenic: fibroblasts, endothelial cells. Promotes angiogenesis.
Tumor necrosis factor-Alpha (TNF- α): Macrophages can stimulate angiogenesis by expressing TNF- α
P: Basic concepts of wound healing based on two reviews.
Disc: Initially there is a temporary repair characterized by a sequence of steps (which often overlap):
Clot formation: Start with injury to the blood vessels. The fibrin rich clot is formed by coagulation and platelet aggregation. Role: reservoir of growth factors and cytokines (start signalling for repair), protect wound and provisional matrix for cell formation.
Recruitment of inflammatory cells: Neutrophils: Clean the wound of foreign particles, debris and bact using enzymes and toxic oxygen. Release pro-inflammatory cytokines for recruitment of fibroblast and keratinocytes. Last for a few days. Monocytes: Eventually become macrophages to continue with phagocytosis and GF and cytokines release.
A family of cell adhesion receptors will activate the epithelial cells and keratinocytes from the border of the wound (basal layer) to migrate to cover the denuded surfaces (or form a junction at the tooth interface).
Fibroblasts and endothelial cells from the connective invade the clot to form a granulation tissue. For cells to invade the clot they need migration paths. For dissolution of this fibrin barrier the enzyme plasmin and MMP’s are activated.
Granulation tissue: Form by new capillaries, macrophages, fibroblasts and loose connective tissue. Occur around day 4. Cytokines induce proliferation of fibroblast and extracellular matrix, which in turn function in a reciprocal manner. Migration of fibroblast into the wound is also stimulated by platelet derived grown factors and TGF-b.
Maturation of the healing tissue matrix is seen along w/ contraction or scaring: The provisional matrix is replaced by new, collagen-rich matrix, synthetized by the fibroblast migrating into the wound. Around 7-10d some fibroblasts transform into myofibroblasts, which generate strong contractile forces that is responsible for wound contraction. In the final stages, these 2 cells are decreased by death cells.
Angiogenesis: Is a complex process. Several grown factor are important for it induction.
Growth factors in wound healing:
|
GROWTH FACTOR |
SOURCE |
EFFECT |
|
Fibroblast Growth factor 1,2,4 |
Macrophages, endoth cells |
Fibrobst prolif & angiogenesis |
|
TGF |
Macrophages, keratinocytes |
Re- epithelization |
|
TGF 1 and 2 |
Platelets & macrophages |
Fibro & macroph chemotaxis |
|
Epidermal GF |
Platelets |
Re-epithelization |
|
Platelet-derived GF |
Platelets, macroph, keratinocytes |
Fibro & macroph chemotaxis, fibro prolif, matrix synthesis. |
|
Interleukin 1 and |
Neutroph |
Actv Gr. Factor expression in macrophages, keratinocytes and fibroblasts |
|
Tumor necrosis factor |
Neuthophils |
Actv Gr. Fact expression in…. |
|
Insulin GF |
Plasma, platelets |
Endoth and fibrob prolif |
|
Vascular endoth GF |
Keratinocytes, macroph |
Angiogenesis. |
|
Keratinocyte GF |
Dermal fibroblasts |
Keratinocyte prolif |
What is the healing response of various oral tissues in contact with implanted tooth roots? What factors seem to influence the type of healing tissue found adjacent to tooth roots?
P: To evaluate the regenerative potential of the perio tissues following root re-implantation using a model which excluded the epithelium (epi) from interfering with healing.
M/M: 5 adult monkeys, 3 different groups: (all teeth had RCT)
Grp I: 12 teeth extracted following elevation of FTF and crowns removed and re-implanted
Grp II: 8 teeth same as (I) but buccal alveolar bone removed to half original height & notch at level of bone crest.
Grp III: 10 teeth same as (II) but buccal root surface planed till the surgically created crest.
Sacrificed at 6 months and histological evaluation using microscope.
Results: Complete fibrous reattachment (re-att) when PDL preserved (Grp I, II). In Grp III: when root remained submerged for entire period, fibrous re-att in the apical parts of the roots where PDL was preserved; new cementum formation in 45% of the planed root length. Coronal to new cementum, roots were covered by CT (fibers parallel to root surface), & root resorption occurred coronal to CT where roots remained submerged for the entire period. New bone form in (Groups II & III). No relationship b/w amount of CT re-att or new att and new alv bone.
Disc: When buccal bone was reduced but PDL was retained, healing resulted in a complete restitution of CTA in grp I and II. In group III, the potential of new att formation could be studied. When epi was excluded, healing was characterized by new att & varying degree of bone tissue regrowth. In some roots, apical migration of epi occurred, but was limited. In this case root resorption is possible.
BL: New CTA can form w/o a concomitant regeneration of alveolar bone. Existing PDL fibers served as barrier to epi migration. Epi will prevent resorption after removal of PDL. Bone regrowth and PDL regeneration are unrelated phenomena.
Purpose: To study whether new connective tissue attachment can occur to root surfaces which have been exposed to the oral environment and subsequently implanted into bone tissue.
Materials and methods: 3 beagle dogs were used. A total of 24 roots. In order to induce periodontal breakdown cotton ligatures were placed around mandibular premolars. The mandibular 2nd premolars, 1st molars and maxillary 3rd incisors were extracted to provide sites for root implantation. The ligatures were changed every 2nd week and replaced in sub-g position. When the destruction of the supportive tissues had progressed to a level corresponding to half the length of the roots, the ligatures were removed. 9-12 weeks later the crowns were cut off and multirooted teeth were root resected to obtain single roots. Pulp tissue was removed under aseptic conditions and root canals were filled with resin in chloroform and gutta-percha. FTF were raised , exposed parts of the roots received Sc/Rp and were notched (level of marginal bone), then extracted, 2-3mm of the apical parts of the roots were resected. Roots were implanted into prepared bony cavities and completely covered by flaps created to exclude epithelial migration. Animals were sacrificed at 1, 2, and 3 months.
Results: As a result of extensive root resorption the notches created could not always be relocated in the specimens. These roots were arbitrarily divided into one apical and one coronal portion.
Apical portion of the roots: Areas of regeneration and areas of repair involving root resorption and ankylosis could be identified. In most specimens areas with regeneration predominated. In areas with reestablished PDL, a layer of newly formed cementum was seen on the root surface. Collagen fibers were found to insert into new cementum and adjacent bone. In some specimens a small amount of new cementum was formed. Small superficial resorption cavities were found in the old cementum layer. In areas of ankylosis, portions of dentin and cementum were replaced with bone.
Coronal portion of the roots: No signs of true regeneration. Healing had occurred by repair phenomena (root resorption and ankylosis). Resorption lacunae were found in the dentin close to the resected coronal surface.
Conclusion: It cannot be determined whether new CT attachment can be achieved to root surfaces that have been exposed to oral environment. It can be suggested though that in addition to apical migration of junctional epithelium and subgingival plaque, the cells that repopulate the wounded area may jeopardize new CT attachment.
Purpose: To examine if a new connective tissue attachment can be established on a previously periodontally involved root surface, located in contact with gingival connective tissue during healing.
Materials and methods:
28 teeth in 1 dog (beagle) and 2 monkeys (Macaca) were subjected to experimental periodontal tissue breakdown by placing cotton floss ligatures or orthodontic elastics around the teeth until 50% of the supporting tissues had been lost.
Following resection of the crown and division of multirooted teeth, the roots were root filled (gutta-percha) and SRP. The roots were extracted and implanted horizontally into grooves
prepared in the alveolar bone of edentulous areas, leaving ½ of the circumference covered by
connective tissue of the repositioned flap.
The animals were sacrificed at 2 and 3 months.
Results:
No differences were found between the observation periods 2 and 3 months
No fundamental differences found between dog and monkey specymens
Gingival connective tissue, which during healing was in contact with a root surface, previously
exposed to the oral environment, failed to form a new connective tissue attachment to this surface.
In areas of the roots where the periodontal ligament tissue had been preserved, a fibrous attachment (re-attachment) consistently developed between the root and the adjacent gingival connective tissue.
Granulation tissue derived from alveolar bone induced root resorption and ankylosis.
Cells from gingival connective tissue established contact with the “exposed” root surface but induced neither formation of cementum nor connective tissue attachment. The present findings confirm the previous study by Karring et al.(1980).
BL: Gingival connective tissue does not possess the ability to establish conditions that enable the formation of a new connective tissue attachment.
P: To evaluate if conditions for reformation of a CT attachment are less favorable on root surfaces which have lost their fibrous attachment due to perio disease than on root surfaces surgically deprived of their attachment apparatus.
M&M: 4 Squirrel monkeys, 2 maxillary and 2 mandibular teeth (experiment). Perio breakdown was produced and allowed to progress to the mid-root level around 1 of the experimental teeth in both maxilla and mandible by placing elastic ligatures around the neck of these teeth. 3 months after removal of the ligatures, the crown of the teeth was resected, epithelial and granulation tissues were removed. Using a diamond bur, circumferential defects were produced around the remaining 2 experimental teeth after resection of the crown. The root cementum on both groups of teeth was removed to the level of the reduced bone height. All roots were submerged to complete coverage by a mucosal flap. The animals were sacrificed after 3 months.
R: No histological differences in the result of healing were discernible between the specimens of previously periodontitis affected roots & roots with surgically created defects. New cementum with inserting collagen fibers had formed in the apical part of the instrumented surface in both groups of teeth. NSSD between average length of the newly formed cementum.
BL: The potentials for reformation of fibrous attachment are similar on planed root surfaces previously exposed to perio disease and on surfaces surgically deprived of their attachment apparatus.
Purpose: To explore the relationship between the porosity of a surface and the rate of epithelial migration and connective tissue attachment at that surface.
Materials and methods: Pigs were used. The surgery was performed in the back, adjacent to the vertebral column. Strips of Millipore filter material 3x8mm were placed in individual incisions made through the skin. Pore sizes of 0.025, 2.2, 0.65, 1.0, 1.2, 3.0, 7.0 and 8.0μm were selected and strips of each of the filter sizes were inserted in 5 pigs for 1, 2, 4, 6 or 8 weeks. Filters were removed when a full thickness biopsy of skin was removed containing the filter within it. Specimens were examined to measure the distance between the tip of the epithelial downgrowth along the filter surface and the level of the adjacent epidermal – connective tissue junction. Filters were divided in 4 groups (0.025μm-0.2μm, 0.65μm-1μm, 1.2μm-3μm, 7μm, 8μm) for statistical analysis.
Results: In all specimens epidermis showed a tendency to migrate along the surface of the implanted filter. The epithelium formed the lining of a narrow crevice extending a variable distance down the filter. The extent of migration along the filter at any time interval appeared to be related to porosity, with the epithelium moving faster along filters with a small pore size. The filters with the larger pore sizes (more than 3μm) were markedly infiltrated by connective tissue cells and fine collagen fibrils, while the ones with the smallest pore sizes, the CT fibers were aligned parallel to the surface and formed a capsule. The epithelium migrated at a more rapid rate during the first 2 weeks after implantation.
Conclusion: Results support assertions that intact periodontal fibers are a deterrent to the apical migration of junctional epithelium. It also seems likely that procedures aimed at promoting CT reattachment to the tooth may serve to limit apical migration of epithelium and represent rational periodontal therapy.
BG: It has been found in vitro, that a root surface modified by ultrasonic (US) grooving provided preferential adherence & enhanced migration of cultured fibroblasts.
Purpose : The perio fenestration model was used to evaluate the ability of vertical root surface grooving to enhance & direct cell outgrowth & subsequent formation of new attachment at 2- & 6- wk healing intervals in dogs.
Materials and methods:
4 mongrel dogs had SRP & CHX b/f fenestration model (as described by Melcher & modified by Caton) used to exclude epithelium & CT from the healing wound.
Horizontal incision at MGJ, fenestrations made in bone over PM’s w/round burs. On 1 side of the mandible, 3 control fenestrations were made. On the experimental side, vertical grooves from apical-coronal borders of the wound were made w/ round bur. On the control side, no grooving, only root planning (RP).
E-PTFE membranes used to cover all wounds. Animals received Flocillin post-op. Dogs sacrificed at 2 & 6 wks.
Results:
Grooved wounds showed greater cementum & bone formation (more bone than CEM), primarily in early wound. In addition, a more mature attachment at 6 wks (PDL oriented perpendicular & composed of thick dense fiber bundles inserting into new CEM). No ankylosis was observed.
BL: Grooving the root surface may enhance initial cell adhesion & proliferation, thereby accelerating new attachment formation. The use of grooves on exposed root surface
P: To substantiate the hypothesis that connective tissue attachment to root surface appeared to be dependent upon chronological sequence of healing related to fibrin & collagen interactions using histology.
M&M: 4 squirrel monkeys, 24 teeth extracted & re-implanted after: (1) surgically denuding the coronal root surface of CT fibers & cementum by root planing or (2) surgical denudation followed by topical citric acid (CA). 3 specimens were evaluated by histology at 1, 3, 7, & 21 days after re-implantation.
R: Epithelial tissue migrated rapidly along the denuded, non-acid treated, root surfaces, reached the alveolar crest at 3 days, and was to the level of root denudation at 21 days. Epithelium did not migrate apically along CA treated root surfaces. At 1 & 3 days, inflammatory cells were meshed in a fibrin network that appeared to be attached to the root surface. At 7 and 21 days, the region had repopulated with CT cells & collagen fibers had replaced the fibrin. No new cementum formation was seen.
D: CA conditioning, by exposing the dentin collagen fibrils, created an environment whereby collagen fibers were surrounding the wound – a situation analogous to the present after incisional wounding.
BL: The fibrin network is the initial stage in wound healing and precedes the collagen attachment to the root surface.
Blomlof 1989 ARTICLE chemical cleansing
P: To explore the chemical cleansing procedure of periodontally-involved cementum and the importance of granulation tissue and calculus removal for the establishment of a new attachment.
M&M: Ligature induced periodontitis on 8 monkeys around 2nd premolar, first and second molars on both jaws. One month after removal of the ligatures, the experimental teeth were subjected to different periodontal treatment procedures as following
Detergent(a)/No detergent rinse(b) 0.5 ml 2% sodium-N-Lauroyl sarcosine (Fluka), plaque control, no surgery
Surgery with granulation tissue removal, Detergent(a)/No detergent(b), plaque control
Surgery with granulation tissue and calculus removal, Detergent(a)/No detergent(b), plaque control
Surgery with granulation tissue, calculus, and contaminated root cementum removal, Detergent(a)/No detergent(b), plaque control,
Animals were sacrificed 9 months after surgical treatment. Increased alveolar bone height(X), transseptal fiber thickness(Y), and new attachment(X+Y) were measured. Tetracycline was used to label newly-formed mineralized tissue such as alveolar bone and cementum by injecting to animals 7, 14, and 21 days after surgery.
** New attachment: only where newly-formed cementum detected in the supracrestal area in association with the transseptal fiber bundle, inserted into newly formed cementum
R: Found increase in alveolar bone height and thickness of transseptal fiber bundle in all experiments. However, new attachment found only after treatments 2a and 3a (Surgery with granulation tissue, granulation tissue and calculus removal / detergent / plaque control). SSD between 2a, 3a and remaining groups. NSSD between 2a and 3a (2 mm new attachment).
BL:
No improvement in periodontal healing can be obtained by merely rinsing the pocket with detergent, compared to plaque removal alone.
New attachment including formation of new adhering cementum will result only on chemically-conditioned cementum surfaces.
Small amounts of granulation tissue or calculus left does not influence healing.
P: To study effects of citric acid root conditioning on new connective tissue attachment formation.
M&M: Fenestration wounds of standard sizes (4 mm x 3 mm) were made on the buccal aspects of 2nd and 3rd Mandibular premolars in 6 beagle dogs. Exposed root surface were curetted and conditioned with citric acid pH-1 (8 experimental) or distilled water (7 control) for 3 minutes, and covered wounds with Millipore filter. Dogs were sacrificed and histologically analyzed at 3 months of healing.
R:
The percentage of surgically denuded root surface showing new cementum with inserting fibers was significantly lower in citric acid group compared to controls.
Coronal and apical areas of controls had SSD higher percentage root surface with new attachment
Root resorption was seen in both groups but more in experimental group.
Ankylosis was significantly more in experimental group.
No difference in bone regeneration (both regenerated in equal extend).
New cementum was not strongly attached to dentin.
BL: Both citric acid conditioning and no conditioning can result in new attachment but more undesirable features of wound healing are associated with the use of citric acid. Agreed with findings of Nyman et al 1982; Aukhil et al 1983. Gottlow et al 1984. Also agrees with Melcher ’70 concept of progenitor cells are located in healthy periodontal ligament.
Purpose: The purpose of the following study was to evaluate, in a closed periodontal wound, the sequence of histologic events that resulted in the formation and attachment of new connective tissue. The specific objectives in this histologic evaluation were (I) to identify the source of the fibroblast profileration and migration at the wound site; (2) ta quantitate the cementum deposition and evaluate the attachment and functional orientation of young collagenous fibers into the newly deposited cementum; 3) to quantitate the osteogenesis response attained in surgically produced alveolar bone fenestrations; and (4) to evaluate the role of membrane barrier implants in the healing process of closed periodontal wounds.
M&M: 4 Mongrel adult dogs with healthy periodontia with full complement of teeth. Two weeks prior to surgery, each dog was sedated with 2.5% sodium thiamylal solution and the teeth were thoroughly scaled and polished. OH maintained with daily brushing, 0.12% CHX five times per week. Teeth in all quadrants of the mouth (including canines, second, third, and fourth premolars, and first molars) were used. They were assigned randomly to one of the following six treatment modalities: (1) citric acid with a non resorbable membrane barrier; (2) citric acid without membrane barrier (CA); (3) tetracycline with membrane barrier; (4) tetracycline without membrane barrier (TC); (5) control (sterile water) with membrane barrier; and (6) control (sterile water) without membrane barrier. The surgical procedures were conducted in each quadrant of each dog at different time periods. Intracrevicular, FTF mucoperiosteal flaps with raised with vertical-re leasing incisions extending to the mucogingival junctions at the mesial and distal ends of the predetermined surgical sites. Fenestrations cut through bone to expose the middle third of the roots. The cementum was completely removed and dentin was exposed. Defects rinsed and blotted dry with sterile cotton pellets. Citric acid (phH 1), tetracycline HCI (50 mg/mL), or sterile water (SW) was then topically applied to the dentinal defect for 3 minutes. Nonresorbable membranes were randomly placed over half of the defects. Animals were killed at 1, 3, 7, or 21 days and routine histologic examinations with hematoxylin and eosin staining followed.
R: PDL and alveolar bone are the main source of fibroblast proliferation and migration as well as extracellular matrix formation at the initial stages of healing. At 21 days, citric acid stimulated more cementogenesis than tetracycline or sterile water. Also, while the tetracycline influenced the maximal deposition of alveolar bone, no differences in healing were found between the citric acid, tetracycline, and sterile water with and without the use of membrane barriers.
C: 1. Fibroblast proliferation and migration with extracellular matrix formation was evident 24 hours after surgery and came from both the apical and coronal borders of the defect. 2. New cementoid deposition was present at day 21 and was highest in the CA-treated groups. 3. At 7 days specimens with implanted membranes showed delayed healing, evidenced by persistence of residual fibrin at the implanted membrane side along with the presence of few RBCs and PMNs. At 21 days no differences in healing were found between the CA, TC, or SW groups, with or without the use of membrane barriers.
What are the basic principles/tenets of GTR?
Bjorn 1965 NO ARTICLE
Purpose: To investigate regeneration of periodontal tissues in cases where the root cementum had been devoided of organic connection with other parts of the periodontal tissues for a long time and where the epithelium was excluded from the healing process.
Materials and methods: 11 teeth in 7 patients were studied. All teeth were vital and were recommended for extraction because of mobility and deep pockets. The teeth were treated by root canal therapy. After 3-6 weeks, periodontal surgery was performed. The crown was cut off, entrance to the canal was sealed with amalgam filling and root planing was performed. A flap free of granulation tissue and consisting entirely of mucous membrane was raised, extended over the cut surface and sutured to the lingual marginal gingiva. Serial single and stereoscopic radiographs were taken. Changes in marginal bone height was determined. 3 histologic samples were studied. Control periods varied from 3-12 months.
Results: Healing had taken place by formation of cementum, PDL, and alveolar bone. 2 showed a functionally oriented apparatus, while the 3rd showed areas of resorption and inflammation. The resorption was probably due to the fact that the root was totally luxated during the root planing. Infection from root canal may also be a contributing factor.
Conclusion: By using the technique described, a definitive regeneration of the alveolar bone can be accomplished.
Purpose: To demonstrate a new periodontal attachment procedure based on retardation of epithelial migration, FGG (since the epithelium desquamates and re-epitelization begins until 5-6 days).
Materials and methods:
Patients had initial prep and 88 intrabony defect treated, then re-evaluated at 3 and 6 months.
Surgical technique: initial incision 1 mm below the free gingival margin at an angle of about 25” to the tooth, internal bevel incision, split thickness flap except over defect, debrided and degranulated defect, SRP, cortical penetration, flap recontoured to receive FGG, cancellous osseous coagulum autograft into defect (loose), FGG from palate or edentulous area. Modification of this procedure also discussed.
Results:
Conventional flap technique had 60% of the treated sites had residual pockets, whereas the technique being tested had 10% residual pockets >3mm.
About 60% of the intrabony defects regenerated completely with new attachment, whereas with the conventional flap procedure only 40% of the defects showed new attachment.
BL: Using free soft tissue grafts to obtain new attachment showed very good results.
P: To study healing around various types of root surfaces when epithelium was excluded.
M&M: 8 Rhesus monkeys; 58 teeth; Periodontitis induced with ortho ligatures until 50% AL was achieved; Contralateral untreated control teeth were then treated with SC & OH with 0.2% CHX; Buccal FTF were raised; crowns resected at CEJ, roots SC; flap replaced to completely cover the resected root. CTRL received SC only. Lead acetate injected to label new bone formation. Histo specimens obtained 5 to 36 weeks after surgery & evaluated: l) New attachment, 2) Epithelium, 3) Root resorption, 4) CT, & 5) ankylosis.
R: Only 66% of teeth remained entirely covered. New attachment was seen mostly on the sides of the covered roots and ranged from 0 to 4.4 mm (quite variable). Exposed roots had epithelium extending down the sides of the root in most specimens. In specimens with a small perforation, the epithelium covered as little as 15% of the root surface. Cementogenesis was seen as early as 8 weeks in the resected teeth. New bone formation was seen at alveolar crest, ranged from 0 to 1.6 mm, and was often associated with ankylosis. Epithelial downgrowth was variable. Root resorption was common & limited epithelial downgrowth. CT attachment was mostly seen at the apical end of roots near the PDL, but some attachment was seen near the cut surfaces of teeth.
BL: Covering resected roots via flap replacement makes it possible to exclude epithelium from periodontal pockets. Authors proposed that new attachment appears to result from cells originating in the PDL, but that it can also arise from cells from the gingival CT.
Purpose: To discuss observations on periodontal repair in experimental animal models that may contribute to the understanding of the biologic basis for regenerative therapies.
Review:
Perspectives of periodontal repair: Healing of surgical wounds begin with chemoattraction of cells that accumulate and debride the wound and end with the formation and maturation of a new extracellular matrix. The matrix bridges the margins of the wound, supports cells and a regenerating vasculature and restores the resistance of the tissues to functional stress. Healing after periodontal surgery is more complicated since part of the flap opposes the avascular, calcifies and rigid tooth surface. Epithelium of the surgical flap must be prevented from early access to the root surface during the healing period to permit CT repair.
Current regenerative therapeutic procedures: Soft tissue management to prevent epithelial downgrowth in early regenerative attempts included repeated subgingival curettage. More recent approaches included surgical removal of the epithelium and root submerging. The use of a cell-occluding membrane can also be used for epithelium exclusion as well as other adjuncts to periodontal flap surgery such as detoxification by root planing of the root surface and root conditioning by topical application of acidic drugs. Suitable application of extracellular matrix proteins and growth factors may support periodontal regeneration. Bone grafts are also used to fill intrabony defects and furcation defects.
Early healing events: The sequence of healing is commonly divided into three overlapping phases 1) inflammation, 2) granulation tissue formation and 3) matrix formation and remodeling.
Periodontal wounds red blood cells interspersed in a granular precipitate of plasma proteins may be observed immediately following wound closure. A few hours later the intercellular matrix appears more organized with fibrin formation. Neutrophils are present and the inflammatory phase progresses and degradation of erythrocytes begins at one day. Granulation tissue is visualized within 3 days. Macrophages can be seen at the dentin surface and fibroblasts now occur in the wound space. Further degradation of the fibrin clot is evident. At 7 days the wound site is dominated by a cell-rich granulation tissue with fibroblasts and young collagen fibers. Within 14 days, the newly formed collagen fibers may show an arrangement indicative of physical attachment to the dentin. Cementum formation may be initiated. Studies in dogs have shown that the root surface-gingival flap interface reaches sufficient maturity to resist tensile strengths in 2 weeks. The biologic potential for complete CT repair exists, but several factors influence healing and explain the appearance of long junctional epithelium. These factors disrupt the healing during the first few days, perhaps the 1st week.
Significance of clot adhesion: The significance of clot adhesion for periodontal repair following flap surgery has been elucidated in studies where healing against dentin surfaces treated with heparin were followed for 7 days. Already on day 1 adherence of fibrin clot to dentin appeared to be compromised, although maturation of the clot progressed normally over the 7-day interval. After flap surgery, significantly reduced CT repair was observed on roots treated with heparin. The strength of clot adhesion becomes less critical if complete wound stability can be secured throughout the healing period. The improved results observed when barrier membranes are used can also be an effect of wound stabilization.
Root surface condition: It appears that successful biomodification of the root surface is critically dependent on the agent used. Citric acid or tetracycline show better results than fibronectin, heparin or stannous fluoride. Root surface demineralization seems to increase the tensile strength of the wound by providing stronger adhesion of the fibrin clot to the root surface.
Do local or systemic antibiotics influence the clinical and/or histologic results with GTR?
How does bacterial colonization on the membrane influence the outcome of GTR?
Purpose: To evaluate the effect of complete anti-infective therapy on the microflora and success of periodontal regeneration in mandibular class II furcation defects.
Materials and methods:
18 pts with bilateral mand molar class II furcation defects were recruited. PI, GI, PD and vertical probing attachment level (V-PAL)-v and subg plaque levels were measured baseline, 3,6,9,12 mos.
Open flap, SRP w/hand instruments and flame shaped diamond bur (no odontoplasty or osteoplasty).
Guided Tissue Regeneration (GTR) was performed (e-PTFE membranes); the area was irrigated with either tetracycline (100 mg/ml) or 0.9% saline. All pts got TTC 250 mg qid x 14 days and CHX.
Prophylaxis was performed every 2 weeks for 3 months and monthly thereafter for 1 year. Membranes retrieved 4-6 wks.
Results:
PD reduction (3.1 mm), PAL horizontal gain (2.3 mm), and V-PAL (1.2 mm) were SSD compared to baseline.
There was NSD in sites receiving tetracycline irrigation.
A strong positive correlation was found between initial PD and vertical & horizontal PAL gain.
Aa was detected in 5 sites and was associated with less favorable clinical results.
BL: Anti-infective therapy (both mechanical & chemical), and monitoring for Aa and/or other periodontal pathogens might be useful in GTR therapy. Sites still harboring Aa had less favorable clinical results
P: To assess if a 10-day course of amoxicillin/clavulanate potassium (ACP -Augmentin) enhanced the outcome of GTR after 1 year.
M&M: Group I: 8 pts. (12 sites) no ACP and Group II: 7 pts (12 sites) w/ ACP coverage (10 day). Class II mandibular molar furcations were treated w/ePTFE (membrane removed at 4 wks). 22/24 sites were re-entered and assessed.
R/D: Group given ABX had less inflammation post-surgery. Overall gain of 0.8mm clinical attachment was found. Hard tissue findings: wide variations existed among the defects, however NSSD found b/w groups. 0.4mm crestal loss and 0.3mm apical defect fill was observed. A decrease in defect volume of >30% was found in sites in both groups.
|
After 1 year |
Group 1 |
Group 2 |
|
Mean PD reduction |
2.0 +1.2mm |
1.8 +1.1mm |
|
Recession |
1.2 +1mm |
0.8 +.7mm |
BL: As previously reported, ACP coverage was effective in reducing post-op inflammation, however these effects are not associated w/better defect fill or CT attachment at 12 months.
P: To determine whether the use of adjunctive systemic Azithromycin (AZM) improved the outcomes of periodontal pocket reduction surgery for the treatment of moderate to severe chronic periodontitis in heavy smokers.
M&M: Double-masked, randomized, placebo-controlled clinical trial study was performed on 30 pts. All pts had generalized moderate to severe chronic periodontitis, smoked at least one pack/day, with ≥10 teeth, and at least two posterior teeth with PD ≥ 5 and BOP. All patients completed SRP within 90 days prior to inclusion in the study and demonstrated adequate OH (plaque score < 20%). Surgery (APF with osseous recontouring) perfomed by 2nd and 3rd year residents. Clinical parameters (PD, CAL, BOP) were taken at the day of surgery, 3 and 6 months after surgery. GI, PI, wound healing index and crevicular fluid were assessed at base line, 2 weeks, 1,2 and 3 months. Patients were randomly assigned to one of two groups.
Group 1: received active AZM, 1 tablet/day 500mg for three days.
Group 2: placebo containing inactive ingredients, 1 tablet/day for three days.
R: Surgical treatment (SS) improved PD, CAL, and BOP. Additional use of AZM did not enhance this improvement. The test group had SS better wound healing at 1 month and SS less GI at 2 weeks and SS reduction of red complex bacteria at 3 months.
BL: In heavy smokers adjunctive AZM did not enhance reduction of PD, CAL gain. However, AZM did help with a more rapid wound healing, and sustained reduction of periopathogenic bacteria.
P: To evaluate the effect on periodontal healing of a locally applied metronidazole gel in combination with GTR.
M&M: 12 patients with one pair of vertical periodontal defects of comparable size and configuration were evaluated. The test defects were treated by GTR using e-PTFE membranes in combination with local application of metronidazole gel (1g) in the root, over the membrane and once sutured, around the gingival margin.
R: During the first month of membrane implantation, no statistic significance between test and control surfaces were noted with respect to inflammation of the marginal gingiva. 6 months after removal of the membrane, the median gain in attachment level as a percentage of the initial defect depth was 92% for test defects and 50% for control defects. NSSD was found between test and control sites regarding plaque, BOP, reduction in PD, gain in bone height, or recession of the gingival margin.
C: Local application of metronidazole gel has a beneficial effect on healing of periodontal vertical defects treated by guided tissue regeneration.
Purpose: To study microbiota associated with furcation-involved teeth before & after treatment by GTR procedure with or without a non resorbable ePTFE membrane, and to evaluate the benefit of additional systemic antimicrobial therapy.
M&M: 10 patients (20 mandibular molar with class II furcation defects) were selcted. 5 defects were treated with membrane & the active drug, 5 were treated without membrane but with active drug, 5 were treated with membrane and placebo, & 5 were treated with neither membrane nor active drug. Single daily dose of 1000 mg ornidazole was administered for 10 consecutive days.
R: Considerable differences were found in the healing response of furcation defects with or without antimicrobial agent. More horizontal attachment gain & increase in bone density was obtained in patients receiving the active drug than the patients receiving placebo. With 1 exception, all sites with increase horizontal probing depth found in patients in the placebo group. Treatment with membrane + antibiotics results in 0.7 mm mean recession & 1.2 mm mean decrease in horizontal probing depth. Sites with membrane were more contaminated than non-membrane sites (especially A.a, F.n. & P.i.). GTR treated sites were often already positive upon removal of the membrane, re-emergence of target organisms seemed to be more delayed in the conventionally-treated sites. None of the drug treated sites were positive for A.a and only one for P.g., however, P.i. was still evident
Conclusion: Using antibiotics didn’t eliminate all bacteria, but the sites that were treated showed better result.
Purpose: To determine the microbial colonization of e-PTFE barrier membranes by putative pathogens at 3 minutes of intra-oral manipulation, and to compare the microbial and clinical features of mandibular posterior 2- to 3-wall defects treated with e-PTFE membranes in 20 patients with no PD 5mm and in 22 patients with multiple PD 5mm.
Materials and methods: 42 patients, no systemic disease, no smokers were included. 42 sites with a two- to three- wall interproximal intrabony defect in the mandibular posterior region Group A: 20 patients, received Phase I and Phase II prior to experiment except for the experimental areas, so they had no PD >5mm except for the study site and low levels of putative pathogens. Group B: 22 patients received maintenance only, multiple PD >5mm (8-44) and high levels of pathogens. Clinical measurements, PD, BOP, PI and membrane exposure (>2mm was recorded as positive) were taken at the initial visit, immediately prior to regenerative procedure and 6 weeks post-surgery. Membrane exposure was measured every week for 6 weeks. Prior to experiment OHI, SCRP, occlusal adjustment and carries control were done. Patients in group A had also received surgical therapy of deep periodontal pockets in the non-study sites. All patients received amoxicillin/clavulanate potassium, ibuprofen and CHX. Microbial examination was done prior to surgery, after 3 minutes of intra-oral membrane manipulation and at the time of membrane removal, 6 weeks post-surgery. Paper points were used and various species were studied (Aa, Pi, Pg, Tf, C. rectus, Fusobacterium species...). Statistical analysis was done.
Results: In Group A there was no contamination of the membrane at 3 minutes of intra-oral manipulation, whereas in group B 7/22 membranes got infected. Average defect size was comparable in both groups. CAL was ≥2mm in group A, 8 sites of group B showed 1mm of CAL gain and 3 no gain. Membranes remained covered for a 2.5 weeks average in group A and from 1.3-1.8 weeks in group B. Group B patient exhibited significantly higher levels of pathogens in every time interval. Membrane exposure, BOP, presence of Pg at the time of GTR and presence of putative perio-pathogens at baseline are correlated with less CAL gain.
Conclusion: GTR should be performed in patients with low levels of pathogens prior to the insertion of the membrane and at the site of regeneration during the healing period. OHI, SCRP, Phase II and specific antibacterial treatment, seem to constitute valuable treatment modalities in optimizing the potential healing.
Purpose: To evaluate bacterial colonization of the tooth-facing surface of bioabsorbable membranes and to determine its effect on the clinical outcome of membrane supported reconstructive surgery.
Materials and methods :
20 systemically healthy subjects with chronic adult periodontitis (12M, 8F, mean age 41 years).
One non-furcation tooth site per patient was associated with an angular bony defect and a PAL of > 5mm, was selected for GTR using a polyglicolactic membrane.
Patients prescribed Augmentin 1g/day for 14 days and 0.12% Chlorhexidine 2x/day. Recalled 1x/week for 5 weeks for prophylaxis.
Membranes were removed at sites with exposure at 5 weeks and were analyzed by SEM for bacterial colonization.
Sites with no exposure were allowed to heal without any surgical intervention. Prophylaxis and OHI 1x/month for the next 6 months. PAL were measured at the end of the 6 months.
Results:
5 weeks post-surgery 13/20 membranes (65%) were partially exposed supragingivally.
A gain of AL was statistically greater in sites with no membrane exposure when compared to sites with a partially exposed membrane (4.2 +/- .5mm vs. 3.3 +/- .6mm).
SEM showed bacterial colonization in all exposed areas of membranes.
In the midpart of exposed membranes, 41% demonstrated microbial colonization with no bacteria in the apical portion of the membrane.
Cocci and short rods were the predominant microorganisms found in the exposed areas of the membrane and more apically on the unexposed portion of the membrane filaments and long curved rods dominated.
Regression analysis indicated that gain in PAL was negatively correlated to microbial colonization of the midpart of the exposed membranes.
BL: Gain in AL was reduced in sites with partially exposed membranes when compared to sites with unexposed membranes. Systemic antibiotics and chlorhexidine did not prevent bacterial colonization. Midportion of the tooth-facing surface of polyglicolactic membrane is a critical area for the healing process since its bacterial colonization was detrimental to the outcome of the GTR surgery.
What are some of the biologic modulators you know of that are used in periodontal regeneration? Discuss their applications and success in periodontal regenerative therapy.
P: To determine if there was a proliferative effect of PDGF and TGF β1 alone or in combination on fibroblasts obtained from the periodontal tissue, and also to determine if the effect of growth factors was different on populations of fibroblasts derived from gingiva or from PDL.
M&M: Human gingival fibroblasts were obtained from biopsy sites of non-inflamed tissues and cultured. PDL fibroblasts were obtained from extracted for ortho reasons or from impacted 3rd molars. Subjects ranged from 15 37 years old. 3 samples were PDL cells and 3 samples were gingival fibroblasts. The cells were supplemented with 10 ng/ml TGF β1, 20 ng/ml PDGF, or both. Thymidine incorporation was measured after 24, 48, & 72 hours. Statistical evaluation using ANOVA and t-test were conducted.
R: A significant difference in proliferation was seen in PDL cells & gingival fibroblasts exposed to PDGF & TGF β1. TGF β1 favored proliferation of PDL cells over gingival fibroblasts at 48 & 72 hours. The combination of TGF β1 and PDGF showed the greatest degree of proliferation mainly on PDL cells. PDGF alone showed preferential proliferation of gingival fibroblasts at 72 hours.
BL: TGF β1 produced a mild increase in proliferation of PDL but was a poor stimulator of gingival fibroblasts, (previous studies have shown inhibitory effect on epithelial cells). PDGF's effect on PDL cells is enhanced by TGF β1. Recent advances in our understanding of cell regulation by growth factors present new options for the clinician and may provide additional treatment methods for regenerating lost periodontal support.
Purpose: To evaluate alveolar bone and cementum regeneration following periodontal reconstructive surgery using rhBMP-2 in beagle dogs.
Materials and methods: 6 dogs were used. Supra-alveolar periodontal defects were created in the mandibular right and left jaw quadrants. Bone was removed around the full circumference of 2nd, 3rd and 4th premolars and clinically the height from the CEJ to the reduced alveolar crest was 5mm. Crowns were reduced to 1mm above the CEJ. Defects in alternate quads were assigned to be treated with rhBMP-2 or control vehicle autologous blood and poly(D, L-lactide-co-glycolide)(PLGA) microparticles. Implants consisting of rhBMP-2 and vehicle were formulated and control defects received vehicle with buffer. Implants were molded around teeth and flaps were advanced to submerge the teeth. Antibiotics were administered twice daily for 2 weeks. The dogs were sacrificed 8 weeks post-op and tissue blocks were removed and prepared for histologic analysis. Defect height, bone regeneration, cementum regeneration, root resorption and ankylosis were recorded.
Results: 2 weeks post-op there was an obvious difference in tissue mass between jaw quadrants.
rhBMP-2 sites had increased 2-3 times the presurgical volume. Tissue was firm to palpation. At 8 weeks there was a decrease in tissue mass. One dog experienced exposure of a control tooth.
Radiographically test teeth exhibited increase radiopacity of the defects at 2, 4 and 8 weeks assuming the appearance of trabecular bone.
Histologically extensive bone regeneration in the test sites was observed. Frequently the bone was extending coronal to the CEJ covering completely the teeth. Periodontal space was observed between the instrumented roots and the bone. Newly formed cementum with fibrous attachment was present. Limited tooth resorption and ankylosis when present was limited immediately apical to the CEJ. Limited regeneration was observed in the control sites.
Conclusion: rhBMP-2 has significant potential for stimulating periodontal regeneration
.
Purpose: review that summarizes recent information on the characterization of extracellular matrices (ECM) and their cell interactions.
Discussion
Extracellular matrices: interactions between cells and ECM are important to their growth, morphology and function
Fibroblast ECM: Fibroblast usually exist in a fibrous matrix composed of collagen types I and III, a small chondroitin sulfate proteoglycan and fibronectin. Type I collagen high tensile strength.
Cartilage ECM: Chondrocytes exist in a homogeneous matrix containing type II collagen, chondroitin sulfate, and proteoglycan. Collagen fibers are small.
Epithelial cell ECM: Constitute the matrix of basement membrane. Contains type IV collagen, heparan sulfate, proteoglycan and the glycoprotein Laminin. Laminin is a major constituent of basement membrane constituting 30-50% of the total protein. Laminin is localized exclusively in the basement membrane and is synthesized by the cells that normally reside on the basement membrane.
Cell specificity as modulated by ECM: Fibroblast, chondrocytes and epithelial cells produce and use different attachment factors.
Polypeptide growth factors : they are another class of biological response modifiers. They are hormone like in both structure and function.
Regeneration of the Connective tissue attachment of the periodontium
Citric acid conditioning or insertion of synthetic membranes, allows for selective cell recolonization of the tooth surface by cells of mesenchymal origin. In vitro partial surface demineralization of the root surface dentin enhances migration to and attachment of fibroblast like cells from the periodontal ligament. The gain in clinical attachment following partial surface demineralization with citric acid in conjunction with periodontal surgery in man is limited, approximately 2mm gain of probing attachment in acid treated vs 1.2-1.5mm on non treated.
It has been proposed that a prerequisite for successful healing following periodontal regeneration procedures is that cells from the PDL are allowed to selectively colonize the instrumented root surface rather than gingival epithelial cells, gingival fibroblast and osteoblast. The insertion of semi porous membranes under the soft tissue flap excludes epithelial cell apical migration and recolonization of the root by surface gingival fibroblast.
ECM and polypeptide growth factors: The attachment of fibroblast was enhanced by fibronectin whereas Laminin enhanced the attachment of epithelial cells.
It is possible that the attachment of connective tissue could be promoted by the local application of exogenous extracellular matrix material and appropriate PGFs to properly prepared root surfaces, which would confer a selective advantage to gingival fibroblast, osteoblast and/or cell originating from the PDL.
Tetracycline root conditioning selectively removes the surface smear layer, it may also act favorably by inhibition of collagenase activity and bone resorption and by its local antimicrobial effects to support these events.
P: To analyze all available biological data of enamel matrix proteins (EMPs) at the cellular and molecular levels that are relevant in the context of periodontal wound healing and tissue formation.
M: Medline literature search was performed using key words “enamel matrix proteins” or “enamel matrix derivative” or “emdogain” and “amelogenin.” 6 articles were included out of 127 that matched the criteria.
D: Traditionally EMPs are associated with amelogenesis. Ameloblasts synthesize and secrete a number of EMPs, including amelogenins, ameloblastin, amelotin, tuftelin, and enamelin. Amelogenins self-aggregate into supramolecular aggregates, so-called nanospheres, and play a crucial role in regulating the initiation and growth of hydroxyapatite crystals during the formation of enamel. EMPs are also considered to be involved in cell differentiation processes occurring during epithelial-mesynchymal interactions of crown development. EMPs have been linked to playing a role in differentiation of progenitor cells into cementoblasts- that specifically produce acellular extrinsic fibre cementum.
1) Cell attachment, spreading and chemotaxis:
EMPs increase cell attachment of epithelial cells, gingival fibroblasts and PDL fibroblasts. Inconsistent observations were made regarding the difference in rate and extent of cell attachment between gingival and PDL fibroblasts. EMD has also a chemotactic effect on endothelial cells.
2) Cell proliferation and survival:
EMPs favor cell proliferation of PDL fibroblasts over gingival fibroblasts and over epithelial cells. Epithelial cells respond less to EMPs by cell proliferation. The effects of EMPs on epithelial cells seem to be cytostatic, not cytotoxic. EMPs stimulate the outgrowth of new blood vessels and increase the number of endothelial cells. EMD and in particular, its vehicle, PGA have antibacterial properties.
3) Expression of transcription factors:
EMPs increase the expression of transcription factors that are related to chondroblast and osteoblast/cementoblast differentiation.
4) Expression of growth factors:
EMPs cause stimulation of total protein synthesis and synthesis of specific extracellular matrix molecules (glycoproteins and proteoglycans). They also down-regulate the expression of genes involved in early inflammatory events of wound healing and up-regulate the expression of genes encoding growth and repair promoting molecules. Among the up-regulated molecules are TGF-B1, BMP-2, BMP-7, PDGF-AB, VEGF, CTGF, FGF-2, IGF-1, TNF-a, IL-6, IL-8, PGE2, OPN, collagen types II and X, MMP-2, and ALP.
5) Expression of molecules involved in regulation of bone remodeling
Normal bone remodeling depends on balance between bone formation and bone resorption. (RANK binds to RANKL, which induces osteoclastic activity, OPG is a decoy that competes with RANKL for its binding- thus OPG is a natural inhibitor of osteoclast differentiation and activation). EMPs influence this by modulation the expression of OPG and RANKL. Studies suggest that EMPs modulate the RANK-RANKL-OPG system most likely towards bone apposition. In addition, some growth factors and cytokines that are up-regulated by EMPs directly up-regulate OPG and down-regulate RANKL production.
Carlson 2002 ARTICLE comparisons and reviews
Platelet-rich plasma (PRP). Clinical applications in dentistry. (Review)
Surgical sites enhanced with PRP have been shown to heal at rates 2-3x that of normal surgical sites. PRP can be a great adjunct to many periodontal and oral surgical procedures such as bone grafts, implants and maxillofacial reconstruction
Growth Factors:
Mechanism of hemostasis and Wound healing
Vessel injury/exposure of subendothelial tissue to blood platelets stick to exposed collagen proteins release adenosine diphosphate, serotonin and thromboxane hemostasis (platelet plug) activation of growth factor involved in initiating and sustaining wound repair.
PDGF (platelet-derived growth factor) – Accelerates early would closure
Is Chemotactic for PMNs, macrophages, fibroblasts and smooth muscle cells
Stimulates cell replication of important stem cells for fibroblasts and endothelial cells
Simulates the production of fibronectin and hyaluronic acid and helps bring about wound contraction and remodeling
TGF-B (transforming growth factor –B)
Stimulates fibroblast chemotaxis and the production of collagen and fribronectin by cells.
It has been shown that the topical application of these growth factors to healing sites can accelerate repair and wound maturation.
Platelet-Rich Plasma (PRP)
Once PRP are activated by the addition of thrombin, begin to release the growth factors PDGF and TGF-B.
PRP can serve both in hemostasis and adhesion of graft materials.
Marx and Carlson et al. 1998, a study showed increase bone density for PRP-enhanced grafts compared with control bone grafts without PRP. They concluded that addition PRP to bone grafts accelerates the rate of bone formation and the degree of bone formation in bone grafts at least during the first 6 months.
Cho and colleagues found that PDGF was the only growth factor that effectively stimulated periodontal ligament fibroblast migration and proliferation without the added risk of the patient experiencing ankylosis of the teeth. When used in clinical trials on beagles, PDGF-modulated guided tissue regeneration (GTR), therapy was shown to effectively aid in the regeneration of periodontal furcation defects.
Park and colleagues conducted similar studies on beagles, comparing treatment of Class III furcation defects with PDGF and GTR vs. with GTR alone. The study indicated a statistically greater amount of bone and periodontal ligament in sites treated with PDGF and GTR together than in sites treated with GTR alone.
P: To present data documenting that PRP increases platelet concentration when placed into grafts.
M & M: 88 cancellous cellular marrow bone graft reconstructions of mandibular defects arising from benign or malignant tumors (no radiotherapy). One group received grafts without PRP and the second group with PRP. Samples of PRP and venous bood submitted for platelets counts. PRP monoclonal antibody, and bone graft harvest material monoclonal antibody study were studied and assessment of radiographic graft maturity was performed at 2,4, and 6 month intervals. At least one implant was placed in each site at 6 months and a core of bone specimen was for histomorphometry and antibody testing.
R:
Pt mean platelet value was 232,000 (111,000-523,000). PRP mean platelet count was 785,000 (338% more concentration 595,000-1,100,000).
After centrifugation the platelets sequestered showed and intense uptake of both PDGF and TGF-β (grown factors).
Bone graft harvest material tested positive for receptors to PDGF and TGF-β, meaning capable to response.
Radiographic graft maturity: Grafts with PRP were assessed more than twice their actual maturity, with ratios 2.16 at 2 months, 1.88 at 4 months and 1.62 at 6 months.
6 months histomorphometry: native mandible had a trabecular bone area of 38.9% compared to 55.1% for grafts without PRP and 74% for grafts with PRP.
BL: PRP addition accelerates the rate and degree of bone formation, through at least the first 6 months.
P: To discuss the biological mediators for periodontal regeneration
D: Growth factors: proteins that may act locally or systematically to affect the growth and function of cells either in an autocrine fashion (cells that produce them are also affected) or paracrine fashion (affects different cells).
Platelet-derived growth factor (PDGF): The primary effect of platelet-derived growth factor is that of a mitogen, initiating cell division.
Insulin growth factor: They are mitogens, and in fibroblastic systems appear to be progression factors. In bone cell systems, insulin growth factors stimulate both proliferation of pre-osteoblasts as well as the differentiation of osteoblasts, including type I collagen synthesis. Thus, insulin growth factor increases both the number of cells synthesizing bone and the amount of extracellular matrix deposited by each cell.
Bone morphogenetic protein (BMP): proteins that constitute a large family of regulatory factors. While they are mitogenic on some cell types such as rat calvarially derived cells, their primary activity appears to be one of differentiation.
Transforming growth factor-β: multifunctional growth factor structurally related to BMPs, but functionally different. Increases matrix production and leads to an increase in fibrosis.
Fibroblast growth factor: general growth-promoting effects on most fibroblastic cell types and also stimulates angiogenesis, wound healing, and cell migration. It can stimulate endothelial cell and periodontal ligament cell migration and proliferation. It also stimulates bone cell replication, but under some conditions can inhibit matrix synthesis by bone cells though more studies required.
Extracellular matrix proteins and attachment factors: control where cells migrate, how they adhere, and how they function
Amelogenins: regulate the initiation and growth of hydroxyapatite crystals during mineralization of the enamel and direct formation of cementum.
Fibronectin: aids in the attachment of cells to the extracellular matrix and plays a pivotal role in tissue regeneration and wound healing.
Mediators of bone metabolism:
Prostaglandins: mitogenic for osteoblasts and stimulate differentiation, increase periosteal and endosteal bone formation.
Glucocorticoids: chronic use known to result in bone loss, generally though can enhance differentiation of osteoblastic precursor cells.
BL: Formation of tissues proceeds in a deliberate and orderly sequence and can be stimulated at different points. Mitogenic signals and differentiation factors can be used to stimulate tissue formation. Receptor mediated peptides or extracellular matrix molecules for soft and hard tissues appear to allow stimulation of soft tissue formation cascades. More studies are needed to determine the future therapeutic potential for growth factors so that they may be used to optimally stimulate and direct specific points along tissue formation cascades.
Platelet-rich plasma (PRP) is an autologous concentration of human platelets in a small volume of plasma. The term PRP is preferred to autologous platelet gel, plasma-rich growth factors (PRGFs) or a mere autologous platelet concentrate.
It is a concentration of platelets and of the 7 fundamental protein growth factors proved to be actively secreted by platelets to initiate all wound healing. These growth factors include the 3 isomeres of platelet-derived growth factor (PDGF, PDGF and PDGF), 2 of the numerous transforming growth factors – (TGF1 and TGF2), vascular endothelial growth factor and epithelial growth factor. PRP also contains 3 proteins known to act as cell adhesion molecules for osteoconduction and as a matrix for bone, connective tissue and epithelial migration. These cell adhesion molecules area : fibrin, fibronectin and vitronectin.
PRP development via centrifugation has been greatly simplified so that it can be used in the office setting as well as the operating room. The centrifugation process should be sterile and precisely suited to platelet separation from red blood cells and their sequestration in high concentrations without lysing the platelets or damaging them so that they no longer can actively secrete their growth factors.
Animal studies: blood volume too small to produce PRP. So, these studies use donor blood that is homologous but not autologous and therefore is not true PRP. The use of donor animal blood platelets imparts an immune reaction and leads to false negative results.
At the time of this writing only two devices used to develop PRP have been cleared by FDA.
Smart PReP, Harvest Technologies
Platelet concentration collection system, 3i implant innovations
Studies suggesting that there is no benefit from PRP can often be traced to poor quality PRP produced by inadequate devices.
How does PRP work?
PRP works via the degranulation of the a granules in platelets, which contain the synthetized and prepackaged growth factors. The active secretion of these growth factors is initiated by the clotting process and begins within 10 min after clotting. More than 95% of the presynthetized growth factors are secreted within 1 hour. PRP should be used on the graft, flap or wound within 10min of clot initiation. The secreted growth factors immediately bind to the external surface of cell membranes of cells in the graft, flap or wound via transmembrane receptors. Mesenchymal stem cells, osteoblasts, fibroblasts, endothelial cells and epidermal cells express the cell membrane receptors to growth factors in PRP. These receptors induce activation of an endogenous internal signal protein, which causes the expression of (unlocks) a normal gene sequence of the cell such as cellular proliferation, matrix formation, osteoid production, collagen synthesis, etc. The importance of this knowledge is that the PRP growth factors never enter the cell or its nucleus, they are not mutagenic, and they act through the stimulation of normal healing, just much faster. Therefore, PRP has no ability to induce tumor formation and has never done so.
After the initial burst of PRP-related growth factors, the platelets synthesize and secrete additional growth factors for the remaining 7 days of their life span. Once the platelet is exhausted and dies off, the macrophage, which has arrived in the region via the vascular in-growth stimulated by the platelets, assumes the function of wound healing regulation by secreting some of the same growth factors as well as others. Therefore, the number of platelets in the blood clot within the graft, wound, or adherent to a flap sets the rate of wound healing. PRP merely increases this number.
How many platelets are enough?
Dose-response relationship. The greater the number of platelets that greater the cell proliferation and differentiation. Because most individuals have a baseline blood platelet count of 200,000 75,000/L, a PRP platelet count of 1 million/L as measured in the standard 6-mL aliquot has become the benchmark for “therapeutic PRP.”
Does PRP really work?
There are studies to support both sides. Review the level of science each publication represents, assessing the quality of PRP used in each study and the controls used. Articles supporting little benefit from PRP often do not use real PRP, use damaged platelets, may have not activated the platelets or have statistically insufficient data to draw a valid conclusion.
What clinical situations benefit from PRP?
Because PRP enhances osteoprogenitor cells in the host bone and bone grafts, it has found clinical applications in periodontal/periimplant defects, sinus grafting procedures, ridge augmentation and preservation procedures. Because it enhances soft tissue healing, it is used in gingival grafts, root coverage procedures.
PRP is an autogenous preparation, no risk for disease transmission. Some suggest that PRP can promote infections due to the fact that it is blood clot and than blood agar is used in microbiology to culture bacteria. PRP is not different is substrate than the blood clot that forms in every wound and therefore could not support bacterial growth any more than any other blood clot.
Some have implied that the value of PRP is related to soft tissue healing enhancement because platelets do not contain BMP. However, all bone graft healing and osteoconduction into bony defects and around the numerous bone substitutes used today arise from adult mesenchymal stem cells and their lineage, leading to osteoblasts, all of which have already been proved to respond to PRP with accelerated bone formation.
The value of PRP is its proven effectiveness, its safety, its cost effective- ness, and its availability in an easy-to-develop manner and its FDA approval if developed by an FDA-cleared device.
Purpose: Review of how tissue engineering has advanced and its impact on the clinical management of periodontal, maxillofacial and osseous defects in preparation for implant placement.
Discussion: Tissue engineering: wound healing process manipulated so that tissue regeneration occurs usually involving: the signaling molecules, scaffold or supporting matrices, and cells.
Examples of two clinically applicable, commercially available tissue engineering systems that involve the use of platelet-derived growth factor-BB tricalcium phosphate (GEM 21) and bone morphogenetic protein type I collagen sponge (INFUSE).
Platelet-rich plasma:
Autologous blood drawn and separated into three fractions: platelet-poor plasma (fibrin glue or adhesive); platelet- rich plasma; and red blood cells. Platelets enriched by 338% in the platelet-rich plasma preparation, and increased concentrations of platelet-derived growth factor (41.1 ng/ml) and transforming growth factor-beta1 (45.9 ng/ml) in platelet-rich plasma have been reported.
Monoclonal antibodies have identified the presence of platelet-derived growth factor, insulin-like growth factor and transforming growth factor-beta in the cytoplasmic granules of platelets. Analysis of platelet-rich plasma indicated the additional presence of basic fibroblast growth factor-2, epidermal growth factor, and vascular endothelial growth factor mixture of growth factors in platelet rich plasma putatively stimulates the proliferation of fibroblasts and periodontal ligament cells, extracellular matrix formation and neovascularization.
Platelet-rich plasma may suppress cytokine release and limit inflammation, thereby promoting tissue regeneration. Platelet-rich plasma also contains a high concentration of fibrinogen.
In clinical use, calcium and thrombin are added to the platelet-rich plasma preparation to activate the proteolytic cleavage of fibrinogen into fibrin. Fibrin formation initiates clot formation, which in turn initiates wound healing.
Enamel matrix derivative
Harvested from developing porcine teeth has recently been reported to induce periodontal regeneration.
Contains a mixture of low-molecular weight proteins that stimulate cell growth and the differentiation of mesenchymal cells, including osteoblasts.
Contain transforming growth factor-beta and to stimulate bone morphogenetic protein, transforming growth factor-beta and connective tissue growth factor expression in osteoblastic cells.
Connective tissue growth factor is a downstream mediator of transforming growth factor-beta and promotes osteoblast proliferation and development.
Stimulates angiogenesis directly by stimulating endothelial cell proliferation and chemotaxis, and stimulates vascular endothelial cell growth factor production by periodontal ligament cells.
When applied to root surfaces, the proteins are absorbed into the hydroxyapatite and collagen fibers of the root surface, where they induce cementum formation followed by periodontal regeneration.
Growth Factors
Growth factors are naturally occurring proteins that regulate various aspects of cell growth and development.
During wound healing, growth factors modulate cell proliferation, migration, extracellular matrix formation and other cellular functions. Some may also function as cell differentiation factors.
Platelet-derived growth factor and insulin-like growth factor-1 were topically applied to periodontally diseased root surfaces in beagle dogs Substantial amounts of new bone, cementum and periodontal ligament were present after 2 weeks. Results of this study were confirmed in three other studies utilizing beagles and experimentally induced periodontitis in nonhuman primates.
Fibroblast growth factor-2 is one of the most potent mitogens for cells of mesodermal and neuroectodermal origin and induces angiogenesis, and is involved in regulating the proliferation
and differentiation of fibroblasts, vascular endothelial cells, vascular smooth muscle cells, neuroectodermal, osteoblast, cartilage, epidermal and periodontal ligament cells.
Fibroblast growth factor-2 plays important roles during the processes of tissue regeneration and wound healing; promotes mesenchymal cell proliferation.
The unique advantage of recombinant human platelet-derived growth factor, tricalcium phosphate
and recombinant human basic fibroblast growth factor is consistency in their regenerative capacity.
Unlike grafting materials and enamel matrix derivative, there is no variability in purification or
processing. Variations in the regenerative/healing response are caused by individual healing capability and surgical techniques.
Bone morphogenic proteins
Group of regulatory glycoproteins that are members of the transforming growth factor-beta superfamily.
Primarily stimulate differentiation of mesenchymal stem cells into chondroblasts and osteoblasts.
At least seven bone morphogenetic proteins have been isolated from bovine and human sources.
Research has focused on bone morphogenetic protein-2 (OP-2), bone morphogenetic protein-3 (osteogenin) and bone morphogenetic protein-7 (OP-1).
The osteoinductive effect of bone morphogenetic proteins has been characterized using crude protein preparations derived from decalcified bone. When these crude preparations were placed in muscle or subdermal pouches, ectopic focal formation of cartilage was present after 12 days and bone was present after 28 days.
Crude preparations of bone morphogenetic protein-2 and bone morphogenetic protein-3 applied in surgically induced furcation defects appeared to stimulate periodontal regeneration.
Studies using recombinant human bone morphogenetic proteins to determine their potential for correcting intrabony, supra-alveolar, furcation and fenestration defects gains in bone
and cementum were 3.5 mm and 1.6 mm, respectively, compared with 0.8 mm and 0.4 mm for controls.
Histologic analysis revealed periodontal regeneration with areas of ankylosis. Contrary to these findings, bone morphogenetic protein-7 augmentation resulted in a significant increase in periodontal regeneration without any ankyloses
BL: A variety of new regenerative strategies utilizing tissue-engineering principles are now available. Despite certain limitations, we continue to improve our understanding of the physical and biologic requirements necessary for specific tissue regeneration. Helps to improve manipulation of the various elements of tissue engineering (signaling molecules, scaffold and cells) to generate specific regenerative responses.
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