Implants- Biological Principles: Osseointegration and bone interface

 

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References:

Book Chapters

  • Giannobile, et al. Bone as a Tissue (CH 4). Clinical Periodontology and Implant Dentistry, Lindhe, J.; Lang, K. 5th Edition, 2008, Blackwell Munksgaard (Volume 1).
  • Lindhe, Berglundh, Lang. Osseointegration (CH 5). Clinical Periodontology and Implant Dentistry, Lindhe, J.; Lang, K. 5th Edition, 2008, Blackwell Munksgaard (Volume 1).

Journals

Osseointegration

  1. Albrektsson, T et al: Biological aspects of implant dentistry: Osseointegration. Periodontology 2000 4:58-73, 1994
  2. Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of edentulous jaws. Int J Oral Surg 1981;10:387-416.
  3. Charatchaiwanna A, et al. Mathematical equations for dental implant stability patterns during the osseointegration period, based on resonance frequency analysis studies. Clin Implants Dent Relat Res. 2019 Aug 1 epub ahead of print.
  4. Smeets et al. Impact of Dental Implant Surface Modification on Osseointegration. Biomed Res Int. 2016;20166285620
  5. Rittel D, Dorgoy, A, Shemtov-Yona, K. Modeling the effect of osseointegration on dental implant pullout and torque removal tests. Clin Implant Dent Relat Res. 2018 Oct;20(5):683-691. doi: 10.1111/cid.12645. Epub 2018 Jul 27.

Bone-implant interface (Placement and Initial Healing)

  1. Marão HF et al. Cortical and Trabecular Bone Healing Patterns and Quantification for Three Different Dental Implant Systems. Int J Oral Maxillofac Implants. 2017 May/June;32(3):585-92.
  2. Mathieu V, Vayron R, et al. Biomechanical determinants of the stability of dental implants: Influence of the bone-implant interface properties. J Biomech. 2014 Jan 3;47(1):3-13. doi: 10.1016/j.jbiomech.2013.09.021. Epub 2013 Oct 10.
  3. Trisi, P., Rebaudi A: Progressive bone adaptaion of titanium implants during and after orthodontic load in humans. Int J Periodontics Restorative Dent. 2002 Feb; 22(1):31-43
  4. Tretto PHW et al. Does the instrument used for the implants site preparation influence the bone-implant interface? A systematic review of clinical and animal studies. Int J Oral Maxillofac Surg. 2018 Apr 24 (epub ahead of print)
  5. Trisi P, Berardini M, Falco A, Podaliri Vulpiani M. Validation of value of actual micromotion as a direct measure of implant micromobility after healing (secondary implant stability). An in vivo histologic and biomechanical study. Clin Oral Implants Res. 2016 Jan 4.
  6. Salvi et al. Temporal sequence of hard and soft tissue healing around titanium dental implants. Periodontol 2000. 2015. June;68(1):135-52
  7. Abrahamsson I, Berglundh, T, et al. Early bone formation adjacent to rough and turned endosseous implant surfaces. An experimental study in the dog Clinical Oral Implants Research, 15 (2004), pp. 381–392
  8. Berglundh T, Abrahamsson I, et al. Bone healing at implants with a fluoride-modified surface: an experimental study in dogs. Clinical Oral Implants Research, 18 (2007), pp. 147–152

Bone-implant interface (Function or Failure)

  1. Greenstein G, Cavallaro J, Tarnow D. Assessing bone’s adaptive capacity around dental implants: a literature review. J Am Dent Assoc. 2013 Apr;144(4):362-8.
  2. Mangano C, Piattelli A, et al. Evaluation of peri-implant bone response in implants retrieved for fracture after more than 20 years of loading. A case series. J Oral Implantol. 2013 Aug 21. [Epub ahead of print]
  3. Huang HL et al. Initial stability and bone strain evaluation of the immediately loaded dental implant: an in vitro model study. Clin Oral Implants Res 2011 Jul;22(7):691-8.
  4. Barewal R et al: Resonance Frequence Measurment on Implant Stability in Vivo on Implants with a Sandblasted and Acid – Etched Surface. Int J Oral Maxillofac Implants 2003; 18:641-651
  5. Alsaadi, G et al: A Biomechanical assessment of the relation between the oral implant stability at insertion and subjective bone quality assessment . J Clin Periodontol 2007; 34:359-366

Abstracts

Osseointegration

Topic:microscopic evaluation of osseointegration
Authors:Albrektsson T, Johansson C, Sennerby L

Title:Biological aspects of implant dentistry: Osseointegration.

Source:Periodontology 2000 4:58-73, 1994

Type:Discussion/Review

Keywords:osseointegration

Purpose: To analyze current knowledge on osseointegration.

Discussion:

Radiographic evaluation:

Due to the surrounding bone tissue, an implant may seem to be in direct bone contact even though there is obvious soft tissue coat in reality. The maximal resolution level of radiography, under ideal conditions, is 0.1 mm, which is 10 times the size of a soft tissue cell.

Light microscopic investigations of bone-to-implant interface:

The use of modern cutting and grinding techniques has clearly demonstrated that direct bone-to-implant contact at the light microscopic resolution level is possible with many different metallic and ceramic materials. In loaded clinical cases there are indications that what is referred to as osseointegration depends on material used as one of several factors being important for implant take.

Ultrastructural investigation of experimental implants:

Ultrastructural analysis of the implant-bone interface is technically very difficult, since ultrathin sections are needed for transmission electron microscopy. Most ultrastructural investigations have been performed in animals using metal-coated polycarbonate implants, which permits sectioning, or metal plugs from which the tissue has been separated before sectioning.

Comments on published ultrastructural investigations:

The in vivo interface scenario seems to be completely different from that observed in vitro. In vitro the only cells in direct contact with the implant surface were red blood cells and macrophages, during the early healing phase, and later, multinuclear giant cells. The inner most interface was the last area to be mineralized, and this process seemed to be acellular. The amorphous layer, and in some instance the electron-dense layer, cold be distinguished before extracellular matrix became mineralized.

The commercially pure titanium bone interface in relation to other interfaces:

The interface descriptions found in the literature point to a variability of the interface morphology both for bone-bonding (hydroxyapatite or bioglass) and non-bone-bonding materials (titanium), which is why this type of classification cold be criticized.

The ultrastructure of the bone-titanium interface:

There is one type of amorphous layer in the bone-to-metal interface, even if the width and the content (mineral, collagen, and proteoglycans) has been debated.

Evaluation of retrieved oral implants removed despite a remaining anchorage:

In general, a nonmineralized amorphous layer 200-400 nm wide was bordering the mineralized bone with an electron-dense lamina limitans-like line (50 nm thick). Areas with nonmineralized tissue containing collagen and sometimes osteocytes or vessels were present along the interface.

Conclusion: The only acceptable mode of defining osseointegration is based on clinical examination finding stable implants: a process in which clinically asymptomatic rigid fixation of alloplastic materials is achieved and maintained in bone during functional loading.

Topic: Osseointegration

Author: Adell R, Lekholm U, Rockler B, Brånemark PI

Title: A I5-year study of osseointegrated implants in the treatment of the edentulous jaw

Source: Int J Oral Surg 1981;10:387-416.

Introduction: Installation of pure titanium implants results in a firm, intimate and lasting connection between the implant and the vital host bone, which remodels in accordance with the masticatory load applied.

Objective: The purpose of the present paper is to give a summarizing review of material, methods and results from 15 years (1965 to 1980) clinical use of osseointegrated fixtures in the treatment of the edentulous jaw

Materials:

The evolution of the clinical procedures was divided into three time periods:

  1. Initial period (July 1965- March 1968)
  2. Development period (April 1968-June 1971), during which certain modifications of the method were introduced.
  3. Routine period (July 1971-September 1980), when only minor technical adjustments were accomplished.

The reviewed material in this study is presented as follows.

Development group, consisting of both the initial and development periods together, with an observation time of 10-15 years.

Routine group I, consisting of the routine period with an observation time of 5-9 years.

Routine group II, consisting of the routine period with an observation time of 1-4 years.

A preoperative denture period of at least one year was required for the majority of the patients in order to evaluate the rehabilitation effects of treatment with optimally adjusted removable dentures and to provide sufficient time for bone healing after tooth extraction.

Treatment procedure:

6 fixture sites (implants) were generally prepared in the region between the mental foramina or in the upper jaw between the anterior walls of the maxillary sinuses. No direct fixture loading was allowed, the healing time was 3-4 months in the lower and 5-6 months in the upper jaw before the loading.

After the healing period, the cover screws were removed and abutments attached to the implants. The prosthetic treatment started about 2 weeks following the abutment operation.

A precise fit between a gold framework and the abutments was the aim. The bridges were extended to include a maximum of 2 teeth distally to the most posterior fixtures in the lower and only 1 tooth in the upper jaws. All bridges were facultatively removable.

Results:

2768 fixtures were installed in 410 edentulous jaws of 371 consecutive patients

Anchorage function-  The anchorage function, defined as the ratio between the number of stable, osseo-integrated fixtures supporting a bridge, in relation to the total number of installed fixtures showed better results in Routine group II than I.

Marginal bone height- The marginal bone height depends on both proper marginal stress distribution and on adequate function of the marginal soft tissue. The results of the roentgenological examination of the changes in marginal bone height show almost equal amount in all the 3 groups and was about 1.2mm.

Marginal soft tissues- The marginal peri-abutment tissues were generally found to be clinically healthy, even when the peri-abutment mucosa was movable.

Complications- Loss of anchorage function; Fixture anchorage was lost basically because of different types of tissue reactions. Osseointegration might not have been achieved due to surgical trauma or because of perforation through the covering mucoperiosteum during healing.

Gingival complications- Three types of gingival complication occurred, namely early perforation, proliferative gingivitis and fistulae.

Discussion:

In routine group I (5-9 years) persisting fixture anchorage of 81% for upper and 91% for lower jaws was obtained. The results from routine group II (1-4 years) indicate that even better results can be expected in the future.

The marginal bone loss could be attributed to several factors:

  1. Effects of surgical trauma
  2. Inadvertent stress distribution to the marginal bone by forced tightening of the fixtures at installation
  3. Physiological resorption of the edentulous jaw
  4. Gingivitis

The total marginal bone loss from the beginning of the healing period to the end of the remodeling period was, however, almost equal in all the 3 groups and was about 1.2 mm

Conclusion– The mean bone loss was 1.5 mm during the healing period and the first year after abutment connection. Thereafter only 0.1 mm of marginal bone was lost annually in the group observed for 5-9 years. In the routine case the fixtures and their abutments are surrounded by hard and soft tissues which have remained healthy for follow-up periods of up to 15 years.

Osseointegration can only be achieved and maintained by a gentle surgical installation technique, a long healing time and a proper stress distribution when in function.

 

Topic: Dental implant stability and osseointegration.

Author: Charatchaiwanna, Attakorn, et al.

Title: Mathematical equations for dental implant stability patterns during the osseointegration period, based on previous resonance frequency analysis studies.

Source: Clin Implant Dent Relat Res. 2019;1–13. Wiley Periodicals, Inc

DOI: 10.1111/cid.12828.

Type: prospective clinical trial.

Keywords: dental implant stability, mathematical equation, resonance frequency analysis.

Purpose: to formulate mathematical equations for dental implant stability patterns during the osseointegration period, based on previous resonance frequency analysis studies.

Methods: online search of the literature between January 1996 to December 2017 was performed using MEDLINE.

-Inclusion criteria

  1. Studies published in English.
  2. Prospective clinical trials – Human participants older than 18 years with no systemic disease or contributing factors that affect osseointegration of dental implants.
  3. Treatment using root-form implants.
  4. Osstell magnetic device used to measure implant stability (measured in terms of ISQ 1-100 using magnetic frequencies by connecting the implant to Smartpeg).
  5. Implant stability measured: – At time of implant placement – At least four times in the first 6 weeks – At least two times between the 7th and 13th weeks.
  6. Mean ISQ value and standard deviation shown at all measured times.
  7. Complete paper accessible.

-Exclusion critetia

  1. Non-English language publications.
  2. Non-experimental studies (systematic reviews, literature reviews, and meta-analyses).
  3. Case reports and In vitro studies.
  4. Animal studies.
  5. Treatment using non-root-form implant (orthodontic mini-screws, palatal implants, etc.)
  6. Insufficient points of implant stability.

A mathematical function was used to determine implant stability. This function derives from 2 curves, which are the curve of primary and secondary stability and from parameters derived from time and flexibility.

Results:The initial search yielded 533 publications found in PubMed/Medline. 27 publications were considered for full-text analysis. Finally, nine studies were included in the mathematical analysis

Based on the ISQ scale, 3 groups were determined.

Group H with high stability more thand 70 ISQ.

Group M with moderate stability 60 to 69 ISQ.

Group L with low stability less than 60

Group H and some units of group M showed a rapid drop in primary stability in the first 6 weeks after the surgery with an exponential increase in secondary stability. While Group L and some units of group M showed a stable primary stability with a slow increase in the secondary stability.

Discussion: A mathematical way could be used to predict implant osseointegration after collecting their stability with a resonance frequency analysis system. However more researches should be done in order to have more data about it and determine the level of successful in treatment using this methods.

 

Topic: Osseointegration

Author: Smeets, Ralf, et al

Title: Impact of Dental Implant Surface Modifications on Osseointegration

Source: BioMed Research International 2016

DOI: 10.1155/2016/6285620

Type: Review article

Keywords: Dental implants, osseointegration, surface treatment, bone formation.

Purpose: To evaluate the effect of different surface treatments on osseointegration. Surface treatments evaluated included both commercially available and proposed treatments.

Methods: No methods mentioned.

Results:

  • Osseointegration and success of dental implants are highly affected by surface modifications (Macro, Micro and Nano surface modifications).
  • Macro surface implant modifications are determined by its visible geometry including threads, vent holes and tapered design.
  • Several micro surface implant modifications were introduced to induce increased bone formation surrounding dental implants and help shorten implant healing time or even allow immediate loading in certain situations.
  • Different methods of surface treatments were introduced and are currently available including:

Sandblasted and Acid-Etched Implants (Straumann).

Grit-Blasted, Acid-Etched, and Neutralized Implants (Ankylos, Xive and Frialit by Dentsply).

  • Other Implant systems proposed Nano surface modifications for dental implants to induce better and faster bone formation around implants including:
  1. Discrete Crystalline Deposition (NanoTite and T3 by Biomet 3i)
  2. Laser Ablation (Laser-Lok implant by Bio Horizons).
  3. Anodic Oxidation (TiUnite by Nobel BioCare).
  4. Titanium Oxide Blasted and Acid-Etched Implants (OsseoSpeed implant by DENTSPLY).
  • Increasing the surface wettability of implant surface was proposed to increase cellular adhesion to the implant surface contributing to an acceleration of osseointegration.
  • Hydrophilic Implants (SLActive dental implants by Straumann) are implants modified with high level of hydrophilicity. To prevent surface contact to air, SLActive implants are rinsed under nitrogen protection and stored in isotonic saline solution until insertion.
  • Multiple surface coatings are currently proposed to induce osseointegration, but more long-term research is needed to approve its commercial clinical use including:
  1. Hydroxyapatite and Nanocomposite Coatings.
  2. Growth Factors (BMP.TGF AND FGF).
  3. Extracellular Matrix Proteins (chondroitin sulfate).
  4. Peptides (Human beta defensins, RGD peptide and GL13K).
  5. Messenger Molecules (antisclerostin coatings).
  6. Drug Coatings (Statins, Zoledronate).

Discussion:

  • Different preclinical studies demonstrated the superiority of particular surface modifications in respect to histomorphometric properties and biomechanical features.
  • However, clinical studies showed no significant difference between different methods of surface treatment and most commercially available implant systems showed comparable success and survival rates.
  • The search for the ideal surface treatment modality is still ongoing and more long-term clinical studies are needed

 

Topic: Osseointegration

Author: Rittel,D., Dorogoy,A., Shemtov-Yona, K.,

Title: Modeling the effect of osseointegration on dental implant pullout and torque removal tests

Source: Clin Implant Dent Relat Res. 2018;20:683–691

DOI: 10.1111/cid.12645

Type: finite element analysis

Keywords: dental implants, finite element, osseointegration, pullout, torque

Purpose: To obtain a quantitative relationship between osseointegration and  3-dimensional variable extent of the bone-implant bonding and its influence on the measurable extraction and torque loads.

Methods: The extraction of a commercial implant from the bone of the mandible was simulated in a 3 dimensional model numerically using finite element analysis.The extraction procedures performed were the straight implant pullout test and the reverse torque test.

Results: 16% of the implant contact surface is in contact with the cortical bone, while the remaining 84% is in contact with the trabecular bone. Regarding pullout tests, the overall load- displacement characteristics are sensitive up to the first 5% of osseointegration, as an ROA of 9.5% cannot be distinguished from 100%. Concerning reverse torque tests,the resulting torque-angle relationships consist of three phases. The first phase is linear until a significant drop in the torque value, and it mostly involves the cortical bone. The second phase involves increasingly the trabecular bone component, it is nonlinear and ends with very low residual constant values of the torque. The first two phases are short and the third phase consists of the decreasing evolution of the residual torques for different ROA at high rotational angles. It can be observed that for all ROA’s, the torque drops to zero, meaning that the implant is fully released and can move upward with no restraint due to the upward extraction force. Also,the various ROA’s of the cortical bone cannot be distinguished based on load-displacement, while for the trabecular bone, only ROA <20% can be distinguished. The peak torque values of the cortical bone are higher from those of the trabecular bone. In addition, the lower ROA cause less sharp peak at the initial angle of 1-2, but increases the extremum at 5-6.

Discussion: As a limitation, although the bone-implant geometrical contact was kept to 100% in all calculations, one can consider frictional interfaces as some kind on non contacting faces.

Conclusion: The trabecular bone has a lower mechanical strength than cortical, but it can sustain higher strains to failure, so it has a higher contribution to the pullout force and extraction torque due to its high relative contact area. Finally, this study shows that the mechanical extraction test results depend on the combined relative contact area and the interfacial mechanical characteristics, and not solely to the area contact, as both factors determine the exact constraint applied to the implant. Those results suggest that the very initial stage of osseointegration is sufficient to firmly anchor the implant in the jawbone. The results of this work indicate that the torque test is more discriminant than the extraction one, while both cannot really discriminate osseointegration levels below a relative variation of 20%.

 

Bone-implant interface (Placement and Initial Healing)

Topic: osseointegration

Authors:Marão, H.F., Jimbo, R., Neiva, R., Gil, L.F., Bowers, M., Bonfante, E.A., Tovar, N., Janal, M.N.

Title: Cortical and Trabecular Bone Healing Patterns and Quantification for Three Different Dental Implant Systems.

Source: Int J Oral Maxillofac Implants. 2017;32(3):585–592

DOI: 10.11607/jomi.4856.

Type: Animal histology

Keywords: bone healing patterns, osseointegration, bone to implant interface

Purpose: To determine if different bone healing patterns through initial stages of osseointegration would be observed with three different implant systems (Nobel Groovy, Implacil, and Zimmer TSV) were used. Assessed differences in histometric levels of total bone and new bone formation during the osseointegration process.

Methods: 48 endosseous implants (10mm length) were placed bilaterally on the tibias of 8 beagle dogs. Three groups of implants were used: Group A: Nobel Groovy 3.5mm,  Group B: Implacil 3.75mm,  Group C: Zimmer TSV 3.7mm

Implants were allowed to heal for 2 and 6 weeks. Following euthanasia, nondecalcified specimens were processed for morphologic and histometric evaluation. Bone-to-implant contact (BIC) and new bone area fraction occupancy (BAFO) analyses for native and new bone were performed along the whole perimeter of each implant and separately for the cortical and trabecular bone regions.

Results: Different healing patterns and osseointegration levels were observed for each implant system as time elapsed in vivo. Interfacial remodeling was the chief healing pattern in Zimmer implants, while a combination of interfacial remodeling and healing chambers was observed in Nobel and Implacil implants.

At both 2 and 6 weeks, new bone, BIC-trabecular/cortical and new bone, BIC, trabecular presented identical patterns, with the Nobel group presenting significantly higher values than the Zimmer group. NSSD between groups detected for the NB-BIC at 2 weeks in vivo. While at 6 weeks in vivo, a significant difference was observed between the Implacil (highest) and Nobel (lowest) groups with the Zimmer group presenting intermediates values. NSSD between groups were detected when NB-BAFO-TC, BAFO-T and BAFO-C were evaluated.

When trabecular bone was evaluated, similar bone healing patterns were observed between systems despite different levels of osseointegration observed as a function of implantation time, implant system, and native and/or new bone BIC and BAFO.

Discussion: Different implant systems led to different healing patterns during early stages of osseointegration. Such variation in pattern was more noticeable in the cortical regions compared to the trabecular regions. The variation in bone healing pattern did significantly influence overall indicators of native and new BIC and BAFO during the osseointegration process.

Conclusion:

  • Osseointegration was influenced by distinct surface characteristics, surgical instrumentation, and implant macrogeometry.
  • Nobel showed highest BIC both at 2 and 6 weeks. It could be explained by macrogeometry which created healing chambers to allow for clot and bone formation.
  • Implacil had the highest BAFO, probably due to the drilling pattern and macrogeometry.
  • These results may aid in deciding the successful loading timeline for different implant systems.

Topic: biomechanical determinants of implant stability


Authors: Mathieu V, Vayron R, et al.

Title:Biomechanical determinants of the stability of dental implants: Influence of the bone-implant interface properties.

Source: J Biomech. 2014 Jan 3;47(1):3-13. doi: 10.1016/j.jbiomech.2013.09.021.

Type: review

Keywords: Biomechanical properties; Bone; Implant; Osseointegration; Stability

Background: Dental implants are widely used however, risks of failure are still experienced and remain difficult to anticipate. The stability of biomaterials inserted in bone tissue depends on multiscale phenomena of biomechanical (bone-implant interlocking) and of biological (mechanotransduction) natures.

Purpose: to provide an overview of the biomechanical behavior of the bone-dental implant interface as a function of its environment by considering in silico (via computer simulation), ex vivo and in vivo studies including animal models as well as clinical studies.

Discussion:

Description of the bone-implant interface: the interface has a complex nature due to (i) its roughness, (ii) the fact that bone is in partial contact with the implant, (iii) adhesion phenomena between bone and the implant and (iv) the time-evolving nature of the interface properties.

  • Geometrical description; bone-implant distance and micromotions: When primary stability is not sufficient, micro-movements may appear preventing good healing conditions and leading to the formation of fibrous tissue and to surgical failure. Some studies show that micromotion should not exceed 150 µm, however the precise threshold is not yet known.
  • Mechanical description: stresses and the interface; When functional loading exerted via the implant exceeds “a certain stress”, the implant is regarded as being “overloaded”, leading to possible complications such as peri-implant bone resorption. However, stresses below that are beneficial for the implant outcome and stimulate bone remodeling phenomena. The determination of the value of that threshold remains unclear.
  • Dynamic description: bone remodeling and osseointegration; implant osseointegration was discovered by Branemark. Diagram bellow shows the multi-scale and multi-time nature of the different phenomena occurring during osseointegration; Factors related to implant properties (dashed lines), to the surgeon (dotted line) and the ones relating to bone properties (solid lines).

Implant stability: a space-time multiscale issue

  • Measurement of the multiscale bone properties around the interface:
    • Histology: the gold standard measurement.
    • Small angle X-ray scattering (SXAS): is used to assess thickness, orientation, and shape/arrangement of the mineral crystals in bone tissue. Gives information about bone mineralization but no information about mechanical properties
    • Nanoindentation: investigates biomechanical properties in the microscopic scale. Has shown that Young’s modulus and hardness values are lower in the vicinity of the implant than in mature bone.
    • Scanning Acoustic Microscopy (SAM): qualitative assessment of the biomechanical microstructural properties of bone-implant interface
    • Micro Brillouin scattering: uses the photo acoustic interaction between a laser beam and a sample to measure bone speed of sound
  • Homogenization approaches of bone tissue around the interface: homogenization techniques have been developed to climb the hierarchy of scales in newly formed bone tissue, from the nanoscale up to the macroscopic level.
  • Multiscale biomechanical modeling of the bone-implant interface: Various approaches have been developed to model the mechanical behavior of the bone–implant interface such as; Finite element methods (FEM), Frictional coulomb law, non-linear anisotropic FEM, …

Implant stability assessment

  • X-ray and MRI based techniques: Limited resolution of clinical X-ray based techniques due to metal artifacts related to the presence of the implant metallic components. MRI has also been proposed but is also of limited interest due to magnetic fields disturbance. Maximum resolution level of radiography is 0.1mm which is ten times the size of a soft tissue cell. X-ray or MRI based techniques are not commonly used in order to assess the biomechanical properties of bone to implant interface
  • Invasive biomechanical methods: Tensional test, Push out/Pull out test, Removal torque analysis
  • Non-invasive biomechanical methods:
    • Empirical approaches; Hitting the implant with an instrument and listen to the noise made by the system. Insertion torque during the surgical procedure.
    • Impact based approaches: PerioTest device (Schulte et al. 1980) was originally used for evaluation of tooth mobility. Measurement leads to PerioTest value (PTV), -8 to 50. PTV correlates to mobility and level of marginal bone.
    • Resonance frequency analysis: Measurement of the first resonance frequency of the bone–implant system. Uses an L-shaped transducer or a “Smartpeg”, which is a piece screwed in the implant abutment. Measurement gives an index called Implant Stability Quotient (ISQ 0-100), system is commercialized under the name Osstell. A correlation was shown between initial ISQ value and; (i) cutting torque, (ii) bone measurements assessed empirically by the surgeon during implant placement, (iii) Cortical bone thickness, (iv) Anatomical region of implantation. Limitations:
      • Only captures the first resonance frequency, which is of limited value from a structural mechanics point of view (“oversimplification”)
      • Sensitivity of ISQ value to the implant stability depends on the implant type
      • Relationship between ISQ values and BIC remains unclear
      • Fixation and orientation of the transducer (or smartpeg) influence significantly the ISQ values
      • ISQ values are related to the bone properties at the scale of the organ, but properties at the scale of 50-200μm are critical for osseointegration
      • Quantitative ultrasounds methods: Used to assess bone mineral status, enamel thickness. Several studies show the potentiality of QUS to investigate bone quality around implants, further work is necessary.

 

Topic: Anatomy bone adaptaion
Authors:Trisi, P., Rebaudi A

Title:Progressive bone adaptaion of titanium implants during and after orthodontic load in humans.

Source: Int J Periodontics Restorative Dent. 2002 Feb; 22(1):31-43

Type: Histology

Keywords: orthodontics, implants

Purpose: To evaluate implant stability and peri-implant bone reaction by histologic and clinical evaluation after therapeutic orthodontic loads.

Methods: 41 adult patients received titanium implants (Exacta) as an orthodontic anchorage device; 12 patients received a retromolar or palatal implant to obtain tooth movement. Seven implants were removed at the end of the orthodontic therapy, after 2, 4, 6, and 12 months of orthodontic load, and processed for histologic examination.

Results: It was possible to distalize maxillary and mandibular molars and a group of teeth (molars and premolars), and to obtain tipping, uprighting, intrusion, extrusion, and transfer of anchorage in other parts of the mouth. The results showed that orthodontic therapy is facilitated and quickened using implants. All implants remained stable in the bone up to 12 months of loading, and all were osseointegrated. Microfractures, microcracks, and microcalli were observed around implants that had been placed in both low- and high-density bone. The remodeling rate was still elevated after 18 months.

Conclusion: Loading implants after 2 months of healing was shown to be safe and is considered the standard for orthodontic implants.

Topic: bone-implant contact

Authors: Tretto PHW et al.

Title: Does the instrument used for the implants site preparation influence the bone-implant interface? A systematic review of clinical and animal studies.

Source: Int J Oral Maxillofac Surg. 2018 Apr 24

Type: review

Keywords:  implant site preparation; implant survival, biomechanics, histological analysis

Purpose:  to evaluate the influence of different instruments used for implant site preparation on the bone-implant interface.

Methods: Included were randomized or non-randomized controlled clinical studies or experimental studies in animal models utilizing at least two different instruments for dental implant site preparation and evaluating bone response through any type of clinical, biomechanical or histological evaluation. Two independent reviewers screened all titles/ abstracts searched through MEDLINE/ PubMed, ISI Web of Science, and SciVerse Scopus.

Results: Initial search presented with 1027 articles and 29 articles were included in the systematic review. Publication dates range 2002-2017.

13/29 compared conventional drilling (CD) vs. Osteotomes (OT), 12/ 29 CD vs. piezosurgery (PD),1 study CD vs. Laser surgery (LS), 2 studies CD vs. osteodensification (OD), and 1 study CD vs. PD vs. LS.

CD vs. OT: Implant survival did not differ, but more bone loss seen in OT group at 3 months and no difference at 6 and 12 months. Similar ISQs values between methods was also observed. Some variation at baseline but after 3 months no difference. Histological evaluation showed no initial differences of bone -implant contact (BIC), one study found better BIC after 28 days. Two studies showed better initial BIC in OT group but no difference at 8 weeks. One study showed significant increase in temperature in OT group, but all temperatures were below necrosis threshold. Bone density studies showed SS higher values for OT group. One study showed new bone formation earlier with OT than CD, however one study showed high interfacial strains that caused fractures and triggered a prolonged period of bone resorption.

CD vs. PD: Crestal bone loss, PD, GI, PI no difference between groups. Clinical studies showed similar implant survival. Biomechanical analysis assessed: ISQ no difference between groups in 60% of studies. Two studies revealed higher ISQ for PD group but after 12 weeks no difference. Histological BIC analysis revealed no difference between groups. One animal study showed more rapid healing around implants using PD with more organized newly formed bone tissue.

CD vs. LS: One animal study analyzed, histological evaluation showed lower BIC for LS group after 2 weeks, but no difference at 12 weeks. LS osteotomy also resulted in wider gaps at peri—implant interface.

CD vs. PD vs. LS: one animal study:  no difference in BIC

CD vs. OD: 2 animal studies observed: all biomechanical evaluations presented significant benefits with OD group. Histological evaluation showed SS higher BIC in OD group as well as higher bone volume around implants.

Meta-analysis revealed NSSD between CD vs any other technique utilized for osteotomy preparation.

Conclusion: The present study’s findings demonstrated different results among the methods and outcomes evaluated. Clinical longevity of implants in all studies comparing CD vs. OT, and CD vs PD showed no differences in implant survival. Clinical comparisons between CD vs OT or PD was performed only in short-term follow-up periods of 2 years, so longer studies with greater populations is needed. The use of ODs showed promising results but only evaluated in animal models and also short-term periods. General observations of this review: OT did not improve the BIC in comparison to CD, but OT still useful for bone expansion. PD seems to have better biologic response when compared to CD.

 

Topic: Osseointegration

Authors: Trisi P, Berardini M, Falco A, Vulpiani MP

Title: Validation of value of actual micromotion as a direct measure of implant micromobility after healing (secondary implant stability). An in vivo histologic and biomechanical study.

Source: Clin Oral Implants Res. 2016; 27: 1423-30

DOI: 10.1111/clr.12756

Type: Animal study (Sheep)

Keywords: %bone-to-implant contact, dental implant, osseointegration, secondary stability, value of actual micromotion

Purpose: To test the relationship between the value of actual micromotion (VAM) and other parameters related to osseointegration such as reverse torque (RTV), implant stability quotient (ISQ) value, %BIC, %Bone volume (BV) and vertical bone loss after 2 months of implant healing in the iliac crest of sheep.

Materials and Methods: Twenty-four 3.8 × 11.5 mm implants (Dynamix, Cortex, Shlomi, Israel) were inserted in sheep iliac crests. The animals were sacrificed after 2 months, and the freshly retrieved bone blocks were immediately fixed on a customized device to calculate the value of actual micromotion (VAM) according to a previously described technique. Implant stability quotient (ISQ) values, and reverse torque value (RTV). Histology was performed to assess %bone-to-implant contact (%BIC), bone volume percentage (%BV) and crestal bone loss (CBL) were also calculated for each implant. Statistical correlations between VAM and the other parameters were calculated.

Value of Actual Micromotion: 11mm tall healing abutments are affixed to the implants. On one side force is applied to the abutment at 25N/m and on the other side a micromotion detection device is used to collect data. This detects micromotion during loading.

Results: All 24 implants had similar values for insertion torque and ISQ at placement (average IT + 67.29N/m and average ISQ 56.23). 3 implants failed after 2 months, all of which had extremely high VAM and low RTV, low %BIC and high CBL. Data correlation analysis between the examined parameters showed that VAM significantly correlates (P < 0.05) to RTV, %BIC, ISQ and CBL.  Histologic analysis showed bone formation against the titanium surface with implants achieving a high degree of osseointegration.

Conclusion: As VAM showed to be statistical correlated to the other parameters of osseointegration, it may be used to clinically check the amount of implant osseointegration, secondary stability and CBL. Future studies are needed to confirm these results and determine that this is true micromotion and not elasticity of bone. An instrument to measure VAM in the oral cavity still needs to be developed.

 

Topic: Bone Implant Interface

Authors: Salvi, et al.

Title: Temporal sequence of hard and soft tissue healing around titanium dental implants

Source: Periodontol 2000. 2015. June;68(1):135-52

DOI: 10.1111/prd.12054

Type: review

Keywords: hard tissue; soft tissue; implants; osseointegration; bone; interface

Purpose: to summarize the evidence on the temporal sequence of hard and soft tissue healing around titanium dental implants in animal models and in humans. 

Hard and soft tissue integration of titanium dental implants in animal models

Osseointegration: early events

  1. 2 hours after implantation: thread in contact with bone providing mechanical anchorage
  • Void between pitch and implant body established geometrically well-defined wound chamber filled with blood clot
    • Clot has erythrocytes, neutrophils, monocytes/macrophages
  1. Day 4, granulation tissue replaces clot and CT matrix established
  • Contains mesenchymal cells, and vascular structures

Osseointegration: bone modeling

  1. 1 week, CT is rich in vasculature
  • Cell-rich immature bone in CT that surrounded blood vessels
  • Woven bone in the center of the chamber and rough surface of implant = “contact osteogenesis”
  1. 2 weeks, woven bone surrounds entire implant via a continuous coat on implant body
  • Osteoclast formation noted on bone surface which resulted in resorption adjacent to implant surface
  • Mechanical stability of implant replaced by biological bonding and stability
  1. 4 weeks, mineralized bone extends from bone surface into chamber and coats implant and central chamber filled with primary spongiosa (rich is vasculature and mesenchymal cells)

Osseointegration: bone remodeling

  1. 6-12 weeks, chambers filled with mineralized bone and consists of primary/secondary osteons while bone marrow surrounds mineralized bone
  • Bone reinforced by lamellar bone, which allows coping of bearing load

Osseointegration: comparison of surfaces

  1. Roughened sand blasted and acid-etched implants showed higher bone-implant contact compared to polished surface
  2. Contact osteogenesis and distant osteogenesis noted in acid-etched and roughened sandblasted surfaces
  3. Distant osteogenesis noted in polished surface

Peri-implant soft-tissue integration

  1. 2 hours after flap reposition, large amounts of neutrophils infiltrate and degrade coagulum of chamber
  • Dense fibrin network forms primitive seal between flap and implant
  1. At 1-2 weeks of healing, epithelial proliferation noted
  2. After 2 weeks, fibroblasts dominated in CT
  3. At 4 weeks, fibroblasts decrease and collagen fibers organized
  4. At 6-8 weeks, mature barrier epithelium and implant-mucosal seal is functional

Osseointegration of titanium dental implants in humans

Early healing events around screw-type implants in humans (implants placed then retrieved/explanted)

  1. There was a progressive decrease in the percentages of old bone, soft tissue and bone debris covering the implant surfaces, but there was a gradual increase in the bone-to-implant contact of new bone over time
  2. Presence of bone debris and solid bone particles on the implant surfaces and in the peri-implant tissues

Healing after 1 week

  1. Old, mainly compact bone covered 22% of Straumann SLA/active implant surfaces mainly in coronal aspect
  • Initial bone formation noted at 7 days
  • Implant areas not covered with old bone were coated with bone debris or layer of new bone matrix

Healing after 2 weeks

  1. Old bone covered 28% of surfaces
  • Most of this bone was cortical and in coronal aspect
  • Bone resorption noted
  • New bone trabeculae from old bone onto implant surface (12% SLA; 15% SLA-active)

Healing after 4 weeks

  1. Old bone covered 14% and new bone 28%
  • Bone resorption closer to implant surface
  • Bone debris found in mineralized new bone
  • New bone trabeculae from old bone onto implant surface (32% SLA; 48% SLA-active)

Healing after 6 weeks

  1. Old bone covered 8%-14%
  2. Bone apposition on bone-implant surface and bone marrow maturing

Molecular mechanisms of early healing events of osseointegration

Inflammation

  1. process of bone formation leading to osseointegration is accompanied by a marked decrease in the immune-inflammatory response following implant placement.

Osteogenesis

  1. dental implant changes the nature of bone healing, with an acceleration of osteogenesis-associated mechanisms being observed
  • vast majority of osteogenesis-associated genes are induced during the first 2 weeks of osseointegration

Angiogenesis

  1. angiogenesis is an important biological process that is regulated during osseointegration and bone regeneration

Neurogenesis

  1. large number of neurogenesis-related genes compared with skeletogenesis-related genes are up-regulated during the first 2 weeks of osseointegration
  • large number of the neurogenesis-associated genes are associated with axon formation and neural signal transduction, suggesting that neurogenic tissues are regenerated during osseointegration.

Signaling Pathways

  1. the IjB kinase/nuclear factor-kappaB pathway is the major pathway
  • intimately associated with inflammation but also plays a key role in inflammation induced bone loss
  1. Ras family of signal transduction proteins (Rho and Rab) are also involved in the osseointegration process

Influence of Surface Roughness and chemistry on molecular mechanisms of osseointegration

  1. A  micro-rough implant surface showed accelerated gene expression of the bone matrix molecules, along with the up-regulation of bone sialoprotein, collagen III and integrins during the first week of osseointegration
  2. surface hydrophilicity exerts a positive regenerative response characterized by enhanced osteogenesis

Conclusion:

  1. The attachment and maturation of the soft tissue complex to implants becomes established 6–8 weeks after surgery.
  2. Implant placement into alveolar bone starts healing events with clot formation and then bone maturation in contact with the implant surface
  3. osseointegration is associated with a decrease in inflammation and an increase in expression of osteogenesis-, angiogenesis- and neurogenesis-associated genes during the early stages of wound healing

Topic: Osseointegration


Title: Early bone formation adjacent to rough and turned endosseous implant surfaces. An experimental study in the dog

Author: Abrahamsson I, Berglundh, T, et al.

Source: Clinical Oral Implants Research, 15 (2004), pp. 381–392

Type: Histologic study, animal model

Keywords: SLA, osseointegration, implant surface

Objective: To validate a proposed model (as proposed by Berglundh et al. 2003) and to evaluate the rate and degree of osseointegration at turned (T) and sand blasted and acid etched (SLA) implant surfaces during early phases of healing.

Methods: Twenty Labrador dogs received totally 160 experimental devices (solid screw implant with either a SLA or a T surface configuration) as to evaluate healing between 2h and 12 weeks. Histometric and morphometric analyses were performed.

Results: The sections provided an overview of the various phases of tissue formation, while the decalcified, thin sections enabled a more detailed study of events involved in bone tissue modeling and remodeling for both SLA and T surfaces. The initially empty wound chamber became occupied with a coagulum and a granulation tissue that was replaced by a provisional matrix. The process of bone formation started already during the first week. The newly formed bone present at the lateral border of the cut bony bed appeared to be continuous with the parent bone, but on the SLA surface woven bone was also found at a distance from the parent bone. Parallel-fibered and/or lamellar bone as well as bone marrow replaced this primary bone after 4 weeks. In the SLA chambers, more bone-to-device contact, more initial woven bone and earlier lamellar bone formation was found than in the T chambers.

Conclusions:Osseointegration represents a dynamic process both during its establishment and its maintenance. While healing showed similar characteristics with resorptive and appositional events for both SLA and T surfaces, the rate and degree of osseointegration were superior for the SLA compared with the T chambers.

Topic: Osseointegration


Authors: Berglundh T, Abrahamsson I, et al.

Title: Bone healing at implants with a fluoride-modified surface: an experimental study in dogs.

Source: Clinical Oral Implants Research, 18 (2007), pp. 147–152

Type:Animal study

Keywords:dental implants, histology, osseointegration, titanium

Purpose: Study early stages of osseointegration to implants with a fluoride-modified surface.

Methods: Six mongrel dogs, about 1-year old, were used. All mandibular premolars and the first mandibular molars were extracted. Three months later, mucoperiosteal flaps were elevated in one side of the mandible and six sites were identified for implant placement. The control implants (MicroThread) had a TiOblast surface, while the test implants (OsseoSpeed) had a fluoride-modified TiOblast surface. Both types of implants had a similar geometry, a diameter of 3.5 mm and were 8 mm long. Following installation, cover screws were placed and the flaps were adjusted and sutured to cover all implants. Four weeks after the first implant surgery, the installation procedure was repeated in the opposite side of the mandible. Two weeks later, biopsies were obtained and prepared for histological analysis. The void that occurred between the cut bone wall of the recipient site and the macro-threads of the implant immediately following implant installation was used to study early bone formation.

Results:The amount of new bone that formed in the voids within the first 2 weeks of healing was larger at fluoride-modified implants (test) than at TiOblast (control) implants. It was further observed that the amount of bone-to-implant contact that had been established after 2 weeks in the macro-threaded portion of the implant was significantly larger at the test implants than at the controls.

Conclusions:It is suggested that the fluoride-modified implant surface promotes osseointegration in the early phase of healing following implant installation.

 

Topic:Bone adaptive capacity


Author:Greenstein G, Cavallaro J, Tarnow D.

Title: Assessing bone’s adaptive capacity around dental implants: a literature review.

Source:J Am Dent Assoc. 2013 Apr;144(4):362-8

Type:Review

Keywords:Bone; dental implants; osseointegration; resorption

Purpose:To review concepts pertaining to bond adaptation that may account for high survival rates of prostheses that are subjected to increased stresses.

Discussion:

Bone Mechanotransduction

  • Mechanotransduction=the mechanism that permits bone to detect stimuli.
  • It is thought that bone cells sense and respond to their mechanical environment by changing their biological and biochemical actions.
  • It is strain, not stress, that precipitates alteration of the bone response
  • 3 Possible stimuli for Osteocytes
    • 1-Direct mechanical stimulation
    • 2-Fluid flow induced by shear stress
    • 3-Bone Microdamage
  • The prevailing concept suggests that under dynamic loading, bone matrix deformation produces an interstitial fluid flow. This flow creates shear stress that stimulates osteocytes. Osteocytes act as mechanosensors and convey signals to adjacent cells (osteoblasts) through the intercellular communication network.

Rules For Bone Adaptation to Mechanical Stimuli

  • According to Turner, the following 3 rules characterize the response of bone to stress
    • Bone adaptation is determined by dynamic, rather than static, loading, and it is the alteration of stress, not its consistency, that produces bone modifications
    • A short episode of mechanical loading is required to begin the adaptive response
    • Bone cells accommodate to customary mechanical loading, making them less responsive to routine loading signals.
  • From these, it can be deduced that abnormal stress and strains drive structural change.

Stresses and Strains on Bone

  • Magnitude of occlusal load, cycle number, direction and frequency all can affect the quantity of stress.
  • The relationship between stress and strain establishes the modulus of elasticity (stiffness) of a material.
  • According to Frost, a certain amount of stress is required to maintain bone homeostasis.
    • Microstrains from 0 to 50atrophy
    • 50 to 1500normal bone modeling
    • 1500 to 3000overload
    • >3000possible destruction

Bone Microdamage

  • Fatigue: bone has lost strength and stiffness due to repetitive loads.
  • Microcracks: a discontinuity in the calcium-rich matrix and reflects fissures and breaks in the hydroxyapatite.

Bone’s Proliferative response to stress around dental implants

  • If the load is above a certain threshold, bone loss or loss of osseointegration can occur.
  • If functional load is below a destructive threshold, it can be stimulatory and induce apposition of bone and increased osseous density.
  • There is much evidence that supports the concept that bone can respond to stress and modify itself to withstand increased mechanical forces.

Remodeling

  • Jee estimated that about 20 percent of the cortical and cancellous bone surfaces (endosteal and periosteal) are remodeling at any point in time.
  • The replacement rate of cortical bone is 7.7% per year
  • The replacement rate of cancellous bone is 17.7% per year
  • Garetto showed that within 1mm of implants, there was a layer of bone that remodeled rapidly. The turnover rate was three to nine times faster per year within the 1mm of the implants.
  • Bones such as the mandible that experience loading from varying directions exhibit more platelike trabecular architecture. An advantage of this structure is its ability to manage forces from different directions.
  • High load areas usually manifest dense platelike architecture, whereas low load areas usually demonstrate low-density rodlike structures.

Conclusion: There are 2 possible explanations for the success of prosthetic constructs. First, is that bone is stronger than expected and can tolerate increased stress. Second is that as long as the stress/strain level does not increased beyond a threshold that causes bone destruction, bone has the ability to remodel and model and increase its osseous density.

Topic: Fracture


Authors: Mangano C, Piattelli A, Mortellaro C, Mangano F, Perroti V, Iezzi G

Title: Evaluation of peri-implant bone response in implants retrieved for fracture after more than 20 years of loading. A case series

Source:J Oral Implantol. 2013 Aug 21

Type: Case series

Keywords: Bone remodeling, human histology, implant surfaces, retrieved dental implants

Purpose: To present a histological case series of the peri-implant bone responses in implants retrieved for fracture after more than 20 years loading period.

Methods: 5 implants retrieved for bodily fracture in 5 patients were found to be analyzed. The surface of these implants was obtained by sandblasting, followed by acid-etching for 30 minutes. The implants were then washed with hydrogen peroxide and dried with high heat. None of the implants were immediately loaded. In 3 cases, implants supported partial fixed bridges, while in 2 cases there was a mandibular ovendenture supported by 2 implants. Four implants were located in the mandible, and 1 in the maxilla. All implants were retrieved with a 5-mm trephine bur. Histological analysis and histomorphometry of the percentages of bone-implant contact were carried out.

Results: Compact, mature bone in close contact with the implant surface was observed in all specimens, with no gaps or connective tissue at the interface. Primarily newly formed bone was observed in proximity of the implant surface. In the most coronal portion of one implant, connective tissue adhering to the implant surface was detected. Bone-to-implant contact percentage ranged from 37.2-76%.

Conclusion: Implant effectiveness is largely dependent on biological stability and integration between bone and implant. Endosseous implants may function over a wide range of degrees of osseointegration.

Topic:sandblasted and acid-etched implant surfaces
Authors:Barewal R et al.
Title: Resonance frequency measurement of implant stability in vivo on implants with a sandblasted and acid-etched surface.

Source: J Oral Maxillofac Implants 2003; 18:641-651

Type: Clinical Study

Keywords: bone, clinical trials, dental implants, early healing, endosseous dental implantation,

implant stability, resonance frequency analysis

Purpose: to understand pattern of stability changes and early healing around single-stage roughened-surface implants during the first 2 ½ months in different bone types.

Methods: Twenty patients had 1 to 4 implants placed in the posterior maxilla or mandible. Bone type was classified into 1 of 4 groups according to the Lekholm and Zarb index (1985). RFA was used for direct measurement of implant stability on the day of implant placement and consecutively once per week for 6 weeks and at weeks 8 and 10.

Results:

Twenty-seven ITI SLA implants placed in the premolar and molar regions of the maxilla and mandible were evaluated. Early failure occurred with 1 implant related to parafunction. The remaining 26 implants were distributed as follows: 29.6% in Type 1 bone, 37% in Type 2 or 3 bone, and 33.3% in Type 4 bone. The lowest mean stability measurement was at 3 weeks for all bone types. The percentage decrease in stability from baseline to 3 weeks was highest for Type 4 bone (8.6%), as was the percentage increase in stability from 3 to 10 weeks (26.9%). A Bonferroni adjusted Student t test comparison of bone groups at each time point revealed highly significant differences between implant stability in Types 1 and 4 bone at 3 weeks (P = .004) and a moderately significant difference between Types 2, 3, and 4 bone (P = .08) at 3 weeks. Implant stability did not change significantly during the 10-week period in Type 1 bone (P  .10). With the same test, by 5 weeks, no bone groups showed any difference in implant RFA measurements (P = 1.0). Discussion: This study demonstrated the lowest values for implant stability at 3 weeks after placement for all bone types. This effect was statistically significant and most pronounced in Type 4 bone.

Conclusion: The lowest values for interfacial stiffness between the bone and the implant were found at 3 weeks, particularly in type 4 bone. Healing responses of Types 2 and 3 bone were more similar to Type 1 than to Type 4 bone. The RF values at 6 weeks did not differ from those at 10 weeks in all bone types; this supports the idea of a 6-week healing period for ITI implants in Types 1, 2, and 3 bone. The lack of significant change in stability from 5 to 10 weeks for Types 1, 2, and 3 bone supports further testing of an even shorter healing protocol. With regards to Type 4 bone, the current 12- week healing period could be evaluated and potentially shortened. There was no significant difference in the pattern of stability changes among different bone types after 5 weeks of healing.

Topic: implant stability per bone type

Authors: Alsaadi G, Quirynen M, Michiels K, Jacobs R, Steenberghe D

Title:A biomechanical assessment of the relation between the oral implant stability at insertion and subjective bone quality.

Source: Journal of Clinical Periodontology 2007; 34: 359-366.

Type: Clinical

Keywords:biomechanics; bone quality; dental implants; insertion torque; oral implants; osseointegration; periotest; RFA

Purpose:To evaluate the validity of subjective bone quality assessment.

Methods:A total of 298 patients treated with implants. Bone quality assessment performed immediately after implant placement and using the Lekholm & Zarb index. Tactile sensation was assessed for cortical bone and trabecular bone during high speed drilling. A scale from 1 (very thick cortex/dense trabecular bone) – 3 / 4 (thin/ poorly mineralized trabecular bone). The bone quality was assessed during implant insertion by an electronic torque force measurement device, which measures the torque force while tapping or inserting the implant at slow speed. The rigidity of implant-bone continuum was assessed by resonance frequency analysis taken at implant insertion and before abutment insertion, through a peg attached to the fixture, and an ISQ value is presented. This runs from 1-100, the higher the ISQ the more stable the implant. Periotest also measured the rigidity. After connecting a temporary abutment 4 mm in length, this device measures the damping capacity of the implant bone continuum. A rod is placed perpendicular to the abutment at a distance of 2 mm and it is accelerated electromagnetically. When rod hits the implant, it is decelerated. The faster the deceleration, the greater implant stability. Values range from -8 (very stable) to +50 (extremely mobile).

Results:Subjective assessment was related to PTV, ISQ and placement torque in the crestal, the second and the apical third.

ISQ and PTV were also compared with the bone quality assessed according to the Lekholm & Zarb index. A significant relationship was detected.

– Grade 1: 5.3, 73.3

– Grade 3 or 4: 1.6, 55

ISQ and PTV recorded at implant insertion were also compared with the bone quality assessed according to the surgeon’s tactile sensation. A significant relationship was detected between ISQ, PTV and cortical bone grades and between ISQ and trabecular bone grades

For surgeon’s tactile sensation, a good correlation was noted for the presence of a thick cortex: – 4.6, 70.3 or a thin one: – 0.3, 65.9. For dense trabecular bone, the values were – 2.8, 69.4 while for poor trabecular bone, the values were – 1.7, 66.4

Conclusion:

Subjective assessment of bone quality is related to PTV, ISQ and placement torque measurements at implant insertion.