Research Abstracts

10/07/05

Immediate Stabilization of Implants for General Dentists

Speratti. D., ADA Annual Meeting, Philadelphia, PA October 2005

Immediate stabilization and function of dental implants has become a preferred method of treatment. Clinical research and engineering improvements have allowed clinicians to offer the treatment more frequently. Leading practitioners utilize the method of “Immediate Loading or Stabilization”. This presentation intends to show a predictable and affordable technique for general practitioners so that they may be able to achieve aesthetic results without additional surgical procedures. Clinical pictures will be presented.

08/25/05

Immediate Stabilization & Function of Dental Implants

Speratti. D., Hirayama, M., FDI Annual Meeting, Montreal, Canada August 2005

Abstract: Immediate Stabilization and Function (ISF) of dental implants has become a preferred method of treatment. Clinical research, engineering improvements, and patients’ needs have allowed clinicians to offer the treatment more frequently. Leading practitioners utilize the method of “Immediate Loading or Stabilization”; however, many clinicians are still skeptical about its success.
Materials and Methods: In this on-going clinical study of 405 fin-type implants (Hydroxylapatite and Titanium Plasma Spray), 142 patients were treated from November 1998 to July 2004 by means of the ISF.  All implants were immediately stabilized by fabrication of a temporary prosthesis bonded to natural dentition or splinting implants to one another.
Results: During this period of time, 128 implants successfully integrated and were restored.  14 failed to integrate and were replaced.
Conclusion: With this technique, a clinician may provide immediate temporary restorations of implants in function at the same time of implant placement without additional risks impacting the success of treatment.

03/11/05

Fit of Fixture/ Abutment Interface of Internal Connection Implant Systems

Kim, C., Gwangju,Chung., AO Annual Meeting, Orlando, FL March 2005

Objective: The purpose of this study was to evaluate the machining accuracy and consistency of implant/ abutment/screw combination of internal connection type.
Materials and Methods: In this study, each two randomly selected internal implant fixtures from ITI, 3i, Avana, Bicon, Friadent, Astra, and Paragon system were used. Each abutment was connected to the implant with 32 Ncm torque value using a digital torque controller or tapping. All samples were cross-sectioned with grinder-polisher unit (Omnilap 2000 SBT Inc) after embedded in liquid unsaturated polyester (Epovia, Cray Valley Inc.) Then optical microscopic and scanning electron microscopic (SEM) evaluations of the implant-abutment interfaces were conducted to assess quality of fit between mating components.
Results: 1. Generally, the geometry of the internal connection system provided for a precision fit of the implant/abutment interface. 2. The most precision fit of the implant/abutment interface was provided in the case of the Bicon System which has no screw. 3. The fit of the implant/abutment inte3rface was usually good in the case of ITI, 3i and Avana system and tha amount of fit of the implant/ abutment was similar to each other. 4. The fit of the implant/ abutment interface was usually good in the case of Friadent, Astra and Paragon system. The case of Astra system with the inclined contacting surface had the most intimate contact among them. 5. Amount of intimate contact in the abutment screw thread to the mating fixture was larger in assembly with two-piece type which is separated screw from abutment such as Friadent, Atra and Paragon system than in that with one-piece type which is not separated screw from abutment such as ITI, 3I and Avana system. 6. Amount of contact in the screw and the screw seat of abutment was larger in assembly of Friadent system than in assembly of Astra system than in assembly of Astra system or Paragon system.
Conclusion: Conclusively, although a little variation in machining accuracy and consistency was noted in the samples, important features of all internal connection systems were the deep, internal implant-abutment connections which provide intimate contact with the implant walls to resist micromovement, resulting in a strong stable interface. From the results of this study, further research of the stress distribution according to the design of internal connection system will be required.

03/11/05

Morphological and Chemical Assessment of Two Thin-film Ion Beam Assisted Deposited Bioceramic Coated Surfaces on Ti-6Al-4V Implants

Coelho, P.G., Lemons, J.E., AO Annual Meeting, Orlando, FL, 2005

Nanotechnology has strongly affected biomaterials science and engineering, once reduced condensed matter domains may deeply alter biomaterials electronics properties and thus their in-vivo behavior. It has been shown that nano-thick Ion Beam Assisted Depoisted (IBAD) bioceramic coatings increase osteoblatic activity at early implantation times, and studies have indicated higher bone-biomaterial interfacial shear strength values for IBAD coated implants. The purpose of this study was to morphologically and chemically assess 2 types of IBAD bioceramic coatings and correlate these evaluations to their in-vivo performance. Control (C) and nano-thick IBAD (IBAD 1, IBAD 2) implants were morphologically evaluated on a SEM under various magnifications, following by survey and site-specific EDS elemental assessment. Superficial layer chemical analyzes were performed by XPS (survey and site-specific), and Ca/P ratios were calculated from spectra output. Results showed no evidence of bioceramic coating presence on all implants (IBAD 1, IBAD 2 –too thin for SEM detection), although ion beam assisted surface etch was evident for IBAD implants. EDS showed the presence of Ti and Al for all specimens, and Ca and P presence for IBAD 2 implants only. XPS spectra showed the presence of Ti, Al, C, O and Si for C implant surfaces, Ti, Al, C, O, Si, Ca, and P for IBAD 1 implant surfaces, and C, O, Si, Ca, and P for IBAD 2 implant surfaces, revealing absorbed molecules (Si and C) for all implants and higher thickness for IBAD 2 implants. Stoichiometry ratios were 1.5 and 2.2 for IBAD 1 and IBAD2 respectively. According to the results obtained, IBAD 2 coatings were thicker than IBAD 1, and both were in the nanorange thickness. Stoichiometry ratios revealed that IBAD 1 and IBAD 2 were different than crystalline HA, suggesting that IBAD coating dissolution rates are potentially higher than crystalline HA. These findings were consistent with animal experiments, where biological response increases were detected at early implantation times due to coating dissolution. Coating nanothickness also allowed direct bone contact to implant metallic substrate, as per histological analyzes, as thin coatings disappear as a function of time in-vivo. IBAD coatings physico/chemical characteristics were desirable features for implant biomechanical fixation competence.
03/10/05

Gingival Tissue Health Around Locking-Taper Implant-Abutment Connections

Coelho, P.G., Materials Science & Engineering, Birmingham, AL, USA, Geurs, N.C., University of Alabama, Birmingham, USA, Freire, J.N.O., Universidade Federal De Santa Catarina, Florianopolis, Brazil, Coelho, A.L., UNICENP, Curitiba, Brazil, and Speratti, D., Faulkner Hospital, Boston, MA, USA


Objective: to clinically/histologically evaluate gingival tissue around locking taper connected implants in a beagle dog model.
Materials and Methods: Six beagle dogs were acquired 12 weeks prior to surgical procedures. Five weeks prior to euthanization, left mandibular 4th premolars were extracted, followed by immediate placement of two 3.5 mm diameter by 8 mm length endosseous implants at the mesial and distal root sockets. Locking taper abutments were installed to distal implants and the flap was closed by standard suture techniques. Three weeks prior to euthanization, locking taper abutments were installed on left mandibles mesial implants and the same surgical procedure previously described was used to place an implant of same dimensions on the mesial root socket, followed by abutment installation. All surgical procedures were followed by a single dose AB protocol. No mechanical/chemical plaque control was performed, and a crunchy diet was utilized throughout the study. After euthanization, mandibles were retrieved and abutments removed from implants. 5 µm thick soft tissue sections were obtained in the bucco-lingual direction aiming implants' long axis central region (H. and E. stained).
Results: Periodic clinical evaluations revealed absence of inflammation signs. Histological sections resembled healthy mucosal tissue for all 18 specimens. The junctional epithelium was well organized and void of intra cellular spaces. Neutrophils were found and few lymphocytes were noted. No vascular proliferation apical to junctional epithelium was observed.
Conclusion: Histological sections revealed that gingival tissue around locking taper connected implants were consistent with healthy gingival tissue.

03/10/05

Biomechanical Performance of IBAD Thin-Coated Implants at Early Implantation Times

Coelho, A.L., UNICENP, Curitiba, Brazil, Coelho, P.G., University of Alabama at Birmingham, Birmingham, USA, Freire, J.N.O., Universidade Federal De Santa Catarina, Florianópolis, Brazil, Suzuki, M., University of Alabama at Birmingham, Birmingham, USA., IADR General Session; Baltimore, MD

Desirable features of bioceramic thin-coated implants include controlled composition and thickness plus enhanced adhesion to metallic substrates. Also, metallic substrate exposure with subsequent bone direct contact to the implant surface as a function of time in-vivo may be a potential advantage compared to commercially available bioceramic coatings. Objective: compare the mechanical fixation of Ion Beam Assisted Deposited (IBAD) coated implants versus a non-coated grit-blasted/acid-etched (Control) treated implant surface. Methods: three male adult beagle dogs received 2-4 cylindrical implants on the proximal tibiae following sterile procedures. Left and right limbs provided specimens that remained for 5 and 3 weeks in-vivo respectively. After euthanization, the limbs were retrieved by sharp dissection, the implants received a connecting screw in order to adapt to a torque testing apparatus installed in a universal testing machine. Implants were torqued at a 0.5 in/min rate and maximum loads to interfacial failure were recorded. ANOVA was performed with Max Torque as the dependent variable, and time in-vivo and surface type as independent variables at 95% level of significance. Results: no post-surgical inflammation/infection was observed. Radiographic evaluation revealed bone contact to implant for all groups. Surface treatment had a significant effect on maximum torque value, IBAD= 79.55±7.21 N·cm and Control= 62.76±6.37 N·cm. Time in-vivo did not have a significant influence on maximum torque value, 3 weeks=62.52±6.66N·cm and 5 weeks= 67.23±6.9 N·cm. Conclusion: According to the results, IBAD coated implants presented higher anchorage values compared to control implants, supporting favorable conditions for early functional loading of these implants.

10/01/04

Evaluating the Bacterial Seal of an Implant-Abutment Connection

Dibart, S., AAP Annual Meeting, Orlando, FL, 2004

Background: In the submerged implant design, the quality of the implant-abutment connection is thought to play a critical role in preserving the alveolar crestal bone levels from loss due to oral bacteria. Oral microorganism that would colonize that structure are suspected to initiate inflammation and promote bone loss over time. Methods: In order to test the efficacy of an implant-abutment seal to the bacterial challenge in vitro, a 2 phase experiment was devised. Phase 1: testing the ability of the seal to shield the implant well from outside bacteria. 10 abutments were seated on 10 wide body implants and then immersed in culture tubes containing a bacterial mixture. They were incubated for 24 hours anaerobically at 37°C. The abutments were then separated from implants, carbon coated, and the inside well analyzed for bacteria presence using a scanning electron microscope. Phase 2: testing the ability of the seal to prevent bacterial seepage out from the implant well. 0.1µl of a bacterial mix was deposited at the apical end of abutment posts, which were then carefully inserted into implant wells. The implant/abutment units were immersed, individually, in culture tubes containing a sterile broth and incubated anaerobically at 37°C for 72 hours. The broths were then plated on agar plates to check for bacterial growth.
Results: Phase 1: Scanning electron microscopy did not show any evidence of bacterial presence into the implant wells. Phase 2: There was no evidence of bacterial growth on the agar plates.
Discussion: The tested implant abutment seal was hermetic to oral bacteria in vitro, with no microorganisms transiting from the "outside-in" or the "inside-out".
10/01/04

Aesthetic Dental Implant Restorations

Speratti, D., ADA General Session, Orlando, FL, October 2004

Aesthetic restorative procedures on dental implants are known to be complexes and difficult to achieve, challenging clinicians and concerning patients where aesthetic is paramount to their needs. The technique shown in this presentation allowed the clinician to insert a screwless and cementless crown into a dental implant with no gap between the crown and the abutment, bringing an immediate aesthetic result. Clinical pictures will be shown in this presentation.

09/01/04

Comparison of the Periodontal Performance of the Integrated Abutment Crowns, Porcelain Fused to Metal Crowns and Teeth: A 2-year retrospective Cohort Study

Urdaneta, R., et al. Oral Presentation OSSEO, September 2004

The Integrated Abutment Crown (IAC) is a technique for the fabrication of single-tooth implant-supported restorations where the abutment and the crown material are one integral unit without the use of any screws or cement. There is no clinically discernible interface between the veneer material and the implant abutment due to a chemical bond. The precision of the prosthetic margin has been shown to be more important for the maintenance of gingival health than its location above or below the gingival margin (Richter and Veno, 1973). It was hypothesized that the gingival tissues would respond positively to a restoration without a crown margin. Purpose: The purpose of this 2-year retrospective clinical study was to compare the periodontal health around Integrated Abutment Crowns, Implant and tooth-supported metal ceramic crowns and adjacent natural teeth. Materials and Methods: 221 implants placed in 62 patients, with a mean age of 58.2 years, 56% were placed in the maxilla and 44% placed in the mandible. Of the prosthetic restorations, 151 were Integrated crowns, 70 were implant-supported Metal ceramic crowns, and 65 were tooth-supported metal ceramic crowns. Patients were recalled and the following periodontal measurements were obtained: Gingival index, modified plaque index, sulcular bleeding index and pocket depth. Results: The 2-year survival rate for Integrated crowns was 98.56%. Two Integrated crowns were removed, one due to implant failure. No significant differences in gingival inflammation and sulcular bleeding were observed between Integrated abutment crowns and unrestored teeth notwithstanding the higher plaque accumulation observed around the Integrated crowns. Furthermore, Metal ceramic crowns on implants had the highest bleeding index and the difference between the Integrated crowns was statistically significant. Teeth, regardless of restoration type, had lower pocket depths than implants. Conclusion: The gingival response around the integrated abutment crowns was similar to the health of the marginal tissues surrounding unrestored teeth. There was significantly less bleeding upon probing around Integrated abutment crowns than around implant supported metal ceramic crowns, this may be explained by the absence of a cement interface on the integrated crowns.

08/01/04

A Photoelastic Stress Analysis of Fixed Partial Dentures with Bicon Implants on Mandibular Posterior Area

Kang, JU., Kim, NY., Kim, YL., and Cho, HW., Korean Acad Prosthodont. 2004 Aug

Statement of Problem: Several prosthetic options are available for the restoration of multiple adjacent implants. A passively fitting prosthesis has been considered a prerequisite for the success and maintenance of osseointegration. Passivity is a particular concern with multiple implants because of documented inaccuracies in the casting and soldering process. One way to avoid this problem is to restore the implants individually, however, the restorations of individual adjacent impants requires careful adjustment of interproximal contacts.
PURPOSE: The purpose of this study was to compare the stress distribution pattern and amount surrounding Bicon implants with individual crowns and splinted restorations.
Material and Methods: A photoelastic model of a human partially edentulous left mandible with 3 Bicon implants(4*1 mm) was fabricated. For non-splinted restorations, individual crowns were fabricated on 3 abutments (4.0*6.5 mm, 0 degree, 2.0 mm post, Bicon Inc., Boston, USA) After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal (8 micrometershim stock drags without tearing), medium(40 micrometer), and heavy(80 micrometer). Splinted 3-unit fixed partial dentures were fabricated and cemented to the model. Changes in stress distribution under simulated non-loaded and loaded conditions(7.5, 15, 30 lb) were analyzed with a circular polaricope.
Results: 1. Stresses were distributed around the entire body of fin in Bicon implants. 2. Splinted restorations were useful for distribution of stress around implants especially with higher loads. 3. By increasing the contact tightness between the individually restored three implants, the stress increased in the coronal portion of implants.
ConclusionsS: Ideal adjustment of the contact tightness was important to reduce the stresses around individually restored Bicon implants.

03/20/04

Biomechanical Evaluation of a Wide Diameter Bicon Dental Implant in Various Bone Conditions

Bozkaya, D., Muftu, S. and Muftu, A., Poster abstract at the Academy of Osseointegration 19th Annual Meeting, March 18-20, 2004, San Francisco, CA

An association between higher implant failure rates and regions of poor bone density, commonly found in the posterior maxilla and mandible, has been reported in the literature. Moreover, implant placement in posterior regions is often limited by anatomic changes due to edentulism, where implant design alteration may be an alternative for treatment planning. In this regard, using a short implant with a large diameter in anatomically compromised regions may provide further increase in implant stability and long-term clinical success. The purpose of this study was to evaluate the biomechanical response of the bone for a wide and short implant, (WSI) (6 mm in diameter x 5.7 mm in length) versus a narrow and long implant (NLI) (3.5 mm x 11 mm) in various bone densities through finite element analyses (FEA). Both implants are using Bicon Morse-taper and made of Ti-6AL-4V. The implants and their respective bone domains were graphically designed through 3-D CAD software. After mesh refinement, different cortical to trabecular ratios and elastic moduli were assigned to the bone domain's elements to reproduce various bone conditions (Types II-IV). Vertical and horizontal loads were applied to the top of the Morse-taper connected abutments of the two implants. Implant and bone stress and strain states were evaluated numerically for analysis. The results showed that the implants presented comparable strain distributions under vertical loads and that the WSI presented lower strain values when the horizontal load was considered. The stress invariant values were also lower for the WSI implant. Increased stress and strain values were found at lower bone densities, where these values were higher for the NLI in most cases. According to the results obtained by this computer-based analysis, it can be concluded that the WSI implant presented an overall better biomechanical force distribution than the NLI when horizontal forces were applied for the different bone densities analyzed and may be considered for implantation of anatomically compromised regions and regions of poor bone quality.
03/10/04

Bacterial Adhesion on Integrated Abutment Crowns™. In Vivo Study (II)

M. MARINCOLA, S. DIBART, M.L. WARBINGTON, Z. SKOBE, R. URDANETA, and S.-K. CHUANG, University of Cartagena, AISI, Italian Association of Restorative Implant Dentistry, Rome, Italy, Boston University, MA, USA, Forsyth Institute, Boston, MA, Harvard University, Concord Dental Associates, Concord, MA, USA, Massachusetts General Hospital and Harvard School of Dental Medicine, Harvard School of Public Health, Chestnut Hill. IADR/AADR/CADR 80th General Session; Honolulu, HI

Objectives: The purpose of this study was to compare the subgingival microbiota present on implant supported Integrated Abutment Crowns (IAC) and natural teeth in vivo.

Material and Methods: A cross-sectional study design was utilized with patients selected from the patient pool at the Implant Dentistry Centre at Faulkner Hospital (Boston, MA). Thirty-one patients (13 males and 18 females) were selected, mean age 57.36 years (range 28.09 to 90.85 years) of which 4 were smokers. Selection requirements were: Patients had IAC crowns placed at least 6 months ago and had not taken antibiotics 3 months prior evaluation. Gingival index (GI), modified bleeding index (MBI), subgingival plaque samples and clinical photographs were taken on at least 1 IAC and the natural contralateral tooth on each patient. The subgingival plaque samples were taken from the mesial side of the IAC or natural teeth and put in an Eppendorf tube containing 0.150 ml Tris-EDTA. The samples were then hybridized with 12 whole chromosomal probes to Tannerella forsythensis, Prevotella intermedia, Campylobacter rectus, Fusobacterium nucleatum, Actinomyes odontolyticus, Streptococcus sanguis, Streptococcus intermedius, Actinobacillus actinomycetemcomitans serotype b, Actinomyces naeslundii, Streptococcus oralis, Porphyromonas gingivalis and Prevotella intermedia , using the checkerboard DNA-DNA hybridization method. The descriptive statistics and generalized linear mixed models (GLMM) accounted for intra-cluster correlation within the same patient were utilized using SAS-PC (version 8.2, 2001) Results: IAC were noted to have less GI and MBI compared with natural teeth but were not statistically significant (p>0.05). There were no statistical differences (p>0.05) in all the various colonies count between IAC and the natural teeth.

Conclusions: The IAC showed striking similarities with the natural tooth in terms of subgingival bacteria plaque count and composition. The IAC also showed lower GI and MBI indices.

Supported by a research grant from Bicon (MM, SD), OMSF Foundation Fellowship in Clinical Investigation (SKC).
03/10/04

Bacterial Adhesion on Integrated Abutment Crowns™. In Vitro Study (I)

S. DIBART, M. MARINCOLA, M.L. WARBINGTON, and Z. SKOBE, Boston University, MA, USA, University of Cartagena, AISI, Italian Association of Restorative Implant Dentistry, Rome, Italy, Forsyth Institute, Boston, MA. IADR/AADR/CADR 80th General Session; Honolulu, HI

Objectives: The goal of the present investigation was to determine if the DiamondCrown material, used to make Bicon's Integrated Abutment Crown (IAC), is less susceptible to harbor/attract bacterial plaque than All Ceramic (AC) or Metal Ceramic (MC) crowns. A secondary goal was to compare the composition of the plaque attracted on tested surfaces.

Methods: 6 IAC, 6 AC and 6 MC crowns were equally divided in 2 test groups. The AC and MC crowns were cemented on titanium abutments. Group I (3 IAC,3 AC, 3 MC) and group II were incubated for 10 min in a bacterial solution containing 10 different oral bacteria at O.D.1: Tanerella forsythensis, Prevotella intermedia, Campylobacter rectus, Fusobacterium nucleatum, Actinomyces odontololyticus, Streptococcus intermedius, Actinobacillus actinomycetemcomitans serotype b, Actinomyces naeslundii, Streptococcus oralis, Porphyromonas gingivalis. After a brief wash in PBS to eliminate the unbound plaque, the crown samples in group I were incubated in 500µl of Tris-EDTA buffer with 500µl of NaOH. The samples were then hybridized with 10 whole chromosomal probes to the above mentioned microorganisms. The microbiological analysis was completed using the checkerboard DNA-DNA hybridization method. The samples in group II were briefly washed in PBS and fixed in 4% formalin for scanning electron microscopy (SEM).

Results: All experimental crowns showed bacterial adhesion. There was no statistical difference in the microbial compositions when comparing crowns. The SEM showed that the AC crowns were harboring the heaviest bacterial deposits. MC and IAC showed the least bacterial deposits especially at the abutment/crown interface.

Conclusions: The IAC and MC crowns appear to be less prone to bacterial colonization, in an in vitro setting then an all ceramic crown. IAC and MC crowns harbored very few bacteria at the abutment/crown interface.

This study was supported by a research grant from Bicon.

03/10/04

Two-Year Retrospective Evaluation of a Unique Restoration for Single Implants

R. URDANETA, Harvard University, Concord Dental Associates, Concord, MA, USA, M. MARINCOLA, University of Cartagena, AISI, Italian Association of Restorative Implant Dentistry, Rome, Italy, and S.-K. CHUANG, Massachusetts General Hospital and Harvard School of Dental Medicine, Harvard School of Public Health, Chestnut Hill. IADR/AADR/CADR 80th General Session; Honolulu, HIIADR/AADR/CADR 80th General Session; Honolulu, HI

The Integrated Abutment Crown™ (IAC) (Bicon, Boston, MA) is a technique for the fabrication of single-tooth implant-supported restorations where the abutment and the crown material are one integral unit without the use of any screws or cement.

Objectives: The objective of this study was to examine the 2-year clinical performance of 151 IACs placed in a general dental practice.

Materials and Methods: A retrospective cohort study design was utilized with patients selected from the patient pool at the Implant Dentistry Centre at Faulkner Hospital (Boston, MA). Patients were recalled and the restorations were evaluated following the modified USPHS criteria. The gingival esthetics and the number of restorative appointments were documented. Descriptive statistics and generalized linear mixed models (GLMM) accounting for intra-cluster correlation within the same patient were utilized using SAS-PC (version 8.2, 2001).

Results: A total of 151 implants were restored with IACs on 59 patients, with a mean age of 58.2 years, 62% were placed in the maxilla and 38% placed in the mandible. The 2-year survival rate for IACs was 98.56%. Two IACs were removed, one due to implant failure; all others were rated as either excellent or good for anatomy, surface texture, and color. No IACs were removed due to fractures. Excellent marginal adaptation was observed with no clinically discernible interface between the veneer material and the abutment. Excellent gingival esthetics was observed. Significantly fewer appointments were needed to restore an IAC than a PFM (p<.0001).

Conclusion: The results of this prosthetic evaluation supported the conclusion that the Integrated Abutment Crown™ is an excellent choice for the restoration of locking-taper single implants for both anterior and posterior areas of the mouth. IACs are a cost-effective and timesaving alternative to PFMs.

Supported by Oral and Maxillofacial Surgery Foundation (OMSF) Fellowship in Clinical Investigation (SKC).

03/10/04

Biomechanical Assessment of an IBAD Surface-Modified Implant

P.G. COELHO, University of Alabama at Birmingham, Birmingam, USA, J. LEMONS, University of Alabama at Birmingham, USA, and A.W. EBERHARDT, University of Alabama at Birmingham, USA. IADR/AADR/CADR 80th General Session; Honolulu, HI

Attention has been given by implantology research groups regarding thin-film bioceramic coatings on dental implants due to the potential controlled coating dissolution/biological degradation after implantation and direct bone anchorage to the metallic substrate.

Objective: The purpose of this study was to evaluate the biological fixation of a thin-film ion beam assisted deposition (IBAD) surface-modified implant versus a non-surface-modified titanium alloy implant at early implantation times in-vivo in a laboratory canine model.

Methods: The implants were placed in the dogs’ tibiae and remained for 2 and 4 weeks in vivo. After euthanization, the limbs were retrieved and reduced to blocks containing the implant in its center. The blocks were mounted in epoxy resin and the implants were pulled-out at 0.5 in/min in a universal testing machine. Force versus displacement curves were recorded for the specimens, which were subsequently decalcified and prepared (H. and E. stain) for histomorphometric assessment of bone contact at the implant surface enabling interfacial shear stress calculations.

Results: The results showed that bone contact at the implant surface was significantly higher (P<0.03) for the non-surface-modified when compared to surface-modified implants for both times in vivo, and that the pullout forces were not statistically different among the four groups. ANOVA revealed that time in-vivo and surface treatment did not affect interfacial shear stress.

Conclusion: According to the histomorphometric and biomechanical results obtained in this study, it was concluded that there were no weak links between the thin-film coating and the metallic substrate. Furthermore, the bone around the surface-modified implants may have improved mechanical properties, which is a desirable feature for early and long-term implantation of load bearing devices. These results suggest that total dissolution/biological degradation of the coating may not be complete at these early implantation times.
03/10/04

Radial Implant-Abutment Gap Determination Through Serial-Sectioning Method

P.G. COELHO, University of Alabama at Birmingham, Birmingham, USA, M. SUZUKI, University of Alabama at Birmingham, USA, and A.L. COELHO, UNICENP, Curitiba, Brazil. IADR/AADR/CADR 80th General Session; Honolulu, HI

Significant attention has been devoted by the implantology and bioengineering research community regarding the implant-abutment gap, once such gap may provide a favorable environment for bacterial adhesion/proliferation and to degradation of the metallic substrate. Classically, this distance has been evaluated by means of scanning electron microscopy (SEM) along the implant perimeter and no information is revealed as a function of radius.

Objective: The purpose of this study was to evaluate the implant-abutment gap as a function of radius by means of optical microscopy evaluation through a sequential sectioning technique.

Methods: Six implants (3.75 mm in diameter) and abutments were screw connected and torqued to 20 N.cm. Outer radius measurements were recorded by SEM. The implants were then mounted in epoxy resin using a metallic fixture to assure implant position (perpendicular to the vertical axis). Subsequently, each implant was abraded and polished parallel to its long axis at six different distance intervals. Implant-abutment gaps were obtained by optical microscopy (1000X mag.) and these distances were related to its radial position through trigonometric inferences. A 6th degree polynomial best line fit approach was used to determine the radial adaptation patterns for each of the implants.

Results: The results showed that gap distances were not statistically different among the implants (P=0.05). The polynomial best line fit approach revealed that the implant-abutment gap distance increases as a function of implant radius and this increase is more pronounced in the outer 1⁄4 radius, at the abutment beveled region. Also, communication between external and internal regions of the implant were found for all specimens.

Conclusion: Based on these results, it was concluded that this methodology provided a broader scenario of the implant-abutment gap distance and that SEM evaluations may underestimate the gap value.
03/01/04

Use of Integrated Abutment Crowns to Enhance the Aesthetics of Maxillary Anterior Implant Restorations

Leary, J., Hirayama, M., AO General Session, San Francisco, CA, March 2004

Achieving excellent aesthetics with maxillary anterior implant restorations is challenging to even the most accomplished clinicians. Placing implants in the area of the mouth is not only a clinically demanding task but often involves unrealistic patient expectations.

The cases presented here utilize an Integrated Abutment CrownsTM(IAC), an innovative technique in implant prosthetics, to achieve aesthetic restorations in a narrow edentulous space. These cases also demonstrate a multi-disciplined approach solving the problem of esthetics in the maxillary anterior. Orthodontic tooth movement , periodontal plastic surgery, and immediate stabilization have been used to achieve the desired clinical results.

This presentation should add to our ability to enhance anterior aesthetics in even the most demanding situation.

03/01/04

Risk Factors with Radiographic Bone Loss in Dental Implants in a Five-Year Retrospecitve Cohort Study

Chuang, S.K., AO General Session, San Francisco, March 2004

Objectives: The purpose of this study was to examine the long-term follow-up (> 5 years) of radiographic evaluation of Bicon dental implants and the risk factors associated with radiographic bone loss beyond the first thread placed at the Implant Dentistry Center (IDC) in Boston, Massachusetts.

Materials and Methods: To address the research purpose, a retrospective cohort study design was used. The cohort was composed of patients who had at least one Bicon dental implant placed for 5 years and were willing to return to IDC for the 5 year follow-up radiographic examination of these originally placed implants. Risk factors were categorized as demographic, implant-specific and anatomic variables. The outcome variable as failure was bone loss beyond the first implant thread on either the mesial or the distal aspects of the implant. Risk factors for bone loss were identified using the generalized estimating equations (GEE) approach adjusted for clustered implant observations within the same patient.

Results: There were 50 patients with 117 implants with a mean age of 50.75 years (range: 17.61 to 82.84 years) of which 26 were females. There were 52 implants placed in the maxilla and 65 implants in the mandible. On the mesial side, 6 implants (5.13%) lost bone beyond the first thread over 5 years. On the distal side, 5 implants (4.27%) lost bone beyond the first thread over the five years. A total of 6 implants (5.13%) had lost bone beyond the first thread on at least the mesial or the distal aspect. Risk factors associated with bone loss beyond the first thread (p < 0.20) included age at implant placement, quality of bone, and implant length. Based on the adjusted multivariate GEE model including gender for biologic importance, risk factors associated with bone loss beyond the first thread was age at implant placement (odds ratio =1.14, p =0.04).

Conclusions: The results of this long-term follow-up radiographic study supported the fact that the Bicon dental implant system is an excellent choice for the prosthetic restoration of the locking-taper implant design. We identified one risk factor (age at implant placement) associated with bone loss beyond the first thread. This key factor is not under the direct control of the practitioner. Supported by Oral and Maxillofacial Surgery (OMSF) Fellowship in Clinical Investigation (SKC).

03/01/04

Immediate Stabilization and Functioning: Anterior Aesthetics

Leary, J., Hirayama, M., WCOI General Session, Honolulu, Hawaii, March 2004

The immediate stabilization and loading has become one of the more prominent topics in implant dentistry today. Clinical testing by clinicians, engineering improvements from manufacturers, and patient demand have allowed clinicians to reduce the osseointegration healing period from a conservative time of 6-9 months to period of 1-3 months. Many practitioners acknowledge and utilize the immediate stabilization and functioning: however, a majority of clinicians are still skeptical about such methods and techniques. This presentation shall show step by step methodology of totally chair-side technique of immediate stabilization and functioning with two year retrospective study.

In this retrospective clinical study, 477 fin-type implants (Hydroxyappatite coated, Titanium Plasma Spray, or Uncoated) in 208 patients during the periods from July 1, 2001 unlit July 31, 2003. All implants are immediately stabilized and functioned by fabrication of temporary prosthesis by bonding the prosthesis to remaining teeth or splinting one piece prosthesis for full arch cases.

Further to the normal principles of implant placement the immediate stabilization technique requires only one criterion. That is the ability to prosthetically immobilize the implant with a transitional stabilization prosthesis. Successful osseointegration is not dependent upon the density or quality of the bone to provide initial stability of the implant in its osteotomy. Implants placed immediately after an extraction or even a ridge split osteotomy are excellent candidates for the immediate stabilization or (immediate) loading technique. This technique is applicable for a single implant or for a full arch of implants.

With this new concept and fully chair-side technique shown in this presentation, a clinician can provide an immediately stabilized and immediately functioned prosthesis on the same day as implant placement giving the patient both function and aesthetics. Based upon these clinical evidence, the immediately stabilized and functioned implant technique is a viable treatment option that should be part of every implant practice.

03/01/04

Immediate Loading Implants for Overdentures

Speratti, D., AO General Session, San Francisco, CA, March 2004

The immediate loading of implants has become a prominent topic in implant dentistry lately. Engineering improvements from manufacturers and clinical testing have allowed clinicians to offer immediately loaded implants to a wider patient population. The application of this technique for over dentures is a rewarding treatment for both dentists and patients. Patients benefit from gaining immediate prosthetic stability in a cost effective manner and clinicians by being able to offer an efficient and predictable treatment that improves many patients quality of life.

03/01/04

Efficiency Considerations for the Purely Tapered Interference Fit (TIF) Abutments Used in Dental Implants

Bozkaya, D., Müftü, S. and Müftü, A., Journal of Biomechanical Engineering, Trans ASME

A tapered interference fit provides a mechanically reliable retention mechanism for the implant-abutment interface in a dental implant. Understanding the mechanical properties of the tapered interface with or without a screw at the bottom has been the subject of a considerable amount of studies involving experiments and finite element (FE) analysis. In this paper, approximate closed-form formulas are developed to analyze the mechanics of a tapered interference fit. In particular the insertion force, the efficiency, defined as the ratio of the pull-out force to insertion force, and the critical insertion depth, which causes the onset of plastic deformation, are analyzed. It is shown that the insertion force is a function of the taper angle, the contact length, the inner and outer radii of the implant, the static and the kinetic coefficients of friction, and the elastic modul of the implant/abutment materials. The efficiency of the tapered interference fit, which is defined as the ratio of the pull-out force to insertion force, is found to be greater than one, for taper angles that are less than 6o when the friction coefficient is 0.3. A safe range of insertion forces has been shown to exist. The lower end of this range depends on the maximum pull-out force that may occur due to occlusion in the multiple tooth restorations and the efficiency of the system; and the upper end of this range depends on the plastic deformation of the abutment and the implant due to interference fit. It has been shown that using a small taper angle and a long contact length widens the safe range of insertion forces.

11/01/03

Immediate Loaded implants: How clinicians can achieve aesthetic results

Hirayama, M., Wang, M., AAID General Session, Hollywood, FL, November 2003

The “immediate loading” technique has become a popular procedure in implant dentistry. Some practitioners use this method routinely while many remain skeptical about this treatment. The purpose of this study is to demonstrate that the immediate loading technique is a viable and practical treatment option.

Our clinical methodology of “immediate loading” and its concept will be explained in this presentation. Preservation of hard and soft tissue around the implant site is the most critical issue in aesthetic implant dentistry. Clinicians can utilize these methods for many types of cases while providing an immediate temporary restoration on same day implant placement.

11/01/03

Bone Levels around Immediately Loaded-Stabilized Vs. Conventionally loaded locking-taper implants

Hirayama, M., Urdaneta, R., AAID General Session, Hollywood, FL, November 2003

Synopsis: Once an implant is uncovered, vertical bone loss of 1.5-2.0mm is observed apically from the newly established implant-abutment interface. This has been well documented for screw-type implant abutment connections.

The purpose of this study was to evaluate bone loss around a locking taper implant-abutment connection interface in immediately loaded and conventionally loaded one and two stage implants. The following objectives will be discussed in this presentation as a retrospective analysis: factors affecting peri-implant tissue conditions; assessment of peri-implant bone levels around immediately loaded vs. conventionally loaded implants; remodeling of peri-implant bone after functional loading; and changes in crestal bone levels during the first year after functional loading.

Download PDF

11/01/03

Mechanics of the tapered interference fit in dental implants

D. Bozkaya and S. Müftü, Journal of Biomechanics, Vol. 36, No. 11, pp. 1649-1658

In evaluation of the long-term success of a dental implant, the reliability and the stability of the implant-abutment interface plays a great role. Tapered interference fits provide a reliable connection method between the abutment and the implant. In this work, the mechanics of the tapered interference fits were analyzed using a closed-form formula and the finite element (FE) method. An analytical solution, which is used to predict the contact pressure in a straight interference, was modified to predict the contact pressure in the tapered implant-abutment interface. Elastic-plastic FE analysis was used to simulate the implant and abutment material behavior. The validity and the applicability of the analytical solution were investigated by comparisons with the FE model for a range of problem parameters. It was shown that the analytical solution could be used to determine the pull-out force and loosening-torque with 5-10% error. Detailed analysis of the stress distribution due to tapered interference fit, in a commercially available, abutment-implant system was carried out. This analysis shows that plastic deformation in the implant limits the increase in the pull-out force that would have been otherwise predicted by higher interference values.

06/12/03

Determination of Bone Activity around a Surface-modified Titanium Alloy Implant

P.G. COELHO, University of Alabama at Birmingham, USA, and J. LEMONS, University of Alabama at Birmingham, USA. AADR/CADR Annual Meeting; San Antonio, TX

Objective: The purpose of this study was to evaluate the cortical and trabecular bone activity by means of tetracycline bone labeling of a surface-modified (IBAD) versus a non-surface-modified titanium alloy implant in a canine model.

Methods: Implants were surgically placed in the dogs tibiae and the model provided specimens that remained 2 and 4 weeks in vivo. Prior to euthanization, 10mg/Kg oxytetracycline was administered for bone labeling. The limbs were retrieved by sharp dissection, and non-decalcified thin sections containing the implant in their centers were prepared for microscopy evaluation under UV light. Bone activity determination (amount of tetracycline labels) was evaluated dividing the specimens in regions of interest along the length and away from the implant surface (to 2 mm) by quantitative microscopy techniques. Physiologic activity was obtained by tetracycline labeling assessment away (> 3 mm) from the implant surface and comprised the normalizing data.

Results: Results showed that the 4-week surface-modified implant had significantly higher (P = 0.05) amount of tetracycline labeling than other groups and demonstrated that there is significantly more labeling in regions of trabecular bone than in regions of cortical bone. Quantification of the amount labeled for the different regions of interest at different distances from the implant surface (to 2 mm) revealed that the only region that had significantly higher activity than physiologic levels was the region adjacent from the implant surface (to 0.5 mm) and the amount of labeling was significantly higher for the 4-week surface-modified group. Determination of bone activity gradients from the implant surface was performed by linear regression and presented negative slopes from the implant surface.

Conclusions: These results indicated that there is a time-dependent increased osteoconductivity for the surface-treated implants and that increased bone activity after implantation is restricted to the first 0.5 mm region adjacent from the implant surface.
03/12/03

6.0 x 5.7mm Implants: Survival Estimates and Risk Factors for Failure

M.A. GENTILE, S.-K. CHUANG, and T.B. DODSON, Harvard School of Dental Medicine, Boston, MA, USA, Massachusetts General Hospital and Harvard School of Dental Medicine, Boston, USA. AADR/CADR Annual Meeting; San Antonio, TX

Introduction: Short dental implants facilitate prosthetic restoration in the setting of limited alveolar bone height. Few data exists to support the clinical use of short implants. We hypothesize that 6x5.7 implants are a clinically acceptable option when indicated.

Objective: The study objectives are to: 1) estimate the one-year survival of Bicon 6x5.7 mm implants, 2) identify risk factors associated with 6x5.7 implant failure, and 3) compare the one-year survival of 6x5.7 implants with non-6x5.7 implants.

Methods: We used a retrospective cohort study design and a sample composed of patients having one 6x5.7 implant placed. Predictor variables were categorized as demographic, health status, anatomic, implant-specific, prosthetic, perioperative, and reconstructive. The outcome variable was implant failure defined as explantation. Kaplan-Meier estimates were used to assess implant survival. Appropriate bivariate and multivariate (Cox proportional hazards) survival statistics were computed.

Results: The sample was composed of 35 patients having 172 implants placed (45 6x5.7 and 127 non-6x5.7). The one-year survival of 6x5.7 and non-6x5.7 implants was 92.18% and 95.24%, respectively (p=0.78). Bivariate analyses identified staging and reconstruction as risk factors for failure. After adjusting for covariates in a multivariate model, a single-stage implant placement was found to be a statistically significant (p=0.047) risk factor for implant failure.

Conclusion: We believe this to be the first study reporting on clinical outcomes of the Bicon® 6x5.7 implant. The survival of 6x5.7 implants was comparable to that of non-6x5.7 implants. This data supports the hypothesis that 6x5.7 implants are a clinically acceptable option to facilitate prosthetic restoration in the setting of limited alveolar height. In addition, the results suggest that a two-stage approach is preferred when placing these implants.

Supported by the OMS Foundation Fellowship in Clinical Investigation (S-KC), NIH-NIDCR K24 DE00448 (TBD), MGH Department of OMS Research Fund (MAG).
03/12/03

Mixed-effects Frailty Failure Time Methods to Estimate Dental Implant Survival

M.A. GENTILE, S.-K. CHUANG, and T.B. DODSON, Harvard School of Dental Medicine, Boston, MA, USA, Massachusetts General Hospital and Harvard School of Dental Medicine, Boston, USA. AADR/CADR Annual Meeting; San Antonio, TX

Purpose: The purpose of this study was to identify covariate effects associated with implant failure by applying clustered semi-parametric Cox proportional hazards frailty survival methods. To our knowledge, this method has not been described or applied widely in the dental research literature.

Methods: To address the research purpose, we used a retrospective cohort study design. The cohort was composed of patients having one or more Bicon implant(s) placed. Covariates were categorized as demographic, health status, implant-specific, anatomic, prosthetic, perioperative, operative, and reconstructive variables. The outcome variable was implant failure (explantation). Covariates for implant failure were identified using the frailty survival methods adjusted for clustered failure-time observations.

Results: The sample was composed of 677 patients having 2349 implants placed. Covariates associated with implant failure (p < 0.15) included operating surgeon, tobacco use, peri-operative antibiotic use, implant position, implant length, well size, coating of implant, proximity of the implant to adjacent teeth or other implants, immediate implant placement, abutment diameter, prosthetic type, usage of reconstruction procedures, and implant staging. Based on the adjusted multivariate frailty model, covariates associated with implant failure were tobacco use, implant length and staging, proximity of the implant to adjacent teeth or other implants, and well size.

Conclusion: Datasets composed of clustered observations are commonly encountered in dental research. Survival analyses of such datasets are exceedingly challenging propositions. We presented an innovative Cox proportional hazards frailty survival methods with clinical applications to implants as an example. We identified five factors associated with implant failure. Three of these variables, smoking status, well size, and staging of implant placement are under the direct control of the practitioner.

Supported by Oral and Maxillofacial Surgery Research Foundation Fellowship in Clinical Investigation (S-KC), NIH grant K24 DE000448 (TBD) and MGH Department of OMS Research Fund (S-KC, TBD).
03/01/03

Immediate Loading and Stabilization: The Clinical Realities

Hirayama, M., and Wang, M., AO General Session, Boston, MA, March 2003

The immediate loading and stabilization has become one of the more prominent topics in implant dentistry today. Clinical testing by clinicians, engineering improvements from manufacturers, and patient demand have allowed clinicians to reduce the osseointegration healing period from a conservative time of 6-9 months to a period of 1-3 months. Many practitioners acknowledge and utilize the latest method of “immediate loading” or “immediate stabilization”; however, a majority of clinicians are still skeptical about such methods and techniques.

In this on going clinical observation and study, 168 fin-type implants (Hydroxyappatite Coated or Titanium Plasma Spray Coated) were placed in 98 patients during the period from November 1998 until September 2002. All implants were immediately loaded by fabrication of a temporary prosthesis by bonding the prosthesis to remaining teeth or splinting a one-piece prosthesis for a full arch case. During this period of time, two implants failed to osseointegrate and were subsequently replaced with new implants.

With this new concept and fully chair side technique shown in this presentation, a clinician can provide an immediately stabilized and immediately loaded prosthesis on the same day as implant placement giving the patient both function and aesthetics. Clinical realities with this on-going study will be shown as well as its methodology. Based upon the results of this on-going study, the immediately stabilized and loaded implant technique is a viable treatment option that should be part of every implant practice.

1. Aires I, Berger J. (2002). “Immediate placement in extraction sites followed by immediate loading; a pilot study and case presentation.” Implant Dent.; 11(1):87-94.
2. Cooper LF, Rahman A, Moriarty J, Chaffee N, Sacco D. (20) “Immediate mandibular rehabilitation with endosseous implants : simultaneous extraction, implant placement, and loading.” Int J Oral Maxillofac Implants. July-Aug;17(4):517-25

03/01/03

Dental implant complications: Types, frequency, and associated risk factors

N. MCDERMOTT, S.-K. CHUANG, V. VEHEMENTE, S. DAHER, A. MUFTU, and T.B. DODSON, Harvard School of Dental Medicine, USA, Boston University Goldman School of Dental Medicine, USA, Tufts University School of Dental Medicine, USA, Massachusetts General Hospital, USA. IADR/AADR/CADR 80th General Session; San Diego, CA

Objectives: The purpose of this study was to identify the type, frequency and factors associated with complications following placement of dental implants.

Materials and Methods: To address the research purpose, we used a retrospective cohort study design and a sample derived from patients having Bicon (Bicon, Boston, MA) implants placed at the Implant Dentistry Centre, Faulkner Hospital, Boston, MA between 1992 and 2000. The predictor variables were grouped into demographic, medical history, implant-specific, anatomic, prosthetic, and reconstructive categories. The complication variables were grouped into inflammatory, prosthetic or operative. For each patient, one implant was randomly selected for study inclusion. The Cox proportional hazards regression model was used to identify risk factors associated with implant complications.

Results: The sample was composed of 677 patients with a mean age of 53.5 +/- 13.9 years. The overall frequency of implant complications was 13.9% (10.2% inflammatory, 2.7% prosthetic, 1.0% operative). Most implants (62%) with complications did not fail during the study interval. Variables associated with complications (p < 0.15) were: 1) smoking, 2) prosthetic type 3) implant staging, and 4) use of reconstructive procedures. These four variables, gender and age (6 variables total) were included in the multivariate model. Multivariate Cox proportional hazards regression revealed smoking, implant staging, and use of reconstructive procedures to be statistically associated with implant complications (p < 0.05).Prosthetic type was borderline non-significant (p=0.08).

Conclusion: Factors associated with an increased risk for complications include smoking, implant staging, and use of reconstructive procedures.
03/01/03

Risk factors for dental implant failure: A strategy for the analysis of clustered failure time observations

S.-K. CHUANG, Harvard School of Dental Medicine, USA, L.-J. WEI, Harvard School of Public Health, USA, and T.B. DODSON, Massachusetts General Hospital, USA. IADR/AADR/CADR 80th General Session; San Diego, CA

Objectives: This study's objective was to identify risk factors associated with failure of dental implants by applying innovative, advanced semi-parametric survival methods that adjust for clustered failure-time observations.

Methods: To address the research objective, we used a retrospective cohort study design including all patients who had one or more implants placed at Implant Dentistry at the Faulkner Hospital, Boston, MA between 1992 and 2000. Risk factors for failure were grouped into the following categories: demographic, health status, implant-specific, anatomic, prosthetic, and reconstructive categories. The outcome variable was implant failure defined as explantation. Overall implant survival was adjusted for clustered failure-time observations. Risk factors for implant failure using a dependence model and applying a marginal approach of the Cox proportional hazard regression model.

Results: The sample was composed of 677 patients who had a total of 2349 implants placed. The overall Kaplan-Meier survival rates at one- and five-years were 95.46% and 90.91%, respectively. Univariate risk factors associated with failure (at p < 0.15) were smoking status, implant position, implant length, well size, coating of implant, proximity of the implant, immediate implant placement, abutment diameter, prosthetic type, and implant staging. Based on a multivariate model that adjusts for correlated observations, five factors were statistically associated with implant failures (p < 0.05): 1) smoking status, 2) implant length, 3) immediate implants, 4) implant staging, and 5) well size.

Conclusions: Managing the issue of clustered or correlated observations within the same subject is a common and challenging proposition in dental research. When selecting risk factors for inclusion in the Cox proportional hazard regression models, we recommend adjusting for dependence among dental implant observations within the same patient.

Supported by NIH grants: K16 DE000275 (SKC), R01 CA56844 (LJW), and K24 DE000448 (TBD).
03/01/03

Stress Distribution Characteristics of Various Implant Systems due to Non-central Occlusal Loads

Bozkaya, D., Müftü, S. and Müftü, A., Poster presentation abstract for the Academy of Osseointegration 18th Annual Meeting, February 27-March 1, 2003, Boston MA.

Long-term stability of the dental implants strongly depends on the stress distribution characteristics of the implant-bone interface. The occlusal and masticatory loads acting on the prosthesis are transferred to the implant by means of abutment and result in non uniform stress distribution in the bone. In order to maintain a healthy bone, stresses should be in the range of 1.4-5 MPa. Stresses outside this range have been reported to cause resorption of the bone tissue1. In this study, the stress distribution characteristics of five different implants from Bicon, Ankylos, Astra, ITI and Nobel Biocare subjected to an occlusal load located off the central axis are investigated. The dimensions of the implants were comparable in size; however the thread profiles were considerably different from each other. The 2-D axisymmetric finite element models were loaded by 100 N vertical, 20 N lateral forces and 100 N.mm moment, separately and then the results are superposed to combine the effect of these loads to obtain the stress distribution due to a 102 N occlusal load 1 mm offset to the symmetry axis. The Young’s modulus of the bone was varied between 1 GPa (soft trabecular bone) and 16 GPa (hard cortical bone) in order to be able to investigate the success of the implants in different bone densities. The Bicon and Ankylos implant systems seem to distribute the stresses more evenly when compared to Astra, ITI and Nobel Biocare implants in all bone densities. High localized stresses were found at the tip of the Astra, ITI and Nobel Biocare implants that can lead to crestal bone loss, however stresses generated at the other sites of implant-bone interface were low enough to prevent bone resorption. 1. Rieger M. R, Mayberry M, Brose M. O. Finite element analysis of six endosseous implants. J Prosthet Dent. 1990;63:671-6

03/01/03

Implant-Supported Overdenture Surgery in the Severely Resorbed Edentulous Mandible: A Clinical Report

Wang, M.Y. & Hirayama, M., AO General Session, Boston, MA, March 2003.

Implant-supported overdentures are an effective means for restoring the resorbed mandible or maxilla. However, restoring the severely resorbed edentulous mandible with implants presents challenges for both the clinician and laboratory technician. A step-by-step surgical procedure for restoring the resorbed mandible with one implant system will be presented. A comparison of this procedure will be made to the treatment of the same patient using other implant systems.
1. Banton, B. and M.D. Henry (1997). “Overdenture stabilization with ball-and socket attachments: principles and technique.” J Dent Technol 14(7): 14-20
2. Visser, A., M.E. Geertman, et al. (2002). “Five years of aftercare of implant-retained mandibular overdentures and conventional dentures.” J Oral Rehabil 29(2): 113-20
3. von Wowern, N. and K. Gotfredsen (2001). “Implant-supported overdentures, a prevention of bone loss in edentulous mandibles? A 5-year follow-up study.” Clin Oral Implants Res 12(1): 19-25

03/01/03

Tapered Connection Mechanisms in Dental Implants

Bozkaya, D., Müftü, S., Poster presentation abstract for the Academy of Osseointegration 18th Annual Meeting, February 27-March 1, 2003, Boston MA.

One of the critical factors determining the success of a dental implant is the stability and the reliability of the implant-abutment connection. In-screw type implant-abutment connection mechanism is widely used in various implant systems; but high incidences of mechanical complications such as screw loosening, or creep deformation in the screw-implant interface are reported1. Tapered interference fits provide an alternative, reliable connection method2. The pull-out force and the loosening torque are the main design considerations to secure a reliable implant-abutment connection. In this work, the mechanics of the tapered interference fits was analyzed using finite element analysis (FEA). A closed-form analytical solution was also sought to determine the contact pressure distribution in the contact region. The validity of the analytical solution was investigated by comparisons with the FEA for different design parameters. The pull-out force and the loosening torque of the implant-abutment system were determined for different insertion depths. The quality and the quantity of the bone surrounding the implant did not have an effect more than 10%. The elastic-plastic FEA showed that the plastic deformation of the implant limits the increase in the pull-out force. This implies that larger insertion depth does not always mean more pull-out force, or a more secure connection. The pull-out force and the loosening torque of the implant-abutment system was large enough to prevent the long-term abutment loosening. 1. Schwarz. Mechanical Complications of Dental Implants. Clin. Oral Impl. Res. 2000;11:156-158. 2. Müftü A, Chapman R. J. Replacing posterior teeth with freestanding implants: Four-year prosthodontic results of a prospective study. Journal of the American Dental Association 1998;129(8):1097-1102.

10/01/02

Immediate Restorations in Clinical Realities

Hirayama, M., AAID General Session, Los Angles, CA, October 2002

Immediate loading has become one of the latest trends in Implant Dentistry, due to engineering improvements, modified clinical techniques, and clinical necessities. Osseointegration time allowances have drained from 6-9 months to 4-6 months, and yet again to 1-3 months, while restoration/loading time allowances of the implant have decreased to immediate 2 weeks. This study presents successful clinical immediate restoration cases on a two component fin-type dental implant, including methodology.

10/01/02

The New Generation In Aesthetic Dentistry: Extra-Oral Cementation & Integrated Abutment Crown™

Hirayama, M., Marincola, M., Wang, M., AAID General Session, Los Angles, CA, October 2002

With the flexibility of the Bicon Dental Implant System, the common problems associated with traditional screw and cement retained restorations can be eliminated. By using extraoral cementation you avoid the problems of excess sub-gingival cement. With the advent of DiamondCrown™, by DRM Research Laboratories, Inc., this new poly-ceramic material will create a strong and flexible Integrated Abutment Crown™ without the use of screws or cement. This new restorative concept will provide a superior aesthetic result, while reducing occlusal stress on the dental implant.

03/01/02

Integrated Abutment Crown with Poly-Ceramic Material

Wang, M.Y., Hinman General Session, Georgia, March 2002

Traditionally, there are screw-retained or cement-retained restorations for implant prostheses. These techniques are well known to clinicians. Screw-retained attachments can lead to screw loosening caused by occlusal forces and cement-retained restorations can lead to problems because of excess cement around the subgingival margin. Both of these problems can lead to a significant loss of time and expense for the dentist. A product has recently been introduced which enables a dentist to build the crown directly onto an implant abutment in the laboratory, and subsequently tap the abutment and crown as a unit into the implant well. This technique eliminates the problems of screw-loosening and excess cement subgingivally. This table clinic shows the step-by-step technique of the Integrated Abutment Crown.

03/01/01

Bone Morphology Associated with Biologic Width Among Various Dental Implant Designs

Hirayama, M., and Wang, M., AO General Session, Toronto, Canada, March 2001

The design of a dental implant can affect the clinical results of implant treatment. While all designs can achieve a certain level of success, there are specific engineering designs that do not experience the same problems and issues as others. Three problems commonly cited with dental implants are: (1) bone integration levels (2) biological width surrounding implants and (3) the complexity of restorative components. This study compares different implant systems in their bony architectures through various surgical stages. Different implant designs affect the bony morphology differently. These differences can lead to differences in integration strength and the biological width. We found that, in general, one-stage implants and one fin-type implant preserve bone better than the two-stage screw-type implants. A comparison of several dental implant designs and their clinical results is presented here.

03/19/97

Comparison of Ss Penetration Through Various Implant-Abutment Connection Mechanisms

Muftu, A., Chapman, R.J., and Mulcahy, H.L., IADR Orlando, Tufts University School of Dental Medicine & Suffolk University Department of Biology, Boston, MA., March 1997

Bacterial penetration through implant fixture-abutment interface (FA) may vary with the type of the connection mechanism. There appears to be significantly less bacterial penetration with the lock-and-taper mechanism than with most screw type mechanisms. However, design of screw systems differ with implant systems. The objective of this study was to determine whether a difference in microbial penetration exists in: 1) two different FA designs: (i) - lock-and-taper mechanism and (ii) - screw type mechanism and 2) within various screw mechanisms. After determining internal volume of all fixtures, FA-assemblies were attached according to manufacturer’s specifications and autoclaved. The, FA assemblies were immersed in a liquid medium exhibiting heavy growth of Streptococcus sanguis (ATCC 10566) and incubated at 35˚C. After 7 days , samples were rinsed with 25 ml of ultrafiltered, sterile H2O twice. Prior to disassembly, external surfaces were dried with sterile gauze to prevent contamination by the remaining medium along the FA interface. Under aseptic conditions, abutments were removed and, using a 26 G 3/8 in. needle attached to P100 Pipetman micropipering device, the inner parts of fixtures were filled with sterile saline respectively. This suspension was aspirated with the same instrument and inoculated into trypticase soy broth.

Implant

# Tested

# Showed Ss growth

Implant

# Tested

# Showed Ss growth

Bicon

10

0

IMZ (4.0mm Ø)

7

2

Brenemark

11

4

Minimatic

8

2

IMZ (3.3mm Ø)

9

3I

7

0


Statistical differences using Student’s t-test between the implant systems were: Bicon vs. Branemark p<.01; Bicon vs. IMZ (3.3 mm Ø) p<.000; Branemark vs. IMZ (3.3 mm Ø) p<.03; IMZ (3.3 mm Ø) p<.008); Minimatic vs. IMZ (3.3 mm Ø) p<.003; 3I vs. Branemark p<.03; 3I vs. IMZ (3.3 mm Ø) p<.000. Locking taper abutment connectors and one thread design abutment connector appear to resist bacterial penetration in vitro.

 

03/01/96

Comparison of Microbial Penetration Between Components of Screw and Locking Taper Implant-Abutment Connections

Muftu, A., Chapman, R.J., & Mulcahy, H.L., IADR San Francisco, Tufts University School of Dental Medicine & Suffolk University Department of Biology, Boston, MA., March 1996

It has been suggested that the seal between implant fixtures and abutments is not hermetic. There is a potential reservoir for bacterial flux which might play a role in peri-implantitis and/or the outcome of guided tissue regeneration after peri-implantitis. The objective of this study was to determine whether a difference in microbial penetration exists in two different implant fixture-abutment (FA) designs: 1) lock-and-taper mechanism and 2) screw type mechanism. Ten Bicon and 7 Branemark FA assemblies were attached according to manufacturer's specifications and autoclaved. Then, FA assemblies were immersed into a liquid medium that was previously inoculated with Streptococcus sanguis (ATCC 10556) and incubated at 35°C. After 70 hours, samples were rinsed with 25 ml of ultrafiltrated, sterile H2O twice. Prior to disassembly, external surfaces were dried with sterile gauze to prevent contamination by the remaining medium along the FA interface. Under aseptic conditions, abutments were removed and, using a 26G 3/8 needle attached to P100 Pipetman micropipeting device, the inner parts of Bicon and Branemark fixtures were filled with 5 microliters and 15 microliters of sterile saline, respectively. This suspension was aspirated with the same instrument and inoculated into trypticase soy broth. After 42 hrs, 1 out of 10 Bicon and 4 out of 7 Branemark implants showed growth while none of the sterility controls were contaminated. In this study, there appears to be significantly less bacterial penetration with the lock and taper mechanism than with the screw-type mechanisms. (Student's t-test p<0.05). The size of the spaces in the locking taper mechanism may prevent or reduce bacterial downgrowth.

03/01/94

Tissue Interfaces for Titanium Alloy Plateau Implants

Mitchell, S., Lemons, J., & Wellons, H., March 1994 IADR General Session and Exhibition, Seattle, Washington, University of Alabama and Stryker Dental Implants, Kalamazoo, MI.

Previous studies have demonstrated that integrated calcium phosphate ceramic (CPC) coated plateau design root-form implants have a unique distribution and orientation of mineralized phases associated with a vasculature that was specific to the plateau design.1 This study focused on three non-coated Ti alloy plateau implants to determine if similar anatomical characteristics existed. The three specimens consisted of transmitted and reflected light microscopy and contact microradiography. The overall orientation of bone and vasculature was similar to the CPC coated implants (i.e., oriented haversian bone with mid-central positioned vascular channels relative to the plateaus), while the distribution of mature bone was greatest along the apical portions of the implants. A thin layer of non-calcified material was observed between the alloy and bone of one specimen. There was no evidence of inflammation present in any of the specimens. These analyses support previous results and showed that the distribution and orientation of bone integrated with CPC coated and non-coated Ti alloy plateau implants are similar. The bone anatomy for the plateau design is uniquely different compared to screw or rod (bullet) designed root-form dental implants. The importance of this difference related to load bearing capabilities and stability are unknown at this time and will be the subject of extended research.

This study was supported by Stryker Instruments.
1 Mitchell, S.C., Lemons, J.E., Wellons, H, Tissue Interfaces for HA Coasted Dental Implants. Abstract, IADR/AADR General Session and Exhibition, Chicago, March 1993.