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[Bioresorbable barrier membranes for guided bone regeneration around dental implants].

The aim of this study was to evaluate the efficacy of two bioresorbable barriers especially produced for guided bone regeneration. Six beagle dogs were used in this investigation. At the beginning of the study, all mandibular premolars were extracted and after a healing period of three months three screw-type machined implants were inserted in each side of the mandible. At the buccal aspect of each implant bed a dehiscence type defect with a coronoapical and mesiodistal extension of 5 mm was created. Then, one of the following four methods for defect treatment was applied: 1) guided bone regeneration (GBR) with a bioresorbable barrier (poly-L/DL-lactide) (test group 1), 2) GBR with a bioresorbable composite barrier [poly-L/DL-lactide reinforced with tricalciumphosphate (TCP)] (test group 2), 3) GBR with an expanded polytetrafluoroethylene barrier (GTAM) (control group 1), and 4) no treatment (control group 2). The animals were sacrificed six months after implant installation. During the healing period the most common problems encountered in the test groups 1 and 2 were soft tissue dehiscences and bioresorbable membrane exposures. Retrieved tissue specimens were processed for histological and histometric evaluation. The mean amount of vertical bone regeneration at the defect areas was 1.75 mm for test group 1, 1.82 mm for the test group 2, 2.38 mm for control group 1, and 1.93 mm for control group 2. When the amount of bone regeneration in contact to the implant surface was evaluated, the regeneration result was 1.45 mm for test group 1, 1.49 mm for test group 2, 2.08 mm for control group 1, and 0.91 mm for control group 2. For both measurements, no statistically significant differences could be observed between the different groups. The present animal experiment showed that the treatment of dehiscence type defects around machined implants with the two bioresorbable barriers showed only slightly superior results compared to the treatment without barriers (control group 2). The best results--although not statistically significant different from the other treatment groups--were obtained when nonresorbable barriers were used.

Absorbable Implants↗

Functional behaviour of bone around dental implants.

Achieving a long-term stable implant interface is a significant clinical issue when there is insufficient cortical bone stabilisation at implant placement. Clinical outcomes studies suggest that the higher risk implants are those placed in compromised cortical bone (thin, porous, etc.) in anatomical sites with minimal existing trabecular bone (characterised as type IV bone). In establishing and maintaining an implant interface in such an environment, one needs to consider the impact of masticatory forces, the response of bone to these forces and the impact of age on the adaptive capacity of bone. These forces, in turn, have the potential to create localised changes in interfacial stiffness through viscoelastic changes at the interface. Changes in bone as a function of age (e.g. localised hypermineralised osteopetrosis and localised areas of osteopenia) will alter the communication between osteocytes and osteoblasts creating the potential for differences in response of osteoblastic cells in the older population. A key to understanding the biomechanical and functional behaviour of implants in the older population is to control the anticipated modelling and remodelling behaviour through implant design that takes into account how tissues respond to the mechanically active environment.

Aged↗

[Criteria for determining clinical success with osseointegrated dental implants].

In the past decade, the technique of osseointegration has elicited three general responses in the dental profession. The first and major response has been an enormous clinical satisfaction to resolve difficult prosthetic problems, as well to expand the scope and range of routing prosthetic therapy. A second, if minor, response has been an attempt to deny the documented apparent superiority of the osseointegrated method. The third response has been a very active marketing one, which led to the rapid proliferation of a large number of implant systems, all claiming osseointegration and comparable success to the originally introduced Swedish system. The purpose of this paper is to describe and analyze those clinical criteria which can be used by dentist and researcher to determine the long term success or failure of functioning dental implants. Some attempts had been made to identify criteria which reflected sound scientific consideration of long term host acceptance of functioning implants. However, these criteria where a reflection of the state of the art information as perceived by the authors at the time. It is therefore fair to add that the principle of osseointegration did not feature in our colleagues recommendations. Since it is an axiom that host response must be analyzed and understood if a clinical technique is to be successfully prescribed, we regarded our own and other's published data on clinical results with osseointegration as pivotal in the grouping of criteria which would comprise a reliable yardstick, easy to identify and apply, and which reflected assessment experiences in dental practice and research, mainly in the disciplines of periodontics and prosthodontics.(ABSTRACT TRUNCATED AT 400 WORDS)

Dental Implantation, Endosseous↗

Biomimetic calcium phosphate composite coating of dental implants.

PURPOSE: The aim of the present study was to test the hypothesis that calcium phosphate coating of titanium screw-type implants enhances peri-implant bone formation in the jaw. MATERIALS AND METHODS: Ten adult female foxhounds received experimental titanium screw-type implants in the mandible 3 months after removal of all premolar teeth. Four types of implants were evaluated in each animal: implants with machined titanium surface (the control group), implants coated with collagen I (the collagen-only group), implants with a composite coating of calcium phosphate and mineralized collagen I (the composite group), and implants with calcium phosphate (hydroxyapatite [HA]) coating (the HA-only group). Peri-implant bone regeneration was assessed histomorphometrically after 1 and 3 months in 5 dogs each by measuring bone-implant contact (BIC) and the volume density of the newly formed peri-implant bone (BVD). RESULTS: After 1 month, BIC was significantly enhanced only in the group of implants with composite coating of calcium phosphate and mineralized collagen (P = .038). Volume density of the newly formed peri-implant bone was significantly higher in all coated implants after 1 month. No significant difference from baseline was found in BIC for the collagen-only and HA-only groups, but BVD was significantly higher in implants with composite coating (P = .041). After 3 months, BIC and BVD were significantly higher in all coated implants than in the controls with machined surfaces. CONCLUSION: It was concluded that composite coating of dental screw-type implant surfaces using calcium phosphate and collagen can enhance BIC and peri-implant bone formation.

Animals↗

Reconstruction of maxillary alveolar defects with mandibular symphysis grafts for dental implants: a preliminary procedural report.

Partially edentulous patients with alveolar defects contraindicating implant placement were treated with bone grafts obtained from the mandibular symphysis. Complications encountered were minor and uneventful. Evaluation 4 months after surgery revealed minimal graft resorption, thus implant placement was possible in all potential sites. Advantages of the symphysis graft include easy access, availability of greater quantities of bone over other intraoral donor sites, low morbidity, no hospitalization, minimal discomfort, no alteration in ambulation, and no cutaneous scar. Compared with other bone regenerative methods for implant placement, a superior quality of bone was found and a shorter healing period is required. Results of this preliminary clinical investigation demonstrate that chin grafts offer a viable alternative for reconstruction of alveolar defects prior to dental implant placement.

Alveolar Bone Loss↗

Alveolar distraction before insertion of dental implants in the posterior mandible.

We investigated the efficacy of alveolar distraction for reducing crown height:implant length ratio in the posterior mandible. Ten alveolar distractions were done in seven patients. The pre-distraction ratio of required crown height to bone height available for implantation was in all cases > or =1. Two implants were placed in each distracted area (total 20 implants). Before distraction, the mean (SD) predicted crown height was 12.8 (2.1) mm; mean bone height available for implantation was 7.8 (1.5) mm. After distraction and insertion of implants, mean crown height was 8.1 (1.9) mm, and mean implant length was 11.3 (1.9) mm. Before distraction, the mean required crown height:available bone height ratio was 1.7 (0.3); after distraction and insertion of implants, the mean crown:implant ratio was 0.7 (0.2) (P<0.0005). Alveolar distraction is effective for increasing the height of the alveolar ridge in the posterior mandibular region, and should be considered when the height of the predicted crown that is required is greater than or equal to the maximum height of bone available for implantation.

Adult↗

Tissue reactions to some dental implant materials. An in vivo study in white rats.

In a 10 week experimental investigation the tissue reactions to implantation of standardised test pieces made of a polysilicone, Silastic, Tantalum, Titanium and a cobalt-chromium alloy, Vitallium, were studied in the white rat. After 2 weeks, polysilicone, Tantalum and Titanium caused slight reactions whilst a comparatively strong round cell infiltration was observed around the cobalt-chromium test pieces. After 10 weeks, no cellular infiltration was demonstrable around any of the implant materials. The now all appeared inert and were surrounded by a tough connective tissue.

Animals↗

Characterization of Actinomyces species isolated from failed dental implant fixtures.

In the oral cavity, Actinomyces form a fundamental component of the indigenous microflora, being among initial colonizers in polymicrobial biofilms. However, some differences may exist between different species in terms of their attachment not only to teeth but also to biomaterials. In this study we investigated the distribution of Actinomyces in 33 dental implant fixtures explanted from 17 patients. The identification was based on comprehensive biochemical testing and gas-liquid chromatography and when needed, 16S rRNA sequencing. Actinomyces was the most prevalent bacterial genus in these failed implants, colonizing 31/33 (94%) of the fixtures. Proportions of Actinomyces growth of the total bacterial growth in the Actinomyces-positive fixtures varied from 0.01% up to 75%. A. odontolyticus was the most common Actinomyces finding, present in 26/31 (84%) Actinomyces-positive fixtures. Actinomyces naeslundii and A. viscosus were both detected in 10/31 (32%) and A. israelii in 7/31 (23%) fixtures. Other Actinomyces species, including A. georgiae, A. gerencseriae and A. graevenitzii, were detected less frequently. Our results suggest that Actinomyces species are frequent colonizers on failed implant surfaces, where A. odontolyticus was the far most prominent Actinomyces species.

Journal Article↗

Evaluation of alveolar ridge bend and length in upper and lower jaws in anthropological skulls for planning of a series of endosseous dental implants.

The alveolar ridge bend and length were measured in the interforaminal part of the upper and lower jaws in 338 anthropological skulls. Interforaminal sections were determined by projection of the most medial points of the two foramina infraorbitale and foramina mentale at right angles to the alveolar ridge bends. Interforaminal arch lengths and radii of the circles that best fit the arches were analyzed with the use of celluloid transparencies. The differences between female and male group samples and the left and right sides were established. The data were processed by computer and were used for the development of a series of endosseous dental implants to satisfy various anatomical conditions.

Alveolar Process↗

Comparative surface analysis of four dental implant systems.

Surface analysis of similar titanium screw implants from four manufacturers (Brånemark System, 3i, Impla-Med and Restore) showed considerable differences in the composition of the surface oxides. Brånemark System implants had a markedly higher surface content of the natural oxide forming elements: titanium and oxygen. These implants also had a lower content of all contaminants (except boron) and significantly less variation in composition between different samples and points of analyses.

Dental Alloys↗

The longitudinal clinical effectiveness of osseointegrated dental implants: the Toronto study. Part I: Surgical results.

In this prospective study, 46 edentulous patients who had undergone traditional denture optimization therapy without success were treated with osseointegrated implants according to the surgical protocol described by Dr. P.I. Branemark. Two hundred seventy-four implants were placed in 49 dental arches--43 mandibles and six maxillae. At the time of writing, 4 to 9 years after insertion of the implants, 244 or 89.05% remained osseointegrated. Of the 262 implants in place more than 5 years, 232 or 88.55% were still integrated. The implant success criteria developed in this clinical study endorsed the predictably favorable outcome of the Branemark technique.

Adult↗

Evaluation of an experimental periodontal ligament for dental implants.

To improve the devices used in dental implantology, a new experimental supporting element has been developed. The device, made of titanium, poly(methylmethacrylate) and Dacron tissue, has been tested for the osteointegrability of its outer Dacron coat by implants in mandibular bone of rabbits. The Dacron filamentous tissue became incorporated by the bone at 3 month post-implantation. This might provide a reliable mechanical anchorage of the device and a barrier against epithelial proliferation and microbial contamination. Preliminary results relating to in vitro evaluation of the poly(methyl methacrylate)-Dacron fixation strength predict favourable mechanical behaviour at this interface and in the complete implanted device.

Animals↗

Coated versus non-Proplast-coated endosseous blade-vent dental implants.

In order to determine the efficacy of applying Proplast to dental endosseous bladevent implants, this material was coated on half of sixteen such implants which were bilaterally placed in the mandibles of eight rhesus monkeys. No difference in the clinical acceptability could be ascertained between the two groups. Histologic examination revealed a loose connective tissue layer around the noncoated implants which was not evident around the coated ones.

Alveolar Process↗

[A therapeutic approach using dental implants in an irradiated area. The experiences of the René Huguenin Center].

A therapeutic trial was conducted with six patients who were in remission after cancer therapy for at least two years. Twenty-four implants were performed in irradiated maxillary bone after local and general paraimplantation preparation using adjuvant hyperbaric oxygenotherapy. All implants integrated the bone within a minimal delay of nine months. All patients were fitted with a removable dental prosthesis which was anchored magnetically or with implant conjunction bars. Despite the limited number of implants and the short observation period, the results have been promising, in agreement with previous reports. These findings emphasize the importance of adjuvant hyperbaric oxygenotherapy and the need for good conditions in paraimplantation tissue. Although this technique demonstrates that dental implantation in irradiated tissue is possible, the risk of secondary failure has not been determined. In strictly selected cancer patients with reasonably healthy irradiated tissue, implantation can be proposed by a fully multidisciplinary team of specialists.

Aged↗

Clinical evaluation of two-piece apatite dental implants in 189 cases.

A two-piece apatite implant composed of a titanium abutment and a titanium tubular root portion cemented to an outer dense hydroxyapatite (D-HAP) tubular shell by resin cement has been authorized as High Advanced Medical Technology (H.M.A.T.) and applied since December 1987. We will show the success rate and the evaluation of the implants applied through May 1992. A successful implant was considered as one that provides functional comfort with no mobility and the absence of surrounding mucosal inflammation. The number of implants applied during the last 4.5 years was 810 pieces in 189 cases with an overall success rate of 92.5% for the 704 implants with abutment. The extirpation rate has no clear linear association with the duration of the implant or with the patient's age. Most of the extirpations resulted from cases where the patient used a provisional denture during the bone healing period, the time between implantation and abutment cementation. Extirpation rate of implant was high in cases using large maxillary provisional dentures with ten or more missing teeth. It is believed that all implant cases in which large dentures were used frequently contributed to the extirpation. These observations led us to suggest that provisional dentures may be harmful to the implant. When we shifted from the traditional method to the Delay Method 2.5 years ago, no incidence of extirpation was experienced in the mandible, even with the use of provisional dentures. In the maxilla, the Delay Method proved to be effective without the provisional denture. However, the results of the Delay Method with provisional dentures remains to be evaluated. The reason is that too few cases were encountered with large missing teeth to suffice for our observation. This Delay Method (named by us) consists of delaying the insertion of the implant for approximately 2 months after the first socket preparation, until the bone tissue activity has risen. After some adjustment in the prepared socket, the implant is then inserted during the second surgical procedure. We therefore consider this method of potential benefit over the traditional method.

Aged↗

Dosimetric measurement of scattered radiation from dental implants in simulated head and neck radiotherapy.

The purpose of this study was to examine the dose enhancement at bone-implant interfaces from scattered radiation during simulated head and neck radiotherapy. Three cylindric implant systems with different compositions (pure titanium, titanium-aluminum-vanadium alloy, titanium coated with hydroxyapatite) and a high gold content transmandibular implant system (gold-copper-silver alloy) were studied. Extruded lithium fluoride single crystal chips were used as thermoluminescent material to measure radiation dose enhancement at 0, 1, and 2 mm from the bone-implant interface. The relative doses in buccal, lingual, mesial, and distal directions were also recorded and compared. The results indicated that the highest dose enhancement occurred at a distance of 0 mm from the bone-implant interface for all the implant systems studied. The transmandibular implants had higher scattered radiation than other groups at 0 mm and at 1 mm from the bone-implant interface. There was no significant difference of dose enhancement between buccal, lingual, mesial, and distal directions. Titanium implants coated with hydroxyapatite demonstrated the best results under the simulated irradiation.

Alloys↗

Prosthodontic complications in osseointegrated dental implant treatment.

Complications were recorded in consecutive patients with osseointegrated implant-supported prostheses visiting prosthodontic specialist clinics during October and November 1991. Patients at regular follow-ups and emergency visits were included. Of the 600 prostheses examined, 28% needed some prosthodontic treatment. Complications varied widely--from simple adjustment to complete remaking of the prosthesis. The most common complications observed were related to the acrylic resin part of the prostheses. The frequency was higher in maxillary than in mandibular prostheses, and in full-arch removable and fixed prostheses than in single-tooth replacements and fixed partial dentures. Implant losses were rare (0.3% of all 2,709 implants placed) and occurred in 1% of the patients examined.

Adolescent↗