989 resultados para Bone implants


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OBJECTIVE: A novel biphasic calcium phosphate (CaP) granulate consisting of hydroxyapatite (HA) and beta-tricalciumphosphate (TCP) was compared with pure HA and pure TCP and with autograft as positive control. MATERIALS AND METHODS: Four standardized bone defects were prepared in both mandibular angles of 16 minipigs and grafted with autogenous bone chips, HA, HA/TCP (60% : 40%), or TCP. Histologic and histomorphometric analysis of bone formation and graft degradation followed healing periods of 2, 4, 8, and 24 weeks. RESULTS: 2 weeks: more bone formation in defects filled with autograft than with the three CaP materials (P<0.05). 4 weeks: bone formation differed significantly (P<0.05) between all four materials (autograft>TCP>HA/TCP>HA). 8 weeks: more bone formation in defects with autograft and TCP than with HA/TCP (P<0.05), and HA/TCP had more bone formation than HA (P<0.05). 24 weeks: no difference in bone formation between the groups. Autograft and TCP resorbed quickly and almost completely over 8 weeks, whereas HA/TCP and HA showed limited degradation over 24 weeks. CONCLUSION: All defects healed with mature lamellar bone and intimate contact between bone and the remaining graft material. The rate of bone formation corresponded to the content of TCP in the CaP materials.

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INTRODUCTION: Autogenous bone is the most successful bone-grafting material; however, multiple disadvantages continue to drive developments of improved methods for bone regeneration. AIM: The aim of the present study was to test the hypothesis that an arginine-glycine-aspartic acid (RGD) modified polyethylene glycol-based matrix (PEG) containing covalently bound peptides of the parathyroid hormone (PTH(1-34)) enhances bone regeneration to a degree similar to autogenous bone. MATERIAL AND METHODS: Six American foxhounds received a total of 48 cylindrical titanium implants placed in the mandible between the first premolar and the second molar. Five, respectively, 7 months following tooth extraction, implants were placed into the center of surgically created defects. This resulted in a circumferential bone defect simulating an alveolar defect with a circular gap of 1.5 mm. Four treatment modalities were randomly allocated to the four defects per side: (1) PEG-matrix containing 20 microg/ml of PTH(1-34), and 350 microg/ml cys-RGD peptide, (2) PEG alone, (3) autogenous bone and (4) empty defects. Histomorphometric analysis was performed 4 and 12 weeks after implantation. The area fraction of newly formed bone was determined within the former defect and the degree of bone-to-implant contact (BIC) was evaluated both in the defect region and in the apical region of the implant. For statistical analysis ANOVA and subsequent pairwise Student's t-test were applied. RESULTS: Healing was uneventful and all implants were histologically integrated. Histomorphometric analysis after 4 weeks showed an average area fraction of newly formed bone of 41.7+/-1.8% for matrix-PTH, 26.6+/-4.1% for PEG alone, 43.9+/-4.5% for autogenous bone, and 28.9+/-1.5% for empty defects. After 12 weeks, the respective values were 49.4+/-7.0% for matrix-PTH, 39.3+/-5.7% for PEG alone, 50.5+/-3.4% for autogenous bone and 38.7+/-1.9% for empty defects. Statistical analysis after 4 and 12 weeks revealed significantly more newly formed bone in the PTH(1-34) group compared with PEG alone or empty defects, whereas no difference could be detected against autogenous bone. Regarding BIC no significant difference was observed between the four treatment groups neither at 4 nor at 12 weeks. CONCLUSION: It is concluded that an RGD-modified PEG hydrogel containing PTH(1-34) is an effective matrix system to obtain bone regeneration.

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Bone healing may be improved in implant patients by the administration of osteogenic agents, such as bone morphogenetic protein 2 (BMP-2). But the efficacy of BMP-2 depends upon its mode of application. We hypothesized that BMP-2 is capable of a higher osteogenic efficacy when delivered physiologically, viz., when incorporated into a calcium-phosphate carrier that mimics mineralized bone matrix, than when administered via simple pharmacological modes, such as by adsorption onto a carrier surface. Using an ectopic rat model, we compared the osteoinductive efficacies of calcium-phosphate implant-coatings bearing either incorporated, adsorbed, or incorporated and adsorbed BMP-2. When adsorbed directly onto the naked implant surface, BMP-2 was not osteogenic. When adsorbed onto a calcium-phosphate coating, it was osteoinductive, but not highly efficacious. When BMP-2 was incorporated into calcium-phosphate coatings, it was a potent bone-inducer, whose efficacy was compromised, not potentiated, by the additional deposition of an adsorbed pool.

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OBJECTIVE: Lateral ridge augmentations are traditionally performed using autogenous bone grafts to support membranes for guided bone regeneration (GBR). The bone-harvesting procedure, however, is accompanied by considerable patient morbidity. AIM: The aim of the present study was to test whether or not resorbable membranes and bone substitutes will lead to successful horizontal ridge augmentation allowing implant installation under standard conditions. MATERIAL AND METHODS: Twelve patients in need of implant therapy participated in this study. They revealed bone deficits in the areas intended for implant placement. Soft tissue flaps were carefully raised and blocks or particles of deproteinized bovine bone mineral (DBBM) (Bio-Oss) were placed in the defect area. A collagenous membrane (Bio-Gide) was applied to cover the DBBM and was fixed to the surrounding bone using poly-lactic acid pins. The flaps were sutured to allow for healing by primary intention. RESULTS: All sites in the 12 patients healed uneventfully. No flap dehiscences and no exposures of membranes were observed. Nine to 10 months following augmentation surgery, flaps were raised in order to visualize the outcomes of the augmentation. An integration of the DBBM particles into the newly formed bone was consistently observed. Merely on the surface of the new bone, some pieces of the grafting material were only partly integrated into bone. However, these were not encapsulated by connective tissue but rather anchored into the newly regenerated bone. In all of the cases, but one, the bone volume following regeneration was adequate to place implants in a prosthetically ideal position and according to the standard protocol with complete bone coverage of the surface intended for osseointegration. Before the regenerative procedure, the average crestal bone width was 3.2 mm and to 6.9 mm at the time of implant placement. This difference was statistically significant (P<0.05, Wilcoxon's matched pairs signed-rank test). CONCLUSION: After a healing period of 9-10 months, the combination of DBBM and a collagen membrane is an effective treatment option for horizontal bone augmentation before implant placement.

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OBJECTIVES: To evaluate whether or not preparation of the implant site with osteotomes instead of drilling may improve peri-implant bone density and/or osseointegration, and whether or not this further improves the predictability of immediate loading of SLA implants. MATERIAL AND METHODS: The second, third, and fourth premolars were extracted in both sides of the mandible in six dogs, and after at least 3 months four SLA implants were inserted into each side of the jaw. In three animals, the implant sites were prepared by means of osteotomes, while standard stepwise drilling was used in the remaining animals. In each side of the jaw, two non-adjacent implants were restored with single crowns 4 days after installation, while the remaining two implants were left without crowns to serve as non-loaded controls. After 2, 4, or 12 weeks of loading, specimens including the implants and surrounding tissues were obtained and processed for histologic analysis of undecalcified sections. RESULTS: All implants placed with osteotomes were lost (five before delivery of the crowns and the rest during the first week after loading). None of the conventionally inserted implants, however, was lost, and histomorphometrical analysis revealed similar soft- and hard peri-implant tissue characteristics at immediately loaded and non-loaded implants at all observation times. Average bone-to-implant contact was 59-72% at immediately loaded implants vs. 60-63% at non-loaded ones. CONCLUSION: Preparation of the implant site by means of osteotomes had a deleterious effect on osseointegration, while immediate loading of single, free-standing, SLA implants following a conventional surgical protocol did not jeopardize their osseointegration.

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BACKGROUND: Peri-implantitis is associated with the presence of submarginal plaque, soft-tissue inflammation and advanced breakdown of the supporting bone. The progression of peri-implantitis following varying periods of continuing plaque accumulation has been studied in animal models. OBJECTIVE: The aim of the current experiment was to study the progression of peri-implantitis around implants with different surface roughness. MATERIAL AND METHODS: In five beagle dogs, three implants with either a sandblasted acid-etched surface (SLA) or a polished surface (P) were installed bilaterally in the edentulous premolar regions. After 3 months on a plaque control regimen, experimental peri-implantitis was induced by ligature placement and plaque accumulation was allowed to progress until about 40% of the height of the supporting bone had been lost. After this 4-month period, ligatures were removed and plaque accumulation was continued for an additional 5 months. Radiographs of all implant sites were obtained before and after 'active' experimental peri-implantitis as well as at the end of the experiment. Biopsies were harvested and the tissue samples were prepared for light microscopy. The sections were used for histometric and morphometric examinations. RESULTS: The radiographic examinations indicated that similar amounts of bone loss occurred at SLA and P sites during the active breakdown period, while the progression of bone loss was larger at SLA than at polished sites following ligature removal. The histological examination revealed that both bone loss and the size of the inflammatory lesion in the connective tissue were larger in SLA than in polished implant sites. The area of plaque was also larger at implants with an SLA surface than at implants with a polished surface. CONCLUSION: It is suggested that the progression of peri-implantitis, if left untreated, is more pronounced at implants with a moderately rough surface than at implants with a polished surface.

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OBJECTIVES: To assess the microbiota at implants diagnosed with peri-implantitis, implant mucositis, or being clinically healthy. MATERIAL AND METHODS: Clinical and microbiological data were collected from 213 subjects (mean age: 65.7+/-14) with 976 implants in function (mean: 10.8 years, SD+/-1.5). Forty species were identified by the checkerboard DNA-DNA hybridization method. RESULTS: Implant mean % plaque score was 41.8+/-32.4%. Periodontitis defined by bone loss was found in 44.9% of subjects. Implant mucositis was diagnosed in 59% and peri-implantitis in 14.9% of all cases. Neisseria mucosa, Fusobacterium nucleatum sp. nucleatum, F. nucleatum sp. polymorphum, and Capnocytophaga sputigena dominated the implant sub-mucosal microbiota and the sub-gingival microbiota at tooth sites. Implant probing pocket depth at the implant site with the deepest probing depth was correlated with levels of Eikenella corrodens (r=0.16, P<0.05), the levels of F. nucleatum sp. vincentii (r=0.15, P<0.05), Porphyromonas gingivalis (r=0.14, P<0.05), and Micromonas micros (r=0.17, P=0.01). E. corrodens was found in higher levels at implants with mucositis compared with implant health (P<0.05). Subjects who lost teeth due to periodontitis had higher yields of F. nucleatum sp. vincentii (P<0.02) and N. mucosa (P<0.05). Independent of implant status subjects with teeth had higher levels of P. gingivalis (P<0.05), and Leptotrichia buccalis (P<0.05). CONCLUSIONS: At implant sites studied, few bacteria differed by whether subjects were dentate or not or by implant status.

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The repair of bone defects with biomaterials depends on a sufficient vascularization of the implantation site. We analyzed the effect of pore size on the vascularization and osseointegration of biphasic calcium phosphate particles, which were implanted into critical-sized cranial defects in Balb/c mice. Dense particles and particles with pore sizes in the ranges 40-70, 70-140, 140-210, and 210-280 mum were tested (n = 6 animals per group). Angiogenesis, vascularization, and leukocyte-endothelium interactions were monitored for 28 days by intravital microscopy. The formation of new bone and the bone-interface contact (BIC) were determined histomorphometrically. Twenty-eight days after implantation, the functional capillary density was significantly higher with ceramic particles whose pore sizes exceeded 140 mum [140-210 mum: 6.6 (+/-0.8) mm/mm(2); 210-280 mum: 7.3 (+/-0.6) mm/mm(2)] than with those whose pore sizes were lesser than 140 mum [40-70 mum: 5.3 (+/-0.4) mm/mm(2); 70-140 mum: 5.6 (+/-0.3) mm/mm(2)] or with dense particles [5.7 (+/-0.8) mm/mm(2)]. The volume of newly-formed bone deposited within the implants increased as the pore size increased [40-70 mum: 0.07 (+/-0.02) mm(3); 70-140 mum: 0.10 (+/-0.06) mm(3); 140-210 mum: 0.13 (+/-0.05) mm(3); 210-280 mum: 0.15 (+/-0.06) mm(3)]. Similar results were observed for the BIC. The data demonstrates pore size to be a critical parameter governing the dynamic processes of vascularization and osseointegration of bone substitutes. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007.

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OBJECTIVES: The aim of this prospective study was to evaluate the 5-year performance and success rate of titanium screw-type implants with the titanium plasma spray (TPS) or the sand-blasted, large grit, acid-etched (SLA) surface inserted in a two-stage sinus floor elevation (SFE) procedure in the posterior maxilla. MATERIAL AND METHODS: A total of 59 delayed SFEs were performed in 56 patients between January 1997 and December 2001, using a composite graft with autogenous bone chips combined with deproteinized bovine bone mineral (DBBM) or synthetic porous beta-tricalcium phosphate (beta-TCP). After a healing period averaging 7.75 months, 111 dental implants were inserted. After an additional 8-14-week healing period, all implants were functionally loaded with cemented crowns or fixed partial dentures. The patients were recalled at 12 and 60 months for clinical and radiographic examination. RESULTS: One patient developed an acute infection in the right maxillary sinus after SFE and did not undergo implant therapy. Two of the 111 inserted implants had to be removed because of a developing atypical facial pain, and 11 implants were lost to follow-up and were considered drop-outs. The remaining 98 implants showed favorable clinical and radiographic findings at the 5-year examination. The peri-implant soft tissues were stable over time; the mean probing depths and mean attachment levels did not change during the follow-up period. The measurement of the bone crest levels (DIB values) indicated stability as well. Based on strict success criteria, all 98 implants were considered successfully integrated, resulting in a 5-year success rate of 98% (for TPS implants 89%, for SLA implants 100%). CONCLUSION: This prospective study assessing the performance of dental implants inserted after SFE demonstrated that titanium implants can achieve and maintain successful tissue integration with high predictability for at least 5 years of follow-up in carefully selected patients.

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BACKGROUND: The concept of early implant placement is a treatment option in postextraction sites of single teeth in the anterior maxilla. Implant placement is performed after a soft tissue healing period of 4 to 8 weeks. Implant placement in a correct three-dimensional position is combined with a simultaneous guided bone regeneration procedure to rebuild esthetic facial hard and soft tissue contours. METHODS: In this retrospective, cross-sectional study, 45 patients with an implant-borne single crown in function for 2 to 4 years were recalled for examination. Clinical and radiologic parameters, routinely used in implant studies, were assessed. RESULTS: All 45 implants were clinically successful according to strict success criteria. The implants demonstrated ankylotic stability without signs of a peri-implant infection. The peri-implant soft tissues were clinically healthy as indicated by low mean plaque (0.42) and sulcus bleeding index (0.51) values. None of the implants revealed a mucosal recession on the facial aspect as confirmed by a clearly submucosal position of all implant shoulders. The mean distance from the mucosal margin to the implant shoulder was -1.93 mm on the facial aspect. The periapical radiographs showed stable peri-implant bone levels, with a mean distance between the implant shoulder and the first bone-implant contact of 2.18 mm. CONCLUSIONS: This retrospective study demonstrated successful treatment outcomes for all 45 implants examined. The mid-term follow-up of 2 to 4 years also showed that the risk for mucosal recession was low with this treatment concept. Prospective clinical studies are required to confirm these encouraging results.

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BACKGROUND: It has been shown that different implant designs and different vertical implant positions have an influence on crestal bone levels. The aim of the present study was to evaluate radiographic crestal bone changes around experimental dental implants with non-matching implant-abutment diameters placed submucosally or transmucosally at three different levels relative to the alveolar crest. METHODS: Sixty two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds. The implants were placed submucosally or transmucosally in the left or the right side of the mandible. Within each side, six implants were randomly placed at three distinct levels relative to the alveolar crest. After 12 weeks, 60 crowns were cemented. Radiographs were obtained from all implant sites following implant placement, after crown insertion, and monthly for 6 months after loading. RESULTS: Radiographic analysis revealed very little bone loss and a slight increase in bone level for implants placed at the level of the crest or 1 mm above. The greatest bone loss occurred at implants placed 1 mm below the bone crest. No clinically significant differences regarding marginal bone loss and the level of the bone-to-implant contact were detected between implants with a submucosal or a transmucosal healing. CONCLUSIONS: Implants with non-matching implant-abutment diameters demonstrated some bone loss; however, it was a small amount. There was no clinically significant difference between submucosal and transmucosal approaches.

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PURPOSE: The aim of this study was to evaluate bone apposition to a modified sandblasted and acid-etched (SLA) implant surface (modSLA) in the canine mandible as compared with the standard SLA surface. MATERIAL AND METHODS: In this experimental study, all mandibular premolars and first molars were extracted bilaterally in five foxhounds. After a healing period of 6 months, each side of the mandible received six randomly assigned dental implants alternating between the standard SLA and modSLA surface. The dogs were sacrificed at 2 weeks (n=2) or 4 weeks (n=3) after implant placement. Histologic and histomorphometric analyses were then performed for each implant. RESULTS: The microscopic healing patterns at weeks 2 and 4 for the two implant types with the standard SLA and modSLA surfaces showed similar qualitative findings. New bone tissue had already established direct contact with implant surfaces after 2 weeks of healing. The mean percentage of newly formed bone in contact with the implant (BIC) was significantly greater for modSLA (28.2+/-7.9%) than for SLA (22.2+/-7.3%) (P<0.05). This difference was no longer evident after 4 weeks. An increase in BIC for both implant surface types occurred from weeks 2 to 4. This increase was statistically significant when compared with SLA at 2 weeks (P<0.05), but not when compared with modSLA at 2 weeks. CONCLUSION: The data from the present study demonstrate significantly more bone apposition for the modSLA surface than the standard SLA surface after 2 weeks of healing. This increased bone apposition may allow a further reduction of the healing period following implant placement for patients undergoing early loading procedures.

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INTRODUCTION: This investigation was designed to compare the histomorphometric results from sinus floor augmentation with anorganic bovine bone (ABB) and a new biphasic calcium phosphate, Straumann Bone Ceramic (BCP). MATERIALS AND METHODS: Forty-eight maxillary sinuses were treated in 37 patients. Residual bone width was > or =6 mm and height was > or =3 mm and <8 mm. Lateral sinus augmentation was used, with grafting using either ABB (control group; 23 sinuses) or BCP (test group; 25 sinuses); sites were randomly assigned to the control or test groups. After 180-240 days of healing, implant sites were created and biopsies taken for histological and histomorphometric analyses. The parameters assessed were (1) area fraction of new bone, soft tissue, and graft substitute material in the grafted region; (2) area fraction of bone and soft tissue components in the residual alveolar ridge compartment; and (3) the percentage of surface contact between the graft substitute material and new bone. RESULTS: Measurable biopsies were available from 56% of the test and 81.8% of the control sites. Histology showed close contact between new bone and graft particles for both groups, with no significant differences in the amount of mineralized bone (21.6+/-10.0% for BCP vs. 19.8+/-7.9% for ABB; P=0.53) in the biopsy treatment compartment of test and control site. The bone-to-graft contact was found to be significantly greater for ABB (48.2+/-12.9% vs. 34.0+/-14.0% for BCP). Significantly less remaining percentage of graft substitute material was found in the BCP group (26.6+/-5.2% vs. 37.7+/-8.5% for ABB; P=0.001), with more soft tissue components (46.4+/-7.7% vs. 40.4+/-7.3% for ABB; P=0.07). However, the amount of soft tissue components for both groups was found not to be greater than in the residual alveolar ridge. DISCUSSION: Both ABB and BCP produced similar amounts of newly formed bone, with similar histologic appearance, indicating that both materials are suitable for sinus augmentation for the placement of dental implants. The potential clinical relevance of more soft tissue components and different resorption characteristics of BCP requires further investigation.

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OBJECTIVE: Immediate and early loading of dental implants can simplify treatment and increase overall patient satisfaction. The purpose of this 3-year prospective randomized-controlled multicenter study was to assess the differences in survival rates and bone level changes between immediately and early-loaded implants with a new chemically modified surface (SLActive). This investigation shows interim results obtained after 5 months. MATERIAL AND METHODS: Patients > or =18 years of age missing at least one tooth in the posterior maxilla or mandible were enrolled in the study. Following implant placement, patients received a temporary restoration either on the day of surgery (immediate loading) or 28-34 days after surgery (early loading); restorations consisted of single crowns or two to four unit fixed dental prostheses. Permanent restorations were placed 20-23 weeks following surgery. The primary efficacy variable was change in bone level (assessed by standardized radiographs) from baseline to 5 months; secondary variables included implant survival and success rates. RESULTS: A total of 266 patients were enrolled (118 males and 148 females), and a total of 383 implants were placed (197 and 186 in the immediate and early loading groups, respectively). Mean patient age was 46.3+/-12.8 years. After 5 months, implant survival rates were 98% in the immediate group and 97% in the early group. Mean bone level change from baseline was 0.81+/-0.89 mm in the immediate group and 0.56+/-0.73 mm in the early group (P<0.05). Statistical analysis revealed a significant center effect (P<0.0001) and a significant treatment x center interaction (P=0.008). CONCLUSIONS: The results suggested that Straumann implants with an SLActive can be used predictably in time-critical (early or immediate) loading treatment protocols when appropriate patient selection criteria are observed. The mean bone level changes observed from baseline to 5 months (0.56 and 0.81 mm) corresponded to physiological observations from other studies, i.e., were not clinically significant. The presence of a significant center effect and treatment x center interaction indicated that the differences in bone level changes between the two groups were center dependent.

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Background: The goal of this study was to retrospectively analyze a cohort of 136 patients who underwent dental implant placement in the posterior maxilla at the University of Connecticut Health Center to assess and identify predictors for implant failure in the posterior maxilla. Methods: Data were retrieved from patient charts to identify subjects older than 21 years of age who received dental implant(s) in the posterior maxilla. Patients without a postoperative baseline radiograph were excluded. A recall radiograph was taken 3 to 6 months after implant placement. If there was no recall radiograph, the subject was contacted for a recall visit that included a clinical evaluation and radiographs to determine the implant status. Based on a univariate screening, variables considered potential implant failure predictors included gender, diabetes, smoking, implant length, implant diameter, membrane use, sinus-elevation technique, and surgical complications. These parameters were further assessed, and a multivariable logistic regression was performed with implant failure as a dependant variable. All tests of significance were evaluated at the 0.05 error level. Results: Two hundred seventy-three implants were placed in the posterior maxilla. Fourteen implants failed (early and late failures combined), resulting in a 94.9% overall survival rate. The survival rates for the sinus-elevation group and native bone group were 92.2% and 96.7%, respectively (P = 0.090). Based on the multivariable analysis, sinus floor-elevation procedures were not associated with increased risk for implant failure (P = 0.702). In contrast, smoking and surgical complications had a statistically significant effect on implant failure; the odds ratios for implant failure were 6.4 (P = 0.025) and 8.2 (P = 0.004), respectively. Conclusion: Sinus-elevation procedures with simultaneous or staged implant placement do not increase the risk for implant failure, whereas smoking and surgical complications markedly increase the risk for implant failure.