The International Journal of Oral & Maxillofacial Implants, 04/2013

Purpose: This study was conducted to analyze how a cleaning treatment using plasma of argon would affect fibroblast growth on titanium disks at different time points to determine whether this treatment could enhance soft tissue healing around titanium dental implant abutments. Materials and Methods: Sixty sterile disks made of machined grade 5 titanium were divided into two groups; 30 disks were left untreated (control) and 30 were cleaned using plasma of argon (test). To simulate clinical conditions during soft tissue healing around titanium abutments, both groups were immersed in a culture of murine fibroblasts (L929) for 2, 8, or 48 hours. After preparation, they were stained using 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) to label the cellular nuclei and fluorescent phalloidin to label the cellular bodies. The nuclei were counted, and cellular bodies were analyzed with fluorescent microscopy and imaging analysis software. Analysis was performed at the three different time points. Results: Fibroblast adhesion for the test group was statistically significantly greater versus the control group at 2 and 8 hours but not at 48 hours. At 2 and 8 hours, the cellular bodies in the test group appeared flatter and more spread out, revealing more advanced cellular adhesion, compared to the cells observed in the control group. At 48 hours, the test and control specimens were nearly indistinguishable. Conclusion: The removal of organic and inorganic contaminants from the surfaces of titanium disks using plasma of argon accelerated fibroblast adhesion in the early stages of colonization (2 to 8 hours). This effect disappeared after 48 hours as a result of saturation. Clinically, abutment cleaning using plasma of argon might positively affect soft tissue healing in early stages. Palabras clave: abutments, cell colonization, fibroblast adhesion, glow discharge, plasma cleaning, titanium surface

Purpose: This study examined the effects of the immobilization of Arg-Gly-Asp (RGD) peptide (CAAALLLKERGDSK) on anodized titanium (Ti) via chemical grafting or physical adsorption methods on cell adhesion and osteoblast differentiation. Materials and Methods: The RGD peptide was immobilized on the anodized Ti surface by means of physical adsorption or chemical grafting. The chemical composition of each RGD-immobilized Ti substrate was examined by x-ray photoelectron spectroscopy. The level of cell proliferation was investigated via tetrazolium (XTT) assay. Alkaline phosphatase activity and calcium deposition were evaluated by alizarin red S staining, and mRNA expression of the differentiated osteoblast marker genes was analyzed by reverse-transcriptase polymerase chain reaction. Results: Cell adhesion was enhanced on the RGD-immobilized Ti substrates compared to the anodized Ti surfaces. In addition, significantly increased cell spreading and proliferation were observed with the cells grown on the RGD-immobilized Ti (P .05). Furthermore, the osteoblasts on the RGD-immobilized Ti showed significant increases in the integrin ß1 and type I collagen levels and small increases in osteonectin and osteocalcin levels (P .05). Interestingly, the chemical grafting method resulted in significantly greater effects on adhesion and differentiation than the physical adsorption method (P .05). Conclusion: RGD-immobilized Ti substrates might be effective in improving the osseointegration of dental implants. In particular, the chemical grafting method of RGD immobilization is more favorable and is expected to provide positive outcomes with future animal and clinical studies. Palabras clave: anodized titanium, cell adhesion, differentiation, immobilization, RGD peptide

Purpose: The objective of this study was to evaluate the feasibility of application of thermoplastic poly-L lactic acid (PLLA) membranes for guided bone regeneration in rabbit parietal bone. Materials and Methods: PLLA membranes with a molecular weight of 100,000 (PLLA-100,000) and a molecular weight of 380,000 (PLLA-380,000) were dissolved in chloroform to prepare concentrations of 8% by weight and 4% by weight, respectively. The compression strength, temperature, and time to prepare each formulation were measured. Moreover, the pH was noted and cytotoxicity of the membrane was determined by monotetrazolium assay. In vivo experiments were performed to measure the volume of newly formed bone tissue in hematoxylin and eosin-stained tissue sections 4 and 12 weeks after implantation. Results: The membrane prepared from PLLA-380,000 showed excellent thermoplasticity at 75°C to 80°C and the compressive strength was equal to that of titanium mesh, in contrast to that of PLLA-100,000 and poly(lactic acid-co-glycolic acid). There was a significant change in the pH of an aqueous solution in which the PLLA-380,000 membrane was placed, but there was no cytotoxic activity. The membrane made of PLLA-380,000 induced new bone formation in a dome shape without any membrane deformation. Conclusion: Thermoplastic PLLA membrane shows promise for guided bone regeneration in vertical bone augmentation. Palabras clave: bone augmentation, dental implants, guided bone regeneration, membrane, poly(L-lactic acid), thermoplasticity

Purpose: Artificial materials such as dental implants are at risk of bacterial contamination in the oral cavity. Human beta defensins (HBDs), small cationic antimicrobial peptides that exert a broad-spectrum antibacterial function at epithelial surfaces and within some mesenchymal tissues, could probably help to reduce such contamination. HBDs also have protective immunomodulatory effects and have been reported to promote bone remodeling. The aim of this study, therefore, was to investigate the influence of recombinant HBD-2 on the proliferation and survival of cells in culture. Materials and Methods: Human mesenchymal stem cells (hMSCs), human osteoblasts, human keratinocytes (control), and the HeLa cancer cell line (control) were incubated with recombinant HBD-2 (1, 5, 10, or 20 µg/mL). Cell proliferation and cytotoxicity were evaluated via a water-soluble tetrazolium salt (WST-1) and lactate dehydrogenase assays, respectively. Results: HBD-2 was not toxic in any tested concentration to hMSCs, osteoblasts, keratinocytes, or HeLa cells. Furthermore, proliferation of hMSCs and osteoblasts increased after treatment with HBD-2 at all tested concentrations, and keratinocyte proliferation increased when treated at 20 µg/mL. In contrast, HeLa cancer cells were not affected by HBD-2 as tested. Conclusions: HBD-2 is not only biocompatible but also promotes proliferation of hMSCs, osteoblasts, and keratinocytes in culture. Further investigation of HBD-2 functional surface coating of artificial materials is recommended. Palabras clave: antimicrobial peptides, biocompatibility, human beta defensins, human mesenchymal stem cells, human primary osteoblasts, implant dentistry

Purpose: This in vitro study aimed to identify the effects of the implant system, impression technique, and impression material on the transfer accuracy of implant impressions. The null hypothesis tested was that, in vitro and within the parameters of the experiment, the spatial relationship of a working cast to the placement of implants is not related to (1) the implant system, (2) the impression technique, or (3) the impression material. Materials and Methods: A steel maxilla was used as a reference model. Six implants of two different implant systems (Standard Plus, Straumann; Semados, Bego) were fixed in the reference model. The target variables were: three-dimensional (3D) shift in all directions, implant axis direction, and rotation. The target variables were assessed using a 3D coordinate measuring machine, and the respective deviations of the plaster models from the nominal values of the reference model were calculated. Two different impression techniques (reposition/pickup) and four impression materials (Aquasil Ultra, Flexitime, Impregum Penta, P2 Magnum 360) were investigated. In all, 80 implant impressions for each implant system were taken. Statistical analysis was performed using multivariate analysis of variance. Results: The implant system significantly influenced the transfer accuracy for most spatial dimensions, including the overall 3D shift and implant axis direction. There was no significant difference between the two implant systems with regard to rotation. Multivariate analysis of variance showed a significant effect on transfer accuracy only for the implant system. Conclusions: Within the limits of the present study, it can be concluded that the transfer accuracy of the intraoral implant position on the working cast is far more dependent on the implant system than on the selection of a specific impression technique or material. Palabras clave: implant, implant impression technique, impression material, transfer accuracy

Purpose: The present study sought to compare copy-milled zirconia abutments with standard prefabricated titanium abutments in terms of horizontal and vertical misfit, rotational freedom, and torque loss. Materials and Methods: Twenty regular-platform implants (Brånemark, Nobel Biocare) with a standard external-hexagon implant-abutment interface were divided into two groups. In one group, prefabricated titanium abutments (Easy Abutment, Nobel Biocare) were used; in the other group, custom-made zirconia abutments were fabricated using the Zirkonzahn milling system. Measurements of geometry, rotational freedom, and marginal discrepancy were performed using a video measuring machine. To measure torque loss, each abutment was torqued to 32 Ncm and then loosened with a digital torque wrench. The torque loss values were reported as a percentage of the applied torque. Results: Rotational freedom and horizontal misfit were significantly higher with the customized abutments. There were no statistically significant differences in vertical misfit or in mean percentage of torque loss between the two groups. Conclusions: Within the limitations of this study, it could be concluded that copy-milled zirconia abutments do not fit as accurately as prefabricated titanium abutments. However, the less precise fit of customized zirconia abutments does not seem to affect their ability to maintain the applied torque. Palabras clave: copy milling, dental implant-abutment interface, fit, rotational freedom, torque, zirconia

Purpose: The purpose of this study was to assess the variation of rotational freedom at the implant interface of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic abutments with internal-hexagon connections before and after artificial aging and after porcelain sintering. Materials and Methods: Thirty Y-TZP ceramic abutments with internal-hex connections were used in this study. Three groups of 10 abutments each were created. Group C was made up of abutments in the as-received condition, group A abutments went through 1 hour of autoclaving at 134°C to simulate the effect of 3 to 4 years of aging in vivo, and group P abutments went through porcelain sintering procedures. Measurements of rotational freedom were compared between groups. The quantitative differences between groups were assessed using multivariate analysis of variance. Statistical testing was carried out at the 5% significance level. Results: A mean rotational freedom of 115.34 ± 1.42 minutes was found for group C abutments; the values for group A and group P abutments were 115.35 ± 1.73 minutes and 115.37 ± 1.54 minutes, respectively. None of these differences were statistically significant between the three groups. Conclusion: Misfit of the Y-TZP ceramic abutment on the internal-hex connection of implants may be implicated in screw joint loosening. The results of this report suggested that, if all laboratory steps are followed carefully, changes will not occur at the implant/Y-TZP ceramic abutment interface. Maintenance of the original features of the abutment may reduce the risk of screw loosening. Palabras clave: aging, implant abutment, implant/abutment connection, internal-hexagon connection, zirconia

Purpose: Tissue engineering and regenerative medicine may now be used for the treatment of maxillofacial defects, but the related procedures have several limitations, including high capital investment, expensive cell culture techniques, and complicated safety and quality management issues. Stem cells secrete many cytokines that can affect cell mobilization and differentiation that accumulate in conditioned media. This study investigated the effects of stem cell-conditioned media from human bone marrow-derived mesenchymal stem cells (MSCs) on bone regeneration and its ability to induce endogeneous stem cell mobilization and bone regeneration. Materials and Methods: Human MSCs that were 70% to 80% confluent were refed with serum-free Dulbecco's modified Eagle medium, and the cell-cultured conditioned media were collected after 48 hours of incubation. The collected media were defined as cultured conditioned media from MSCs (MSC-CM). Rat bone-marrow-derived stem cells (rMSCs) were cultured with MSC-CM for 48 hours; then, cell mobilization and the expression of osteogenic-related genes were investigated. The presence of cytokines in MSC-CM was determined by enzyme-linked immunosorbent assay. Collagen sponge was then soaked in MSC-CM and grafted into rat calvarial bone defects. At 2 or 4 weeks after implantation of graft materials, implanted sections were evaluated by microcomputed tomography and histologic analysis. Results: MSC-CM enhanced the migration, proliferation, and expression of osteogenic marker genes, such as alkaline phosphatase, osteocalcin, and Runx2, of rMSCs in vitro. Cytokines such as insulinlike growth factor-1, vascular endothelial growth factor, transforming growth factor-ß1, and hepatocyte growth factor were present in the MSC-CM. MSC-CM significantly increased the migration and expression of osteogenic-related genes of rMSCs. Early bone regeneration in rat calvaria was also observed. Conclusion: These results suggest that MSC-CM may have potential for novel cell-free regeneration of bone. Palabras clave: bone, conditioned medium, growth factors, mesenchymal stem cells, paracrine factors, regenerative medicine

Purpose: The purpose of this study was to survey the prosthodontists of the American College of Prosthodontists (ACP) and the American Academy of Maxillofacial Prosthetics (AAMP) to identify the most commonly used implant both during their training and currently in practice, and to evaluate overall restorative preference. Participants were asked to rank criteria that make an implant company desirable and important features when selecting an implant. Materials and Methods: An electronic survey was emailed to 1,739 members of the ACP and AAMP. Results: The majority of respondents (79%) were trained using Nobel Biocare brand implants, which was also the brand most often selected by participants for use in all regions of the oral cavity (34% to 39%, location dependent). Abutment preferences varied by area: incisors and canines (29%) and highly esthetic areas (53%) were more likely to be restored with custom milled zirconia abutments, while prefabricated titanium abutments were preferred for premolars and molar areas. Conventional loading was most often applied, ranging from 95% in medically compromised patients to 55% in esthetic areas. The majority of participants (86%) used Locator attachments for complete overdenture restorations. Also, respondents selected an implant company based on features and literature support versus cost and customer service. The implant features deemed most important were the design of the internal connection and ease of finding replacement parts; thread design and variety of abutments were deemed least important. Respondents reported that while implant planning software was used, they rarely/never order the concurrent surgical guide. Conclusion: Within the study's limitations, the majority of prosthodontists select implants based on training, features, and literature support. Palabras clave: implant restoration, implant selection, implant survey, implant systems

Purpose: There is a need for improved methods of reducing peri-implant bone loss. This study evaluated the structural, drug loading, drug release, and in vitro characteristics of collagen membranes impregnated with zoledronic acid (ZA). Materials and Methods: Two commercially available collagen barrier membranes (Bio-Gide and BME-10X) were loaded with ZA. The physicochemical and pharmacologic properties of the membranes were characterized with scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and high-performance liquid chromatography. The ZA-loaded membrane's inhibition of osteoclasts and promotion of osteoblast growth was evaluated in vitro at ZA concentrations of 0, 10-4, 10-3, and 10-2 mol/L. Results: The disappearance of micropores between Bio-Gide collagen fibers and the formation of crystalloids on the surface of BME-10X membranes following ZA loading was evident under the microscope. Phosphorus was detected on the membranes, and amide shifts were observed. Greater amounts of ZA loading and slower ZA release were evident for Bio-Gide membranes. Osteoclast numbers were reduced with ZA, and a corresponding decrease in bone resorption was evident at higher ZA concentrations (P .05). After 7 days, at a ZA concentration of 10-3 mol/L, Bio-Gide membranes had an increased osteoblast proliferation index, while both types of membranes displayed increased alkaline phosphatase expression. Conclusion: Collagen membranes loaded with ZA provided delayed drug release. This study may offer a novel therapeutic strategy for minimizing peri-implant bone resorption. Palabras clave: collagen membranes, drug delivery systems, osteoblasts, osteoclasts, zoledronic acid

Purpose: The objectives of this study were to evaluate the galvanic corrosion behavior between titanium and nickel-chromium (Ni-Cr) alloy, to investigate the effect of diamondlike carbon (DLC) coating over titanium on galvanic corrosion behavior between titanium and Ni-Cr alloy, and to evaluate the effect of DLC coating over titanium abutments on the fit and integrity of prosthetic assemblies by scanning electron microcopy (SEM). Materials and Methods: Five Ni-Cr and 10 titanium disks with a diameter of 5 mm and thickness of 3 mm were prepared. DLC coating was applied to five titanium disks. Electrode samples were prepared, and open circuit potential measurements, galvanic current measurements over platinum electrodes, and potentiodynamic polarization tests were carried out. For the SEM evaluation, 20 Ni-Cr alloy and 10 gold alloy superstructures were cast and prepared over 30 abutments. DLC coating was applied to 10 of the abutments. Following the fixation of prosthetic assemblies, the samples were embedded in acrylic resin and cross sectioned longitudinally. Internal fit evaluations were carried out through examination of the SEM images. Results: Titanium showed more noble and electrochemically stable properties than Ni-Cr alloy. DLC coating over the cathode electrode served as an insulating film layer over the surface and prevented galvanic coupling. Results of the SEM evaluations indicated that the DLC-coated and titanium abutments showed no statistically significant difference in fit. Hence, no adverse effects on the adaptation of prosthetic components were found with the application of DLC coating over abutment surfaces. Conclusions: DLC coating might serve as a galvanic corrosion barrier between titanium abutments and Ni-Cr superstructures. Palabras clave: diamondlike carbon, galvanic corrosion, nickel-chromium, titanium

Purpose: To evaluate, through a systematic review of the literature, the efficacy of different surgical techniques in maintaining residual bone in the alveolar process following tooth extractions. Materials and Methods: MEDLINE/PubMed was searched through January 2010 and papers were selected according to the CONSORT statement and an independent three-stage screening process. The selected outcome variables were clinical width and height changes of the socket, and means and standard deviations were calculated from the included studies. For those studies that were randomized controlled trials, six meta-analyses were performed by dividing studies into three groups with regard to the use of barriers and grafting (barriers alone, graft alone, or both). Results: Thirteen papers met the eligibility criteria and were included in the analyses. Statistically significant ridge preservation was found for studies that used barriers alone; the pooled weighted mean was 0.909 mm (95% confidence interval, 0.497554 to 1.320732 mm) for bone height, while the mean for bone width was 2.966 mm (95% confidence interval, 2.334770 to 3.598300 mm). Conclusions: Socket preservation procedures are effective in limiting horizontal and vertical ridge alterations in postextraction sites. The meta-analysis indicates that the use of barrier membranes alone might improve normal wound healing in extraction sites. Palabras clave: alveolar socket preservation, ridge preservation, systematic review

Purpose: The aim of this case series is to propose an approach to help maintain autogenous bone grafts. This is done by applying a collagen membrane (CM) and anorganic bovine bone (ABBM) at the time of implant surgery, rather than at the time of ridge augmentation, to avoid volume loss after implants are inserted. Materials and Methods: Ten patients with severe horizontal bone atrophy were consecutively enrolled in this study. A staged approach was chosen for implant placement following horizontal ridge augmentation. A block graft was harvested from the retromolar area and secured to the recipient site with fixation screws; contour overbuilding was avoided. The width of the ridge was measured before and after horizontal augmentation. After 4 months of healing, implants were inserted, the augmented site was relined with ABBM, and CM was applied to prevent bone volume loss. Another 4 months later, at the time of abutment placement, cone beam computed tomography was performed to quantify the end result. Results: The mean horizontal ridge width prior to treatment was 2.1 ± 0.5 mm. Mean postsurgical crest width was 6.9 ± 0.5 mm. After the 4-month healing period, the mean alveolar crest width was 6.6 ± 0.6 mm. At the time of abutment connection, the mean width of the regenerated ridge, as measured on three-dimensional cone beam images, was 7.7 ± 0.8 mm. Conclusions: Minimal bone loss occurred in unprotected autogenous bone grafts with respect to alveolar bone contour (0.25 ± 0.29 mm). After the implants were inserted, no further remodeling/resorption occurred with sites treated by ABBM and CM relining; moreover, an additional increase in alveolar crest width was evident. The nonresorbable ABBM osseointegrated clinically and radiologically, preventing bone loss prior to implant loading. This layer appeared to maintain the regenerated crest volume. Palabras clave: autogenous bone graft, bone augmentation, bone resorption, volume maintenance

Purpose: The aim of this in vitro study was to investigate the potential of digital and conventional radiography to detect small amounts of residual dental luting cements around implant abutments. Materials and Methods: Artificial cement and aluminum overhangs in varying thicknesses, heights, and depths were radiographed adjacent to implant restorations with a radiovisiography sensor. Five trained evaluators were asked to identify the smallest depth of overhang that could be detected on radiographs. Results: For detection of cement overhangs adjacent to implant abutments, a luting agent must have greater radiopacity than what is recommended by relevant International Organization for Standardization directives. To detect a 0.1-mm-thick portion of excess cement adjacent to an implant abutment, the cement should have a radiopacity of at least 1.7 mm of aluminum for high-resolution digital radiographs and 2.2 mm of aluminum for film-based radiographs. Two-way analysis of variance revealed that the thickness of the specimens, type of imaging detector, and type of cement all affected the radiopacity threshold for artificial cement excess (P .05). The height of the specimens and the surrounding structures were not statistically significant factors in cement detection. Conclusions: Digital radiography offers better possibilities for visualization of cement excess than conventional radiography. Palabras clave: cement overhang, digital radiography, luting cement, radiopacity

Purposes: The aim of this study was to assess the effectiveness of barrier membranes in bone augmentation through a systematic review of the literature. Materials and Methods: Electronic data banks and hand searching were used to find relevant articles on the reconstruction of localized bone defects published up to May 2011. Controlled animal and human studies with more than 4 weeks of follow-up were included; studies of periodontal lesions, extraction sockets, and maxillary sinus grafts were excluded. Applications of recombinant growth factor or assessments of membranes' effects on implant osseointegration were also considered exclusion criteria. Defects filled with bone graft/bone substitute material and covered with a membrane were considered the test group, while uncovered defects were considered the control group. Thereafter, human and animal studies were evaluated separately by meta-analysis. Results: Of the 3,986 articles found in the initial search, 34 studies met the inclusion criteria. Four animal studies concluded that the use of barrier membranes would increase the amount of vertical augmented bone (mean difference 0.32 mm; P = .006). Qualitative results regarding horizontal bone augmentation were controversial. Membranes do not increase the risk of improper healing, according to both human studies (odds ratio 5.67; P = .32) and animal studies (odds ratio 3.35; P = .12). Conclusion: There is limited evidence to support the effectiveness of barrier membranes in the treatment of bone deficiencies. Membranes do not increase postoperative infection, wound dehiscence, or membrane/bone graft exposure in either human or animal models. Because a majority of the results are based on animal studies, more randomized clinical trials are needed to objectively measure the efficacy of membranes in human bone augmentation. Palabras clave: bone engineering, bone regeneration, guided bone regeneration, guided tissue regeneration, nonresorbable membrane, resorbable membrane

Purpose: An international Delphi study was undertaken to determine by consensus an agreed approach to the management of children with dental manifestations of ectodermal dysplasia, including the use of dental implants. This was done using a questionnaire developed by an interdisciplinary team. Materials and Methods: The Delphi study questionnaire was built around 19 areas of clinical relevance and included 90 items. Topic areas included dental disability; initial diagnosis; global disability; oral health aspects of dental treatment (orthodontics, hypodontia, anodontia, implants); and case studies of selected treatment options. Eleven teams from six countries contributed to three iterations of the questionnaire. An algorithm was designed to standardize analysis of the questionnaire answers, all of which were blinded to ensure anonymity. The second and third rounds of the questionnaire excluded previously agreed-upon items but included the responses to the questions from the earlier rounds. The nonconsensus items inquired about the use of radiographs at initial diagnosis; sedation of an uncooperative child; use of a pretreatment questionnaire; the age range for specific treatments (eg, dentures, orthodontics, implants); specific uses of implants (eg, partial prostheses, overdentures, cantilevered prostheses); and case study 2. The residual nonconsensus questions were subsequently discussed at a 2-day meeting. Results: Among the 90 questions and partial questions, there was progressive consensus, with agreements in rounds 1, 2, and 3 of 61%, 21%, and 8%, respectively. At the conclusion of round 3, there was 90% agreement and it was considered that the nonconsensus items required in-depth face-to-face discussion at a consensus meeting, which is described in part 2 of the study. Conclusion: The Delphi study provided an opportunity to engage specialist teams in recognized centers to integrate their clinical knowledge and draw on published data to develop a consensus of evidence-based responses. Palabras clave: consensus, Delphi study, ectodermal dysplasia

A consensus meeting was arranged to provide an opportunity to discuss the residual nonconsensus questions following three rounds of a Delphi study. It was hoped that the nonagreements could be resolved to define a comprehensive protocol for the management of ectodermal dysplasia, particularly with respect to the use of dental implants in growing patients. An international panel of expert clinicians in pediatric dentistry, prosthodontics, and orthodontics was invited to be part of the Delphi study to develop agreement on clinical questions through a consensus of ideas. Each expert had been invited to form a study group or team within his or her home institution. As required by the Delphi protocol, a 90-part questionnaire was considered by the collaborating teams and progressed through three iterations with increasing agreement. This process is discussed in part 1 of the study. The residual nonconsensus questions, which represented 10% of the questionnaire, required collaborative interaction for resolution. The consensus meeting was held in London, England, over a 2-day period with support from Nobel Biocare and the British Dental Association. Palabras clave: clinical research, clinical trials, morphometric analysis, structural biology, tissue physiology

Purpose: To compare clinical outcomes of three-unit fixed prostheses supported by two or three implants in the posterior region. Materials and Methods: Patients in this retrospective study were restored with three-unit fixed partial prostheses supported by two (group 1) or three (group 2) implants in the partially edentulous posterior maxilla and mandible. Outcome measures were survival and success rate, marginal bone loss, complication rate, and peri-implant soft tissue indices. Two-way ANOVA and an independent t test were performed at a significance level of P .05. Result: A total of 48 implants placed in 23 patients (group 1) and 132 implants placed in 40 patients (group 2) were observed for 52.9 ± 19.7 months and 58.5 ± 22.0 months, respectively. Both groups showed a 100% survival rate. The success rate, considering marginal bone loss, was 82% (group 1) and 86% (group 2). Marginal bone loss was greater in group 1 every year during 3 years of measurement, but the difference was not statistically significant (P > .05). Differences of marginal bone loss according to sex, anatomical location (maxilla vs mandible), and connection type (external vs internal) also were not significant (P > .05). Complication rates were similar, but Plaque Index was significantly greater in group 2 (P .05). Conclusion: Within the limitations of this study, three-unit fixed partial prostheses supported by two implants showed comparable clinical outcomes with those supported by three implants in the partially edentulous posterior maxilla and mandible during the short- to medium-term. Palabras clave: bone loss, implant, soft tissue index, survival rate, three-unit fixed partial prosthesis

Purpose: To compare immediate and conventional loading of fixed full-arch maxillary prostheses supported by implants placed in healed and fresh postextraction sites. Materials and Methods: This prospective, controlled, nonrandomized 12-month study included 30 consecutive patients requiring fixed full-arch maxillary prostheses supported by implants placed in healed and fresh extraction sites. Fifteen patients were treated with conventional loading (control group), and 15 were treated with immediate loading (test group). Each patient received six to eight implants; implants with insertion torque 35 Ncm were conventionally loaded and excluded from the analysis. Implant success, biologic and prosthetic complications, success of the immediately loaded provisional prostheses, and marginal bone loss were assessed and analyzed statistically. Results: One test group patient failed to attend recall visits and was excluded from the study, and 16 implants did not achieve insertion torque of 35 Ncm and were excluded from analyses. The final sample included 29 patients and 193 implants (94 test implants, 99 control implants). Implant success rates were 96.8% (test) and 99.0% (control). In the test group, the most common complications were screw loosening and tooth fractures; in the control group, dentures caused discomfort and soft tissue irritation. The success rate of the immediately loaded prostheses was 100%. Average bone loss was 0.61 ± 0.21 mm for test implants and 0.53 ± 0.18 mm for control implants. Differences between loading protocols were not statistically significant. Conclusions: No significant differences in implant success and peri-implant marginal bone loss were seen in the current 12-month comparison of immediate and conventional loading of maxillary fixed full-arch prostheses. Biologic and prosthetic complications were rare with both loading protocols, and all immediately loaded provisional fixed prostheses performed successfully. Palabras clave: full-arch prosthesis, immediate implants, immediate loading

Purpose: To evaluate factors promoting mucositis and peri-implantitis (plaque accumulation, poor peri-implant soft tissue health, bone loss) with regard to prosthetic attachment systems consisting of implant-supported bar-retained overdentures. Materials and Methods: Patients who received TiOblast implants to support overdentures retained by either (1) prefabricated bars with or without extensions or (2) cast bars were recalled and examined clinically and radiographically. Plaque Index (PI), Sulcus Bleeding Index (SBI), probing pocket depth (PPD), and peri-implant bone loss were measured. Peri-implant tissue health was assessed, and the presence of mucositis and peri-implantitis was recorded. One-way analysis of variance with the Bonferroni adjustment was used to compare groups (α = .05). Results: Five to 10 years after prosthetic loading, 107 patients who received 516 TiOblast implants were evaluated; 31 of these patients were treated with 131 implants to support bar-retained overdentures. PI, SBI, PPD, and pathologic bone loss were least common in the group with prefabricated bars, followed by the group with prefabricated bars with extensions, and were most common in the group with cast bars. Plaque accumulation and pathologic bone loss values were higher with implants that supported mandibular bar-retained overdentures than with those supporting maxillary bar-retained overdentures. However, these differences among attachment systems or between maxillary and mandibular implants were not significant (P > .05). Mucositis was observed in one implant in the group with prefabricated bars, four implants in the group with prefabricated bars with extensions, and four implants in the group with cast bars. Peri-implantitis was observed in one implant of the cast bar group. Conclusions: Five to 10 years after prosthetic loading, no significant difference in PI, SBI, PPD, pathologic bone loss, or peri-implant tissue conditions among the different bar designs tested was observed. Palabras clave: bar design, bone loss, dental implant, mucositis, overdenture, peri-implantitis

Purpose: The aim of this study was to assess the long-term reliability of Locator-retained mandibular or maxillary overdentures and to examine clinical and radiographic parameters of the supporting implants. Materials and Methods: The authors performed a retrospective analysis of a case series. After implant placement and a submerged healing phase of about 3 months, all implants were restored with Locatorretained overdentures. The follow-up examinations included the assessment of the Plaque Index (PI) and sulcus Bleeding Index (SBI) as well as peri-implant soft tissue parameters, such as bleeding on probing (BOP) and pocket probing depth (PPD). The mean marginal bone loss was measured on panoramic radiographs. The clinical performance of Locator components and the prosthetic restoration were evaluated. Descriptive statistics were computed. For statistical analysis, non-parametric and parametric tests with respect to the variable scale were used. The significance level was set as P = .05. Results: The sample was composed of 33 patients (18 men, 15 women) with a mean age of 66.8 years who received 132 implants (84 in the anterior maxilla, 48 in the anterior mandible). After 32.9 months of follow-up, one maxillary implant was lost. All prosthetic restorations were still functionally in place at the last follow-up appointment with moderate prosthodontic maintenance effort. Clinical parameters and radiographs revealed healthy tissues around most implants. Conclusion: Within the limitations of this study, it can be concluded that Locators are a predictable alternative for anchorage of mandibular and maxillary overdentures with good clinical performance of both the prosthetic restorations and the supporting implants. Palabras clave: four implants, Locator, overdenture

Purpose: To evaluate the 5-year outcome of a previously reported case series of patients with severely atrophic maxillae treated with palatally positioned implants and fixed full-arch rehabilitations. Materials and Methods: A retrospective cross-sectional clinical study of patients treated between January 2000 and January 2004 with palatally positioned implants was carried out. The parameters evaluated at the 5-year follow-up visit were: implant success rate, peri-implant soft-tissue conditions, biological and prosthetic post-loading complications, radiographic peri-implant marginal bone loss, and patient satisfaction. Results: A total of 33 patients with 151 palatally positioned implants were included in the study; 15 patients had received cemented prostheses and 18 had received screwed full-arch prostheses. The success rate for palatally positioned implants after 5 years was 98.7%. Average peri-implant mucosa retraction was 0.39 ± 0.94 mm and the average probing depth was 2.89 ± 0.77 mm. Plaque Index was 0 in 63.1% of the implants, 1 in 18.8%, 2 in 8.7%, and 3 in 9.4%. The modified Bleeding Index was 0 in 71.1%, 1 in 14.1%, and 2 in 14.8%. Mucositis was found in 5.2% of the implants and none had peri-implantitis. Prosthetic complications occurred in 12.1% of the cases. Average peri-implant marginal bone loss was 1.03 ± 1.28 mm. General patient satisfaction averaged 8.2 ± 1.8 according to a 10-point visual analog scale, and good quality of life was reported by most patients. Conclusions: Palatally positioned implants were found to be an adequate treatment for patients with severely atrophic maxillae. A high implant success rate, good peri-implant soft tissue stability, low marginal bone loss, high patient satisfaction and few complications were registered. Palabras clave: bone atrophy, full-arch prosthesis, maxillary atrophy, palatal implants

Purpose: Marginal bone loss around implants is of great concern, and its cause may be multifactorial. Recently, clinical cases presenting marginal bone loss, in most cases accompanied by vertical fracture of internal-connection implants in the buccolingual direction, have been reported, in which unfavorable stress distribution is one possible cause of marginal bone resorption. The purpose of the current study was to characterize this type of marginal bone loss and implant fracture by conducting a finite element analysis (FEA). Materials and Methods: Clinical and radiographic evaluations showed that the prostheses of all reported cases had implant-level setups and were directly screwed to the internal implants. Intriguingly, all vertical fractures reported were in the buccolingual direction. Therefore, to characterize the specific implant fractures, FEA was conducted with misfit models created for two different setups, abutment-level and implant-level, both with screw-retained prostheses. The models were subjected to initial misfits of 0 µm (representing perfect fit), 50 µm, 100 µm, 150 µm, or 200 µm, and vertical loading was then applied. Results: FEA revealed that, for the implant-level setup, excessive stress at the neck of the implant gradually increased in the buccolingual direction as the misfit increased. This result was not seen for the abutment-level setup. A broad maximum stress distribution was evident for the implant-level setup but not for the abutment-level setup. Conclusion: Broad distribution of excessive stress in the FEA correlated to the clinical cases, and marginal bone loss in these cases may be associated with mechanical alterations. To avoid unnecessary complications, selection of an abutment-level setup is strongly suggested. Palabras clave: finite element analysis, implant vertical fracture, marginal bone loss, mechanical alteration, misfit

Purpose: Unlike standard dental implants, the stabilization of orthodontic microscrews removed after treatment is done without osseointegration and achieved by several components: cortical bone thickness (CBT), microscrew geometry, and drilling depth. The purpose of this study was to evaluate 10 different microscrews and the influence of their geometric parameters with different CBT and drilling depths. Materials and Methods: The influence of geometric parameters in cortical bone was analyzed with a series of computational simulations with finite element models to obtain von Mises stresses and deformations in the microscrew when loaded with a perpendicular traction force of 1 N and considering the angle of incidence as a random parameter. Results: There was variability in the angle of incidence, with less clinical influence. Biomechanical parameters such as microscrew diameter, CBT, and drilling depth had significant influences on the results. At a drilling distance of 8 mm, narrow microscrews (Abso Anchor 1.2) showed maximum von Mises stress of 500.698 MPa and maximum deformation in the shank of 0.08549 mm. Microscrews with a diameter of 1.5 mm (Dentaurum, Jeil, Mondeal, Tekka, Spider) showed von Mises stresses ranging from 56.97 to 136 MPa and deformation between 0.0062055 and 0.0476 mm. Microscrews with a diameter of 2.0 mm (Jeil, Mondeal, Tekka) showed von Mises stresses ranging from 17.172 to 54.861 MPa and deformation of 0.000172 to 0.0161 mm. Conclusions: The shape and geometry of an orthodontic microscrew are highly important in its behavior. Optimal characteristics of a microscrew would include a diameter of 2.0 mm, a cylindric shape, a short and wide head, a short and wide shank, and threads of an appropriate size. Palabras clave: cortical bone, finite element method, microscrews, orthodontics, random, variance

This case report presents a histologic and histomorphometric evaluation of the peri-implant tissues of a HA-coated implant retrieved due to peri-implantitis after a 10-year loading period. The implant was retrieved with a trephine and treated to obtain thin ground sections. At low-power magnification mostly compact, mature bone with small marrow spaces could be observed at the interface with the implant. The coating was always present in the areas where bone was detected, the bone was always in close contact with the coating, and there was no detachment between the metal and coating or between the coating and bone. Areas of bone remodeling were demonstrated by the presence of many secondary osteons and reversal lines close to the implant surface. The bone-implant contact percentage was 36.3% ± 1.2%. The percentage of the implant surface covered by the HA coating without bone, where bone may have detached during retrieval, was 32.6% ± 2.8%. This HA-coated implant, continued to demonstrate more than adequate BIC after many years of function and the potential to maintain osseointegration in the long term. Palabras clave: coating failure, coating resorption, histology, hydroxyapatite coating, long-term study

This case report describes a rare displacement of a dental implant in the infratemporal fossa, which occurred during placement of the implant into the pterygoid process with computer-assisted technology. The implant was immediately removed by means of an intraoral approach to prevent any neurologic complications. Although computer-aided systems in implant surgery represent a reliable and effective tool, the surgeon should always instruct the patient on the necessary behavior during implant placement and the risks associated with a lack of adherence to these recommendations. Palabras clave: complication, dental implants, foreign body, infratemporal fossa