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Purpose: The All-on-4 treatment concept has been shown to be an effective clinical procedure; however, to date, no studies have analyzed the subgingival microbiota present in these restorations. The purpose of this study was to evaluate the microbial profile of the subgingival biofilm around dental implants placed in the All-on-4 protocol and compare the microbial profile around axial and tilted implants. Materials and Methods: Fourteen subjects treated by the All-on-4 concept were evaluated clinically and microbiologically. Subgingival biofilm was collected from each patient, and the amount of 40 species of bacteria was assessed using the checkerboard DNA-DNA hybridization technique. Results: The results for the indices of probing depth (PD), bleeding on probing, marginal bleeding, and visible plaque were 2.32 mm, 46%, 60%, and 57%, respectively. Tilted implants presented a significantly higher mean PD and Plaque Index compared with axial implants (P .05). Fusobacterium nucleatum ssp vincentii, Veillonella parvula, and Fusobacterium nucleatum ssp polymorphum were found in higher levels; however, no difference in the microbial composition was observed between tilted and axial implants (P > .05). Tilted implants presented statistically higher mean levels for the orange complex in relation to the axial implants (P .05). Conclusion: Despite the clinical success rate of the All-on-4 protocol, the subgingival biofilm of tilted implants presented a higher proportion for the orange complex pathogens in comparison to axial implants. These data could suggest that subjects with this modality of implant-supported restoration must be aware that they need a more rigorous maintenance protocol. Keywords: All-on-4, dental implant, microbiota, prosthesis, subgingival biofilm

Purpose: To evaluate the gene expression levels of semaphorins 3A, 3B, 4A, and 4D in both healthy and diseased implants. Materials and Methods: Subjects with peri-implantitis presented clinical attachment loss, probing depth ≥ 5 mm, bleeding on probing and/or suppuration, and radiographic bone loss > 4 mm. Peri-implant tissue biopsy specimens were sampled for analysis of the mRNA expression levels for semaphorins 3A, 3B, 4A, and 4D. A real-time polymerase chain reaction was performed, and the gene expression levels of semaphorins in relation to the housekeeping gene were analyzed by using the nonparametric Mann-Whitney test (P .05). Results: Thirty-five subjects (16 men, 19 women; mean age: 54.12 ± 2.34 years) with implant-supported restorations, using screw-shaped dental implants with internal or external hexagon were enrolled in this study. Higher levels of semaphorins 3A and 4D were detected in the peri-implantitis compared with the healthy tissues (P = .0011 and P = .0404, respectively), whereas Sem4A levels were significantly higher in the control group (P .0001). Differences between groups in the expression levels of Sem3B were not significant. Conclusion: Advanced peri-implantitis lesions showed higher levels of gene expression for Sem3A and Sem4D and lower levels of Sem4A in comparison to tissues obtained from a healthy dental implant. Keywords: dental implants, gene expression, peri-implantitis, real-time PCR, semaphorins

Purpose: The aim of this prospective controlled study was to evaluate the influence of osteopenia on the levels of osteoclastogenesis-related factors in the peri-implant crevicular fluid (PICF) and on the clinical parameters of immediately loaded implants. Materials and Methods: This study included 24 patients who received at least two implants in the mandible, with restorations delivered 48 hours after implant placement. Patients were divided into control (n = 11) and osteopenia (n = 13) groups. Seven days after implant placement (baseline) and 4 months after implant placement, PICF samples were obtained, and clinical parameters (Plaque Index, Gingival Index, bleeding on probing, suppuration, probing depths, clinical attachment levels) were measured. A commercially available enzyme-linked immunosorbent assay was used to analyze PICF samples for levels of soluble receptor activator of nuclear factor of κB ligand (sRANKL) and osteoprotegerin (OPG). At the 4-month follow-up visit, the implant-supported restorations were removed and periapical radiographs were acquired to evaluate bone loss around the implants. Results: Eighty-eight immediately loaded implants were included in this study (38 in the control group, 50 in the osteopenia group). The RANKL and OPG levels, the RANKL/OPG ratio, and the clinical parameters were similar between the groups at both time points. However, the levels of these factors in PICF differed significantly between baseline and 4 months after surgery. Conclusion: Within the limitations of this short-term study, it can be concluded that osteopenia does not influence the PICF levels of osteoclastogenesis-related factors in immediately loaded implants after 4 months of loading. Keywords: dental implants, dental implant loading, immediate loading, osteopenia, osteoporosis, osteoprotegerin, RANK ligand, receptor activator of nuclear factor-kappa B

The aim of this study was to assess the impact of replacing conventional mandibular complete dentures with implant-supported fixed complete dentures (ISFDs) on the oral health-related quality of life (OHQOL) of edentulous patients and on the associated kinesiographic parameters. The patients had their complete dentures replaced by ISFDs and were assessed after 1, 2, 3, 6, and 12 months. An improvement of general OHQOL was observed 2 months after treatment with ISFDs. Kinesiographic recordings revealed significant mandibular vertical and horizontal opening increases and a greater vertical intrusion of the maxillary complete dentures during clenching after the treatment with ISFD.

Purpose: Modifications in implant surface topography and chemistry may alter the early bone response at different levels. This study characterized four implant surfaces and evaluated the biomechanical fixation and histologic response at early implantation times in a canine radius model. Materials and Methods: Externalhexagon Brånemark-type implants were used with four experimental surfaces: microblasted (MI), acid-etched and microblasted (AAM), anodized (A), and discrete crystalline deposition (DCD). Surface topography was assessed by scanning electron microscopy, interferometry, and x-ray photoelectron spectroscopy. The implants were placed in the central region of the radii of eight beagle dogs and remained in vivo for 10 or 30 days. The implants were torqued to interface failure, and a general linear statistical model with torque as the dependent variable and implant surface and time in vivo as independent variables was used. Results: All surfaces presented were textured, and different surface chemistries were observed. No significant differences between implant surfaces were observed for torque at 10 days. However, at 30 days, the AAM surface presented significantly higher torque values compared to the DCD and A surfaces. Significantly higher torque values were observed at 30 days compared to 10 days (P .001). Conclusions: Significantly different biomechanical fixation dependent on surface preparation was observed after 30 days, and all surfaces were biocompatible and osteoconductive. Keywords: dental implant, histology, in vivo, osseointegration, surface properties

Purpose: To evaluate the biomechanical fixation, bone-to-implant contact (BIC), and bone morphology of screw-type root-form implants with healing chambers with as-machined or dual acid-etched (DAE) surfaces in a canine model. Materials and Methods: The animal model included the placement of machined (n = 24) and DAE (n = 24) implants along the proximal tibiae of six mongrel dogs, which remained in place for 2 or 4 weeks. Following euthanasia, half of the specimens were subjected to biomechanical testing (torque to interface failure) and the other half were processed for histomorphologic and histomorphometric (%BIC) assessments. Statistical analyses were performed by one-way analysis of variance at the 95% confidence level and the Tukey post hoc test for multiple comparisons. Results: At 4 weeks, the DAE surface presented significantly higher mean values for torque to interface failure overall. A significant increase in %BIC values occurred for both groups over time. For both groups, bone formation through the classic appositional healing pathway was observed in regions where intimate contact between the implant and the osteotomy walls occurred immediately after implantation. Where contact-free spaces existed after implantation (healing chambers), an intramembranous-like healing mode with newly formed woven bone prevailed. Conclusions: In the present short-term evaluation, no differences were observed in BIC between groups; however, an increase in biomechanical fixation was seen from 2 to 4 weeks with the DAE surface. Keywords: animal study, bone-to-implant contact, dental implants, implant design, surface properties, torque

Purpose: This study evaluated the effect of severe magnesium (Mg) dietary deficiency on systemic bone density and biomechanical resistance of bone tissue to the removal torque of osseointegrated implants. Materials and Methods: The sample consisted of 45 rats; each received a titanium implant in their tibial metaphysis. After 60 days, the animals were divided into three groups (n = 15) according to their dietary Mg: the control group received the recommended content of Mg, group Mg1 received a 75% reduction in dietary Mg content, and group Mg2 was fed a diet with a 90% reduction in Mg content. Animals were sacrificed 150 days after implant placement. Serum concentrations of Mg were measured and the effect of Mg deficiency on systemic bone density was evaluated by densitometry of the lumbar vertebrae and femur. Biomechanical characteristics were measured by resistance of the bone tissue to removal of the implants. Results: Lower Mg serum concentrations were found for the Mg1 and Mg2 groups; however, densitometric analysis and torque evaluations showed a statistically significant difference only in the Mg2 group (P .05). There was a statistically significant difference in removal torque between the Mg2 group and the control group. Conclusions: This study showed that a severe deficiency of Mg decreased the systemic bone density and removal torque of osseointegrated implants. Keywords: bone mineral density, dental implants, magnesium deficiency, rats, removal torque