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Purpose: Strains transferred to the supporting simulated bone structure by implant-supported full-arch fixed dental prostheses (FAFDPs) were analyzed by digital image correlation (DIC). Materials and Methods: Polyurethane models were made using 3.75 × 11–mm implants and divided into the following groups with different implant numbers and design: EH5 (five implants/external hexagon), MT5 (five implants/internal taper), EH4 (four implants/external hexagon), and MT4 (four implants/internal taper). Both qualitative and quantitative (one-way analysis of variance [ANOVA] statistical comparison) analyses were performed by the DIC method after the application of a 250-N load in the central fossa of the mandibular first molar. Different regions of interest were selected in the polyurethane model for comparison between groups. Results: Compressive strains were found in the cervical region of the models, and tensile strains were found in the apical region of the models. Significant differences were found in the different analyzed regions of interest for the different number of supporting implants and implant designs (P < .05). Conclusion: Groups with five implants showed more regions with less strain concentration compared to groups with four implants, but strain distribution was similar between groups. The different tested implant designs showed similar strain concentration and distribution to the supporting structures. [ABSTRACT FROM AUTHOR]

Purpose: To study the force used for tightening tapered one-piece prosthetic abutments and their influence on the removal torque value and stress level of the prosthetic abutment after cyclic loading. Materials and Methods: Fourteen implants and prosthetic abutments were divided into two groups (n = 7): G1, 20 Ncm; and G2, 32 Ncm (manufacturer recommended). A 20-mm T-shaped horizontal bar was adapted to the abutments. A 12-Hz cyclic loading was applied to the specimens in an electrodynamic testing system with the maximum number of cycles set to 106. Specimens were inclined by 15 degrees from the vertical axis, and a 5-mm off-center vertical load was applied to generate a combination of bending and torquing moments on the tapered connections. Progressive loads (from 164.85 to 362.85 N) were applied when the previous sample survived 106 cycles. The paired t test compared the screw removal torque with the initial tightening torque for each group (α = .05). A finite element analysis (FEA) of the mechanical testing analyzed the regions of stress concentration. Results: No specimens failed after 106 cyclic loadings. The mean screw removal torque for both groups was similar to the initial abutment torque value applied for each group (G1, 20.36 ± 8.73 Ncm; and G2, 35.61 ± 6.99 Ncm) (P > .05). FEA showed similar stress behavior for both groups in the study despite the different simulated screw preloads (G1: 200 N; G2: 320 N). The coronal region of the implant body presented the highest strain values in both groups. Conclusion: Tightening tapered one-piece prosthetic abutments at 20 and 32 Ncm maintains a stable connection after cyclic loading. The stresses generated by the different tightening forces during cyclic loading are highest at the coronal level of the connection. [ABSTRACT FROM AUTHOR]

This study evaluated the anatomical factors that influence the virtual planning of zygomatic implants by using cone-beam computerized tomography (CBCT) scans. CBCT scans of 268 edentulous patients were transferred to specialized implant planning software for the following measurements: maxillo-sinus concavity size (small, medium, and large), zygoma width, implant insertion angle, implant length, and implant apical anchorage. Concavity sizes found were as follows: 34.95% small, 52.30% medium, and 7.35% large. The mean insertion angle was 43.2 degrees, and the average implant apical anchorage was 9.1 mm. The most frequent implant length was 40 mm. Significant differences were found when the different types of concavities in relation to the installation angle, the distance of the apical portion of the implant in contact with the zygomatic bone, and the lateral-lateral thickness of the zygomatic bone were compared (P <.001). Medium-sized maxillary sinus concavity presented greater apical anchorage of the implant (9.7 mm) and was the most frequent type (52.30%). The zygomatic bone is a viable site for zygomatic fixtures, and the use of specialized implant planning software is an important tool to achieve predictable outcomes for zygomatic implants and allows good visualization of the relation between implants and anatomical structures. [ABSTRACT FROM AUTHOR]

Purpose: This study compared the vertical microgaps of milled zirconia and cobalt-chromium (Co-Cr) implant-supported fixed dental prosthesis frameworks to those seen in one-piece frameworks cast with different techniques. Materials and Methods: Two threaded implants were used to simulate the rehabilitation of a maxillary partially edentulous space from the second premolar to the second molar. Three-unit screw-retained prosthetic frameworks were fabricated and divided into the following groups (n = 10 in each group): 1 = cast in Co-Cr using burnout cylinders; 2 = cast in Co-Cr using cast-on Co-Cr cylinders; 3 = one-piece cast in Co-Cr using a passive fitting technique; 4 = milled Co-Cr framework; 5 = milled zirconia framework. The microgap was measured under an optical microscope at ×25. Readings were made with one screw tightened and with both screws tightened. Data were submitted to statistical analysis to enable comparison between groups (α = .05). Results: All frameworks presented microgaps less than 70 μm under all reading conditions, except for group 1 with the readings made on the side opposite the tightened side (124.22 μm). With one screw tightened, the microgap on the tightened side was significantly smaller in groups 2, 3, and 4. On the opposite side, groups 3, 4, and 5 presented significantly smaller microgaps compared to the other groups. When both screws were tightened, the microgap was significantly smaller in groups 2, 3, and 4. Conclusion: One-piece cast frameworks associated with a passive fitting technique and milled Co-Cr frameworks presented smaller microgaps than the other fabrication methods and materials that were tested. [ABSTRACT FROM AUTHOR]

This study compared the vertical misfit of 3-unit implant-supported nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloy and commercially pure titanium (cpTi) frameworks after casting as 1 piece, after sectioning and laser welding, and after simulated porcelain firings. The results on the tightened side showed no statistically significant differences. On the opposite side, statistically significant differences were found for Co-Cr alloy (118.64 μm [SD: 91.48] to 39.90 μm [SD: 27.13]) and cpTi (118.56 μm [51.35] to 27.87 μm [12.71]) when comparing 1-piece to laser-welded frameworks. With both sides tightened, only Co-Cr alloy showed statistically significant differences after laser welding. Ni-Cr alloy showed the lowest misfit values, though the differences were not statistically significantly different. Simulated porcelain firings revealed no significant differences. [ABSTRACT FROM AUTHOR]

Objective: This retrospective study evaluated the use of a single miniplate for the treatment of mandibular angle fractures (MAF).Methods: Fifty patients with 53 MAF were treated by open reduction and internal fixation with the use of a single miniplate and were analyzed in this study.Results: Five patients with MAF had postoperative complications that required additional procedures. Three patients had postoperative infection, one patient complained of malocclusion in the first postoperative week, and one patient had miniplate exposure three months after surgery. Every additional procedure was performed in the office under local anesthesia without disruption of the initial fracture treatment. Postoperative maxillomandibular fixation (MMF) was performed in four patients. Treatment of MAF using a single miniplate was effective, with low morbidity and with low rates of postoperative complications. MAF can be treated without MMF, and stability is improved when long miniplates are used.Conclusions: The use of a single miniplate is therefore encouraged. However, postoperative MMF should be considered with the presence of little contact between bone segments, malocclusion, or extensive tooth loss. [ABSTRACT FROM AUTHOR]

Objectives This randomized clinical trial analyzed crestal bone changes and soft tissue dimensions surrounding implants with an internal tapered connection placed in the mandible anterior region at different depths (equicrestal and subcrestal). Materials and methods Eleven edentulous patients (five implants per patient) were randomly divided in a split-mouth design: G1, 28 equicrestal implants; and G2, 27 subcrestal implants. All implants were immediately loaded. Correlation between keratinized tissue width ( KTW) and vertical mucosa thickness ( MT) with soft tissue recession was analyzed. Intraoral radiographs were used to evaluate crestal bone changes. Patients were assessed immediately, 4-, and 8-months after implant placement. Rank-based ANOVA-type statistical test was used for comparison between groups (α = 0.05). Results Fifty-five implants (G1 = 28 and G2 = 27) were assessed in 11 patients. Implant survival rate was 100% for both groups. Both tested implant placement depths presented similar crestal bone loss ( P > 0.05). Significant crestal bone loss for each group was found in the different measurement times (T4 and T8) ( P < 0.05). Implant placement depths, KTW, and vertical MT had no effect on soft tissue recession ( P > 0.05). Conclusions Different implant placement depths do not influence crestal bone changes. Soft tissue behavior is not influenced by different implant placement depths or by the amount of keratinized tissue. [ABSTRACT FROM AUTHOR]

Purpose It is still unclear whether four, six, or more implants should be used when restoring fully edentulous maxillae. This research evaluated the in vitro screw torque loss of zirconia frameworks supported by six implants and cantilevered zirconia frameworks supported by four implants. Materials and Methods Computer aided design/computer-assisted machining was used to fabricate 10 one-piece frameworks. Standardized pressable porcelain crowns were fabricated and luted to the frameworks. Specimens were divided into two groups (n = 5): AO4, cantilevered 12-unit full-arch fixed dental prosthesis supported by four implants; AO6, 14-unit supported by six implants. An opposing mandibular dental arch was fabricated with bis-acrylic composite resin. Specimens were submitted to 200 N underwater cyclic load at 2-Hz frequency for 1 × 106 cycles in a controlled 37°C temperature. A digital torque gauge assessed the initial and postload screw removal torque. Linear mixed-effects model was used for statistical analysis (α = 0.05). Results Significant screw torque loss was found for AO6 after cyclic loading (before: 36.20%/after: 52.82%; p < 0.05). Group AO6 (36.20%) presented lower preload loss before the cyclic loadings compared with AO4 (60.10%) ( p < 0.05). Conclusions Cyclic loading and lower implant-to-replaced-units ratio do not seem to compromise screw stability compared with higher implant-to-replaced-units ratio; however, a steep drop in preload was found before cyclic loading for both groups. [ABSTRACT FROM AUTHOR]