Thiago de Almeida Prado Naves Carneiro

Micro-leakage at the implant-abutment interface with different tightening torques in vitro

Objectives This study evaluated the microleakage at the implant/abutment interface of external hexagon (EH) implants and abutments with different amounts of bacteria and tightening torques. Material and Methods A bacterial suspension was prepared to inoculate the implants. The first phase of this study used nine EH implants and abutments that were divided into three groups with different amounts of bacterial suspension (n=3): V0.5: 0.5 µL; V1.0: 1.0 µL e V1.5: 1.5 µL, and tightened to the manufacturers recommended torque. The second phase of this experiment used 27 assemblies that were similar to those used in the first phase. These samples were inoculated with 0.5 µL of bacterial suspension and divided into three groups (n=9). T10: 10 Ncm; T20: 20 Ncm and T32: 32 Ncm. The samples were evaluated according to the turbidity of the broth every 24 hours for 14 days, and the bacteria viability was tested after that period. The statistical evaluation was conducted by Kruskal-Wallis testing (p<.05). Results During the first phase, groups V1.0 and V1.5 was presented with bacterial contamination in all samples after 24 h. During the second phase, two samples from group T10 and one from T20 presented positive results for bacterial contamination. Different amounts of bacterial solution led to overflow and contamination during the first 24 h of the experiment. The tightening torques did not statistically affect the microleakage in the assemblies. However, the group that was tightened to 32 Ncm torque did not show any bacterial contamination. Conclusion After 14 days of experimentation, the bacteria were proven to remain viable inside the implant internal cavity.

Micrometric precision of prosthetic dental crowns obtained by optical scanning and computer-aided designing/computer-aided manufacturing system

Abstract. The current study evaluated prosthetic dental crowns obtained by optical scanning and a computer-aided designing/computer-aided manufacturing system using micro-computed tomography to compare the marginal fit. The virtual models were obtained with four different scanning surfaces: typodont (T), regular impressions (RI), master casts (MC), and powdered master casts (PMC). Five virtual models were obtained for each group. For each model, a crown was designed on the software and milled from feldspathic ceramic blocks. Micro-CT images were obtained for marginal gap measurements and the data were statistically analyzed by one-way analysis of variance followed by Tukey’s test. The mean vertical misfit was T=62.6±65.2  μm; MC=60.4±38.4  μm; PMC=58.1±38.0  μm, and RI=89.8±62.8  μm. Considering a percentage of vertical marginal gap of up to 75 μm, the results were T=71.5%, RI=49.2%, MC=69.6%, and PMC=71.2%. The percentages of horizontal overextension were T=8.5%, RI=0%, MC=0.8%, and PMC=3.8%. Based on the results, virtual model acquisition by scanning the typodont (simulated mouth) or MC, with or without powder, showed acceptable values for the marginal gap. The higher result of marginal gap of the RI group suggests that it is preferable to scan this directly from the mouth or from MC.

A conservative approach to retrieve a fractured abutment screw – Case report

INTRODUCTION Regarding implant-supported prostheses, the most reported types of complications are related to loosening or fracturing of abutment or prosthesis screws. This case report shows a series of procedures that allowed a conservative solution for a fractured screw. It avoided removing the implant and also allowed the same prosthesis to be used after guided-drilling the fractured screw and re-tapping the implant internal threads. The same prosthesis was replaced immediately after the procedure. PATIENT A 67-year-old male patient, who had a fractured abutment screw of the lower left first molar implant. The patient decided for the conservative treatment option and an attempt was made to remove the fractured screw. DISCUSSION Parafunctional habits can generate excessive occlusal forces, which are risk factors associated with loosening and fracturing implant screws and even the fixtures themselves. This case report focus on the probable causes, difficulties and risks associated with this procedure and it also discusses the alternative approaches. CONCLUSION The purposed treatment allowed a time and money saving resolution for fractured abutment screws.

Micro-CT analysis of in-office computer-aided designed/computer-aided manufactured dental restorations

Abstract Purpose: The current study evaluated two different materials, using micro-CT to compare the marginal gap of feldspathic ceramic (V) and resin nano-ceramic (L) crowns obtained by two different computer-aided design/computer-aided manufacturing (CAD/CAM) systems, CEREC CAD/CAM system and E4D Technologies. Methods: A human lower left first premolar was mounted on a typodont model and prepared for an all-ceramic crown. Two groups (n = 5) were divided based on the system for obtaining the crowns and the material used for it (V and L). Micro-CT images were obtained for marginal gap measurements of each crown, and the data were statistically analysed by one-way analysis of variance followed by Tukey’s post hoc test for pairwise comparisons (α¼ 0.05). Results: There were no statistically significant differences between marginal gap of groups V and L (p = 0.473). The mean and standard deviation for the vertical misfit was V = 62.6 (65.2) and L = 66.5 (59.0). For the horizontal misfit, the values were divided into three groups: underextension (L = 20.8%) and (V = 54.6%), equally extended (L = 16.9%) and (V = 36.9%) and overextension (L = 62.3%) and (V = 8.5%). Conclusion: The results revealed no difference in the marginal fit of crowns produced by different materials and different chairside CAD/CAM systems. Both are considered clinically acceptable according to all cited classifications.