Influence of Torque on Platform Deformity of the Tri-Channel Implant: Two- and Three-Dimensional Analysis Using Micro-Computed Tomography.

Background and Objectives: The insertion of the dental implant in the bone is an essential step in prosthetic rehabilitation. The insertion torque has the potential to distort the prosthetic platform, which can cause future biomechanical problems with the continuous action of occlusal forces. The aim of this study is to evaluate different insertion torques in the deformation of tri-channel platform connections through two- and three-dimensional measurements with micro-CT. Materials and Methods: A total of 164 implants were divided into groups (platform diameter and type): 3.5, 3.75, and 4.3 mm NP (narrow platform), and 4.3 mm RP (regular platform). Each implant-platform group was then divided into four subgroups (n = 10) with different torques: T45 (45 Ncm), T80 (80 Ncm), T120 (120 Ncm), and T150 (150 Ncm). The implant-abutment-screw assemblies were scanned and the images obtained were analyzed. Results: A significant difference was observed for the linear and volume measures between the different platforms (p < 0.01) and the different implant insertion torques (p < 0.01). Qualitative analysis suggested a higher deformation resistance for the 3.75 NP compared to the 3.5 NP, and RP was more resistant compared to the NP. Conclusions: The 0.25 mm increment in the implant platform did not increase the resistance to the applied insertion torques; the 4.3 mm implant was significantly stronger compared to the 3.5 mm implant; and the proposed micro-CT analysis was considered valid for both the 2D and 3D analyses of micro-gaps, qualitatively and quantitatively.

Bond strength of adhesive systems to sound and demineralized dentin treated with bioactive glass ceramic suspension.

OBJECTIVE: The objective of this study was to evaluate the effect of a Biosilicate®, associated with dentin adhesive system, on microtensile bond strength (µTBS) to sound and demineralized dentin. MATERIALS AND METHODS: Eighty sound-extracted molars had their middle occlusal dentin exposed. In forty teeth, dentin was artificially demineralized (pH cycling). Sound and demineralized dentin teeth were separated into four groups (n = 10), according to the substrate treatment before restoration: Group 1-total-etching adhesive Adper TM Single bond 2 (ASB) + Biosilicate®, Group 2-ASB (without Biosilicate®), Group 3-AdheSE self-etching adhesive system (AdSE) + Biosilicate®, and Group 4-AdSE (without Biosilicate®). Each tooth was restored with a hybrid composite and stored in water at 37 °C for 6 months. After water aging, teeth were cut in sticks (≈ 1 mm2 cross-sectional area) and all samples were submitted to µTBS test. The fracture modes of the samples were analyzed by stereomicroscopy. The representatively fractured samples were observed by scanning electron microscopy. Representative samples of each group were analyzed on energy dispersive X-ray spectrometry (EDX). The µTBS and Ca-P ratio values were analyzed by 2-way ANOVA, Bonferroni, and Tukey test, respectively, p < .05. RESULTS: ASB + Biosilicate® presented the highest µTBS values (p < .05), and lowest µTBS values (p < .05) were found in AdSE Group. There was no statistical difference (p < .05) on µTBS when substrates were compared, except for Group 2. The fracture pattern analysis showed prevalence of adhesive fractures in all groups. CONCLUSION: Biosilicate® enhanced bond strength of self-etching and etch-and-rinse adhesives to sound and demineralized dentin. CLINICAL RELEVANCE: Bioactive glass ceramic suspension could be recommended to be used to improve the dentin bond strengths of the total-etching and self-etching adhesives after acid-etching and priming.

Color Stability and Surface Roughness of Composite submitted to Different Types and Periods of Finishing/Polishing: Physical Properties of Composites.

AIM: The aim of this study was to evaluate the influence of accelerated artificial aging (AAA) on color stability (AE) and surface roughness of composite submitted to different systems and periods of finishing/polishing. MATERIALS AND METHODS: A Teflon matrix was used to fabricate 60 specimens that were separated into four groups, according to the finishing/polishing system: G1: no polishing; G2: abrasive papers; G3: rubber polishing disks; and G4: G2 + G3. Polishing was performed at three different time intervals (n = 6): immediately (Im), 24 hours (24 hours) and 7 days (7 day) after specimen fabrication. Initial color and surface roughness readouts were taken. Afterwards, specimens were submitted to AAA (480 hours) and new readouts were taken. RESULTS: Results demonstrated that G2 (7 day) presented lower AE, statistically different from G1 and G4 (7 days) (two-way analysis of variance (ANOVA), Bonferroni, p < 0.05). CONCLUSION: Regarding roughness, there was no difference among groups and periods. Polishing performed with abrasive papers, 7 days after performing the restoration, promoted less color alteration. CLINICAL SIGNIFICANCE: Most of composite restorations are replaced within a period shorter than 5 years due to esthetic failure, and correct finishing and polishing procedures are fundamental to avoid these problems.