Zygomatic implants are becoming an ideal treatment approach for implant-supported prosthesis treatment developed for the atrophic maxilla. This study aims to evaluate the amount and distribution of stress in implants and peri-implant bone using different implant-supported prosthesis configurations in Aramany Class I maxillary defects through 3-dimensional finite element analysis. A 3-dimensional finite element model of the Aramany class I defect was created. Three different implant-supported prostheses were modelled: model 1: 1 zygomatic implant and 3 dental implants, model 2: 1 zygomatic implant and 2 dental implants, and model 3: 2 zygomatic implants. Vertical and horizontal loads of 150 N were applied in 6 different ways to the defected and non-defective areas. Maximum principal stress and von mises stresses in the bone surrounding the implants were evaluated. When all loading conditions were evaluated with both porcelain layer on Co-Cr framework and acrylic layer on acrylic framework, the highest maximum principal stress value was observed in Model 3. In contrast, the lowest value was observed in Model 1. The highest maximum principal stress occurred when a horizontal load was applied simultaneously to both the defective and non-defective areas. In contrast, the lowest value was observed when a vertical load was applied to the non-defective area. The von Mises stress values were found to be similar across all models when both restoration materials were used. Based on the results of this study, it can be concluded that increasing the number of implants in the non-defective area reduces the highest stress value while using acrylic as a restoration material slightly increases the stress value.

The purpose of this study was to evaluate the effect of different polymerization cycles on the flexural strengths and microhardness of two denture base materials (Meliodent and Paladent). Heat-polymerized acrylic resin specimens (65.0 mm long×10.0 mm wide×2.5 mm in height) were prepared using different short and long polymerization cycles. After the specimens had been polymerized, they were stored in distilled water at 37±1°C for 24 h. Flexural strength test was performed at a cross-head speed of 5 mm/min and Vickers microhardness was measured. Data were analyzed with a 1-way analysis of variance followed by Tukey test, and Student t-test (α=0.05). The flexural strengths and microhardness were significantly different between Meliodent and Paladent (p<0.05). Significant differences were found among the polymerization cycles in terms of flexural strengths and microhardness (p<0.05). Polymerization with G cycle may be suggested for Meliodent and H cycle may be suggested for Paladent.

The aim of study was to evaluate the effects of multiple firings on the microstructures of zirconia and two ceramics. Vita VM9 (VMZ) and Cerabien ZR (C-Z) ceramics on a zirconia framework and zirconia without veneering ceramic (WO-Z) were evaluated. Firing methods included firing two, five, and ten times (n=10). The effects of multiple firings on the surface hardness of the materials were evaluated using a Vickers hardness (HV) tester. Data were analyzed by two-way ANOVA and Tukey's test (α=0.05). After firing five and ten times, the hardness of VM-Z and C-Z increased significantly (p0.05). In the XRD analysis, zirconia had similar tetragonal (t)-monoclinic (m) phase transformations of Y-TZP after the different firing times. Clinically, multiple firings did not affect the microstructure of zirconia, but the structures of the two ceramics were affected.

Alkurt M, et al. J Adv Prosthodont. 2016 Oct;8(5):380-387. https://doi.org/10.4047/jap.2016.8.5.380

This study was aimed to observe the relationship between the different surface treatments and the bond strength of both composite based adhesive cement and zirconia ceramic. Thirty-two zirconia ceramic discs were fabricated by following the instructions of manufacturer (5 × 5 × 1.5 mm). Four subgroups were obtained from the specimens according to the specified surface treatments respectively: (a) C: control groups: no treatment; (b) SB: sandblasting with 125 μm aluminum oxide particles for 10 s; (c) SC: silica coating for 10 s; (d) Nd :YAG laser . The composite resin specimens Panavia F and Clearfil SA were introduced and polymerized to the treated bonding areas. Afterwards the specimens were stored in distilled water at 37 °C during 24 h, and the shear test was applied. The data were statistically analyzed by ANOVA and Duncan tests. The bond strength was stated significantly higher in silica coating/Panavia F group (23.35 MPa). The lowest bond strength was stated in control groups cemented with Clearfil SA (12.25 MPa). As a result it was determined that the bond strength has affected the both surface treatments and cement types (p < 0.001). The silica coating –treated zirconia ceramic recorded a significant increase in mean bond strength values.

Purpose: The aim of this study was to assess the intra-pulpal temperature changes in adhesive resin cements during polymerization. Materials and Methods: Dentin surface was prepared with extracted human mandibular third molars. Adhesive resin cements (Panavia F 2.0, Panavia SA, and RelyX U200) were applied to the dentin surface and polymerized under IPS e.max Press restoration. K-type thermocouple wire was positioned in the pulpal chamber to measure temperature change (n = 7). The temperature data were recorded (0.0001 sensible) and stored on a computer every 0.1 second for sixteen minutes. Differences between the baseline temperature and temperatures of various time points (2, 4, 6, 8, 10, 12, 14, and 16 minute) were determined and mean temperature changes were calculated. At various time intervals, the differences in temperature values among the adhesive resin cements were analyzed by two-way ANOVA and post-hoc Tukey honestly test (α = 0.05). Results: Significant differences were found among the time points and resin cements (P < 0.05). Temperature values of the Pan SA group were significantly higher than Pan F and RelyX (P < 0.05). Conclusion: Result of the study on self-adhesive and self-etch adhesive resin cements exhibited a safety intra-pulpal temperature change.