PURPOSEVeneering porcelain might be delaminated from underlying zirconia-based ceramics. The aim of this study was the evaluation of the effect of different surface treatments and type of zirconia (white or colored) on shear bond strength (SBS) of zirconia core and its veneering porcelain.MATERIALS AND METHODSEighty zirconia disks (40 white and 40 colored; 10 mm in diameter and 4 mm thick) were treated with three different mechanical surface conditioning methods (Sandblasting with 110 µm Al2O3 particle, grinding, sandblasting and liner application). One group had received no treatment. These disks were veneered with 3 mm thick and 5 mm diameter Cercon Ceram Kiss porcelain and SBS test was conducted (cross-head speed = 1 mm/min). Two and one way ANOVA, Tukey's HSD Past hoc, and T-test were selected to analyzed the data (α=0.05).RESULTSIn this study, the factor of different types of zirconia ceramics (P=.462) had no significant effect on SBS, but the factors of different surface modification techniques (P=.005) and interaction effect (P=.018) had a significant effect on SBS. Within colored zirconia group, there were no significant differences in mean SBS among the four surface treatment subgroups (P=0.183). Within white zirconia group, "Ground group" exhibited a significantly lower SBS value than "as milled" or control (P=0.001) and liner (P=.05) groups.CONCLUSIONType of zirconia did not have any effect on bond strength between zirconia core and veneer ceramic. Surface treatment had different effects on the SBS of the different zirconia types and grinding dramatically decreased the SBS of white zirconia-porcelain.

One of the main goals of prosthetic dentistry is to reconstruct the masticatory system. Replacing missing teeth by complete or partial denture is associated with decreased bite force and patient satisfaction. The aim of the present study was to measure the maximum bite force (MBF) and to evaluate patients' satisfaction from their conventional complete dentures and their mandibular implant-supported overdentures opposed by complete denture. In this cross sectional analytical descriptive study, seventy-five 45- to 65-year-old patients were divided into 3 groups wearing: (1) conventional complete dentures for up to 6 months; (2) conventional complete dentures for 10 years or more; and (3) complete maxillary dentures opposing mandibular implant-supported overdentures. Bite force was measured by means of electronic bite force measuring device with strain gauges. Three measurements were made on each side on the first molar region and the mean values were recorded. Patient satisfaction was also recorded using questionnaires. Results were analyzed by analysis of variance (ANOVA), t test, chi-square, and Pearson correlation test. The mean MBF for the first, the second, and the third group was, respectively, 5.65 +/- 1.46 kgf, 7.01 +/- 2.1 kgf, and 12.22 +/- 27 kgf. The difference between MBF in patients with overdentures and in patients with conventional complete dentures was statistically significant (P = .001). Patient satisfaction with mandibular implant-supported overdentures was recorded as "great." Results indicated MBF in the patients with mandibular implant-supported overdentures was significantly higher than that of patients with conventional complete dentures. This difference may indicate the important role of dental implants in the improvement of bite force and chewing efficiency and therefore patients' satisfaction.

A microgap between implant and abutment can lead to mechanical and biological problems such as abutment screw fracture and peri-implantitis. The aim of this study was to evaluate microgap size and microbial leakage in the connection area of 4 different abutments to ITI implants. In this experimental study, 36 abutments in 4 groups (including Cast On, Castable, Solid, and Synocta abutments) connected to Straumann fixtures (with their inner part inoculated with bacterial suspension) and microbial leakage were assessed at different times. The size of the microgap in 4 randomized locations was then measured by scanning electron microscope. The data were analyzed by SPSS software and by 1-way variance statistical test, Kruskal-Wallis, and their supplementary tests (Mann-Whitney HSD and Tukey's; α = .05) at the next step. The effect of using different types of abutments was significant on the mean microgap size (P < .001) and on the mean number of leaked colonies (CFU/mL) through the connection area of the implant and abutment within the first 5 hours of the experiment (P = .012); however, it did not significantly influence microleakage at 24 hours, 48 hours, and 14 days (P = .145). Using Synocta abutments compared with Solid abutments will not provide us with more accommodation, and vice versa. Using Solid and Synocta abutments can significantly decrease the microgap size; however, Cast On abutments do not show a significant difference in terms of microgap compared with Castable abutments. Microleakage in the connection area is comparable for these 4 abutments.

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Macrodesign of ILS leads to better primary stability and stress distribution. Maximum stress around Xive was less.