The use of separation rings with sectional matrices provides superior contacts when placing Class II RCRs.

Objectives:This study was carried out to examine the effect of application of four different disinfecting agents on the micro-shear bond strength (μ-SBS) of an etch-and-rinse and self-etch adhesive systems.Materials and Methods:One hundred flat dentin surfaces of human molars were produced by wet grinding the buccal surfaces. Specimens were randomly assigned to five groups according to the disinfectant used: Group I: Control (no disinfectant); Group II: 5.25% sodium hypochlorite based; Group III: 2% chlorhexidine based (Consepsis), Group IV: 0.1% benzalkoniumchloride based (Tubulicid red) and Group V: 3% doxycycline based (Biopure, MTAD). Specimens were bonded using either Adper Single Bond 2 or Clearfil S3 Bond, which were employed according to the manufacturer's instructions. Resin composite microcylinders were bonded using Tygon® tubes for μ-SBS testing. The modes of failure were noted after visual examination using a binocular stereomicroscope at ×25 magnification. Failures were classified as adhesive, or mixed. μ-SBS results were analyzed using two-way ANOVA followed by Tukey's post-hoc test.Results:Dentin disinfectants tested significantly negated the bonding of Adper Single bond 2 and the groups were ranked; Group I > Group V = Group IV > Group II = Group III, meanwhile they enhanced significantly the μ-SBS values upon using Clearfil S3 Bond and were ranked; Group II > Group III = Group IV = Group V > Group I. Most failures were adhesive with the Adper single bond adhesive system. Mixed modes of failure were evident with Clearfil S3 bond.Conclusions:The disinfectants tested should not be used with Adper Single Bond 2 when applied before the etching step, However they could be used safely prior to bonding with Clearfil S3 Bond.

SUMMARY Objective The purpose of this study was to compare proximal contact tightness (PCT) of MOD resin composite restorations placed with different matricing protocols. Methods Forty-five ivorine lower right first molars with standardized MOD cavities were equally divided into three groups according to the restoration protocol. Group 1: Sectional matrix (Standard matrix, Palodent, Dentsply) secured with a wedge (Premier Dental Products Co.) and separation ring (BiTine I, Palodent, Dentsply, York, PA, USA) was used to restore the mesial surface first and then removed and repeated for the distal surface. Group 2: Identical to group 1, but separation rings were placed at both the mesial and distal sides (BiTine I+II, Palodent) prior to restoration. Mesial surface was restored followed by distal. Group 3: Walser matrix (O-form, Dr. Walser Dental GmbH) was used. Following composite resin restoration, PCT was measured using the tooth pressure meter. Data were analyzed using analysis of variance and a Tukey post hoc test (p<0.05). Results PCT values for mesial contacts were 2.99 ± 0.47N for group 1, 4.57 ± 0.36N for group 2, and 3.03 ± 0.79N for group 3. For the distal contacts, the values were 4.46 ± 0.44N for group 1, 5.12 ± 0.13N for group 2, and 0.76 ± 0.77N for group 3. Significantly tighter contacts were obtained for mesial and distal contacts for group 2 compared to groups 1 and 3 (p<0.05). For groups 1 and 3, mesial contacts were not significantly different (p=0.993), while distal contacts for group 1 were significantly tighter (p<0.001). Conclusion Within the limitations of this study, tighter contacts can be obtained when sectional matrices and separation rings are applied to both proximal surfaces prior to placement of the resin composite in MOD cavities.

Objective: to evaluate the internal fit of all ceramic restoration fabricated by two CAD/CAM milling systems using cone beam CT (CBCT). Materials and methods:A total number of 20 all ceramic restorations were manufactured in this study, and were equally divided into two main groups (n=10) according to the type of CAD/ CAM system used in the manufacturing process. Group I (Cerec in-lab system) and group II (Everest system) using the e.max CAD blocks specified for each milling system. specially designed stainless steel die was manufactured with specified dimensions. The die was scanned, the all ceramic restoration was designed and milled according to the different CAD/CAM milling systems used, and then crystallization procedure was carried. Duplication of the metal die into epoxy resin dies was performed and the final all ceramic restorations were the placed over the epoxy resin dies and examined for internal gap measurement using cone beam computed tomography (CBCT). Numerical data were explored for normality using Kolmogorov-Smirnov test of normality. Normally distributed (parametric data), were presented as mean, standard deviation and were compared between groups using independent t test. Non-parametric data were compared between groups using Mann Whiney U test. Gingival, axial and occlusal segments were compared using Friedman test and Wilcoxon signed rank test. The significance level was set at p < 0.05. Statistical analysis was performed with SPSS 18.0 for windows.Results: Comparison between groups using the mean of the 3 successive sections in buccolingual section revealed that a higher mean value was recorded in Cerec for each of the gingival, axial and occlusal segments, with no statistically significant difference between groups (p=0.138, p=0.06, p=0.276 respectively), while in mesio distal section a higher mean value was recorded in Cerec in the gingival and axial segments, with no significant difference between groups (p=0.296,

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