Effect of Ferrule Location on Fracture Resistance of Maxillary Premolars: An In Vitro Study.

Objectives: The present study aimed to assess the effect of ferrule location on fracture resistance of maxillary premolars. Materials and Methods: A total of 72 extracted human maxillary premolars were selected and randomly assigned to six groups (n = 12 in each) considering ferrule location: circumferential ferrule (CF), without ferrule (WF), buccal ferrule (BF), lingual ferrule (LF), mesial ferrule (MF), and buccal-lingual ferrule (BLF). Cast posts were cemented into the prepared post spaces. Following conventional impression, Ni-Cr crowns were cemented to the specimens. After thermocycling (5,000 cycles, 5-55°C), the specimens were loaded at 45° in a universal testing machine until fracture. Data were analyzed with one-way ANOVA, Kolmogorov-Smirnov, and Tamhane tests. Results: The maximum and minimum mean fracture resistance were related to the CF (1,143.84 N) and WF (514.89 N) groups, respectively, (P = 0.039). Fracture resistance in the BF (933.67 N) and BLF (874.01 N) groups was significantly higher than in the MF group (617.54 N) (P = 0.001). There was no significant difference between the MF, LF (722.89 N), and WF groups in terms of fracture resistance (P > 0.05). Conclusion: Teeth with CF showed maximum fracture resistance. The location of the ferrule effects on the fracture resistance of maxillary premolars and also the mode of failure.

Bacterial microleakage in endodontically treated teeth following two methods of postspace preparation at two-time intervals: An in vitro study.

Aims: The goal of this study was to analyze the bacterial microleakage following two methods (heat vs. rotary) of postspace preparation after two-time intervals (immediate vs. 1 week later). Setting and Design: In vitro-comparative study. Materials and Methods: Eighty-two single-rooted teeth were decoronated at the cementoenamel junction. Root canals were prepared using rotary files. After root canal obturation, specimens were randomly allocated to 4 experimental groups based on the method of postspace preparation (heat or peeso reamer) and time interval (immediate or 1 week later) (n = 18). Group 1: Peeso reamer-immediate, Group 2: Heat-immediate, Group 3: Peeso reamer-1 week later, Group 4: Heat-1 week later. 10 specimens were considered as positive and negative controls (n = 5 each). Custom-made dual-chamber devices were used to appraise the bacterial microleakage for 60 days. Statistical Analysis Used: Data were analyzed with Chi-Square and Log-Rank tests and Cox regression. Results: All through the experimental period, there was no significant difference (P = 0.41) between the studied groups. Groups 2 and 4 had the highest microleakage and the lowest survival rate (55.56% ± 11.71%). Group 1 showed the lowest microleakage and the highest survival rate (77.8% ± 9.80%). Conclusions: The applied techniques for postspace preparation and the time intervals (neither independently nor simultaneously) showed no significant difference in the field of bacterial leakage.

Comparison of Bond Strength in the Different Class of Resin Cements to Cast and CAD/CAM Co-Cr Alloys.

OBJECTIVES: Despite the widespread use of resin cements in cementing dental restorations, their bond strength to CAD/CAM base metal alloys is not widely studied. This study aimed to evaluate the microshear bond strength (µSBS) between cobalt-chrome (Co-Cr) alloys fabricated using casting or CAD/CAM methods with three types of resin cements. MATERIALS AND METHODS: Fifty Co-Cr blocks were prepared with CAD/CAM or casting technique. Specimens were divided using primer or not and bonded to three types of resin cements: Panavia F2, RelyX Unicem, and Duo-Link. The differences between the mean µSBS values were analyzed using the two-way ANOVA test and Tukey analysis (α = 0.05). The mode of failure was evaluated using a stereomicroscope. In addition, the specimens were examined by scanning electron microscopy (SEM) based on two received signals: backscattered electrons (SEB) and secondary electrons (SEs). One intact alloy specimen in each group was analyzed by energy-dispersive X-ray spectroscopy (EDX). RESULTS: Most of the specimens in the no-primer group were prematurely debonded. Statistical analyses showed that the interaction between the alloy substrate and cement type was significant (p=0.001). The bond strength of Panavia F2 was significantly higher than Duo-Link in the CAD/CAM group (p=0.001). SEM evaluation confirmed the difference in grain structures, while EDX showed no remarkable difference in the chemical composition of the alloy substrates. CONCLUSION: Alloy fabrication technique may influence the bond strength of resin cements. In the CAD/CAM group, cement containing MDP molecules exhibited higher strength than the etch-and-rinse one.

Effect of fluid contamination on the reverse torque values of abutment screws at implant-abutment connections.

STATEMENT OF PROBLEM: Screw loosening is still among the most important complications of dental implants. Identifying effective factors in screw loosening plays an important role in preventing this problem. PURPOSE: The purpose of this in vitro study was to assess the effect of fluid contamination on the reverse torque values (RTVs) of abutment screws at implant-abutment connections. MATERIAL AND METHODS: Five groups (9 specimens in each group) of implants were mounted in acrylic resin. Four groups of fixture screw holes were contaminated with chlorhexidine (CG), saliva (SG), blood (BG), or fluoride (FG), and a fifth group served as a control with no contamination (NC). Abutment screws were tightened by using a digital torque meter. The RTVs were recorded after thermocycling. Data were analyzed by 1-way ANOVA and the Tukey honestly significant difference test (α=.05). RESULTS: RTVs were lower in SG (13.65 ±0.91 Ncm) than NC (16.55 ±1.82 Ncm), while the values were significantly higher in CG (19.74 ±1.79 Ncm) than NC. No statistically significant difference was reported in BG (16.30 ±1.66 Ncm) and FG (15.92 ±1.82 Ncm) compared with the control group. CONCLUSIONS: RTVs were significantly reduced by saliva contamination in comparison with those of other groups. The highest RTVs were detected in CG.

Facilitation of Prosthetic Rehabilitation in Scleroderma: Case History Report.

Dental management of scleroderma patients is difficult and complicated because of compromised intraoral access. Physiotherapy may play an adjunctive and effective treatment role as described in a follow-up report on a previously documented case history.