Evaluation of Marginal and Internal Integrity of Modified Resin-Bonded Fixed Partial Dentures: An In Vitro Study

PURPOSE: The purpose of this study was to evaluate the microleakage of various types of resin-bonded fixed partial dentures (RBFPDs) after artificial aging. MATERIALS AND METHODS: Forty models with missing first molar were fabricated using artificial resin teeth and were divided into four groups: Group A, conventional RBFPDs design; Group B, modified RBFPDs design; Group C, assembled 3-piece RBFPDs design; and Group D, assembled 3-piece RBFPDs with different occlusal rest positions. Half of the specimens underwent chewing simulation process (240,000 cycles, 50 N load, 1.7 Hz) and thermocycling (temperatures 5℃~55℃, dwelling time 30 seconds) and the remaining 20 specimens didn't receive any treatment. All the specimens were immersed in 2% methylene blue solution for 24 hours to evaluate microleakage, and were sectioned at the middle part of abutment teeth. To evaluate the microleaskage, a dye penetration was calculated. RESULT: With artificial aging, cyclic loading and thermocycling, a 3-piece RBPFD and a 2-piece RBPFD using original tooth undercuts have significantly lower microleakge (P<0.05) compared to the conventional design of RBPFD and modified RBPFD. CONCLUSION: Within the limit of this experiment, the assembled RBFPDs exhibited a smaller microleakage than the conventional RBFPDs, implying that the assembled RBFPDs can be more effective for reducing the dislodgement of the RBFPDs.

Effect of Accelerated Aging on the Color Stability of Dual-Cured Self-Adhesive Resin Cements

PURPOSE: The effect of accelerated aging on color stability of various dual-cured self-adhesive resin cements were evaluated in this study. MATERIALS AND METHODS: Color stability was examined using three different brands of dual-cured self-adhesive resin cements: G-CEM LinkAce (GC America), MaxCem Elite (Kerr), and PermaCem 2.0 (DMG) with the equivalent color shade. Each resin cement was filled with Teflon mold which has 6 mm diameter and 2 mm thickness. Each specimen was light cured for 20 seconds using light emitting diode (LED) light curing unit. In order to evaluate the effect of accelerated aging on color stability, color parameters (Commission Internationale de l'Eclairage, CIE L*, a*, b*) and color differences (DeltaE*) were measured at three times: immediately, after 24 hours, and after thermocycling. The L*, a*, b* values were analyzed using Friedman test and DeltaE* values on the effect of 24 hours and accelerated aging were analyzed using t-test. These values were compared with the limit value of color difference (DeltaE*=3.7) for dental restoration. One-way ANOVA and Scheff's test (P<0.05) were performed to analyze each DeltaE* values between cements at each test period. RESULT: There was statistically signifi cant difference in comparison of color specifi cation (L*, a*, b*) values after accelerated aging except L* value of G-CEM LinkAce (P<0.05). After 24 hours, color difference (DeltaE*) values were ranged from 2.47 to 3.48 and L* values decreased and b* values increased in all types of cement and MaxCem Elite had high color stability (P<0.05). After thermocycling, color change's tendency of cement was varied and color difference (DeltaE*) values were ranged from 0.82 to 2.87 and G-CEM LinkAce had high color stability (P<0.05). CONCLUSION: Color stability of dual-cured self-adhesive resin cements after accelerated aging was evaluated and statistically significant color changes occurred within clinically acceptable range.

Reconstruction of anterior guidance using duplication technique of CAD/CAM: a case report / 대한치과보철학회지

Comprehensive prosthetic treatment requires considerations from various points of view. The anterior guidance is important factor in prosthodontic treatment of anterior teeth. Lingual surface contour of anterior restoration is so critical that a small mistake of laboratory or clinical process can cause discomfort of patient and disharmony of entire dentition. There are no guidelines for lingual surface contour that fit all patients. Therefore the lingual surface of provisional restoration is most accurately described as a customized one. The dentist transfers the exact information of anterior guidance that has made through long term provisional restoration to the technician. This case introduce that the duplication technique of CAD/CAM system to reproduce the anterior guidance of provisional restoration. This method can improve satisfaction of both patient and dentist.