Date of Degree
MS (Master of Science)
Marcos A. Vargas
Resin-based composite for Class IV restoration is a conservative alternative for maxillary incisor fracture. Little is known about the effect of lingual margin configurations on the longevity of these restorations. This in vitro experiment compared the mean fracture strength among four lingual margin configurations (butt joint, 45° bevel, 60° bevel and chamfer) for Class IV resin-based composite restorations. A total sample size of n=100 human extracted lower incisors were selected, then the teeth were randomly assigned to one of the four lingual margin configuration groups (n=25) and restored with resin-based composite. After thermocycling (5000 cycles, 5°C-55°C with 30 seconds dwell time), they were subjected to inter-incisal static load (135° angulation) until failure (N). Failure mode was determined. In vitro fracture strength was compared among the four groups using one-way ANOVA at alpha=0.05. Mean standard deviation of fracture strength and frequency distribution of failure modes were reported.
Results revealed no significant effect on the fracture strength for the type of lingual margin configurations (F(3,96)=0.13; p=0.9435). The data showed that 71% of failure modes resulted in complete tooth fracture (intact restoration), 11% in total adhesive failure, 7% in adhesive only facial, 6% in total cohesive, 4% in cohesive only facial, 1% in avulsion. Fischer’s exact test revealed no statistically significant association (p>0.05) between the margin configurations and failure modes. Within the limitations of this study, it can be concluded that any of the four lingual margin configurations are acceptable in Class IV preparation in terms of fracture strength under static load.
Dentistry includes restoring teeth for both esthetics, and function. In cases of upper teeth chipping, the dentist offers different treatment options including the use of resin material that is bonded to the remaining tooth structure. In order to improve the retention of the material, a tooth preparation is required, including smoothing margins and beveling the edges. Little is known about the longevity of these restorations related to the different bevel preparations. This study compared the fracture strength among the four types of bevels that retained the resin composites on upper anterior teeth. One hundred teeth were selected and then divided into four experimental groups (twenty-five teeth per group). Teeth were subject to thermocycling and static forces until they broke. Fracture strength and failure mode were recorded and compared. There was no difference in fracture strength and failure mode among the four designs for bevels. This study concludes that the proposed margin configurations to restore upper human incisors with resin did not affect the fracture strength.
publicabstract, Bevels, Class IV preparations, Fracture Strength, Margin configuration, Resin-based composites
Copyright 2015 Nubia Carolina Garcia Martinez