Marginal accuracy and microleakage of various semi-permanent crown materials

Abstract

Background/purpose: To investigate the marginal accuracy and microleakage of three semi-permanent crown materials under thermocycling. Materials and methods: Human lower premolar teeth were prepared for crown restoration (n=45), separated into 3 groups (n=15) by the material types as follow: Group U: self-cured PMMA (Unifast™ Trad, GC, Tokyo, Japan); Group P: bis-acryl (Protemp™ 4, 3M™ ESPE, Minnesota, USA); and Group L: novel bis-acryl resin (LuxaCrown, DMG, Hamburg, Germany). All specimens were fabricated and cemented with self-adhesive resin cement (RelyX™ U200, 3M™ ESPE, Minnesota, USA), then divided into 3 subgroups by thermocycling process (n=5): no treatment (TC0), 5,000 cycles (TC5000) and 10,000 cycles (TC10000). The specimens were immersed in 50% silver nitrate solution and kept in a developing solution (GBX, Carestream, New York, USA). Subsequently, they were buccolingually sectioned with a cutting machine (IsoMet™ Low Speed Saw, Buehler, Düsseldorf, Germany) in which buccal and lingual margins were obtained (n=10) before being observed under a stereomicroscope (SZX7, Olympus, Tokyo, Japan) with a 30x magnification. The marginal accuracy was then analyzed by two-way ANOVA and the microleakage score was described by a pivot chart. Results: The two-way ANOVA revealed that the types of material and the thermocycling process significantly affected the marginal accuracy (p-value < 0.01). However, the materials among Group U-TC5000, P-TC5000, P-TC10000, L-TC5000 and L-TC10000 were not significantly different (p-value > 0.1). Regarding the trend of the microleakage shown in the pivot chart, as the thermocycles increased, more leaked specimens were obtained. Conclusion: Marginal accuracy and microleakage of LuxaCrown are comparable to Protemp™ 4, and both of them are superior to Unifast™ Trad.