Effect of Dynamic Load on Adhesion of Hybrid Ceramic Onlay Restoration

Abstract

The purpose of this study was to examine the effect of dynamic load on adhesion of hybrid ceramic onlay restoration. Standardized MODB cavities were prepared for 32 extracted human lower molars. The cavities were coated with dentin using an all-in-one adhesive system, and impressions of cavities were taken with a silicon rubber impression material. A die stone was poured and hybrid ceramics onlays were made on the working stone model. The cavities were restored by onlays using adhesive luting cement. Specimens were divided into two groups and following tests (n=16) were performed, dynamic load stress condition (+; 300,000 repeated load stress of 16.0 kgf), control condition (-; non stress). The micro-tensile bond strength (μ-TBS) to the pulpal wall (P) and axial wall (A) was measured. The data were examined using two-way ANOVA. Student's t-test and Weibull analysis. The μ-TBS of P(+)/P(-)/A(+)/A(-) conditions was 7.94 (2.20)/10.53 (1.60)/9.56 (2.16)/10.12 (2.44) MPa. The μ-TBS of P(+) was significantly smaller than P(-) (p<0.01), and the μ-TBS of A(+) was similar to those of A(-). The μ-TBS of P(-) was similar to those of A(-), but the μ-TBS of P(+) was significantly lower than that of A (+) (p<0.05). The Weibull modulus of P(+)/P(-)/A(+) /A(-) conditions was 4.03/7.39/4.73/4.37, and the modulus decreased in response to a dynamic load stress at P (p<0.01). The Weibull modulus of P(-) was significantly smaller than A(-) (p<0.01), and the Weibull modulus of P(+) was similar to those of A(+). The effect of dynamic load varied in response to the cavity wall. Both the μ-TBS and adhesive reliability had decreased statistically at P, but not recognized at A. Under the (-) condition, the μ-TBS of P was similar to those of A, and the reliability of P was superior to those of A, but dynamic load stress reversed the inclination.