Microshear Bond Strength and OCT Wear Resistance of CADCAM Composite

Objectives: This study evaluated the microshear bond strength (MSBS) of an adhesive resin cement with or without surface treatment to CADCAM composite and its wear resistance after different loading cycles using OCT.
Methods:
Lava Ultimate CADCAM blocks (3M) were sectioned by low-speed diamond saw in two groups (n=24). Specimens in the surface treatment group were sandblasted with 50µm alumina particles at 2.5 bar for 10 seconds at a 10-mm distance. Resin cylinders (0.7mm diameter, 1mm height) were bonded using Panavia SA Cement Universal and Clearfil Universal Bond Quick 2 (Kuraray Noritake Dental). In the non-treatment group, the resin cement was placed without sandblasting or bonding. MSBS was measured using the wire loop technique at 1.0 mm/min in a tester (Bisco). For the wear test, all specimens were embedded in PMMA and subjected to 200,000, 400,000, and 600,000 cycles under a 50N load using a spherical indenter following a circular movement pattern in a chewing simulator (SD Mechatronik). After each loading episode, OCT analysis (Yoshida Dental OCT) was performed. Volume loss (VL) and linear wear (LW) were calculated by analyzing the 3D OCT images using Amira software. MSBS was compared using a t-test while VL and LW were analyzed using Kruskall-Wallis followed by Mann-Whitney with Bonferroni correction (alpha=0.0125).
Results: MSBS (Table 1) was significantly higher in the surface treatment group (p<0.01). VL and LW increased with the number of cycles; there was a significant difference among all loading episodes (p<0.01) except for between 200,000 and 400,000 cycles (p>0.0125).
Conclusions:
The surface treatment (sandblasting followed by universal bond) significantly enhanced the bond strength of the adhesive resin cement to the CADCAM composite. The highest rate of composite wear occurred at the early stages of loading and continued to increase as the loading continued. OCT is applicable for non-destructive evaluation of the wear resistance of dental materials.