Micro Tensile Bonding Strength to Milled and Printed Permanent CAD/CAM Materials

Abstract

Purpose: To evaluate influence of different surface treatments and artificial aging on the micro tensile bond strength (μTBS) of three milled and printed permanent CAD/CAM materials (Lava Ultimate [LU], VarseoSmile Crown Plus [VS], and Ceramic Crown [CC]). Material and methods: Blocks of CAD/CAM materials (n=8/material; 14x14x6 mm; n=8/material; 14x14x5 mm) were fabricated by cutting from CAD/CAM blocks or by printing. After polishing of the bonding surface, specimens were divided into eight groups according to the surface treatment: control (C), Airborne Particle Abrasion (P), Silane (S), Adhesive (A), Airborne Particle Abrasion+ Silane (PS), Silane + Adhesive (SA), Airborne Particle Abrasion+ Adhesive (PA), and Airborne Particle Abrasion+ Silane +Adhesive (PSA). Blocks of 5- and 6- mm thickness with the same surface treatment were bonded together using a dual-cure resin cement (RelyX Ultimate). Every block was cut into 50 sticks with a dimension of 1.00 mm2 (±0.02). The sticks were subdivided into two subgroups: Non-Aged (.NA), and Aged (.A). μTBS test was performed using a universal testing machine. Data were analyzed using 3-way and 2- way ANOVA with Bonferroni post-hoc test (α=0.05). Weibull analysis was used to calculate the Weibull Modulus and Characteristic Strength to create Weibull plots and likelihood contour plots. Results: The micro tensile bond strength of the materials differed significantly from each other (CC>LU>VS). A significant difference was found between the different surface treatments, regardless of the Artificial Aging (PA>PS>PSA>P>S>SA>A>C). Aging significantly reduces the μTBS of LU and CC but does not significantly affect the VS. The most frequent failure mode was cohesive in resin, while for the milled material it was predominantly adhesive. Higher Weibull modulus and characteristic strength values were observed with the milled material compared to the printed materials. Conclusions: Surface treatment significantly affects μTBS to milled and printed direct CAD/CAM resin materials with increase of bond strength upon application of airborne particle. The adhesive interface of the milled material (LU) has a lower probability of failure than the interface of the printed materials (VS and CC).