Bonding to dental zirconia ceramic

Abstract

Introduction The first purpose of this study was to determine the bond strength of resin cement to zirconia ceramic after different surface treatments by means of three shear bond strength (SBS) test methods and to compare the sensitivity and the reliability of the SBS test methods. The second purpose was to evaluate the performance of the new universal adhesives (Single Bond Universal, 3M ESPE and All-Bond Universal, Bisco Inc.) as a surface treatment agent for zirconia with a test method established through the foregoing experiment.

Materials and methods In Experiment I, polished zirconia ceramic (Cercon® base, DeguDent) slabs were randomly divided into four surface treatment groups: no treatment (C), airborne-particle abrasion (A), treatment with a conventional phosphate monomer-containing primer (Alloy Primer, Kuraray Co.) (P), and treatment with Alloy Primer after airborne-particle abrasion (AP). Bond strengths of resin cement to the zirconia specimens of each surface treatment group were determined by three SBS test methods: Method 1, the conventional SBS test with direct filling of the mold (Ø 4 mm x 3 mm) with resin cement

Method 2, the conventional SBS test with cementation of prefabricated composite cylinders (Ø 4 mm x 3 mm) using resin cement

Method 3, the microshear bond strength (μSBS) test with cementation of prefabricated composite cylinders (Ø 0.8 mm x 1 mm) using resin cement. The bond strength data were statistically analyzed using two-way analysis of variance (ANOVA) with factors of SBS test method and surface treatment. One-way ANOVA followed by Dunnett T3 test was performed to compare bond strengths. The coefficient of variation (CV) and the Weibull parameters were used to compare the consistency and reliability of the three test methods. In Experiment II, the performance of universal adhesives containing phosphate monomer as a surface treatment agent for zirconia was evaluated with a test method established through Experiment I and compared to that of Alloy Primer. A conventional single-bottle adhesive (Single Bond 2, 3M ESPE) was used as a negative control. Bond strengths were obtained after 24 h of water storage and after 10,000 thermocycles between 5°C and 55°C with a 25 s dwell time. The bond strength data were statistically analyzed using one-way ANOVA followed by Tukeys HSD test.

Results Both SBS test method and surface treatment significantly influenced the SBS values (p < 0.05). The AP group showed the highest bond strength regardless of the test methods. Only Method 3 (μSBS test) revealed a significant difference between the P group and the A group, such that, as the SBS values increased, the CV decreased and the Weibull parameters increased. Method 3 was the most discriminative test method, producing consistent and reliable results. Method 3 was thus used to evaluate the effects of the universal adhesives on the bond strength of resin cement to zirconia. Single Bond Universal showed the highest initial bond strength (37.7 ± 5.1 MPa), followed by All-Bond Universal (31.3 ± 5.6 MPa), Alloy Primer (26.9 ± 5.1 MPa), and Single Bond 2 (8.5 ± 4.6 MPa). Artificial aging significantly reduced the bond strengths of all the test groups (p < 0.05). However, the bond strengths of Single Bond Universal (20.7 ± 6.4 MPa) and All-Bond Universal (26.9 ± 6.9 MPa) remained significantly higher than that of Alloy Primer (10.7 ± 4.2 MPa) after thermocycling (p < 0.05).

Conclusions The μSBS test was more discriminative in differentiating the effects of surface treatments than the conventional SBS tests. The combination of airborne-particle abrasion and a primer containing phosphate monomer was the most effective in improving the bond strength of resin cement to zirconia. The universal adhesives significantly improved the bond strength and its durability of resin cement to zirconia when compared to Alloy Primer.