Evaluation of Microshear Bond Strength of Orthodontic Resin Cement to Monolithic Zirconium Oxide as a Function of Surface Conditioning Method

Purpose: To evaluate the microshear bond strength (μSBS) of orthodontic resin cement to monolithic zirconium oxide ceramic (MZ) after different surface conditioning methods. Materials and Methods: Two types of MZ (BruxZir Solid Zirconia, n = 60; Prettau-Zirkon, n = 60) with two types of surface finish (glazed, n = 30 per group; polished, n = 30 per group) were tested after two surface conditioning methods: 1. air abrasion with 30-μm silica coated aluminum oxide (Al2O3) particles (CoJet), or 2. air abrasion with 50-μm Al2O3 particles. The non-conditioned group acted as the control. A universal primer (Monobond-Plus) and an orthodontic primer (Transbond-XT Primer) were applied to all specimen surfaces. Orthodontic resin composite (Transbond-XT) was bonded using a mold and photopolymerized. The bonded specimens were subjected to μSBS testing (0.5 mm/min). Data were analyzed statistically using three-way ANOVA and the Sidac adjustment post-hoc test (α = 0.05). Failure modes were analyzed using a stereomicroscope (30X). Results: Mean μSBS values (MPa) did not show a significant difference between the two brands of MZ (p > 0.05). In both glazed (44 ± 6.4) and polished (45.9 ± 4.8) groups, CoJet application showed the highest μSBS values (p < 0.001). The control group (34.4 ± 6) presented significantly better results compared to that of Al2O3 (30 ± 3.8) (p < 0.05) on glazed surfaces, but it was the opposite in the polished groups (control: 20.3 ± 4.7; Al2O3: 33.8 ± 4.7; p < 0.001). Adhesive failure was the dominant type in all groups. Conditioning MZs with Al2O3 and CoJet increased the percentage of mixed failure type. Conclusion: Air abrasion with CoJet followed by the application of universal primer improved the μSBS of orthodontic resin to both the polished and glazed monolithic zirconium oxide materials tested

Relation between handling characteristics and application time of four photo-polymerized resin composites

OBJECTIVE: To investigate the relation between handling characteristics and application time of four composite materials with subjectively different viscosities. METHODS: Eight experienced faculty members placed one Class II and one Class IV restoration in a random sequence into pre-prepared plastic teeth mounted on a typodont model, each using 4 types of composites (Herculite Précis (M1), Kerr; Tertic N-Ceram (M2), Ivoclar Vivadent; Filtek Z350 (M3), 3M-ESPE; Charisma Opal (M4), HareausKulzer), resulting in a total of 64 restorations. The application process was filmed with a high definition video camera. Two evaluators watched the recordings in a random sequence as well, timed the composite application and wrote down their observations, which were dichotimised into positive and negative ones. Application times were analysed with a two-way Kruskal Wallis test (time x dentist) and the observation data were analysed with a chi-square test (P < 0.05). RESULTS: Materials did not differ in their application time (P > 0.05). The mean application time was 12 ¼ minutes for the Class II and 9 ¾ minutes for Class IV restorations. However, there were statistically significant differences between the dentists in terms of application time. The observation data showed no significant difference between Class II and Class IV restorations but there were significant material differences (P < 0.05). M2 yielded 6% negative observations, while the other materials were between 35% and 38%. CONCLUSION: There was no association between the handling characteristics of the tested composite resins and the speed of application. However, one of the tested materials (M2) showed significantly less problems in the application process