Influence of different primers and adhesive system combinations on the durability of resin bonding to lithium disilicate

Statement of problem

The long-term performance of universal dental primers and adhesive systems where all the different components are mixed in a single composition has not yet been thoroughly investigated.

Purpose

The purpose of this in vitro study was to evaluate the bond strength and the durability of various luting composite resins to lithium disilicate ceramic after the application of the system’s specific primer or after the application of a pure silane primer (Hoffmann’s Silan).

Material and methods

A total of 128 lithium disilicate specimens were etched with hydrofluoric acid and randomly divided into 4 main groups according to the assigned adhesive system. Each group was further divided into 2 subgroups: the first was conditioned with the specified system’s primer, while the second was conditioned with a pure silane primer. Plexiglas tubes filled with composite resin (Clearfil FII New Bond) were adhesively bonded to the lithium disilicate specimens using the assigned luting composite resin. Half of the specimens in each subgroup were stored in distilled water at 37 °C for 3 days, while the other half were subjected to artificial aging over 150 days and 37 500 thermal cycles (5 °C to 55 °C). All surviving specimens underwent tensile bond strength (TBS) testing in a universal testing machine. Statistical evaluation was carried out using 3-way ANOVA, followed by separate 2-way and 1-way ANOVAs. The Tukey HSD test was applied as a post hoc test for pairwise comparisons (α=.05).

Results

All specimens survived storage and thermal cycling without failure of the adhesive bonds. After 150 days of artificial aging the mean TBS values ranged from 11.0 ±4.1 MPa to 50.7 ±7.4 MPa. The adhesive system had a significant effect on the resulting TBS, whereas the effect of the conditioning method and artificial aging was not statistically significant for all groups.

Conclusions

Artificial aging had a negative effect on the bond strength of all groups except 2. After 150 days, the adhesive system significantly influenced the resulting TBS. The use of freshly mixed silane resulted in higher bond strength for all systems after 150 days than the use of the system-specific primer or adhesive monomer, although the increase was not statistically significant for all systems.