Spot-etch technique and other adhesive strategies for provisional veneers

Aim: The objective of the present study was to evaluate the influence of different adhesive strategies regarding shear bond strength (SBS) of provisional resin--based materials bonded to the enamel surface as well as on the enamel surface roughness.

Materials and methods: Bovine incisors were randomly divided into six groups (n = 10) according to the adhesive strategy used: BRControl (bis-acrylic resin); Spot-etch+BR (spot-etch + bis-acrylic resin); Spot--etchSB2+BR (spot-etch + adhesive + bis-acrylic resin); Spot-etchZ350Flow+BR (spot-etch + flowable composite resin + bis-acrylic resin); SBU+BR (universal adhesive + bis-acrylic resin); Spot-etchSBMP+Z350 (spot-etch + adhesive + composite resin). The enamel surface roughness was determined by a surface profil-ometer. An SBS test was performed in a universal testing machine, and failure modes were classified under magnification. The SBS data were analyzed by one-way analysis of variance (ANOVA). A paired t test was used for enamel surface roughness intragroup comparisons, and the Friedman one-way repeated meas-ures analysis of variance by ranks was used for differences in enamel surface roughness between groups, with the Tukey post hoc test (a = 0.05).

Results: BRControl had the lowest SBS values (MPa), with a significant difference (P ≤ 0.001) from the other groups. Spot-etch+BR had the highest SBS values but with no significant differences from the other groups in which the spot-etch technique was also used. Adhesive failure mode was predominant for all groups. BRControl had the lowest surface roughness difference, significantly different (P = 0.001) from all the other groups.

Conclusions: Spot-etch and other adhesive strategies could be applied to increase the SBS values of provisional restorations to enamel compared with no surface pretreatment. However, the adhesive strategy may change the enamel surface roughness, revealing the importance of cleaning the tooth surface.