Effect of Application Mode and Aging on Microtensile Bond Strength of Universal Adhesives to Enamel of Primary Teeth

Background: Limited reports are available regarding bonding of universal adhesives to primary teeth' enamel.

Aim: To evaluate the effect of application mode and aging on microtensile bond strength (μTBS) of universal adhesives to primary enamel.

Design: Ninety-six human primary molars were randomly assigned to three groups: SU: Scotchbond Universal (3M); CU: Clearfil Universal Bond Quick (Kuraray Noritake); iBU: iBond Universal (Heraeus Kulzer), then subdivided according to phosphoric acid etching time into three subgroups (SG): SG1: 0s; SG2: 15s; SG3: 30s. Samples were incubated for 24 h, while separate samples for SG1 & SG2 were aged for 6 months. After μTBS testing, light microscope was used for evaluating failure patterns and SEM for the adhesive interface. Data were analyzed using linear mixed model and post hoc tests (p < 0.05).

Results: Selective etching increased μTBS of universal adhesives to enamel (p < 0.001) without significance between 15 and 30 s etching (p > 0.05). Six-month aging significantly reduced the μTBS of SU in SG2 (p < 0.014) when compared to 24 h aging.

Conclusions: Selective etching with phosphoric acid remains the gold standard for bonding universal adhesives to primary teeth enamel. While etching time showed no significant effect on immediate μTBS, aging may affect the μTBS of SU applied on 15 s etched enamel.