Bond strength and micro morphology of a self-etching primer versus a standard adhesive system with varying etching times in primary teeth.

Aims: These were to firstly evaluate the shear bond strength of a composite resin to primary dental enamel treated with a standard adhesive system but with varying phosphoric acid etching times along with a self-etching prime, secondly to analyse the etching patterns using SEM.

Methods: Forty primary molars were used. In the first three groups, following acid etching, a layer of Prime & Bond NT adhesive was employed, and in group 4 the self-etching adhesive system (Prompt-L-Pop) was used. A composite cylinder (Spectrum, Denstply, Germany) was then applied. After processing of the samples, the teeth were subjected to shear stress using an Instrom universal machine. The study of primary enamel morphology after etching for different time periods and using different etching systems was carried out with a scanning electron microscope.

Statistics: Data were analysed using one way ANOVA, followed by Scheffé, test to determine differences between groups.

Results: In the groups subjected to acid etching for 5 and 15 seconds significant differences were recorded versus the self-etching group (p<0.0001). Regarding the SEM study of primary enamel morphology, there was predominately a clear and marked type 2 etching pattern.

Conclusions: Longer acid etching times for primary enamel do not appear necessary, as 15 seconds suffice to obtain retentive etching patterns, and the bonding strengths obtained with the traditional etching technique followed by two-step adhesive application are sufficient to ensure good composite resin bonding to the enamel surface. However, the self-etching adhesive system employed yields less than optimum bonding strength to primary enamel surfaces.