Effect of surface conditioning on the shear bond strength of Compomers to human primary and permanent enamel

Purpose: To compare the bond strength of two polyacid-modified composite re sins (Compomer) to primary and permanent enamel with and without acid-etchi ng and to test for a possible relationship between the determined shear str ength values and area of cohesive failure within the materials on the bondi ng interface. Materials and Methods: Two compomer materials (Dyract and Com poglass) with their respective one-bottle primer/adhesive agents (Prime & B ond 2.0 and Syntac Single Component) were investigated. The parameters test ed were shear strength and area of cohesive type of failure after debonding of specimens with respect to the total area of the bonding interface. Resu lts: Mean bond strength to primary enamel ranged from 4.09 MPa (Compoglass) to 5.6 MPa (Dyract), while in permanent enamel the mean values were betwee n 12.3 MPa (Compoglass) and 14.3 MPa (Dyract), when pretreatment was made w ith bonding agents only. Generally, acid-etching prior to pretreatment impr oved adhesion significantly (6.0 MPa and 8.1 MPa in primary enamel and 16.0 MPa and 19.4 MPa in permanent enamel for Compoglass and Dyract, respective ly). Over one-half of the variation in the values for cohesive failure area was explained by its linear relationship with shear bond strength.