Bonding to Composite Resin With Diverse Surface Finishes

Objective: This study investigated bonding of new composite to existing composite that had either been kept dry or aged in water. Specimens were cured after placement of a surface sealant or an oxygen barrier, or were cured then polished. Method: Cylindrical specimens of a hybrid composite (Renew, BISCO Dental) were prepared and finished, using polishing disks (Sof-lex, 3M ESPE), Mylar Strips, or surface sealant (Bis-cover, BISCO Dent.). Each group was divided into two sub-groups (I and II). Subgroup I was immersed in water for five weeks and subgroup II was kept dry. Each subgroup was further divided into four sub-subgroups and treated as follows before bonding new composite resin: a) no surface modification and DEresin (BISCO) applied; b) no surface modification, and a dentinal adhesive applied (One-Step, BISCO); c) roughened, then silane (Prolong, Chameleon Dent. Prod) and DEresin applied; d) roughened, then an application of silane and dentinal adhesive. All specimens were then bonded to 2 mm diameter, 2mm in height composite cylinders, stored in room temperature water for seven weeks, and subjected to shear bond strength testing in an Instron Testing Machine, cross-head speed 5 mm/min. Data were analyzed using ANOVA (P<0.05). Results: Polished wet and dry specimens that had had silane applied before bonding produced significantly higher bond strengths. Surface-sealed specimens recorded higher bond strengths with silane and One-Step as well as with silane and DEresin. The use of silane did not affect the bond strength of the Mylar group. The wet subgroups recorded higher bond strengths with the added composite as compared with the dry subgroups. Conclusion: Finished composite (polished, sealed, or barrier-protected), fresh or existing, may have new composite added, with certain modification. Roughening the existing composite may not lead to a stronger bond. This study supported by BISCO Dental Prod.