Effect of Er: YAG laser on repair bond strength of a nano-hybrid composite

Introduction
Due to the advancements in adhesion technology, minimally invasive approaches have gained popularity in today’s dentistry. With their improved aesthetic and mechanical properties, composite materials are widely used in clinical practice.

Objectives
This study aimed to evaluate whether surface pre-treatment with Er: YAG laser and bur, and application of various universal adhesives is effective on the repair bond strength of thermally aged nano-hybrid composite restorations.

Material and methods
A total of 96 disc-shaped specimens were made from a nano-hybrid resin composite material (Clearfil Majesty Esthetic, Kuraray), using standard size (14 mm diameter × 2 mm thickness) silicon molds. Thermally aged composite disc specimens were assigned randomly into 2 equal groups according to pre-treatment methods (bur or Er: YAG laser). Then, specimens were divided into 3 sub-groups according to used universal adhesive: GPB (G-Premio BOND, GC), CUB (CLEARFIL™ Universal Bond, Kuraray), and ABU (All-Bond Universal, Bisco, Inc.). They were aged 5,000 thermocycles and subjected to a shear bond strength test. Data were analyzed statistically, with p = 0.05.

Results
The groups that received pre-treated with Er: YAG laser showed statistically higher values of bond strength than the groups pre-treated with burs (p < 0.05). There was no statistically significant difference between the groups pre-treated with Er: YAG laser. For the groups pre-treated with bur, there were no statistically significant differences between B-CUB (Bur/Clearfil Universal Bond) and B-ABU (Bur/All-Bond Universal) groups (p > 0.05). B-GPB (Bur/G-Premio Bond) group exhibited the lowest bond strength (p < 0.05).

Conclusions
Er: YAG lasers may be used as alternative method used for pre-treatment for repairing nano- hybrid composite restorations. Silane-containing universal adhesives do not have better repair bond strength than other universal adhesives.