Influence of cutting of enamel surface with Er: YAG laser on bond strength

Masashi Miyazaki, DDS, PhD,(a),(b) Hideo Onose, DDS, PhD,(a),(b) Naoshi Hirohata, DDS PhD,(a) Osamu Nishizawa DDS,(a) and B. Keith Moore, PhD(c)

(a)Department of Operative Dentistry, (b)Division of Biomaterials Science, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan, and (c)Department of Restorative Dentistry, Dental Materials Division, Indiana University School of Dentistry, Indianapolis, IN, USA

Purpose: The purpose of this study was to examine the influence of cutting the enamel surface with an Er: YAG laser on bond strengths of two-step adhesive systems and compare them with a surface prepared with high-speed rotary cutting instrument.
Materials and Methods: Adhesive systems employed in this study were Imperva Fluoro Bond/Lite-Fil II A (Shofu Inc.) and Single Bond/Filtek Z250 (3M/ESPE). Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were ground wet on #600-grit SiC paper followed by cutting with a diamond bur (ISO #022,FG-Regular 103,Shofu Inc.) or an Er: YAG laser (Erwin, Morita Mfg. Corp.). After treating the tooth surface according to manufacturers’ instructions, resin composites were bonded to enamel. Fifteen samples per test group were stored in 37°C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute. One-way analysis of variances (ANOVAs) followed by the Duncan test (p<0.05) were done.
Results: For the adhesive systems used, the highest bond strength was obtained with #600 SiC abrasive followed by the diamond bur and Er: YAG laser ablation. Only the enamel bond strengths obtained with Imperva Fluoro Bond were significantly influenced by the means of cutting the enamel surface, lower for Er: YAG laser ablation.
Conclusion: The bond strengths of the self-etching primer system were significantly affected by the methods of enamel cutting, the highest bond strength was obtained with #600 SiC abrasive (17.8 MPa) followed by the diamond bur cutting (16.8 MPa), and the lowest bond strength was obtained with Er: YAG laser ablation (11.2 MPa).
(Int Chin J Dent 2002; 2: 75-85.)

Clinical Significance
: The laser treated enamel surface conditioned with the self-etching primer may not create a suitable adherend surface for bonding as compared to the one-bottle adhesive system that employ phosphoric acid as a conditioner. Care should be taken with the combination of the cutting methods and the adhesive systems used.
Key Words: bond strength, enamel, Er: YAG laser, resin composite.