Pii: S0109-5641(00)00092-0

Objectives: The purpose of this study was to compare microleakage of Class V restorations following acid, laser or laser and acid treatment of cavity walls. Methods: Standardized lingual and buccal Class V preparations were made in 18 human extracted third molars. The preparations were randomly assigned to three equal groups (nˆ 12). Group 1: cavities were treated with 35% phosphoric acid. Group 2: cavities were irradiated with an Er-YAG laser at 2 Hz and 250 mJ on dentin and 300 mJ on enamel, with water cooling. Group 3: cavities were irradiated with the laser before acid etching. Scotchbond 1 Adhesive System and Z100 resin composite were used for restorations. The specimens were stored in water for 24 h at 378C and thermally cycled (500 £ ) between 6±608C. After 24 h immersion in 0.5% basic fuchsin, dye penetration was recorded according to an ordinal scale. Data were analysed using non-parametric statistical tests (Kruskal±Wallis and Mann±Whitney). Results: On the occlusal walls, microleakage in acid etched cavities was signi®cantly lower than that achieved after laser treatment (P , 0.001) or after both treatments (P , 0.05). On the gingival walls, no statistical differences were found. Signi®cance: Laser irradiation of enamel is not a valid alternative to acid-etching pretreatment for resin composite materials adhesion. Acid etching alone gave the lowest microleakage at the occlusal margin. No differences were found for microleakage on gingival wall, although lased dentin surfaces presented several characteristics that appear to be advantageous for bonding. q 2001 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.