In vitro analysis of the effects of acid or laser etching on microleakage around composite resin restorations

The aim of the present study was to determine the effect of two conditioning methods, phosphoric acid and XeCl laser application on microleakage at composite resin restorations.

Class II MOD (mesio-occluso-distal) cavities were prepared on 90 extracted human wisdom teeth with one proximogingival margin on enamel and the other on dentin. Phosphoric acid (37%) and a XeCl excimer laser system were used for the etching procedure. The prepared teeth were randomly assigned to six groups: In group 1, acid-etching of the enamel margins was followed by application of enamel bonding, in group 2 additionally a dentin bonding system was used. In group 3, acid-etching of the enamel and dentin (total etch) was followed by the application of dentin bonding. In group 4, laser-etching of enamel margins was followed by the application of enamel bonding, in group 5 dentin bonding was used additionally. In group 6, laser-etching of enamel and dentin margins was followed by the application of dentin bonding. All restorations were placed incrementally and polymerized with a halogen light source. After restoration, all samples were thermocycled and stained in 0.5% basic fuchsin and sectioned longitudinally in a mesio-distal plane. Microleakage was scored by means of a stereomicroscope. The margins of the restorations at tooth-resin interface were examined with a scanning electron microscope.

In all groups, marginal leakage was more extensive at the gingival margin that was in dentin than at the gingival margin in enamel. Microleakage scores and the gap at the tooth-resin interface were significantly lower in all acid-etched groups than in laser-etched groups.

Acid-etch technique is more effective than the investigated laser-etch technique at 308nm concerning the reduction of marginal leakage in composite restorations.