Parameter-dependence of marginal microleakage in Er,YAG laser ablated and modified dental preparations

Previous studies have shown that the status of the residual tooth surface after hard dental tissue ablation using laser irradiation may vary depending on the parameter combinations and cooling mechanisms used. The purpose of this investigation was to assess the effects of Er:YAG laser cavity preparation at different fluences on microleakage of glass ionomer and composite resin restorations. In freshly extracted clinically and radiographically healthy human anterior teeth, standardized Class V cavities were prepared using the dental drill or the Er:YAG laser (Quantronix 294). Fluences of 10 - 40J/cm 2 were used at a p.r.r. of 1 Hz and pulse durations of 250 microseconds under an air/water coolant spray. Thirty three teeth were included in each subgroup; 3 teeth were used for light microscopy and SEM; 15 underwent conventional restoration with glass ionomer and 15 with composite resin. After immersion in 5% methylene blue, dye penetration was measured linearly in 5 standardized locations on each of the bisected samples. Using the Pearson correlation coefficients, microleakage correlated strongly with laser fluence for glass ionomer (p equals 0.0238) and for composite resin (p equals 0.0099) restorations. Results differed significantly between the 2 restoration types (p less than 0.05). In conclusion, the parameters used during laser ablation of dental tissues must be carefully controlled to optimize clinical outcome.