To solve the problem of mechanical instrumentation, we developed a cone-shaped laser irradiation tip. This tip delivers 80% of the energy of the laser laterally and 20% of the energy forward. The tip was equipped with a water nozzle. The aim of this study was to examine the effect of Er:YAG laser irradiation using this tip on root canal enlargement and debridement. As a root canal model, a hole (0.5 × 5 mm) was drilled into a bovine dentin block. The tip was inserted into this hole and moved from the apex to the orifice (45 mm/min). The power of 10 mJ × 10 pps caused enlargement of the canal dimension by 106.5%. 20 and 40 mJ × 10 pps caused enlargements of 116.3 and 118.6%. 30 mJ × 10 pps caused the biggest change (129.8%). Scanning electron microscopic observations indicated that the dentin surface after laser preparation appeared cleaner than that obtained after preparation by drilling. This technique may have the advantage of decreasing the preparation time.
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