Intraosseous heat generation during sonic, ultrasonic and conventional osteotomy.

Objectives: To assess heat generation in osteotomies during application of sonic and ultrasonic saws compared to conventional bur.

Methods: Two glass-fiber isolated nickel-chromium thermocouples, connected to a recording device, were inserted into fresh bovine rib bone blocks and kept in 20 ± 0.5 °C water at determined depths of 1.5 mm (cortical layer) and 7 mm (cancellous layer) and 1.0 mm away from the planned osteotomy site. Handpieces, angulated 24-32°, were mounted in a vertical drill stand, and standardized weights were attached to their tops to exert loads of 5, 8, 15 and 20 N. Irrigation volumes of 20, 50 and 80 ml/min were used for each load. Ten repetitions were conducted using new tips each time for each test condition. The Mann-Whitney-U test was used for statistical analysis (p < 0.05).

Results: Both ultrasonic and sonic osteotomies were associated with significantly lower heat generation than conventional osteotomy (p < 0.01). Sonic osteotomy showed non-significantly lower heat generation than ultrasonic osteotomy. Generated heat never exceeded the critical limit of 47 °C in any system. Variation of load had no effect on heat generation in both bone layers for all tested systems. An increased irrigation volume resulted in lower temperatures in both cortical and cancellous bone layers during all tested osteotomies.

Conclusion: Although none of the systems under the conditions of the present study resulted in critical heat generation, the application of ultrasonic and sonic osteotomy systems was associated with lower heat generation compared to the conventional saw osteotomy. Copious irrigation seems to play a critical role in preventing heat generation in the osteotomy site.