Comparison of two ultrasonic cleaning units for deterioration of cutting edges and debris removal on dental burs.

The effects of two ultrasonic cleaning units on surface deterioration and cleaning effectiveness of dental burs were compared in this study. The units tested were the Dextrex Model L 503B (Dextrex Chemical Industries, Inc., Bowling Green, KY) industrial ultrasonic unit and a conventional dental ultrasonic unit L & R T-21 B (L & R Manufacturing Co., Kearny, NJ). SEM photomicrographs of the burs were made before cleaning; and burs were processed for 10 min in each unit. Forty-eight new burs (24 #1/2A diamond and 24 #330 carbide) contaminated with human blood and 48 burs contaminated with tooth debris following cavity preparation were used to evaluate cleanliness. To assess deterioration, 48 new burs were evaluated for changes in the number of diamond chips or pits (carbide burs) and color changes following ultrasonic cleaning. Neither unit sufficiently cleaned the burs, as evidenced by remnants of remaining blood and debris on the burs. The loss of diamond chips was statistically significant for the burs processed in the Dextrex unit (P < 0.001) as well as for burs processed in the L & RT 21-B unit (P < 0.01). The mean number of pits was significant in carbide burs processed in both units as well (Dextrex unit: P < 0.01; L & RT-21 B unit: P < 0.001). No differences were noted in color changes for any of the burs in either unit. These data showed that the industrial-type unit was no more effective in cleaning dental burs than the conventional unit, though both units caused significant amounts of deterioration in the cutting surfaces.