The Effect of Instrument Design on Ultrasonic Cleaning Efficiency

C.H. Miller and C.J. Palenik, Indiana University School of Dentistry, Indianapolis, Indiana, USA

Instrument cleaning reduces bioburden that interferes with sterilization. Objectives: This study was designed to measure ultrasonic cleaning effectiveness on differently designed dental curettes. Methods: Four brands of dental curettes (13/14 Gracey) were contaminated with defibrinated sheep blood containing hydroxyapatite (50 mg/mL) by complete immersion for 10 seconds. After drying for an hour, curettes were added to an instrument basket, which was then placed into an ultrasonic cleaner. The unit was operated for 90, 120 or 300 seconds. One type of ultrasonic cleaner and cleaning solution was used. Each run contained 5 curettes from each of the 4 brands. Three runs were preformed for each cleaning time period. After cleaning, instruments were rinsed and analyzed for remaining contaminants by visual observation, a Hemastix assay for blood and quantitatively for protein. Uncleaned control instruments were analyzed for protein. Results: Visual absence of blood on all instruments occurred only after 300 seconds of cleaning. Blood was detected by the Hemastix assay on all instruments at all cleaning times except for one type of curette after 300 seconds of cleaning. In this case, five of the 15 instruments were free of detectable blood. These curettes also had the lowest average level of detectable blood, which was statistically (two-tail ANOVA, p <0.001) different at all cleaning periods. The same type of curettes had the fewest number of instruments with detectable protein at all cleaning periods and the lowest amounts after 90 and 300 seconds of cleaning. All curettes had protein removal levels above 99% when compared to uncleaned control instruments. Conclusions: Curette design may affect amounts of residual blood detectable after ultrasonic cleaning and rinsing.

Financial support was provided by LASCOD SpA, Florence, Italy.