Effects of occupational ultrasonic noise exposure on hearing of dental hygienists: a pilot study.

PURPOSE The purpose of this case-control study was to determine whether long-term ultrasonic noise exposure via the dental office environment is related to dental hygienists' hearing status. METHODS Registered dental hygienists (N = 698) who live in the Hampton Roads areas of Virginia were mailed a Dental Hygiene Work History Questionnaire to determine who would meet the inclusion criteria and would be willing to participate in the study. Consenting subjects were categorized into one of two groups, according to ultrasonic scaler usage rate, and matched on age. Persons with known hearing loss due to infection, disease, or congenital defect were excluded from the study. The final sample consisted of 20 dental hygienists with a high ultrasonic usage rate and a matched group of 20 dental hygienists who had a low ultrasonic usage rate. Once the groups were formed, a certified audiologist tested subjects' hearing in each ear via the pure-tone audiometer. Audiometric data were analyzed using the analysis of variance for repeated measures procedure to determine if degree of ultrasonic scaler noise exposure in the dental office environment was significantly related to hearing status in these dental hygienists. RESULTS Results revealed that the right and left ears were not statistically different in the hearing threshold levels, regardless of group status. However, there was a significant difference in the high ultrasonic usage group and the low ultrasonic usage group at the 3000 Hz. No differences were found at the frequencies of 500, 1000, 2000, 4000, 6000, and 8000 Hz. CONCLUSIONS Based on these outcomes, the ultrasonic scaler is not considered to have a negative effect on the hearing of dental hygienists at 500, 1000, 2000, 4000, 6000, and 8000 Hz, but may be related to hearing loss at 3000 Hz. Ultrasonic noise may in fact be affecting dental hygienists' hearing at 3000 Hz, but loss of hearing observed at the higher frequencies may be attributed to other unidentified factors present in both groups.