ORAL HEALTH EVIDENCE-BASED PRACTICE PROGRAM
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Title Dentists’ Are Not At Risk of Hearing Loss Due to High Speed Drill Noise
Clinical Question Are Dentists at risk of hearing loss due to high speed drill noise compared to the general population?
Clinical Bottom Line Dentists are not at risk of hearing loss due to high speed drill noise as compared to the general population.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 359623 Forman-Franco/197870 American Dentists from 8 specialties. RCT
Key resultsThis study compared the audio logical evaluations (consisting of hearing thresholds at eight frequencies – 500-800 Hz and impedance audiometry) of 70 randomly selected dentists from eight specialties to the normal age-adjusted population. When the mean hearing threshold levels (left and right) of general dentists were adjusted for age and compared with a similar normal population, no statistical differences (p>.5) were found. Most energy from the air-turbine high speed drill is concentrated in the higher frequencies (above 4,000Hz). When a ball bearing type drill was used, intensities slightly above 85dB were found. Air bearing drills were 10dB lower and both hand pieces showed an additional drop of 8-12dB when subjected to cutting torque. On the basis of length of exposure and noise intensity, air turbine drill in proper working order should be within tolerable limits regarding damage to hearing. Hearing at frequencies less than 3,000Hz (commonly referred to as the speech range) was not affected by drilling. Fifty percent of word intelligibility is found between 1,000 and 2,450 Hz, therefore few, if any discrimination difficulties would be expected in the dental population. When comparing the hearing levels as adjusted for age of the general population to hearing levels of the general practitioners, no statistical difference was found. A correlation appears to exist between years in dental practice and progressive loss of hearing. These findings mimic the relationship of advancing age and loss of hearing in the normal population. This suggests that when a loss of hearing occurs, it was primarily an effect of aging.
#2) 2758794 Lehto/198968 Dentists with at least 10 years of practice experience. Cohort Study
Key resultsThis was a comprehensive follow-up program to study the health status and behavior of dentists. Two studies (1973 and 1988) observed hearing threshold at 6kHz differed highly significantly from corresponding reference thresholds in both male and female dentists, P=<0.001. In 1973 male dentists differed highly significantly more from their reference thresholds than female dentists differed from theirs, P=<0.001. In the 1988 study this difference was of the same kind and statistically significant, P=0.04. The observed losses of hearing at the frequencies 4, 6 and 8 kHz were relatively evenly distributed among the examinees, so that hearing threshold levels exceeding 60 dB were rare even at the 6 kHz frequency. Thus, mild noise induced hearing loss (NIHL) were very common in dentists, with a tendency to appear earlier in males than in females. In the 1973 study the prevalence of NIHL (both ears) was significantly higher in males (70%) than in females (25%), P=0.002. In the 1988 study the difference between the prevalence of NIHL of both the ears in males (75%) and females (48%) was not statistically significant. The difference remained essentially similar over the follow-up period, indicating the dental drill noise was insufficient to cause continuous hearing loss. While mild NIHL was very common and tended to appear earlier in male than in female dentists, there was in the long run no continuous loss of hearing in either sex other than that attributable to the natural development of presbyacusis.
Evidence Search The following search strategy used in PubMed: Hearing Loss in Dentistry, High Speed Drill Noise
Comments on
The Evidence
These studies represented a good cross-section of the profession. The criteria for the testing were explicit and credible. The diagnostic work-up was comprehensive and consistently applied. There was no follow-up in the first study. The second study, as the title states, is a 15 year follow-up. There were no apparent competing interests of the authors in either study.
Applicability The participants in these studies were representative of the dental profession. Dentists avoidance of unnecessary noise of drills in their offices and other environments is feasible. Dentists need not be afraid of routine exposure to the noise of the drill. Dentists can expect to have some hearing loss from aging but not from the noise of the high speed drill.
Specialty/Discipline (Oral Medicine/Pathology/Radiology) (Endodontics) (General Dentistry) (Oral Surgery) (Orthodontics) (Pediatric Dentistry) (Periodontics) (Prosthodontics) (Restorative Dentistry)
Keywords Hearing Loss in Dentistry, High Speed Drill Noise
ID# 2471
Date of submission: 04/08/2013spacer
E-mail Ronald.brown@ucdenver.edu
Author Ronald N. Brown, DDS
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