During a recent visit to the dentist involving multiple fillings and an obnoxiously loud drill, I was anxious to go home and research rates of hearing loss amongst dental professionals. During my externship, I had previously fit dentists with custom earplugs, but had never personally investigated the literature regarding their typical noise exposure. To my surprise, I found not only a tremendous amount of research, but also a tremendous array of outcomes. While several studies have shown that some common dental tools create noise in excess of safe exposure limits (Kadanakuppe, Bhat, Jyothi, & Ramegowda 2011; Qsaibati & Ibrahim 2014), the evidence suggesting dental professionals have higher rates of noise-induced hearing loss and tinnitus is mixed. A sample of some of these studies can be seen in Table 1.
Table 1. Incidence of NIHL in Dentists Study Outcomes
|Year||Researcher(s)||↑ Risk of NIHL||↑ Risk of Tinnitus|
|2016||Alabdulwahhab et al||Yes||NOT STUDIED|
|2016||Myers et al||No||YES|
|2014||Khaimook et al||No||NOT STUDIED|
|2014||Willershausen et al.||Yes||NOT STUDIED|
|2013||Theodoroff et al||Yes||NOT STUDIED|
|2012||Lopes et al.||Yes||NOT STUDIED|
Although not conclusive, existing evidence does suggest dental professionals are at increased risk of hearing problems from prolonged exposure to occupational noise. Fortunately, noise-induced hearing loss is entirely preventable, and as audiologists we have the tools and knowledge necessary to protect against NIHL. Below I define four steps we as audiologists can take to protect dentists from NIHL, and these same steps can be used for virtually any patient with concerns regarding workplace noise.
Step 1: Complete a comprehensive baseline diagnostic test battery, and think beyond the standard audiogram. Research suggests noise-induced hearing loss will often appear first as changes in high-frequency audiometric thresholds (Mehrparvar et al., 2014) and otoacoustic emissions (Baradarnfar 2012). While research is mixed in determining if transient-evoked or distortion product OAEs are best for detecting “sub-clinical” NIHL, DPOAEs are typically favored for their frequency specificity (Oeken & Müller 1995). When completing diagnostic DPOAEs to detect and monitor NIHL pay close attention to frequencies between 2kHz and 10kHz, and test at least five frequencies per octave to avoid missing a noise notch (Hall 2015).
Step 2: Measure workplace noise in real-time. Most smartphone sound level meter apps are of questionable accuracy, but the National Office for Occupational Safety (NIOSH) has recently released an easy-to-use, highly accurate sound level meter app for iOS devices. With this app, your patients can take measurements of their workplace in real-time and send you the results directly. When instructing your patients in how to take measurements, inform them they should place the microphone as close to the location of their ear as possible for the most accurate representation of the noise level reaching their ears. These measurements will be highly useful in determining their level of risk and necessary level of attenuation for hearing protection.
Step 3: Develop a plan for noise protection and noise mitigation. Work closely with your patient to determine what style of protection works best for the them. Using the noise measurements taken in the workplace, select a level of attenuation that reduces the harmful noise levels while keeping conversation with staff and patients audible. Finally, encourage your dentist patients to maintain and replace their dental equipment as recommended by the manufacturer. Multiple studies have shown up to a 10 dB reduction in noise output when the dental equipment is maintained properly.
Step 4: Establish an annual monitoring protocol. The American Dental Association recommends annual hearing tests for all dentists regularly exposed to occupational noise. These follow-ups should include an updated case history and medical intake information, updated conventional audiometric thresholds, high-frequency audiometry, and OAEs. Use previous testing to monitor for clinically-significant changes in thresholds and assess if any changes need to be made to the choice of noise protection.
Although the research regarding dental professionals and noise-induced hearing loss is inconclusive, audiologists have the knowledge and tools necessary to determine their patient’s noise-exposure risk and make appropriate recommendations for hearing protection. Now that’s something to smile about!
For Further Reading:
Clinician’s Guide to OAE Measurement: http://www.audiologyonline.com/articles/clinician-s-guide-to-oae-14981
NIOSH App: https://www.youtube.com/embed/ZUoeDlYOAIQ
Alabdulwahhab, B., Alduraiby, R., Ahmed, M., Albatli, L., Alhumain, M., Softah, N., & Saleh, S. (2016). Hearing loss and it’s association with occupational noise exposure among Saudi dentists: a cross-sectional study. BDJ Open, 2, 16006.
Baradarnfar, M.H., Karamifar, K., Mehrparvar, A.H., Mollasadeghi, A., Gharavi, M., Karimi, G., … Mostaghaci, M. (2012). Amplitude changes in otoacoustic emissions after exposure to industrial noise. Noise Health, 14(56), 28-31.
Kadanakuppe, S., Bhat, P., Jyothi, C., & Ramegowda, C. (2011). Assessment of noise levels of the equipments used in the dental teaching institution, Bangalore. Indian Journal of Dental Research, 22(3), 424-431.
Khaimook, W., Suksamae, P., Choosong, T., Chayarpham, S. & Tantisarasart, R. (2014). The prevalence of noise-induced occupational hearing loss in dentistry personnel. Workplace Health & Safety, 62(9), 357-360.
Lopes, A. C., de Melo, A. D. P., & Santos, C. C. (2012). A study of the high-frequency hearing thresholds of dentistry professionals. International Archives of Otorhinolaryngology, 16(2), 226–231.
Mehrparvar, A. H., Mirmohammadi, S. J., Davari, M. H., Mostaghaci, M., Mollasadeghi, A., Bahaloo, M., & Hashemi, S. H. (2014). Conventional Audiometry, Extended High-Frequency Audiometry, and DPOAE for Early Diagnosis of NIHL. Iranian Red Crescent Medical Journal, 16(1), e9628.
Messano, G. & Petti, S. (2012). General dental practitioners and hearing impairment. Journal of Dentistry, 40(10), 821-828.
Myers, J., John, A. B., Kimball, S., & Fruits, T. (2016). Prevalence of Tinnitus and Noise-induced Hearing Loss in Dentists. Noise & Health, 18(85), 347–354.
Oeken, I. & Müller, H. (1995). Distortion product otoacoustic emissions (DPOAE) in chronic noise-induced hearing loss- recommendations for expert assessment. Laryngorhinootologie, 74(8), 473-480.
Qsaibati, M. L., & Ibrahim, O. (2014). Noise levels of dental equipment used in dental college of Damascus University. Dental Research Journal, 11(6), 624–630.
Theodoroff, S. & Folmer, R. (2013). Hearing loss associated with long-term exposure to high-speed dental handpieces. General Dentistry, 63(3), 71-76.
Willershausen, B., Callaway, A., Wolf, T. G., Ehlers, V., Scholz, L., Wolf, D., & Letzel, S. (2014). Hearing assessment in dental practitioners and other academic professionals from an urban setting. Head & Face Medicine, 10, 1.