Practice Tips #117: Are You Hearing This?

Are you hearing this? As a dental professional, you may encounter occupational hazards every day. Hearing loss might be one of them. Your hearing might be at risk due to the noises encountered in your dental practice that may make you susceptible to the development of permanent hearing loss.

Hearing loss caused by noise is referred to as noise induced hearing loss (NIHL). According to the National Institute for Occupational Safety and Health (NIOSH), noise-induced hearing loss is the most common occupational injury.(1) So what makes noise hazardous? The level of risk and type of noise determine whether or not specific noise endangers your hearing.

Levels of Risk

There are three properties of noise that can be examined to determine the level of risk: intensity (i.e. volume), duration, and spectrum (frequency or frequencies) of the sound.(2) These three elements of sound, which include time characteristics and the physical make-up of the noise, interact to put an individual at risk for hearing loss.(3)

Intensity

Handpieces generate loud noises of a high frequency. The intensity of sound measures in decibels (dB). The greater the intensity of the sound (or the higher the dB level), the greater the risk of hearing damage.

Many studies have examined whether the noise found in a dental practice exceeds the Occupational Safety and Health Act (OSHA) standards. OSHA regulations for industry limit a worker’s exposure to steady noise levels of 90 dB in an eight-hour time period.(4) Dental professionals are exposed to equipment that emits differing levels of noise.

Garner et al. have reported that common types of exposure in a dental office can include: angled-design turbine handpieces, low-speed handpieces, lab electromotor handpieces, high-speed turbine handpieces, stone mixers, lab machines, ultrasonic scalers, and ultrasonic cleaners.

The ISO standard 14457:2017(en) for high-speed handpieces has established a noise limit of 65 dB, with a maximum output of 80 dB, well under the 90dB OSHA limit. With age, wear, and other variables, it is still possible for these dental instruments to exceed the 90db limit. Some researchers have reported that noise levels can reach 100 dB with the use of air turbines.(5) If the higher intensity is reached, allowable exposure time should be reduced to two hours per day.

This graph shows the differences of decibels heard at a music concert using different ear protection, including the EARasers. Image is courtesy of EARasers.

With handpieces functioning within ISO standards, a typical dental office should not exceed the limits set by OSHA and proposed by NIOSH. However, damage from noise may still occur. Garner et al. stated that “the authors have clinical experience suggesting there is sufficient anecdotal evidence to warrant a more active approach to hearing conservation by the dental team.”(6)

Duration

The duration of the sound is measured in time. The longer the period of time during which an individual is exposed to a sound, the greater the risk of developing this condition. Feuerstein has reported that “long-term exposure studies have shown a clear link between the number of years of daily exposure and hearing loss.”(7)

Spectrum

The final element of noise is the spectrum. Feuerstein has observed that “most noise exposures are due to complex, variable, broadband signals.”(8) Dental handpieces typically create sound with a frequency spectrum varying from 3,000 hz – 6,000 hz. In contrast, an average male human voice is centered with a frequency of 250hz. An average female human voice is centered at 300 hz.

Noise filtering ear plugs help to filter the loud high-frequency sounds of the handpiece, while still allowing the lower frequency of human voices to penetrate. You can still hear staff and patients.

The risk to hearing is real, what can you do to limit your personal risk?

Hearing Protection Check List:

• Maintain good posture
• Keep an appropriate distance between yourself and the patient
• Keep your equipment well-maintained and operating within original specifications (see Practice Tip #34 on what and when to maintain your dental equipment)
• Wear hearing protection

Hearing protection devices protect the dental professional from potential noise damage, but it must allow the dentist or dental assistant to hear sufficiently, in order to communicate with the patient. One option is to purchase custom earplugs, the same type of hearing protection device used by many musicians for protection from occupationally induced hearing loss. Garner et al. found that “the musician’s style earplug is perfectly suited to the dental environment and is an affordable and comfortable solution. Voices sound softer, but are still audible. A definite decrease in the noise from dental equipment will be observed.”(9) If custom products are not used, other hearing protection devices such as generic insert earplugs (foam plugs or flanged plastic plugs) and headsets are possible alternatives.

Taking the suggested precautions to limit sound exposure through posture, patient positioning, and equipment maintenance. To assure noise levels generated by your equipment are as low as possible, proper maintenance helps. Wearing hearing protection can be an effective additional step to assure you can keep your hearing intact and undamaged throughout your career.

Endnotes:

1. Garner, G.G., Federman, J., Johnson, A. Noise induced hearing loss in the dental environment: An audiologist’s perspective. J Georgia. Dent Assoc, 2002:17–19.
2. Feuerstein, J.F. Occupational Hearing Conservation. In J. Katz (Ed.), Handbook of Clinical Audiology, 5th ed., 2002, p. 569. Philadelphia: Lippincott Williams & Wilkins.
3. Melnick, W. (1985). Industrial Hearing Conservation. In J. Katz (Ed.), Handbook of Clinical Audiology, 3rd ed., 1985, p. 726. Baltimore: Williams & Wilkins.
4. Fabry, D.A. Hearing loss as occupational hazard. Northwest Dentistry, 1995;74:29–32.
5. Hyson, J.M. The air turbine and hearing loss. Are dentists at risk? J Am Dent Assoc, 2002;133:1639–1642.
6. Garner, G.G., Federman, J., Johnson, A. Noise induced hearing loss in the dental environment: An audiologist’s perspective. J Georgia. Dent Assoc, 2002:17–19.
7. Feuerstein, J.F. Occupational Hearing Conservation. In J. Katz (Ed.), Handbook of Clinical Audiology, 5th ed., 2002, pp. 567–583. Philadelphia: Lippincott Williams & Wilkins.
8. Feuerstein, J.F. Occupational Hearing Conservation. In J. Katz (Ed.), Handbook of Clinical Audiology, 5th ed., 2002, p. 569. Philadelphia: Lippincott Williams & Wilkins.
9. Garner, G.G., Federman, J., Johnson, A. Noise induced hearing loss in the dental environment: An audiologist’s perspective. J Georgia. Dent Assoc, 2002:17–19.