Is someone listening to the din of occupational noise exposure in dentistry?
Mary Martha Stevens, RDH, PhD
The hazards of noise in the dental office are difficult to measure, according to research on the subject. But the effects noise has on each individual in the office should be evaluated on an annual basis. Dental professionals need to be aware of the dangers of occupational noise exposure, which is the leading cause of noise-induced hearing loss (NIHL) in the country.
After working as an assistant and hygienist in orthodontics for approximately 37 years, Bev Cook, RDH, recently found herself in distress when she began using a high-speed handpiece to remove bonding adhesives after orthodontic appliance removal. "I`ve noticed a gradual hearing loss over the years because I have been exposed to such intense sounds for so long. But the sound from the high-speed handpiece has been so irritating to my ears that it has put me on edge," Cook said. "Even slow-speed handpieces and suction noises can be an overload when working in large clinics where as many as six to 10 chairs are in use." Cook, who resides in Wichita, Kan., explained that, throughout her career, she also contended with disturbing sounds from the dental laboratory, which were clearly within hearing range.
Cook`s plight conjured up images of my work at Children`s Mercy Hospital many years ago. I could remember one UMKC pediatric dentistry resident, Dr. Richard Ackerman, being teased incessantly by classmates for wearing earplugs whenever he used the high-speed handpiece. Dr. Ackerman, who went on to receive a second specialist`s degree in orthodontics at Harvard University, retired recently after 19 years of teaching and chairing the orthodontic department at UMKC.
When questioned about why he chose to wear earplugs and endure the ridicule of classmates, Ackerman said, "My mother was almost totally deaf. So I was very much aware of the social effect deafness has on a person, and I certainly didn`t want to go down that route if I could avoid it. Beyond that, I always thought the sound of the high-speed handpiece was really shrill; it just hurt my ears."
Today, Ackerman feels that two of the biggest hazards to hearing in the dental office are the ultrasonic cleaner and scaler. "I think they present major problems; they`re probably much more intense than people realize."
Do we need to be concerned?
More than 20 million Americans are exposed, on a regular basis, to hazardous noise levels. Occupational noise exposure, as well as noise from sources outside our work setting, can contribute to a lifetime of overstimulation, culminating in permanent hearing loss. Unfortunately, once the damage is done, the problems are irreversible.
NIHL`s profound influence extends to all areas of one`s life, especially social activities. The stress associated with trying to understand what others are saying leads to fatigue, anxiety, and decreased participation in activities at work (as well as those that include family and friends). Hearing loss has even been associated with depression in the elderly.
Hal B. Merrell, PhD, professor and chair of the department of communicative disorders at the University of Tulsa, and Kay Claggett, CDA, wrote in the Dental Assistant, "Ears differ in their susceptibility to damage through exposure to noise, thus, exposure in a common work environment may cause hearing loss in one person and not in another. Exposure time and the intensity of damaging noise are inversely related. To prevent damage to a given ear, exposure time must be sharply reduced as the sound pressure level (SPL) of noise increases."
Hearing impairment can occur at any age. It is often characterized by difficulty in understanding speech and other symptoms such as tinnitus (ringing in the ears). Cook confirmed that her distress began with several uncomfortable symptoms. "I began feeling a ringing in my ears while I was using the high-speed handpiece. It was painful. Then afterwards, there is a roaring sound in my ears for a while."
What sounds are damaging?
Most sounds in our environment can produce hearing loss if they are experienced at a certain strength or amplitude (sound level recorded in decibels [dB]) on a daily basis for a period of time. On the other hand, explosive sounds can cause immediate permanent damage to hearing with just a single exposure. Additionally, sounds are measured in frequency or bandwidth (such as the span of the keys on a piano). The lowest audible frequency is about 20 Hz, and the highest audible range goes to at least 16,000 or 20,000 Hz. According to the 1990 National Institutes of Health Consensus Development Conference Statement, "Sound levels of less than 75 dB are unlikely to cause permanent hearing loss, while sound levels above 85 dB with exposures of eight hours per day will produce permanent hearing loss after many years." See the related chart for examples of sound measurements.
Although sound exposures that are potentially hazardous to hearing are usually defined in terms of sound level, frequency bandwidths, and duration, hearing experts agree that other exposures may be hazardous, including:
* If the sound is appreciably louder than conversational levels for a sufficient period of time, it is potentially harmful
* Noise may be hazardous if the listener experiences:
__ difficulty communicating while "in" the sound
__ ringing in the ear (tinnitus) after exposure to the sound
__ sounds seem muffled after leaving the exposure area
Tinnitus is nature`s warning that the noise levels are dangerously high.
Unfortunately for dental professionals, it is not known at this time whether ultrasonic vibration (sound outside the decibel frequency range) will damage hearing.
Protection and conservation strategies
In January 1990, the National Institutes of Health Consensus Development Conference on Noise and Hearing Loss brought together biomedical and behavioral scientists, health care providers, and the public to address the characteristics of noise-induced hearing loss, acoustic parameters of hazardous noise exposure, individual and age-specific susceptibility, and prevention strategies. Some comments and protection strategies emerging from the conference are:
- Dangerous sound exposure can cause significant damage without pain.
- Hearing aids do not restore normal hearing.
- Individuals should become aware of loud noise situations and avoid them, if possible. Otherwise, use hearing protection properly.
- Many sources, such as guns, power tools, chain saws, small airplanes, farm vehicles, firecrackers, some types of toys, and some medical and dental instruments may produce dangerous exposures.
- Music concerts, car and motorcycle races, and other spectator events often produce sound levels that warrant hearing protection.
- Some stereo headphones and loudspeakers are capable of producing hazardous exposures.
Hearing conservation programs for occupational settings must include the following components:
* sound surveys to assess the degree of hazardous noise exposure
* engineering and administrative noise controls to reduce exposures
* education to inform at-risk individuals why and how to prevent hearing loss
* hearing protection devices (earplugs, earmuffs, and canal caps) to reduce the sound reaching the ear
* audiometric evaluations detect hearing changes
Merrell and Claggett recommend that dental professionals incorporate a personal hearing conservation program (PHCP) into their practice to avoid the negative effects of noise exposure. First, have an audiologist perform a hearing evaluation to see if a hearing loss has taken place. Second, identify sounds in your 24-hour environment and limit your exposure to those that are annoying. This can be done by turning down the volume control on tape decks, radios, and TVs. Then, wear ear protectors when necessary to reduce exposure at work. Merrill found that earmuffs worn over the ears decreased sound levels 39 dB, whereas earplugs showed a 33 dB reduction in sound.
Quintessence International published an interesting article on common occupational hazards in the dental office titled, OMinimizing health hazards in the dental workplace: A critical review.O Dr. Robert Baratz, an assistant professor of oral pathology at Tufts University School of Dental Medicine, wrote, ONoise, especially repetitive noise at the same pitch and with the same decibel range from high-speed air turbine handpieces, can be minimized by proper adjustment of air pressure, regular lubrication, and ear protectors. Several types of ear protectors are on the market, which can be worn within the ear and are not unsightly. Repetitive handpiece noise produces permanent high-end hearing loss. (Volume 18, Number 11/1987).O
For the past three months, Cook has been wearing a hearing reduction headband device with rubber earplugs. It has reduced the sound level of the high-speed handpiece from 90 to 70 dB. OA friend of mine who is an audiologist measured this for me and said it is at a safe level now. The ear protector allows me to hear my patient while blocking out the sound,O said Cook. OIt?s been great while I?m working and has made a tremendous difference in my comfort level. I can still hear the noise of the handpiece, but it is not uncomfortable at all.O
Both Cook?s and Ackerman?s hearing protectors had been used by military crew members to block airplane sounds. Today, audiologists can fit dental professionals with custom earmolds. The protective devices can be comfortable and effective. For example, Westone Laboratories, Inc., the world?s largest manufacturer of custom ear molds, designed the ER-15 originally for musicians. The unique ER-15 filter protects against damaging noise levels, yet still allows the wearer to hear normal conversation and avoid the Oplugged upO feeling that generic over-the-counter earplugs can cause. The ER-15 attenuates the potentially damaging 80 to 90 dB noise levels that can be generated by dental equipment to a more comfortable 65 to 75 dB.
Mary Martha Stevens, RDH, PhD, is an RDH consulting editor. She acknowledges the assistance of Ann Marie Corry, librarian at the University of Missouri-Kansas City, School of Dentistry during the research of this article. She can be contacted by e-mail at [email protected].
Is the noise intense?
Sound measurements can vary, depending on the measuring device`s placement in relation to the sound. A noise and hearing loss referral Web site, earhelp.com, has listed the following common sound levels (these may differ depending on the product or condition):
Level (decibels) dB / Common Sounds
30 dB / whisper
50 dB / rainfall, quiet office, refrigerator
60 dB / dishwasher, conversation
70 dB / hair dryer, heavy traffic
80 dB / alarm clock, subway
90 dB / electric razor, lawnmower, shop tools
100 dB / chain saw, stereo system set above the halfway mark
110 dB / rock concert, power saw
120 dB / jet takeoff, night club, thunder
130 dB / jackhammer
140 dB / shotgun, air raid system
180 dB / rocket launching pad
Or is it pleasant?
Why are some sounds better than others? Besides the potentially damaging effects of sound, frequency, and duration levels, sounds in our environment can have a profound, positive impact on our lives, according to Janalea Hoffman, a music therapist and president of Rhythmic Medicine (www.ishopper.com/rhythmicmedicine). The Kansas City-based therapist specializes in relaxation and imagery work. Besides her private practice, she provides workshops and seminars to health professionals on how to use music therapeutically. "For example, I teach people how to lower their heart rate and blood pressure quickly. Your body constantly tries to synchronize to an external rhythm. This is called entrainment."
Hoffman explained that entrainment is happening all the time whether we are aware of it or not, because the body wants to be in harmony with the rhythms around it. If it`s a very fast rhythm, the body will speed up. If it`s a slow rhythm, the body will slow down. She has created therapeutic music that is played in a variety of health care settings, including dental offices.
"Most music or radio stations that are played in the work environment have an erratic rhythm which is stressful to the body," she said. "What I have done with entrainment is create musical compositions that have a steady rhythm (50-60 beats per minute), which allows the body`s immune system to function at its best. This creates a restful, peaceful rhythm for the body to synchronize with. It can help the fearful dental patient as well as dental personnel," said Hoffman.
Sounds have been shown to have healing qualities as well as damaging effects.
What OSHA wants to hear
The Occupational Safety and Health Administration (OSHA) regulates workers` exposure to noise. The federal agency revised its suggested hearing conservation program for employers in 1995.
Key points of the program are:
- Employers are required to monitor noise levels in order to identify employees who are exposed to noise at, or above, 85 decibels over an eight-hour period. OSHA clarified this by writing in its guidelines, "That is, employers must monitor all employees whose noise exposure is equivalent to or greater than a noise exposure received in eight hours where the noise level is constantly 85 dB."
This may imply situations where the noise is constant. But the guidelines state that the measurement of the noise include "all continuous, intermittent, and impulsive noise within an 80 dB to 130 dB range and must be taken during a typical work situation." The employer gets to choose the method for monitoring. However, employees have the right to be informed about the monitoring procedures. Any new purchases of noisy dental equipment, for example, should prompt a new evaluation of noise exposure.
- OSHA suggests that employers pursue two goals with audiometric testing. Obviously, testing "monitors the sharpness and acuity of an employee`s hearing over time." The agency also believes that the program should educate employees "about their hearing and the need to protect it."
Audiometric testing is a required component of a hearing conservation program. The agency has specific guidelines for a baseline exam and then following up with annual audiograms. Employers are supposed to provide the testing at no cost to employees "who are exposed to an action level of 85 dB or above."
The annual audiograms are routinely compared to the baseline to evaulate whether employees experience a lost ability to hear. The original baseline audiogram is supposed to be retained throughout a worker`s employment.
- According to the OSHA program, hearing protectors should be "available to all workers" who are exposed to eight-hour noise levels of 85 dB or above. As the agency asserts, "This requirement will ensure that employees have access to protectors before they experience a loss in hearing."
The decision about which size and type of hearing protector is used in the workplace belongs to employees, and they can enlist the help of a trained professional in choosing a protective device. The employer has to evaluate the effectiveness of a hearing protector "whenever there is a change in working conditions that may cause the hearing protector being used to be inadequate."
Additional information about requirements for a hearing conservation program can be obtained by calling the regional OSHA office or state workplace safety agency.