Hearing loss and its silent role in affecting our careers and systemic health
Hearing loss is the most significant unaddressed threat to our careers as dental professionals.1 Today, we have more personal protective equipment (PPE) and regulations than ever before. We are required by Occupational Safety and Health Administration (OSHA) and other standards to protect ourselves from exposure to blood, chemicals, solvents, and other biohazards. We can make the argument that our PPE serves to preserve one of our five senses: gloves protect our hands and thus help preserve our sense of touch, masks cover our mouths and noses and protect our senses of smell and taste, and eye protection preserves our sight. We have now incorporated N95 masks as additional barriers against inhalation of COVID-related viruses. Yet, despite decades of evolution in PPE, regulatory mandates, and countless sources of literature warning us of the perils of our noisy working environment, our sense of hearing has been completely ignored, to our great detriment.
Prevalence of hearing loss
If hearing loss were officially considered a disability, it would rank as the highest in the world,2 affecting over 25% of the population.3 Over 48 million Americans suffer from advanced hearing loss, while an additional 30 million workers are exposed to hazardous noise on the job daily according to the Centers for Disease Control and Prevention (CDC).4 Noise-induced hearing loss (NIHL), which specifically targets dental professionals, is defined as a permanent hearing impairment resulting from prolonged exposure to high levels of noise.5
It is the most self-reported occupational illness/injury in the workforce and is an invisible problem that shows no signs of its presence until it has reached irreversible levels.6 It ranks as the third most common chronic health problem in the country after hypertension and arthritis, and its prevalence is more common than highly funded and publicized diseases such as cancer, diabetes, mental health, and asthma.7 Further, despite its prevalence, NIHL and hearing loss in general are widely uninsured issues, minimizing its publicity and adding to the financial burden it causes once identified.
Hearing loss issues are now starting at earlier ages than ever before thanks to advancements in technology. Past generations considered televisions and radios as luxuries, but today’s children have more options than ever before, and the use of devices such as iPods have created a new wave of hearing issues from a younger age. As early as 2001, it was estimated that over 12% of children ages 6-19 had hearing impairment in one or both ears.8 Today, over 80% of elementary school children use personal music players9 for extended periods of time, meaning their exposure starts at younger and younger ages, leading to hearing issues far sooner than prior generations and driving up the longterm ramifications. Thus, it begs the question: How can something so serious and so prevalent throughout our population receive so little attention?
Why hearing loss is not being addressed
A lack of screening is a major contributing factor; over one fifth of those above the age of 65 say they have never had a hearing test before, and only around 20% of adults have had their hearing checked in the last three years versus 60% having vision checks.10 Compare that with yearly medical visits, bloodwork, and wellness checkups, and it paints an unfortunate picture in which proper diagnosis cannot be achieved. Another important reason that hearing loss receives so little attention is that many careers have reduced exposure to dangerous levels of noise and are less at risk. Dentistry is not one of them.
According to the American Dental Association (ADA), dentists continue to work longer careers and retire at a later age.11 The average dental career is now 35 years and rising, and including dental school and a possible residency program, the actual dental career is closer to 40 years in duration. If we know that NIHL specifically results from prolonged exposure to high levels of noise, the picture begins to be seen more clearly. A simple mathematical calculation shows a scary reality: a traditional five-days-a-week, eight-hour workday in the dental environment over the course of a typical career adds up to over 70,000 hours of exposure for the average dental professional. It’s therefore no coincidence that our profession suffers badly from this issue, and we need to better educate ourselves on the process of hearing loss itself and how we may protect ourselves.
Anatomy of the ear
To better understand NIHL and how it is established, one must first look to the anatomy of the ear. Our ears are anatomically divided into three sections: the external, middle, and inner ear. The external ear serves to collect and amplify incoming sounds and help determine which direction the sound is coming from.5 The middle ear contains the three tiny bones (incus, malleus, stapes) linking the eardrum to the inner ear. The vibrations from the eardrum cause the tympanic membrane to vibrate, and those vibrations then move into the inner ear.
The inner ear has two parts: the vestibular, which deals with balance, and the cochlea, which handles hearing. The cochlea has a snail shell appearance, and within this shell are hair cells and fluid. As the fluid moves due to the incoming vibrations from the eardrum, the hair cells move; this movement creates signals that translate to the auditory complex of the brain via the auditory nerve to the central nervous system, where the final processing of the sound is completed. With continuous levels of damaging sound from NIHL, the hair cells begin to vasoconstrict and become damaged, and once damaged, they cannot regenerate. It then requires a greater intensity of sound to reach hair cells deeper within the cochlea to translate noise, giving us the perception of hearing loss.
How NIHL occurs
The initial signs of hearing loss begin at the 4 kHz frequency, also known as the “4k notch,” an identification indicator analogous to a 5 mm probing depth and periodontal disease. The hair cells that are damaged first are present in the area of the cochlea responsible for high-frequency sounds; that’s why we lose this range of hearing first.5 Upon initial exhaustion of the hair cells from a loud exposure, a muffling or ringing sensation will result. Picture a night out at a concert, and waking up to a muffled buzzing of your ears. This is known as the temporary threshold shift.12 What we typically notice with this shift is that after a day or two in a quieter environment, the muffling disappears. Problem solved, right?
For decades within the audiology community, this was the narrative. But a groundbreaking study showed a totally different reality; it turns out that even a single incident of a temporary threshold shift can result in acute loss of cochlear nerve terminals and longterm delayed degeneration of the cochlear nerve.13 Not only can this damage not be measured via any hearing test, but the results may not be fully realized for years.
Stages of hearing loss
Hearing loss occurs in three stages. In stage one, we have temporary threshold shift incidents and hair cell permanent damage.12 The individual cannot detect any changes with their hearing, nor can it be detected on a screening test. In stage two, high-frequency hearing is permanently lost, but typical speech and lower frequency hearing still appear normal. This change can be detected via a hearing test, but as established earlier, few people get checked regularly. By the time stage three is reached, both high- and lowfrequency hearing are affected, and regular speech becomes difficult to discern.12 The individual now realizes something is wrong, but by this point, damage is permanent and irreversible; hearing aids are the only solution.
Ironically, a similar tale occurs with our patients and dental care. We warn them about signs of infection and/or decay, and stress the need to act before it progresses, but a lack of pain makes patients hesitant, so they choose to monitor the area until things progress to the point of acute pain and an emergency visit becomes necessary. Our frustration stems from a dedication to prevention, which, ironically, we do not apply to our own wellness and hearing loss.
Dentistry is a risk factor for hearing loss
NIHL is preventable, yet our regulatory bodies have not pushed hearing protection as the standard of care. Noise is considered to be dangerous at levels of 85 dB and higher.5 In context, 85 dB is relatively the environment where someone standing three feet away will not be able to hear you unless you raise your voice. While normal speech is in the 60-65 dB range, the bulk of dental equipment used daily easily exceeds the 85 dB range.14,15 The question is: How long can we be exposed to these sounds before they damage our ears?
OSHA, which carries the force of law, states that in a 90 dB environment, you can be exposed for a total of eight hours before causing damage. Conversely, the National Institute for Occupational Safety and Health (NIOSH), which uses scientific studies and data to determine values and is the only standard used by audiologists, states that for the same decibel level, we can only be exposed for two hours before causing damage.5 The difference in hearing standards is massive! We all are aware of OSHA but haven’t known about NIOSH simply because they don’t carry any legal enforcement. But it gets worse; both standards are based on a standard eight-hour day, five-day workweek and therefore assume our remaining 16 hours of the day and entire weekend are spent in a noise-free environment! The reality is that even the NIOSH standards are not strict enough, and the true amount of exposure time without harm is far less than the standards suggest. This combined with our daily exposure to noise in the dental environment shows we are at significant risk.
The reason dental professionals are at such risk is that hearing loss is a cumulative issue over time5; while we may spend only 25 minutes per patient using the high-speed handpiece, suction, or ultrasonics, we do this multiple times daily, for an average career of 35 years. The literature has demonstrated endless studies clearly showing that our daily armamentarium far exceeds the permissible levels of decibel exposure.
In one study done by an audiologist at a dental school, the data showed high-speed handpiece and ultrasonic instrument levels ranging from 95-102 dB or, according to NIOSH, an average total exposure limit of only 30 minutes per day.14 Another meta-analysis done in Europe also showed an average decibel exposure in dental clinics of 91 dB, with a total cumulative daily drilling time of approximately two hours, exactly matching the permissible NIOSH standards.16
Studies on hygienists have shown those practicing for over 20 years with ultrasonics have hearing levels equivalent to an average citizen three decades older,17 and compared to other health professionals, dentists have significantly worse hearing.9,25 This holds true for all ages and genders compared to the general population.18 Our hearing capacity as a whole is equivalent to people decades older than we are,5 and each member of the dental team from specialist to lab tech to assistant is similarly affected.19
Systemic results of hearing loss
While the relationship of the risk of NIHL and our professional career is more obvious, the significant systemic health effects that NIHL causes are completely overlooked. Exposure to chronic noise can lead to significant systemic health issues such as cardiovascular disease and depression.20 It reduces productivity, increases stress, and interferes with concentration. 21 This insult results in both sympathetic and endocrine responses deteriorating our overall health in the long term.21
Consider some daily scenarios we are all familiar with: At a stoplight, the car behind you aggressively honks their horn and yells at you when the light turns green. In response, you get angry and honk back. This response initiates an increase in blood pressure and anger in the acute phase, activating your endocrine system via adrenaline. As an isolated episode, the risks are minimal, but done on a more chronic basis, this constant endocrine activation can lead to long-term heart disease.
Another example is noise exposure occurs when we’re trying to sleep. Oftentimes, we like to say that we are capable of “sleeping through anything,” but the reality is more complicated. High noise disturbances, from a passing ambulance, loud group of people, or an unruly neighbor, will create microdisturbances that may wake us for a brief moment and disturb our deep sleep, again activating the endocrine system. With time, we notice that our sleep quality and quantity are reduced, which in the acute phase affect our productivity at work and also can cause hypertension.21 Chronic episodes to these noise disturbances can result in long-term cardiac issues.21
One study highlights how workers with average career spans of 35 years (matching the average dental career) and prolonged moderate or severe noise exposure had an increased incidence of cardiovascular death.22 Even pregnant women exposed to chronic noise are found to have significantly higher incidence of premature births and low-birth-weight babies23; thus the systemic health risks NIHL carry cannot be overlooked.
Preventing hearing loss
Our best counter to this risk is prevention via hearing protection. The ADA and endless publications have recommended hearing protection since 1974; why have we ignored the warnings?15 Our options in the past were very limited.
Traditional foam plugs result in significant muffling of sounds and the inability to communicate; studies show this as the primary reason protection has been avoided.17 They are very useful when it comes to increased attenuation (lowering of decibels), but the amount of reduction is too extreme. Solutions like noise-canceling headphones are not practical for our environment, and again eliminate communication. Thus, it is evident that we not only require something that provides us protection, but also something that doesn’t cut us off from our environment and affect our ability to communicate with patients and staff.
The first positive step in that direction came with the introduction of passive ear technology. By incorporating a filter within the plug that can utilize different levels of attenuation, the amount of muffling compared to traditional foam is improved while still providing protection. These plugs also can be made to custom fit an individual’s ear via a mold, further improving fit and function. While passive plugs with filters are a definite improvement, they still filter all sounds that pass through the ear, whether or not they cause damage. 1,24 This means that normal conversation, which falls well below the danger level, will be equally attenuated as any sound within the danger zone, resulting in increased difficulty communicating.
As dental professionals, what we require is something that protects us from hearing damage while simultaneously preserving our ability to hear and communicate with patients and staff. This technology is known as active hearing protection.24,25 Using a tiny electronic microchip located within the plug itself, the damaging sounds from the environment are instantly isolated and compressed to lower levels while still maintaining an “open ear” response, resulting in 100% HD hearing (figure 1).1,25 Hearing damage is prevented, and communication remains unaffected. This technology gives us a solution to solve noise exposure issues.
The first active hearing protection product for the dental professional, known as DI-15 (currently EarAid), was first introduced at the Greater New York Dental Conference in 2014 (figure 2). It provided 15 dB of attenuation; thus working in an environment of 100 dB would be lowered down to 85 dB, increasing permissible exposure time significantly without affecting normal sounds. The 15 dB attenuation was chosen based on the literature and audiology recommendations. 14 The product successfully underwent an intensive two-year ADA Professional Product Review where it earned top marks; yet despite the scientific and clinical affirmation from the ADA and multiple publications, 25 our profession underutilizes the product.
Products such as the EarAid and other comparable products are powerful preventive tools for the dental profession. Other supplementary methods of prevention include regular hearing tests, utilizing electric versus air-driven handpieces, minimizing exposure outside of the workplace, and trying traditional foam or passive plugs. Stock plugs and other OTC devices are not nearly as effective as electronic protection, but some level of protection is better than none at all.
It’s time we take a stand and begin seriously addressing dentistry’s true pandemic. While we continue to fret over the newest bonding agents and software platforms, we continue losing our hearing daily. The responsibility to take action is ours. Twenty years ago the idea of dental loupes was considered radical and the clinical adjustments and applications unrealistic; today it’s considered the standard of care in all teaching institutions and globally accepted for clinical use. The premise of requiring N95 masks as an additional layer of protection would have been laughed off in 2019; today it has become a standard form of PPE and something we all have adjusted to using despite the added difficulties in breathing and discomfort.
So why is the idea of incorporating hearing protection still so taboo? Decades of literature, tens and thousands of our peers affected, and serious systemic health risks have not changed our approach to the biggest silent killer in all of dentistry. Certainly, the introduction of an added form of PPE will meet initial hesitation, but nothing has the significant all-around impact of NIHL on our professional career and overall health. Ultimately, it’s not a question of if, but rather when and how much our hearing and quality of life will be affected by dentistry. Ask yourself a simple question: How much do you value your hearing?
References
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September 18, 2019. https://www.aaosh.org/connect/dentistrys-deafening-silence
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11. The dentist workforce. American Dental Association Health Policy Institute Statistics. 2015 https://www. ada.org/resources/research/health-policy-institute/ dentist-workforce
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This article was originally published on RDHmag.com