Abstract:
Common equipment in the dental operatory generate cumulative noise at sufficient decibel levels that can damage hearing. Although noise exposure in the dental office is typically intermittent, dentists and other dental care providers have been shown to be at risk of hearing loss. This article provides dentist-generated insight to use when incorporating hearing protection devices during dental practice. Four hearing protection devices (HPDs) were provided to 15 dentists in randomized sequence for evaluation. Perceptions were gathered via questionnaires and analyzed to determine mean ratings and product preferences. Battery requirements of electronic HPDs were also examined. Qualitative assessments of the HPDs evaluated are presented, including dentist preferences and recommendations.
There were statistically significant differences (P ≤ 0.0031) among the HPDs in terms of ease of insertion, aesthetics, ability to hear while using a hand piece, and the openness of the ear. Battery life was not found to differ between the 2 electronic HPDs evaluated. Dentists most highly valued ease of hearing, ability to communicate, and comfort while wearing HPDs. The DI-15 High-Fidelity Electronic Earplugs HPD was ranked the highest, followed by Music PRO Electronic Earplugs. Battery longevity for these electronic HPDs was similar under all tested conditions studied.
Knowledge Transfer Statement:
Dentists should understand the potential ramifications of hearing loss and be aware that there are commercially available hearing protection products that preserve the ability to communicate with patients and coworkers.
Keywords: hearing loss, hearing protection products, dentists, battery life, earplugs, product evaluation
Introduction
Within the United States, 15.2% of adults have some hearing trouble (Blackwell et al. 2014). Factors contributing to auditory dysfunction include age, genetics, disease, and loud noise exposure; an estimated 16% to 24% of hearing loss has been attributed to occupational noise exposures (Stockmen and Hong 2014). The Occupational Safety and Health Administration set the permissible exposure limit for noise to 90 dB for an 8-h workday (U.S. Department of Labor 2013), and the National Institute for Occupational Safety and Health provides a recommended exposure limit of 85 dBA for the same 8-h exposure period.
Because exposure to loud noise in the workplace is predictable, it is considered to be preventable. Nonetheless, occupational noise-induced hearing loss is estimated to be the most common occupational disability in the United States (Stucken and Hong 2014). Although noise is recognized as problematic in manufacturing and construction (Tak et al. 2009), there is less appreciation that common equipment in the dental operatory—such as hand pieces (70 to 92 dBA), ultrasonic scalers (86 dBA), and saliva suction tubes (75 dBA)—generate cumulative noise at sufficient decibel levels to damage hearing (Sorainen and Rytkonen 2002; Theodoroff and Folmer 2015).
Factors such as hand piece design, wear, bur concentricity, misuse, poor maintenance, and the design of the dental operatory can influence the level of noise generated by such equipment (Council on Dental Materials and Devices 1974; Bahannan et al. 1993). While noise exposure in the dental office is typically intermittent, dentists and other dental care providers have been shown to be at increased risk of hearing loss (Lopes et al. 2012; Willershausen et al. 2014; Goncalves et al. 2015).
Exposure to high levels of noise can also create stress, reduce productivity, and interfere with communication and concentration (U.S. Department of Labor 2013). Longer term hearing loss has been found to be a risk factor for memory, cognitive, and executive function impairment, as well as diminished ability to perform daily activities of living and those skills required for independent living (Dalton et al. 2003; Lin 2011; Lin et al. 2011; Lin et al. 2013).
Hearing loss has been associated with self-reported hearing handicap and communication difficulties; older adults with moderate to severe hearing loss have been found to have greater impairment in activities of daily living and instrumental activities of daily living, which are predictors of ability to live independently (Dalton et al. 2003). Based on the National Health and Nutrition Examination Survey data set, hearing loss was found to have an independent negative impact on cognitive test results (Lin 2011). Insight from the Baltimore Longitudinal Study of Aging found hearing loss to have an independent negative impact on test results evaluating memory and executive function (Lin et al. 2011).
In the Health ABC Study, a prospective observational study, individuals with hearing loss were found to have increased risk of cognitive impairment (Lin et al. 2013).
Avoiding noise exposure is the best preventative option for dentists concerned about hearing loss (Council on Dental Materials and Devices 1974), but this is often not possible in practice. Dental workers with unavoidable exposure to noise may conserve hearing through proper use of hearing protection devices (HPDs; Centers for Disease Control and Prevention 2013). However, studies have found that use of HPDs is not common among dentists (Serafini et al. 2003; Theodoroff and Folmer 2015). A qualitative study to explore factors influencing their use of HPDs found that the following influenced workers’ willingness to use HPDs: perceiving high noise levels as normal or unavoidable, HPD comfort, HPD ease of use, and communication problems while using HPDs (Reddy et al. 2012). An important consideration regarding use of hearing protection in dental practice is its impact on the ability to hear and converse with the patient. In dentistry, the ability to carry on 2-way communication with patients and coworkers is critical for the success of the treatment and for patient safety.
This evaluation was designed to capture insight from dentists who were provided with a range of hearing protectors to use in the clinic, to better understand possible barriers and facilitators of their use. Evaluated products ranged from disposable to high end HPDs (e.g., expandable foam plugs, nonelectronic plugs, and electronic plugs). Simulated-use battery life tests were used to characterize the battery demands of electronic level–dependent HPDs (DI-15 and Music PRO). The current evaluation focused on product features aiming to determine which characteristics were most important to dentists and how they may influence use of HPDs in the dental practice setting.
Materials and Methods
Participants and Protocol
The participants of this evaluation were the licensed and practicing full-time dentists who regularly used handheld powered dental instruments at U.S. Department of Veterans Affairs (VA) Medical Centers located in Togus, Maine; Portland, Oregon; and Houston, Texas. The protocol for this evaluation was developed in an agreement between the American Dental Association (ADA) and the VA; it was reviewed and determined to be exempt by the ADA Institutional Review Board. Participants provided written informed consent. For each participant, all 4 HPDs were assigned random numbers generated by a computerized random number generator and then distributed to the participants in that order.
The clinicians used each product either for 1 wk or approximately 20 h of wear during patient treatment. Throughout each week, the clinician made notes regarding the types of procedures performed while wearing the HPD. After each period of use, clinicians returned the product along with their completed product review questionnaire. They then received another HPD for evaluation. After using all 4 products and completing the individual product questionnaires, clinicians received a final questionnaire, in which they rated all the HPDs tested.
Questionnaire
The questionnaires (Appendix) were developed by the ADA and VA staff and were all self-administered on paper. The product review questionnaire had 4 sections.
The first section collected information characterizing the dentists who participated in this evaluation (Table 1). The second section collected the dentists’ ratings of HPD attributes; with a 5-point Likert-type scale where 1 was most positive and 5 most negative (Table 2). The third section used 4 yes/ no questions to gather dentist insight about the overall utility of the HPD (Table 3). The last section had open ended questions to explore advantages and disadvantages and collect other comments about the HPD that dentists wanted to share. The final questionnaire was given to the dentists at the end of the study after they had used each HPD for a comparative product rating in which they ranked all devices in order of preference and indicated the HPD feature that most influenced their determinations.
Hearing Protection Devices
Of the HPDs commercially available at the time of the study, 4 were chosen by a VA audiologist as representing a variety of styles and electronic and non-electronic types. All HPDs were purchased by the ADA from product manufacturers or distributors, for $0.15 (disposable Laser-Lite earplugs) to $350 (reusable DI-15 earplugs) per pair. The HPDs evaluated were as follows:
- MP 9-15 Music PRO Electronic Earplugs (Etymotic Research, Inc.)
- ETY Plugs High Fidelity Non Electronic Earplugs (Etymotic Research, Inc.)
- Laser-Lite Earplugs (The Safety Zone, LLC distributed by Henry Schein)
- DI-15 High-Fidelity Electronic Earplugs (Dental Innovations, LLC)
All HPDs were reusable, with the exception of the foam Laser-Lite Earplugs, which were disposable. The dentists participating in this study were provided with 1 pair of Laser-Lite Earplugs for each day of the evaluation.
Battery Life Evaluation
As the 2 electronic HPDs (DI-15 and Music PRO) both recommend use of Rayovac No. 10 hearing aid batteries, with a nominal voltage of 1.45 V, these were purchased by the ADA for evaluation.
Battery life in the electronic HPDs (DI-15 and Music PRO) was evaluated in the ADA Laboratories. Battery life was defined as the time from when the battery was first opened until it failed to produce feedback or until an audible warning sound was detected. It was divided into usage time, the period when the batteries were actively powering an HPD, and storage time, the period when the batteries were in storage (i.e., not powering an HPD). Because pattern of usage can affect zinc-air battery life, 5 batteries were evaluated for each electronic HPD brand in 3 usage conditions (continuous usage, unsealed storage, and resealed storage).
The continuous usage batteries powered the HPDs until they no longer functioned, with any time in storage. Unsealed and resealed storage conditions emulated clinical use in a typical workweek. These batteries were used to power the HPDs for 8 h/d for 5 d/wk and, when not in use, were removed and stored in an open nonconductive foam container. Unsealed storage batteries were stored without modification, while resealed storage batteries had the original plastic tab replaced to seal off the air intake prior to storage.
Results
The majority of participants were general dentists (73%); the remainders were prosthodontists (20%) or endodontists (6.7%; Table 1). Sixty six percent of the participants were men. Participants had between 0.5 to 35 y of experience in practice (average: 12.6) and graduated between 1 to 36 years previously.
Each HPD evaluated is shown in Figure 1. Mean ratings for HPD attributes are shown in Table 2. Table 3 presents clinicians’ perceptions of their ability to communicate while wearing each HPD with patients and colleagues, whether clinicians would use the HPD while working, and last, whether they would recommend its use to others.
DI-15 High-Fidelity Electronic Earplugs
DI-15 was ranked easiest to hear while using a high-speed handpiece and 87% of dentists indicated that they could hear patients or colleagues while wearing it. Of all the HPDs, dentists were most likely to use the DI-15 earplugs while working (73%) and would recommend them to other clinicians (73%).
DI-15 was rated the most attractive and the most likely to stay in place; it left the ear feeling most open; and it was best to hear other sounds while using a handpiece. Several dentists mentioned that the device’s connecting cord got tangled or interfered with equipment, such as face masks or loupes. The DI-15 has a power switch, which 2 of the 15 dentists found difficult to remember to use. When the battery was used for 8 h/d for 5 d/wk. and removed and resealed when not in use, the battery life was 254.5 h (SD = 11.5; Fig. 2).
Music PRO Electronic Earplugs
Music PRO was rated the most painless and most comfortable, which multiple dentists cited as its most desirable quality. It was rated second highest on ease of insertion, ability to hear while using a handpiece, and attractiveness. Dentists ranked it as their second most likely to use while working and the second most likely to recommend to other clinicians (64.3%). Music PRO turns on and off by opening and closing the battery door, which several dentists cited as a disadvantage. When the battery was used for 8 h/d for 5 d/wk and removed and resealed when not in use, the battery life was 256.0 h (SD = 10.8; Fig. 2).
ETY Plugs High Fidelity – Non-Electronic Earplugs
ETY was 1 of 2 products reported as having the easiest manufacturer directions and was considered the easiest product to insert. However, it received poor ratings on attractiveness, ear openness, and ability to hear patients and colleagues. A recurrent theme in the comments about this product was that it made it difficult to hear and communicate with patients and staff members.
Laser-Lite Earplugs
Laser-Lite was the other HPD reported as having the easiest manufacturer directions. It was, however, found to be the most difficult to insert, the least attractive, the most painful to wear, the least comfortable, the least likely to stay in place, the most likely to impart a feeling of a blocked or full ear, and the worst for hearing patients or colleagues, and it caused the most difficulty of hearing when using a high speed handpiece. Of all the HPDs tested, the lowest number of dentists (2 of 15, 13.3%) reported they would use or recommend it to other clinicians.
Product Comparisons
After evaluating all 4 products, participants were asked to rank the HPDs that they were most and least likely to use in the clinic. The DI-15 High Fidelity Electronic Earplugs HPD was ranked as the one that they were most likely to use, followed by the Music PRO Electronic Earplugs HPD. The ETY Plugs High Fidelity Non-Electronic Earplugs HPD and the Laser-Lite Earplugs HPD were ranked as the least preferred. Dentists ranked the HPDs in this same order regardless of years of experience or average hours per week exposed to sounds of high-speed handpieces or scalers. Ease of communication while wearing HPDs and the comfort of the HPD were frequent themes in individual product questionnaires and were the 2 features considered most influential in choosing a preferred HPD. Other considerations mentioned in open-ended survey questions were the visibility or appearance of HPDs and concern about the device’s adaptability to accommodate various ear shapes. Dentists reported a unique set of concerns associated with electronic HPDs, which included whether it interfered with existing equipment (e.g., whether the device’s connecting cord tangled with loupes), how easy the device was to turn on or off, and battery life.
Battery life did not differ significantly between the 2 electronic HPDs (i.e., DI-15 and Music PRO earplugs) for the 3 evaluated conditions (i.e., continuous usage, unsealed storage, resealed storage; ANOVA F test, P value = 0.617). Compared with batteries that were unsealed, batteries that were resealed or in continuous usage group had significantly longer usage times (ANOVA F test, P < 0.001; Fig. 2).
Conclusions
Ease of communication and comfort were the 2 factors that most affected dentists’ preference of the HPD that they were most likely to use in the clinic. Of the evaluated HPDs, dentists ranked the 2 electronic HPDs the highest: DI-15 High-Fidelity Electronic Earplugs HPD was ranked the best overall, followed closely by Music PRO Electronic Earplugs. These devices had similar battery use requirements. It is useful to note that resealing the batteries between uses extended the battery life, when used in a traditional 40-h workweek.
A strength of this study is the variety of demographic characteristics, dental experience, and noise exposure levels among participants. However, participants were not randomly selected and did not represent all dental specialties, and all worked for the VA, potentially limiting the generalizability of these findings. Although the types of handheld powered dental instruments used while wearing HPDs was kept constant, the type of procedure or noise level were not measured, which could bias participants’ perceptions? Each participant wore the HPDs for approximately the same amount of time, but this was not objectively tracked, and varying amount of time spent with each device could influence participants’ comfort or expectations. Age may influence HPD preferences and hearing sensitivity, but this was not assessed. Age is generally correlated with years of dental experience and graduation date, which were collected, and neither was associated with different HPD ratings or preferences. This is an evaluation of clinicians’ perceptions and preferences only; further research is required to quantitatively measure the HPD’s effective noise attenuation and interference with speech intelligibility.
This evaluation found that comfort and ease of communication were the qualities that most influenced HPD choice by dentists, and it demonstrated that commercially available HPDs may be acceptable to dentists. Given that there are devices on the market that allow good communication with patients and colleagues while providing hearing protection, it seems prudent for dentists to consider using HPDs to guard against environmentally induced hearing loss.
Author Contributions
- Spomer, contributed to conception, design, and data acquisition, critically revised the manuscript; C.G. Estrich, contributed to design, data analysis, and interpretation, drafted and critically revised the manuscript; D. Halpin, with respect to the authorship and/or contributed to conception, design, data acquisition, analysis, and interpretation, critically revised the manuscript; R.D. Lipman, contributed to data interpretation, drafted and critically revised the manuscript; M.W.B. Araujo, contributed to data interpretation, critically revised the manuscript. All authors gave final approval and agree to be accountable for all aspects of the work.
Acknowledgments
The American Dental Association acknowledges Drs. Michelle Hamilton, Peter Gerngross, and Craig Ling of the U.S. Department of Veterans Affairs for their assistance in study design and administration, Dr. Helen Ristic, and Nina Koziol for their assistance in survey and study design, and Rashad Vinh for his assistance with battery life testing. The authors received no financial support and declare no potential conflicts of interest publication of this article.
References
Bahannan S, el-Hamid AA, Bahnassy A. 1993. Noise level of dental handpieces and laboratory engines. J Prosthet Dent. 70(4):356–360.
Blackwell DL, Lucas JW, Clarke TC. 2014. Summary health statistics for U.S. adults: National Health Interview Survey, 2012. Vital Health Stat 10. 260:1–161.
Centers for Disease Control and Prevention. 2013. Noise and hearing loss protection [accessed 2017 May 26]. http://www.cdc .gov/niosh/topics/noise/about.html.
Council on Dental Materials and Devices. 1974. Noise control in the dental operatory: Council on Dental Materials and Devices. J Am Dent Assoc. 89(6):1384–1385.
Dalton DS, Cruickshanks KJ, Klein BE, Klein R, Wiley TL, Nondahl DM. 2003. The impact of hearing loss on quality of life in older adults. Gerontologist. 43(5):661–668.
Goncalves CG, Santos L, Lobato D, Ribas A, Lacerda AB, Marques J. 2015. Characterization of hearing thresholds from 500 to 16,000 hz in dentists: a comparative study. Int Arch Otorhinolaryngol. 19(2):156–160.
Lin FR. 2011. Hearing loss and cognition among older adults in the united states. J Gerontol A Biol Sci Med Sci. 66(10):1131–1136.
Lin FR, Ferrucci L, Metter EJ, An Y, Zonderman AB, Resnick SM. 2011. Hearing loss and cognition in the baltimore longitudinal study of aging. Neuropsychology. 25(6):763–770.
Lin FR, Yaffe K, Xia J, Xue QL, Harris TB, Purchase-Helzner E, Satterfield S, Ayonayon HN, Ferrucci L, Simonsick EM, et al. 2013. Hearing loss and cognitive decline in older adults. JAMA Intern Med. 173(4):293–299.
Lopes AC, de Melo AD, Santos CC. 2012. A study of the high-frequency hearing thresholds of dentistry professionals. Int Arch Otorhinolaryngol. 16(2):226–231.
Reddy RK, Welch D, Thorne P, Ameratunga S. 2012. Hearing protection use in manufacturing workers: a qualitative study. Noise Health. 14(59):202–209.
Serafini F, Biasi CSL, Serafini ST, do Rio F, Zinani A. 2003. Sound intensity and audiometric findings in the odontologic practice [accessed 2017 May 26]. http://www .neurootology.org/archives/21.
Sorainen E, Rytkonen E. 2002. High-frequency noise in dentistry. AIHA J (Fairfax, Va). 63(2):231–233.
Stucken EZ, Hong RS. 2014. Noise-induced hearing loss: an occupational medicine perspective. Curr Opin Otolaryngol Head Neck Surg. 22(5):388–393.
Tak S, Davis RR, Calvert GM. 2009. Exposure to hazardous workplace noise and use of hearing protection devices among U.S. workers—NHANES, 1999–2004. Am J Ind Med. 52(5):358–371.
Theodoroff SM, Folmer RL. 2015. Hearing loss associated with long-term exposure to high-speed dental handpieces. Gen Dent. 63(3):71–76.
U.S. Department of Labor. 2013. OSHA technical manual (OTM) chapter—noise [accessed 2017 May 26]. https://www.osha.gov/dts/ osta/otm/new_noise/index.html.
Willershausen B, Callaway A, Wolf TG, Ehlers V, Scholz L, Wolf D, Letzel S. 2014. Hearing assessment in dental practitioners and other academic professionals from an urban setting. Head Face Med. 10:1.