PROFESSIONAL PRACTICE
The Prevalence of Noise-Induced Occupational Hearing Loss in Dentistry Personnel Wandee Khaimook, MD; Puwanai Suksamae, MD; Thitiworn Choosong, PhD; Satit Chayarpham; Ratchada Tantisarasart Occupational hearing loss is the second most common health problem in the industrialized world. Dental personnel exposed to occupational noise may experience hearing loss. This article compares the prevalence of hearing loss in the general population to that of dental personnel exposed to noise during work hours and identifies risk factors for hearing loss among workers at a dental school. This prospective study included 76 dental personnel on the faculty of dentistry at a major university in Asia who were exposed to noise and 76 individuals in a control group. Nearly 16% of the study group and 21% of the control group had lost hearing, a nonsignificant difference (p = .09). Hearing loss was significantly related to work tenure longer than 15 years and age older than 40 years (p < .001). [Workplace Health Saf 2014;62(9):357-360.]
T
he most common cause of sensorineural hearing loss is presbycusis, affecting 35% to 40% of the population older than 65 years (Huang & Tang, 2010). The second most common cause of hearing loss in ABOUT THE AUTHORS
Dr. Khaimook is Assistant Professor, and Dr. Suksamae is from the Department of Otolaryngology Head and Neck Surgery, Faculty of Medicine, Hatyai, Songkla, Thailand. Dr. Choosong is Resident, Occupational Health Unit, Department of Community Medicine, Faculty of Medicine, Hatyai, Songkla, Thailand. Ms. Chayarpham is Assistant Professor and Audiologist, Department of Otolaryngology Head and Neck Surgery, Faculty of Medicine, Hatyai, Songkla, Thailand. Ms. Tantisarasart is Nurse, Faculty of Dentistry, Hatyai, Songkla, Thailand. Submitted: May 31, 2013; Accepted: June 25, 2014; Posted online: September 5, 2014 Supported by the Faculty of Medicine, Hatyai, Songkla, Thailand. The authors have disclosed no potential conflicts, financial or otherwise. Correspondence: Wandee Khaimook, MD, Department of Otolaryngology Head and Neck Surgery, Faculty of Medicine, Prince of Songklanagarind University, Hatyai, Songkla 90110, Thailand. E-mail: [email protected] doi:10.3928/21650799-20140815-02
this population, occupational noise-induced hearing loss, accounts for 7% to 16% of disabling hearing loss (Dube, Ingale, & Ingale, 2011; Engdahl & Tambs, 2010; Krishnamurti, 2009). The extent of hearing loss depends on the intensity of the noise and duration of noise exposure. The Occupational Safety and Health Administration (OSHA), an agency of the United States Department of Labor, requires employers to develop and implement surveillance programs when employees are exposed to noise levels of 85 dB or greater over 8 working hours (Brusis, Hilger, Niggeloh, Huedepohl, & Thiesen, 2008; Wazzan, Qahtani, Shethri, Muhaimeed, & Khan, 2005). Instruments in dentistry produce dangerously loud noise, which may contribute to hearing loss. Long-term exposure to noise levels above 80 to 85 dB carries an increased risk of hearing loss (Setcos & Mahyuddin, 1998; Verbeek, Kateman, Morata, Dreschler, & Sorgdrager, 2009).
The health problems of 220 dentists in southern Thailand were studied using self-report questionnaires (Chowanadisai, Kukiattrakoon, Yapong, Kedjarune, & Leggat, 2000; Leggat, Chowanadisai, Kedjarune, Kukiattrakoon, & Yapong, 2001; Leggat, Chowanadisai, Kukiattrakoon, Yapong, & Kedjarune, 2001). The most common problems identified by the dentists were musculoskeletal pain (78%), eye problems (15%), and hearing loss (3%). This study was designed to determine the prevalence of hearing loss in the general population and among dental personnel exposed to instrument noise during working hours, identify noise levels in work areas in a dental school, and identify risk factors of hearing loss. METHODS This descriptive study, conducted between May and December 2010, assessed 76 dental personnel such as dentists, dental technicians, and dental assistants on the Faculty of Dentistry of a major university in Asia who were exposed to noise during work hours and 76 individuals in a control group who had no history of noise exposure. Inclusion criteria for the experimental group included dental personnel who had been on the Faculty of Dentistry for more than 1 year and were younger than 50 years. The control group was selected from the faculty and staff in the Faculty of Medicine, were younger than 50 years, and had no history of ear prob-
WORKPLACE HEALTH & SAFETY • VOL. 62, NO. 9, 2014 Downloaded from whs.sagepub.com at UNIV OF GEORGIA LIBRARIES on August 29, 2015
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TABLE 1
Demographic Data Characteristic
Dental Personnel Number (%) (n = 76)
Control Number (%) (n = 76)
Sex
p .512
Male
6 (7.9)
4 (5.3)
70 (92.1)
72 (94.7)
21 to 30
9 (11.8)
9 (11.8)
31 to 35
11 (14.5)
10 (13.2)
36 to 40
21 (27.6)
18 (23.7)
41 to 45
24 (31.6)
27 (35.5)
46 to 50
11 (14.5)
12 (15.8)
Female Age (years)
.973
Statistical Analysis
TABLE 2
Prevalence of Hearing Loss in Dental Personnel and Controls Number
Number With Hearing Loss (%)
p
Dental personnel
76
12 (15.7)
.09
Profession Dentist
31
8 (25.8)
Dental technician
4
1 (25.0)
Dental assistant
41
3 (7.3)
Control
76
16 (21.0)
lems and noise exposure during work hours. Exclusion criteria for both groups included history of chronic ear disease, ear surgery, ear trauma, ototoxic drugs, or previous sensorineural hearing loss. Data Collection
The researchers contacted all of the dental personnel in the Faculty of Dentistry via e-mail to explain the effect of instrument noise on hearing and invited them to participate in this study. Those who agreed to participate were divided into age groups (21 to 30, 31 to 35, 36 to 40, 41 to 45, and 46 to 50 years). The control group was solicited through an announcement to the personnel in the Faculty of Medicine personnel. Volunteers who had no workplace noise exposure and matched the same age groups of the dental per-
358
audiometry testing. Audiometric examinations were performed using an audiometer (Model RT 150; Glaser Instruments AG, Zurich, Switzerland) in a sound-proof room and calibrated to the International Standard Organization (1964). Air conduction hearing thresholds were measured by pure tone audiometry at the following frequencies: 0.5, 1, 2, 3, 4, 6, and 8 kHz. Pure tone average at 3, 4, and 6 kHz reflects the frequency range most susceptible to noise-induced hearing loss. A loss of more than 25 dB in these frequencies is considered abnormal.
sonnel were invited to join this study. Participants who fulfilled the inclusion criteria completed a demographic questionnaire and received otoscopic and hearing examinations after providing written informed consent. Data collected by the researchers included age, sex, job title (dentists, dental technicians, or dental assistants), duration of work experience (< 5 years, 5 to 10 years, 10 to 15 years, or > 15 years), actual number of hours exposed to loud noise each day (< 3 hours, 3 to 6 hours, or > 6 hours), and noise intensity level in each dental clinic measured by sound level meters (Rion NL-31; Rion, Tokyo, Japan and SoundPro SE-DL; Quest, Oconomowoc, WI) with octave band frequency analysis. All participants received otoscopic examinations and pure tone
The data were analyzed using R software version 2.13.1 (R Development Core Team, 2011) to determine the prevalence of hearing loss for dental personnel and the control group. The effects of the occupation on hearing loss were calculated via univariate analysis. Fisher’s exact test was used to determine risk factors for hearing loss based on type of work, worker’s age, actual hours exposed to noise each day, and noise intensity in each dental clinic. RESULTS The ages of the 76 dental personnel ranged from 25 to 50 years (average age: 39 years) and included 6 men and 70 women. In the control group, the ages ranged from 23 to 50 years (average age: 39 years) and included 4 men and 72 women (Table 1). The dental personnel group included 31 dentists, 41 dental assistants, and 4 technicians. The prevalence of hearing loss was 8 in 31 dentists (25.8%), 1 in 4 dental technicians (25%), and 3 in 41 dental assistants (7.3%). Noise-induced hearing loss was 15.7% for dental personnel and 21% for the control group. No significant difference was found between the two groups in terms of noise-induced hearing loss prevalence (p > .05) (Table 2). In the dental personnel group, dentists and dental technicians had greater prevalence of sensorineural hearing loss than dental assistants. Table 3 lists potential risk factors for hearing loss in the dental personnel group. Sensorineural hearing loss
Copyright © American Association of Occupational Health Nurses, Inc. Downloaded from whs.sagepub.com at UNIV OF GEORGIA LIBRARIES on August 29, 2015
PROFESSIONAL PRACTICE
was significantly related to the duration of work tenure and age: more than 15 years (p = .002) and older than 40 years (p = .0003). No significant differences were found with the other demographic variables. In the dental school, the noise intensity in all dental clinics ranged from 49.7 to 58.1 dBA. The noisiest work area was in the dental laboratory (58.1 dBA). DISCUSSION Occupational noise-induced hearing loss is defined as bilateral sensorineural hearing loss that develops slowly over a period of several years as the result of exposure to continuous or intermittent loud noise in the work place. Environmental noise is responsible for hearing loss when workers endure noise exposure for 8 hours to levels above 85 dB (Messano & Petti, 2012). The first sign of hearing loss from noise exposure is typically a “notching” of the audiogram at 3,000, 4,000, or 6,000 Hz greater than 25 dB, with recovery at 8,000 Hz (Bali, Acharya, & Anup, 2007; Jones, 1996; Krishnamurti, 2009; Verbeek et al., 2009). Figure 1 illustrates notching in the audiogram of the left ear. Some researchers have reported that the three most common occupational health problems are low back pain (54.0%), vision problems (52.3%), and auditory disorders (19.6%) (Gijbels, Jacobs, Princen, Nackaerts, & Debruyne, 2006). Bali et al. (2007) stated that the noise generated in a dental clinic should not be underestimated. Three questionnairebased surveys reported the percentage of dentists experiencing hearing problems in Thailand (11.3%), Belgium (19.6%), and the United Arab Emirates (5%) (Messano & Petti, 2012). Ten years of noise exposure at the level of 100 dB will raise the probability of hearing impairment from 94.5% to 99.5% (Verbeek et al., 2009). Some studies have suggested that hearing loss among dentists appeared to be higher than among a control group in the high frequency range (4,000 to 6,000 Hz), but in other studies dentists’ impairment did not exceed the hearing loss of a control group (Lehto,
TABLE 3
Risk Factors That May Influence Hearing Loss Risk Factor
Number
Number With Hearing Loss (%)
Duration of working experience (years)
p .002
< 15
29
0 (0)
≥ 15
47
12 (25.6)
< 40
34
0 (0)
≥ 40
42
12 (28.6)
Age (years)
.0003
Duration of time exposed to noise per day (hours)
.518
3 to 6
48
9 (18.8)
>6
28
3 (10.7)
Noise intensity in dental clinics by sound level meters (dBA)
.242
Pedodontic (55.2)
6
1 (16.7)
Undergraduate student (54.9)
28
4 (14.3)
Graduate student (50.1)
2
0 (0)
Prosthodontic (54.7)
11
2 (18.2)
Oral surgery (53.4)
6
1 (16.7)
Orthodontic (49.7)
7
1 (14.3)
Dental service (57.3)
12
2 (16.7)
Laboratory (58.1)
4
1 (25)
Figure 1. Audiograms showing hearing loss notching in the left ear.
Laurikainen, Aitasalo, Pietila, Helenius & Johansson, 1989; Reitemeier & Fristche, 1990).
The prevalence of noise-induced hearing loss in dental personnel has been reported to range from 7% to
WORKPLACE HEALTH & SAFETY • VOL. 62, NO. 9, 2014 Downloaded from whs.sagepub.com at UNIV OF GEORGIA LIBRARIES on August 29, 2015
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PROFESSIONAL PRACTICE
16% in the literature (Dube et al., 2011; Engdahl & Tambs, 2010; Krishnamurti, 2009). This study revealed the prevalence of hearing loss in dental personnel to be 15.7%; however, no significant difference was found when compared to the control group. Several factors put dental personnel at risk for hearing loss, including work tenure, age, actual hours exposed to noise per day, and sound intensity in each dental clinic. This study showed the risk factors for noised-induced hearing loss were significantly related to work tenure of more than 15 years and workers 40 years or older. It is possible that in the past, noise levels were higher in dental clinics. In the work areas of the dental school, average daily noise intensity was 49.7 to 58.1 dBA, which is generally considered safe (Wazzan et al., 2005). Therefore, dental drill noise was insufficient to cause noise-induced hearing loss and dental personnel are likely not at risk unless they experience noise in other areas of their lives. IMPLICATIONS FOR OCCUPATIONAL HEALTH NURSING PRACTICE Occupational and environmental health nurses who have the opportunity to work with dental personnel can advise them to protect their hearing when they are exposed to noise, both at work and away from work. For dental personnel who are concerned about possible work exposure to noise, the occupational health nurse can recommend environmental sound monitoring to determine if workers should be placed in a hearing conservation program. This study
360
suggests that workplace noise is not a risk factor for dental personnel, but they may have noise exposure outside of work that requires use of personal protective devices. CONCLUSION Research shows that dental personnel are exposed to workplace noise. This study evaluated the sound levels of a dental clinic environment and compared the prevalence of sensorineural hearing loss in dental personnel with that of medical personnel. Risk factors for hearing loss among dental personnel included age older than 40 years and career length greater than 15 years. No significant difference was found between dental personnel and the control group for noise-induced hearing loss. REFERENCES
Bali, N., Acharya, S., & Anup, N. (2007). An assessment of the effect of sound produced in a dental clinic on the hearing of dentists. Oral Health & Preventive Dentistry, 5, 187-191. Brusis, T., Hilger, R., Niggeloh, R., Huedepohl, J., & Thiesen, K. W. (2008). Are professional dental health care workers (dentists, dental technicians, assistants) in danger of noised induced hearing loss? [article in German]. Laryngo-Rhino-Otologie, 87, 335-340. Chowanadisai, S., Kukiattrakoon, B., Yapong, B., Kedjarune, U., & Leggat, P. A. (2000). Occupational health of dentists in southern Thailand. International Dental Journal, 50, 36-40. Dube, K. J., Ingale, L. T., & Ingale, S. T. (2011). Hearing impairment among workers exposed to excessive levels of noise in Ginning industries. Noise & Health, 13, 348-355. Engdahl, B., & Tambs, K. (2010). Occupation and the risk of hearing impairment: Results from the Nord-Trondelag Hearing Loss Study. Scandinavian Journal of Work, Environment & Health, 36, 250-257. Gijbels, F., Jacobs, R., Princen, K., Nackaerts, O., & Debruyne, F. (2006). Potential oc-
cupational health problems for dentists in Flanders, Belgium. Clinical Oral Investigations, 10, 8-16. Huang, Q., & Tang, J. (2010). Age-related hearing loss or presbycusis. European Archives of Oto-Rhino-Laryngology, 267, 1179-1191. Jones, C. M. (1996). ABC of work related disorders: Occupational hearing loss and vibration induced disorders. British Medical Journal, 313, 223-226. Krishnamurti, S. (2009). Sensorineural hearing loss associated with occupational noise exposure: Effects of age-corrections. International Journal of Environmental Research and Public Health, 6, 889-899. Leggat, P. A., Chowanadisai, S., Kedjarune, U., Kukiattrakoon, B., & Yapong, B. (2001). Health of dentists in southern Thailand. International Dental Journal, 51, 348-352. Leggat, P. A., Chowanadisai, S., Kukiattrakoon, B., Yapong, B., & Kedjarune, U. (2001). Occupational hygiene practices of dentists in southern Thailand. International Dental Journal, 51, 11-16. Lehto, T. U., Laurikainen, E. T., Aitasalo, K. J., Pietila, T. J., Helenius, H. Y., & Johansson, R. (1989). Hearing of dentists in the long run: A 15- year follow up study. Community Dentistry Oral Epidemiology, 17, 207-211. Messano, G. A., & Petti, S. (2012). General dental practitioners and hearing impairment. Journal of Dentistry, 40, 821-828. R Development Core Team. (2011). A language and environment for statistical computing. Vienna: Author. Reitemeier, B., & Fristche, F. (1990). The long term effects of noise on dentists [article in German]. Zahn-Mund-Kieferheilkd Zentralbl, 78, 735-738. Setcos, J. C., & Mahyuddin, A. (1998). Noise levels encountered in dental clinical and laboratory practice. The International Journal of Prosthodontics, 11, 150-157. Verbeek, J. H., Kateman, E., Morata, T. C., Dreschler, W., & Sorgdrager, B. (2009). Interventions to prevent occupational noise induced hearing loss. Cochrane Database Systematic Reviews, 8, CD006396. Wazzan, K. A. A., Qahtani, M. Q. A., Shethri, S. E. A., Muhaimeed, H. A. S., & Khan, N. (2005). Hearing problems among dental personnel. Journal of the Pakistan Dental Association, 14, 210-214.
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The Prevalence of Noise-Induced Occupational Hearing Loss in Dentistry Personnel Wandee Khaimook, MD; Puwanai Suksamae, MD; Thitiworn Choosong, PhD; Satit Chayarpham; Ratchada Tantisarasart Occupational hearing loss is the second most common health problem in the industrialized world. Dental personnel exposed to occupational noise may experience hearing loss. This article compares the prevalence of hearing loss in the general population to that of dental personnel exposed to noise during work hours and identifies risk factors for hearing loss among workers at a dental school. This prospective study included 76 dental personnel on the faculty of dentistry at a major university in Asia who were exposed to noise and 76 individuals in a control group. Nearly 16% of the study group and 21% of the control group had lost hearing, a nonsignificant difference (p = .09). Hearing loss was significantly related to work tenure longer than 15 years and age older than 40 years (p < .001). [Workplace Health Saf 2014;62(9):357-360.]
T
he most common cause of sensorineural hearing loss is presbycusis, affecting 35% to 40% of the population older than 65 years (Huang & Tang, 2010). The second most common cause of hearing loss in ABOUT THE AUTHORS
Dr. Khaimook is Assistant Professor, and Dr. Suksamae is from the Department of Otolaryngology Head and Neck Surgery, Faculty of Medicine, Hatyai, Songkla, Thailand. Dr. Choosong is Resident, Occupational Health Unit, Department of Community Medicine, Faculty of Medicine, Hatyai, Songkla, Thailand. Ms. Chayarpham is Assistant Professor and Audiologist, Department of Otolaryngology Head and Neck Surgery, Faculty of Medicine, Hatyai, Songkla, Thailand. Ms. Tantisarasart is Nurse, Faculty of Dentistry, Hatyai, Songkla, Thailand. Submitted: May 31, 2013; Accepted: June 25, 2014; Posted online: September 5, 2014 Supported by the Faculty of Medicine, Hatyai, Songkla, Thailand. The authors have disclosed no potential conflicts, financial or otherwise. Correspondence: Wandee Khaimook, MD, Department of Otolaryngology Head and Neck Surgery, Faculty of Medicine, Prince of Songklanagarind University, Hatyai, Songkla 90110, Thailand. E-mail: [email protected] doi:10.3928/21650799-20140815-02
this population, occupational noise-induced hearing loss, accounts for 7% to 16% of disabling hearing loss (Dube, Ingale, & Ingale, 2011; Engdahl & Tambs, 2010; Krishnamurti, 2009). The extent of hearing loss depends on the intensity of the noise and duration of noise exposure. The Occupational Safety and Health Administration (OSHA), an agency of the United States Department of Labor, requires employers to develop and implement surveillance programs when employees are exposed to noise levels of 85 dB or greater over 8 working hours (Brusis, Hilger, Niggeloh, Huedepohl, & Thiesen, 2008; Wazzan, Qahtani, Shethri, Muhaimeed, & Khan, 2005). Instruments in dentistry produce dangerously loud noise, which may contribute to hearing loss. Long-term exposure to noise levels above 80 to 85 dB carries an increased risk of hearing loss (Setcos & Mahyuddin, 1998; Verbeek, Kateman, Morata, Dreschler, & Sorgdrager, 2009).
The health problems of 220 dentists in southern Thailand were studied using self-report questionnaires (Chowanadisai, Kukiattrakoon, Yapong, Kedjarune, & Leggat, 2000; Leggat, Chowanadisai, Kedjarune, Kukiattrakoon, & Yapong, 2001; Leggat, Chowanadisai, Kukiattrakoon, Yapong, & Kedjarune, 2001). The most common problems identified by the dentists were musculoskeletal pain (78%), eye problems (15%), and hearing loss (3%). This study was designed to determine the prevalence of hearing loss in the general population and among dental personnel exposed to instrument noise during working hours, identify noise levels in work areas in a dental school, and identify risk factors of hearing loss. METHODS This descriptive study, conducted between May and December 2010, assessed 76 dental personnel such as dentists, dental technicians, and dental assistants on the Faculty of Dentistry of a major university in Asia who were exposed to noise during work hours and 76 individuals in a control group who had no history of noise exposure. Inclusion criteria for the experimental group included dental personnel who had been on the Faculty of Dentistry for more than 1 year and were younger than 50 years. The control group was selected from the faculty and staff in the Faculty of Medicine, were younger than 50 years, and had no history of ear prob-
WORKPLACE HEALTH & SAFETY • VOL. 62, NO. 9, 2014 Downloaded from whs.sagepub.com at UNIV OF GEORGIA LIBRARIES on August 29, 2015
357
PROFESSIONAL PRACTICE
TABLE 1
Demographic Data Characteristic
Dental Personnel Number (%) (n = 76)
Control Number (%) (n = 76)
Sex
p .512
Male
6 (7.9)
4 (5.3)
70 (92.1)
72 (94.7)
21 to 30
9 (11.8)
9 (11.8)
31 to 35
11 (14.5)
10 (13.2)
36 to 40
21 (27.6)
18 (23.7)
41 to 45
24 (31.6)
27 (35.5)
46 to 50
11 (14.5)
12 (15.8)
Female Age (years)
.973
Statistical Analysis
TABLE 2
Prevalence of Hearing Loss in Dental Personnel and Controls Number
Number With Hearing Loss (%)
p
Dental personnel
76
12 (15.7)
.09
Profession Dentist
31
8 (25.8)
Dental technician
4
1 (25.0)
Dental assistant
41
3 (7.3)
Control
76
16 (21.0)
lems and noise exposure during work hours. Exclusion criteria for both groups included history of chronic ear disease, ear surgery, ear trauma, ototoxic drugs, or previous sensorineural hearing loss. Data Collection
The researchers contacted all of the dental personnel in the Faculty of Dentistry via e-mail to explain the effect of instrument noise on hearing and invited them to participate in this study. Those who agreed to participate were divided into age groups (21 to 30, 31 to 35, 36 to 40, 41 to 45, and 46 to 50 years). The control group was solicited through an announcement to the personnel in the Faculty of Medicine personnel. Volunteers who had no workplace noise exposure and matched the same age groups of the dental per-
358
audiometry testing. Audiometric examinations were performed using an audiometer (Model RT 150; Glaser Instruments AG, Zurich, Switzerland) in a sound-proof room and calibrated to the International Standard Organization (1964). Air conduction hearing thresholds were measured by pure tone audiometry at the following frequencies: 0.5, 1, 2, 3, 4, 6, and 8 kHz. Pure tone average at 3, 4, and 6 kHz reflects the frequency range most susceptible to noise-induced hearing loss. A loss of more than 25 dB in these frequencies is considered abnormal.
sonnel were invited to join this study. Participants who fulfilled the inclusion criteria completed a demographic questionnaire and received otoscopic and hearing examinations after providing written informed consent. Data collected by the researchers included age, sex, job title (dentists, dental technicians, or dental assistants), duration of work experience (< 5 years, 5 to 10 years, 10 to 15 years, or > 15 years), actual number of hours exposed to loud noise each day (< 3 hours, 3 to 6 hours, or > 6 hours), and noise intensity level in each dental clinic measured by sound level meters (Rion NL-31; Rion, Tokyo, Japan and SoundPro SE-DL; Quest, Oconomowoc, WI) with octave band frequency analysis. All participants received otoscopic examinations and pure tone
The data were analyzed using R software version 2.13.1 (R Development Core Team, 2011) to determine the prevalence of hearing loss for dental personnel and the control group. The effects of the occupation on hearing loss were calculated via univariate analysis. Fisher’s exact test was used to determine risk factors for hearing loss based on type of work, worker’s age, actual hours exposed to noise each day, and noise intensity in each dental clinic. RESULTS The ages of the 76 dental personnel ranged from 25 to 50 years (average age: 39 years) and included 6 men and 70 women. In the control group, the ages ranged from 23 to 50 years (average age: 39 years) and included 4 men and 72 women (Table 1). The dental personnel group included 31 dentists, 41 dental assistants, and 4 technicians. The prevalence of hearing loss was 8 in 31 dentists (25.8%), 1 in 4 dental technicians (25%), and 3 in 41 dental assistants (7.3%). Noise-induced hearing loss was 15.7% for dental personnel and 21% for the control group. No significant difference was found between the two groups in terms of noise-induced hearing loss prevalence (p > .05) (Table 2). In the dental personnel group, dentists and dental technicians had greater prevalence of sensorineural hearing loss than dental assistants. Table 3 lists potential risk factors for hearing loss in the dental personnel group. Sensorineural hearing loss
Copyright © American Association of Occupational Health Nurses, Inc. Downloaded from whs.sagepub.com at UNIV OF GEORGIA LIBRARIES on August 29, 2015
PROFESSIONAL PRACTICE
was significantly related to the duration of work tenure and age: more than 15 years (p = .002) and older than 40 years (p = .0003). No significant differences were found with the other demographic variables. In the dental school, the noise intensity in all dental clinics ranged from 49.7 to 58.1 dBA. The noisiest work area was in the dental laboratory (58.1 dBA). DISCUSSION Occupational noise-induced hearing loss is defined as bilateral sensorineural hearing loss that develops slowly over a period of several years as the result of exposure to continuous or intermittent loud noise in the work place. Environmental noise is responsible for hearing loss when workers endure noise exposure for 8 hours to levels above 85 dB (Messano & Petti, 2012). The first sign of hearing loss from noise exposure is typically a “notching” of the audiogram at 3,000, 4,000, or 6,000 Hz greater than 25 dB, with recovery at 8,000 Hz (Bali, Acharya, & Anup, 2007; Jones, 1996; Krishnamurti, 2009; Verbeek et al., 2009). Figure 1 illustrates notching in the audiogram of the left ear. Some researchers have reported that the three most common occupational health problems are low back pain (54.0%), vision problems (52.3%), and auditory disorders (19.6%) (Gijbels, Jacobs, Princen, Nackaerts, & Debruyne, 2006). Bali et al. (2007) stated that the noise generated in a dental clinic should not be underestimated. Three questionnairebased surveys reported the percentage of dentists experiencing hearing problems in Thailand (11.3%), Belgium (19.6%), and the United Arab Emirates (5%) (Messano & Petti, 2012). Ten years of noise exposure at the level of 100 dB will raise the probability of hearing impairment from 94.5% to 99.5% (Verbeek et al., 2009). Some studies have suggested that hearing loss among dentists appeared to be higher than among a control group in the high frequency range (4,000 to 6,000 Hz), but in other studies dentists’ impairment did not exceed the hearing loss of a control group (Lehto,
TABLE 3
Risk Factors That May Influence Hearing Loss Risk Factor
Number
Number With Hearing Loss (%)
Duration of working experience (years)
p .002
< 15
29
0 (0)
≥ 15
47
12 (25.6)
< 40
34
0 (0)
≥ 40
42
12 (28.6)
Age (years)
.0003
Duration of time exposed to noise per day (hours)
.518
3 to 6
48
9 (18.8)
>6
28
3 (10.7)
Noise intensity in dental clinics by sound level meters (dBA)
.242
Pedodontic (55.2)
6
1 (16.7)
Undergraduate student (54.9)
28
4 (14.3)
Graduate student (50.1)
2
0 (0)
Prosthodontic (54.7)
11
2 (18.2)
Oral surgery (53.4)
6
1 (16.7)
Orthodontic (49.7)
7
1 (14.3)
Dental service (57.3)
12
2 (16.7)
Laboratory (58.1)
4
1 (25)
Figure 1. Audiograms showing hearing loss notching in the left ear.
Laurikainen, Aitasalo, Pietila, Helenius & Johansson, 1989; Reitemeier & Fristche, 1990).
The prevalence of noise-induced hearing loss in dental personnel has been reported to range from 7% to
WORKPLACE HEALTH & SAFETY • VOL. 62, NO. 9, 2014 Downloaded from whs.sagepub.com at UNIV OF GEORGIA LIBRARIES on August 29, 2015
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PROFESSIONAL PRACTICE
16% in the literature (Dube et al., 2011; Engdahl & Tambs, 2010; Krishnamurti, 2009). This study revealed the prevalence of hearing loss in dental personnel to be 15.7%; however, no significant difference was found when compared to the control group. Several factors put dental personnel at risk for hearing loss, including work tenure, age, actual hours exposed to noise per day, and sound intensity in each dental clinic. This study showed the risk factors for noised-induced hearing loss were significantly related to work tenure of more than 15 years and workers 40 years or older. It is possible that in the past, noise levels were higher in dental clinics. In the work areas of the dental school, average daily noise intensity was 49.7 to 58.1 dBA, which is generally considered safe (Wazzan et al., 2005). Therefore, dental drill noise was insufficient to cause noise-induced hearing loss and dental personnel are likely not at risk unless they experience noise in other areas of their lives. IMPLICATIONS FOR OCCUPATIONAL HEALTH NURSING PRACTICE Occupational and environmental health nurses who have the opportunity to work with dental personnel can advise them to protect their hearing when they are exposed to noise, both at work and away from work. For dental personnel who are concerned about possible work exposure to noise, the occupational health nurse can recommend environmental sound monitoring to determine if workers should be placed in a hearing conservation program. This study
360
suggests that workplace noise is not a risk factor for dental personnel, but they may have noise exposure outside of work that requires use of personal protective devices. CONCLUSION Research shows that dental personnel are exposed to workplace noise. This study evaluated the sound levels of a dental clinic environment and compared the prevalence of sensorineural hearing loss in dental personnel with that of medical personnel. Risk factors for hearing loss among dental personnel included age older than 40 years and career length greater than 15 years. No significant difference was found between dental personnel and the control group for noise-induced hearing loss. REFERENCES
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