Evaluation of Hearing Status in Employees of Dental Prosthodontics Laboratories in Yazd

Noise Induced Hearing Loss (NIHL) is the first cause of acquired hearing loss. Dentists and dental prosthodontics technicians are exposed to different sounds produced by a variety of devices in their occupations. In this study, we studied the effect of dental prosthesis sounds on the auditory power of the respective staff.

This case-control study was carried out among all technicians of dental prosthesis laboratories in Yazd in 2018 selected by census sampling method. A total of 23 technicians who were willing to cooperate and met the inclusion criteria were included in the experimental group. Furthermore,  23 people who referred to the audiology clinic, were matched with the experimental group in terms of age and gender, and were not working in noisy environment, and had no congenital or acquired deafness were examined as the control group.  Finally, the collected data were analyzed by SPSS version 19 using statistical tests.

The mean hearing threshold of the right ear at frequencies of 3000 and 4000 Hz and the mean hearing threshold of the left ear at frequencies of 3000, 4000, 6000, and 8000 Hz was significantly higher in the experimental than the control group. The mean hearing threshold of the right ear at the frequency of 4000 Hz and the hearing threshold of the left ear at frequencies of 3000, 4000, and 6000 Hz in participants with job history>4 years was significantly higher. Furthermore, the mean hearing threshold of the right ear in the frequency of 4000 Hz and the hearing threshold of the left ear at frequencies of 3000, 4000, and 6000 Hz years was significantly higher in people with job history >30 years.

According to findings, the staffs working in dental prosthodontics laboratories suffer from NIHL at frequencies of 3000 to 8000 Hz. The hearing loss in the left ear was more severe  in  people with job history of >30 years and in people with job history of > 4 years.Therefore, the use of hearing impaired and hearing protectors is recommended in these people.