# Evaluation of Noise Levels in a University Dental Clinic
## 5 Discussion  
This study reports on estimated noise exposure assessments in undergraduate, postgraduate, and laboratory settings in the Department of Dentistry, School of Health Sciences of the National and Kapodistrian University of Athens, Greece. The settings had varied characteristics, as some had renovated dental equipment and others had units more than 15-30 years old, either in a clinical or laboratory environment. Overall, noise measurement findings were within the recommended limit values for dental equipment (47.5 to 80.8 dB(A) and corresponded to previous reports for noise estimation in university dental clinics and laboratories [39-42, 57, 58]. To mention accordingly, in India for example, it was concluded that the mean noise levels in the working clinics ranged from 63.0 dB(A) to 81.5 dB(A) [39] and 54 dB(A) to 83.3 dB(A) [58]. In Saudi Arabia, an overall noise level of 73.83 \(\pm\) 4.39 dB within the dental clinical setting was calculated [57]; in Casablanca, noise levels were between 69.35 dB(A) and 72.07 dB(A) [42]; in Hong Kong, it was between 62.6 dB(A) and 67.7 dB(A) [41]. Previously, [PERSON] et al. [39] in their measurements showed a variation of 63.0 dB(A) to 81.5 dB(A) in the noise levels. The highest noise levels ever recorded so far were at the dental college of Damascus University, where the noise levels reached 96 dB(A) while using the sandblaster [27], and in Michigan's pediatric university clinic, where the noise levels peaked at 103.5 dB(A) [40]. The personal exposure measurements in all settings were noisier than static area measurements when both air scaler/ultrasonic and airotor/micmotor were used, suggesting that in cases of constant use of all types of handpieces and water suction equipment, students should use hearing protectors on-site. Further, we should mention that the choice of timing in this study was in accordance with the patients' inflow to the clinic where the peak working flow for each setting was used to avoid bias in measurements. The results indicated that the time of measurement had no influence on the sound generated when patients were being treated, as different hours consisted of the peak workflow in each clinic. This is in accordance with other findings [40]. In postgraduate clinics, despite new units on site, the noise levels did not differ from those found in undergraduate clinics with the old equipment, possibly due to the heavier workload performed by postgraduate students, as also mentioned elsewhere [27, 40]. Furthermore, a comparison between data from the UG and PG clinics revealed that the high noise levels in PG settings were attributed mainly to suction units which are found next to each unit. When designing dental clinics, it is important to consider incorporating a central high-volume evacuation (HVE) unit instead of using separate units attached to each dental unit. Additionally, a silencer design for the main HVE should also be taken into consideration. Suction alone was equally noisy compared to suction using airotor/micomotor, whereas suction using an ultrasonic handpiece was noisier, as mentioned elsewhere [27]. Additionally, it is important to mention that in the PG settings, there were statistically important differences in the noise levels produced from different specialty treatments, with the therapeutic department being noisier than the prosthetics department, as also reported in a study by [PERSON] et al. [58]. Elevated noise levels in chairside settings were reported either in undergraduate (UG) or postgraduate (PG) clinics when ultrasonic handpieces with suction were used. This finding is consistent with previous research [59]. Since this previous reading of 85.8 dB(A), compared to our 80.8 dB(A), and that of [PERSON] et al. [57] where the use of a scaler and high-vacuum saliva ejector created a maximum noise of 71.39 dB(A), and the scaler alone produced a minimum noise of 68.53 dB(A), it seems that ultrasonic handpieces still need redesigning to further diminish noise production.