The effect of industrial noise on teeth.

Continuous exposure to industrial noise, rich in low-frequency noise (LFN) components, can cause the abnormal proliferation of extracellular matrices. Studies have shown alterations in oral tissues. Noise is a powerful stressor. Parafunctional habits are a self-destructive process caused by stress that induces hyperactivity of masticatory muscles, teeth grinding, leading to progressive dental wear. Teeth usually respond to injuries by forming tertiary dentine. The aim of this study was to ascertain the effects of industrial noise on teeth, namely tooth wear and tertiary dentine formation. Thirty adult Wistar rats were divided into 3 experimental groups of 10 animals, and exposed to industrial noise for 1, 3 and 7 months, with a weekly average of 40 h of exposure. A further 10 animals served as controls. We extracted the molars and 126 teeth were processed for light microscopy. The area of the cusps was measured. A further 44 teeth were processed for electron microscopy, analyzed using fieldemission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). Eight teeth were prepared for immunogold and field-emission in-lens scanning electron microscopy (FEI-SEM) and observed for collagen I. The average area of the molar cusps differed significantly between exposed and controls animals. The most striking differences occurred between month 1 and 3. FESEM results showed a 2.0 to 6.0 mm-wide mineral band in the roof of the pulp chamber of the animals exposed. EDS showed that the band is hydroxyapatite, tertiary dentine. Study of collagen fibers showed proliferation and disorganization on the exposed animals’ circumpulpar dentine. Significant tooth wear correlated with exposure time and was significantly higher in the first 3 months. With LFN exposure there is formation of tertiary dentine and our results strongly suggest that this stimulus is important in the pathogenesis of tooth wear.