RESUMEN
INTRODUCTION: Sleep bruxism as nocturnal parafunction, also known as tooth grinding, is the most common parasomnia (sleep disorder). Most tooth grinding occurs during rapid eye movement - REM sleep. Sleep bruxism is an oral habit characterized by rhythmic activity of the masticatory muscles (m. masseter) that causes forced contact between dental surfaces during sleep. Sleep bruxism has been associated with craniomandibular disorders including temporomandibular joint discomfort, pulpalgia, premature loss of teeth due to excessive attrition and mobility, headache, muscle ache, sleep interruption of an individual and problems with removable and fixed denture. Basically, two groups of etiological factors can be distinguished, viz., peripheral (occlusal) factors and central (pathophysiological and psychological) factors. The role of occlusion (occlusal discrepancies) as the causative factor is not enough mentioned in relation to bruxism. OBJECTIVE: The main objective of this paper was to evaluate the connection between occlusal factors and nocturnal parafunctional activities (occlusal disharmonies and bruxism). METHOD: Two groups were formed- experimental of 15 persons with signs and symptoms of nocturnal parafunctional activity of mandible (mean age 26.6 years) and control of 42 persons with no signs and symptoms of bruxism (mean age 26.3 yrs.). The computerized occlusal analyses were performed using the T-Scan II system (Tekscan, Boston, USA). 2D occlusograms were analyzed showing the occlusal force, the center of the occlusal force with the trajectory and the number of antagonistic tooth contacts. RESULTS: Statistically significant difference of force distribution was found between the left and the right side of the arch (L%-R%) (t=2.773; p<0.02) in the group with bruxism. The difference of the centre of occlusal force - COF trajectory between the experimental and control group was not significant, but the trajectory of COF was longer in the group of bruxists (67.3+24.4mm). In addition, the significant difference of COF position in relation to the center of the elliptic fields was not found in bruxists (chi-squared=1.63; p> 0.05), but obtained results directly revealed uneven distribution of the occlusal forces which caused the excessive attrition and mobility of tooth. CONCLUSION: Our study failed to find direct correlation between occlusal factors and bruxism, so they are basically contributing factors.