The influence of occlusal morphology on occlusion time.

OBJECTIVES: The aim of the study was to assess how the morphology of the occlusal surfaces of premolars and molars influenced the occlusion time in a mixed gender group of young adults with full natural dentition. METHODS: Fifty healthy volunteers with Angle's Class I occlusion were included in the study. After clinical examination, the alginate impressions of both arches were taken, and plaster casts were prepared. To assess the morphology of lateral teeth, the digital models were measured. Occlusal analysis was performed with the T-Scan® III to assess occlusion time. RESULTS: A direct correlation was found between the cusp distance for the first upper premolar and occlusion time (r = -0.29, p<0.05) and the distance between distal buccal and distal lingual cusps of the first lower premolar and occlusion time (r = 0.33, p<0.05). The parameters that had their impact on occlusion time were the opening angle of lingual cusps for the lower molars and the furrow angle of aperture between cusps for first upper premolar. DISCUSSION: Occlusal surface morphologies of premolars may have direct impact on occlusion time. However, anterior guidance parameters and morphologies of molars could also influence the time teeth are in contact coming to maximal intercuspation.

Effect of the dental arches morphology on the masticatory muscles activities in normal occlusion young adults.

OBJECTIVES: The aim of this study was to assess the relationship between the morphology of dental arches and the activity of the masticatory muscles activities in healthy volunteers with full natural dentition. METHODS: Two-hundred youthful Class I volunteers (113 females, 87 males) were clinically investigated. Alginate impressions of dental arches were taken, and plaster casts were prepared and measured. EMG data from eight masticatory muscles was recorded to assess their activities in central occlusion, lateral and protrusive movements. RESULTS: Clinical measurements and plaster casts analyses confirmed normal values of parameters investigated. Most of the arch measurements were significantly larger in the males than in the females. Weak positive correlations were found between overbite and masseter activity in centric occlusion (the right Mm R = 0.151, P ≤ 0.05; the left Mm R = 0.191, P ≤ 0.05). Also, the range of protrusive movement positively correlated with masseter activities in central occlusion (the right Mm R = 0.194, P ≤ 0.05; the left R = 0.201, P ≤ 0.05). CONCLUSIONS: The null hypothesis that morphology of dental arches does not affect the masticatory muscles' activities was rejected. The findings of this investigation indicate that systemic, longitudinal analyses of morphology of occlusion and muscular response, even in normal subjects, are needed.