Abstract
Introduction: Orthodontic treatment in-deep bite subjects has generally been focused on the correction of excessive vertical coverage (overbite); however, the impact on functional problems following treatment has not been well evaluated. This study aimed to investigate the differences in mandibular movements between deep bite and normal occlusion, and to compare the functional changes of mandible in the subjects with deep bite before and after treatment. Methods: This study included students from School of Dentistry, China Medical University (CMU), and employees from CMU Hospital. The participants were categorized into normal bite (n = 11) and deep bite (n = 16) groups. Considering the clinical practicability, convenience and affordability, Digi Gnatho software (Japan), was used to analyze mandibular movements recorded by digital video camera. Results: No significant difference was observed in the left side masticatory movements between two groups. Significant difference was only detected in the horizontal direction of right side mastication. All of the velocities and masticatory cycle duration of both sides showed no difference. In the mandibular border movements, protrusive movements in deep-bite group were distinct from normal occlusion group. Normal occlusion group had a larger range of mandibular movements compared to deep bite group. Conclusions: Different degrees of vertical coverage of the incisors not only presented differences in the ranges of masticatory movements and border movements, but also had an impact on the final occlusal phase of mastication.
Highlights
Orthodontic treatment in-deep bite subjects has generally been focused on the correction of excessive vertical coverage; the impact on functional problems following treatment has not been well evaluated
[25] Based on their results, we found that the subjects with deep bite might have exerted an effort to avoid steeper angles of incisors and a larger overbite, which resulted in a narrower range of mandibular movements during mastication, a slower mouth closing velocity, and a longer average duration of masticatory cycle
We found that the subjects showing either right side or left site mastication accounted for 6% in the deep bite group, 9% of subjects with normal occlusion presented right side mastication, and 18% subjects were left side
Summary
Orthodontic treatment in-deep bite subjects has generally been focused on the correction of excessive vertical coverage (overbite); the impact on functional problems following treatment has not been well evaluated. This study aimed to investigate the differences in mandibular movements between deep bite and normal occlusion, and to compare the functional changes of mandible in the subjects with deep bite before and after treatment. Normal occlusion group had a larger range of mandibular movements compared to deep bite group. Jankelson et al in 1975[1] suggested that the functions of chewing system can be evaluated by mandibular movement trajectories, such as changes in mandibular displacement and velocity observed during chewing. This method has been widely used for analyzing the masticatory system function by many scientists . The other studies suggested that deep bite was not significantly associated with condylar position [7], or caused TMJ disorders [8]
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