A Study Of The Relationship Between Ultrasound Images Of Masicatory Muscle And Caraniofical Morphlogy Of Young Males With Nomal Occlusion

Objective: The aim of this study was to establish the average of superfacial masseter and to meter anterior temporal muscle of young males with nomal occlusion by Ultrasonography under different mandibular functional positions,and to compare their differences,and to investigate whether the Ultrasound images of masseter and temporal muscle were related to the facial morphology and the dental arch form of individiual,using to orthodontic clinical. Methods: The subjects consisted of 69 males with nomal occlusion (aged 18～28 years). Ultrasound scanning was used to measure the perimeter,area,width,mean thickness,maximal thickness and length of superfacial masseter muscle and mean thickness and maximal thickness of anterior temporal muscle,recordings were performed with the muscle both in relaxing,maximal clenching and under maximal protruding position respectively. Facial dimensions and dental arch form parameter were measured. The facial dimension ratios were calculated,and these indexes were analysis. Results:①The thickness of superfacial masseter and anterior temporal muscle were statistically significant differences between in relaxation and in maximal protruding position (P<0.05). The ultrasound parameters of images of superfacial masseter and the thickness of anterior temporalis in maximal clenching were statistically significant differences from those in the relaxing and in the maximal protruding position (P<0.05).②During both relaxation and maximal clenching,the perimeter,area,mean thickness and maximal thickness of masseter muscle showed a poisitive relation with bizygomatic facial width (BFW) and intergonial width (IGW) (P<0.05). The mean thickness and maximal thickness of anterior temporal muscle showed a poisitive relation with IGW (P<0.05). There was a poisitive relation between posterior facial height (PFH) and masseter muscle maximal thickness at maximal clenching. The perimeter,mean thickness and maximal thickness of masseter muscle in relaxation had a significantly negative relation with AFH/BFW and AFH/IGW (P<0.05). The perimeter,mean thickness and maximal thickness of masseter muscle at maximal clenching had a significantly negative relation with AFH/IGW (P<0.05).③There were significantly poisitive relationships between maxillary antero-middle dental arch length and masseter muscle area,mandibular anterior dental arch length and masseter muscle length,mandibular middle dental arch width,maxillary dental arch perimeter and masseter muscle maximal thickness in relaxation (P<0.05). There were significantly poisitive relationships between mandibular middle dental arch width and masseter muscle mean thickness at maximal clenching (P < 0.05). There were significantly negative relationships between the maxillary anterior,antero-middle dental arch length and anterior temporal muscle thickness both relaxation and maximal clenching (P<0.05). There were significantly negative relationships between the mandibular antero-middle dental arch length and anterior temporal muscle thickness at maximal clenching (P<0.05). Conclusion:①There were statistically significant differences was found in the ultrasound parameters of images of superfacial masseter and anterior temporalis under different mandibular functional positions.②Masseter and temporal muscle morphology and function could influenced the facial morphology.③The results indicate that the function capacity of masseter and temporal muscle may be considered as one of the factors which influencing the dental arch form.