Abstract:Objective: To discuss possible relationships between class III malocclusion and perioral forces by measuring the pressure from the lips and the tongue of children with class III malocclusion. Methods: Thirty-one children with class III malocclusion were investigated and their perioral forces were measured at rest and during swallowing under natural head position by a custom-made miniperioral force computer measuring system. Results: The resting pressures exerted on the labial side and palatine side of the upper left incisor, as well as the labial side and lingual side of the lower left incisor, were 0 g/cm 2 , 0 g/cm 2 , 0.57 g/cm 2 and 0.23 g/cm 2 , respectively. Correspondingly, the swallowing forces were 2.87 g/cm 2 , 5.97 g/cm 2 , 4.09 g/cm 2 and 7.89 g/cm 2 , respectively. No statistical difference between muscular pressure and gender existed. During swallowing, the lingual forces were significantly higher than the labial forces (P<0.01), however, at rest there was no significantly different force between these two sides. Compared to the normal occlusion patients, children with class III malocclusion had lower perioral forces. The upper labial resting forces (P<0.01), the lower labial resting forces (P<0.05) and all the swallowing pressures from the lips and the tongue (P<0.01) showed statistical differences between the two different occlusion conditions. Meanwhile, no significant difference was found for the resting pressure from the tongue between class III malocclusion and normal occlusion. Conclusion: Patients with class III malocclusion have lower perioral forces and this muscle hypofunction may be secondary to the spatial relations of the jaws. The findings support the spatial matrix hypothesis.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

No abstract

The etiology of class III malocclusion remains unknown. The present study investigates the relationship between craniofacial morphology and premaxillary suture fusion to test the hypothesis that class III malocclusion may be related to premaxillary suture fusion. Cyanoacrylate was applied to immobilize the left premaxillary suture in the experimental group. Sham surgeries in rats were used for controls. Dental impressions and radiographs were taken before and after surgery for comparison of craniofacial differences between groups. Overall cranial base lengths, craniofacial widths, and craniofacial angulations related to the anterior base showed significant differences between groups. At the end of the experiment, the growth of the snout in the experimental group was inhibited and deviated to the treated side, while no obvious change was seen in the control group. The results show that induced premaxillary suture fusion can affect craniofacial morphology and indicate that premature premaxillary suture fusion may result in class III malocclusion.