Objective To analyze the effects of different traction sites and directions on the maxilla and upper dentition when using clear aligners combined with protraction for the treatment of maxillary deficiency.Methods A three-dimensional(3D)finite element model including the zygomaticomaxillary complex,maxillary dentition,and clear aligners was constructed.The models were divided into Group 1(traction hook at the distal of the lateral incisor)and Group 2(traction hook at the distal of the canine).Each group was analyzed under four loading conditions with protraction angles of 0°,10°,20°,and 30° relative to the occlusal plane.A unilateral protraction force of 500 g was applied.The differences in stress distribution and displacement of the maxillary bone and dentition under different loading conditions were analyzed.Results When the protraction angle was 30°,both groups showed forward and downward displacement of the maxilla,while other angles resulted in counterclockwise rotation.Under the same protraction direction,the total displacement of the maxilla and displacements in all directions in Group 2 were greater than those in Group 1.The upper central incisors in Group 1 showed lingual displacement,which increased with the protraction angle.The maxillary dentition in Group 2 showed forward displacement,with the minimum total and sagittal displacements at a protraction angle of 30°.Stress concentration was mainly observed in the zygomaticomaxillary suture and anterior alveolar bone regions in both groups,decreasing as the protraction angle increased.Conclusions Clear aligners combined with protraction can be applied to skeletal Class Ⅲ patients with mild maxillary deficiency.When the protraction site is located at the distal of the canine with a 30° downward and forward angle to the occlusal plane,the maxilla can achieve ideal forward and downward displacement with the minimum labial movement of the upper anterior teeth.

Finite element method, as a verified numerical simulation method, has been widely applied in the biomechanical research of clear aligner treatment. The accuracy of its calculation results is closely related to the construction method of the finite element model. This paper takes the finite element modeling process of clear aligner treatment as a clue, and reviews the modeling methods of relevant research in recent years, aiming to provide reference for subsequent studies.

Finite element method, as a verified numerical simulation method, has been widely applied in the biomechanical research of clear aligner treatment. The accuracy of its calculation results is closely related to the construction method of the finite element model. This paper takes the finite element modeling process of clear aligner treatment as a clue, and reviews the modeling methods of relevant research in recent years, aiming to provide reference for subsequent studies.

Objective To analyze the effects of different traction sites and directions on the maxilla and upper dentition when using clear aligners combined with protraction for the treatment of maxillary deficiency.Methods A three-dimensional(3D)finite element model including the zygomaticomaxillary complex,maxillary dentition,and clear aligners was constructed.The models were divided into Group 1(traction hook at the distal of the lateral incisor)and Group 2(traction hook at the distal of the canine).Each group was analyzed under four loading conditions with protraction angles of 0°,10°,20°,and 30° relative to the occlusal plane.A unilateral protraction force of 500 g was applied.The differences in stress distribution and displacement of the maxillary bone and dentition under different loading conditions were analyzed.Results When the protraction angle was 30°,both groups showed forward and downward displacement of the maxilla,while other angles resulted in counterclockwise rotation.Under the same protraction direction,the total displacement of the maxilla and displacements in all directions in Group 2 were greater than those in Group 1.The upper central incisors in Group 1 showed lingual displacement,which increased with the protraction angle.The maxillary dentition in Group 2 showed forward displacement,with the minimum total and sagittal displacements at a protraction angle of 30°.Stress concentration was mainly observed in the zygomaticomaxillary suture and anterior alveolar bone regions in both groups,decreasing as the protraction angle increased.Conclusions Clear aligners combined with protraction can be applied to skeletal Class Ⅲ patients with mild maxillary deficiency.When the protraction site is located at the distal of the canine with a 30° downward and forward angle to the occlusal plane,the maxilla can achieve ideal forward and downward displacement with the minimum labial movement of the upper anterior teeth.

Objective: To investigate the effects of skeletal Class III malocclusion(SCIIIM) on speech articulation in the children with mixed dentition.Methods: 38 children aged 7.5～11.5 years old with skeletal Class Ⅲ malocclusion and mixed dentition were selected in a SCIIIM group, other 40 children at similar mean age with normal occlusion were selected in a control group.The articulations of the children were examined by phoneticians and the discorded speech sounds were analysed by computerized speech lab. Results: Misarticulation(%) of z,c,s,zh,ch and sh in SCIIIM group were 27.4,46.3,34.7,6.3,9.5 and 6.8 respectively. The voice onset time(VOT) of resonant note and resonant fricative note in SCIIIM group was nought while that in the control group was positive. Conclusion: There is articulatory misfunction in most Class III malocclusion patients with mixed dentition.