| Objective: The aim of this study is to measure dental arch width,three dimensional tilted of molars,the labial inclination of incisors and occlusal plane in skeletal Class Ⅲ malocclusions assessed with CBCT and Invivo Dental 5.1,and to provide reference for presurgical orthodontics.Methods: 57 skeletal Class Ⅲ malocclusion patients were selected for this research.Cone-beam computed tomography scans of all samples were taken by the same radiologist and saved in DICOM format,and measurement analysis were taken by Invivo Dental 5.1.The coordinate system was set up with the origin of Ba.Adjust the head position in the Section interface to establish the coordinate system.The median sagittal plane is composed of Ba,N and ANS.The horizontal plane is over Ba and is parallel to the plane of the Palatal plane.The coronal plane is over Ba and is perpendicular to the plane of the sagittal plane and horizonal plane.The cranial face is divided into two parts according to the median sagittal plane after setting up the coordinate system.The lateral side of mental point is defined as the deflected side,the other side is non-deflected side.In Section interface,we use Distance Measurement to measure the width of dental arch.In the Arch Section interface,we use Angle Measurement to measure the lip dip Angle of incisors.In the Arch Section interface,adjust the direction of the dental section through the Create Arch Spline,we use Angle Measurement to measure the Angle of the buccolingual and mesiodistal inclination of molars.20 normal occlusion individuals as the control group were taken the same measurement.The same experimentor performs the experiment.The interval is two weeks.We use SPSS 22.0 software to analyze the experimental measurement results.The relevance of the two measurement results was verified by the interclass correlation coefficient.In the experimental group,the Paired-Samples T Test was performed on the deflected and non-deflected side,and analyzed the differences on both sides.The left and right side’s differences were detected by Paired-Samples T Test.Independent-Sample T Test was performed in the experimental group and the control group.Results: 1.Incisor: The lip tilt of the of upper incisors is larger than the control group,the upper central incisors tilts to the lip.The lip tilt of the mandibular incisors of the normal occlusion is larger than skeletal Class Ⅲ malocclusion,the lower incisors tilt to the tongue.2.Mesioincisodistal inclination: The normal occlusion of the upper molars are distally inclined and the second molar is more distally inclined than the first molar.The mandibular molars are mesially inclined.The second molar is more mesial tilting than the first molar.The deflected upper molars in skeletal Class Ⅲ malocclusion are more significantly mesial inclination than the matched group.The deflected lower first molar and the control group in mesiodistal direction have no statistical difference.The deflected lower second molar was more erect than the control group in mesiodistal direction.Non-deflected upper molars in skeletal Class Ⅲ malocclusion are more upright or mesial inclination than that of the control group.Non-deflected lower molars are more upright than that of the control group.Except for the upper second molar in skeletal Class Ⅲ malocclusion,deflected molars are more mesial inclination than non-deflected molars.3.Buccal lingual inclination: in the control group,the upper molars are buccal inclination,the lower molars are lingual inclination.Relative to the normal occlusion group,deflected upper molars in skeletal Class Ⅲ malocclusion are more apparently buccal inclination,deflected lower molars are more obviously lingual inclination.Relative to the normal occlusion group,the upper first molar of the non-deflected is lingual inclination,the non-deflected upper second molar is buccal inclination,there is no statistical significance in the non-deflected lower molars.The deflected upper molars are more significantly buccal inclination than the nondeflected upper molars.The deflected lower molars are significantly lingual inclination than the non-deflected lower molars.4.Dental arch width: the width of the upper and lower canine teeth in skeletal Class Ⅲ malocclusions have no statistical significance.The arch width of upper second premolar and second molar was wider than that of the control group.the upper first molar and the control group have no statistical significance.Except for the width of the mandibular intercannie,the mandibular arch is wider than that of the matched group.5.The occlusal plane: the occlusal plane of the deflected upper molars is lower than the non-deflected side,and the Angle of the upper posterior molars are smaller than the control group,and there is no statistical difference between the lower posterior molars and the control group.Conclusion: 1.Relative to the normal occlusion group,the upper incisors in skeletal Class Ⅲ malocclusion tilt to the lip,.the lower central incisors in skeletal Class Ⅲ malocclusion are lingual inclination.2.Relative to the normal occlusion group,the deflected upper molars in skeletal Class Ⅲ malocclusion are more significantly mesial,and there is no statistical difference in mesiodistal inclination between the deflected lower first molar and the control group.3.Buccal lingual inclination: the deflected upper molars in skeletal Class Ⅲ malocclusion are more apparently buccal inclination,and the deflected lower molars are more obviously lingual inclination.The upper first molar of the non-deflected is lingual inclination,the non-deflected upper second molar is buccal inclination,there is no statistical significance in the non-deflected lower molars.4.Dental arch width:the lower dental arch width in skeletal Class Ⅲ is larger than the individual normal occlusion.The upper dental arch width in skeletal Class Ⅲ malocclusion and the control group have no statistical difference.5.The occlusal plane: the occlusal plane of the deflected upper molars is lower than the non-deflected side,and the Angle of the upper posterior molars are smaller than the control group. |
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