Cone-beam Computed Tomography Study On Root Length And Alveolae Bone Morphology Of Maxillaryand Mandibular Anterior Trrth In Open Bite Patients

Objective: Comparing the root length and alveolar bone morphology of upper and lower anterior teeth between open bite patients and normal overbite patients by Cone-beam computed tomography(CBCT),which provided reference for clinical diagnosis and treatment in open bite patients.Methods1.106 untreated patients’ CBCT data(53 anterior open bite patients and 53 normal overbite patients)were evaluated by Dolphin software,and the midsagittal plane of the teeth was used as the measurement plane.The line connecting the midpoint of labial and lingual/ palatal enamel cementum junction(CEJ)and the apex was taken as the root length,and the root length of the maxillary and mandibular anterior teeth was measured.Independent t-test was used to compare respectively the difference of anterior root length between the open bite group and normal overbite group,mild open bite group and moderate-severe open bite group.Pearson correlation analysis was used to explore the correlation between the root length of anterior teeth and overbite,ANB angle,mandibular angle and so on.2.58 untreated patients(29 anterior open bite patients and 29 normal overbite patients,overlapping with some of the subjects of method 1)of high-angle with skeletal Class Ⅱ malocclusion were selected.Vertical bone level and the width of alveolar bone were measured in the midsagittal plane of the teeth by Dolphin software.Comparing the differences in alveolar bone morphology between the two groups,and explored the correlation between the alveolar bone morphology and overbite.Results1.The results showed that:(1)There was a statistical difference between the open bite group and the normal overbite group in the length of the upper and lower anterior teeth(P <0.05),the root lengths of the upper and lower anterior teeth in the open bite patients were shorter than those in the control group.(2)Compared with patients in the mild open bite group,the root length of mandibular central incisor was shorter in the moderate-severe open bite patients(P <0.05);(3)The results of Pearson correlation analysis showed that the root lengths of the maxillary and mandibular anterior teeth was positively correlated with the overbite,root length increased with the increase of overbite,while negatively correlated with the mandibular angle(except for maxillary central incisors).Moreover,anegative correlation was found between the root length of the upper and lower central incisors and the inclination of the upper central incisors.2.The results showed that:(1)In the vertical bone level: except for the mandibular lateral incisor,the lingual/ palatal vertical bone level of the upper and lower incisors were lower in open bite group(P <0.05);(2)In the maxillary alveolar bone thickness: the palatal alveolar bone thickness and the total alveolar bone thickness at the apex of the maxillary incisors were thinner in open bite group;In the labial side,alveolar bone thickness of4 mm and 6mm below CEJ of maxillary central incisor were thinner in open bite group,but alveolar bone thickness of 6mm below CEJ of lateral incisors was thicker in open bite group(P <0.05);(3)In the mandibular alveolar bone thickness: in open bite group,the labial alveolar bone thickness of 4 mm below CEJ in mandibular incisors were thinner than the control group.In the lingual side,the alveolar bone thickness of 4mm and6 mm below CEJ in the mandibular incisors were thinner than the control group.(4)In the correlation analysis,there was a different degree of positive correlation between the overbite and the alveolar bone thickness at different sites of different teeth.The deeper the overbite,the thicker the alveolar bone,especially the alveolar bone thickness of the palatal and apical regions on the maxillary incisor.And there was a negative correlation between the overbite and the vertical bone level of maxillary incisors and mandibular central incisors.Conclusions:(1)The root length of the maxillary and mandibular anterior teeth were shorter in open bite patients,and the root length was positively related to the overbite,while negatively related to the mandibular angle(except for the upper central incisor),and the root length of the upper and lower central incisors was negatively correlated with the inclination of the maxillary central incisors.(2)The alveolar bone thickness at multiple sites of upper and lower incisors were thinner in open bite patients,especially the palatal and apical regions of the maxillary incisors.(3)The lingual/ palatal vertical bone level was lower in open bite patients,except for mandibular lateral incisor.(4)There was a different degree of positive correlation between the overbite and the alveolar bone thickness at different sites of different teeth,while overbite negatively related to the vertical bone level of maxillary incisors and mandibular central incisors.