| Backgrounds:With the development and progress of Orthodontics,especially in the recent ten years,implant anchorage has been widely used.So that more mild to moderate skeletal malocclusion can achieve satisfied results through orthodontic treatment.In order to give the patient a good profile,orthodontists try their best to control the sagittal and vertical directions.Most of the researches on incisor retraction after extraction are mainly alveolar absorption.Therefore,it is important to analyze the initial state of alveolar bone and the relationship between root and bone.In order to explore the differences between different divergent patterns in alveolar bone thickness,height and the length of teeth before and after orthodontic treatment in adult AngleⅡ~1 patients,to provide references on treatment design and the choice of orthodontic methods.Part Ⅰ Assessment of alveolar thickness among adult AngleⅡ~1 patients with different divergent patterns before and after orthodontic treatmentObjective:To digitalize the CBCT data of AngleⅡ~1 patients with different divergent patterns before and after orthodontic treatment,investigate the changes of the thickness to explore whether there are differences in alveolar bone thickness before orthodontic treatment in adult AngleⅡ~1 patients with different divergent patterns;Wish to provide references for clinicists’s definition of proper diagnosis and project for the suitable patients before treatment,monitoring and evaluation of the therapeutic effect during and after treatment.Materials and Methods:60 adult AngleⅡ~1 patients(19-34 years)were selected,in the Affiliated Stomatological Hospital of Nanchang University during 2016-2019,who were treated with four first premolars extracted.They were divided into 3 groups:20 in the low-angle group(12 male,8 female),20 in the high-angle group(5 male and 15female),and 20 in the average-angle group(10 male and 10 female).The CBCT data before and after the treatment of all the subjects were imported into Dolphin imaging11.95,then corrected the head position and selected measurement planes.The measurement was as follows:The buccal-lingual thickness of the alveolar bone of the left and right upper and lower central incisors,canines and first molars at the location3mm,6mm,9mm from the Cemento Enamel Junction(CEJ)and at the apex;The data obtained were analyzed statistically.Results:1.In terms of the the results of cephalometric analysis,no significant difference was found between the traditional lateral cephlometrics and the one reconstructed from CBCT(P>0.05).2.Measurement of alveolar bone thickness:(1)We compared the thickness of the upper right and left central incisors,found there was difference(2)Coparison of three groups before treatment:1)The total and palatal thickness were significantly different,the same to the palatal bone thickness at the 1/3 apical region;2)The labial bone thickness in the low-angle group were significantly greater than that of the others;3)we could find the thickest regions of the bone were 6mm and 9mm in the low-angle group;4)At the level of 6 mm,the lingual thickness in the high-angle group was larger than the low-angle group,as for the labial thickness at 9 mm,it was opposite;5)The bone thickness of the mesial and distal buccal roots in the low-angle group were greater than that in the high-angle group;6)The buccal bone thickness of the mesial and distal roots in the low-angle group was greater than that in the high-angle group,while the results were reversed on the lingual side.(3)Comparison of three groups after treatment:1)The reduction of the total and labial bone thickness in the high-angle group,was significantly greater than in the low-angle group,at the level 6mm from CEJ and the apical region;2)The total bone thickness in the low-angle group did not change significantly,while decreased significantly on the lingual side,and a slight increase occurred on the labial side;In the high-angle group,the total and lingual bone thickness decreased significantly,likewise at 3mm from the CEJ in the labial side.Relatively,the reduction of total and labial bone thickness in the high-angle group was significantly greater than that in the low-angle and average-angle groups;3)the total and palatal bone thickness in the high-angle group decreased significantly at 6 mm from the CEJ;4)The total bone thickness in the high-angle group decreased significantly than that in the low-angle group;5)The buccal bone thickness of the mesial buccal roots in both the two groups decreased significantly,but no significant difference was found between the two groups;6)Apart from the apical region,the bone thickness at the maximum cross section of the mesial and distal roots both decreased in the two groups,and the reduction in the high angle group was greater than that in the low angle group.Conclusion:1.CBCT reconstructed lateral radiograph can use as hard tissue cephalometric analysis,combined with the auxiliary measurement software,improve the accuracy of pointing and measurement efficiency2.The alveolar bone thickness of the teeth of high-angle patients is thin,extraction may cause more reduction.Remind us to choose extraction carefully for high angle patients.when extraction is needed,we should pay attention to the condition of buccal alveolar bone,keep following up and preparing for soft and hard tissue increments.Part Ⅱ Assessment of alveolar height among adult AngleⅡ~1 patients with different divergent patterns before and after orthodontic treatmentment.Objective:To digitalize the CBCT data of AngleⅡ~1 patients with different divergent patterns before and after orthodontic treatment,investigate the changes of the height of alveolar bone to explore whether there are differences in alveolar bone height before orthodontic treatment in adult AngleⅡ~1 patients with different divergent patterns;Wish to provide references for clinicists’s definition of proper diagnosis and project for the suitable patients before treatment,monitoring and evaluation of the therapeutic effect during and after treatment.Materials and Methods60 adult AngleⅡ~1 patients(19-34 years)were selected,in the Affiliated Stomatological Hospital of Nanchang University during 2016-2019,who were treated with four first premolars extracted.They were divided into 3 groups:20 in the low-angle group(12 male,8 female),20 in the high-angle group(5 male and 15female),and 20 in the average-angle group(10 male and 10 female).The CBCT data before and after the treatment of all the subjects were imported into Dolphin imaging11.95,then corrected the head position and selected measurement planes.The measurement was as follows:(1)The buccal-lingual distance from alveolar crest to the CEJ;(2)The maxillary teeth:Distance from buccal-lingual alveolar crest to the palate plane;The mandibular teeth:Distance from the buccal-lingual alveolar crest to the mandibular plane;The data obtained were analyzed statistically.Results:1.There was no difference between the attached alveolar height and the alveolar height before treatment.2.The attached alveolar height of maxillary central incisor,canine palatal side,buccal side of maxillary first molar,the alveolar height on the lingual side of the mandibular canine,as well as upper and lower incisors in the high-angle group were greater significantly than that in the lower group.3.After treatment,the attached alveolar height increased in all three groups,especially on the lingual sides of maxillary canines and mandibular first molars in the low-angle group,in addition to the buccal sides of maxillary first molars’distal roots.However,The alveolar height was decreased,mainly manifested in the lingual sides on the lingual side of the mandibular canines in the high-angle group,as well as the labial sides of lower canine and maxillary first molars’mesial roots in the low-angle group.Conclusion:The alveolar crest of all teeth decreased after extraction treatment,that is alveolar absorption.Apply individual vertical control of the molar area for different divergent patterns.Part Ⅲ Assessment of teeth length among adult AngleⅡ~1 patients with different divergent patterns after orthodontic treatmentObjective:To digitalize the CBCT data of AngleⅡ~1 patients with different divergent patterns before and after orthodontic treatment,investigate the changes the length of the tooth and incisor saggital movement to explore whether there are differences in alveolar bone height before orthodontic treatment in adult AngleⅡ~1 patients with different divergent patterns;Wish to provide references for treatment design,monitoring and evaluation of the therapeutic effect during and after treatment.Materials and Methods:60 adult AngleⅡ~1 patients(19-34 years old)were selected,in the Affiliated Stomatological Hospital of Nanchang University during 2016-2019,who were treated with four first premolars extracted.They were divided into 3 groups:20 in the low-angle group(12 male,8 female),20 in the high-angle group(5 male and 15female),and 20 in the average-angle group(10 male and 10 female).The CBCT data before and after the treatment of all the subjects were imported into Dolphin imaging11.95,then corrected the head position and selected measurement planes.The measurement was as follows:The length of the tooth before and after treatment and the adduction of the upper and lower incisors.The data obtained were analyzed statistically.Results:There was no difference in the length of the corresponding teeth on the left and right sides before treatment.After treatment,the root length of the three groups was reduced(p<0.01),and the high-angle group reduced mostly.The retraction of the upper and lower incisors’incisal edge and the apex were the same in the two groups,(p>0.05).The retraction of the left maxillary central incisor’apex was positively correlated with the decrease in root length,and the correlations were 0.663,0.618,0.635(p<0.01).Conclusion:There are teeth roots resorption in different degrees after extraction treatment in different divergent patterns. |
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