Clinical Study On The Effect Of PAOO On Periodontal Tissue And Root Of Lower Anterior Teeth In Adult Patients With Bimaxillary Protrusion

Objective:To utilize PAOO to assist anterior teeth retraction process in adult patients with bimaxillary protrusion,and to explore the changes of periodontal tissue and root length in lower anterior teeth.Materials and methods:Twenty adult patients(13 females,7 males;18-31 years old,mean age 23.7±2.6 years)with bony class I bimaxillary protrusion were enrolled.There were 10 patients in the experimental group and 10 in the control group.All patients receieved four first premolars extraction and retract the incisors under the maximum anchorage.Gingival recession and keratinized gingiva width of mandibular canines,lateral incisors and middle incisors were measured after alignment(TO)and 3 months after space closure(T1).The cone-beam CT was used to measure the alveolar bone area of the labial side of the sagittal plane,the height of alveolar bone of labial and lingual sides,the thickness of the alveolar bone at 3 mm,6 mm,9 mm below the CEJ of labial side,and the length of the root.SPSS(Version 19.0,SPSS,Chicago,USA)software was used for data analysis.Paired T test were used to compare the differences between the two time points to analyze the changes before and after treatment.Independent sample T test was used to compare the differences between groups to analyze the effect of PAOO.The 1-way analysis of variance with the Tukey' s test was used for the comparison between the central incisors,lateral incisors,and canines in the experimental group to analyze the effect of PAOO on different types of anterior teeth.Results:1.The keretinized gingiva width:In the experimental group and the control group,the keratinized gingiva width of the lower anterior tooth increased significantly(P<0.05).The increase of the gingival width in the experimental group was significantly greater than the control group(P<0.001).2.The root length and gingival recession:There was no significant difference in root length and gingival recession between the experimental group and the control group.3.The bone area of the labial side:In the experimental group,the alveolar bone area of the labial side of the sagittal plane of the canines,lateral incisors and middle incisors were significantly increased(P<0.01);while in the control group,the alveolar bone area of the lateral incisors and the middle incisors were significantly decreased(P<0.001).The changes of the lateral incisors and the middle incisors were statistically significant(P<0.001).4.The thickness of alveolar bone:In the experimental group,the thickness of alveolar bone at 6mm and 9mm below the CEJ of labial side increased significantly in the canines,lateral incisors and middle incisors(P<0.01);in the control group,the thickness of alveolar bone at 9mm below the CEJ of labial side was significantly decreased in 3 kinds of anterior teeth(P<0.05).The changes of alveolar bone thickness at 6 mm and 9 mm were statistically significant in 3 kinds of anterior teeth(P<0.01).5.The height of alveolar bone:In the experimental group,the height of labial alveolar bone of canines,lateral incisor and middle incisor were significantly increased(P<0.01),while that of the control group were significantly decreased in 3 kinds of anterior teeth(P<0.01).There was a significant difference between groups changes,including canines,lateral incisors and middle incisors(P<0.01).In the experimental group and the control group,the height of the lingual alveolar bone of the canines,the lateral incisors and the middle incisors were both significantly decreased(P<0.01),and the changes in the experimental group were significantly lower than those in the control group(P<0.001).6.The thickness of alveolar bone in lateral incisors was significantly increased in 3 kinds of anterior teeth,especially at 6mm and 9mm below the CEJ of labial side(P<0.05).Conclusion:In the process of retraction of anterior teeth in adult patients with bimaxillary protrusion,PAOO increased the width of the keratinized gingiva,and did not increase the risk of root resorption and gingival recession.The alveolar bone mass in the anterior region was increased,and PAOO may be more conducive to the preservation of vertical alveolar bone height.The effect of PAOO on different types of anterior teeth was different.