A Retrospective Study Of Periodontal Tissue Destruction Of Adjacent Teeth By Impacted Mandibular Third Molars And Periodontal Tissue Recovery After Extraction

Objective Impacted mandibular third molars(MTM)occur when the normal growth and development of MTM is hindered by the surrounding soft or hard tissues.Especially when there is mesial or horizontal impaction,it will not only increase the risk of pericoronitis of wisdom teeth,but also cause the defect of distal alveolar bone of mandibular second molar(MSM),and bring adverse effects on the healthy growth of periodontal tissue.In the clinical treatment process,the partial eruption of MTM and the destruction of periodontal tissue in the distal part of MSM caused by infection are the initial causes of loosening and shedding of MSM.In this study,cone beam CT(CBCT)was used for image acquisition,and then DCTViewer software was used to measure and analyze the influence of MTM on MSM and its distal alveolar bone in different periods,as well as the shape of MSM distal alveolar bone defect,so as to provide sufficient reference for the clinical removal of MTM and create favorable conditions for the realization of MSM prognosis.Methods According to the CBCT data of 400 patients in Hangzhou Dental Hospital from May 2018 to may 2019,they were divided into three groups:18-25 years old,25-35 years old and 35-50 years old.CBCT software KaVo eXam Vision was used to measure the distance between mesial and distal alveolar bone crest to root apex,and to analyze the effect of age on the distal alveolar bone of MSM.Results 1.After MTM removal,the risk of distal bone defect of adjacent MSM is higher in 35-50 years old patients.2.In 18-25 years old patients,the height of distal alveolar bone of MSM recovered best after removal of MTM.3.The risk of distal bone defect in MSM increases with age due to the presence of mesial or horizontal impacted MTM.4.In the presence of MTM,the distal alveolar bone defects of MSM were mainly concave and buccal defects;When MTM was absent,the types of distal buccal bone defects increased gradually in MSM,and the types of distal horizontal bone defects increased with age.Conclusion 1.Mesial or horizontal impacted MTM has great influence on the periodontium of MSM.2.It is suggested that the mesial or horizontal impacted MTM should be removed as early as possible before the age of 25,as far as possible in the tooth germ stage or young permanent teeth before root formation.3.It is suggested that the distal buccal bone plate of MSM should be preserved as much aspossible during the removal of MTM.4.CBCT can accurately analyze the impact of impacted MTM on the distal alveolar bone of MSM,which is worthy of clinical promotion.