The Clinical Study Of Preventive Extraction Of Impacted Mandibular Third Molar Tooth Germ

Objectives To investigate the impaction of mandibular third molar(M3M)and its correlation with the lesion of adjacent mandibular second molar(M2M);to explore the bone defect of M2 M and its influencing factors after M3M extraction;to study the clinical effect of preventive extraction of M3M germ with impaction tendency.Materials and methods(1)A total of 4328 M3Ms from 3000 orthopantomography(OPG)were retrospectively analyzed.The impaction of M3M and its correlation with the lesion of adjacent M2 M including caries,periodontal lesions and root resorption were analyzed.(2)The preoperative and postoperative cone-beam CT(CBCT)data of 25 patients with 37 impacted M3Ms were analyzed retrospectively.The changes of M2 M distal ODD before and 6 months after operation were analyzed.(3)This prospective clinical study was conducted in 11 healthy adolescent patients with21 extractions of M3M germs and 14 healthy adult patients with 21 extractions of M3M.The postoperative response,PD,ODD and so on were recorded during the follow-up period.Results(1)The classification of M3M were related to the lesion of M2M(P<0.001).The rate of M2 M distal caries was highest when M3M were mesioangular or type B.The rate of M2 M periodontal defects was highest when M3M were vertical or type B.The rate of M2 M external root resorptions was highest when M3M were inverted or type C.(2)M2M distal ODD decreased compared with that before extraction.Age,type of impaction and degree of bone defect before extraction were the factors influencing postoperative M2 M distal bone defect.(3)The operation time of M3M germ extraction was short,and there was no adverse event after the operation.6 months after the operation,PD was(2.07 ± 0.51)mm,ODD was(0.65 ± 0.31)mm,better than the control group.Conclusions(1)High-risk M3M should be removed to prevent damage to the adjacent M2 M.(2)After the removal of M3M in young patients with high risk,M2 M distal bone height recovered.When M3M can be expected to be removed,early extraction may have a beneficial impact on the periodontal health of M2 M.When M3M is impacted deeply,bone graft should be implanted at the same time in order to achieve better healing.(3)Preventive extraction of M3M germs with the tendency of impaction can avoid the potential harm of M3M and obtain excellent clinical outcome after 6 months.