| Background The mandibular first molar is the largest tooth in the arch,which the cusp of the occlusal surface,the ridge,the fossa,the groove,the inclined surface are the most,and the occlusal contact area is the largest.So it also plays the most important role in teeth chewing function and also in maintaining normal oral function.Mandibular first molar is one of the important conditions to establish normal occlusal.Nevertheless,the mandibular first molar eruption time is earlier.The gap between pit and fissure is deep,and the oral hygiene maintenance consciousness of school-age children is poor.Parents often ignore the mandible first permanent molar.Chinese malocclusion cases most likely choose tooth extraction treatments,but most are pulling premolar,among them there are also many cases encountered problems which mandible first molar tooth is controversial.So the mandible first molar is commonly subject to significant compromise which may arise due to caries or endodontic complications,or from developmental anomalies such as hypoplasia.Orthodontic cases involving the extraction of mandible permanent first molars are thought to be technically more difficult to treat and whether it is a good result.Many cases that would benefit from this approach because of the doubtful long-term prognosis of the molars are treated with the extraction of healthy premolars.The avoidance of mandible first molar cases may be due to a number of factors including the following: operator comfort with premolar extraction cases,lack of experience in handling molar extraction cases,and the importance of mandible first molar.But when we work in the clinical encountered in the mandibular first molar severe lesions or congenital malformations of the patients,should be conservative to adopt conventional tooth extraction model,tries to keep them by repairtreatment after the extensively carious first molars,or pulling them,or orthodontic closure of the mandible first molar extraction space by protracting the second and third molars?This is the problem that clinical orthodontic doctors often need to think about.What about the effect of extraction the mandible first molars malocclusion? Besides,choosing a right method to evaluate the outcome of the unique plan is also very important.This is the very topic I need to study in the paper.Objective The aim of this retrospective study was to assess the clinical effect of orthodontic treatment in patients with extraction of mandible first molar using PAR index and cephalometrics,which the purpose is to provide reference and help for clinical.Besides,compare the differences between mandibular first molar extraction and four premolars extraction.Methods Nineteen patients(three male and sixteen female)with extraction of mandible first molar because of caries,periapical disease as experimental group,which the average age was 21.37±5.07,from 18 to 33.The control group was 19 patients(seven male and twelve female)with extraction four first premolar,which the average age was 20.42±4.23,from 18 to 33.According to the principle of randomized double-blind control,all subjects including experimental group and control group were collected from the Department of Orthodontic,The Second Affiliated Hospital of Guang Zhou Medical University.All the patients were treated with orthodontic space closure using MBT pre-adjusted appliance and sliding mechanics and class ? or class ? elastics.76 Cephalometric films and casts that were taken before and after orthodontic treatment were measured and analysed.The PAR index including upper and lower anterior teeth displacement,upper and lower posterior teeth displacement,bilateral buccal occlusion,overjet,overbite and centerline were measured on before and after orthodontic treatment dental casts quantitatively.And Cephalometrics analysis were performed in selected 38 patients with PACS system before and after treatment.Results1.Cephalometric results before and after orthodontic treatment: All the subjects with extraction treatment had the facial aesthetic and facial balance.Most of the indexes tended to normal after treatment.The experimental group were significant changes in U1-NA(°)?U1-NA(mm)?U1-SN(°),but not in the rest of the value.The control group were significant changes in U1-NA(°)?U1-NA(mm)?U1-SN(°)?L1-NB(°)?L1-NB(mm).The two group have differences in L1-NB(°)?L1-NB(mm)after orthodontic treatment(P<0.05).2.PAR index result analysis before and after orthodontic treatment: The two groups were statistically significant changes in all PAR index.No patient had been worse or no difference,6 patients had been improved(31.58%),13 patients had been greatly improved(68.42%).The experimental group pre-treatment total weighted PAR score were 25.58±8.33,and post-treatment PAR was 0.26±0.65,achieving a reduction of 99%with treatment.The control group pre-treatment total weighted PAR score were25.68±8.33,and post-treatment PAR was 0.26±0.65,achieving a reduction of 99% with treatment.No statistical difference was found between the experimental group and control group after treatment in PAR index(P>0.05).3.Treatment time: All extraction spaces were closed.The experimental group duration of treatment ranged from 19 to 48 months,the average treatment time was(33.47±7.93)months.The control group duration of treatment ranged from 14 to 24 months,the average treatment time was(21.26±2.40)months.The experimental group and control group difference was statistically significant(P<0.05).Conclusions If the mandibular first molars have serious decay or periapical lesions,remove of mandibular first molar,make full use of the mandibular third molar,so that you can avoid the denture restoration in the mouth.It also can produce satisfactory results under strict plan,appropriate control and careful clinical operation. |
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