Research On The Guidance Of Retrospective Analysis Of The Developmental Condition Of Young Permanent Molar On Orthodontic Treatment

Objective The panoramic radiograph can provide the integrated information on the lower teeth; it is more superior in the observation of the growth and development of teeth.Digital panoramic radiographs appeared in recent years, the molar adorable situation can be showed more accurately with it. To analyze the imaging manifestations of second molar(M2)and third molar(M3)in aged 11-14 in Changzhou City, and to explore the relationship of development between M3 and M2.Methods A total of 345 adolescents with 11~14 years old, of Changzhou stomatological hospital in January-October 2013 were selected as the imaging database, male 150 cases,female 195 cases. The sample inclusion criteria were: age for 11-14 year olds;the image was clear, no obvious distortion of the mandible; no M3 extraction of history; the non congenital missing teeth and dentin dysplasia influence the development of tooth disease; without doing orthodontic treatment; the single maxillary dental arch crowding was less than 2mm, no too large or small teeth, no ectopic teeth sinking, no supernumerary teeth etc. The M3 and M2 on the panoramic radiographs was observed and the development degree in 345. And then the correlation analysis was done, to analyze the correlation between the M3 and M2, a preliminary prediction and analysis the impaction of the third molar extraction and possible; the situations of caries and resistance of the first and two molar.Results In the all adolescents, 43.26% of M2 was in stage G. The development of M2appeared earlier in the mandibular than in the maxillary(Z=-11.69, P<0.001) and earlier in female than in male(Z=-3.06, P=0.002,); There was significant difference( c 2=425.427, P<0.001) in the developmental stage of different age.21 teeth were impacted and tilted in the mandibular, it was 3.83% of the total number of mandibular M2 adorable.33.26% of M3 was in stage C. The development of M3 appeared earlier in female than male(Z=-2.06, P=0.040,);and earlier in the mandibular than in the maxillary(Z=-3.42, P = 0.001); There was significant difference(c2=501.301,P <0.001)in the developmental stage of different age. M3 and M2 to calculate Spearman correlation coefficient was 0.869, P<0.001, the difference was statistically significant.The mesial impacted mandibular M2 angle(Am2-m1) was bigger than adorable group,there was significant difference(P<0.05); Am2-m1 of female was less than the male in the adorable group, it was significant difference(P<0.05).Conclusion In the adolescents with 11~14 years old, the developmental stages of M2 was mostly in stage G, which was beneficial to carry out the best orthodontic treatment period. It was need to pay attention to the changes of mandible M2 tooth inclination in this stage and prevent mesioangular impaction; existing tendency need timely intervention. The development of M2 and M3 appeared earlier in female than in male.M2 and M3 growth trend was consistent, they was closely related to the development with the Spearman correlation analysis, this could provide a reference for the analysis of the early segment of dental arch after constant conditions, so it was necessary to consider fully the relationship between the two in orthodontic treatment.