Study On The Correlation Between Mandibular Second Molar Growth And Dental Age And The Skeletal Age Among Children And Adolescents

In Orthodontics, the stage of growth and development of patients has an important effect on the development of treatment plans, the expectation of treatment limits and prognosis as well as determination of best treatment timing. This study observed the cervical vertebral bone age(Cervical Vertebra Bone Age, CVBA), dental age(Dental Age, DA) and the tooth body length(TL) and crown width(CW) of the mandibular second molar(mandibular second molar, Msm) of children and adolescents from Chongqing aged between 9.5-15.5 years old by cone beam CT(Cone beam CT, CBCT) and lateral head positioning. And the paper discusses relation between the tooth body length and crown width ratio(TL/CW) of mandibular second molar(Msm), dental age(DA) and cervical vertebral bone age(CVBA) using statistical analysis method, providing a basis for evaluation of the development of bones and teeth in orthodontic treatment. This study consists of two parts:(i) Study on the correlation between mandibular second molar(Msm) growth and dental age(DA) of children and adolescents;(ii) Correlation between mandibular second molars(Msm) and cervical vertebral bone age(CVBA) of children and adolescents.Purpose: To discuss the correlation between mandibular second molar(Msm) growth, dental age(DA) and cervical vertebral bone age(CVBA) of children and adolescents, providing a basis for evaluation of the development of bones and teeth in orthodontic treatment.Method: This study measures the cervical vertebral bone age(Cervical Vertebra Bone Age, CVBA), dental age(Dental Age, DA) and tooth body length(TL) and crown width(CW) of the mandibular second molar(mandibular second molar, Msm) of 114 male children and youngsters aged between 9.5-15.5 years old and 168 female children and youngsters from Chongqing aged between 9.5-15.5 years old by CBCT(Cone beam CT) and lateral head positioning. Using a simple linear correlation analysis, the study discusses the correlation between CVBA, DA and the tooth body length and crown width ratio(TL/CW) of mandibular second molar(Msm), and the relationship between the tooth body length and crown width ratio(TL/CW) of mandibular second molar(Msm), DA and CVBA as a simple linear regression analysis.Using two independent sample t-test to compare between the various indicators of the male and female, explores whether there is sexual difference.Results:1. Through the Pearson correlation analysis, the tooth body length and crown width ratio(TL/CW) of mandibular second molar was highly correlated with DA among the male group,and the correlation coefficient r was 0.795(p<0.01). The tooth body length and crown width ratio(TL/CW) of mandibular second molar was moderately correlated with DA among the female group,and the correlation coefficient r was 0.667(p<0.01). The tooth body length and crown width ratio(TL/CW) of mandibular second molar was moderately correlated with DA in all the crowd, and the correlation coefficient r was 0.686(p<0.01). Through regression analysis, we get the regression equation of y=5.929x+4.515(p<0.001) with the tooth body length and crown width ratio(TL/CW) of mandibular second molar as(x) and DA(y) for the male group; and the regression equation of y=2.775x+9.705(p<0.001) with the tooth body length and crown width ratio(TL/CW) of mandibular second molar as(x) and DA(y) for the female group; After merger of both groups, the tooth body length and crown width ratio(TL/CW) of mandibular second molar as(x) and DA(y) correlate in the equation y=3.263x+8.402(p<0.001).2. Through the Pearson correlation analysis, the tooth body length and crown width ratio(TL/CW) of mandibular second molar was highly correlated with the CVBA among the male group,and the correlation coefficient r was 0.795(p<0.01). 7he tooth body length and crown width ratio(TL/CW) of mandibular second molar was highly correlated with the CVBA among the female group,and the correlation coefficient r was 0.754(p<0.01). The tooth body length and crown width ratio(TL/CW) of mandibular second molar was highly correlated with the CVBA in all the crowd, and the correlation coefficient r was 0.732(p<0.01). Through regression analysis, we get the regression equation of y=3.045x+8.693(p<0.001) with the tooth body length and crown width ratio(TL/CW) of mandibular second as(x) and CVBA(y) for the male group; and the regression equation of y=5.275x+6.321(p<0.001) with the tooth body length and crown width ratio(TL/CW) of mandibular second molar as(x) and CVBA(y) for the female group; After merger of both groups, the tooth body length and crown width ratio(TL/CW) of mandibular second molar(x) and CVBA(y) correlate in the equation y=5.637x+5.465(p<0.001).3. In the indexes of gender comparison, in addition to comparison of age and the tooth body length and crown width ratio(TL/CW) of mandibular second molar show no statistical difference(p > 0.05), the comparison of the CVBA and the DA were statistically significant(p < 0.05), and the DA and CVBA of female than for male.Conclusion: From the results above, we see that the growth of mandibular second molar is highly correlated with CVBA and moderately correlated with DA among male and female children and adolescents. When deciding the growth of the patient in orthodontic treatment, it is recommended to use the root length of mandibular second molar for evaluation of the development of bones and teeth.