Investigation of rotation, angle and tilt values of upper 1st molars according to malocclusions by digital 3D modeling method

The aim of this study is to analyze the rotation, angulation and inclination values of the upper first molars in patient models with different dental malocclusions by means of digital 3D model analysis programs and to compare these values obtained as a result of the analysis with each other. The material of our study consists of orthodontic models of 208 patients who applied to Ankara Yıldırım Beyazıt University Faculty of Dentistry, Department of Orthodontics. They were divided into 4 groups according to Angle's dental classification as Class I, Class II Div 1, Class II Div 2, Class III. The scanning of the models was made in the Dental-Wings model scanner, the measurements of them were made in the Maestro program. Each measurement was done separately for the right and left molars. The measurements were 'Henry Angle', 'Friel Angle', Ricketts Line', 'Hayce- Nance Analysis', 'Angulation' and 'Inclination'. Anova and Kruskal-Wallis H tests were used for the statistical analysis. Chi-square test for comparison of categorical variables; percentage-frequency tables were used. p<0.05 was used as the significance level. According to the Rickets analysis the upper molars in Class II patients (Div 1 and Div 2) had a higher amount of rotation in the mesiopalatinal direction than Class I patients (p= 0.014). According to the Hayce-Nance analysis, the lack of space in Class II (Div 1 and Div 2) patients was higher than Class III patients (p=0.010). There were less negative angulations in Class III patients than the other groups (p=0.001). However, in inclination, Class III patients had more positive inclinations than the other groups (p=0.000). Knowing the ideal rotation, angulation and inclination of the maxillary first molar teeth according to malocclusions can help in making the correct diagnosis and treatment planning. Thus, the orthodontist can choose a more accurate technique for treatment. As a result, it can increase the effectiveness of the treatment by shortening the sitting time of the patient.