The correlation between the rotation of upper first permanent molars and malocclusions in the individual dental arch and in the occlusion

Introduction Malocclusions disturb the integrity of the dental arch and the interdental/occlusal relationship. All this leads to a change in the position of the upper molars in the sagittal, transversal and vertical plane. The rotation of the upper first molar leads to a shift of position of molar cups in a mesio-distal direction demonstrated by the great impact on the distribution of occlusal forces. Aim The rotation of upper first molars should not be underestimated in the biometrical analysis of diagnostic dental casts as this can lead to incomplete and improper treatment plan. Ðœaterial s and M ethods Our study investigated 681 children aged 7-10 years who attended the Department of Orthodontics at the Faculty of Dental Medicine in Varna. All children were clinically evaluated and biometrical assessment of diagnostic dental casts was performed. Diagnostic records included also photo-analysis and measurements of diagnostic dental casts. The relationship between the rotation of upper first permanent molars and the transversal and sagittal dimension, and also the overjet were assessed. The degrees of rotation were classified using the Friel and Vigano methods. Results A regressional statistical analysis was conducted to determine the frequency of malocclusion and to establish the relationship between the rotation of upper first permanent molar and the length of the arch, the intercanine distance, and the overjet. The comparative analysis demonstrated inverse relationship not only between the rotational position of the molars and the length of the arch, but also between the canine distance and the rotation of the upper molars (p<0.01). It is reported that when an overjet up to 4 mm is present, the mediopalatal rotation of the molars is negatively affected. Conclusion Losing the length of the arch leads to compression of the dental arch, medialization of permanent molars and crowding of the frontal teeth. The problem of mesiopalatal rotation of upper first permanent molars is manifested through increased overjet and increased overbite.