Comparison of maxillary first molar rotation in hyper and hypo divergent patients
Introduction: The diagnosis and treatment in orthodontics is effected by the position and occlusion of the first molars in a majority of cases. This study compared the prevalence and degree of Upper 1st Molar rotation in non-treated skeletal class I patients with hypo and hyper-divergent profile.
Material and methods: Cephalometric radiographs and maxillary casts of 80 skeletal class I patients with all permanent dentition and with no dental anomaly were selected. These eighty casts were evaluated in two groups; hyper-divergent and hypo-divergent pattern, determined on basis of cephalometric angle (SN-MP), was measured on the cephalometric tracings of the radiographs. Molar rotation was measured manually on cast, using Ricketts line.
Results: There was a significant positive relationship between SN/MP and degree of molar rotation (r=.45, P>.01), The result of independent sample t test revealed that there is a significant difference between the occurrence of right side molar rotation and left side molar rotation (F=2.90, P>.005). The mean and standard deviation of right side of molar rotation was 2.39 and 0.93 respectively which is greater than left side of molar rotation 1.81 and 0.78 respectively with a significance of 0.005. It was found that mesiopalatal rotation of U1st Molar was of 85% whereas distopalatal rotation occurred in only 15% of the total sample. The one sample t test was applied which revealed that the mean difference (MD=1.150) was significant with a mean difference (F=28.62, p> .01).
Conclusions: Mesiopalatal rotation of 1st M is more common than distopalatal rotation. Molar rotation is more often found on right side of upper arch than on left side. With an increase in SN-MP angle there was increase of molar rotation in skeletal class I patients.