Introduction:

the mental symphysis is the medial cartilaginous joint of the mandibular bones, its position is related with the different biotypes and can influence the position of the lower incisor.

Objective:

to determine if there are variations in the position of the lower incisor, in class II patients with different biotypes.

Materials and methods:

all the tomography of skeletal class I and II patients who attended a private clinic between 2014 and 2020 were evaluated, having a total sample of 74 participants, characterizing the patients by sex and age. Facial biotype, Incisor Mandibular Plane Angle, distances to the symphysis such as the ACV-ACL and height from the apex were determined. For the analysis, I-CAT Vision Q was used for the measurements of the digital tomography and for the statistical analysis Stata 17.

Results:

a greater Incisor Mandibular Plane Angle in class II patients in the three biotypes was evident; class II dolichofacials showed a lower value in both cortical ACV-ACL, with the narrowest and longest measurement of the symphysis, the patients showed proclination in class II for both sexes, being higher for the male. The position of the incisor within the symphysis in class II patients presents a significant proclination in brachyfacial patients (p=0.04), despite presenting greater proclination, it maintains its apices centered within the symphysis.

Conclusion:

variations were found between the three facial biotypes in class I and II patients, it is relevant when performing orthodontic treatment since it can limit the movement of the lower incisors.

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