The Relationship between Upper Incisors Inclination and the Supporting Bone Tissue : A CBCT Study

Abstract

The aims of the study were 1) to evaluate the supporting bone tissue thickness around 68 upper incisors and its relationship with their inclination, and 2) to investigate the impact of gender on these two variables. Thirty-four patients with no previous orthodontic treatment participated in the study. Cone beam computed tomography (CBCT) scans were taken. Sagittal sections of the roots were made to evaluate the supporting bone at the labial and the lingual aspects and at three different levels: cervical, middle and apical. Angles of the upper central incisors (U1/U2) with the palatal plane (SPP) were also measured. The palatal apical region had the greatest thickness of bone tissue followed by the palatal middle and the labial apical regions. The lowest thickness was observed on the labial surface, in the apical and in the middle of the root. The thickness of the labial apical region of both upper teeth increased significantly when the angle between the upper central incisors axis and the palatal plane increased (U1: p = 0.012/ r = 0.42 and U2: p = 0.005/ r = 0.46). The thickness of the palatal middle of the root regions for both upper central incisors were significantly higher in males than females (U1: p = 0.005/ average = 1.2 mm for males; U2: p = 0.003/ average = 1.0 mm for males). There was no significant difference in the incisors’ inclination between males and females. The bone tissue thickness in the labial apical region increased when the inclination of the upper central incisors increased. The greatest value of bone tissue amount was in the apical region, whereas the lowest value was in the labial surface in both cervical and middle of the root regions. Males had a higher value than females of bone tissue amount in the palatal middle of the root region at the upper central incisors. Resume Cette etude a pour buts d’evaluer 1) l’epaisseur de l’os alveolaire autourdes incisives superieures et la correlation entre l’epaisseur osseuse et l’inclinaison des incisives, et 2) l’influence du sexe sur l’epaisseur de l’os et l’inclinaison des incisives. Trente-quatre patients n’ayant subi aucun traitement orthodontique ont participe a l’etude. Des coupes tomodensitometriques volumetriques a faisceau conique (CBCT) ont ete realisees. Des sections sagittales ont ete faites sur les incisives superieures pour evaluer l’epaisseur osseuse des surfaces labiale et palatine au niveau de 3 regions (cervicale, centrale et apicale) de la racine. Les angles formes par les incisives (U1 /U2) avec le plan palatin ont ete encore mesures. La plus grande epaisseur d’os alveolaire a ete observee au niveau de la region palatine apicale, suivie par la region palatine centrale et la region labiale apicale. L’os alveolaire des regions labiale cervicale et centrale de la racine etaient le moins epais. La correlation entre l’inclinaison des incisives et l’epaisseur de l’os alveolaire etait proportionnelle au niveau des deux incisives droite et gauche (r1 = 0.42; p = 0.012 et r2 = 0.46; p = 0.05, respectivement). Les hommes avaient un os alveolaire plus epais que celui des femmes dans la region palatine des 2 incisives superieures droite (p=0.05) et gauche (p=0.003), respectivement. La difference d’epaisseur des deux incisives droite et gauche entre hommes et femmes etait respectivement av1=1.2mm et av2=1mm. Par contre, aucune difference n’a ete observee entre les hommes et les femmes en ce qui concerne l’inclinaison des incisives superieures.