The relationship between maxillary and mandibular central incisor inclination and assessment of supporting bone thickness-A cross sectional cone beam computed tomography study

Objectives: This study was conducted to evaluate the age and sex related changes in inclination angle, age and sex prediction on the basis of inclination angle (Linear Regression Analysis- derived mathematical equations). This study is also aimed to evaluate supporting bone thickness of maxillary central incisor/mandibular central incisors and relationship of maxillary central incisor with inclination angle and to investigate the impact of age and gender on the alveolar bone thickness. The present study also assesses the difference between supporting bone thickness of maxillary central incisor and mandibular central incisor and its relationship with inclination angle. Material and Methods: Total 101 patients having 61 male and 40 females who met the inclusion criteria were included in study. The total maxillary (101) and mandibular incisors (101) were included in the study. The cone beam images(Sagittal sections) were obtained from Carestream 9000cc (USA) CBCT machine having FOV 17x13' with Kvp 90, mA 4,voxel size.30 with 11.30 seconds exposure. The sagittal section of roots were made to evaluate the supporting bone at the labial, lingual and palatal aspects and at three different levels, cervical, middle, apical. The angle between the axis of the maxillary right central incisor and palatal plane was determined. The palatal plane was determined by the anterior nasal spine (ANS) and the posterior nasal spine. In order to measure the bone thicknesses in the most central slice of incisor in sagittal section, the long axis of right maxillary incisor and right mandibular incisor (the reference plane) was determined by drawing a line extending from the middle of the incisal edge to the end of the apical root passing by the middle of the root canal. From this sagittal section, three points were defined on the reference plane in the cervical (2 mm from the cemento-enamel junction), middle and apical regions of the root. Then three perpendiculars were drawn from the previous points on the reference plane in order to calculate the bone thickness at these levels. Results: The mean of inclination angle is approximately same in males and females and this correlation is statistically not significant(P value>0.05). The inclination angle in age groups are statistically nonsignificant (P value>0.05). The supporting alveolar bone thickness in maxillary labial and palatal except maxillary palatal in middle of root is statistically non-significant(P>.05). The alveolar bone thickness in mandibular labial and mandibular lingual side is also statistically non-significant(P>.05). The mathematical equation derived from linear regression analysis can be used for age prediction. Conclusion: This study highlights the importance of inclination angle in determination of age of an individual which can be helpful in resolving many medicolegal and criminal cases. However the supporting alveolar bone thickness helps in deciding the amount of orthodontic force to be applied for correction of skeletal malocclusion.