On the Interaction between Incisor Crown-Root Morphology and Third-Order Angulation

Abstract

OBJECTIVE: To evaluate the significance of crown-root angles (CRAs) by testing the null hypothesis that there are no significant differences in deviations of third-order angles to axial inclination values between Angle Class II division 2 incisors and a neutral occlusion control sample. MATERIALS AND METHODS: The study group comprised n(total) = 130 whites with either Angle Class II division 2 (n(1) = 62; group A) or neutral (n(2) = 68; control group B) occlusal relationships. Upper central incisor inclination (U1) was assessed with reference to the cephalometric lines NA and palatal plane (U1NA/deg, U1PP/deg). Craniofacial sagittal and vertical relations were classified using angles SNA, SNB, ANB, and NSL-PP. Third-order angles were derived from corresponding dental cast pairs using an incisor inclination gauge. Welch's two-sample t-tests (alpha-level: .05) were used to test the null hypothesis. Single linear regression was applied to determine third-order angle values as a function of axial inclination values (U1NA, U1PP) or sagittal craniofacial structures (ANB angle), separately for group A and B. RESULTS: The discrepancy between axial inclination (U1NA, U1PP) and third-order angles is significantly different (P < .001) between groups A and B. Regression analysis revealed a simply moderate correlation between third-order measurements and axial inclinations or sagittal craniofacial structures. CONCLUSION: The hypothesis is rejected. The results of this study warn against the use of identical third-order angles irrespective of diminished CRAs typical for Angle Class II division 2 subjects. Routine CRA assessment may be considered in orthodontic treatment planning of Angle Class II division 2 cases. -order measurements and axial inclinations or sagittal craniofacial structures. On the Interaction between Incisor Crown-Root Conclusion:The results of this study warn against the use of identical 3 rd -order angles irrespective of diminished crown-root angles typical for Angle Class II division 2 subjects. Routine CRA assessment may be considered in orthodontic treatment planning of Angle Class II division 2 cases.

Effects of labial and lingual retraction and intrusion force on maxillary central incisor with varying collum angles: A three-dimensional finite elemental analysis

“…Smaller crown root angle models showed more of intrusion, supported by Knösel et al study. [13] conclusIon From the present study, we conclude that as the collum angle increased, the stress-strain distribution increased in LaO and LiO. The center of rotation shifted cervically, and the intrusion decreased when collum angle increased.…”

Comparison of Collum Angle of Maxillary Central Incisor in High Angle and Low Angle Patients

“…Some authors suggest that differences in the morphology should be given more importance because of the difference among various types of pre-adjusted brackets systems. 16 Maxillary central incisor resorption is influenced by changes in the treatment and mechanics. Kaley and Phillips 25 in 1991 reported that root translation or torqueing into the palatal cortex significantly increases the chances of root resorption.…”

“…The second and third morphological feature of anterior teeth has been focused in the following studies. 7,9,16 Before CBCT (Cone beam computed tomography) was invented lateral cephalometry was the only way to investigate labial surface angle and collum. 4,17,18 CA of maxillary central incisor in sagittal malocclusion has been studied previously in western population 19,10,20,3,6 as well in Pakistani population 7,24 but vertical skeletal malocclusion using lateral cephalogram has not been studied, which was the reason we chose to explore this aspect.…”

Fatigue resistance and failure mode of novel-design anterior single-tooth implant restorations: influence of material selection for type III veneers bonded to zirconia abutments

“…In addition, any crown–root angle (CRA) can be simulated. There is a wide variation in the CRA of natural teeth themselves (Bryant et al 1984; Van Loenen et al 2005; Knösel et al 2009). A type III veneer bonded to a custom abutment would allow the replacement of teeth with extreme CRA even when placing the implant in the original root position.…”