Anterior teeth root inclination prediction derived from digital models : a comparative study of plaster study casts and CBCT images

To assess the accuracy of digital models generated using commercially available software to predict anterior teeth root inclination characteristics and compare the results to relevant data obtained from CBCT images. Following sample size calculation and after application of inclusion and exclusion criteria, pre-treatment maxillary and mandibular plaster models and the corresponding CBCT scans of 31 patients attending a private orthodontic clinic were selected. The subjects were 10 males and 21 females with age range 12 to 40 years. Plaster models were scanned using the high resolution mode of an Ortho Insight 3D scanner and CBCT scans were taken using a Kodak 9500 Cone Beam 3D System machine. The teeth on the digital scans were segmented and virtual roots were predicted and constructed by the Ortho Insight 3D software. The long axes of the predicted roots and the actual roots, as segmented from the CBCT images, were computed using best-fit lines. The inter-axis angle was used to assess error in root inclination prediction by the software. Mann-Whitney and Kruskal-Wallis tests were used. Intra-examiner error was evaluated using the Bland-Altman method. The maximum disparity in angle between images derived from digital models and CBCT data was almost 40 degrees (upper left canine). The upper and lower canines produced the worst results, followed by the lower lateral incisors. The upper central incisors showed the best results, although the maximum angle of difference exceeded 20 degrees (with the median around 8 degrees). Root morphology imaging prediction is not a primary function of this software and this study confirmed its limitation as a sole tool in routine clinical applications. At present these predictions cannot be considered accurate or reliable unless correlated clinically with a radiographic image

Volumes faciaux et typologie verticale : étude comparative tridimensionnelle

Introduction : Le but de cette étude est de comparer les volumes des cavités faciales entre les typologies hyperdivergente et hypodivergente dans une population adulte jeune. Méthodes : Les échantillons étaient formés de 30 sujets chacun, âgés de 18 à 30 ans, sélectionnés selon leur typologie verticale (GoGn-SN ≤ 28° et ≥ 36°). À partir d’acquisitions scanners 3D et à l’aide du logiciel AMIRA®, les mesures volumétriques des cavités orbitaires, ethmoïdo-nasale et buccale ont été effectuées à partir de points servant à les délimiter, alors que les deux sinus maxillaires ont été directement segmentés coupe par coupe, puis reconstruits et leurs volumes calculés. Le test Kolmogorov-Smirnov a été utilisé pour démontrer la normalité des variables, suivi du test « t » de Student pour la comparaison des moyennes (p < 0,05). Résultats : La comparaison des volumes des différentes cavités entre les deux groupes hypodivergent et hyperdivergent n’a montré aucune différence significative au niveau des valeurs absolues ; seul le rapport du volume de la cavité nasale/volume total s’est avéré plus petit chez les hypodivergents. Conclusion : Un phénomène de compensation pourrait survenir entre les trois directions de croissance pour équilibrer un déficit ou un excès de la dimension verticale, ce qui maintiendrait constant le volume des cavités faciales étudiées

The inflection point: a torque reference for lingual bracket positioning on the palatal surface curvature of the maxillary central incisor

Abstract Background Contrary to buccal orthodontics, lingual orthodontics has no reference for vertical bracket positioning on the maxillary central incisor. The aim of this study was to provide a reference point in relation to torque for lingual bracket positioning on the palatal surface curvature (PSC) of the maxillary central incisor. Methods Cone beam computed tomography (CBCT) radiographs of 50 right maxillary central incisors from archives of a dental radiographic center were transferred to Photoshop, where their PSC was traced using pen-tool. The PSC torque angle values of the incisors were calculated in Excel using cubic poly-Bezier curves at 0.5-mm increments and at the inflection point of PSC. Descriptive statistics for the torque angle values of the increments and for the inflection point for the 50 incisors were then calculated. One-way ANOVA test was used to detect systematic differences between the increments, and Tukey test was used post-hoc. Results For all incisors, increments incisal to inflection point exhibited progressive decrease in torque angle values from the first-calculated increment to inflection point while increments cervical to inflection point exhibited progressive increase from inflection point to last-calculated increment. Mean torque angle values of all the increments and inflection point showed high standard deviations and vast range of values. One-way ANOVA test was highly statistically significant (p < 0.0001) and most pairwise comparisons of the increments using Tukey test were significant. Conclusions Inflection point can be used as a reference for bracket positioning on PSC. Cervically oriented shifts in vertical bracket position cause crown labial/root palatal movement cervical to inflection point and crown palatal/root labial movement incisal to it. A scientific mathematical justification for customized bracket torque prescriptions on PSC of maxillary central incisor was also provided

Dimorphisme sexuel et cavités faciales : étude volumétrique en imagerie 3D

Introduction : L’objectif de ce travail est d’étudier le dimorphisme sexuel au niveau des volumes des cavités faciales dans une population adulte jeune. Méthodes : L’échantillon sélectionné comporte 60 sujets, âgés entre 18 et 30 ans, ayant bénéficié d’un examen scanner de la tête. Ils sont divisés en deux groupes identiques selon le sexe. Les cavités orbitaires, ethmoïdo-nasale et buccale sont délimitées par des points sur les acquisitions scanner 3D et leurs volumes mesurés à l’aide du logiciel AMIRA®, alors que les deux sinus maxillaires sont segmentés et leurs volumes calculés. Le test Kolmogorov-Smirnov est utilisé pour démontrer la normalité des variables, suivi du test « t » de Student pour la comparaison des moyennes (p < 0,05). Résultats : Les moyennes des volumes des cavités orbitaires, ethmoïdo-nasales, buccales et des sinus maxillaires sont plus grandes chez les hommes, alors que le dimorphisme sexuel n’a pas été mis en évidence au niveau du rapport des volumes de chacune des cavités sur le volume facial total. Conclusion : Les volumes absolus des cavités faciales étudiées sont plus grands chez les hommes, mais pas les volumes relatifs, ce qui pourrait s’expliquer par l’existence d’une différence cranio-faciale de taille, et non de forme, entre les hommes et les femmes

Multinational study on profile preference of laypersons

BACKGROUND: This study aimed to assess the facial profile preferences of lay people in seven locations from different countries and whether their place of residence, sex, age, race, education, or income influenced the decision. METHODS: After altering the lip and nose in 1 mm increments in the sagittal and sagittal/vertical directions, 50 profile silhouettes with white-like facial features were rated by evaluators. The soft tissue values were integrated into the profiles, and profile preferences were identified for each location. An ANOVA with post hoc Tukey test was used to compare the differences in mean preference in each location. A multivariable regression model was used to assess the effect of the demographics of the evaluator on preference. RESULTS: Thirteen profiles were ultimately analyzed. The mean for profile preference was significantly different across locations (P < 0.0001). For evaluators in the United States and Lebanon, the most preferred profile had the original lip and original nose. In Switzerland and South Africa, retrusive lips, and a small and less upturned nose was most preferred. In Japan and Saudi Arabia, the most preferred profile had the original lip and a protrusive nose that was less upturned. A protrusive lip with a small, upturned nose was preferred in Turkey. Profile change (P < 0.0001), location (P < 0.0001), sex (P < 0.0001), and race (P = 0.02) were significant confounders; in contrast, age, education, and income were not significant. CONCLUSIONS: Profile preference is different among the seven locations. For the most part, lay people prefer profiles within one SD from white norms. Also, an upturned nose is the least favored in most of the locations. Sex and race are also significant confounders. CLINICAL RELEVANCE: An orthodontic treatment plan decision is affected by an individual's preference for their facial appearance. This study helps clinicians understand how racial and regional differences may affect patients' preferences and, therefore, their expectations for orthodontic treatment results