Asymmetry of the sphenoid bone and its suitability as a reference for analyzing craniofacial asymmetry

A reference-based radiographic “reference sphere method” (RSM) for accurate length measurements in (dental) projection radiographs for the assessment of tooth length in dry human mandible sections is evaluated. RSM determines the depth coordinates of reference spheres placed in the object plane from the elliptical distortion of their shadows. Two segments (one canine and one molar) of dry human mandibles were exposed 95 times at different angulations (0–40°) on a dental charge-coupled device receptor. Three steel spheres (diameters d
 1 = 2.00 mm, d
 2 = 3.00 mm) were attached roughly coplanar with the tooth’s main axis. Radiographs were assessed once by visual inspection plus manual landmark identification with a mouse-driven cursor. The results were compared to the true tooth length assessed after extraction and to a conventional method (C), i.e., the rule of proportion based on magnification of the sphere shadows. Mean relative length error was 2.28% (d
 1) and 0.46% (d
 2) for RSM and −13.58% (d
 1) and −9.90% (d
 2) for C. For both methods, length errors were significantly (p < 0.0001) correlated with the inclination relative to the receptor. RSM allows for complete a posteriori determination of the imaging geometry under the assumption of a known source-to-receptor distance. One specific application is foreshortening correction of objects coplanar with the reference spheres. Remaining errors are mainly due to incorrect landmark definition. In our setup, these were exaggerated by the visual/manual image-evaluation process. Automated image analysis has been shown for similar tasks to minimize these errors considerably.

Ex vivo radiographic tooth length measurements with the reference sphere method (RSM)

The purpose of this research was to compare the reliability of two different methods for cranial midline localization through cephalometric analysis of mandibular condyle asymmetries. A retrospective cohort study was performed analyzing consecutively the SMV radiograms of 47 patients undergoing oral surgery before orthodontic treatment at the Dental School, University of Trieste (Italy) from 2003 to 2008. Two different cephalometric analyses were used to identify the basicranium midline (Tracing 1: initial landmarks = craniostat ear rods; Tracing 2: initial landmarks = spinosum foramina), and the left/right symmetry ratio (SR) for four parameters (condylar length, condylar angle, intra-condylar hemidistance, extra-condylar hemidistance) was calculated. The main result showed that no significant statistical difference between the SRs of the intra-condylar and extra-condylar hemidistance obtained with the same tracing was found ( 𝑡 -test; 𝑃 = N S ; C.I. 95%). Conversely, the difference between the SRs obtained with the two different tracings was statistically significant ( 𝑡 -test; 𝑃 0 . 0 0 0 ; C.I. 95%). In conclusion, if the analysis of condylar asymmetries is performed in growing subjects, utilization of anatomic references such as the neurovascular foramina seems to guarantee a lower error compared to non-fixed references such as ear rods.

/pdf/localization-of-basicranium-midline-by-submentovertex-3xt7fiad9l.pdf

Localization of basicranium midline by submentovertex projection for the evaluation of condylar asymmetry.

Aim: To three-dimensionally evaluate the facial harmony in orthodontic patients with vertical growth pattern. Materials and Methods: Cone-beam computed tomography (CT) scans were obtained in 10 normal occlusion adults (4 men, 6 women) with vertical growth pattern, and reconstructed into 3dimensional (3D) models by using a 3D image software. 3D position of 12 hard tissue landmarks, 3 midlines and 9 pairs of bilateral landmarks, were identified in 3D coordination system, and their right and left differences were calculated and analyzed. Results: The right and left difference values derived from the study indicated a degree of facial asymmetry in the vertical growers. The lateral ramal inclination was the most asymmetric value. Conclusions: A degree of facial asymmetry exists in the vertical growers. The lateral ramal inclination is a significant parameter in the assessment of facial asymmetry in the vertical growers. Facial asymmetry tends to increase according to the lower and lateral positioning of the landmarks in the face. There is a tendency towards left-side dominance.

https://scumj.journals.ekb.eg/article_47300_fe1c61699d7988ec7b98ae03da98796a.pdf

Three-dimensional Evaluation of Facial Harmony in Orthodontic Patients with Vertical Growth Pattern

Aiming to complete the three dimensional cephalometric analysis, specially on face s asymmetry, this study developed a cephalogram in basal norm, only with angular measures. A sample of thirty patients, clinically symmetrics was used, and through an angular coordinate system were evaluated bilateral cephalometrics points as Angulare, Buccale, Coronoid process, lateral condylion and gonion; besides unpaired points as Anterior Nasal Spine , superior incisors and pogonion. Statistical tests, as t-Student and Pearson s Correlation coeficient were applied and, through them, it was possible to observe differences among the averages obtained of the right and the left side of the same individual, characterizing an asymmetry and the presence of a positive correlation among bilateral structures.

Análise cefalométrica axial, com medidas angulares, na avaliação de indivíduos clinicamente simétricos

This study examined the changes seen on the submentovertex radiograph when the head is not extended sufficiently. A human dry skull supported on a cephalostat was used to simulate head extension. The range of rotation tested was an under-rotation of the skull of 30 degrees to an over-rotation of 10 degrees in intervals of 5 degrees. The measured variables were the intercondylar axis angles, corpus lengths and condylar widths. The relationships between skull rotation and changes in these variables were determined. Three selected landmarks, the spinosa points (right and left) and the pogonion point of each radiograph were located and compared spatially with the same points on the ideal radiograph. The results showed that variation in skull rotation affects both linear and angular measurements significantly (P < 0.01). Landmarks further away from the axis of rotation are affected by distortion more than those nearer to it.

Head positioning and projection errors in submentovertex radiographic analysis.

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Head positioning and projection errors in submentovertex radiographic analysis.