Image Distortion in Rotational Panoramic Radiography. : II. Vertical Distance.

Aims:The purpose of this study was to investigate the relationship between vertical asymmetries of the mandibular condyle with different occlusion types, including Angle Cl I, Cl II, Cl III malocclusions and unilateral posterior crossbite (UPC) in adolescent patients.Methodology:A total number of 120 patients (60 girls, 60 boys with a mean age of 13·64±1·58 years) with no signs and symptoms of temporomandibular disorders were included in the study [n = 30 for each group; Group I: normal occlusion, Group II: Angle Class II malocclusion, Group III: Angle Class III malocclusion and Group IV: UPC]. The asymmetry index for each patient was measured using panoramic radiographs. The results were analyzed using Kruskal–Wallis and Mann–Whitney U test at the 95% confidence level.Results:The results of the analyses showed no statistically significant differences between the gender and the age of the patients for condylar height asymmetry (P>0·05). No statistically significant difference was found between the...

Condylar asymmetry in different occlusion types.

Objectives The aim of this study was to analyze contributing factors for postoperative relapse after orthognathic surgery in patients with preoperative idiopathic condylar resorption (ICR). Study Design Sixteen female patients with mandibular retrognathism and ICR were included in this prospective study. For patient factors, serum 17 β-estradiol (E2), bone mineral density, and the preoperative posterior condylar inclination were evaluated. Bone mineral density was measured using dual-energy x-ray absorptiometry (DEXA) bone densitometry and expressed by T-score. Surgical changes and postoperative relapse were measured with cephalometric analysis. The correlation between postoperative relapse and measured parameters was statistically analyzed. Results The lowest T-score exhibited a significant correlation with postoperative clockwise rotation and posterior relapse tendency of the mandible (P Conclusions The postoperative relapse tendency in patients with preoperative ICR is significantly related to the lowest T-score and the amount of mandibular advancement.

Bone mineral density and mandibular advancement as contributing factors for postoperative relapse after orthognathic surgery in patients with preoperative idiopathic condylar resorption: a prospective study with preliminary 1-year follow-up

The widely used panoramic radiography as a special kind of tomography underlies intrinsic procedural restrictions such as poor definition, inconsistent magnification, geometric distortion and spatial depositioning of objects situated outside the focal trough. This results in a non-anatomic display of the radiographed anatomic structures. Individual mandibular angle and width of the jaws, adjustment of the focal trough, jaw incongruence as well as patient positioning increase the inconsistency in display of the radiographed objects. This study precisely evaluated the quantitative impact of object malpositioning on the display in panoramic radiography. A special dental implant model was highly accurate three dimensionally malpositioned and panoramic radiographs were taken. Automated image analysis was performed to exclude subjective assessment error. Precise and retraceable object deposition of up to 5 mm or 5° resulted in relevant deposition of objects and significant changes in object size and inter-object distances in the panoramic image. Unidirectional malpositioning lead to multiple errors in display. The extent of malpositioning-related display errors additionally to the known physicotechnical insufficiencies of the panoramic radiography demonstrates its limitations in precisely interpreting spatial relationships. Measurements within the panoramic radiography must not claim reliability. For a single object securely positioned in the focal trough and perpendicular to the central X-ray beam, measurements may be trustworthy on clinical scale. Once sterical relationships to other structures are evaluated, reliability must be questioned.

Impact of malpositioning on panoramic radiography in implant dentistry

Image Distortion in Rotational Panoramic Radiograhy. : III. Inclined Objects.

The aim of this study was to assess whether it is possible to derive accurate vertical measurements of the mandibular ramus and condyle from panoramic radiographs. A human dry skull was positioned in a panoramic machine. The skull was displaced along the sagittal and transverse plane and rotated around the vertical and transverse axes. A set of 252 digital radiographs with defined positioning errors was compared with a set of 42 radiographs in the ‘ideal’ position. The distances between the metal markers that had been attached at the angle of the mandible at a distance of 60 mm in the condyle region to produce fixed reference points on the radiographs were measured. Statistical differences were investigated using Friedman repeated measures analysis of variance on ranks followed by the Dunnett's test for the comparison against the control group in the ideal position (α = 0.05). Vertical measurements were significantly affected when the skull was rotated around the vertical ( P < 0.001) or shifted along the transverse axis ( P < 0.001). Misalignment of the head affected the vertical measurement of the mandibular ramus and condyle. However, asymmetries of more than 6 per cent are probably not due to patient positioning in the panoramic machine.

/pdf/panoramic-radiography-effects-of-head-alignment-on-the-2ihnsjujah.pdf

Panoramic radiography: effects of head alignment on the vertical dimension of the mandibular ramus and condyle region.

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Panoramic radiography: effects of head alignment on the vertical dimension of the mandibular ramus and condyle region.