Measurement accuracy with a new dental panoramic radiographic technique based on tomosynthesis
a Professor and Chair, Department of Orthodontics, School of Dentistry, Asahi University, Gifu, Japan. The Angle Orthodontist
(Impact Factor: 1.23).
05/2012; 83(1). DOI: 10.2319/020412-100.1
Abstract Objective: To investigate measurement errors and head positioning effects on radiographs made with new dental panoramic radiograph equipment that uses tomosynthesis. Materials and Methods: Radiographic images of a simulated human head or phantom were made at standard head positions using the new dental panoramic radiograph equipment. Measurement errors were evaluated by comparing with the true values. The phantom was also radiographed at various alternative head positions. Significant differences between measurement values at standard and alternative head positions were evaluated. Magnification ratios of the dimensions at standard and alternative head positions were calculated. Results: The measurement errors were small for all dimensions. On the measurements at 4-mm displacement positions, no dimension was significantly different from the standard value, and all dimensions were within ±5% of the standard values. At 12-mm displacement positions, the magnification ratios for tooth length and mandibular ramus height were within ±5% of the standard values, but those for dental arch width, mandibular width, and mandibular body length were beyond ±5% of the standard values. Conclusions: Measurement errors on radiographs made using the new panoramic radiograph equipment were small in any direction. At 4-mm head displacement positions, no head positioning effect on the measurements was found. At 12-mm head displacement positions, the measurements for vertical dimensions were little affected by head positioning, while those for lateral and anteroposterior dimensions were strongly affected.
Available from: Mauro Cozzani
- "There are in the literature a few quantitative measurement studies, which evaluate tooth length  and mesiodistal root angulation : dimensions in the vertical direction may entail a variable amount of magnification that can be as high as 17–27% in the maxillary premolar and 1st molar region with the palatal root having the worst vertical magnification. This is why panoramic radiographs have been of limited use for quantitative studies, preferring 3D imaging or newer technologies  instead. Lahreim  also measured tooth lengths from panoramic radiographs and showed that measurement error varies from 0.43 to 0.56 mm, indicating that the main source of error was the recognition of reference points. "
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. To build a 3D parametric model to detect shape and volume of dental roots, from a panoramic radiograph (PAN) of the patient.
Materials and Methods
. A PAN and a cone beam computed tomography (CBCT) of a patient were acquired. For each tooth, various parameters were considered (coronal and root lengths and widths): these were measured from the CBCT and from the PAN. Measures were compared to evaluate the accuracy level of PAN measurements. By using a CAD software, parametric models of an incisor and of a molar were constructed employing B-spline curves and free-form surfaces. PAN measures of teeth 2.1 and 3.6 were assigned to the parametric models; the same two teeth were segmented from CBCT. The two models were superimposed to assess the accuracy of the parametric model.
. PAN measures resulted to be accurate and comparable with all other measurements. From model superimposition the maximum error resulted was 1.1 mm on the incisor crown and 2 mm on the molar furcation.
. This study shows that it is possible to build a 3D parametric model starting from 2D information with a clinically valid accuracy level. This can ultimately lead to a crown-root movement simulation.
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ABSTRACT: Panoramic radiographs are commonly used in dental practice. The challenge with panoramic radiography is overlapping structures, ghost and air shadows. The area of interest can appear blurred especially in the anterior region. The focal block is a virtual space in which the dentition should be perfectly placed when acquiring the radiograph. Anatomical structures that are within this focal block appear focused and in perfect geometric accuracy on the final image. Structures outside this focal block appear blurred, and distorted. Accurate positioning of the patient will help in placing the region of interest within in the focal block and as a result minimising artefacts, ghost and air shadows. We utilise cone beam computed tomography (CBCT) software to explain this principle.
Available from: Koray HALICIOĞLU
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ABSTRACT: The aims of this study were to evaluate condylar and ramal mandibular vertical asymmetry in a patient group affected by unilateral (UCLP) and bilateral (BCLP) cleft lip and palate, and to compare the findings with a well-matched control group with normal occlusion.
The study groups included 20 UCLP patients (12 male, 8 female), 21 BCLP patients (12 male, 9 female), and a control group of 21 subjects with normal occlusion (10 male, 11 female). Measurements of condylar, ramal, and condylar plus ramal heights and asymmetry indexes were examined on cone-beam computed tomography images. One-way analysis of variance was used to determine potential statistical differences among the groups for condylar, ramal, and condylar plus ramal asymmetry index measurements. The post-hoc Tukey HSD test was used to determine individual differences.
No investigated group showed a statistically significant sex difference for any asymmetry index (P >0.05). There was a statistically significant difference between the normal and cleft sides in the ramal height and ramal plus condylar height measurements in the UCLP group (P = 0.004 and P = 0.006, respectively). The Tukey HSD test showed a statistically significant difference between the UCLP and BCLP groups in terms of ramal asymmetry index values (P = 0.018).
The ramal height and ramal plus condylar height measurements were significantly lower in the cleft side in the UCLP patients, and there was a statistically significant difference in ramal asymmetry index values between the patients affected by UCLP and BCLP.
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