Sam-Sun Lee

Ameloblastic carcinoma: an analysis of 6 cases with review of the literature.

OBJECTIVES The purpose of this study is to report 6 cases of ameloblastic carcinoma and to analyze all published cases regarding demographic features, clinical behavior, treatment, and prognosis. STUDY DESIGN We reviewed our 6 cases of ameloblastic carcinoma and 98 cases previously reported in the English literature. Available follow-up data from 59 cases was analyzed. RESULTS In the analysis of our cases, the average age of 6 patients was 61 years and there was a predilection for the maxilla and male. Five cases arose de novo, whereas 1 case was secondary type of ameloblastic carcinoma. Microscopically, our cases showed malignant cytologic features with some histologic features of ameloblastoma. Malignant cytologic features included nuclear pleomorphism, hyperchromatism, and high mitotic activity (33.3%). Necrosis and vascular invasion were also seen in 4 cases and 1 case, respectively. Immunostaining for cytokeratins 5, 14, and 18 was all positive and labeling index of Ki-67 was 13.91%. Two patients (33.3%) had a metastatic lesion in the regional lymph nodes without distant metastasis. In the analysis of the literature, the mean age was 49.2 years with a wide age range (7-91 years). The rate of occurrence was higher in males, and the most common site of occurrence was the mandible. The male-to-female ratio was 1.97:1 and the mandible-to-maxilla ratio was 1.71:1. Most cases (70%) involved the posterior portion of the jaw. The most common symptom was swelling, followed by pain, ulceration, paresthesia, and trismus. The recurrence rate in patients treated with surgical resection was 28.3%, whereas the rate in cases of conservative therapy was 92.3%. There was a significant correlation between treatment modality and recurrence (P = 0.000). Metastatic lesions were detected in 22% of patients during follow-up, and the lung was the most common area of distant metastasis. The 5- and 10-year survival rates were 72.9% and 56.8%, respectively. There was a significant decrease in the 5-year survival rate in patients with metastasis (21.4%; P = 0.0000). CONCLUSION Metastasis from an ameloblastic carcinoma is significantly correlated with poor prognosis. Therefore, diagnosis at an early stage and close periodic screening for metastasis are necessary to improve patient prognosis.

Use of advanced imaging modalities for the differential diagnosis of pathoses mimicking temporomandibular disorders

The medical records of 3 patients who visited our hospital with preauricular pain and limited jaw movement were retrospectively reviewed. All were clinically evaluated, diagnosed through the use of conventional radiographs, and initially treated as having temporomandibular disorders (TMD). However, their symptoms did not improve and even increased or facial swelling occurred, so advanced imaging modalities were used to make a differential diagnosis. The final diagnoses of the patients were cellulitis, an inflammatory pseudotumor, and pigmented villonodular synovitis. In addition to these 3 patients, 50 others who were initially misdiagnosed during a clinical examination as having TMD on conventional radiographs were reviewed in the English-language literature. When diagnosing patients with TMD symptoms, we must consider the possibility of unusual causes, including tumors and infections or inflammations. Furthermore, in addition to usual TMD treatment procedures, an advanced radiologic examination should be performed to aid in the differential diagnosis of all patients with unceasing pain and mouth-opening limitation.

Evaluation of accuracy of 3D reconstruction images using multi-detector CT and cone-beam CT

Purpose This study was performed to determine the accuracy of linear measurements on three-dimensional (3D) images using multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). Materials and Methods MDCT and CBCT were performed using 24 dry skulls. Twenty-one measurements were taken on the dry skulls using digital caliper. Both types of CT data were imported into OnDemand software and identification of landmarks on the 3D surface rendering images and calculation of linear measurements were performed. Reproducibility of the measurements was assessed using repeated measures ANOVA and ICC, and the measurements were statistically compared using a Student t-test. Results All assessments under the direct measurement and image-based measurements on the 3D CT surface rendering images using MDCT and CBCT showed no statistically difference under the ICC examination. The measurements showed no differences between the direct measurements of dry skull and the image-based measurements on the 3D CT surface rendering images (P>.05). Conclusion Three-dimensional reconstructed surface rendering images using MDCT and CBCT would be appropriate for 3D measurements.

Comparison of effective dose for imaging of mandible between multi-detector CT and cone-beam CT

Purpose The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Materials and Methods Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. Results The effective dose was the highest for Somatom Sensation 10 (425.84 µSv), followed by AZ3000CT (332.4 µSv), Somatom Emotion 6 (199.38 µSv), and 3D eXaM (111.6 µSv); it was the lowest for Implagraphy (83.09 µSv). The CBCT showed significant variation in dose level with different device. Conclusion The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

Comparison of trabecular bone anisotropies based on fractal dimensions and mean intercept length determined by principal axes of inertia

The mechanical quality of trabecular bone depends on both its stiffness and its strength characteristics, which can be predicted indirectly by the combination of bone volume fraction and architectural anisotropy. To analyze the directional anisotropy of the trabecular bone, we applied the fractal geometry technique to plain radiographs. The anisotropy of the bone was quantified from an ellipse, based on the directional fractal dimensions (FD), by the principal axes of inertia. The anisotropies based on the FD were compared with those determined using the common method of mean intercept length (MIL). The directional FD gave the fractal information obtained from a projection along the MIL orientation. For this reason, the spatial variations associated with the bone length in any direction were manifested in a related frequency band of the power spectrum determined along the direction. The directional FD and MIL plots were highly correlated, although they originated from quite different geometries. Of the angle, premolar, and incisor regions of the human mandible, the anisotropies calculated using both FD and MIL showed the highest correlation in the trabecular bone of the angle region. The method using directional FDs as determined by the principal axis of inertia measures the anisotropy directly, using two-dimensional plain radiographs. This kind of method will be a useful to provide better estimates of bone quality in vivo compared with the density measurements alone, especially for the indirect diagnosis of jawbone quality in dental clinics.

Correlation between 3-dimensional facial morphology and mandibular movement during maximum mouth opening and closing

PURPOSE The purpose of this study was to analyze the relationship between mandibular movement and facial morphology parameters measured using 3-dimensional CT data. MATERIALS AND METHODS We have developed a mandibular movement tracking and simulation system. The mandibular movement data were acquired from 22 subjects (6 males and 16 females), 3 who had no clinical facial deformities and 19 who had orthofacial deformities. The subjects voluntarily performed maximum mouth opening and closing movements. Three-dimensional maximum linear movements of selected points (bilateral condylions, infradentale, and pogonion) were calculated to represent mandibular movement. Facial morphology values were measured 3-dimensionally from CT data and bilateral morphological values were divided into 2 groups according to the mandibular deviation, the deviated side, and counter-deviated side groups. Correlation coefficients were calculated to evaluate the relationship between mandibular movements and facial morphology. RESULTS Maximum linear movements of all selected points on the mandible were positively correlated with sella-nasion-point A (SNA) and sella-nasion-point B (SNB). Movements of the infradentale and pogonion were significantly correlated with ramus inclination, lateral mandibular body angle, ramus length, and mandibular body length. Condylar movement was positively correlated with lateral mandibular body angle and mandibular body length. Multiple stepwise linear regression analysis was performed to evaluate the model predicting the effect of morphological values on mandibular movement. Condylar movement was associated with the SNA (R(2) value = 0.32 for the deviated side, R(2) value = 0.26 for the counter-deviated side), and movement of the infradentale was associated with both SNA and ramus length (R(2) value = 0.57). Movement of the pogonion could be predicted by SNA, mandibular length, and condylar head length (R(2) value = 0.65). CONCLUSION The 3D facial morphology values were associated with variations in mandibular movement, and morphological parameters contributed to predicting the movement of the mandible with different degrees.

The relationship between three-dimensional principal rotations and mandibular deviation

OBJECTIVE To investigate the rotational variations of three-dimensional (3D) trajectories at anatomic landmarks by different mandibular kinematics, we applied principal axes of inertia to the 3D trajectories. The principal rotations were determined directly from the anatomy-based trajectories produced by a patient-specific temporomandibular joint simulation. As a preliminary study, the principal rotations for a pilot group of patients with mandibular deviation were correlated with the deviation. STUDY DESIGN Three-dimensional mandibular movements from the patients with mandibular deviation were tracked based on a patient-specific splint and an optical tracking system. The dental occlusion recorded on the splint provided synchronization for initial movement in the tracking and the simulation phases. The translation and rotation recorded during tracking were applied sequentially to the mandibular model in relation to a fixed maxilla model. The sequential positions of the points of interest based on the reference coordinate system could also be simulated and traced by the same method. The landmarks selected for analysis were the points of the bilateral condyles and of the mandibular incisor. The moment of inertia tensor was calculated with respect to the 3D trajectory points. Using the unit vectors along the principal axes derived from the tensor matrix, α, β, and γ rotations (horizontal, sagittal, and frontal planes) around the z-, y-, and x-axes, respectively, were determined to represent the principal directions as principal rotations. RESULTS The measured rotations were correlated with the deviation in 3 orthogonal planes. Under the influence of the mandibular asymmetry, the orientations of the principal axis at the condyles increase counterclockwise in the horizontal plane and clockwise in the frontal plane. At the incisor point, the horizontal and frontal angles increase counterclockwise, but the sagittal angles increase clockwise. The interrelations between different rotations and between landmarks, defined as a correlation coefficient between principal rotations, decrease as the deviation increases. CONCLUSIONS Three-dimensional trajectories at selected landmarks based on the reference coordinate system were evaluated using principal axes of inertia to investigate the functional characteristics of the mandible with a deviation. The movement asymmetry between the condyles increases as the deviation increases in all directions. The principal rotations at the condyles can be explained by those at the incisor with varying degrees despite the deviation.

Predicting the configuration of a C-shaped canal system from panoramic radiographs

OBJECTIVE To characterize the presentation of C-shaped canals in mandibular molars on dental panoramic radiographs. STUDY DESIGN The sample consisted of 290 patients who had undergone both panoramic dental radiography and computed tomography (CT). Initially the presence of mandibular molars with C-shaped canals was identified on this sample by the use CT. This was used as a ground radiographic truth. Then 3 investigators independently classified the mandibular molars according to their 6 root morphologies on panoramic dental radiographs. The sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) of characteristic findings on panoramic radiographs were calculated. RESULTS A C-shaped canal was identified in 90 (29%) of 311 mandibular molars. The most common morphology of C-shaped canal molars was 2 separate conical roots (52%); trabecular patterns were relatively common between the roots. In contrast, the most common morphology of molars without C-shaped canals was 2 separate roots that were either divergent or parallel (85%). CONCLUSION Panoramic radiography is a good surveying modality to detect C-shaped canals and can be used to determine whether further examination is required before endodontic treatment.

Texture analysis of mandibular cortical bone on digital dental panoramic radiographs for the diagnosis of osteoporosis in Korean women

OBJECTIVE To determine whether individual measurements or a combination of textural features and mandibular cortical width (MCW) derived from digital dental panoramic radiographs (DPRs) are more useful in assessment of osteoporosis. STUDY DESIGN Textural features were obtained by using fractal dimension (FD) and gray-level co-occurrence matrix (GLCM). Digital DPRs and bone mineral densities (BMDs) of the lumbar spine and the femoral neck were obtained from 141 female patients. A naïve Bayes classifier, a k-nearest neighbor (k-NN) algorithm, and a support vector machine were assessed for classifying osteoporosis. RESULTS The combinations of FD plus MCW (95.3%, 92.1%, 96.8%) and GLCM plus MCW (93.7%, 89.5%, 94.2%) for femoral neck BMD showed the highest diagnostic accuracy with the use of the naïve Bayes, k-NN, and support vector machine classifiers, respectively. CONCLUSIONS The combination of textural features and MCW contributed a better assessment of osteoporosis compared with the use of only individual measurements.

The relationship between the changes in three-dimensional facial morphology and mandibular movement after orthognathic surgery

PURPOSE The purpose of this study was to investigate the relationship between changes in three-dimensional (3D) facial morphology and mandibular movement after orthognathic surgery. We hypothesized that facial morphology changes after orthognathic surgery exert effects on 3D mandibular movement. MATERIALS AND METHODS We conducted a prospective follow-up study of patients who had undergone orthognathic surgical procedures. Three-dimensional facial morphological values were measured from facial CT images before and three months after orthognathic surgery. Three-dimensional maximum mandibular opening (MMO) values of four points (bilateral condylions, infradentale, and pogonion) were also measured using a mandibular movement tracking and simulation system. The predictor variables were changes in morphological parameters divided into two groups (deviated side (DS) or contralateral side (CS) groups), and the outcome variables were changes in the MMO at four points. RESULTS We evaluated 21 subjects who had undergone orthognathic surgical procedures. Alterations in the TFH (total facial height), LFH (lower facial height), CS MBL (mandibular body length), and DS RL (ramus length) were negatively correlated with changes in bilateral condylar movement. The UFH, DS MBL and CS ML (mandibular length) showed correlations with infradentale movement. The CS ML, DS ML, MBL, UFH, and SNB were correlated with pogonion movement. CONCLUSION The height of the face is most likely to affect post-operative mandibular movement, and is negatively correlated with movement changes in the condyles, infradentale and pogonion. The changes in CS morphological parameters are more correlated with mandibular movement changes than the DS. The changes in CS MBL and bilateral RL were negatively correlated with condylar movement changes, while the bilateral MBL and CS ML were positively correlated with changes in infradentale and pogonion.