Yun-Hoa Jung

Cone-beam computerized tomography evaluation of condylar changes and stability following two-jaw surgery: Le Fort I osteotomy and mandibular setback surgery with rigid fixation

OBJECTIVES The purpose of this study was to compare the changes of the condylar axis, the anteroposterior condylar position relative to the glenoid fossa, and post-2-jaw surgery stability. STUDY DESIGN All of the patients (12 male, 14 female) were assessed by cone-beam computerized tomography (CBCT) before surgery, after surgery, and at follow-up. CBCT images were referenced to assess skeletal stability, the condylar axis change, and the anteroposterior condylar position in the glenoid fossa. A repeated-measures analysis of variance (P = .05) also was performed. RESULTS The skeletal changes between postsurgery and follow-up (P < .05) were insignificant. Both the axial condylar angles and the anteroposterior condylar position significantly differed among the groups (P < .05). CONCLUSIONS After surgery, the coronal condylar axis was rotated inward. The anteroposterior condylar position in the glenoid fossa had moved from the anterior to the concentric position, tending to return slightly toward the original position. These changes did not negatively affect the stability.

Effect of Bimaxillary Surgery on Adaptive Condylar Head Remodeling: Metric Analysis and Image Interpretation Using Cone-Beam Computed Tomography Volume Superimposition

PURPOSE The aim of the present study was to use cone-beam computed tomography volume superimposition to investigate the effect of bimaxillary orthognathic surgery on condylar head remodeling. MATERIALS AND METHODS Using a retrospective study design, 2 investigators evaluated the cone-beam computed tomography data of subjects who had undergone Le Fort I osteotomy and mandibular setback surgery. The predictor variable was time, grouped as preoperative versus postoperative. The outcome variables were the measurement changes of the condylar heads and the distribution of the condylar head remodeling signs. Paired t and χ(2) tests were performed for the purposes of the 2-dimensional metric analysis and the condylar head remodeling distribution. P < .05 was considered significant. RESULTS The sample was composed of 22 adults (11 men and 11 women, age 20.3 ± 3.2 years) diagnosed with skeletal Class III malocclusion. The intra- and interoperator reliabilities of the image interpretation showed substantial agreement, according to Cohens kappa index. The condylar heights on the sagittal and coronal planes decreased after surgery. Bone resorption occurred predominantly in the anterior and superior areas on the sagittal plane, the superior and lateral areas on the coronal plane, and the anterolateral and posterolateral areas on the axial plane (P < .05). Bone formation was apparent only in the anteromedial area on the axial plane (P < .05). CONCLUSIONS Bimaxillary orthognathic surgery caused a decrease in the condylar heights and condylar head remodeling. The cone-beam computed tomography volume superimposition method showed that the condylar head had undergone remodeling after bimaxillary surgery.

Assessment of the relationship between the maxillary molars and adjacent structures using cone beam computed tomography

Purpose This study investigated the relationship between the roots of the maxillary molars and the maxillary sinus using cone beam computed tomography (CBCT), and measured the distances between the roots of the maxillary molars and the sinus floor as well as the thickness of the bone between the root and the alveolar cortical plate. Materials and Methods The study sample consisted of 83 patients with normally erupted bilateral maxillary first and second molars. A total of 332 maxillary molars were examined using CBCT images. The vertical relationship of each root with the maxillary sinus was classified into four types on CBCT cross-sectional images. The distance between the sinus floor and root and the bone thickness between the root and alveolar cortical plate were measured. Results In the buccal roots of the maxillary molars, a root protruding into the sinus occurred most frequently. A root projecting laterally along the sinus cavity was most common in the palatal roots of the maxillary first molars. The mesiobuccal roots of the maxillary second molar were closest to the sinus. The mesiobuccal roots of the first molars were closest to the cortical plate. Conclusion The relationship between the roots of the maxillary molars and the sinus differed between the buccal and palatal roots. A root protruding into the sinus occurred more frequent in the buccal roots of the maxillary molars. The mesiobuccal root of the maxillary second molar was closest to the maxillary sinus floor and farthest from the alveolar cortical plate.

External root resorption after orthodontic treatment: a study of contributing factors

Purpose The purpose of this study was to examine the patient- and treatment-related etiologic factors of external root resorption. Materials and Methods This study consisted of 163 patients who had completed orthodontic treatments and taken the pre- and post-treatment panoramic and lateral cephalometric radiographs. The length of tooth was measured from the tooth apex to the incisal edge or cusp tip on the panoramic radiograph. Overbite and overjet were measured from the pre- and post-treatment lateral cephalometric radiographs. The root resorption of each tooth and the factors of malocclusion were analyzed with an analysis of variance. A paired t test was performed to compare the mean amount of root resorption between male and female, between extraction and non-extraction cases, and between surgery and non-surgery groups. Correlation coefficients were measured to assess the relationship between the amount of root resorption and the age in which the orthodontic treatment started, the degree of changes in overbite and overjet, and the duration of treatment. Results Maxillary central incisor was the most resorbed tooth, followed by the maxillary lateral incisor, the mandibular central incisor, and the mandibular lateral incisor. The history of tooth extraction was significantly associated with the root resorption. The duration of orthodontic treatment was positively correlated with the amount of root resorption. Conclusion These findings show that orthodontic treatment should be carefully performed in patients who need the treatment for a long period and with a pre-treatment extraction of teeth.

Correlation of panoramic radiographs and cone beam computed tomography in the assessment of a superimposed relationship between the mandibular canal and impacted third molars

Purpose This study evaluated the association between cone beam computed tomography (CBCT) and panoramic radiographs in the assessment of a superimposed relationship between the mandibular canal and impacted third molars. Materials and Methods The study samples consisted of 175 impacted third molars from 131 patients who showed a superimposed relationship between the mandibular canal and third molars on panoramic radiographs and were referred for the examination of the mandibular canal with CBCT. Panoramic images were evaluated for the darkening of the root and the interruption of the mandibular canal wall. CBCT images were used to assess the buccolingual position of the mandibular canal relative to the third molar, the proximity of the roots to the canal, and lingual cortical bone loss. The association of the panoramic and CBCT findings was examined using a Chi-square test and Fishers exact test. Results Panoramic radiographic signs were statistically associated with CBCT findings (P<0.01). In cases of darkening roots, lingual cortical bone loss or buccally positioned canals were more frequent. In cases in which the mandibular canal wall was interrupted on panoramic radiographs, contact or lingually positioned canals were more frequent. Conclusion The results of this study suggest that contact between the mandibular third molar and canal and a lingually positioned canal could be more frequently observed in cases of the interruption of the white line of the mandibular canal and that there could be more lingual cortical loss in cases of darkening roots.

Radiographic evaluation of the course and visibility of the mandibular canal

Purpose This study was performed to investigate the course of the mandibular canal on panoramic radiography and the visibility of this canal on both panoramic radiography and cone-beam computed tomography (CBCT). Materials and Methods The study consisted of panoramic radiographs and CBCT images from 262 patients. The course of the mandibular canal, as seen in panoramic radiographs, was classified into four types: linear, elliptical, spoon-shaped, and turning curves. The visibility of this canal from the first to the third molar region was evaluated by visually determining whether the mandibular canal was clearly visible, probably visible, or invisible. The visibihlity of the canal on panoramic radiographs was compared with that on CBCT images. Results Elliptical curves were most frequently observed along the course of the mandibular canal. The percentage of clearly visible mandibular canals was the highest among the spoon-shaped curves and the lowest among the linear curves. On panoramic radiographs, invisible mandibular canals were found in 22.7% of the examined sites in the first molar region, 11.8% in the second molar region, and 1.3% in the third molar region. On CBCT cross-sectional images, the mandibular canal was invisible in 8.2% of the examined sites in the first molar region, 5.7% in the second molar region, and 0.2% in the third molar region. Conclusion The visibility of this canal was lower in the first molar region than in the third molar region. The mandibular canal presented better visibility on CBCT images than on panoramic radiographs.

Prevalence of missing and impacted third molars in adults aged 25 years and above

Purpose The purpose of this study was to determine the prevalence of missing and impacted third molars in people aged 25 years and above. Materials and Methods The study sample of 3,799 patients was chosen randomly from patients who visited Pusan National University Dental Hospital and had panoramic radiographs taken. The data collected included presence and impaction state, angulation, and depth of impaction of third molars, and radiographically detected lesions of third molars and adjacent second molars. Results A greater percentage of men than women retained at least one third molar. The incidence of third molars decreased with increasing age. The incidence of partially impacted third molars greatly declined after the age of 30. Vertically impacted maxillary third molars and horizontally impacted mandibular third molars were most frequent in all age groups. Among the maxillary third molars, those impacted below the cervical line of the second molar were most frequent in all age groups, and among the mandibular third molars, deeply impacted third molars were most frequent in those aged over 40. Dental caries was the most common radiographic lesion of the third molars. Mesioangularly impacted third molars showed radiographic lesions in 13 (9.5%) adjacent maxillary second molars and 117 (27.4%) mandibular second molars. Conclusion The number of remaining third molars decreased and the percentage of Class C depth increased with age. Caries was the most frequent lesion in third molars. Partially impacted mesioangular third molars showed a high incidence of caries or periodontal bone loss of the adjacent second molar. Regular oral examination will be essential to keep asymptomatic third molars in good health.

Radiographic evaluation of third molar development in 6- to 24-year-olds

Purpose This study investigated the developmental stages of third molars in relation to chronological age and compared third molar development according to location and gender. Materials and Methods A retrospective analysis of panoramic radiographs of 2490 patients aged between 6 and 24 years was conducted, and the developmental stages of the third molars were evaluated using the modified Demirjians classification. The mean age, standard deviation, minimal and maximal age, and percentile distributions were recorded for each stage of development. A Mann-Whitney U test was performed to test the developmental differences in the third molars between the maxillary and mandibular arches and between genders. A linear regression analysis was used for assessing the correlation between the third molar development and chronological age. Results The developmental stages of the third molars were more advanced in the maxillary arch than the mandibular arch. Males reached the developmental stages earlier than females. The average age of the initial mineralization of the third molars was 8.57 years, and the average age at apex closure was 21.96 years. The mean age of crown completion was 14.52 and 15.04 years for the maxillary and the mandibular third molars, respectively. Conclusion The developmental stages of the third molars clearly showed a strong correlation with age. The third molars developed earlier in the upper arch than the lower arch; further, they developed earlier in males than in females.

Nontraumatic bifid mandibular condyles in asymptomatic and symptomatic temporomandibular joint subjects.

Purpose This study was performed to determine the prevalence of bifid mandibular condyles (BMCs) in asymptomatic and symptomatic temporomandibular joint (TMJ) subjects with no traumatic history, and to assess their impact on clinical and radiographic manifestations of TMJ. Materials and Methods A total of 3,046 asymptomatic and 4,378 symptomatic patients were included in the study. Cone-beam computed tomography (CBCT) images were reviewed for bifid condyles. T-tests were used to compare the frequency of BMCs when stratified by symptom, gender, and side. In BMC patients, the clinical features of pain and noise, osseous changes, and parasagittal positioning of the condyles were compared between the normally shaped condyle side and the BMC side using chi-squared tests. Results Fifteen (0.49%) asymptomatic and 22 (0.50%) symptomatic patients were found to have BMCs. Among the bilateral cases, the number of condyles were 19 (0.31%) and 25 (0.29%), respectively. No statistically significant differences were found between asymptomatic and symptomatic patients, between female and male patients, or between the right and left sides (p>0.05). Compared with the normally shaped condyle side, the BMC side showed no statistically significant differences in the distribution of pain and noise, parasagittal condylar position, or condylar osseous changes, with the exception of osteophytes. In the symptomatic group, osteophytes were found more frequently on the normally shaped condyle side than the BMC side (p<0.05). Conclusion BMCs tended to be identified as an incidental finding. The presence of BMC would not lead to any TMJ symptoms or cause osseous changes.

Diagnostic reference levels in intraoral dental radiography in Korea

Purpose The objectives of this study were to survey the radiographic exposure parameters, to measure the patient doses for intraoral dental radiography nationwide, and thus to establish the diagnostic reference levels (DRLs) in intraoral dental X-ray examination in Korea. Materials and Methods One hundred two intraoral dental radiographic machines from all regions of South Korea were selected for this study. Radiographic exposure parameters, size of hospital, type of image receptor system, installation duration of machine, and type of dental X-ray machine were documented. Patient entrance doses (PED) and dose-area products (DAP) were measured three times at the end of the exit cone of the X-ray unit with a DAP meter (DIAMENTOR M4-KDK, PTW, Freiburg, Germany) for adult mandibular molar intraoral dental radiography, and corrections were made for room temperature and pressure. Measured PED and DAP were averaged and compared according to the size of hospital, type of image receptor system, installation duration, and type of dental X-ray machine. Results The mean exposure parameters were 62.6 kVp, 7.9 mA, and 0.5 second for adult mandibular molar intraoral dental radiography. The mean patient dose was 2.11 mGy (PED) and 59.4 mGycm2 (DAP) and the third quartile one 3.07 mGy (PED) and 87.4 mGycm2 (DAP). Doses at university dental hospitals were lower than those at dental clinics (p<0.05). Doses of digital radiography (DR) type were lower than those of film-based type (p<0.05). Conclusion We recommend 3.1 mGy (PED), 87.4 mGycm2 (DAP) as the DRLs in adult mandibular molar intraoral dental radiography in Korea.