Kee-Deog Kim

Computed tomographic analysis of tooth-bearing alveolar bone for orthodontic miniscrew placement

INTRODUCTION When monocortical orthodontic miniscrews are placed in interdental alveolar bone, the safe position of the miniscrew tip should be ensured. This study was designed to quantify the periradicular space in the tooth-bearing area to provide practical guidelines for miniscrew placement. METHODS Computerized tomographs of 30 maxillae and mandibles were taken from nonorthodontic adults with normal occlusion. Both mesiodistal interradicular distance and bone thickness over the narrowest interradicular space (safety depth) were measured at 2, 4, 6, and 8 mm from the cementoenamel junction. RESULTS Mesiodistal space greater than 3 mm was available at the 8-mm level in the maxillary anterior region, between the premolars, and between the second premolar and the first molar at 4 mm. In the mandible, sufficient mesiodistal space was found between the premolars, between the molars, and between the second premolar and the first molar at the 4-mm level. Safety depth greater than 4 mm was found in the maxillary and mandibular intermolar regions, and between the second premolar and the first molar in both arches. CONCLUSIONS Subapical placement is advocated in the anterior segment. Premolar areas appear reliable in both arches. Angulated placement in the intermolar area is suggested to use the sufficient safety depth in this area.

Computed Tomography as a Diagnostic Aid for Extracanal Invasive Resorption

A case of multiple extracanal invasive resorption is reported. The patient had a history of hypothyroidism for approximately 1 yr before the dental visit. Utilization of computed tomography and a rapid prototyping tooth model in diagnosing the exact location and the size of the resorption area are discussed.

Mesiobuccal root canal anatomy of Korean maxillary first and second molars by cone-beam computed tomography

OBJECTIVE The aim of this study was to investigate the types of canal configurations and the incidence of a second mesiobuccal (MB2) canal in Korean maxillary molar mesiobuccal (MB) roots by analyzing cone-beam computed tomographic (CBCT) images. STUDY DESIGN Three-dimensional CBCT images of 458 maxillary first molars and 467 second molars from 276 Korean patients were analyzed to determine the incidence of an MB2 canal, the types of canal configurations, and the correlations between the incidence of an MB2 canal and age, gender, and tooth position. RESULTS The incidence of 2-canaled MB roots was 71.8% in first molars and 42.2% in second molars, with the most common configurations being Weine types III and II. The frequency of an MB2 canal decreased with age in both molars (P < .05). CONCLUSIONS Types III and II canal configurations were the most prevalent in the 2-canaled MB roots of Korean maxillary molars.

Personal Computer-Based Three-Dimensional Computed Tomographic Images of the Teeth for Evaluating Supernumerary or Ectopically Impacted Teeth

This study describes the use of personal computer (PC)-based three-dimensional computed tomographic (3D CT) images in the evaluation of supernumerary and ectopically impacted teeth. Three selected cases were presented as examples of the more complex cases in which 3D CT imaging added information not readily available from periapical, occlusal, or panoramic radiographs. Patients were CT scanned from the occlusal plane to the periapical region of the impacted teeth. Digital Image and Communications in Medicine CT data were transferred to a personal laptop computer using a network line. 3D volume rendering was performed using PC-based volumetric analysis software. 3D CT-reformatted imaging of the teeth is a useful way to investigate and localize supernumerary or impacted teeth. Newer software that enables this investigation using a PC provides a relatively inexpensive way to carry out such investigations, making it easier for dental practitioners to request such investigations and to view the results in real time in their own offices.

A radiographic study of the posterior superior alveolar artery.

Purpose:The purpose of this study was to elucidate the differences of the prevalence and diameter of the posterior superior alveolar artery (PSAA) and the distance of its inferior border from the alveolar crest on computed tomography (CT) images according to age and sex. Materials and Methods:CT images of maxilla in 200 patients were randomly selected from patients who underwent CT imaging at Yonsei University Dental Hospital, and analyzed. The prevalence of the PSAA in maxillary sinus and the distance of its inferior border from the alveolar crest in the premolar and molar area were measured. Results:The average prevalence of the PSAA on CT images was 52.0%, and it is higher in males (64%) than in females (40%). The diameter of the PSAA was 1.52 ± 0.47 mm (mean ± SD), and larger in males. The distance from the PSAA to the alveolar crest was greater in the premolar area (18.90 ± 4.21 mm) than in the molar area (15.45 ± 4.04 mm), and it did not differ significantly with age or sex. Conclusions:The prevalence of the PSAA on CT images was higher, and the diameter was larger in males. The PSAA was more close to the alveolar crest in the molar areas. The evaluation of the PSAA in maxillary sinus on CT images before surgery could reduce the likelihood of excess bleeding during surgery especially in molar areas.

Orthodontic extrusion of the lower third molar with an orthodontic mini implant.

Neurologic changes owing to damage to the inferior alveolar nerve (IAN) are the most serious complication of lower third molar (M3) extraction because of their close spatial relationship. We adopted the concept of regional orthodontic treatment and extrusion, using skeletal anchorage with an orthodontic mini implant. Two malformed M3s that were closely apposed to the IAN were extruded with the aid of 3 or 4 orthodontic brackets and a mini implant. Both of the M3s were extruded successfully. The patients experienced little discomfort with the orthodontic appliances and there was neither permanent neurologic damage nor fracture of the root fragments following subsequent M3 extraction. Orthodontic treatment using a miniscrew to separate the IAN and M3, or luxation of the M3 may be a good alternative treatment option for extrusion of a vertically impacted lower M3 with fragile roots.

A portable dental image viewer using a mobile network to provide a tele-dental service

We tested three imaging devices for suitability in emergency dental situations for telemedicine. The three devices were a special-purpose oral camera, a digital single lens reflex (DSLR) camera, and the built-in camera of a mobile phone. A total of 20 subjects volunteered to take part in the study. We simulated five different conditions which could affect the quality of the image and measured image transmission times across two widely available mobile networks (a CDMA-based 3G network and a Wireless Broadband Network, WiBRO). The DSLR produced the best quality images, although it was a relatively large device and not easy to use. The oral camera failed to give satisfactory images under certain conditions (i.e. without extra lighting, out of focus and head motion). In contrast, the mobile phone based camera was very easy to use and to handle, and it gave good information for initial diagnosis, even at high compression ratios. If the image acquisition conditions are carefully set up, this device might be the best for emergency dental trauma situations.

Toothbrushing Region Detection Using Three-Axis Accelerometer and Magnetic Sensor

Due to the possible occurrence of periodontal disease at an early age, it is important to have proper toothbrushing habits as early as possible. With this aim, the feasibility and concept of a smart toothbrush (ST) capable of tracing toothbrushing motion and orientation information was suggested. In this study, we proposed the advanced ST system and brushing region classification algorithm. In order to trace the brushing region and the orientation of a toothbrush in the mouth, we required the absolute coordinate information of ST. By using tilt-compensated azimuth (heading) algorithm, we found the inclination and orientation information of the toothbrush, and the orientation information while brushing inner tooth surfaces showed specific heading features that could be reliably discriminated from other brushing patterns. In order to evaluate the feasibility of clinical usage of the proposed ST, 16 brushing regions were investigated by 15 individual healthy subjects. The proposed ST system demonstrated 97.1%(±0.91) of the region detection accuracy and 15 brushing regions could be classified. This study also showed that the proposed ST system may be helpful for dental care personnel in patient education and instruction for oral hygiene regarding brushing habits.

Development and evaluation of a CMOS sensor-based digital intra-oral radiographic system

As part of an ongoing investigation into the development of a dental digital radiographic (DDR) system using a complementary metal-oxide semiconductor (CMOS) sensor, this study developed hardware and software with a graphical user interface to acquire and display intra-oral images from a prototype DDR system. The aim of this study was to develop a DDR system using a CMOS sensor and evaluate its characteristics. Electrical signals that were generated by the CMOS sensor were transformed into digital images by a control computer equipped using a USB board. The distance between the X-ray tube and the CMOS sensor was adjusted within the range of 10-40 cm to provide the optimal image quality. In order to evaluate the image quality according to variations in the dose, phantom images (60 kVp, 7 mA) were obtained at exposure times of 0.03, 0.05, 0.08, 0.10, and 0.12 s, and the signal-to-noise ratio (SNR) was calculated from the phantom image data. The modulation transfer function (MTF) was obtained from a Fourier transform of the line spread function, which was itself derived from the edge spread function of a sharp edge image acquired using the exposure conditions of 60 kVp, 7 mA, and 0.08 s exposure time. The best contrast and focus were obtained at 20 cm. The SNR level was found to increase with increasing exposure time ranging from 0.03 to 0.08 s. The results obtained at 10% of the MTF showed that the resolution of the DDR system was approximately 6.2 line pairs per millimeter. The characteristics of the prototype DDR system have potential applications in intra-oral dental radiographic imaging. The fully developed DDR system can be used for making a clinical diagnosis with further improvements in the acquisition time and spatial resolution.

Alignment of CT images of skull dysmorphology using anatomy-based perpendicular axes

Rigid body registration of 3D CT scans, based on manual identification of homologous landmarks, is useful for the visual analysis of skull dysmorphology. In this paper, a robust and simple alignment method was proposed to allow for the comparison of skull morphologies, within and between individuals with craniofacial anomalies, based on 3D CT scans, and the minimum number of anatomical landmarks, under rigidity and uniqueness constraints. Three perpendicular axes, extracted from anatomical landmarks, define the absolute coordinate system, through a rigid body transformation, to align multiple CT images for different patients and acquisition times. The accuracy of the alignment method depends on the accuracy of the localized landmarks and target points. The numerical simulation generalizes the accuracy requirements of the alignment method. Experiments using a human dried skull specimen, and ten sets of skull CT images (the pre- and post-operative CT scans of four plagiocephaly, and one fibrous dysplasia patients), demonstrated the feasibility of the technique in clinical practice.