Nihon Kyosei Shika Gakkai zasshi = The journal of Japan Orthodontic Society最新文献

In the orthodontic practice, the first or second molars are extracted by reason of a necessity based on the treatment planning. In these cases, it is desirable that the third molar would be taken part in the masticatory function. This study was made to investigate the natural movement of the erupting third molars after the extraction of the first or second molar on the serial lateral cephalometric radiographs and orthopantomographs. Subjects were divided into three groups. The first is the group which the mandibular second molars were extracted. The second is the group which the first molars were extracted bringing about the successful eruption of the third molars. The third is the group which the first molars were extracted with resultant in the failure of the third molar eruption. In all cases, the orthodontic forces were not applied to the third molars. The results were as follows: 1. In the first group, all third molars were successfully erupted and a lot of the spaces after the extraction of second molars were utilized for the eruption of third molars. 2. In the second group, all third molars were successfully erupted and a lot of the spaces after the extraction of first molars were utilized for the mesial movement of the second molars. 3. In the third group, there were various patterns of the impaction of the third molars. It was suggested that the eruption of the third molar was related to the space distal to the second molar but it was not related to the anterio-posterior length of the mandibular body significantly.

A 9 year old girl presented an impacted lower right 2nd premolar which not only was in horizontal position, but its crown was directed lingually. As a lower right 2nd premolar was in such a position that normal eruption was impossible, the deciduous predecessor was extracted at 9 years of age, and then sufficient space had been created for the lower right 2nd premolar to be erupted, and the eruption of it was observed for about 2 years. 2 years later, radiographic indication showed that no spontaneous eruption of a lower right 2nd premolar was to be expected. At 11 years of age, surgical exposure and traction of a lower right 2nd premolar was attempted. When the lower right 2nd premolar was upright, its root formation was in the 1st stage of root developmental stages according to Moorrees et al. Follow up radiographic observations on surgical exposure and traction of a lower right 2nd premolar 3 years later revealed the following results: 1. The root development went on to amount to about 90 percent of the root formation of the other tooth concerned without the curvature of the root. 2. Lamina dura and periodontal space were normal. The continued root formation was narrowing the root apex and the pulpal tissue of apical foramina was continuous with the periodontal space surrounding the root. 3. Bone deposition occurred at the alveolar crest and the latter was recontoured normally. The interdental and inter-radicular trabecula were good. As based on these results, normal development of the root of a lower right 2nd premolar with normal periodontium can be anticipated. Clinically, the lower right 2nd premolar had completely erupted and was in normal position on the arch and in occlusion. Color, vitality and mobility were normal. Periodontal support was good. The above-mentioned findings give support to the possibility that "early treatment" enables the impacted tooth to correct.

Impacted maxillary caries are often treated in the orthodontic practice. However palatally impacted maxillary canines occur in a small. They require active orthodontic traction in those cases in which surgical exposure alone will not be enough to erupt. The purpose of this article is to describe useful orthodontic treatment for the palatally impacted caries by using the ballista spring appliance. Case 1: A girl 12 years 5 months of age had Angle Class 1 malocclusion with anterior cross bite and crowding teeth. Case 2: A woman 28 years 2 month of age had Angle Class 1 malocclusion with crowding teeth. The results were as follows: 1. After the impacted canines retracted and guided into the dental arch in correct position, the condition of the canines and tissues around have been stabilized. 2. The ballista spring appliance was effective in pulling the palatally impacted maxillary canines forward vertical direction.

The purpose of this study was to determine whether a micro-pulsed electrical potential on the tooth surface could induce effective remodeling of the alveolar bone and enhance tooth movement. Twenty-eight cats were divided into 4 groups of 7 animals each for 1, 4, 7, and 14 days of treatment, respectively. A 60 gram orthodontic force was applied to distally tip the maxillary canines. In addition, the left canine only was subjected to a one hertz square wave form of 6 volts which induced a current of about 10 microA. Tooth movement and the amount of newly formed bone for the control and experimental sides were compared statistically using the Student's t test. Histochemical observations were also carried out. The results indicated that when electrical stimulus was applied to the surface of the canines in addition to mechanical force: 1) The periodontal tissue was affected. 2) The teeth moved more rapidly. 3) Wider areas of bone deposition and larger amounts of newly formed bone were observed on the tension side, and the amount of this newly formed bone increased with time. 4) More osteoblasts were observed on the tension side. 5) More tartrate-resistant acid phosphatase (TRACP) positive mononuclear and multinuclear cells were seen on the compression side. These results indicate that micro-pulsed electrical stimulation might play a role in the efficient remodeling of alveolar bone, and in inducing more rapid tooth movement.

Occlusal disharmony is considered to be the most significant factor of temporomandibular joint (TMJ) dysfunction, but the relationship between malocclusion and TMJ dysfunction has been unknown yet. The purpose of present study was to investigate the relationship between TMJ dysfunction and occlusal disharmony (eccentric occlusal contacts and functional shift of the mandible) in orthodontic patients. The subjects were 533 orthodontic patients, 209 males and 324 females, who were received at the Department of Orthodontics, School of Dentistry, Hokkaido University from April 1985 to March 1988. Their ages ranged from 8 to 38 years old. All were prior to orthodontic treatment. The results were as follows 1. The prevalence of TMJ dysfunction was 27.6%, 24.9% in males and 29.3% in females. The difference was insignificant between males and females. 2. The patients with TMJ dysfunction increased after 13-15 years old, corresponding to dental age IV A (Hellman's classification). 3. In patients with TMJ dysfunction, the highest frequency of symptom of TMJ dysfunction was joint sounds (77.6%), the second was pain (22.4%), the third was disturbance of mandibular movement (4.8%). The complication of those symptoms were compounded in 26.3% of the total patients. 4. The prevalence of TMJ dysfunction had no relation to specific malocclusion and maxillofacial morphologic characteristic. 5. Most patients with TMJ dysfunction had occlusal disharmony (95.9%). 6. Eccentric occlusal contacts were found most frequently in patients with open bite and functional shift of the mandible was found most frequently in patients with deep bite. From these findings, the prevalence of TMJ dysfunction was frequent in orthodontic patients, however the symptoms were objective and the patients were not aware of TMJ dysfunction. TMJ dysfunction had no relation to specific malocclusion but some kinds of occlusal disharmony were easy to occur in specific malocclusion and TMJ dysfunction was induced by those etiological factors.

Morphological analysis of the craniofacial deformity has been performed by cephalometric radiography, but even with this method, it is difficult to analyze the cases with complicated deformity. The purpose of the present study is to develop the new 3-D CT morphological analyzing system in order to investigate complicated craniofacial deformity. Using the 67 landmarks, we established the 3 D line drawing method. Then the reproducibility of the landmarks were examined and the clinical cases were investigated. The measurement of landmarks were carried out 10 times by the same operator, and standard deviation of 67 landmarks were calculated. Some landmarks which were difficult to identify showed high value of standard deviation. However, it was almost same value between standard deviation of most of the landmarks and the CT system error. Therefore, location of landmarks in the system were found to be reproducible. This new analyzing system was performed in clinical cases with craniofacial deformity. In such cases, cranium deformity and complicated deformity such as twist-form arrangement of cranium, maxilla and mandible were detected. The 3-D CT morphological analysis is effective for analyzing severe craniofacial deformity which was impossible to recognize with conventional cephalometric analysis.

The present study was undertaken to discuss the effects of parameters on using the principal component analysis for the evaluation of the craniofacial structures. Materials consisted of lateral roentgenocephalograms of 100 adult Japanese females. They were divided into three groups by ANB angle. Linear and angular measurements were selected as parameters to apply the principal component analysis, and scattergrams made by the first and second principal component were compared. The results of the analysis were varied by the parameters. Especially there was a great difference between the real size and the value corrected by isometric method on scattergrams made by the first and second components. Results indicated the importance of using appropriate parameters for the research purpose.

This paper describes the relationship between the development of skeletal open-bite malocclusion and the tooth-to-denture base discrepancy. The cases which have a severe skeletal open-bite malocclusion are presented to evaluate the causing factor of the anterior open-bite. The anterior open-bite was associated with inferiorly positioned maxillary molars caused by the squeezing out effect of the tooth-to-denture base discrepancy, especially those in posterior part of dentition (posterior discrepancy), which provided a less steep maxillary occlusal plane in the denture frame. It was suggested that the posterior discrepancy induced a descending movement of the posterior teeth followed by a change of the occlusal plane and this effect of the posterior discrepancy was important factor in developing anterior open-bite malocclusion.

This study was made in order to develop and evaluate three-dimensional simulation programs in planning for orthognathic surgery by using microcomputer system. Microcomputer system is composed of CPU (NEC, PC-9801), high resolutional color display, color printer, image scanner, and MOUSE. This simulation is composed of four procedures. 1. Data input Three-dimensional coordinate data on tracing obtained from CT films is inputted. One data file is made from one outline of structures. 2. Three dimensional reconstruction A control file is made to arrange data files constructing structures. 3. Simulation This procedure is composed of cutting and movement. The horizontal projection of mandible is displayed. After cutting simulated orthognathic surgery is designed, new data files and new control file are made. A movement consists of parallel translation and rotation. A movement data is combined with movements designed on each of three projections. 4. Three-dimensional graphic display Three-dimensional graphics of the mandible before and after a simulation for orthognathic surgery are displayed by perspective views with treated hidden lines and accurate pictures (COSMOZONE 2SA, NIKON). These simulation programs were carried out with the asymmetrical patient. The simulation was supposed that the operation was combined with sagittal splitting osteotomy of the right mandibular ramus and body ostectomy of the left lower first premolar part. Three-dimensional graphics of the mandible before and after the simulation were presented. Its three-dimensional mandibular position and form after orthognathic surgery were predicted. These three-dimensional simulation programs may be important procedure, when a treatment planning in asymmetrical prognathic case is discussed.

The present study was attempted to establish the model of transseptal fibers in vitro to clarify the remodeling mechanisms of the fibers during orthodontic treatment. Human premolars were transversally cut. The thickness of films was 150 microns and a pair of dental rings was placed at intermediate of 500 microns in tissue culture dishes. Human gingival fibroblasts were seeded in these dishes and cultured. Culturing of these cells were changed at 1, 5, 10 and 20 days and used to histological observation. The following results were obtained: 1. It was observed that human gingival fibroblasts and fibrillar materials oriented approximately the surfaces of sliced teeth and extended the process of cells along the direction from sliced teeth to another one. The bridges of cells and fibers between two sliced teeth were completed after 10 days culturing. 2. The fibrillar materials were examined by TEM and bundles constructed from banded fibrils which each band was 60 nm in diameter. The red fibers were stained with Van Gieson's stain method and so many red fibers filled in the space between the two sliced teeth. This suggests that the most of fibrillar materials were collagen fibers formed from human gingival fibroblasts. The structural materials were assumed to be resembled to transseptal fibers in vivo. This culture system is usefull to study the remodeling mechanisms of transseptal fibers in tooth movement.