• The korean journal of orthodontics
• /
• v.23 no.4 s.43
• /
• pp.503-527
• /
• 1993

This paper describes a new method to create an animal model for TMJ internal derangement in the New Zealand white rabbits and the light and electron microscopical changes of posterior attachment of them. Twenty six rabbits(2.5-3.0kg), four normal and twenty two experimental, were used. The right disc of experimental animal was displaced anteriorly without sectioning the posterior attachment and tied to the zygomatic arch with nylon not to be reduced to the original position. The left TMJ was sham-operated to be compared with its right experimental one. Normal animals were sacrificed one day and eight weeks after experiment. Experimental animals were sacrificed one day, ten days, three weeks, five weeks and eight weeks after surgery respectively. They were fixed intravenously with $2\%$ glutaldehyde under general anesthesia and the samples of them were processed for light and electron microscopic examination. The purpose of this experiment is to make a suitable animal model of disc displacement without reduction for studying and understanding the cellular and morphologic events in posterior attachment of TMJ including early changes which were difficult to be observed in human TMJs. The results of this investigation suggest the following conclusions : 1. Authors induced anterior disc displacement surgically in rabbits with new method to examine histologic changes of posterior attachment. Tissue reactions of this model seem to be similar to those observed in human disc displacement. We think this animal model for anterior disc displacement may be used to explore and evaluate objectively the effects of many treatment modalities in disc displacements. 2. The animal disease model showed inflammation at early stage(one and ten days). At this stage there were mild-to-severe mononuclear inflammatory cell infiltration, numerous newly formed vessels, vessel dilatation and engormement and many fibroblasts. 3. At middle stage(three weeks), fibrosis occurred, where fibroblasts decreased in number, but their cytoplasm was profuse indicating high activity. Collagen fibers increased in number and the tissue looked more dense. 4. At late stage(five weeks and eight weeks) showed degenerative changes including perforation of posterior attachment, disintegration of collagen fiber bundles, degeneration of fibroblasts, metastatic ossification, and dystrophic calcification.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.39 no.3
• /
• pp.146-157
• /
• 2023

The bite collapses due to posterior teeth loss or wear results in inadequate space for restoration and esthetic concerns. Increasing the occlusal vertical dimension to improve space deficiency rotates the mandible posteriorly, creating a gap between the maxillary and mandibular anterior teeth, leading to loss of anterior guidance. To solve this problem, the prosthodontics or orthodontics treatments are the commonly used methods for proper anterior guidance. However, it is reasonable to assume that the anterior teeth can naturally relapse to their original position when the occlusal force is eliminated. Therefore, this case report aimed to test whether natural relapse could recover the lost anterior guidance to develop a less invasive and more convenient treatment method. Digital superimposition was used to evaluate the changes in anterior teeth alignment to confirm the change of the recovered anterior guidance. The appropriate indications for this new treatment method were defined and applied clinically.

• The Journal of Korean Academy of Prosthodontics
• /
• v.38 no.5
• /
• pp.675-694
• /
• 2000

The purpose of this study was to investigate the displacement of and the stress distribution on the prosthesis, abutment, and its supporting tissues under functional load, and the effect of alteration in root length of 2nd abutment. The 3-dimensional finite element method was used and the finite element models were prepared in which the abutments of left mandibular 5 unit axed partial denture were canine, the 1st pre-molar and the 2nd molar, and the root lengths of canines were as follows. Model I : Root length of canine was 2mm longer than the 1st premolar Model II : Root length of canine was 2mm shorter than the 1st premolar Static compressive force of 300N was applied to connector between 2nd premolar & 1st molar, and then von Mises stress, displacement and reaction force were obtained. The results were as follows : 1. In fixed partial denture, prosthesis under load on pontic was rotated around mesio-distal long axis of it from longual side to buccal, and simultaneously bended in buccal and gingival direction with mesial end deformed in gingival direction and distolingual end in occlusal. 2. Clinical crowns of abutments were bended in the same directions with those in which prosthesis deforms. Due to that, roots of anterior abutments were twisted in counterclockwise with concentration of shear stress on distal or distobuccal sides of their cervices, and that of posterior was in clockwise with concentration of shear stress on mesiobuccal side of it in the same level with anterior abutments. 3. In case that root length of the 2nd abutment was longer than that of the 1st abutment, its displacement and reaction force which means the force tooth exerts on the surrounding periodontal tissues were smaller but shear stress on itself was larger than in the case root length of 2nd abutment was shorter.

• The korean journal of orthodontics
• /
• v.48 no.5
• /
• pp.304-315
• /
• 2018

Objective: The purpose of this study was to analyze initial displacement and stress distribution of the maxillofacial complex during dentoskeletal maxillary protraction with various appliance designs placed on the palatal region by using three-dimensional finite element analysis. Methods: Six models of maxillary protraction were developed: conventional facemask (Type A), facemask with dentoskeletal hybrid anchorage (Type B), facemask with a palatal plate (Type C), intraoral traction using a Class III palatal plate (Type D), facemask with a palatal plate combined with rapid maxillary expansion (RME; Type E), and Class III palatal plate intraoral traction with RME (Type F). In Types A, B, C, and D, maxillary protraction alone was performed, whereas in Types E and F, transverse expansion was performed simultaneously with maxillary protraction. Results: Type C displayed the greatest amount of anterior dentoskeletal displacement in the sagittal plane. Types A and B resulted in similar amounts of anterior displacement of all the maxillofacial landmarks. Type D showed little movement, but Type E with expansion and the palatal plate displayed a larger range of movement of the maxillofacial landmarks in all directions. Conclusions: The palatal plate served as an effective skeletal anchor for use with the facemask in maxillary protraction. In contrast, the intraoral use of Class III palatal plates showed minimal skeletal and dental effects in maxillary protraction. In addition, palatal expansion with the protraction force showed minimal effect on the forward movement of the maxillary complex.

• The korean journal of orthodontics
• /
• v.24 no.2
• /
• pp.275-294
• /
• 1994

The occlusal interference during adolescent period makes some effects on growth and development and morphological changes. And so, if we could predict the the timing and results of orthodontic treatment who have occlusal interference during adolescent period, it may be helpful for diagnosis and treatment planning of orthodontic treatment. For about those, the purpose of this study was to evaluate the effects of the posterolateral displacement by the metal casting crown with inclined pathway on the mandibular condyle and morphologic changes of mandible in the rat. The experimental animals were thirty six Sprague-Dawley male rats of 8 weeks old. Eight of them was used as control group, and experimental group 1 ( continuous appliance wearing group ) was composed of sixteen and experimental group 2 ( appliance removal group after worn the appliances during 3 months ) was composed of remaining twelve. The animals of experimental grouop 1 were sacrificed after 1, 2, 3, 6 months from beginning of the experiment and experimental group 2 were sacrificed 1, 2, 3 months after removal of the appliance from worn the appliance during 3 months. Both of mandible and temporomandibular joint were observed histologically and radiologically. The results were as follows : 1. In experimental group 1, the mandibular length and lower posterior height were decreased with experimental period, while the lower anterior height was increased, and the curvature of lower incisors and lingual inclination of anterior alveolar bone were profound as compared with control group. 2. In experimental group 1, both of the thickness of the condylar cartilage were thinned in the posterosuperior region, and this phenomenon was more prominent on right than left in 3-Mo experimental period and both sides were marked thinned in 6-Mo experimental period. 3. In experimental group 2, the lower anterior height was low and lower posterior height was high as compared with experimental group 1, and the curvature of lower incisors and lingual inclination of anterior alveolar bone were recovered to control group. 4. In experimental group 2, both of the thickness of the condylar cartilage were thickened in the posterosuperior region, and this phenomenon was more prominent with experimental period. 5. In experimental group 2, the mandibular length was short, lower anterior height was hight, the curvature of lower incisors were profound, and in histologically, both of the thickness of the condylar cartilage were thickened in the posterosuperior region as compared with control group. As shown above, the occlusal interfemce affected the condylar cartilage, curvature of lower incisor, inclination of anterior alveolar bone, mandibular length, and anterior and posterior height. When the interference was removed, significant recover was found in condylar cartilage, mandibular length, and posterior height. Although no significance was found, other items of measurement showed trends for recovery.

• Imaging Science in Dentistry
• /
• v.32 no.3
• /
• pp.181-185
• /
• 2002

The melanotic neuroectodermal tumor of infancy is a rare neoplasm arising in the first year of life. A 33-day-old female infant had an enlarged alveolar ridge on the right anterior maxilla. Intraoral examination revealed a nonulcerative swelling at the site. An intraoral radiograph showed an ill-defined radiolucency on the right anterior maxilla and displacement of primary incisors from their alveolar sockets. CT scans revealed an expansion of the surrounding bone and partial destruction of the anterior wall of the premaxilla. Histopathologic examination showed the cytoplasm of neuroblastic cells and eosinophilic, epithelioid cells frequently contained a dark brown granular pigment that stained positively to vimentin and HMB45, focally positive to NSE and cytokeratin. Four weeks after the operation, CT scans showed a rapidly growing soft tissue mass occupying right maxillary sinus encroaching to the orbit and nasal cavity. The final diagnosis was made as a malignant melanotic neuroectodermal tumor of infancy.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.23 no.3
• /
• pp.615-623
• /
• 1996

Face mask is an extraoral appliance which used to protract maxilla, and can help in the correction of moderately severe class IlI malocclusions by the anterior displacement of the maxilla and maxillary dentition, and possibly restricting or changing the direction of the growth of the mandible. In three cases the results were followed. 1. Anterior crossbite was corrected 2. Maxilla & maxillary dentition were displaced forwardly. 3. Lingual tipping of the mandibular incisors, and backward & downward rotation of mandible were performed. 4. Acceptable improvement in the class III profile was performed.

• Physical Therapy Korea
• /
• v.12 no.1
• /
• pp.11-21
• /
• 2005

The purpose of this study was to investigate how COP displacement of a hemiplegic foot in stance phase during gait is related to clinical balance measures and the recovery stage in hemiplegic stroke patients. Twenty-eight functionally ambulant hemiplegic patients who had suffered from strokes and thirty age-matched healthy subjects participated in this study. COP parameters were calculated. Clinical balance was measured using the Functional Reach Test (FRT) and Timed Up and Go Test (TUGT). The recovery stage, proprioception, and clonus of the ankles or lower extremities were also measured for physical impairment status. The COPx max-displacement in the medial-lateral side of the stroke patients was significantly longer than that of the normal group (p=.038). The COPy max-displacement in the anterior-posterior side of the stroke patients was significantly shorter than that of normal group (p<.001). Significant differences in the COPx and COPy displacement asymmetry index were found between the two groups (p<.01). The FRT was correlated with the COPx displacement (r=.552) and COPy displacement (r=.765). The TUGT was correlated with the COPy displacement (r=-.588) only. The recovery stage of the lower extremities was correlated with COPy displacement (r=.438). The results of the study indicate that the characteristic of COP displacement in hemiplegic feet in stance phase during gait is related to balance ability and recovery in stroke patients. COP parameters acquired by the mapping of foot pressure in stance phase during gait will provide additional useful clinical information. This information can be used by clinicians to assess objectively the pathologic gait with other diseases and to evaluate the therapeutic effects on gait in stroke patients.

• PNF and Movement
• /
• v.16 no.2
• /
• pp.267-273
• /
• 2018

Purpose: Leg length discrepancy (LLD) is one of the risk factors for postural imbalance. This study aimed to investigate the effect of induced leg length discrepancy on the limitation of stability (LOS) and static postural balance. Methods: Thirteen adults (males, 7; females 6) participated in this study. The LOS and static postural balance [sway length, sway area, and sway velocity of center of gravity (COG) displacement] were measured by the balance trainer system. The subjects were asked to move the COG for the anterior, posterior, and left and right directions maximally and to keep standing on the platform with and without induced LLD for 30 s in the open and closed eyes conditions, respectively. The LLD was artificially induced to 2 cm using insole. Wilcoxon test was used to compare the LOS and the static postural balance between with and without induced LLD. Results: The anterior and posterior LOS significantly decreased in induced LLD (p<0.05), and the left and right LOS were not significantly different between with and without LLD (p>0.05). Sway length, sway area, and sway velocity of the COG displacement significantly decreased in induced LLD (p<0.05). Conclusion: This study suggests that induced LLD could decease the antero-posterior LOS and increased the static postural balance. Therefore, the LLD could disturb the postural balance.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.27 no.5
• /
• pp.457-462
• /
• 2005

The aim of this study is to evaluate the relative signal intensity of TMJ retrodiscal tissue in T2-weighted MRI as diagnostic marker of temporomandibular disorder(TMD). 58 temporomandibular joints from 29 TMD patients (14 men & 15 women) were evaluated. The relative signal intensity of retrodiscal tissue in T2-weighted MRI was referenced to brain gray matter same size of the region of interest(ROI). The collected data was compared to disc positions (normal, anterior disc displacement with reduction, anterior disc displacement without reduction), the presence of joint effusion. The relative signal intensity of retrodiscal tissue was significantly increased when the disc was displaced without reduction. And the relative signal intensity of retrodiscal tissue was significantly increased when joint effusion was present. The results suggest that evaluating the relative signal intensity of TMJ retrodiscal tissue using a T2-weighted MRI is valuable as a non-invasive tool for diagnosing the procession of TMD.