• Journal of Oral Medicine and Pain
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• v.31 no.3
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• pp.265-274
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• 2006

Temporomandibular joint (TMJ) internal derangement, especially disc displacement with reduction (DDwR) is the most common TMJ arthropathy and has been thought to do some effects on masticatory performance. Measuring of maximal bite force has been widely used as objective and quantitative method of evaluating masticatory performance, but previous studies showed various results due to various characteristics of subjects and different measuring devices and techniques. In a few studies about the correlation of bite force and temporomandibular disorders (TMD), some authors reported that bite force and masticatory performance would be reduced in patients with TMD because of pain. But the correlation of changes in structure of articular disc and masticatory performance has not been well investigated yet. In this study, to investigate the influences of non-painful disc change on the masticatory performance, we measured the value of maximal bite force, occlusal contact area and occlusal pressure of 39 patients with non-painful DDwR of the TMJ using pressure sensitive film, and compared it with that of 59 controls. The results are summarized as follows: 1. The maximal bite force (P<0.01) and the occlusal contact area (P < 0.05) of the DDwR patients were greater than the controls. 2. There was no significant difference in occlusal pressure between the DDwR patients and the controls (P > 0.05). 3. The maximal bite force of the male group was greater than that of the female group (P < 0.05). However, the occlusal contact area and the occlusal pressure between the male and the female group didn't show significant difference (P > 0.05). From the results above, we can suggest that DDwR could be a factor of changing bite force, but more controlled, large scaled and EMG related further study is needed.

• The Journal of Korean Academy of Prosthodontics
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• v.17 no.1
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• pp.35-46
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• 1979

A number of experimental studies have been carried out in order to clarify the question as to how temporomandibular joint adapt to the changes of mandibular movement and occlusal equilibration. Recently, the studies on the interrelations between anatomical structure of temporomandibular joint and the state of occlusion have been actively performed in dentistry particularly in prosthodontic field. Author performed extraction of unilateral mandibular molars in 30 mature male rats, and observed histological changes of temporomandibular joint through the light microscope. Following results were obtained. 1. The loss of unilateral teeth gave rise to the changes in the location of condylar head, that is, interior displacement of condylar head in the extraction side and upper displacement in the non-extraction side. 2. Articular disk was compressed by the interior surface of condylar head, resulting in its extension below the condylar neck in the extraction side, and the histological arrangement of the compressed area showed irregular feature. 3. The extension of articular disk below the condylar neck was accompanied with the contraction of muscle fibers which were originated from the articular disk. 4. The cartilage layer of articular fossa to the exterior of the extraction side showed hypertropy. 5. Early in the experiment, the inernal extremity of condylar head of extract ion side showed bone resorption, and cartilage layer of condylar head showed hypertropy. At 12 weeks after experiment, the condylar surface showed flattened, and the cartilage layer of condylar head was replaced by the compact bone. 6. The articular disk showed the formation of pannus in the extraction side as well as in the non-extraction side. 7. The occlusal disturbance due to unilateral missing teeth has brought about the non-inflammatory retrogressive change and osteoarthrotic change late in the experiment.

• Journal of Oral Medicine and Pain
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• v.14 no.1
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• pp.57-66
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• 1989

66 patients with temporomandibular disorders were selected for experimental group, and 45 normal subjects who were Dental students were selected for control group. Average age of experimental group was 30.5 years, Male to Female ratio was 2 : 3, and their age distribution were teen-ages to seventh decades. Transcranial radiography (TR) with Denar Accurad 100 was used for each group to get the values of width in joint spaces and to investigate the bony changes of articular surfaces and relative condylar position to articular fossa. In addition to TR, clinical interview and routine charting about amount of mandibular movements and occlusal variations were carried out in experimental group. The obtained results were as follows : 1. The mean values of joint space with in control group were 2.15mm to anterior, 2.98mm to superior and 2.29mm to posterior and the value of relative condylar position to the deepest portion of articular fossa was 0.21mm to anterior. In experimental group, those values were 2.01mm, 2.14mm 2.22mm and 0.12mm to posterior in sequence, respectively. Joint spaces in experimental group, therefore, were inclined to decreased, and relative condylar position was inclined to retrude. Joint space in control group showed symmetric condylar position, but in experimental group showed asymmetry. 2. Non-affected joints with no bony changes in experimental group showed the narrowest joint spaces which were thought to manifest the abnormal stress to non-affected side to dysfunctional state of contralateral affected joints. 3. Amount of mandibular movements in experimental group were within normal values in lateral movements and in protrusive movement but in opening movement with or without passive stretch, those were lower than normal values. Frequency of occlusal variation, for example, protrusive posterior contacts, open bite, median line shift to lateral side were inclined to increase with bony changes and with crepitus.

• Journal of Dental Rehabilitation and Applied Science
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• v.16 no.2
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• pp.93-104
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• 2000

Orthodontic treatment in conjunction with second-molar extraction has been a controversial issue among orthodontists over many decades. The aim of this study was to investigate the treatment effects of upper second molar extraction cases. The sample included 19 upper second molar extraction orthodontic cases(ten Angle's Class I's and nine Class II's, average age=13Y 6M) cared at Kyung-Hee University Department of Orthodontics. Lateral cephalometric radiographs were taken before and immediately after treatment. Seventy-nine points were digitized on each cephalogram and 38 cephalometric parameters were computed comprising 22 angular measurements, 13 linear measurements, and 3 facial proportions. The data obtained from each malocclusion group were analyzed by paired t-test. The statistical results disclosed that there was no significant change in skeletal pattern after treatment except for that accountable by growth while there was statistically significant change in dentoalveolar and soft tissue patterns. There were no significant changes in Bjork sum, posterior facial height /anterior facial height and lower anterior facial height /anterior facial height. No significant changes in anteroposterior position of maxilla and palatal plane were manifested. Although facial axis and lower facial height was slightly increased and the mandible was rotated backward and downward, there was no remarkable change in the mandibular plane. There were statistically significant changes in distal movement of upper first molar, molar key correction and overjet reduction while there was no change in the occlusal plane. The upper lip was slightly retracted simultaneously with slight increase in nasolabial angle. These results signify that distalization of upper dentition with the second molar extraction does change occlusal relationship without gross modifications in the craniofacial skeletal configurationson. Henceforth the second molar extracted would be recommended to treat severe anterior crowding and protrusion with minor skeletal discrepancy.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.3
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• pp.225-232
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• 2011

Purpose: This study was designed to retrospectively evaluate the postsurgical initial stability of the Le Fort I osteotomy with posterior impaction and rigid internal fixation for the correction of mandibular prognathism with midface deficiency. Particular attention was paid to the magnitude and direction of the initial postsurgical change. Methods: 20 healthy patients with mandibular prognathism and midface deficiency participated in this study. All patients underwent Le Fort I osteotomy with posterior impaction and mandibular setback BSSO by one surgeon. Preoperative (T0), immediate postoperative (T1) and follow-up period (T2) cephalograms were taken and analyzed. Change between T0~T1 and T1~T2 was measured and analyzed. Results: Between T0~T1, significant differences were observed in all measurements except the ANS point and mandibular plane angle. Between T1~T2, only the occlusal plane angle was significantly changed. No significant changes were found in all other measurements. Conclusion: This study indicates that Le Fort I osteotomy with posterior impaction is stable at initial stages. Although changes in the occlusal plane angle were observed, it was caused by tooth movement after post-operative orthodontic treatment. However, more studies with larger samples are required to form definitive conclusions. Conclusion: This study indicates that Le Fort I osteotomy with posterior impaction is stable at initial stages. Although changes in the occlusal plane angle were observed, it was caused by tooth movement after post-operative orthodontic treatment. However, more studies with larger samples are required to form definitive conclusions.

• The korean journal of orthodontics
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• v.37 no.4
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• pp.260-271
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• 2007

The purpose of this study was to evaluate the relationships between the occlusal plane angle and craniofacial skeletal pattern in relation to anterior overbite. Methods: Lateral cephalograms of 90 adults with skeletal class III malocclusions were traced and measured to analyze skeletal factors and occlusal plane angles. In terms of anterior overbite, all patients were classified into 3 subgroups of positive overbite, edgebite, and negative overbite groups. All measurements were evaluated statistically by ANOVA and Duncan's Post Hoc, and correlation coefficients were evaluated among measurements. Results: In this study, some skeletal measurements (saddle angle, articular angle, Y axis, AFH, SN-FH, SN-Mn, FH-Mn) showed a significant difference among the 3 groups in relation to overbite changes. Correlation coefficient showed that PFH/AFH, SN-Mn, Mx-Mn, and FH-Mn showed a significant difference with FH-Occ, Mx-Occ, and Mn-Occ. Regression analysis showed that Mx-Mn had a determination coefficient of 0.714, 0.560, and 0.677 in relation to FH-Occ, Mx-Occ, and Mn-Occ, respectively. Conclusion: This study suggests that consideration of the occlusal plane in relation to the maxillomandibular vertical skeletal state enable the establishment of a more predictable orthognathic surgery result.

• The korean journal of orthodontics
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• v.41 no.3
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• pp.154-163
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• 2011

Objective: The purpose of this study was to quantitatively evaluate relapse tendency after orthodontic treatment and determine the contributing factors by using the American Board of Orthodontics objective grading system (ABO-OGS). Methods: The subjects were 80 patients with more than 2 years of retention period after completing orthodontic treatment at the dental hospitals of Busan University, Kyunghee University, and Dankook University. The posttreatment (T2) and post-retention (T3) ABO-OGS measurements were analyzed in relation to age, gender, Angle's classification, extraction, retention period, and pretreatment condition (initial peer assessment rating (PAR) index, T1) by multiple regression analysis. Results: Among the 7 ABO-OGS criteria, alignment worsened but occlusal contact and interproximal contact improved in T3, but not in T2 ($p$ < 0.01). The 4 other criteria showed no significant differences. Multiple regression analysis showed that alignment, occlusal relationship, overjet, and interproximal contact were significant linear models, but with a low explanation power. Age, gender, Angle's classification, extraction, retention period, and pretreatment condition (initial PAR index, T1) had little influence on the ABO-OGS changes between T3 and T2. Conclusions: An orthodontist's understanding of posttreatment relapse tendency can be useful in diagnosis and during patient consultation.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.285-294
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• 1991

The human temporomandibular joint as a ginglymoarthrodial one has much in common with the other synovial joints of the body, but it does possess an unique charachteristic in that it must accomodate the various occlusal relations of dentition during an end point of closure. For that reason, the movement of the condyle in the temporomandibular joint is susceptible to influences from the nature of occlusion. Undue loading to the temporomandibular joint can be applied on the occasion of premature contacts in centric relation, balancing side interferences, change of occlusal surfaces due to excessive attrition, loss of tooth. Such occlusal disharmonies in association with the systemic and emotional factors may give rise to the temporomandibular disorder. On the other hand, the changes of occlusal patterns in the growing body can also have an effect on the growth of the temporomandibular joint through the alterations of functional stresses. The purpose of this study was to observe histopathologic response of the temporomandibular joint in unilateral chewing on one side exclusively for 10 months. Three dogs showing normal masticatory function were chosen. One dog aged about 12 months was for control, two dogs for experimental specimens were about 12 and 18 months old respectively. For chewing on the left side only, unilateral lower right premolar and molar were extracted in two experimental specimens. And then three dogs were sacrificed 10 months later. Frontal histologic sectioning of joints were done for the observation of the effects of one-side chewing. 24 specimens from three dogs were obtained and fixed in 10% formalin and routinly processed with H-E staining for histologic examination. The light microscopic findings were interpretated as follows: 1. Experimental specimen 1 aged about 22 months: In comparison with control and right non-chewing side, the proliferative and hypertrophic zone were increased at the mesial and lateral part of left chewing side condyle. There was no change of the articular tissue of temporal bone. 2. Experimental specimen 2 aged about 28 months: The articular tissues of adult joint were observed. The differences between the chewing and non-chewing side were not seen in the articular tissues of condyle and temporal bone.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.45-48
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• 1990

CO2 laser beam was focused by a ZnSe lens onto the center of the occlusal surface f extracted lower molars. K-type thermocouple was contacted with the pulp chamber and the changes of temperature in the during and after the laser irradiation were measured as function of the power of laser beam, the time of laser irradiation and thickness of the sample. An empirical formula for temperature effect was derived from the measured data.

• Journal of Oral Medicine and Pain
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• v.13 no.1
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• pp.43-52
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• 1988

The author studied masticatory muscle activity and bite force in normal persons without Temporomandibular Disorders(TMD) signs and symptoms, The number of subjects was 15, and the age of them was from 22 to 25 years. Electromyography was used to record the muscle activity in tapping and clenching movement with or without occlusal splint. 3 splints were made from 3 different mandibular position, that if, centric occlusion position, Rocabado's mandibular rest position, Dawson's centric relation position. The thickness of splint was 3.0-3.5㎜ at molar region. The muscle examined were Masseter and Anterior Temporalis attached with surface electrodes and the device used to measure the EMG level was Bioelectric processor Model EM2. After recording the EMG, the author measured the bite force level in clenching movement with bite force meter Model MPM-3000 in the dame position used in the EMG experiment. The obtained results were as follow : 1. With occlusal splints insetion, the amount of decreased muscle activity in Anterior Temporalis was more than those in Masseter. 2. In the three maxillomandibular relationships with occlusal splints, Masseter showed slightly increased level of muscle in centric occlusion but Ant. Temporalis showed decreased level of muscle activity reversely in that position. 3. Muscle activities between Rocabado's rest position and Dawson's centric relation position were generally similar whatever the muscles or the movements the author examined. 4. Bite force in clenching movement increased with splints insertion, especially with the splint registered in centric occlusion position.