• The Journal of Korean Academy of Prosthodontics
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• v.40 no.6
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• pp.560-571
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• 2002

Jaw relations and the recording methods have been controversial aspects of dentistry. The purpose of this study was to quantify the relative muscle activity of the masseter and temporal muscles in relation to different intermaxillary relations recorded by intra-oral tracer during maximal clenching and to decide the optimal mandibular position. Ten volunteers with healthy TMJ were studied. Intra-oral tracer was assembled and bite block was fabricated in the articulator. Intra-oral tracer was placed in the mouth, and four mandibular positions were recorded. EMG activity was recorded on a BIO-PAK system (Bio-Research Associates, Inc. USA.) in masseter and temporal muscle and compared in each mandibular positions. The results were as follows: 1. In comparison with maximum intercuspation, the chewing position was the most similar followed by tapping position, myocentric position and posterior border position. However the differences were not statistically significant. 2. In comparison of bilateral symmetry of masseter muscle, tapping position was the most symmetrical followed by chewing position and maximum intercuspation. Myocentric position and posterior border position were not symmetrical. (P<.05). 3. In comparison of bilateral symmetry of anterior temporal muscle, chewing position was the most symmetrical followed by posterior border position, maximum intercuspation, myocentric position and tapping position. However the differences were not statistically significant. 4. In comparison of proportionality of anterior temporal muscle to masseter muscle activity on left side, posterior border position was the greatest followed by myocentric position, taping position, chewing position and maximum intercuspation. And the proportionality of posterior border position was greater than that of maximum intercuspation. (P<.05). 5. In comparison of proportionality of anterior temporal muscle to masseter muscle activity on right side, myocentric position was the greatest followed by posterior border position, tapping position, maximum intercuspation and chewing position. However the differences were not statistically significant.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.1
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• pp.75-84
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• 1995

This study was designed as a reference of vertical dimension in prosthetic treatment. The author analyzed six facial measurements, namely, (1) the height of lower face at maximum intercuspal position, (2) the height of lower face at resting position, (3) midface, (4) external ear and lateral wall of orbit, (5) interpupillary distance, (6) distance between pupil and mouth in the 100 Won-kwang Univ. Dental collage students(50 : male, 50 : female), who have normal occlusion, no posterior prosthesis, no experience of orthodontic treatment, and no deformity of facial soft tissue and no temporomandibular dysfunction. The results of this study were as follows : 1. The length of midface was shortest and the inter-pupillary distance was longest in both male and female. 2. The length difference with the length of midface and lower face at maximum intercuspal position was 5.64mm in male and 2.23mm in female, so the lower face was longer, 3. The facial measuring component, similar to lower face at maximum intercuspation, was the length of between medial wall of external ear and lateral wall of orbit. It's difference was 1.3mm in male, 1.77mm in female, and the lower face was shorter. 4. The difference of lower facial length in resting position and maximum intercuspation was 2.48mm in male, 2.24mm in female, the length of resting position was therefore longer. 5. The most clost correlation with the height of maximum intercuspal positioning lower face was resting lower face in both groups.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.6
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• pp.577-589
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• 2002

There are several variations in normal mastication. In them, unilateral mastication is chewing, predominantly on a preferred side of the dentition and hardly on e non-preferred side. Continual unilateral mastication may alter the coordination of masticatory muscles. Although they studied about these EMG of masticatory muscles, there were no information about characteristics of masticatory muscle activity in unilateral mastication. Therefore, In this study, we investigated the activity of the masseter and anterior temporal muscles during rest, clenching in maximum intercuspation and gum chewing in habitually unilateral mastication group compared with normal group and tried to know effects of continual unilateral mastication on activity of masticatory muscles. The results of this study were as follows 1. In electromyographic activity during rest, in bilateral mastication group pattern of muscle activity of right and left side was symmetrical. But, in unilateral mastication group, records of anterior part of temporal muscle was higher than that of bilateral mastication group (p<.01) and patterns of muscle activity of right and left side in both muscle were asymmetrical.(p<.05) 2. In electromyographic activity during clenching in maximum intercuspation, records of superficial part of masseter muscle were higher than anterior part of temporal muscle in both group. Muscle activity of temporal muscle in unilateral mastication group was a little higher han bilateral mastication group and asymmetry of activity pattern in temporal and masseter muscle was shown but these differences were not statistically significant. (p<.05) 3. In electromyographic activity during gum chewing, temporal muscle was activated earlier than masseter muscle and maximum bite force is derived from masseter muscle in both group. In unilateral mastication group, electromyographic activity of masseter and temporal muscle of preferred chewing side, regardless of right or left side chewing, was higher than that of bilateral mastication group and especially, difference in masseter muscle was statistically significant. (p<.01) Based on the above results, our study suggested that recording of masticatory muscle activity will be helpful in the effective diagnosis and treatment of some types of the parafunctional habits.

• The korean journal of orthodontics
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• v.44 no.6
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• pp.312-319
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• 2014

Objective: Facial-type-associated variations in diagnostic features have several implications in orthodontics. For example, in hyperdivergent craniofacial types, growth imbalances are compensated by displacement of the condyle. When diagnosis and treatment planning involves centric relation (CR), detailed knowledge of the condylar position is desirable. The present study aimed to measure condylar displacement (CD) between CR and maximum intercuspation in three facial types of an asymptomatic orthodontic population. Methods: The study was conducted in 108 patients classified into three groups of 36 individuals each (27 women and 9 men; mean age, 20.5 years), based on the following facial patterns: hyperdivergent, hypodivergent, and intermediate. To quantify CD along the horizontal and vertical axes, the condylar position was analyzed using mounted casts on a semi-adjustable articulator and a mandibular position indicator. The Student t-test was used to compare CD between the groups. Results: Vertical displacement was found to be significantly different between the hyperdivergent and hypodivergent groups (p < 0.0002) and between the hyperdivergent and intermediate groups (p < 0.0006). The differences in horizontal displacement were not significant between the groups. In each group, vertical CD was more evident than horizontal displacement was. Conclusions: All facial types, especially the hyperdivergent type, carried a significantly high risk of CD. Therefore, the possibility of CD should be carefully evaluated and considered in the assessment of all orthodontic cases in order to accurately assess jaw relationships and avoid possible misdiagnosis.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.4
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• pp.565-573
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• 1992

This clinical study was to analyze occlusal contacts in maximum intercuspation on distal extension partial denture and to compare tooth contact state between the denture teeth and abutment teeth by time mode and force mode using the T-scan system. The subjects ware twenty-one adult patients with upper natural teeth and lower distal extension partial denture. Conclusion : 1. The patient with simultaneous occlusal contacts both denture tooth and abutment and bilaterally in Kennedy Class I cases was one-sixth, but there was no one with symmetric occlusal and equal force among bilateral denture teeth and abutments. 2. The five-fifteenth of Kennedy Class I case patients resulted in simultaeous occlusal contacts bet-ween denture teeth and abutments but no one has the symmetric occlusal contacts and unifarm force between denture teeth and abutment teeth.

• Journal of Oral Medicine and Pain
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• v.31 no.3
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• pp.245-254
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• 2006

While orofacial pain or various dental factors are generally considered as the primary cause of unilateral chewing tendency, there exist several studies indicating that dental factors did not affect the preferred chewing side. The aim of this study was to examine difference of occlusal scheme between the subjects with and without chewing side preference. The difference between the chewing and non-chewing sides in the unilateral chewing group was investigated as well. Computerized, T-Scan II system was used for occlusal analysis. 20 subjects for the unilateral chewing group (mean age of $25.25{\pm}2.84$ years) and 20 subjects for the bilateral chewing group (mean age of $27.00{\pm}5.07$ years) were selected by a questionnaire on presence or absence of chewing side preference and those with occlusal problem or pain and/or dysfunction of jaw were excluded. T-Scan recordings were obtained during maximum intercuspation and excursion movement. The number of contact points, relative occlusal force ratio between right and left sides, tooth sliding area and elapsed time throughout the maximum intercuspation were calculated. Elapsed time for excursion was also investigated. The results of this study shows that the unilateral chewing group had the smaller average tooth contact areas compared with those of the bilateral group (p<0.005). In the unilateral chewing group, the contact areas of non-chewing side are smaller than those of chewing side (p<0.005). The contact areas on their preferred sides were not significantly different with those of right or left side of the subjects without chewing side preference. There was no significant difference in the elapsed time during maximum intercuspation and lateral excursion, the sliding areas and relative of right-to-left occlusal force ratio between the two groups. From the results of this study, it is likely that individuals prefer chewing on the side with more contact areas for efficient chewing.

• Journal of the korean academy of Pediatric Dentistry
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• v.21 no.2
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• pp.547-554
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• 1994

Posterior crossbites are abnormal buccal, or lingual relationship of a tooth or teeth of the maxilla, the mandible, or both when the teeth of the two arches are in occlusion and involve the molars and premolars. Posterior crossbites are classified as dental, muscular(functional), or skeletal. In an effort to avoid occlusal interferences caused by the inadequate arch width, the patient deviates the mandible laterally upon closure to achieve maximum intercuspation. This is described as functional posterior crossbite. Correction of functional posterior crossbites in the primary & early mixed dentition as early as possible after diagnosis has been recommended, because crossbites do not automatically improve with the eruption of the permanent teeth. Functional posterior crossbites, if left untreated, may have deleterious effects on the development and function of the TMJ. The diagnosis and management of three cases is presented. Each patient with functional posterior crossbites is treated using the bilateral maxillary expansion appliance.

• The Journal of Advanced Prosthodontics
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• v.12 no.2
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• pp.49-54
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• 2020

PURPOSE. The purpose of this study was to compare the performance of Accura to that of the T-scan for indicating occlusal contacts. MATERIALS AND METHODS. Twenty-four subjects were selected. Their maxillary dental casts were scanned with a model scanner. The Stereolithography files of the casts were positioned to align with the occlusal plane. Occlusal surfaces of every tooth were divided into three to six anatomic regions. T-scan and Accura recordings were made during two masticatory cycles. The T-scan and Accura images were captured at the maximum bite force and overlapped to the cast. Photographs of interocclusal records were used as the reference during overlap. The occlusal contacts were counted to compare the T-scan and Accura. McNemar's test was used for statistical significance and the corresponding P-values were calculated from a chi-square distribution with one degree of freedom. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Accura were calculated relative to the T-scan values as a control. RESULTS. No statistical differences (P>.05) were found between the T-scan and Accura methods. The accuracy of Accura was 75.8%, sensitivity was 82.1%, specificity was 60.1%, PPV was 82.9%, and NPV was 60.1%. CONCLUSION. Accura could be another possible option as a computerized occlusal analysis system for indicating occlusal contacts at maximum intercuspation.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.3
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• pp.273-282
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• 2015

Centric occlusion-maximum intercuspation (CO-MI) discrepancy is one of main causes of evoking premature contact and resultant mandibular shift. These non-physiological conditions can induce temporomandibular disease, periodontitis, and non-carious cervical lesion. Therefore, if CO-MI discrepancy exists in patients who need extensive prosthetic rehabilitation, it must be corrected and then physiological occlusion must be restored. This report describes the treatment procedure of removing CO-MI discrepancy and prosthetic rehabilitation in a patient with 3.5 mm discrepancy, multiple caries and periodontitis. Proper mandibular position and modified opening & closing movement were confirmed by ARCUSdigma II and transcranial radiograph.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.565-579
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• 1993

This study was accomplished to analyse and compare the occlusal contact patterns during eccentric mandibular movements in adult with normal occlusion. 50 subjects(male 27, female 23), who had natural occlusion and no symptom of temporomandibular disorder, were selected. Teeth contact patterns during mandibular eccentric movements were recorded and the distribution of tooth contacts in maximum intercuspation analysed by T-scan system. And then, tooth contact numbers recored by T-scan and silicone bite registration at centric occlusion were analysed and compared. The results obtained were as follows : 1. Antero-posteriorly, the qualitative center of occlusal contacts in centric occlusion were in the first molar areas, but there was a slight deviation in left-right directions. Thus, distribution of occlusal contacts were not bilaterally symmetric. 2. During the mandibular movements from centric occlusal position to right lateral and left lateral directions, the frequency that maxillary canine joined in lateral guidance was relatively high, but pure canine protected occlusion or pure group function occlusion had small frequency. 3. During mandibular protrusive movement, one or more maxillary central incisors frequently joined in protrusive guidance. 4. During mandibular eccentric movements, working and balancing side premature contact was observered in relatively high frequency. 5. In centric occlusal position, the numbers of occlusal contacts recorded on T-scan were relatively smaller than on silicone bite registration.