• The Journal of Advanced Prosthodontics
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• v.13 no.1
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• pp.36-45
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• 2021

Purpose. To investigate the fracture resistance of monolithic CAD-CAM all-ceramic surveyed crowns with two different occlusal rest seat designs. Materials and Methods. Two maxillary first premolar were prepared for all-ceramic surveyed crowns with wide (2/3rd of buccolingual width of an unprepared tooth) or narrow (1/3rd of buccolingual width of an unprepared tooth) disto-occlusal rest seat (ORS) designs. Eighty monolithic CAD-CAM all-ceramic surveyed crowns were prepared and divided into 4 groups - Group CR, Composite resin material as a control; Group LDS, Lithium disilicate based material; Group ZIPS, zirconia-material (IPS ZirCAD); and Group ZLHT, zirconia- material (CeramillZolidht+). Crowns were cemented on an epoxy resin die with adhesive resin cement. The fracture resistance of crowns was tested with the universal machine. Univariate regression analysis was used. Results. The mean ± standard deviation of maximum failure force values varied from 3476.10 ± 285.97 N for the narrow ORS subgroup of group ZIPS to 687.89 ± 167.63 N for the wide ORS subgroup of group CR. The mean ± standard deviation of maximum force was 1075 ± 77.0 N for group CR, 1309.3 ± 283.9 N for group LDS, 3476.1 ± 285.97 N for group ZIPS, and 2666.7 ± 228.21 N for group ZLHT, with narrow occlusal rest seat design. The results of the intergroup comparison showed significant differences in fracture strength with various material groups and occlusal rest seat designs (P<.001). Conclusion. The zirconia-based all-ceramic surveyed crowns fractured at more than double the load of Lithium disilicate based crowns. The crowns with narrow base occlusal rest seat design had statistically significantly higher fracture resistance than surveyed crowns with wide occlusal rest seat design. The use of narrow occlusal rest seat design in CAD-CAM all ceramic surveyed crowns provides higher fracture resistance, and therefore narrow occlusal rest design can be used for providing esthetics with high strength.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.241-251
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• 2010

This study aims at contributing to the restorative dentistry by examining results in the vertical load test of four different low invasive fixed partial dentures. Based on a hypothesis on the right upper first molar is missing, three units of FPDs were made for the second premolar and the second molar abutment. that is, twelve metal dies and FPDs were made for resin bonded FPD and Two Key Bridges and Human Bridge without occlusal rest and Human Bridge with occlusal rest. By using universal test machine, the numerical maximum value were recorded during the vertical load test of each FPDs after the bonding process treated by Maxcem which is resin cement. The failure process and its result of prosthesis were also observed. The maximum load was 7,295 N, 4,729 N, 2,190 N, 3,073 N from groups of resin bonded FPD, Two Key Bridge, Human Bridge without occlusal rest and Human Bridge with occlusal rest respectively. There was a statistical significance among the groups of resin bonded FPD, Two Key Bridge and Human Brides. However, there was no significant difference between Human Bridge without occlusal rest and Human Bridge with occlusal rest. Regarding the failure of prosthesis, the groups of Resin Bonded FPD and Two Key Bridge showed that one of the abutment teeth in the both side of retention part was highly failed earlier than the other one (83.2% and 66.6% respectively). While, Human Bridge without occlusal rest and Human Bridge with occlusal rest showed high percentage of failure in the abutment teeth in the both side of retention part at the same time (91.6% and 58.3% respectively). This study demonstrates that the group of Human Bridges has low resistance to the vertical loads of low invasive FPDs in comparison with the groups of resin bonded FPD and Two Key Bridge. Nevertheless, the maximum occlusal load of the restorative position, resistance to diverse restoration failure, amount of tooth reduction and patients' cooperation should be considered when they are applied in the clinic in order to choose an appropriate restoration for each patient.

• Journal of Oral Medicine and Pain
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• v.8 no.1
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• pp.43-60
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• 1983

In order to obtain the basic data for diagnosis of occlusion the author investigated the occlusal sounds produced by mandibular closing movement from rest position to centric occlusion by using the Korotkoff sounds microphone electrodes and physiograph for Korean 20S without TMJ problems. And the author analyzed the correlation of the occlusal sounds with height, body weight, mandibular closing movement distance, maxillary sinus size and masseter muscle activities relating to the production of occlusal sounds. The obtained results were as follows : 1. The occlusal sounds prouduced by mandibular closing movements from rest position to centric occlusion were ranged from 3.08mV to 52.00mV, their maen value 19.07mV in right side, and ranged from 2.41mV to 18.33mV, their mean value 9.19mV in left side in group of Angel's class I occlusion subjects having right habitual side of mastication. 2. In general the occlusal sounds in the habitual side of mastication were greater than those in the opposite side. 3. The correlations of the occlusal sounds with height and maxillary sinus size were not significant. 4. The correaltions of the occlusal sounds with body weight, mandibular closing movement distance and masster muscle activities were significant.

• Journal of Oral Medicine and Pain
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• v.14 no.1
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• pp.67-80
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• 1989

The author studied the changes of muscle activity with Bioelectric processor Model EM2(Myotronics Corp., USA) before and after occlusal stabilization splint therapy. For this study, 15 temporomandibular disorders patients and 15 students without any temporomandibular disorders symptoms were selected, for experimental group and control group, respectively. Experimental group were treated with occlusal stabilization splint and checked about electromyographic activity before and after therapy. Electromyographic levels were measured in both groups at the following mandibular position, i.e., physiologic rest, tapping, light biting, hard open without pain, open with pain, right excursion and ipsilateral biting, left excursion and ipsilateral biting, protrusion, protrusive biting, edge biting and physiologic rest after movement. The obtained results were as follows : 1. In experimental group, post-treatment mean values of muscle activity were lower than pretreatment values. 2. In general, the pre-treatment mean values of muscle activity in experimental group were higher than those of control group. 3. In experimental group, no statistically significant difference appeared between affected and unaffected side. 4. The mean value of muscle activity in physiologic rest position after each movement check was lower than that before each movement check.

• Journal of Oral Medicine and Pain
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• v.21 no.1
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• pp.55-65
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• 1996

This study was performed to investigate the effects of head posture and occlusal splint on the vertical dimension in mandibular rest position and swallowing. Thirty health dental students ware selected lot this study and BioEGNⓡ(Bioresearch Inc., USA) was used for measuring interocclusal distance during rest - swallowing - rest - tapping movement. This swallowing movements were observed in both normal head posture(NHP) and forward head posture (FHP). Thickness of occlusal splint was about 2mm at posterior molar area and even tooth contact were achieved on light biting. The four mandibular positions at which interocclusal distance measured were swallowing position, after swallowing position in which interocclusal distance was maximum, rest position follows swallowing, and tapping position after rest. Changes of distance in each position were measured for three mandibular planes, that is, sagittal, frontal, and horizontal plane, respectively. The results obtained were as follows : 1. In normal head posture, the mandible was raised 1.03mm without splint, and 0.77mm with splint on swallowing, and there was no significant difference between the two. In horizontal plane, however, mandible was displaced more anteriorly in both swallowing position and tapping position with splint. 2. In forward head posture, the mandible was less raised with splint on swallowing, but features in horizontal plane were almost same as those in normal head posture. 3. In natural dentition, significant difference between NHP and FHP were observed in horizontal plane trajectory for swallowing and tapping position. But the difference for same positions were observed in frontal trajectory with splint. 4. Total amount of mandibular movement of two groups classified with sagittal interocclusal distance of swallowing position generally showed significant difference between the higher and the lower height group in head posture without splint. 5. Correlationship among total amount of mandibular movement for three mandibular planes were observed between sagittal plane and horizontal plane, and between sagittal plane and frontal plane in head posture without splint.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.731-752
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• 1995

This study was performed to research the changes of masticatory system subsequent to randomly increasing the vertical dimension. The subjects were twenty seven persons, twenty two men and five women, with a mean age of 24.3(age ranged from 22 to 26). The subjects had a complete or almost complete set of natural teeth and reported no subjected symptoms of pain or dysfunction in the masticatory system. The occlusal splint increased vertical dimension was made on semiadjustable articulator. The subjects were randomly divided to three groups according to the vertical dimension, at which the occlusal splint was made. Group I occlusal splints were made at 2mm form the occlusal vertical dimension, group II occlusal splints at 5mm, group III occlusal splints at 8mm. The occlusal splints were almost weared for 2 weeks except meal-time. Clinical examination, muscle activity, changes of free-way space, movement of mandible and articular condyle were recorded and analyzed by means of biopak system(Bioresearch Inc, Millwakee Wisconsin.) and radiograph. 1. In clinical examination, various symptoms were reported by all subjects immediately after the placement of occlusal splint. At the end of experiment, symptoms were lasted by 1 subject in Group I, 2 subjects in Group II, 6 subjects in Group III. At the other subjects, the most of symptoms were disappered within 2-4 days after the placement of occlusal splints. 2. The average free-way space before the startof experiment was 1.77mm in all twenty seven subjects. Immediately after the placement of occlusal splints, 0.67mm at Group I, 0.49mm at Group II, 0.41mm at Group III, At 2 weeks after the placement of occlusal splint 0.93mm, 0.79mm, 0.78mm each other, 1.94mm, 1.77mm, 2.3 mm at immediately after the removal of occlual splint. At 1 week after the removal of occlusal splint, free-way space was recovered to the pre-experimental state 3. In cephalometric radiograph, following either the placement or the removal of the occlusal splints, the movements of mandible in an antero-posterior direction were not statistically significant(p>0.05). 4. In transcranial radiograghs of TMJ, 1 week after the placement of occlusal splint the movement of most superior position on condyle in all group shoed antero-inferior position than before the experiment(p<0.001) and also showed antero-inferior position in mandibular postural rest position than in certric occlusion(p<0.001). Following either the placement or the removal of the splints, the amount of movement of most superior position on condyle was group III. group II and group I in order(p<0.001). 5. In anterior temporal and superficial masseter muscle, muscle activity at postural rest position decreased at 2 weeks after the placement of occlusal splint in group I and group II (p>0.05), but significantly increased in group III(p<0.001). At 1 week after the removal of the occdusal splint, muscle activity at postural rest position was recovered preconditional state 6. In anterior temporal and superficail masseter muscle, muscle activity at clenching in all group was significantly decreased after placement of the occlusal splint, slightly increased during experimental period and recovered to the original state at 1 week after removal of the occlusal splint. But was not statistically significat(p>0.05)s.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.1
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• pp.49-55
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• 2003

When treating the occlusion the dentist must ensure that patients do not develop an occlusal awareness or neurosis after therapy. This means that after treatment patients should not be conscious of the dentition at rest, in occlusion, or during function. Butactually this goal is not easy to reach in daily practice. The dental technician works with rigid casts and dies that do not move. The dentist must use fixed prostheses that have been made in a laboratory setting in a clinical environment that is significantly different. In this article relativey easy cast adjustment technique which can decrease the time necessary to clinically adjust the occlusion of newly fabricated fixed prostheses, and actual occlusal equilibration technique for natural and restored dentition will be discussed.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.718-730
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• 1995

This study was performed to measure the mandibular movement and the changes of masicatory and sternocleidomastoid muscle activity reflected by occlusal disturbance during habitual chewing. For this study, 18 subjects(14 males and 4 females with an average age of 24.0) were selected. The impression of each subject were taken for measuring intermolar distance on lower dentition. The activities of masticatory and sternocleidomastoid muscle and the mandibular movement were recorded and analyzed during habitual chewing by means of E.M.G.(electromyograph), E.G.N.(electrognathograph), rotate program in BioPak analyzing system(BioResearch Inc.). The results were as follows : 1. In EMG of the mandibular rest position, the mean value of muscle activites were increased by nocleidomastoid muscle and anterior belly of digastric muscle(0.05

• 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.

• The Journal of Korean Academy of Prosthodontics
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• v.22 no.1
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• pp.85-94
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• 1984

The purpose of this study was to investigate treatment effectiveness of TENS and bite plane for bruxism and TMJ dysfunction patients. The electromyograms were made on males aged 23 to 25 with sound stomatognathic system, 5 males bruxism aged 24 to 27, and 1 male and 4 females TMJ dysfunction patients (right TMJ pain) aged 14 to 33. The electromyographic study was limited to the middle of masseter muscle and anterior temporal muscle. The electromyographic study was carried out with 8-channel EM2 (Myotronics Research Inc.) and was taken 5 mandibular positions of clinical rest position, clench intercuspal position, clench protruded, cluch right, clench left. The 2 pairs of surface electrodes were used exactly, with the ear lobe as reference point. The recording were subjected to determine the mean voltage. The results were as follows; 1. In the clinical rest position, the muscle activities of bruxism and TMJ dysfunction patients were higher than those of normal at the before treatment, but that were lower or similar to those of normal at the TENS after and after bite plane wearing. 2. In the clench I.C.P., the muscle activities of TMJ dysfunction patients were decreased as the order of the before treatment, after TENS, after occlusal bite plane wearing, but those of bruxism were irregular. 3. In the clench right and the clench left, the muscle activities of the middle of masseter muscle of the non-working side of bruxism were higher than those of the working side at the before treatment and after TENS, but the muscle activities of after occlusal bite plane wearing were similar to those of the normal. 4. In the clench right and the clench left, the muscle activities of the middle of masseter muscle and anterior temporal muscle of the working side of TMJ dysfunction patients were higher than those of non-working side as like the normal at the before treatment, after TENS, and after occlusal bite plane wearing.