• The Journal of Advanced Prosthodontics
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• v.16 no.4
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• pp.221-230
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• 2024

PURPOSE. This in vitro study was conducted to investigate the accuracy of intraoral scanner (IOS) for recording maximal intercuspal position (MIP) and border positions of the mandible. MATERIALS AND METHODS. Maxillary and mandibular master casts were articulated in MIP, protrusive, and lateral interocclusal position sequentially on a semi-adjustable articulator. For each articulation relation, sites of occlusal contacts (SOCs) and sites of clearance (SCs) were identified on the master casts with articulating paper (reference sites). IOS was used to take full arch scans and nine virtual interocclusal records (VIRs) for virtual articulation of models. Virtual SOCs and SCs were detected with 3D processing software and compared to those identified with the articulating paper. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each articulation relation. RESULTS. For MIP, IOS showed adequate sensitivity and NPV of 100%, and specificity and a PPV of 99%. For protrusive position, the IOS showed a sensitivity and a NPV of 100%, a high PPV of 86%, and a specificity of 83%. For lateral positions, the specificity and the PPV were high (93% and 79%, respectively), but the sensitivity and the NPV were below the clinically acceptable limits (28% and 56%, respectively). CONCLUSION. IOS displayed clinically acceptable accuracy for recording MIP and protrusive border mandibular position. However, IOS had less accuracy for lateral border mandibular position.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.199-207
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• 2013

Purpose: The importance of occlusal contacts of the natural dentition for durability of teeth, mandibular stabilization, and restorative dentistry is well known. The purpose of this study is to analyze the occlusal contact and guidance pattern of Koreans by evaluating the static occlusion on maximal intercuspal position and measuring dynamic occlusion during straight protrusion. Materials and methods: The occlusal contacts at maximal interincisal position and the occlusal guidance pattern during straight protrusion of 29 subjects were recorded with shimstock foil (Whaledent, Langenau, Germany), T-Scan III (Tekscan Inc., Boston, MA, USA), polyvinylsiloxane registration material (Genie Bite, Sultan Healthcare, Hackensack, NJ, USA) and compared. Occlusal registration procedures were repeated 3 times. The position was fixed to an upright position and the head position was fixed with the Frankfurt horizontal plane paralleling the horizontal plane. Fisher's Exact Test (R-General Public License, ver. 2.14.1) and Pearson's Test were used to assess the significance level of the differences between the experimental groups (${\alpha}=.05$). Results: When using shimstock foil, T-Scan III system, and polyvinylsiloxane registration material, most of the patients showed contact on anterior, premolar, and molar teeth during maximal intercuspal position. Approximately 51% of maximal intercuspal position showed anterior contact using shimstock foil. When examining the protrusive movement using shimstock foil and T-Scan III system, guidance pattern with the central incisor was the most common. Conclusion: During maximal intercuspal position, there were cases in which not all of the teeth showed occlusal contact. During mandibular protrusive movements, one or more maxillary central incisors frequently joined in straight protrusion and the posterior teeth were disoccluded. Therefore, the anterior teeth protect the posterior teeth, and vice versa. Thus, mutually protected occlusion should be applied when reconstructing occlusion.

• Journal of Oral Medicine and Pain
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• v.20 no.1
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• pp.195-204
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• 1995

The purpose of this study was to evaluate effect of head posture change on initial occlusal contacts through measuring the distances between initial occlusal contacts and maximum intercuspal position at different head posture. Two special devices were designed and constructed. Mandibular movement replicator was used to assess reliability of the K6 diagnostic system(MKG; Myo-tronic Inc, Seatle, USA) and head posture calibrator was used to maintain the constant head posture during experiment. We measured difference of distance between initial occlusal contact and maximum intercuspal position with MKG in upright, supine, 45 degrees extension, 30 degrees flexion, 30 degrees right and left bending postion of the head. The Frankfurt horizontal plane was used as a reference plane. 21 adults aged from 23 to 25 were selected, who have normal or class I molar relationship, and have no symptoms on TMJ and masticatory muscles, and have restorations less than 3 surfaces on each tooth, and have no other prosthetic restoration. The obtained results were as follows : The mean absolute distances between initial occlusal contact and maximum intercuspal postion were 0.39(0.18mm in the upright position, 0.65(0.37mm in the supine position, 0.59(0.33mm in the 45 degree extension, 0.70(0.53mm in the 30 degrees flexion, 1.12(1.10mm in the 30 degrees right bending and 1.94(0.67mm in the 30 degrees left bending of the head. The positions of the initial occlusal contacts have a tendency to locate anterior, left and inferior to maximal intercuspal position in upright position, posterior and inferior in supine position and 45 degrees extension, anterior and inferior in 30 degrees flexion, right and inferior in 30 degrees right bending, and left and inferior in 30 degrees left bending of the head. There were significant differences among the initial occlusal contacts in each head postures(P<0.0001). Therefore, we need to check initial occlusal contacts in the altered head posture during occlusal analysis and adjustment of occlusal appliance and dental occlusion for diagnosis and treatment of temporomandibular disorder.

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.489-496
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• 1995

The purpose of this study was to evaluate an effect of change on head posture initial occlusal contacts with measuring the distances between initial occlusal contacts and maximum intercuspal position at different head posture in TMDs patient. For this study, 24 patients from age 13 to 36 were selected, they were examined health history taken, patients who have sign and symptoms of TMDs were examine before the study. For the normal group, 21 adults from age 23 to 25 were selected. They have normal or class I molar relationship, and have no other prosthetic restorations. Difference on distance between initial occlusal contact and maximum intercuspal position with mandibular kinesiograph$(MKG^R)$(K6 diagnostic system, Myo-tronic Inc, USA) in upright, supine, 45$^{\circ}$ extension, 30$^{\circ}$ flexion position of the head were measured. The Frankfort horizontal plane was used as a reference plane. The results were as follows : 1. There were significant differences between initial occlusal contacts of the normal and patient group on upright position and 30$^{\circ}$ flexion of the head(p<0.05, p<0.01) 2. The position of the initial occlusal contacts have a tendency to place anterior and inferior to maximal intercuspal position in upright position and 30( flexion of the head as well as posterior and inferior in supine position and 45$^{\circ}$ extension of the head in the normal and patient groups. 3. There were significant differences among the initial occlusal contacts between uptight and supine position; upright and 45$^{\circ}$ extension of the head(p<0.05); supine position and 30$^{\circ}$ flexion of the head, .and 30(flexion and 45$^{\circ}$ extension of the head in the patient group(p<0.01) The result have shown that after treatment on the supine position, it may be necessary to check occlusal contact on the upright position as well ass flexion of the head. It may need careful adjustment in occlusal condition on upright position of TMDs patient.

• The korean journal of orthodontics
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• v.22 no.1
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• pp.253-271
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• 1992

The purpose of this study was to investigate the difference of EMG activity of the Orbicularis oris and Mentalis muscle between normal occlusion and class III malocclusion group during various lip position and to find out whether any correlations exist between the muscular activity and craniofacial morphology. In this study, 50 subjects with a mean age of 22.9 Years (range 20.0-26.0) were investigated (25 subjects were normal occlusion, and 25 subjects were class III malocclusion). EMG data were recorded from the Orbicularis oris and Mentalis muscle during rest lip posture, lip position at maximum biting, lip position at maximum sealing effort, lip position at chewing, swallowing and phonation with the Medelec MS-25 electromyographic machine. Lateral cephalometric radiographs was taken with the mandible in intercuspal position on all subjects. All data were recorded and statistically processed. The findings of this study can be summerized as follows: 1. In normal occlusion, the maximal mean amplitude of upper lip during the lip position at chewing was lower than that of lower lip and mentalis muscle. But the maximal mean amplitude of orbicularis oris and mentalis muscle during the other lip position was not statistically different. 2. In Class III malocclusion, the maximal mean amplitude of upper lip during the lip position at chewing, swallowing and phonation was lower than that of lower lip and mentalis muscle. But the maximal mean amplitude of orbicularis oris and mentalis muscle during the other lip position was not statistically different. 3. Compare to normal occlusion, the Class III malocclusion was showed low maximal mean amplitude of upper lip during rest lip posture and the lip position at swallowing of saliva, and showed great maximal mean amplitude of lower lip and meantalis muscle during the lip position at chewing and phonation. 4. In normal occlusion, the maximal mean amplitude of upper lip during various lip position was not correlated with the length and thickness of upper lip, but the maximal mean amplitude of lower lip during the lip position at chewing and swallowing was positively correlated with the thickness of lower lip. 5. In Class III malocclusion, the maximal mean amplitude of upper lip during rest lip posture was negatively correlated with the thickness of upper lip, and the maximal mean amplitude of lower lip and mentalis muscle during the lip position at chewing and swallowing was positively correlated with the thickness of lower lip and mentalis muscle. But the maximal mean amplitude of orbicularis oris and mentalis muscle during the other lip position was not correlated with the cephalometric measurements of soft tissue. 6. The correlation between the maximal mean amplitude of orbicularis oris and mentalis muscle and cephalometric measurements of incisors was not nearly present. 7. In normal occlusion, the maximal mean amplitude of lower lip and mentalis muscle during the lip position at maximum biting was negatively correlated with the angle between palatal plane and mandibular plane. In Class III malocclusion, the maximal mean amplitude of upper lip, lower lip and mentalis muscle during function was negatively correlated with the length of maxilla, the maximal mean amplitude of upper lip and lower lip during function was negatively correlated with the SNA and SNPo, and the maximal mean amplitude of lower lip during the lip position at chewing was negatively correlated with the ANB.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.2
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• pp.90-97
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• 2019

Purpose: Previous studies related with occlusal contact area were limited that interocclusal thickness level or the method of measurement has not been accurate in measuring. The purpose of this study was to investigate the relation between head posture and occlusal contact area using photo occlusion analysis. Materials and Methods: 54 subjects with complete dentition (44 men, 10 women / 23 to 33 years of age) were included. To identify the relationship between head posture and occlusal contact area, subjects took interocclusal record in maximal intercuspal position with three different positions(supine position ($0^{\circ}$) / inclined position ($45^{\circ}$) / upright position ($90^{\circ}$)) on the dental unit chair. Occlusal contact area was analyzed using photo occlusion analysis. Statistical analyses were performed with SPSS ver.25.0 at 95% confidence interval. Results: Head posture has no significant effect on the changes of occlusal contact area (P > 0.05). Conclusion: When interocclusal relation is stable, head posture does not change a interocclusal record because head posture has no significant effect on occlusal contact area. Analysis of occlusal contact area using photo occlsion analysis device is useful due to its material property and simplicity.

• The korean journal of orthodontics
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• v.24 no.1 s.44
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• pp.199-220
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• 1994

This study was conducted to determine the electromyographic features in the perioral muscles of class II division 1 malocclusion with incompetent lips, and to grope the correlation between its activities and craniofacial morphology. Tn this study, 14 subjects with class II division 1 malocclusion with incompetent lips(mean age of 20.5 years) and 20 subjects with normal occlusion(mean age of 23.9 years) were investigated. Electromyographic data were recorded from orbicularis oris, mentalis, buccinator and suprahyoid muscles durig rest lip posture, lip position at sealing, maximum sealing, maximal blowing, maximal biting, sipping milk, sipping and swallowing milk, chewing gum, masticating almond, swallowing almond and phonation utilizing the Medelec MS-25 electromyographic apparatus. Lateral cephalometric radiographs were taken with the mandible in intercuspal position on all subjects. All data were recorded statistically processed. The findings of this study can be summerized as follows : 1. In class II division 1 malocclusion with incompetent lips, the overall augmentations of perioral muscle activities during various functionel movements set for lip sealing were manifested and particular swelling in mentalis activity at rest was detected. 2. On the other hand remarkable diminution of upper lip acitivities at lip sealing movements was drawn. 3. In Class II division 1 malocclusion with incompetent lips, negative correlations existed between the diversity of upper lip activities and upper incisor position and overjet as well in contrast to positive correlations in the lower lip. 4. It was suggested that the abnormal function of lower lip and mentalis muscle contributed somewhat the revelation of the characteristics of Class II division 1 malocclusion.

• Journal of Oral Medicine and Pain
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• v.42 no.1
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• pp.16-19
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• 2017

Clinicians are familiar with limitation of opening mouth caused by temporomandibular disorders. Sometimes, patients also complain of difficulty in closing mouth. Difficulty in closing mouth can be caused by anterior, posterior disc displacement, and subluxation of temporomandibular joint (TMJ). In this report, we presented a patient who had a difficulty in both opening and closing mouth. The patient complained of TMJ noises and intermittent limitation of opening mouth, and inability to get teeth back into maximal intercuspal position. Magnetic resonance images revealed that the left TMJ had an anterior disc displacement with relative posterior disc displacement. We reviewed the possible causes, signs and symptoms, and treatment for difficulty in closing mouth with related literatures.

• The Journal of Advanced Prosthodontics
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• v.14 no.6
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• pp.369-378
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• 2022

PURPOSE. The purpose of this in vitro study was to assess whether scanning strategies of virtual interocclusal record (VIR) affect the accuracy of VIR during intraoral scanning. MATERIALS AND METHODS. Five pairs of reference cubes were added to the digital upper and lower dentitions of a volunteer, which were printed into resin casts. Subsequently, the resin casts were articulated in the maximal intercuspal position in a mechanical articulator and scanned with an industrial computed tomography system, of which the VIR was served as a reference VIR. The investigated VIR of the upper and lower jaws of the resin master cast were recorded with an intraoral scanner according to 9 designed scanning strategies. Then, the deviation between the investigated VIRs and reference VIR were analyzed, which were measured by the deviation of the distances of six selected reference points on the upper reference cubes in each digital cast to the XY-plane between the investigated VIRs and reference VIR. RESULTS. For the deviation in the right posterior dentitions, RP group (only scanning of right posterior dentitions) showed the smallest deviation. Besides, BP group (scanning of bilateral posterior dentitions) showed the smallest deviation in the left posterior dentitions. Moreover, LP group (scanning of left posterior dentitions) showed the smallest deviation in the anterior dentitions. For the deviation of full dental arches, BP group showed the smallest deviation. CONCLUSION. Different scanning strategies of VIR can influence the accuracy of alignment of virtual dental casts. Appropriate scanning strategies of VIR should be selected for different regions of interest and edentulous situations.

• Journal of Oral Medicine and Pain
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• v.33 no.3
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• pp.279-294
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• 2008

This study aimed to make an analysis of the occlusion in the state of muscle fatigue produced by excessive mouth opening and clenching during the dental treatment to control the dental pain and to evaluate the sensory nerve in the muscle pain state. Most of the reasons why patients visit the dental office result in pain-either conceivably the dental origin pain or the non-dental origin pain. The dental offices have many therapeutic actions to produce the masticatory muscle fatigue for the treatment. Dental treatment with long minutes of mouth opening can cause some headaches, masticatory muscle pain and mouth opening difficulties. Patients with mastication problems who visits a dental office to alleviate pain run against another unexpected pain with other aspects. This study uses T-scan II system(Tekscan Co., USA) for the evaluation on the occlusal pattern in the experimental muscle fatigue after clenching, opening the mouth excessively and chewing gum. The occlusal contact pattern is analyzed by the contact timing, namely first, intercuspal, maximum and end point of contact. This inspection was performed at frequencies of 2000Hz, 250 Hz and 5 Hz before and after each experimental muscle pain was produced to 24 subjects who had normal occlusion without the orthodontic treatment or a wide range of the prosthesis by using $neurometer^{\circledR}$ CPT/C(Neurotron, Inc. Baltimore, Maryland, USA). The measuring sites were mandibular nerve experimental muscle fatigue respectively. This study could obtain the following results after the assessment of occlusion and sensory nerve of the experimental muscle fatigue. 1. There were the fastest expression after the excessive mouth opening in muscle fatigue and after tooth clenching in muscle pain. In the visual analog scale that records the subjective level, there was the highest scale after the clenching in the muscle fatigue in jumping off the point of pain. 2. Tooth contact time, contact force, relative contact force on the point of the first contact had no difference, and there were decreases in the contact force after the excessive mouth opening on intercuspal position point, after the excessive mouth opening and the gum chewing on the point of the maximum, and in the contact time after all the experimental muscle fatigue state on the point of the end contact. 3. There was no statistic significance in the current perception threshold before and after the experimental muscle fatigue. 4. There was no significant difference in the contact number, the maximal contact number on the point of the first contact, and the contact number after the mouth opening and gum chewing on the point of the intercuspal position and the contact number after the experimental muscle fatigue on the maximum point, and showed significant decreases. In conclusion, it was found that the occlusal pattern can cause the changes on the case of the clinical muscle weakness by intra-external oral events. It was important that the sedulous attention to details is required during dental treatment in case of excessive mouth opening, mastication and clenching.