• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.434-442
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• 2017

The purpose of this study was to examine the influence of type of malocclusion and orthodontic treatment awareness on quality of life among orthodontic patients in the region of Busan as well as to develop an educational program tailored to the type of malocclusion as a way to improve quality of life. A survey was conducted for approximately 6 months from December, 2015, and the answer sheets from 472 respondents were analyzed. The most common painful area was the teeth, and this case was most predominant in the respondents with level 2 malocclusion, who differed from others in that regard (p<0.001). Regarding the relationship between satisfaction with orthodontic treatment and quality of life, respondents who were more satisfied currently and who were neither quite confident nor quite unconfident were ahead of their counterparts in quality of life. Concerning the reason for receiving orthodontic treatment, quality of life was lower among patients who started to receive treatment due to pronunciation problems (p=0.013), chewing difficulty (p<0.001), and temporomandibular joint click sound (p<0.001). With regard to influential factors on oral health-related quality of life, time for starting to receive orthodontic treatment was most influential (p<0.001), followed by current satisfaction (p<0.001), changes in confidence (p=0.003), self-rated teeth status (p=0.008), and type of occlusion (p=0.019). Therefore, accurate analysis of the oral health status of orthodontic patients and customized oral health education are required to improve quality of life even during the period of orthodontic treatment.

• Journal of Technologic Dentistry
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• v.42 no.2
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• pp.139-145
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• 2020

Purpose: This study is for the prosthesis of dog. Observed the occlusal relation between the small dog canine and carnassial teeth. The direction of the bite force was analyzed by 3D FEM(finite element method). Methods: The mandibular canine and carnassial of dog were tested. The skull of dog was contact point confirmed by dental CAD. The skull of dog was scaned using CT and a 3D model was created. The 3D model was analyzed ABAQUS. Closing movement has been 100N, 200N, 300N, 500N, 1000N, 1500N. The Direction of bite force was confirmed. Results: As occlusal force increased, the direction of bite force appeared to (-y), (-x,-y,-z), (-x,-y), (-x,-y,+z), (-x,-y,+ z), (+x,-y) in mandibular left canine. And the direction was seen at (+x, -y), (+x,-y,-z), (+x,-y), (-x,-y,+z), (-x,-y,+z), (+x,-y). When the occlusal load is 100 N, 200 N, 300 N, 500 N, the direction of the mandibular carnassial appears as (-x, -y, -z), and when the occlusal load is 1000 N, 1500 N, the direction appears as (-x,-y). Conclusion: The mandibular canine showed irregularities in the coordinates of the direction of the bite force, and the mandibular carnassial showed regularity in the coordinates of the direction of the bite force.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.8-19
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• 2009

The purpose of this study was to investigate the effects of four restorative materials under various occlusal loading conditions on the stress distribution at the CEJ of buccal. palatal surface and central groove of occlusal surface of endodontically treated maxillary second premolar, using a 3D finte element analysis. A 3D finite element model of human maxillary second premolar was endodontically treated. After endodontic treatment, access cavity was filled with Amalgam, resin, ceramic or gold of different mechanical properties. A static 500N forces were applied at the buccal (Load-1) and palatal cusp (Load-2) and a static 170N forces were applied at the mesial marginal ridge and palatal cusp simultaneously as centric occlusion (Load-3). Under 3-type Loading condition, the value of tensile stress was analyzed after 4-type restoration at the CEJ of buccal and palatal surface and central groove of occlusal surface Excessive high tensile stresses were observed along the palatal CEJ in Load-1 case and buccal CEJ in Load-2 in all of the restorations. There was no difference in magnitude of stress in relation to the type of restorations. Heavy tensile stress concentrations were observed around the loading point and along the central groove of occlusal surface in all of the restorations. There was slight difference in magnitude of stress between different types of restorations. High tensile stress concentrations around the loading points were observed and there was no difference in magnitude of stress between different types of restorations in Load-3.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.3
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• pp.472-480
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• 2005

The purpose of this study was to investigate the effective penetration methods of acid etching agents in the pit and fissures on the occlusal surface. Extracted maxillary first and second premolars were divided into 4 groups : to Group I only acid etching agent was applied, to Group II ultrasonic scaler as well as acid etching agent were applied, to Group III after fissurotomy acid etching agent was applied, and to Group IV after fissurotomy the same process performed with Group II. The comparison between the 4 groups by the use of scanning electron microscope showed the results as follows : 1. Comparing each groups with regard to the penetration rate(%) of acid etching agents, Group III and Group IV showed improved penetration rate(%) compared with Group I. Group II made no significant different results from Group I, but had somewhat better penetration rate(%). 2. Comparing each groups with regard to the penetration rate(%) of acid etching agents according to regions within fissures, Group III and Group IV showed more improved penetration rate than Group I in the mesial pit and distal pit. However, no significant difference between each groups was showed in the middle fissure.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.1-12
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• 2009

The objective of this study was to test the effects of crown material, cement type, the direction in which stress is applied and distribution of luting cement that might lead to cement microfracture using 2D Finite Element Method. Twenty three finite element models with a chamfer margin configuration were generated for a mandibular first molar. Crown models exhibited four crown materials: type 3 gold alloy, Ni-Cr alloy, ceramic and composite resin, and two luting cements: zinc phosphate and glass ionomer cements with a thicknesses of $70{\mu}m$. Modeled crowns were loaded axially or obliquely at unit load of 1 N. Areas and levels of stress concentrations within the cement were determined. Stress in the cement layer at the margins of crowns were higher than those in the area away from the margin. Stress under oblique loads were much higher than under axial load. The stiffer crown material produced higher stress and similarly, higher stress were found in cements with the greater Young's modulus.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.1
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• pp.51-61
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• 2011

Recently, restoring implants in the esthetically demanding region, zirconia-based materials are widely used due to their superior mechanical properties, accuracies, and esthetics. The purpose of this study was to investigate the load transfer and mechanical stability of zirconia and titanium implant abutments by using the three-dimensional finite element analysis model. The internal conical joint type and external butt joint type implant system was selected as an experimental model. Finite element models of bone/implant/prosthesis complex were constructed. An load of 250N was applied vertically beside 3mm of implant axis. Stress distribution of zirconia and titanium implant abutment is similar. The maximum equivalent stress of titanium implant abutment is lower than zirconia implant abutment about 15%. Howevere considering a high mechanical strength that exceed those of titanium implant abutment, zirconia implant abutment had similar mechanical stability of titanium implant abutment clinically.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.2
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• pp.119-124
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• 2013

Many of the patients with extensive abrasion need comprehensive restorative treatment. The abrasion is usually caused by attrition, besides of it, there are many reasons for it. The plan of treatment should be started on assessment of the type of attrition and the etiologic analysis. Patient with well-developed masticatory muscle, alveolar process, and high occlusal force and also with little muscle length difference between the stable and the contracted state should be carefully assessed for the vertical dimensional loss and the restoration should be carefully designed. Decrease of tooth length can be compensated by the growth of the alveolar bone height; therefore, consistency of the occlusal vertical dimension is maintained. Accordingly, a careless increase of the vertical dimension can produce muscle fatigue, depressed tooth and pain, and fracture of the restoration. In this case, the patient with multiple tooth abrasion and clenching habit, the edentulous maxillary area is restored with amalgam inserted RPD, and the dentulous area of the maxilla and mandible are treated with fixed restoration accompanying with the increase of vertical dimension. Consequently, we are going to report about the satisfying result in both functional and esthetic aspects.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.2
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• pp.173-182
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• 2019

Vertical facial growth triggers the rotation of mandible to move the chin point to the downward and backward direction, which showed remarkably effective result making the less prominent chin. Recently, the intraoral removable appliance utilizing class III elastic demonstrated the vertical growth trigger mechanism. The treatment change was very fast and wearing was quite easy, compared to extraoral appliances. The purpose of this study was to verify the duration of the treatment on class III malocclusion using intraoral removable appliances, which designed to accelerate vertical facial growth. 56 patients were selected with the complaint of the protruded mandible and class III malocclusion (overjet : -3 - 0 mm, overbite : 0 - 4 mm). Information like; age at start, duration of the treatment events, type of the treatment, overjet, overbite etc. was collected and calculated. The average age of the patients delivering the initial brace was $8.75{\pm}1.10year$. Most of the anterior crossbite was resolved within 6 months. The total treatment period was $21.79{\pm}10.73months$ with the additional procedures like the alignment of anterior teeth and torque control using additional removable and fixed orthodontic appliances. The correlation study showed that patient's cooperation (p = 0.000) and the use of fixed appliance (p = 0.032) were significantly influenced on treatment duration.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.2
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• pp.127-138
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• 2012

This study is to assess the effect of preload level on the stress development at the marginal cortical bone surrounding implant neck. A finite element model was created for a single implant placed in the lower jaw bone. An external load of 100N was applied on the top of abutment at 30 degree with the implant axis in lingo-buccal direction. Five different preloads, i.e. 0, 200, 400, 600, 800N were applied to the abutment stem to investigate if and/or how the preload affects on the marginal bone stress. Differences in the marginal bone stress were recorded depending on the level of preload. On the other hand, the tensile stress on the marginal cortical bone decreased in models of higher preload. Preloads between abutment/fixture can increase compressive stresses in the marginal cortical bone although the amount may be insignificant as compared to those generated by functional forces.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.18-27
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• 2009

Objective: The purpose of this study was to understand the differences in masseter muscle(MM) between the shifted and non-shifted sides in facial asymmetry patients, and the changes shown by MM after mandibular surgery. Methods: Pre- and post-operative CT scans were performed on 12 Class III patients with facial asymmetry who were treated by intraoral vertical ramus osteotomy and 10 subjects with normal occlusion. Using the V-works 4.0 program(Cybermed, Seoul, Korea), 3-dimensional images of the mandible, and MM were reconstructed, and evaluated. Results: In the asymmetry group, the MM angle between the shifted and non-shifted sides was only significantly different(p<0.05). Compared with normal occlusion, the asymmetry group showed a significantly smaller volume and maximum cross-sectional area in both sides of MM(p<0.05). After mandibular surgery, the angle of MM(p<0.01) and differences in angle between the shifted and non-shifted sides of MM(p<0.05) were significantly decreased. The thickness in the maximum cross-sectional area was significantly increased(p<0.01). After surgery, MM in facial asymmetry patients was similarly changed to those in the normal occlusion group except for widths. Conclusions: MM in facial asymmetry was definitely different from those in normal occlusion. However, this study suggests that MM changed symmetrically in conjunction with the mandible after proper mandibular surgery.