• The Journal of Advanced Prosthodontics
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• v.13 no.2
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• pp.79-88
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• 2021

Purpose. To assess peri-implant stress distribution using finite element analysis in implant supported fixed partial denture with occlusal schemes of cuspally loaded occlusion and implant protected occlusion. Materials and methods. A 3-D finite element model of mandible with D2 bone with partially edentulism with unilateral distal extension was made. Two Ti alloy identical implants with 4.2 mm diameter and 10 mm length were placed in the mandibular second premolar and the mandibular second molar region and prosthesis was given with the mandibular first molar pontic. Vertical load of 100 N and and oblique load of 70 N was applied on occlusal surface of prosthesis. Group 1 was cuspally loaded occlusion with total 8 contact points and Group 2 was implant protected occlusion with 3 contact points. Results. In Group 1 for vertical load, maximum stress was generated over implant having 14.3552 Mpa. While for oblique load, overall stress generated was 28.0732 Mpa. In Group 2 for vertical load, maximum stress was generated over crown and overall stress was 16.7682 Mpa. But for oblique load, crown stress and overall stress was maximum 22.7561 Mpa. When Group 1 is compared to Group 2, harmful oblique load caused maximum overall stress 28.0732 Mpa in Group 1. Conclusion. In Group 1, vertical load generated high implant stress, and oblique load generated high overall stresses, cortical stresses and crown stresses compared to vertical load. In Group 2, oblique load generated more overall stresses, cortical stresses, and crown stresses compared to vertical load. Implant protected occlusion generated lesser harmful oblique implant, crown, bone and overall stresses compared to cuspally loaded occlusion.

• Journal of Dental Rehabilitation and Applied Science
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• v.39 no.3
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• pp.119-132
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• 2023

The loss of posterior occlusal support due to tooth loss is likely to lead to compensatory protrusion and labial tilt of the anterior teeth, which may be accompanied by a deep bite and a decrease in vertical dimension. The patient may suffer from a decrease in masticatory efficiency, inaccurate pronunciation, facial appearance changes, and temporomandibular joint disorder, so stable occlusal formation with support of posterior occlusion and restoration of vertical dimension is necessary. We report the case of a patient with reduction of vertical dimension, and inaccurate pronunciation due to multiple tooth loss who underwent full mouth rehabilitation with increased vertical dimension accompanied by phonetic analysis and achieved satisfactory functional and aesthetic results.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.182-190
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• 2009

Statement of problem: Microleakage at the occlusal and gingival margin of Class V cavities restored with composite resin has traditionally been considered an obstacle to successful restoration. Purpose: The aim of this study was to assess the effectiveness of three different surface sealants(Fortify, Permaseal and Biscover LV) on the marginal sealing of Class V light-activated composite resin restorations(Z250). Material and methods: Forty noncarious human premolars and molars extracted within a three-month period were selected. Class V cavities with the occlusal margin in enamel and gingival margin in cementum were prepared in both buccal and lingual surfaces. The teeth, randomly assigned in four groups with twenty cavities in each group, were restored with composite resin after applying an adhesive system(Clearfil SE bond). After the finishing and polishing procedures, the restorations were covered with a specific surface sealants, except for the control samples, which were not sealed. After placing restorations, the specimens were thermocycled, and immersed in a 2% methylene blue solution for twenty four hours and sectioned longitudinally. The marginal microleakage was evaluated at the occlusal and gingival interfaces using a microscope and compared among the four groups using ANOVA test and Wilcoxon Rank-Sum test($\alpha$=0.05). Results: Statistical analysis showed that there was significantly less leakage when the surface sealants were used than there was in control group(P<.05). There were no significant differences of microleakage at occlusal and gingival margins among groups. There were no significant differences between microleakage of occlusal and gingival margins in each group. Fortify was not statistically different from control group at the gingival margin(P>.05). Conclusion: Application of surface sealants was an effective method of surface coating in reducing microleakage at occlusal and gingival margins of Class V composite resin restorations. However, it is certain that some microleakage still occurred despite the application of surface sealants, especially gingival margins.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.257-268
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• 2003

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis according to position and direction of load, under vertical and inclined loading using FEA analysis. The finite element model was designed according to standard fixture (4.1mm restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric usp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant in both vertical and oblique loading but stresses in the cancellous bone were low in both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. 4. The relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 5. The magnitude of the stress in the supporting bone, fixture and abutment screw was greater with the outward oblique loading than with the inward oblique loading and was the greatest under loading at the centric cusp in a $30^{\circ}$ outward oblique direction. Conclusively, this study provides evidence that bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. But it seems to be more important that how long is the distance from center of rotation of the implant itself to the resultant line of force from occlusal contact(leverage). The goal of improving implants should be to avoid bending of the implant.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• The korean journal of orthodontics
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• v.34 no.5 s.106
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• pp.380-393
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• 2004

The Purpose of this study was to investigate the dentoalveolar compensation according to anteroposterior skeletal discrepancy in normal occlusion and to evaluate cephalometric parameters that quantitatively describe dental compensations. The study consisted of 90 subjects (50 males. 40 females) who were selected among specimens of normal occlusion at Seoul National, University Dental Hospital, Dept. of Orthodontics. Lateral cephalograms in centric occlusion were traced and digitized for each subject. According to the anteroposterior skeletal pattern the sample was divided into three groups. Cephalometric data were analyzed for the three groups using the SPSS program. Independent t-test, correlation analysis and regression analysis were carried out. The results were as fellows: Dentoalveolar compensation was found in upper and lower incisor inclination and occlusal plane inclination. As the mandible located anterior to the maxilla, the maxillary incisors incisors more labially. the mandibular incisors more lingually, and the occlusal plane continued to flatten. The dental parameters most correlated with anteroposterior skeletal discrepancy were L1 to SN and L1 to FH. Among the compensatory dentoalveolar changes, lower incisor inclination was strongly related to the anteroposterior jaw relationship and played au imposrtant role in obtaining a normal incisor relationship U1 to PtGn and L1 to APog were constant irrelevant to anteroposterior skeletal discrepancy.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.1
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• pp.33-43
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• 2023

Pathological wear across the entire dentition causes problems such as collapsed occlusal plane, reduced vertical dimension, anterior premature contact, inadequate anterior guidance, and tooth migration, thereby induce symptoms such as temporomandibular joint disorder, reduced masticatory efficiency, and tooth hypersensitivity. For the treatment of patients with excessive wear, evaluation of vertical dimension should be preceded along with analysis of the cause. The patient in this case was a 45-year-old female with a history of orthognathic surgery. Through clinical examination, radiographic examination, and model analysis, overall tooth wear, interdental spacing in the anterior maxillary region, retruded condylar position, and insufficient interocclusal space for prosthetic restoration were confirmed. Full mouth rehabilitation with increased vertical dimension was planned, the patient's adaptation to the new vertical dimension was evaluated with a removable occlusal splint and temporary prosthesis, and cross-mounting was performed based on the temporary restoration to fabricate the definitive zirconia prosthesis, maintaining the adjusted vertical dimension. It showed satisfactory functional and esthetic results through stable restoration of the occlusal relationship.

• Journal of Korean Dental Science
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• v.16 no.2
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• pp.128-148
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• 2023

Dementia is an umbrella term that describes the loss of thinking, memory, attention, logical reasoning, and other mental abilities to the extent that it interferes with the activities of daily living. More than 50 million individuals worldwide live with dementia, which is expected to increase to 131 million by 2050. Recent research has shown that poor oral health increases the risk of dementia, while oral health declines with cognitive decline. In this narrative review, the literature was based on the "hypothesis" that dementia and oral health have a close relationship, and appropriate oral health and occlusal rehabilitation treatment can improve the quality of life of patients with dementia and prevent progression. We conducted a literature search in PubMed and Google Scholar databases, using the search terms "dementia," "major neurocognitive disorder," "dentition," "occlusion," "tooth loss," "dental prosthesis," "dental implant," and "occlusal rehabilitation" in the title field over the past 30 years. A total of 131 studies that scientifically addressed dementia, oral health, and/or oral rehabilitation were included. In a meta-analysis, the random effect model demonstrated significant tooth loss increasing the dementia risk 3.64-fold (pooled odds ratio=3.64, 95% confidence interval [2.50~5.32], P-value=0.0348). Tooth loss can be an important indicator of cognitive function decline. As the number of missing teeth increases, the risk of dementia increases. Loss of teeth can lead to a decrease in the ascending information to the brain and reduced masticatory ability, cerebral blood flow, and psychological atrophy. Oral microbiome dysbiosis and migration of key bacterial species to the brain can also cause dementia. Additionally, inflammation in the oral cavity affects the inflammatory response of the brain and the complete body. Conversely, proper oral hygiene management, the placement of dental implants or prostheses to replace lost teeth, and the restoration of masticatory function can inhibit symptom progression in patients with dementia. Therefore, improving oral health can prevent dementia progression and improve the quality of life of patients.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.2
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• pp.162-167
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• 2010

This is a case report about patient who had suffered from degenerative joint disease and treated by TMJ reconstruction with condylar prosthesis. The patient visited Korea University An-am hospital on 2007 complaining symptom about both TMJ pain, mouth opening limitation and open bite. From CT view there was severe resorption of both condylar head, therefore condylar prosthesis reconstruction was planned. After 3D RP model analysis for preparation, the patient was operated under general anesthesia for condylar prosthesis reconstruction and the symptom was alleviated. (increased mouth opening, reduced anterior open bite, full mouth occlusal contact achieved) Follow up was carried out monthly, but after this, patient refused follow up. After 26 months from the operation, the patient revisited for anterior open bite. In clinical evaluation, occlusal contact was remained, but anterior open bite was relapsed. From cephalometry analysis, severe resorption of glenoid fossa was found. Therefore, Autogenous disc reconstruction with alloplastic material was planned on August 2009. After another surgery, condylar prosthesis was regained its normal position in glenoid fossa, and occlusion was recovered properly.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.321-329
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• 2002

Bending moments results from offset overloading of dental implant, which may cause stress concentrations to exceed the physiological capacity of cortical bone and lead to various kinds of mechanical failures. The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different angulated placement of dental implant in mandibular posterior missing areas. The three kinds of finite element model, were designed according to 3 main configurations: Model 1(parallel typed placement of 2 fixtures), Model 2(15. distal angulated placement of one fixture on second molar area), Model 3(15. mesial angulated placement of one fixture on second molar area). The cemented crowns for mandibular first and second molars were made on the two fixtures (4mm 11.5). Three-dimensional finite element models by two fixtures were constructed with the components of the implant and surrounding bone. A 200N vertical static load were applied to the center of central fossa and the point 2mm apart from the center of central fossa on each model. The preprocessing, solving and postprocessing procedures were done by using FEM analysis software NISA/DISPLAY IV Version 10.0((Engineering Mechanics Research Corporation, USA). Von Mises stresses were evaluated and compared in the supporting bone, fixtures, and abutment. The results were as following : (1) Under the point loading at the central fossa, the direction of angulated fixture affected the stress pattern of implants. (2) Under the offset loading, the position of loading affected more on the stress concentration of implants compare to the angulated direction of implants. The results had a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the placement angulation of implant fixture is placed toward mesial or distal direction. In designing of the occlusal scheme for angulated placement, placing the occlusal contacts axially during chewing appears to have advantages in a biomechanical viewpoint.