• Journal of dental hygiene science
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• v.23 no.4
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• pp.378-388
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• 2023

Background: With increasing interest in health in old age, aspects of oral aging are being considered. The Korean Academy of Geriatric Dentistry recently proposed the diagnostic criteria for oral frailty in older adults in Korea. This study aimed to conduct a cross-sectional survey of factors related to oral frailty among community-dwelling older adults and identify differences in oral frailty status according to age and sex. Methods: Among 217 older adults aged ≥60 years who visited a senior center in Wonju, 206 completed all tests for oral frailty. Among them, data from those with a Korean Version of the Modified Barthel Index score ≥90 were used in the final analysis. After evaluating oral frailty diagnostic factors such as chewing ability, occlusal force, tongue pressure, oral dryness, oral cleanliness, and swallowing function, oral hypofunction was determined according to the oral frailty diagnostic criteria. Subsequently, the evaluation results were compared based on sex and age. Results: Significant differences in chewing ability, maximum occlusal pressure, and maximum tongue pressure were observed between sexes. However, these differences did not affect oral frailty diagnosis. All diagnostic factors of oral frailty, except for the risk of oral dryness and swallowing dysfunction, showed significant differences with age. However, no significant difference was observed in the prevalence of oral frailty. Additionally, this study found no relationship between sex and oral frailty factors using the oral frailty diagnostic criteria. However, it also found that age plays a significant role as an oral frailty diagnostic indicator, in addition to oral dryness and swallowing function. Conclusion: Sex and age did not affect oral frailty diagnosis. However, patients' chewing ability, occlusal force, and tongue pressure were affected by sex and age. Therefore, sex and age should be considered when diagnosing and intervening in oral frailty in the future.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.204-214
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• 2023

The occlusal treatment including prosthetic treatment should be considered when the pathologic symptom was observed with the excessive discrepancy between the centric relation occlusion (CRO) and the maximum intercuspal position (MIP). Through careful diagnosis, the malocclusion and interarch relationship can be analyzed, and occlusal adjustment, restorative treatment, orthodontic therapy, or orthognathic surgery can be performed depending on the degree of disharmony. The patient in this case report complained the unstable occlusion and loss of masticatory function that had been occurring for several years. At the time of the visit, the patient showed severe occlusal disharmony, with only the upper right second molar contacting the lower jaw at the maximum intercuspal position. Based on the analysis of the occlusion, it was difficult to solve the problem with just occlusal adjustment or restorative treatment. In addition, the patient had the skeletal class II malocclusion between the upper and lower jaws. Therefore, for resolving the severe skeletal class II malocclusion, pre- and post-orthodontic treatment, bilateral sagittal split ramus osteotomy (BSSRO) was performed. After that, the occlusal adjustment was performed for stable occlusion, and the missing teeth area was restored with dental implants. During the follow-up period, a periodic follow-up visits and additional occlusal adjustments were performed to achieve a stable centric occlusion and harmonious anterior and lateral guidance. As a result, the final prosthodontic treatment was completed, and the patient's masticatory function was restored.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.587-597
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• 2004

Over the past 20 years, great strides have been made in research regarding the mechanisms involved in the progression of carious lesions, but new equipment and research tools need to be developed to continue these advancements in caries research. Various methods have been applied to reduce the incidence of carious lesions, which have led to a significant decrease in the number of occlusal caries, but a concurrent increase in the proportion of proximal carious lesions. New diagnostic equipment has been developed to detect early stage carious lesions, and these have demonstrated excellent laboratory results and show promise in clinical applications. The research presented here examines the efficacy of the newly developed $DIFOTI^{TM}$ system in detecting proximal carious lesions compared to traditional intraoral exam and bitewing radiography, possible problems or deficiencies of using the system in clinic, possible improvements that can be made to the system, and the efficacy of detecting early, reversible carious lesions that can be remineralized by preventative fluoride applications. The subject pool consisted of 23 grammer school age patients just prior to entering the mixed dentition phase. Each patient was given a thorough oral examination, radiographic examination consisting of bitewing radiographs of the posterior teeth, and $DIFOTI^{TM}$ examination of the anterior and posterior teeth. Each examination was carried out two times by two examiners, and the data were statistically analyzed. The results are as follows: 1. The mean alpha value of reliability test of the visual oral examination was as follows; occlusal surface was 0.8470. mesial surface was 0.6430, distal surface was 0.5727. lingual surface was 0.2807 and distal surface was 0.2339. When the examination was limited to posterior teeth, the mean alpha value was as follows; occlusal surface was 0.8577, distal surface was 0.8211, lingual surface was 0.7728, buccal surface was 0.7152 and mesial surface was 0.6782. 2. The alpha value of reliability test of the radiographic analysis of carious lesions of the occlusal, mesial, and distal surfaces was 0.8500. 3. The alpha value of reliability test of the $DIFOTI^{TM}$ diagnostic analysis of carious lesions of the occlusal, buccal, lingual, mesial, and distal surfaces was determined to be 0.7917. 4. The $DIFOTI^{TM}$ diagnostic system was found to be the most accurate means of detecting occlusal, buccal, and lingual surface carious lesions (p<0.05), while mesial and distal proximal carious lesions were most accurately assessed using bitewing radiography (p<0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.2
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• pp.135-142
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• 2022

Purpose. This study aims to evaluate the combined effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns. Materials and methods. Seven nickel-chromium dies were generated from a 3D model of mandibular first molar using the digital scanner with the following geometries: 1.5 mm occlusal reduction, 1.0 mm deep chamfer. Based on the abutment model, Zirconia blocks (Luxen Zirconia) were selected to fabricate Sixty-three zirconia crowns with occlusal thicknesses of 0.3 mm, 0.5 mm, and 1.5 mm, and different axial thicknesses of 0.3 mm, 0.5 mm, and 1.0 mm. All crowns were cemented by resin cement. Next, the crowns were subjected to load-to-fracture test until fracture using an electronic universal testing machine. In addition, fracture patterns were observed with a scanning electron microscope (SEM). Two-way ANOVA and the Tuckey HSD test for post hoc analysis were used for statistical analysis (P < .05). Results. The mean values of fracture resistancerecorded was higher than the average biting force in the posterior region. The two-way ANOVA showed that the occlusal and axial thickness affected the fracture resistance significantly (P < .05). However, the effect of axial thickness on fracture resistance did not show a statistical difference when thicker than 0.5 mm. The observed failure modes were partial or complete fracture depending on the severity of crack propagation. Conclusion. Within the limitations of the present study, the CAD-CAM monolithic zirconia crown with extremely reduced thickness showed adequate fracture resistance to withstand occlusal load in molar regions. In addition, both occlusal and axial thickness affected the fracture resistance of the zirconia crown and showed different results as combined.

• The Journal of Advanced Prosthodontics
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• v.9 no.3
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• pp.159-169
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• 2017

PURPOSE. The purposes of this study were to evaluate the marginal and internal gaps, and the potential clinical applications of three different methods of dental prostheses fabrication, and to compare the prostheses prepared using the silicone replica technique (SRT) and those prepared using the three-dimensional superimposition analysis (3DSA). MATERIALS AND METHODS. Five Pekkton, lithium disilicate, and zirconia crowns were each manufactured and tested using both the SRT and the two-dimensional section of the 3DSA. The data were analyzed with the nonparametric version of a two-way analysis of variance using rank-transformed values and the Tukey's post-hoc test (${\alpha}=.05$). RESULTS. Significant differences were observed between the fabrication methods in the marginal gap (P < .010), deep chamfer (P < .001), axial wall (P < .001), and occlusal area (P < .001). A significant difference in the occlusal area was found between the two measurement methods (P < .030), whereas no significant differences were found in the marginal gap (P > .350), deep chamfer (P > .719), and axial wall (P > .150). As the 3DSA method is three-dimensional, it allows for the measurement of arbitrary points. CONCLUSION. All of the three fabrication methods are valid for measuring clinical objectives because they produced prostheses within the clinically acceptable range. Furthermore, a three-dimensional superimposition analysis verification method such as the silicone replica technique is also applicable in clinical settings.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.148-155
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• 2008

The aim of the study is to interpret the distribution of occlusal force by 3-dimensional finite element analysis of ISP(Implant Supported Prosthesis) supported by minimum number of implant to restore the edentulous patients. For this study, the Astra Tech implant system is used. Geometric modeling for 6 and 4 fixture ISP group is performed with respect to the bone, implant and one piece superstructure, respectively. Implants are arbitrarily placed according to the anatomical limit of lower jaw and for the favorable distribution of occlusal force, which is applied at the end of cantilever extension of ISP with 30mm. Element type is tetrahedral for finite element model and the typical mechanical properties, Young's modulus and Poisson's ratio of each material, cortical, cancellous bone and implant material are utilized for the finite element analysis. From this study, we can see the distribution of equivalent stress equal to real situation and speculate the difference in the stress distribution in the whole model and at each implant fixture, From the analysis, the area of maximum stress is distributed on distal contact area between bone and fixture in the crestal bone. The maximum stress is 53MPa at the 0.2mm area from the bone-implant interface in the maximum side for 300N load condition for 4 fixture case, which is slightly less than the stress calculated from allowable strain. This stress has not been deduced to directly cause the loss of crestal bone around implant fixture, but the stress can be much reduced as the old peoples may have lower chewing force. Thus, clinical trial may be performed with this treatment protocol to use 4 fixtured ISP for old patients.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.332-338
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• 2013

Data collection including checking the problem list and analyzing the etiology cannot be overemphasized in full mouth rehabilitation cases. It is well reported that favorable prognosis of prosthodontic treatment depends on accurate diagnosis. Seventy seven year old female patient presented with chief complaints of chewing pain on maxillary and mandibular left premolars and unesthetic existing prosthesis. Clinical evaluation, radiographic examination and cast analysis were performed to gather comprehensive data and problem lists. Treatment planning was based on collected data and related articles. Abutment evaluation, prognosis depending on various types of prosthesis, and maintenance were considered as well. Occlusal vertical dimension was increased to solve esthetic dissatisfaction and insufficient interocclusal space. Patient adaptation was verified with provisional restorations followed by diagnostic wax up. Function, esthetics and occlusal stability were verified during 8 week follow-up period. Prosthodontic reconstruction based on systemic analysis, diagnosis, and treatment plan led to satisfactory result after delivery of definitive prosthesis.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.2
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• pp.119-127
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• 2012

Purpose: This study was performed to compare the stress distribution pattern of abutment-fixture connection area using 3-dimensional finite element model analysis when 5 different implant systems which have internal connection. Materials and methods: For the analysis, a finite element model of implant was designed to locate at first molar area. Stress distribution was observed when vertical load of 200 N was applied at several points on the occlusal surfaces of the implants, including center, points 1.5 mm, 3.0 mm away from center and oblique load of 200 N was applied $30^{\circ}$ inclined to the implant axis. The finite element model was analyzed by using of 3G. Author (PlassoTech, California, USA). Results: The DAS tech implant (internal step with no taper) showed more favorable stress distribution than other internally connected implants. AS compare to the situations when the loading was applied within the boundary of implants and an oblique loading was applied, it showed higher equivalent stress and equivalent elastic strain when the loading was applied beyond the boundary of implants. Regardless of loading condition, the abutments showed higher equivalent stress and equivalent elastic strain than the fixtures. Conclusion: When the occlusal contact is afforded, the distribution of stress varies depending on the design of connection area and the location of loading. More favorable stress distribution is expected when the contact load was applied within the diameter of fixtures and the DAS tech implant (internal step with no tapering) has more benefits than the other design of internally connected implants.

• Journal of Technologic Dentistry
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• v.43 no.2
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• pp.42-47
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• 2021

Purpose: The purpose of this study was to evaluate the stability of abutment screws used with the zirconia fixture-based implant system and compare them with those used with the existing titanium fixture system via the finite element method. Methods: A single implant-supported restoration was designed for the finite element analysis. A universal analysis program was used to set 8 occlusal points along the direction to the long axis of the implant, and an occlusal load of 700 N was applied. Results: In all models (Zir and Ti-fixture model), the screw threads presented with the highest von Mises stress (VMS) values, whereas the head and end presented with the lowest VMS values. The VMS of the screw used in the zirconia-fixture model was 5.97% lower than that used in the titanium-fixture model (261.258 vs. 276.911 MPa, respectively) despite statistical significance. Furthermore, the zirconia fixture (352.912 MPa) had a higher stress value (8.42%) than the titanium fixture (332.331 MPa). In a completely tightened titanium fixture implant system, the stress was concentrated in the implant-abutment connection interface, the zirconia fixture presented with a stable stress distribution. Conclusion: Although the zirconia fixture demonstrated a high VMS value, owing to the stiffness and elasticity coefficients of the material, the stress generated in the abutment screws was similar in all models. In conclusion, the zirconia fixture-based implant system presented with a more stable stress distribution in the abutment screws than the titanium fixture-based implant system.

• 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.