• Korean Journal of Health Education and Promotion
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• v.21 no.4
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• pp.121-135
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• 2004

This study aims to analyze the oral health status of the elderly. Study subjects were 9,340 elderly aged over 65 who took the health examination (the first) for the local insured when the National Health Insurance Corporation carried out its survey from January to December, 2002. The subjects took an oral examination and filled in the questionnaire. Major results from the analysis are as follows: 1. Analysis of Oral Health Behavior For oral health behavior, 38.2％ of total subjects had visited a dental hospital (or clinic) in the last one year in the order of the elderly of big cities (48.3％), the elderly of medium cities (43.9％), and the elderly of rural areas (29.0％)(P<0.001). Elderly men had a higher rate than elderly women, and the younger age had a higher rate(P<0.01). For experience of oral prophylaxis, 12.3％ of the total elderly had experienced it in the order of the elderly of big cities (18.8％), the elderly of medium cities (16.0％), and the elderly of rural areas (6.4％) (P<0.001). For elderly men, the younger age had a higher rate of oral prophylaxis. The number of toothbrushing in order was twice(47.5％), once (26.7％), three times (25.0％), and none (0.7％). The younger age brushed their teeth more often (P<0.001). 2. Analysis of Oral Health Status The rate of caries was 10.6％ of the elderly surveyed. By area, the elderly of rural areas had a higher rate of caries than the elderly of cities (p<0.001) and elderly men were higher than elderly women (p<0.001). By age, many elderly aged over 80 had more than two caries. For missing teeth, the elderly of rural areas had a higher rate than the elderly of cities (p<0.001) and the older age had a higher rate(p<0.001). The rate of periodontal disease was 43.2％ of the total elderly. By area, the elderly of big cities (46.2％) had a higher rate of periodontal disease than the elderly of medium cities (39.4％) and rural areas (43.6％)(p<0.001), and elderly men (46.4％) were higher than elderly women (40.2％)(p<0.001). By age, the lower age had a higher rate of peridontal disease (p<0.001). Dental abrasion was observed in 16.9％ of the total elderly. The elderly of cities (21.0％) had a higher rate than the elderly of rural areas (12.0％)(p<0.001) and elderly men (21.3％) were higher than elderly women (12.8％)(p<0.001). Also the lower age had more dental abrasion symptoms (p<0.001). For needing a denture, the rate among the elderly was 48.5％ and was higher for the elderly of rural areas(20.9％), than the elderly of big cities(7.0％) and medium cities (10.5％)(p<0.001). For the rate of denture wearing, the elderly of rural areas(41.8％) were higher than the elderly of big cities (27.7％) and medium cities (28.2％ )(p<0.001). For the relation of drinking and smoking to oral health, the elderly who had a higher frequency of drinking, had a higher rate of caries (p<0.001)periodontal disease(p<0.001) and missing teeth(p<0.001) Smokers had a higher rate of caries (p<0.001), periodontal disease (p<0.05), and missing teeth (p<0.001) than nonsmokers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.19-24
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• 2015

Gears are produced through a variety of methods. In general, a metal piece is formed into the general shape of a gear through rough cuts. The gear then moves on to a more precise machine that removes more material. Grinders work via abrasion, rubbing a rough surface against a work piece at such high speeds that it literally scrapes unwanted material away from the item. Since the grinder is spinning so fast, the material is removed very quickly. This allows a grinder to remove a very small amount without taking any unwanted material with it. This study investigates the effect of grinding process parameters like grinding spindle speed and table transfer speed on the gear grade and grinding efficiency.

• Journal of Periodontal and Implant Science
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• v.39 no.4
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• pp.437-441
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• 2009

Purpose: The purpose of this report is to show three cases treated by an intergrated periodontal and restorative dentistry approach. Methods: Three patients with Miller Class Ⅰgingiva recessions associated with cervical lesions were enrolled for treatment. Two patients received a connective tissue graft and resin modified glass ionomer, and one patient was treated with a connective tissue graft, resin restoration. Keratinized gingiva and relative gingival recession were measured. Results: The mean reduction of relative gingival recession was 3.7 mm, and the mean keratinized gingiva increase was 2.5 mm. The percentage of root coverage was 80% in average. No signs of gingival inflammation or bleeding on probing were seen. The patients were satisfied with the final esthetics and had no more dentin hypersensitivity. Conclusions: This report indicates that teeth with Miller ClassⅠ gingival recession associated with cervical lesions can be successfully treated by a connective tissue graft combined with restorative dentistry. However, longitudinal randomized controlled clinical trials must be performed to support this approach.

• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.55-63
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• 1987

The purpose of this study is to evaluate the effect of dentin bonding agents on marginal leakage. V-shaped cavities were prepared on the faciocervical area of 140 extracted human teeth. In Groups of twenty cavities, they were restored as follow: Group 1 with enamel bonding resin and Silux, Group 2 Scotchbond and Silux, Group 3 enamel bonding resin and Heliomolar, Group 4 Dentin Adhesit and Heliomolar, Group 5 enamel bonding resin and Durafill, Group 6 Dentin Adhesive and Durafill, Group 7 Chembond. All specimens were thermocycled alternatively at $4^{\circ}C$ and $60^{\circ}C$ of 2% methylene blue dye solution, and sectioned faciolingually with diamond disk under water spray. The sectioned specimens observed with stereo microscope. Following results were obtained: 1. The groups filled with Scotchbond-Silux or Dentin Adhesit-Heliomolar had appeared lesser marginal leakage compared with the groups with enamel bonding resin-Silux or enamel bonding resin-Helimolar. 2. The group filled with Dentin Adhesive-Durafill did not show the reduction of the marginal leakage compared with the group with enamel bonding resin-Durafill. 3. There was significant difference among the four dentin bonding agents. Scotchbond showed the greatest marginal sealing ability, and Dentin Adhesit was the next. The marginal sealing ability of Dentin Adhesive was the worst.

• The Journal of Advanced Prosthodontics
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• v.11 no.1
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• pp.7-15
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• 2019

PURPOSE. The aim of this study was to identify the effects of three aesthetic restorative materials on the wear between tooth and restoration by a pin-on-disk manner. MATERIALS AND METHODS. Six aesthetic restorative materials were used to prepare disk specimens for wear test, which were Lava Zirconia as zirconia group, Vintage MP and Cerabien ZR as veneering porcelain group, Gradia Direct microhybrid composite containing prepolymerized fillers, Filtek Z250 microhybrid composite containing zirconia glass and colloidal silica particles, and Filtek Z350 nanocomposite as composite resin group. Vertical loss of the worn cusp, change of the surface roughness of the restoration materials, and the surface topography were investigated after wear test under 9.8-N contact load. RESULTS. The porcelain groups (Vintage MP and Cerabien ZR) caused the largest vertical loss of teeth when compared with those of the composite resin and zirconia groups, and Filtek Z250 microhybrid composite results in the second-largest vertical loss of teeth. The surface of Filtek Z350 nanocomposite was deeply worn out, but visible wear on the surface of the zirconia and Gradia Direct microhybrid composite was not observed. When the zirconia surface was roughened by sand-blasting, vertical loss of teeth considerably increased when compared with that in the case of fine polished zirconia. CONCLUSION. It was identified that microhybrid composite resin containing a prepolymerized filler and zirconia with reduced surface roughness by polishing were the most desirable restorative materials among the tested materials to prevent the two-body wear between aesthetic restorative material and tooth.

• Restorative Dentistry and Endodontics
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• v.30 no.1
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• pp.22-30
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• 2005

The purpose of this study was to compare the effect of surface sealing materials on microleakage and surface roughness in Class V composite restorations. Twenty five standardized Class V cavity preparations were made on the facial surface of human premolars and were randomly assigned to 5 groups. The teeth were restored with Z-250 after applying Single Bond. Following 7 days storage in distilled water at $37^{\circ}C$, the restorations were sealed as following systems : No sealing ; Single Bond Adhesive ; Biscover ; Fortify ; Optiguard. Then, toothbrush abrasion test was conducted using a wear testing machine. Surface roughness was measured by means of profilometer before and after toothbrushing and the results were statistically analysed by using a paired t-test and ANOVA. The bonded interfaces and the changes of surface roughness were examined by SEM. For microleakage test, specimens were stained in a $2\%$ methylene blue solution, then longitudinally sectioned and analyzed for leakage at occlusal and cervical interfaces using stereomicroscope. The results were statistically analysed by using a Kruskal-Wallis and Mann-Whitney U test. Surface roughness was increasing in all groups after toothbrushing, but no statistically significant differences. In SEM observation, surface sealant was partially retained and partially detached in bonded interfaces. Especially, microgap was identified in cervical margins. In microleakage test, there was better seal in the enamel region and a significant difference between groups at occlusal margin. Control group and Single Bond group had significantly better marginal seal at enamel margin than cervical margin.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.126-132
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• 2013

PURPOSE. Post surface conditioning is necessary to expose the glass fibers to enable bonding between fiber post and resin cement. The purpose of the present study was to evaluate the effect of different surface conditioning on tensile bond strength (TBS) of a glass fiber reinforced post to resin cement. MATERIALS AND METHODS. In this in vitro study, 40 extracted single canal central incisors were endodontically treated and post spaces were prepared. The teeth were divided into four groups according to the methods of post surface treatment (n=10): 1) Silanization after etching with 20% $H_2O_2$, 2) Silanization after airborne-particle abrasion, 3) Silanization, and 4) No conditioning (Control). Adhesive resin cement (Panavia F 2.0) was used for cementation of the fiber posts to the root canal dentin. Three slices of 3 mm thick were obtained from each root. A universal testing machine was used with a cross-head speed of 1 mm/minute for performing the push-out tests. Two-way ANOVA and Tukey post hoc tests were used for analyzing data (${\alpha}$=0.05). RESULTS. It is revealed that different surface treatments and root dentin regions had significant effects on TBS, but the interaction between surface treatments and root canal regions had no significant effect on TBS. There was significant difference among $H_2O_2$ + Silane Group and other three groups. CONCLUSION. There were significant differences among the mean TBS values of different surface treatments. Application of hydrogen peroxide before silanization increased the bond strength between resin cements and fiber posts. The mean TBS mean values was significantly greater in the coronal region of root canal than the middle and apical thirds.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.280-287
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• 2019

In the oral cavity, the teeth undergo wear and corrosion throughout their lives. Progressive and constant tooth wear is a natural phenomenon of aging, but wear and corrosion due to specific factors are pathological factors. It can cause pathological damage of the occlusal surface, aesthetic problems, dimensional loss and jaw joint disorders. This case is a 26-year-old female patient with general tooth abrasion and erosion on the entire dentition. Diagnostic wax-up was fabricated based on the information including digital facial analysis, physiological stabilization, and evaluation of anterior crown length. Through the digital analysis, the necessary guides for crown lengthening were prepared and the mastication function and esthetics were evaluated by using temporary crowns. Definitive prosthesis was fabricated with the zirconia restorations. The results were satisfactory when they were observed 3 months of follow-up.

• Journal of Periodontal and Implant Science
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• v.52 no.2
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• pp.116-126
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• 2022

Purpose: This study evaluated the efficacy of treating periodontitis using subgingival nano-hydroxyapatite powder with an air abrasion device (NHAPA) combined with scaling and root planing (SRP). Methods: A total of 28 patients with stage III periodontitis (grade B) were included in this study, although 1 was lost during follow-up and 3 used antibiotics. The patients were divided into a test group and a control group. All patients first received whole-mouth SRP using hand instruments, and a split-mouth approach was used for the second treatment. In the test group, the teeth were treated with NHAPA for 15 seconds at 70% power per pocket. Subgingival plaque samples were obtained from the 2 deepest pockets at the test and control sites before treatment (baseline) and 3 months after treatment. The full-mouth plaque index (PI), gingival index (GI), papillary bleeding index (PBI), bleeding on probing (BOP), probing depth (PD) and clinical attachment level (CAL) were recorded at baseline and at 1- and 3-month post-treatment. Real-time polymerase chain reaction was used to determine the colonisation of Treponema denticola (Td), Porphyromonas gingivalis (Pg), and Aggregatibacter actinomycetemcomitans in the subgingival plaque. Results: From baseline to the first month, the test group showed significantly larger changes in BOP and CAL (43.705%±27.495% and 1.160±0.747 mm, respectively) than the control group (36.311%±27.599% and 0.947±0.635 mm, respectively). Periodontal parameters had improved in both groups at 3 months. The reductions of PI, GI, BOP, PD, and CAL in the test group at 3 months were greater and statistically significant. The total bacterial count and Td and Pg species had decreased significantly by the third month in both groups (P<0.05). Conclusions: Applying NHAPA in addition to SRP improves clinical periodontal parameters more than SRP alone. Subgingival NHAPA may encourage clot adhesion to tooth surfaces by increasing surface wettability.

• Korean Journal of Materials Research
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• v.33 no.8
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• pp.337-343
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• 2023

3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals) ceramics have excellent mechanical properties including high fracture toughness, good abrasion resistance as well as chemical and biological stability. As a result, they are widely used in mechanical and medical components such as bearings, grinding balls, and hip implants. In addition, they provide excellent light transmittance, biocompatibility, and can match tooth color when used as a dental implant. Recently, given the materials' resemblance to human teeth, these ceramics have emerged as an alternative to titanium implants. Since the introduction of CAD/CAM in the manufacture of ceramic implants, they've been increasingly used for prosthetic restoration where aesthetics and strength are required. In this study, to improve the surface roughness of zirconia implants, we modified the 3Y-TZP surface with a biocomposite of hydroxyapatite and forsterite using room temperature spray coating methods, and investigated the mixed effect of the two powders on the evolution of surface microstructure, i.e., coating thickness and roughness, and biological interaction during the in vitro test in SBF solution. We compared improvement in bioactivity by observing dissolution and re-precipitation on the specimen surface. From the results of in vitro testing in SBF solution, we confirmed improvement in the bioactivity of the 3Y-TZP substrate after surface modification with a biocomposite of hydroxyapatite and forsterite. Surface dissolution of the coating layer and the precipitation of new hydroxyapatite particles was observed on the modified surface, indicating the improvement in bioactivity of the zirconia substrate.