• The Journal of Advanced Prosthodontics
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• v.13 no.1
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• pp.36-45
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• 2021

Purpose. To investigate the fracture resistance of monolithic CAD-CAM all-ceramic surveyed crowns with two different occlusal rest seat designs. Materials and Methods. Two maxillary first premolar were prepared for all-ceramic surveyed crowns with wide (2/3rd of buccolingual width of an unprepared tooth) or narrow (1/3rd of buccolingual width of an unprepared tooth) disto-occlusal rest seat (ORS) designs. Eighty monolithic CAD-CAM all-ceramic surveyed crowns were prepared and divided into 4 groups - Group CR, Composite resin material as a control; Group LDS, Lithium disilicate based material; Group ZIPS, zirconia-material (IPS ZirCAD); and Group ZLHT, zirconia- material (CeramillZolidht+). Crowns were cemented on an epoxy resin die with adhesive resin cement. The fracture resistance of crowns was tested with the universal machine. Univariate regression analysis was used. Results. The mean ± standard deviation of maximum failure force values varied from 3476.10 ± 285.97 N for the narrow ORS subgroup of group ZIPS to 687.89 ± 167.63 N for the wide ORS subgroup of group CR. The mean ± standard deviation of maximum force was 1075 ± 77.0 N for group CR, 1309.3 ± 283.9 N for group LDS, 3476.1 ± 285.97 N for group ZIPS, and 2666.7 ± 228.21 N for group ZLHT, with narrow occlusal rest seat design. The results of the intergroup comparison showed significant differences in fracture strength with various material groups and occlusal rest seat designs (P<.001). Conclusion. The zirconia-based all-ceramic surveyed crowns fractured at more than double the load of Lithium disilicate based crowns. The crowns with narrow base occlusal rest seat design had statistically significantly higher fracture resistance than surveyed crowns with wide occlusal rest seat design. The use of narrow occlusal rest seat design in CAD-CAM all ceramic surveyed crowns provides higher fracture resistance, and therefore narrow occlusal rest design can be used for providing esthetics with high strength.

• Journal of Korean Dental Science
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• v.3 no.1
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• pp.32-38
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• 2010

Objective : To evaluate the relationship between the dose of Clodronate and serum level of alkaline phosphatase (ALP), calcium (Ca), and phosphate (PO4) during orthodontic tooth movement MaterialS and MethodS: A total of 18 sex-matched Wistar rats (weight=180~230g, mean age=8 weeks) were allocated into the 2.5mM Clodronate (2.5C) group, 10mM Clodronate (10C) group, or control group (n=6 for each group). After the application of a nickel-titanium closed coil spring (force of 60g) between the upper central incisors and first molars (UFM), 2.5C, 10C, or saline was injected every third day into the subperiosteum of the alveolar bone adjacent to UFM for the experimental and control groups. The animals were sacrificed 17 days later. Trunk blood was quickly collected into a heparinized tube and centrifuged at 2,000 rpm for 20 min. The plasma was used for the biochemical assays of the serum level of ALP, Ca, and PO4. Kruskall-Wallis test and Mann-Whitney test with Bonferroni correction were performed for the statistical analyses. Results : Dose-dependent increase in the level of ALP (P<0.01) and decrease in the level of Ca (P<0.001) were observed among the control, 2.5C, and 10C groups. Although there was no significant difference in PO4 between the 2.5C and 10C groups, the 10C group showed a significantly higher level of PO4 than the control group (P<0.01). Conclusion : Since Clodronate induced significant dose-dependent change in the serum level of ALP, Ca, and PO4 during orthodontic tooth movement, orthodontists should consider these biochemical markers not only as a diagnostic tool for bone turnover rate but also as a monitoring tool for orthodontic tooth movement.

• Journal of Biosystems Engineering
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• v.13 no.4
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• pp.9-19
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• 1988

The threshing of head-feed combine may be accomplished mainly by the action of impact between threshing teeth and rice. In this study, it was attempted to assess threshing performance characteristics of head-feed threshing teeth. And the characteristics of threshing teeth will be applied to the method which could analyze the time and order of impact between teeth and the rice, which was used as a basis for predicting the threshing performance and determining the optimum design parameters. The results of the study are summarized as follows: 1. About 50% of threshed material were threshed by the beginning 7 impacts on the rice bundle. Threshing torque decreased until 25 impacts and did not change thereafter. 2. There was significant difference in the threshability according to the shape of threshing teeth. The triangular-shaped tooth was the most efficient in threshability ratio and the semicircle-shaped tooth was the lowest. There was no significant difference in specific energy requirement for the varied teeth design. Torn-head ratio being generated by the semicircle-shaped and the triangular-shaped teeth in series was less than that by a single tooth with the triangular-shaped and the double setting of the triangular-shaped. Chaff generation ratio by the triangular-shaped and the semicircle-shaped teeth was less than the others tried. 3. The triangular-shaped teeth in series, which was newly designed for this study, showed an intermediate characteristics between the double setting of the triangular-shaped and the semicircle- shaped teeth. Threshability ratio of the triangular-shaped teeth in series was higher than that of the semicircle and lower than the double setting of the triangular-shaped tooth. Torn-head generation ratio for it was about same as that of the semicircle. Chaff being generated by the triangular-shaped teeth in series was about same as the double setting of the triangular-shaped teeth. 4. About 40% of threshed grains which passed through concave were concentrated under the threshing tooth and the rest of grains displayed a skew distribution toward the inlet of threshing chamber.

• The korean journal of orthodontics
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• v.54 no.3
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• pp.142-152
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• 2024

Objective: This retrospective cohort study aimed to assess and compare the accuracy of 3 different Invisalign^® treatment regimens in terms of variations of aligner change frequency and type of aligner material in achieving maxillary dental buccal expansion. Methods: Altogether, 120 adult patients whose treatment involved maxillary dental expansion with Invisalign^® were included. The patients were divided into 3 groups, with each group comprising 40 patients as follows: SmartTrack^® 1-week changes (ST1), SmartTrack^® 2-week changes (ST2), and EX30^® 2-week changes (EX2). The groups were assessed by comparing actual changes achieved with those prescribed by ClinCheck^®. The rates of clinically significant inaccuracies (CSI) observed for buccal expansion (≥ 0.5 mm) and buccolingual inclination (≥ 2°) during expansion were then determined. Results: In terms of expansion, the ST1 group demonstrated the highest CSI rate at all tooth levels, whereas the ST2 group had the lowest rate of CSI and the lowest mean inaccuracy for each tooth level. In terms of buccolingual inclination, the ST1 group had the highest CSI rate across all tooth levels, whereas the EX2 group had the lowest CSI rate at all tooth levels except for the canine level where the ST2 group had the lowest CSI rate. A tendency toward overexpression of buccal crown inclination, and underexpression of buccal expansion was observed at all tooth levels. Conclusions: Two-week aligner change regimens offer improved accuracy compared with 1-week aligner changes. SmartTrack^® 2-week changes were the most accurate for buccal expansion, whereas EX30^® 2-week changes were the most accurate for buccolingual inclination.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.46 no.1
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• pp.84-84
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• 2020

• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.460-469
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• 2006

This article complies a survey on the replacement of the posterior restorations and accesses possible factors that influence the replacement of posterior restorations. The data was collected from patients that visited department of conservative dentistry from Dec 1st 2003, to Sep 3rd 2004. Teeth was restricted to posterior permanent teeth. 9 dentists recorded age, gender of patients, tooth location, cavity farm and restorative material. They rated marginal adaptation, anatomic form, secondary caries of old restoration by modified Ryge criteria system. The statistical analysis was performed with Chi square test (p < 0.05) for replacement ratio according to patients, tooth factor and One way ANOVA was performed for comparison of old restoration according to restorative material. The results were as follows; 1. The female (62%) was statistically higher ratio than the male (38%). 2. The distribution of replacement case according to age, the rate of replacement was in descending order, 20's (38.3%), 40's (16.8%), 30's (15.9%), 10's (11.1%), 50's (9.2%), 60's (8.7%). 3. The rate of replacement was 88% for molar and 12% for premolar (p $gt; 0.05). 4. The rate of replacement was 39% for maxillar and 61% for mandible (p $gt; 0.05). 5. The material of restorations was amalgam (69%), gold inlay (17%), composite resin (13%). 6. In rating system by modified Ryge criteria system on margin adaptation, there was statistically significant difference between amalgam and gold inlay. But on anatomic form and caries, there was no statistically significant difference among the material of restorations.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.291-316
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• 1993

Restorative procedures can lead to tooth fracture due to the relatively small amount of the remaining tooth structure. It is essential to prevent fractures by having a clear concept of the designs for cavity preparations. Among the several parameters in cavity designs, profound understanding of isthmus width factor would facilitate selection of the appropriate cavity preparation for a specific clinical situation. In this study, MO amalgam cavity were prepared on maxillary first premolar and filled with amalgam. Three dimensional, model with 1365 8-node brick elements was made by serial photographic method. In this model, isthmus was varied in width at 1/4, 1/3, 1/2 and 2/3 of intercuspal width and material properties were given for three element groups, i.e., enamel, dentin and amalgam. A load of 500 N was applied vertically on amalgam and enamel. In case of enamel loading, 2 model (with and without amalgam) was compared to consider the possibility of play at the interface between tooth material and amalgam. These models were analyzed with three dimensional finite element method. The results were as follows: 1. The stress was concentrated on the facio-pulpal line angle and distal marginal ridge of the cavity. 2. With the increase of the isthmus width, the stress spread around the facio-pulpal line angle and the area of stress concentration moved toward the proximal box. 3. In case of narrow isthmus width, the initiation point of crack would be in the area of isthmus corner of the cavity, and with the increase of the isthmus width, it would move toward the proximal box and at the same time the possibility of crack increase at the distal marginal ridge. 4. The direction of crack progressed outward and downward from the facio-pulpal line angle, and with the increase of the isthmus width, it approximated vertical direction. At the marginal ridge, it occurred in vertical direction. 5. It would be favorable to make the isthmus width narrower than a third of the intercuspal width, and to cover the cusp if isthmus width were wider than half of the intercuspal width. 6. It is necessary to apply the possibility of play to the finite element analysis.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.6
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• pp.694-700
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• 2007

It is a gel type high functional toothpaste containing vitamin C, E, propolis extract and the rest of herb with a nanoemulsion state. Vitamin C, E is known as the material with an eminent anti-oxidation effect. Propolis is known as the material with an antimicrobial and anti-inflammatory effect. We have been succeeding in making nanoemulsion of vitamin C, E and propolis through the high pressure homogenizer using stable oil and lecithin and the gel type high functional tooth paste were made from nanoemulsion of vitamin C, E and propolis. We observed the process of wound protecting effect and cure effect for a wound of soft tissue, gingival tissue and mucous membrane showing ulcer and inflammation in oral cavity after applying a gel type high functional toothpaste to patient. As a result, the wound were healed very fast and any side effects were not shown. We confirmed that a gel type high functional toothpaste with nanoemulsion of vitamin C, E and propolis extract has good effect not only for wound healing but also for treatment of ulcer-like lesion in oral cavity. So we report our cases with review of literatures.

• Restorative Dentistry and Endodontics
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• v.21 no.2
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• pp.489-504
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• 1996

The purpose of this study was to compare the adaptation to the tooth structure of five light cured glass ionomer cements (Fuji II LC. VariGlass VLC, Vitremer, Dyract and Geristore). Human, non-carious fifty extracted permanent premolars stored in normal saline were used. Class V cavity preparations were created on the buccal surfaces. The occlusal margin of each cavity was placed on the enamel and the gingival margin was placed on the cementum/dentin. The teeth were then distributed at random into five groups of 10 teeth each. Group 1: Fuji II LC, Group 2 : VariGlass VLC, Group 3 : Vitremer, Group 4: Dyract, Group 5 : Geristore. The prepared cavities were restored with one of the five light cured glass ionomer cements. The manipulation of each material was handled according to the manufacturer's instructions. All samples were placed in incubator of 100% relative humidity at $37^{\circ}C$ for 24 hours. The roots of the teeth were removed with the tapered fissure bur and the remaining crowns were sectioned buccolingually through the center of restorations. The cut interfaces were gradually hand polished on sandpapers from 300 up to 1200 grit. The adaptation at the tooth/cements interface was assessed by SEM (JSM-840A, JEOL Ltd.). The results of this study were as follows : 1. Group 2 revealed the best adaptation and groups 1, 4 and 5 revealed similar adaptation pattern to the cavity walls. Group 3 revealed the worst adaptation to the cavity walls. 2. Enamel margins showed better adaptation than dentin/cementum margins with each material except group 3. 3. The hybrid layers were observed between the glass ionomer cement and dentin in groups 2, 4 and 5.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.2
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• pp.135-142
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• 2023

Resin-bonded fixed partial denture (RBFPD)as known as Maryland bridge is is a well-known conservative method for its minimized invasion of the teeth for an anterior single tooth edentulous area. Despite of its various advantages, RBFPD was not widespread because of its high debonding rates, non-esthetic look or weak structure for material property. Currently, with the introduction of zirconia to dental material for RBFPD, Maryland bridge entered upon a new phase. Zirconia surmounts poor esthetics of metal framework, having proper strength, and overcomes ceramic's structural weakness, being sufficiently esthetic. In this case, edentulous area of maxillary left lateral incisor was restored using zirconia resin-bonded fixed partial denture. Restoration of missing tooth in anterior area was achieved using non-invasive and esthetic prosthesis, then we report this case as satisfactory results were obtained for both the operator and the patient.