• The Journal of Korean Academy of Prosthodontics
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• v.41 no.4
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• pp.466-475
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• 2003

Statement of problem : In cemented implant-supported porstheses, it is still controversy what kind of cement to use. However, the effect of thermocycling on retentive strength of cemented implant-supported prostheses has not been well investigated. Purpose : This study was tested to evaluate the effects of various cements and thermocycling on retentive strengths of cemented implant-supported prostheses. Material and methods : Prefabricated implant abutments, height 5mm, diameter 6mm, 3-degree taper per side, with light chamfer margins were used. Ten specimens of two-unit fred partial denture were fabricated. The luting agents used for this study were three provisional luting agents which were Temp bond, Temp bond NE, IRM and four permanent luting agents which were Panavia F, Fuji-cem, Hy-bond Zinc cement, Hy-bond Polycarboxylate cement. 24 hours after cementation. the retentive strengths were measured by the universal testing machine with a cross-head speed of 0.5mm/min. Then cementation procedures were repeated and specimens were thermocycled 1000 times at temperature of $5^{\circ}C$ and $55^{\circ}C$. After thermocycling, the retentive strengths were measured. Results : Before thermocycling, the retentive strengths were decreased with the sequence of Panavia F. Fuji-cem. Hy-bond Zinc cement. Hy-bond Polycarboxylate cement, IRM, Temp bond NE and Temp bond, and there were significant differences among each groups(p<0.05). After thermocycling, the retentive strengths were decreased with the sequence of Panavia F. Fuji-cem, Hybond Zinc cement, Hy-bond Polycarboxylate cement, IRM, Temp bond NE and Temp bond, and there were no significant differences among Panavia F, Fuji-cem and Temp bond NE, Temp bond(p>0.05). The retentive strengths before and after thermocycling showed significant differences in Hy-bond Zinc cement. IRM, Temp bond NE and Temp bond(p<0.05). Conclusion : Within the limitation of this study, thermocycling do not affect the retentive strengths of permanent luting agents but the retentive strengths of temporary cements were reduced significantly after thermocyling.

• Journal of dental hygiene science
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• v.20 no.1
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• pp.34-43
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• 2020

Background: The number and curriculum of dental hygienists in Korea have dramatically increased. Controversies have since resulted from insufficient job descriptions of the work performed by a dental hygienist. A dentist's perception was examined to legally reflect the actual work of dental hygienists. Methods: Four hundred and nineteen dentists were surveyed about the duties of a dental hygienist. Their views on the career and availability of each job were examined. The duties of the dental hygienist include 13 items in dental treatment preparation, 14 items of radiography, 21 items of preventive dentistry, 6 items of periodontal treatment, 12 items of oral medicine, 12 items of conservative dentistry, 8 items of prosthetics, 10 items of orthodontics, 7 items of oral and maxillofacial surgery, 6 items of implantation, 6 items of impression taking and model fabrication, 5 items of anesthesia and injection, 11 items of management and administrative, and 3 items of self-development. Results: Most of the duties were doable by a dental hygienist. Many dentists reported that managing implants, oral hygiene of special patients, some duties in oral medicine, teeth brightening, making temporary crowns, making individual trays, selecting shades, ligaturing, and precision impressions need ≥3 years of experience. Duties perceived by dentists not to be performed by dental hygienists were reading radiographs (55.4%), suture and stitch out (48.0%), intramuscular injection (36.0%), root planning (27.2%), cementation and removal of prostheses (23.2%), and examining pulp vitality (22.0%). Conclusion: Current laws are to be revised to include, the care provided by dental hygienists and under a physician's supervision. Flexibility is also needed to cope with rapidly changing dental technology.

• The korean journal of orthodontics
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• v.25 no.4
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• pp.403-414
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• 1995

The purpose of this study was to investigate the histologic changes in mandibular periodontium during overbite closure for openbite treatment by continuous arch wires and anterior vertical elastics. Two female monkey(Macaca nemestrina) with permanent dentition were used. Posterior bite block was fixed to each of their maxillae, which made the animal temporary anterior openbite as well as stabilized the whole maxillary anchorage. In each mandible, all the teeth except the second molars which had been extracted, were prepared for cast crowns. 018 inch Standard brackets were welded on these crowns. After cementation, two types of the $016{\times}022$ inch continuous arch wires, the plain ideal arch to the control animal and the MEAW(multiloop edgewise archwire) to the other experimental one were inserted. Then anterior vertical elastics were applied for two weeks. The overbite depth changes in the monkeys and histologic examinations of the mandibular periodontiums suggested the following conclusions. 1. During two weeks of the experimental period, the overbite increased + 0.3 mm in the control and + 1.3 mm in the experimental one. 2. In both the control and the experimental animal, histologic examinations showed that incisors, canines and first premolars were subject to extrusive force and the rest of posteriors were subject to intrusive one. 3. In periodontiums of the extruded incisors of the experimental one, reorientation of the periodontal fiber structures reflected the direction of force and the alveolar bone surfaces including apical and crestal areas which had been subject to tension, were the front of new bone formation. 4. In periodontiums of the extruded incisors of the experimental one, neither excessive hyalinization nor gross root resorption was observed. 5. Alveolar bone remodeling of anteriors and posteriors was more remarkable in the experimental one than the control.