An influence of operator's posture on the shape of prepared tooth surfaces for fixed partial denture / 대한치과보철학회지

PURPOSE: Dentists suffer back, neck and shoulder pain during their careers due to bad operating posture. If dentists have a good operating posture ergonomically, there would be less pain and discomfort in the shoulder and back. Therefore, dentists should learn the Home position which enables dentists to approach a stable posture ergonomically. This study was to compare tooth preparation in the Home position and the Random position, and evaluate the clinical efficacy of the Home position. MATERIALS AND METHODS: Tooth preparation for fixed partial denture was performed on the maxillary left 2nd premolar and maxillary left 2nd molar at the two different operating positions were compared. The amount of occlusal reduction, marginal width, subgingival margin depth, and convergence angle were measured. A T-test was performed separately to compare the results of the Random position and the Home position. RESULTS: 1. The amounts of average thickness of occlusal reduction on fossa were deficient to the ordered ones in the Random position and the Home position (P > .05). 2. The average subgingival margin depth of prepared margin on maxillary left 2nd premolar, maxillary left 2nd molar were excessive in the Random position than in the Home position. On the maxillary left 2nd premolar, there was no statistical difference in the Random position and the Home position except Distal midline, DL line angle, Lingual midline, ML line angle (P .05). 4. Analysis of pearson correlation : In the Random position, the amounts of average thickness of occlusal reduction, the average subgingival margin depth of prepared margin, convergence angle were significantly associated with each other (P < .05). But in the Home position, they were not significantly associated with each other (P < .05). 5. The time needed for preparation in the Home position was faster or equal than that of the Random position as time went on. CONCLUSION: In conclusion, there were no significant differences between Home postion and Random position in measures of occlusal reduction, marginal width, marginal depth, convergence angle. However, preparation time and incidence of damaging adjacent teeth were less in Home position than in Random position. Therefore, if trained properly, Home position which is more ergonomically stable can be adopted for clinical use.

The effect of permanent magnet connecting with dental implant on bone extracellular matrix formation / 대한치과보철학회지

STATEMENT OF PROBLEM: The use of permanent magnetics is increasing in implant dentistry. PURPOSE: This study is to know the effect of permanent magnetics on bone matrix formation of osteoblasts. MATERIALS AND METHODS: The konus abutment-shaped permanent magnetics were connected to the implant fixture, and placed on the culture plate. The osteoblast-like cell: Mc3T3-E1 were used for cell culture. As the control group, the implants were connected to titanium healing caps, and cultured in the same conditions of experimental group. After 3, 7, 14 days, cells were cultured, and we measured and compared the amount of collagen type I, osteocalcin, which is bone matrix protein by Western immunoblotting analysis. RESULTS: As a result of Western immunoblotting analysis for estimating the amount of bone extracellular matrix, there was no difference between osteoblast of the experimental group and the control group during 3 and 7day-osteoblast culturing. However when cells were cultured for 14days, the amount of bone extracellular matrix was increased, on the experimental group. CONCLUSION: From these results, magnetic field of permanent magnetics might have effect on bone formation of osteoblast, especially at initial stage of implant placement. Therefore, their clinical application for implant or bone graft could be possible.