Résumé
BACKGROUND:At present, the confrontation of CAD/CAM systems and the lost wax casting method for marginal adaptation has been widely concerned, but the results are controversial. OBJECTIVE:To compare the marginal adaptation of single cobalt-chromium PFM crowns produced by 3 Shape CAD/CAM systems and the lost wax casting method. METHODS: A maxilary first premolar was prepared according to the standards. 50 resin-generation models were created by bi-color silicone rubber method and randomly divided into two groups: CAD/CAM group (A1-A25) and cast group (B1-B25). Al the models were cast in plaster. In CAD/CAM group, the digital impressions were obtained by optical scanning, then designed through computer and cut directly by NC miling machine. In cast group, metal ceramic crowns were made by the lost wax casting method. When crowns were al seated on the working dies, the marginal gaps were copied with light silicone rubber and then embedded with occlusal silicone rubber. The thickness of crown marginal gap was measured with a stereo microscope. RESULTS AND CONCLUSION:The average vertical clearance was (34.67±7.48)μm of CAD/CAM group, while (53.70±9.64)μm of the cast group; the difference was statisticaly significant between two groups (P < 0.05). The average level clearance was (37.61±7.63)μm of CAD/CAM group, while (53.02±10.65)μm of the cast group, and the difference was statisticaly significant between two groups (P < 0.05). Experimental findings suggest that, the marginal adaptation of single cobalt-chromium PFM crowns cast produced by 3 Shape CAD/CAM systems is clinical acceptable (< 120μm), and CAD/CAM systems of metal casting is obviously better than the lost wax casting in building metal based crowns with adaptable margin.
Résumé
BACKGROUND:VITA 3D Master shade guide is a newly launched colorimetric system in recent years, with a wide clinical prospect. OBJECTIVE:To evaluate the significance of dentin colorimetric evaluation for accurate color section of cast ceramic prostheses. METHODS:Using conventional colorimetric assay and conventional colorimetric assay combined with dentin colorimetric assay (combined colorimetric assay), 30 patients were subject to colorimetric evaluation 1/3 to the neck, central part, and cut end of the tooth. In CIE1976L*a*b*color system, a digital SLR camera (Canon D50) was used for colorimetric measurement and analysis of cast ceramic prostheses prepared with two colorimetric methods and teeth with the same name. And a variety of new colorimetric methods were analyzed based on examples. RESULTS AND CONCLUSION:In the conventional colorimetric group,△L*was 1.22±0.16,△C*was 1.19±0.20,△H*was 0.31±0.05,△E*was 1.32±0.13. in the combined colorimetric group,△L*was 1.03±0.11,△C*was 1.12±0.19,△H*was 0.29±0.03,△E*was 1.23±0.11. Cast ceramic prostheses prepared by conventional colorimetric method were satisfactory in 22 cases, while cast ceramic prostheses prepared by the combined colorimetric method were satisfactory in 23 cases. There was no difference in patient satisfaction for color rendition (P>0.05), but chromatic difference analysis was significantly different between the two groups (P<0.05).
Résumé
BACKGROUND:There are many methods for dental impression disinfection, including ultraviolet disinfection method, spraying, immerses disinfection method, argon plasma jet and radio frequency glow discharge on the argon gas ionization disinfection method. At present, there is stil lack of studies addressing the disinfection effect after gargling with mouthwash. OBJECTIVE:To detect the kil ing effect on bacteria and fungi from the dental impressions, which are taken after gargling with cetylpyridinium chloride gargle and stable chlorine dioxide gargle, respectively. METHODS:One hundred patients were randomly divided into cetylpyridinium chloride gargle group and stable chlorine dioxide gargle group. They were told to gargle with clean water for 1 minute, and then impressions were taken to remove the models with sterile cotton swab sampling in neutralizing agent which were sent to laboratory for bacteria and fungi culture. After 1 hour, the patients were asked to gargle with the different mouthwashes for 1 minute again, and then sterile cotton swab sampling was done at the same position for bacteria and fungi culture. The number of colonies was recorded, and the kil ing effects on kil ing bacteria and fungi on the surface of the impressions before and after gargling with different mouthwashes were observed. RESULTS AND CONCLUSION:The number of bacteria and fungi before gargal had no significance difference before gargling. After gargling, the number of bacteria and fungi on the model was significantly lower than before (P<0.001). Two groups did not appear with any adverse reactions, and patients felt refreshed and comfortable after gargling with mouthwash. To gargle with mouthwash before taking impressions can control the number of bacteria and fungi on the samples effectively, thereby achieving the aim of control ing the mutual infections between the doctor and the patients effectively.