[Preliminary evaluation of clinical effect of computer aided design and computer aided manufacture zirconia crown].

OBJECTIVE: To evaluate clinical effects of computer aided design and computer aided manufacturing (CAD/CAM) milled zirconia crown in three aspects: aesthetic, contact wear and fracture. METHODS: Sixty patients were divided into two groups.In one group, 35 full contour CAD/CAM zirconia crown were made on molars of 30 patients. The manufacturing process of zirconia crown was as follow. First, the three dimensional(3-D) data of working models, antagonist impression and check records were acquired by 3-D laser scanning Dental wings S50. Then full contour zirconia crowns, which had functional occlusal contacts with antagonistic teeth, and appropriate contact with adjacent teeth were designed with Zeno-CAD(V4.2.5.5.12919) software. ZENOSTAR Zr pure zirconia material was milled in digital controlled machine WIELAND 4030 M1.In the end, the zirconia crown were completed with the method of second sintering and polishing. After clinical try-in, the crown was cemented.In the control group, thirty gold alloy full crown were made and cemented on molars of 30 patients. According to the modified U S Public Health Service Criteria(USPHS) evaluation standard, all crowns were evaluated on the same day, at three months, half a year, one year and two years following delivery. There were three aspects we were focusing on in the evaluation: aesthetic, contact wear(restoration and antagonist), and fracture. RESULTS: In all the prosthesis we evaluated during the 24 months, no fracture was found. Contact wear of crowns varies according to different antagonist teeth. CONCLUSIONS: The zirconia crowns show privilege in aesthesis, toughness and anti-wearing.However, there is contact wear on antagonistic natural teeth. Thus it is a good choice when full zirconia crowns are indicated on two antagonistic teeth in both jaws.

[Esthetic evaluation of Cerec 3D anterior crowns].

OBJECTIVE: To observe the short-term effect of clinical application of Cerec 3D anterior crowns. METHODS: A total of 16 patients were restored with 31 Cerec 3D anterior crowns. All restorations were stained before cementation. The evaluation started 1 week after luting. The restorations were examined in accordance with the modified US Public Health Service (USPHS) criteria at baseline and every 6 - 12 months. RESULTS: The observation period of 31 Cerec 3D anterior crowns varied from 8 to 33 months. The mean observation period was 22 months. All restorations scored A or B by modified USPHS standard. And 22 out of 31 restorations scored A for all criteria while 8 restorations scored B in color matching. Slight differences of translucency and chroma could be observed. Between baseline and follow-up examinations, insignificant shift from A-to B-rating occurred. CONCLUSION: Cerec 3D anterior crowns may achieve favorable short-term esthetic effects.

[Comparasion of clinical and technical operating time of full-crown restorations between traditional and Triple-tray impression techniques].

OBJECTIVE: To compare the difference of clinical and technical processes of full-crown restorations by using traditional and Triple-tray impression techniques, consumed materials and time estimated in every procedure of these two methods. METHODS: Four veteran clinicians were selected to carry out full-crown restorative treatment for 124 patients (130 crowns). From one impression, dentists could make casts of prepared teeth and the opposing dentition and register the interocclusal relationship.After tooth preparation,Impregum Penta polyether impression was fabricated for 76 cases(80 crowns) by Triple-tray method and 48 cases (50 crowns)by conventional method. During the whole processes, the consumption of impression materials and plaster, the time of fitting on the articulator, manufacturing procedure and try-in in clinical practice were recorded. The differences of material and time consumption in every procedure of these two methods were evaluated by Independent-Samples t test. RESULTS: The consumption of impression materials and plaster of Triple-tray impression technique was significantly less than that of traditional impression technique(P<0.01), and average time in every procedure of Triple-tray impression technique was remarkablely reduced compared with that of the traditional impression technique (P<0.01). Triple-tray impression technique reduces operating costs and the possibility of error. CONCLUSION: Compared with traditional impression technique, Triple-tray impression technique could reduce the consumption of time and materials in clinical and technical processes.