OBJECTIVE: To predict the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training based on the modified Wright learning curve model, then to analyze and applicate the learning curve. METHODS: Twelve graduate students participating in standardized dental resident training were selected to prepare the resin maxillary central incisors on phantom head simulators for all ceramic crowns 4 times. The results of preparation were evaluated by 3 prosthetic experts with at least 10 years' experience focusing on the reduction, contour, taper, shoulder, finish line, margin placement, adjacent tooth injury, and preparation time for tooth preparation. The learning rate of tooth preparation was calculated by scores of tooth preparation of 4 times. The learning curve of tooth preparation was predicted based on the modified Wright learning curve model. According to the criteria of standardized training skill examinations for dental residents in Beijing, 80 was taken as the qualified standard score. The minimum training times for tooth preparation to satisfy the qualified standard score (80) was calculated, to analyze the characteristics of learning curve and evaluate the effectiveness of tooth preparation. RESULTS: The scores of 4 tooth preparation were 64.03±7.80, 71.40±6.13, 74.33±5.96, and 75.98±4.52, respectively. The learning rate was (106±4)%, which showed the learning curve an upward trend. There were no significant differences between the qualified standard score and the predicted scores of tooth preparation from the 5^th preparation to the 13^th preparation (P > 0.05). The predicted score of the 14^th preparation was higher than the qualified standard score (P < 0.05). CONCLUSION The trend of the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training is upward, which predicts the minimum training times higher than the qualified standard score is 14 times.
Humans ; Tooth Preparation, Prosthodontic/methods* ; Incisor ; Learning Curve ; Crowns ; Tooth Preparation ; Ceramics ; Dental Porcelain ; Dental Prosthesis Design

OBJECTIVETo evaluate the clinical performance of the two configurations of gingival margin preparation of tooth.

METHODSThe cases in this study were divided into two groups according to different tooth defects. Each group consisted of 40 cases. One group's gingival margin configuration was 90 degree shoulder, the other was under-gingival non-shoulder. The clinical performance of these restorations was followed up for 1 year and 2 years. The evaluators examined the restorations for plaque index, gingival index, marginal discolor and marginal fit.

RESULTSThere was no significant difference in the evaluators between the two groups.

CONCLUSIONThe under-gingival non-shoulder margin configuration of porcelain fused to metal should be used for clinical application compared with the 90 degree shoulder one in certain circumstance.

Dental Porcelain ; Dental Prosthesis Design ; Humans ; Metal Ceramic Alloys ; Tooth Preparation, Prosthodontic ; methods

Finite element stress analysis has been widely used in stomatology. In this article, we summarized the stress distributions of all-ceramic crowns, post crowns, fixed partial dentures and implant support fixed dentures; and with the use of finite element method, we investigated the stress levels of the periodontal ligament of abutment. The results showed: the tensile stress and compressive stress concentrated at the cervical margin of all-ceramic crown and post crown; the stress at the surface of the crown was the highest; the stress concentration exhibited at the connector of fixed parital denture, the molar was an ideal abutment tooth for the fixed bridge; the largest stress appeared around the neck of the implant abutment. These results have provided a theoretical basis for clinical dentistry in terms of restoration design and manufacture. It is suggested that clinical dentists should be careful to avoid the horizontal laoding applied on the prostheses so as to improve the resistance of abutment tooth to fracture.
Crowns ; trends ; Dental Stress Analysis ; Denture, Partial, Fixed ; trends ; Humans ; Principal Component Analysis ; Prosthodontics ; methods ; Tooth Preparation, Prosthodontic ; methods ; trends

OBJECTIVETo determine the infinite optical thickness of dentine porcelain of IPS E.max A color series.

METHODSCylindrical dentine porcelain specimens of the IPS E.max A color series were prepared with a diameter of 13 mm and thickness of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 mm. The chromatic value of all the specimens was determined with CM-5 spectrometer against standard black and white background. The chromatic aberration (deltaE) was calculated by regression equation.

RESULTSThe infinite optical thickness of dentine porcelain of the IPS E.max A color series ranged from 2.341 to 3.333 mm for a deltaE of 1.0, and from 2.064 to 2.904 mm for a deltaE of 1.5. As the chromaticity or thickness increased, the influence by the background color decreased, and the color of specimens became gradually close to the intrinsic color.

CONCLUSIONThe thickness of the background dentine porcelain specimens must exceed its infinite optical thickness to represent the intrinsic color and avoid the influence by the extrinsic color.

Coated Materials, Biocompatible ; chemistry ; Crowns ; Dental Porcelain ; chemistry ; Dental Prosthesis Design ; Humans ; Prosthesis Coloring ; Tooth Preparation, Prosthodontic ; methods

OBJECTIVETo evaluate the clinical application value of minimal prepared ceramic veneer in anterior teeth, by analyzing the esthetic effects and success rates.

METHODSForty-four anterior teeth in 30 patients with minor esthetic defect were included in this study. Less than 0.5 mm preparation or no preparaion technique was used in the clinical procedure. Glass ceramics veneers were delivered and 3M Relyx Veneer were used as the adhesive. The final appearance of each restoration was evaluated by patients on visual analogue scales (VAS) and by professional prosthodontists. Evaluation criteria included margin effects, color, shape and translucency. The success rate of all the restoration were analyzed in 6, 12 and 24 month after the treatment.

RESULTSThe patients' degree of satisfaction was 9.2 ± 0.4, while the excellent rate of esthetic effect of margin effect, color, shape and translucency was 89% (39/44), 91% (40/44), 98% (43/44) and 93% (41/44) by professional prosthodontist. The success rate of 6, 12 and 24 month were 100% (44/44), 98% (43/44) and 91% (40/44).

CONCLUSIONSThe minimal prepared venneers have a good esthetic effect and a satisfactory success rate, and is a suitable technique in esthetic treatment under the critical indications.

Ceramics ; Dental Restoration, Permanent ; methods ; Dental Veneers ; Esthetics, Dental ; Humans ; Incisor ; Patient Satisfaction ; Tooth Abnormalities ; therapy ; Tooth Preparation, Prosthodontic ; methods ; Tooth Wear ; therapy

OBJECTIVETo measure the cutting forces applied by clinicians during preparing full crown and to provide basic data for the training of dentistry in a virtual reality.

METHODSEach of six prosthodontists and six dental students prepared three extracted maxillary premolars. The cutting forces were measured with a three-dimensional transducer unit. Differences in cutting time and forces between groups were analyzed with independent-samples t-test.

RESULTSThe cutting forces varied in the range from 0.10 N to 4.90 N. The average cutting force (1.71 N) of four axial surfaces was higher than that (0.45 N) of occlusal surface (including functional cusp inclines) (P < 0.01). The cutting time by prosthodontists was shorter than that by the students (P < 0.05). Moreover, the vertical component of the cutting force was higher than the horizontal one (P < 0.01).

CONCLUSIONSThe magnitude of cutting forces could be greatly influenced by the motion direction and tendency of the handpiece. The data on cutting forces might serve as the foundation of cutting simulation algorithm for training in a virtual reality.

Adolescent ; Adult ; Child ; Crowns ; Dentists ; Female ; Humans ; In Vitro Techniques ; Male ; Stress, Mechanical ; Students, Dental ; Tooth Preparation, Prosthodontic ; instrumentation ; methods ; Transducers ; Young Adult