| Background: Nowadays,all-porcelain crowns are recognized as restorations with good long-term performance.Dental ceramics have been successfully used in the restoration of anterior and posterior teeth because of their good aesthetic properties,good biocompatibility and durable mechanical properties.However,the long-term survival rate of the prosthesis is not only related to the material,biocompatibility and mechanical properties of the material,but also related to the fitness of the prosthesis itself.Therefore,the accuracy of the impression is crucial to the production of an accurate and tight prosthesis.In the traditional impression method,although the elastic impression materials(such as polyether and polyethylsiloxane)have sufficient accuracy and stability,there are also bubbles or breakage in important areas,and the polymerization problems caused by insufficient material mixing,resulting in the final restoration is not tight.In view of the shortcomings,Japanese scholars took the lead in the use of a single tooth tray combined with finished pallet silicone rubber impression method to obtain accurate impression.This method does not require clinical mechanical gingival removal,and can obtain the shape of gingival crevicular,which improves the suitability of the prosthesis.Therefore,it is unanimously recommended by doctors in clinical practice.At the same time,with the introduction of digital impression of computer aided design and computer aided manufacturing(CAD/CAM)into the concept of dental treatment,the acquisition of digital model at the side of the chair or in the technician’s room and the manufacture of prostheses has become widely used in clinical practice due to its standardization and repeatability,high cost efficiency and high quality.Objective:In this study,the direct digital impression method,the individual tooth tray combined with the finished tray silicone rubber impression method were applied to the all-porcelain restoration of tooth defects/dentition defects.After the restoration,the clinical effect of the restoration was evaluated according to the improved USPHS evaluation criteria after regular follow-up observation.In addition,the relative software is used to measure the fixed point position widths of the two impression methods.After statistical analysis of the obtained data,the accuracy difference of the two impression methods is compared.Materials and Methods: Ten patients with dental defects/dentition defects who received zirconia all-ceramic crown/bridge restoration in Dalian Department of Prosthodontics from September 2019 to September2020 were included in this study(1 male and 9 female;A total of 22 prostheses were obtained from 29 abutments.Among them,a total of 6 cases(involving 13 abutments and 11 prostheses)were directly digitized impression made with 3Shape Trios 3-mouth scanner and completed the final restoration.A total of 4 cases(16 abutments and 11 prostheses were involved)were imprinted by the method of one-tooth tray combined with finished pallet silicone rubber impression and the final restoration was completed.The finished prostheses were tried on,adjusted,polished and bonded in the mouth to complete the restoration.Follow-up observation was conducted for 3-15 months after repair,and the clinical effect was evaluated according to the modified self-USPHS evaluation criteria.Direct digital impression and traditional impression were made in all cases,and the latter was transformed into indirect digital impression.3SHAPE software was used to measure and record the fixed point position width of the direct digital impression(direct set)and indirect digital impression(indirect set)on the same abudent and the same shoulder.SPSS26.0 statistical software was used to conduct t test for the measured data(α=0.05).Analyze and compare the difference of impression accuracy obtained by two impression methods.Results: In this study,all the 10 cases of all-porcelain crown/bridge repair were revisited on schedule without loss of follow-up,and the followup rate was 100%.After 3-15 months of follow-up observation,29 abutments from 22 prostheses were evaluated.Among the evaluation of gingival health,1 abutment was rated as Grade B,and 2 abutments were rated as Grade C.In addition,all the evaluation indexes were A grade,and good clinical repair effect was obtained.The fixed point width of the direct group was 0.8976±0.11mm(mean ±standard deviation),and the fixed point width of the indirect group was0.8466±0.12mm(mean ± standard deviation).The statistical software SPSS26.0 was used to carry out t test on the measured fixed point width data of the impression shoulder between the two groups,and the analysis results showed no statistical significance(P>0.05).Conclusion: The application of digital direct impression method and single-tooth tray silicone rubber impression method to make all-ceramic crown/bridge to repair dental defects/dentition defects can achieve good short-term clinical effects.The accuracy of the two impression methods is similar. |
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