الفهرس 
Clinical Performance Of Lithium Disilicate Crowns Restoring Endodontically Treated Teeth With Two Occlusal Preparation Schemes : (Randomized Clinical Trial)
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Abstract
The completion of root canal treatment does not mean the end of patient management. The restoration of the tooth back to normal is the actual goal and challenge at the same time. The main aim is to protect the weakened teeth from future failure, which is achieved with the help of a well- fitted restoration. For many years, studies have focused their attention on different aspects for the restoration of endodontically treated teeth, however, very few studies focused on the effect of occlusal preparation. Tooth preparation is considered a fundamental step for the success of any tooth-supported fixed restoration. The designs of tooth preparation can affect the success of the crown restoration.
Previous studies accepted the use of planar occlusal design for restoration of endodontically treated teeth. Also, flat occlusal design provided better qualitative and quantitative stress distribution when compared to an anatomically prepared surface. On the other hand, choosing the material according to its properties, affects the prognosis of the final restoration.
Forty crowns were fabricated for the restoration of posterior molar teeth. Scaling and polishing and shade selection were performed for all the participants in the study prior to preparation.
The patients were divided into two groups according to the employed occlusal preparation design. group PO (control group) represented the planar occlusal design and group FO (intervention group) represented the flat occlusal design. Deep chamfer finish line was placed supra-gingivally for all restored teeth.
Final impression was taken followed by temporization. The try-in was carried out using PMMA crowns. Fabrication of the try-in crowns, as well as the final crowns was performed by CAD/CAM technology. The final restoration was bonded using self-adhesive resin cement.
The clinical performance was determined using USPHS criteria and follow-up visits were carried out every 3, 6, 9 and 12 months.
Qualitative data were presented as frequencies and percentages. Chi-square or Fisher’s Exact test were used to compare between the two groups. Friedman’s test was used to study the changes by time within each group. Numerical data were explored for normality by checking the distribution of data and using tests of normality (Kolmogorov-Smirnov and Shapiro-Wilk tests).
Data were presented as mean and standard deviation (SD) values. Student’s t-test was used to compare between mean age values in the two groups. The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp.
There was no statistically significant difference between both groups regarding the tested outcomes as all groups recorded Alpha scores except few Bravo scores for the marginal discoloration outcome.
This indicated that both preparation designs are clinically acceptable in terms of their clinical performance over a period of one year.