الفهرس 
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Abstract
Objectives : The objectives of this in-Vitro study are to assess the impact of rotary preparation finishing versus ultrasonic preparation finishing on the marginal gap, internal fit and microleakage of anterior ceramic laminate veneers (CLV). Materials and methods Twenty-eight natural upper central incisors extracted for periodontal reasons were collected, then teeth were allocated in two groups of 14 teeth each. Based on the size of diamond coating of high-speed rotary taper with round end stones used for CLVs preparation, the first group was prepared by green coded stones (G), while the second group was prepared by blue coded stones (B) then, further subdivided into 4 groups of 7 specimens each according to method of finishing of the preparation either by using rotary red coded stones or by using ultrasonic diamond coated tip: GR,GU,BR,BU. Standardized reduction was done by putty index and depth cutters, butt-joint preparation design was implemented with minimal preparation parameters. Finishing of preparation was done by a high-speed rotary red coded taper with round end stone for GR, BR groups, and factory calibrated- diamond coated PM2 ultrasonic tip, with adjusted vibration amplitude and water flow for GU, BU groups. CLVs were fabricated from IPS e.max CAD blocks, and cementation was done by light-cured resin cement. Marginal gap measurement was done along all CLV margins before and after cementation using a stereo microscope, then specimens were placed in a thermocycler and embedded in 2% methylene blue dye, then washed and embedded in clear acrylic resin blocks then sectioned vertically and horizontally to provide 4 sections for each specimen to be examined under stereo microscope. Measurement of marginal gap (MG), internal fit (IF) and microleakage (ML) were done using a picture analysis software. Statistical analysis; testing data normality using Shapiro-Wilk test. All tests were 2 tailed, student-t test was used for parametric quantitative variables, to compare between two studied groups and Paired t test for comparison between pre and post treatment. Mann Whitney test was used for nonparametric quantitative variables. Two Way ANOVA test was used for studying the effect of combination between different factors on continuous parametric outcome. Results No significant difference was found in MG, IF and ML of CLVs when using green or blue coded taper with round end stones for bulk reduction, also no significant difference was found in MG, IF and ML of CLVs when using rotary or ultrasonic preparation finishing modalities. Conclusion it was concluded that: Marginal gap and internal fit values of CLVs with rotary and ultrasonic preparation finishing, were within the clinical acceptable range. Technique of preparation finishing, rotary versus ultrasonic had comparable effect on marginal gap, internal fit and microleakage of ceramic laminate veneers. The use of coarse grit diamond stone or medium grit diamond stone for bulk tooth reduction, neither affected the marginal gap, internal fit and microleakage of ceramic laminate veneers.