Mai S. Elgohary, Hesham Abd El Megid Katamish And Maha A. Taymour,

ABSTRACT
Statement Of The Problem: Long-term Clinical Success Of Dental Restoration Is Influenced Not Only By Mechanical Property, Aesthetic Quality, And Biocompatibility, But Also By Marginal Accuracy. Large Marginal Gap Causes Failure Of A Crown By Dissolving Dental Cement So Plaque Can Easily Accumulate, Leading To Marginal Leakage And Secondary Caries. Factors Such As Type Of Finish Line Design And Thickness May Influence The Marginal Adaptation Of All Ceramic Crown Restoration.

Purpose: The Purpose Of This Study Was To Evaluate And Compare Marginal Accuracy In Anterior Single Crowns Having Different Finish Line Thicknesses Constructed From Two Types Of All-ceramic Restorations Made From Lithium Disilicate Glass Ceramic And Anterior Zirconia Using CAD/CAM Fabrication Technique.

Materials and Methods: Thirty-two Zirconia-based Bruxzir Anterior (Glidwell Dental Labs, Prismatik DentalCraft Inc. USA) And Lithium Disilicate Crowns IPS E.max CAD (IvoclarVivadent Gmbh, Burs, Austria), 16 Each, Were Fabricated With CAD/CAM Systems On A Specially Designed Stainless-steel Die To Ensure The Standardization Of Specimen Shape And Dimensions. The Marginal Accuracy For All Tested Crowns Was Evaluated By Using A Stereomicroscope (Nikon Eclips E600, Tokyo, Japan) Connected With An IBM Compatible Personal Computer Using A Fixed Magnification Of 45X., A Digital Image Analysis System (Image J 1.43U, National Institute Of Health, USA) Was Used To Measure And Qualitatively Evaluate The Gap Width. Then The Data Obtained Were Collected, Tabulated And Then Subjected To Statistical Analysis.

Results: Results Of This Study Showed That Finish Line Thickness Regardless To The Material Used Did Not Significantly Affect The Marginal Accuracy. And The Material Has Influence On Marginal Accuracy. A Value Of P < 0.05 Was Considered Statistically Significant, Two -way Analysis Of Variance Was Performed. Student T-test Was Done For Compared Pairs. Sample Size (n=8) Was Large Enough To Detect Large Effect Sizes For Main Effects And Pair-wise Comparisons, With The Satisfactory Level Of Power Set At 80% And A 95% Confidence Level.

Conclusions: More Conservative Preparation Of A Shallow Chamfer Has Similar Marginal Fit As Teeth With The Conventional Preparation For Both Ceramic Types Tested.