Mohamed S. Omar, Karim Rabie And Shereen Amin,
ABSTRACT
Statement Of The Problem: During Delivery Of All Ceramic Restorations, Clinical Adjustments Through Grinding By Diamond Burs Are Needed When The Restoration Exhibits Premature Occlusal Contacts And/or Inadequate Contours, Consequently Removing The Superficial Glazing Layer. The Efficacy Of Ceramic Polishing Systems Is A Controversial Issue In Literature.
Purpose: The Purpose Of This In Vitro Study Was To Evaluate The Effect Of Reglazing And Polishing After Simulated Clinical Adjustment On The Color Change And Translucency Of Translucent Monolithic Zirconia.
Materials and Methods: Thirty Disks Were Milled From Bruxzir Anterior Zirconia Then Glazed And Divided Into 3 Groups (n=10). Glazed-Group (G) Samples (n=10) Were Set Aside And Served As Controls. Reglazed-Group (RG) Samples (n=10) Were Ground Using The Manufacture Recommended Adjustment Kit Then Reglazed. Polished-Group (P) Samples (n=10) Were Ground Then Polished. All Test Samples (n=30) Were Subjected To Spectrophotometric Analyses Of Color Change (?E) And Translucency. A Representative Sample Was Randomly Selected From Each Group And Subjected To Xray Diffraction Crystallography, Surface Gloss Measurement And Scanning Electron Microscope Imaging. Mann-Whitney U Test Was Used To Analyze Color Change Data, One-way ANOVA Test Was Used To Analyze Translucency Parameter Data And Tukey?s Post-hoc Test Was Used For Pairwise Comparison When ANOVA Test Is Significant(�=0.05).
Results: Group (RG) Showed Statistically Significantly Lower Mean ?E (1.11� 0.72) Than Group (P) (3.23 � 0.25). Pair-wise Comparisons Between The Groups Revealed That Group (P) Showed The Highest Statistically Significant Mean TP (10.7 � 0.64), While There Was No Statistically Significant Difference Between Group (G) (8.54 � 0.67) And Group (RG) (9.03 � 0.39). Group (G) Showed The Highest Surface Gloss (62.3 GU), While Group (P) Showed The Lowest Surface Gloss (50.6 GU). XRD Analyses Revealed That Adjustment Procedures Initiated A Monoclinic Transformation Resulting In A Monoclinic Crystal Content Of 41 %. While, Reglazing Caused A Reversal Of Monoclinic Transformation And A Monoclinic Crystal Content Comparable To That Of The Control Group.
Conclusion: Chair-side Polishing Resulted In A Statistically Significant And Clinically Perceivable Color Change And Clinically Perceivable Increase In The Translucency. However, Polishing Significantly Decreased The Surface Gloss Of The Tested Zirconia Specimens. Reglazed Zirconia Showed A Reversal Of Monoclinic Transformation. The Tested Brand Of Translucent Monolithic Zirconia Couldn?t Emulate The Known Values Of Translucency Of Enamel And Dentin Of Equal Thickness.
CLINICAL IMPLICATIONS: Reglazing Is Recommended To Attain Restorations With Less Color Change, Higher Gloss, Less Perceivable Change In Translucency And To Reverse Any Crystalline Phase Transformation Caused By Chair-side Adjustments.
