Abstract
Microleakage can be related to margin misfit. Also, traditional microleakage techniques are time-consuming. This study evaluated the existence of correlation between in vitro margin fit and a new microleakage technique for complete crowns cemented with 3 different luting agents. Thirty human premolars were prepared for full-coverage crowns with a convergence angle of 6 degrees, chamfer margin of 1.2 mm circumferentially, and occlusal reduction of 1.5 mm. Ni-Cr cast crowns were cemented with either zinc phosphate (ZP) (S.S. White), resin-modified glass-ionomer (RMGI) (Rely X Luting Cement) or a resin-based luting agent (RC) (Enforce). Margin fit (seating discrepancy and margin gap) was evaluated according to criteria in the literature under microscope with 0.001 mm accuracy. After thermal cycling, crowns were longitudinally sectioned and microleakage scores at tooth-cement interface were obtained and recorded at x100 magnification. Margin fit parameters were compared with the one-way ANOVA test and microleakage scores with Kruskal-Wallis and Dunn's tests (α=0.05). Correlation between margin fit and microleakage was analyzed with the Spearman's test (α=0.05). Seating discrepancy and marginal gap values ranged from 81.82 μm to 137.22 μm (p=0.117), and from 75.42 μm to 78.49 μm (p=0.940), respectively. Marginal microleakage scores were ZP=3.02, RMGI=0.35 and RC=0.12 (p<0.001), with no differences between RMGI and RC scores. The correlation coefficient values ranged from -0.27 to 0.30 (p>0.05). Conclusion: Margin fit parameters and microleakage showed no strong correlations; cast crowns cemented with RMGI and RC had lower microleakage scores than ZP cement.
Highlights
The margin fit of prosthetic crowns has always been a concern for clinicians . 2,3,6-9,11,16-18,21,24,30,33,34,37 Misfit at cementation[38] results in open margins, increasing the risk of recurrent caries, plaque accumulation and periodontal disease
One hypothesis is that the greater solubility of this cement accelerates the chemical dissolution process[15]. Even with this disadvantage, clinical reports show positive survival rates for complete crowns luted with zinc phosphate cement[10,19,29,35,41]
Measurement techniques and the descriptive terminology of fit for complete crowns varies among the investigators . 2,3,6-9,11,16-18,21,24,30,33,34 Criteria proposed by Holmes, et al.[14] are useful for determining the seating discrepancy and margin gap values
Summary
The margin fit of prosthetic crowns has always been a concern for clinicians . 2,3,6-9,11,16-18,21,24,30,33,34,37 Misfit at cementation[38] results in open margins, increasing the risk of recurrent caries, plaque accumulation and periodontal disease. Microleakage can be related to margin misfit, no strong correlation between margin fit and microleakage scores in complete crowns has been demonstrated. Zinc phosphate cement presents higher in vitro microleakage scores when compared to ionomeric and resin luting agents. One hypothesis is that the greater solubility of this cement accelerates the chemical dissolution process[15]. Even with this disadvantage, clinical reports show positive survival rates for complete crowns luted with zinc phosphate cement[10,19,29,35,41]. Resin or resin-modified glass ionomer cements have shown lower in vitro microleakage values; the long-term in vivo survival rate has not yet been published[27]
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