Abstract
A polymer-infiltrated ceramic network (PICN) material has recently been introduced for dental use and evidence is developing regarding the fit accuracy of such crowns with different preparation designs. The aim of this in vitro study was to evaluate the precision of fit of machined monolithic PICN single crowns in comparison to lithium disilicate crowns in terms of marginal gap, internal gap, and absolute marginal discrepancies. A secondary aim was to assess the effect of finish line configuration on the fit accuracy of crowns made from the two materials. Two master metal dies were used to create forty stone dies, with twenty each for the two finish lines, shoulder and chamfer. The stone dies were scanned to produce virtual models, on which ceramic crowns were designed and milled, with ten each for the four material–finish line combinations (n = 10). Marginal gaps and absolute marginal discrepancies were evaluated at six pre-determined margin locations, and the internal gap was measured at 60 designated points using a stereomicroscope-based digital image analysis system. The influence of the material and finish line on the marginal and internal adaptation of crowns was assessed by analyzing the data using two-way analysis of variance (ANOVA), non-parametric, and Bonferroni multiple comparison post-hoc tests (α = 0.05). ANOVA revealed that the differences in the marginal gaps and the absolute marginal discrepancies between the two materials were significant (p < 0.05), but that those the finish line effect and the interaction were not significant (p > 0.05). Using the Mann–Whitney U test, the differences in IG for ‘material’ and ‘finish line’ were not found to be significant (p > 0.05). In conclusion, the finish line configuration did not seem to affect the marginal and internal adaptation of PICN and lithium disilicate crowns. The marginal gap of PICN crowns was below the clinically acceptable threshold of 120 µm.
Highlights
Flexible resin matrix ceramic (RMC) materials have recently been introduced in dentistry for the computer-aided design/computer-aided manufacturing (CAD/CAM) fabrication of fixed indirect restorations, including single-tooth complete coverage crowns [1,2]
The polymer-infiltrated ceramic network (PICN) materials are a class of RMCs made up of a porous ceramic scaffolds infused with a mixture of urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) polymers [2,3,4,5]
Using two-way analysis of variance (ANOVA), the difference in MG and AMD between PICN and LDS crowns was found to be significant (p < 0.05) (Table 2), the non-parametric Mann–Whitney U test showed that the differences in IG between the two materials were not significant (p = 0.253)
Summary
Flexible resin matrix ceramic (RMC) materials have recently been introduced in dentistry for the computer-aided design/computer-aided manufacturing (CAD/CAM) fabrication of fixed indirect restorations, including single-tooth complete coverage crowns [1,2]. RMCs are purportedly able to overcome the shortcomings of traditional ceramics in that they can be applied directly after milling without the need for additional processing steps, such as firing, sintering, and glazing [2,3,4]. These materials are designed to combine the favorable mechanical properties of ceramic and resin into one single material, with flexural strengths and elastic moduli matching or being close to the natural tooth structure [4,5]. Conclusive evidence on the effect of these variables on the precision of fit is still unavailable
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