In Vitro Study of Comparative Evaluation of Marginal and Internal Fit between Heat-Pressed and CAD-CAM Monolithic Glass-Ceramic Restorations after Thermal Aging.

Roxana-Diana Vasiliu,Liliana Porojan,Sorin Daniel Porojan

doi:10.3390/ma13194239

Abstract

The accuracy of newly developed ceramic materials is still being studied. Marginal and internal adaptation are known factors that have an essential impact on the long term success of dental restorations. The aim of this in vitro study was to evaluate the marginal and internal fit of heat-pressed and milled monolithic glass-ceramic restorations based on their ceramic type, processing technique, and in vitro thermocycling. Thirty-two crowns were studied and divided into four groups (n = 8), according to the ceramic material (feldspathic glass-ceramic (F) and zirconia reinforced lithium silicate glass-ceramic (ZLS)) and to their technological obtaining processes (milling (M) and heat-pressing (P)). A typodont preparation was scanned with a D2000 3D scanner to obtain identical 32 resin 3D-printed abutment teeth. Marginal and internal gaps were measured using the silicone replica technique under 40× magnification. The crowns were further cemented and thermally aged for 10,000 cycles After cementation and thermocycling of the samples, marginal and internal gaps were assessed using micro-CT (micro-computed tomography)) analysis. Data were statistically analyzed using statistical tests. Significant differences were found before and after cementation and thermocycling among the tested materials (p < 0.05). Related to technological processing, significant differences were seen in the marginal area between FP and FM (p < 0.05) Significant differences were also found in the axial and occlusal areas between the ZLSP and ZLSM. Thermocycling and cementation did not have a significant effect on the tested materials (p < 0.05). The technological processes influenced the marginal and internal fit of the crowns in favor of the CAD/CAM (computer aided design/computer aided manufacturing)technologies. Thermal aging had little effect on marginal adaptability; it increased the values for all the tested samples in a small way, but the values remained in their clinically acceptable range for all of the crowns.

Highlights

The adaptability of the crowns, along with esthetics and fracture resistance, are essential factors in controlling the long-term success of restorations [1,2,3,4,5,6,7,8,9,10]
The aim of this in vitro study was to evaluate the marginal and internal fit of heat-pressed and milled monolithic glass-ceramic restorations based on their ceramic type, processing technique, and in vitro thermocycling
Significant differences were seen in the marginal area between FP and FM (p < 0.05) Significant differences were found in the axial and occlusal areas between the ZLSP and ZLSM

Summary

Introduction

The adaptability of the crowns, along with esthetics and fracture resistance, are essential factors in controlling the long-term success of restorations [1,2,3,4,5,6,7,8,9,10]. Crown adaptation is defined by the marginal and internal gaps [12]. The marginal gap term can be defined as the space between the crown and the preparation line. There can be inner gaps, defined as the space between the inner part of the restoration and the dental structure, while the discrepancy at the edge is named the marginal demarcation gap [14]. These gaps appear as a result of morphological disproportion between the tooth and the restoration. Sorensen et al classified these methods into four categories: direct observation; cross-sectional method, impression method, and using an explorer [22]

Methods

Discussion

Conclusion