Marginal adaptation of CAD/CAM zirconia-based crown during fabrication steps

Abstract

Background: Excessive marginal discrepancy of crowns favors the rate of cement dissolution and microleakage that may cause pulpal inflammation. Besides, it may increase plaque retention leading to the onset of periodontal disease. Therefore, this research was carried out to study the effect of fabrication stages and artificial aging on the marginal adaptation of CAD/CAM Zirconia-based crowns which have become increasingly popular among the patients due to their natural esthetics and excellent strength.Purpose: To evaluate the marginal adaptation of CAD/CAM Zirconia-based crowns on their respective prepared teeth during different fabrication stages namely; framework, after veneering, after crown cementation and after thermo-mechanical loading. Materials and methods: A total of twenty zirconia frameworks were fabricated using (Cercon smart ceramics, DeguDent, Germany) manufacturing system, conventionally veneered with (Cercon Ceram kiss, DENSPLY, Germany), cemented with conventional glass ionomer to their corresponding prepared human teeth. The cemented crowns were finally aged through a process of thermo-mechanical cyclic loading. The assessment of vertical marginal gap was performed on the prepared teeth using an optical microscope with image-j software analysis system at 40Â magnification for frameworks, for restorations before and after cementation then, after thermo-mechanical loading. Differences between the vertical gap during fabrication stages and the effect of artificial aging were statistically analyzed using a one-way analysis of variance ANOVA and Independent-samples T test. Results: In this study, the marginal gap increased after every tested stage. The vertical marginal gap recorded its smallest mean value (41.08 ± 3.23 mm) during core stage. A significant increase in the measurement of vertical marginal gap was observed after firing the veneering layer reaching (46.87 ± 3.94 mm). After cementation, the marginal gap was (46.87 ± 4.65 mm). Finally; thermo-mechanical loading corresponding to one year of clinical use was found to cause a significant increase the vertical marginal gap to record its highest value (56.73 ± 7.21 mm).

Vertical Marginal Gap Distance of CAD/CAM Milled BioHPP PEEK Coping Veneered by HIPC Compared to Zirconia Coping Veneered by CAD-On lithium disilicate “In-Vitro Study”

“…Although the critical temperature of zirconia aging suggested above 100°C. (El-Dessouky et al, 2015) Also a similar study done by Khaled et. Al to assess the effect of ageing on zirconia crowns using ROBOTA chewing simulator with 49 N chewing forces for 75000 cycles (6 months clinical condition), it was found that there is increase of marginal gap measurements after aging , from (31.41±5.9)µm to (95.28±9.2) µm of Bruxzir crowns.…”

Marginal Accuracy and Fracture Resistance of Posterior Crowns Fabricated from CAD/CAM PEEK Cores Veneered with HIPC or Nanohybrid Conventional Composite

“…52 The results of present study were agreed by El-Dessouky et al who showed that thermo-mechanical loading has significantly increased the marginal gap measurements when carried out in temperatures between 5°C and 55°C. 53 However, Wael et al assumed that the marginal discrepancies had no significant changes after artificial ageing. 54 However, all results of vertical marginal gap in this study were within the acceptable range.…”

Comparative Study Between Monolithic Translucent Zirconia (Y-TZP) and IPS Empress 2 in Marginal Fit and Fracture Strength

“…Other study was found, that, the thermomechanical loading increased the vertical marginal gap due to the luting cement. Some parts of the cement film were washed out during the aging procedures, particularly, when using water-soluble cement such as glass-ionomer (26) . On contrary, no significant effect on marginal discrepancy after aging was reported by others (27) .…”