Fracture Resistance and Surface Roughness of Zirconia Crowns Veneered by Layering, Press-on, and CAD-on Methods

Mohaghegh, Mina; Pourzarabi, Dorsa; Taghva, Masumeh; Derafshi, Reza

doi:10.30476/dentjods.2025.105198.2579

Fracture Resistance and Surface Roughness of Zirconia Crowns Veneered by Layering, Press-on, and CAD-on Methods

Document Type : Original Article

Authors

Mina Mohaghegh ¹

Dorsa Pourzarabi ²

Masumeh Taghva ³

Reza Derafshi ³

¹ Dept. of Prosthodontics, Biomaterials Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.

² Student, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.

³ Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.

https://doi.org/10.30476/dentjods.2025.105198.2579

Abstract

Background: Various strategies are used for ceramic veneering on zirconia copings. Veneering techniques may influence the fracture resistance and surface roughness of zirconia crowns and controversial results are present in literature concerning these techniques.
Purpose: The aim of the present study was to investigate the effects of layering, press-on, and CAD-on techniques on the fracture resistance and surface roughness of zirconia crowns after aging.
Materials and Method: In this in vitro study, 30 brass dies were milled and scanned. Coping was designed for all of them, milled from a zirconia block, and sintered. Porcelain veneering was done through layering, press-on, and CAD-on methods (n=10 per group), and aged in autoclave. Surface roughness was measured before and after aging. Fracture resistance was tested, and the failure pattern was checked by scanning electron microscopy (200-500×). The independent t-test and post-hoc test were used to compare the fracture resistance among the three groups. The surface roughness before and after aging was investigated using one-way ANOVA and ANCOVA. The data on failure patterns were analyzed using the chi-square test.
Results: The mean fracture resistance in the CAD-on group (4442.19±1580.62 N) was higher than in layering (3225.63±1266.08 N) and press-on groups (2652.42±1320.02 N). The press-on group exhibited the highest surface roughness both before (2.97±0.26μm) and after aging (3.33±0.83μm). The most common failure patterns were adhesive pattern in the CAD-on group and cohesive pattern in layering and press-on groups.
Conclusion: The three veneering techniques had clinically acceptable fracture resistance and surface roughness. The highest fracture resistance was found in the CAD-on group, followed by the layering and press-on groups. The lowest surface roughness was observed in the layering group, followed by CAD-on and press-on groups. Techniques with higher fracture resistance can be considered in patients with high force factors such as bruxism, clenching, and long span bridges.

Keywords

CAD-on

Fracture resistance

Layering

Press-on

Surface roughness

Zirconia

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