Shear bond strength of porcelain to milled and stereolithography additively manufactured zirconia with and without surface treatment: An in vitro study

Elsevier

Available online 15 March 2023

The Journal of Prosthetic DentistryAuthor links open overlay panel, , , , , AbstractStatement of problem

Delamination of veneering ceramic is one of the most common challenges relating to veneered zirconia restorations. Additive manufacturing (AM) is a fast-expanding technology that has gained widespread acceptance in dentistry and is increasingly being used to produce dental restorations. However, information about bonding of porcelain to AM zirconia is lacking.

Purpose

The purpose of this in vitro study was to investigate the shear bond strength (SBS) of porcelain to milled and additively manufactured zirconia, and the effect of surface treatment on bond strength.

Material and methods

A Ø12×5-mm disk was designed virtually to fabricate all specimens, which were divided into 2 groups according to the manufacturing technique: additively manufactured or milled zirconia. The effect of airborne-particle abrasion and a zirconia liner before porcelain application was investigated in both groups. Veneering porcelain was fired into an alumina ring mold on the zirconia surface. SBS was measured by using a universal testing machine at a crosshead speed of 1 mm/min before and after aging (n=10). SBS data were analyzed with 3-way ANOVA (α=.05)

Results

A significant difference was found between milled and AM zirconia. The SBS of porcelain to milled zirconia was significantly higher (1.38 MPa) than to AM zirconia (0.68 MPa) (P<.001). The surface treatment of zirconia had no significant effect on porcelain SBS in either group (P=.254), whereas thermocycling significantly reduced the SBS of porcelain to zirconia in both milled and AM groups (P=.001).

Conclusions

Porcelain bonding to milled zirconia was better than to AM zirconia. Pretreating the zirconia substrate before porcelain application did not improve the porcelain bond.

Section snippetsMaterial and methods

Means and standard deviations obtained from a previous study were used to calculate sample size.48 Assuming an alpha value of .05 and 80% power, the estimated sample size was 9 samples/group. For this study, 10 samples/group were used. A Ø12×5-mm disk was designed using a CAD program (Geomagic freeform; 3D System), and the design was exported as a standard tessellation language (STL) file for the production of zirconia specimens. Specimens were divided into 2 groups: milled zirconia (n=20) and

Results

The means and standard deviations of the SBS values for different tested groups are presented in Table 2. Factorial ANOVA demonstrated that treatment was not a significant factor in the SBS of porcelain to zirconia (P=.254), while the manufacturing technique (P<.001) and thermocycling (P=.001) had a significant effect (Fig. 2). The post hoc Tukey test with 95% confidence interval showed a significant difference between milled and AM zirconia with a mean of 1.38 MPa for milled zirconia and 0.65

Discussion

A significant difference was found in the SBS of porcelain to milled and AM zirconia. Therefore, the first null hypothesis was rejected. However, the zirconia surface treatment did not significantly change the SBS of porcelain to milled and AM zirconia. Therefore, the second null hypothesis was not rejected.

Milled zirconia presented with the highest SBS to porcelain. Surface roughness may contribute to higher SBS.27 Zandinejad et al49 measured the surface roughness of milled versus AM zirconia

Conclusions

Based on the findings of this in vitro study, the following conclusions were drawn:

1.

Milled zirconia exhibited significantly higher SBS when compared with AM zirconia.

2.

Surface treatments including airborne-particle abrasion and the use of liner did not significantly increase the porcelain bond to milled or AM zirconia; however, thermocycling reduced the SBS of porcelain to zirconia in milled and 3D-printed groups.

CRediT authorship contribution statement

Amirali Zandinejad: Conceptualization, Supervision, Validation, Project administration, Writing – original draft, Writing – review & editing. Leila Nasiry Khanlar: Investigation, Methodology, Writing – review & editing. Abdul Basir Barmak: Statistics, Formal analysis. Masaomi Ikeda: Validation, Visualization, Supervision. Junji Tagami: Conceptualization, Resources. Radi Masri: Conceptualization, Validation, Writing – review & editing.

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© 2023 by the Editorial Council for The Journal of Prosthetic Dentistry.

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