Impact of multiple firings on thermal properties and bond strength of veneered zirconia restorations.

Hensel, Justine; Reise, Michael; Liebermann, Anja; Buser, Ramona; Stawarczyk, Bogna (2022). Impact of multiple firings on thermal properties and bond strength of veneered zirconia restorations. Journal of the mechanical behavior of biomedical materials, 128, p. 105134. Elsevier 10.1016/j.jmbbm.2022.105134

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OBJECTIVES

This investigation evaluated the impact of multiple firings during the veneering process of all-ceramic restorations on the thermal properties and bond strength between veneering ceramics and zirconia.

METHODS

For the measurements of the coefficient of thermal expansion (CTE) prismatic specimens of four different veneering ceramics (ZRT/ZRO/HFZ/STR; N = 40/n = 10 per veneering ceramic) and rod-shaped zirconia specimens (N = 2) were produced. 2 specimens of each veneering ceramic were fired 2, 4, 6, 8, and 10 times simulating dentine-firing. Measurements were performed in a dilatometer and glass transition temperature (Tg) was determined graphically. To analyze bond strength (BS), crack initiation test specimens were prepared using the same veneering ceramics and zirconia (N = 600/n = 150 per veneering ceramic). 30 specimens of each veneering ceramic were fired 2, 4, 6, 8, and 10 times. Half of them were thermocycled (5000 cycles, 5 °C/55 °C, 20s). The crack initiation test was conducted in a universal testing machine. Data was analyzed using ANOVA with partial eta squared statistics and post-hoc Scheffé test as well as Pearson correlation test.

RESULTS

CTE was mostly affected by the choice of veneering ceramic (p < 0.001/ηp2 = 0.983). For the leucite-free ceramic, the CTE values were in same value range (p = 0.171) along the number of firings. Tg was not influenced by the number of firings. The highest effect on BS showed veneering ceramics (p < 0.001/ηp2 = 0.055) followed by the number of firings (p = 0.011/ηp2 = 0.023). The global difference in BS was lower for 10 firings compared to 2 firings (p = 0.048). Highest BS were measured for the leucite-free veneering ceramic (ZRT). Artificial aging by thermocycling showed no impact on BS (p = 0.755). Correlations were found for HFZ between the BS and the CTE (r = -0.651/p = 0.021). A correlation between CTE and Tg was observed (r = 0.303/p = 0.029).

SIGNIFICANCE

Thermal stability seemed to be more predictable for leucite-free veneering ceramics with superior BS. All BS results exceeded the minimum clinical requirements.

Item Type:

Journal Article (Original Article)

UniBE Contributor:

Buser, Ramona

ISSN:

1878-0180

Publisher:

Elsevier

Language:

English

Submitter:

Pubmed Import

Date Deposited:

24 Feb 2022 10:08

Last Modified:

10 Mar 2022 00:14

Publisher DOI:

10.1016/j.jmbbm.2022.105134

PubMed ID:

35196634

Uncontrolled Keywords:

All-ceramic restoration Bond strength Coefficient of thermal expansion Glass transition temperature Leucite ceramic Multiple firings Thermal properties Veneering ceramics

BORIS DOI:

10.48350/165973

URI:

https://boris.unibe.ch/id/eprint/165973

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