EFFECT OF SURFACE ABRASION AND TEMPERATURE TREATMENT ON METASTABLE TETRAGONAL ZIRCONIUM DIOXIDE (X-ray diffraction phase analysis)

Abstract

Background. Zirconium dioxide is widely used in prosthodontics due to its strength and biocompatibility. However, a major drawback is its susceptibility to breakage and the tendency for porcelain layers to delaminate or chip(1). The durability and mechanical properties of zirconium dioxide can vary significantly based on the fabrication process, specifically regarding abrasive blasting and regenerative firing(2)(3). There is considerable debate among manufacturers and technicians about the best practices for these processes(4).

Aim. The study aimed to determine the effects of sandblasting and diamond bur abrasive treatment on the hardness and phase state of yttrium-stabilized tetragonal zirconium dioxide (Y-TZP). Evaluate the outcomes and appropriateness of regenerative firing.

Methods. An experimental study was conducted using synthesized ZrO2 stabilized with Y2O3 (Y-TZP). The samples were divided into five groups:

- Sandblasted without subsequent regeneration firing.

- Sandblasted followed by regeneration firing.

- Abrasive blasting with a diamond bur without additional firing.

- Treated with both diamond bur abrasive blasting and regeneration firing.

- Control group with no mechanical or thermal treatments.

A total of 80 pre-sintered Y-TZP blocks were milled and fired. Fifty defect-free samples were selected and treated according to the group protocols. The samples underwent X-ray diffraction phase analysis to assess the phase composition and structural changes. Statistical analysis was performed using TIBCO Statistica v13 and ANOVA Origin statistical package.

Results. X-ray diffraction phase analysis revealed that:

Sandblasting increased monoclinic phases to 8% compared to 0.1% in control samples.
Regeneration firing post-sandblasting reduced monoclinic phases to 1.5%.
Diamond bur treatment increased monoclinic phases to 3%.
Regeneration firing after diamond bur treatment restored monoclinic phases to the original 0.1%.
Conclusions. The study demonstrated that sandblasting significantly increases monoclinic phases in Y-TZP, while regeneration firing effectively reduces these phases. Diamond bur treatment also increases monoclinic phases, but regeneration firing can fully restore the material's original phase state. These findings highlight the importance of selecting appropriate fabrication techniques to optimize the mechanical properties and durability of zirconium dioxide in prosthodontic applications.