A discriminatory mechanical testing performance indicator protocol for hand-mixed glass-ionomer restoratives

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Materials Science

Background:

• Glass-ionomer (GI) restorative materials are widely used in dentistry.
• Ensuring the quality and performance of hand-mixed GIs is crucial for clinical success.
• Standardized mechanical testing is needed to assess GI restorative performance.

Purpose of the Study:

• To establish a reproducible and discriminatory mechanical testing method for hand-mixed glass-ionomer (GI) restoratives.
• To identify a reliable performance indicator for GI materials.
• To compare the efficacy of different mechanical testing approaches.

Main Methods:

• Cylindrical and bar-shaped specimens of hand-mixed GI were prepared with varying powder:liquid ratios.
• Mechanical properties including compressive fracture strength (CFS), compressive modulus (CM), three-point flexure strength (TFS), tensile flexural modulus (TFM), biaxial flexure strength (BFS), and Hertzian indentation (HI) were evaluated.
• Statistical analysis, coefficient of variation (CoV), Weibull analysis, and fractography were employed.

Main Results:

• A progressive linear deterioration in CFS, CM, and TFM was observed with reduced powder content.
• TFS, BFS, and HI showed no significant linear deterioration with altered mixing ratios.
• CoV and Weibull analyses revealed distinct performance regions for CFS and TFS, and two regions for BFS.
• Fractographic analysis of HI specimens indicated a transition in failure modes.

Conclusions:

• Compressive fracture strength (CFS) testing emerged as the sole discriminatory performance indicator among the tested methods.
• Compressive modulus (CM) and tensile flexural modulus (TFM) reflect intrinsic material properties and can supplement CFS testing.
• The findings provide a basis for a standardized mechanical testing methodology for hand-mixed GIs.