Porosity in manually and machine mixed resin-modified glass ionomer cements

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Polymer Chemistry

Background:

• Resin-modified glass ionomer cements (RMGIC) are widely used in dentistry.
• The physical properties of RMGICs can be influenced by their mixing method.
• Understanding the impact of mixing techniques is essential for optimizing cement performance.

Purpose of the Study:

• To quantify the effect of manual versus machine mixing on the porosity of a specific RMGIC (Fuji II LC).
• To evaluate the influence of mixing method on the shear strength of the RMGIC.
• To compare the microstructural and mechanical properties resulting from different mixing procedures.

Main Methods:

• Resin-modified glass ionomer cement (Fuji II LC) was mixed using both manual and machine methods.
• Porosity was assessed using digital imaging of thin specimens (approx. 76 microns).
• Shear strength was determined via shear punch tests on thicker specimens (approx. 800 microns) using a universal testing machine.

Main Results:

• Manually mixed RMGIC exhibited a significantly higher mean number and total volume of pores compared to machine-mixed RMGIC (p < 0.05).
• Machine-mixed RMGIC demonstrated significantly higher shear punch test results than manually mixed RMGIC (p < 0.05).
• Mixing method demonstrably impacts both the porosity and mechanical integrity of the cement.

Conclusions:

• Machine mixing is superior to manual mixing for reducing porosity in Fuji II LC.
• Mechanical mixing enhances the shear strength of this resin-modified glass ionomer cement.
• Optimized mixing protocols are critical for achieving desired properties in dental cements.