Long-Term Water Balance Evaluation in Glass Ionomer Restorative Materials

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials

Background:

• Understanding water balance in glass ionomer cements (GICs) is crucial for dental restorations.
• Existing knowledge relies on early studies and short-term data.
• Long-term water dynamics in conventional and resin-modified GICs require further investigation.

Purpose of the Study:

• To evaluate the long-term (3 years) water species in conventional and resin-modified GICs.
• To analyze changes in bound and unbound water content and their removal enthalpy over time.
• To provide insights into the stability and water management of GIC materials.

Main Methods:

• Thermogravimetric analysis (TGA) was used to assess water content and binding.
• Six conventional and four resin-modified GICs were tested.
• Samples were stored in phosphate-buffered saline and analyzed at multiple time points up to 36 months.

Main Results:

• All GICs showed a significant increase in unbound water percentage over 36 months.
• Bound water content and its removal enthalpy stabilized within 24 hours for all materials.
• The enthalpy for removing unbound water remained constant in conventional GICs but varied in resin-modified ones.

Conclusions:

• Unbound water content in GICs increases over time and is loosely held, especially in conventional types.
• Resin-modified GICs exhibit distinct water behavior compared to conventional ones.
• Protective coatings are recommended for conventional GICs to prevent unbound water loss and maintain material integrity.