Water distribution in dentin matrices: bound vs. unbound water

Area of Science:

• Biomaterials Science
• Dental Materials Science
• Materials Science

Background:

• Dentin's water content significantly influences its mechanical properties and interaction with restorative materials.
• Understanding the different states of water (bound vs. unbound) in demineralized dentin is crucial for optimizing adhesion and infiltration of dental resins.

Purpose of the Study:

• To quantify the amount of bound and unbound water in completely demineralized dentin.
• To evaluate the effectiveness of different dehydration methods (evaporation and chemical) on removing bound and unbound water.

Main Methods:

• Human dentin beams were completely demineralized and rehydrated to different relative humidity levels (41%, 60%, 99%).
• Gravimetric analysis was used to measure water uptake and determine water plateaus.
• Bound and unbound water content were assessed after exposure to varying relative humidity and chemical dehydration agents (ethanol, acetone).

Main Results:

• Bound water constitutes 21-25% of the total water content in demineralized dentin.
• Evaporative methods were largely ineffective in removing bound water.
• Chemical dehydration with 100% acetone removed more bound water (especially from the third layer) than 100% ethanol, though it primarily removed unbound water (25-35%).

Conclusions:

• Bound water in demineralized dentin is resistant to evaporative removal.
• Chemical dehydration, particularly with acetone, shows greater potential for removing bound water compared to ethanol.
• Efficient removal of unbound water (75-79% of total) is critical for enhancing resin infiltration and improving the success of dental restorations.