Permeability of amalgam restorative materials

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Caries Prevention Research

Background:

• Fluoride-containing dental amalgam's efficacy in preventing recurrent dental caries is directly linked to its fluoride ion (F) delivery capability.
• Understanding fluoride diffusion dynamics within amalgam is essential for optimizing its cariostatic properties.
• Amalgam degradation and changes in ion diffusion over time can impact its long-term clinical performance.

Purpose of the Study:

• To quantify and compare the diffusion coefficients of fluoride (F) in freshly prepared and aged dental amalgam specimens.
• To assess the impact of storage in fluoride solution on the diffusion characteristics of F in amalgam.
• To investigate the diffusion kinetics of F and use 125I as a reference tracer in amalgam.

Main Methods:

• A two-chamber diffusion cell was utilized to monitor F diffusion through amalgam membranes.
• Measurements were conducted on both fresh amalgam and amalgam stored in fluoride solution for 15 days.
• Diffusion coefficients (D) for F and 125I were determined through successive measurements over extended periods.

Main Results:

• The average diffusion coefficient (D) for F in fresh amalgam was 2.39 x 10⁻¹⁰ cm²/s, compared to 1.85 x 10⁻¹⁰ cm²/s for 125I.
• For stored amalgam, the average D of F over 30 days was 1.35 x 10⁻¹⁰ cm²/s, representing a 31% reduction compared to fresh amalgam (p < 0.01).
• Scanning Electron Microscopy (SEM) revealed corrosion product deposition on amalgam stored in fluoride solution for 3 months.

Conclusions:

• Fluoride diffusion from dental amalgam decreases significantly after storage, particularly in fluoride-containing environments.
• The observed decline in diffusion suggests potential changes in amalgam material properties over time.
• These findings highlight the importance of considering amalgam aging and storage conditions for sustained fluoride release and caries prevention.