Linear dimensional change during setting of a zinc phosphate cement. A methodological study

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Physical Chemistry

Context:

• Understanding the setting process of dental materials is crucial for clinical success.
• Linear dimensional changes, specifically contraction, can impact the marginal integrity of dental restorations.
• Zinc phosphate cement is a widely used dental material.

Purpose:

• To investigate and quantify the linear dimensional changes (contraction) of zinc phosphate dental cement during its setting process.
• To evaluate the influence of powder-to-liquid ratio and environmental humidity on cement contraction.
• To establish a reliable method for measuring these dimensional changes.

Summary:

• A method was developed to measure linear dimensional changes of zinc phosphate cement during setting at 37°C.
• Specimens were tested under varying humidity levels, with measurements commencing 3 minutes after mixing.
• Both high (3:1) and low (2:1) powder-liquid ratio cements exhibited contraction under wet and dry conditions.
• Under wet conditions, contraction was consistent (0.43% at 30 min, 0.66% at 1 day).
• Under dry conditions, contraction was more significant and varied with powder-liquid ratio (High ratio: 1.33% at 30 min, 3.83% at 7 days; Low ratio: 0.79% at 30 min, 4.76% at 7 days).

Impact:

• Quantifies setting contraction in zinc phosphate cement, providing critical data for material selection and application.
• Highlights the significant impact of environmental humidity and powder-liquid ratio on cement dimensional stability.
• Informs the development of dental cements with improved dimensional accuracy and reduced risk of marginal gap formation.