The use of composites as core material in root-filled teeth. I. In vitro study.

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• Dental restorations require durable cement retention between core materials and crowns.
• Thermal stress from temperature variations can compromise the integrity of cement bonds.
• Understanding material performance under simulated oral conditions is crucial for long-term restoration success.

Purpose of the Study:

• To investigate the effect of repeated thermal stress on cement retention between composite cores and gold crowns.
• To compare the retention of different composite materials and cements under cyclic temperature changes.
• To identify factors influencing the bond strength and longevity of dental core-crown interfaces.

Main Methods:

• Extracted permanent teeth were prepared as cores, and gold crowns were fabricated.
• Four test-pieces per core shape were created using gold and three composite materials (microfill, two-paste macrofill, single-paste macrofill).
• 48 test series utilized two new cements and four zinc phosphate cements, subjected to 12-hour thermo-cycling (0°C, 25°C, 50°C) before tensile stress testing.

Main Results:

• Microfill composite cores exhibited the lowest cement retention values.
• No significant differences in retention were observed between gold and macrofill composite cores.
• One specific zinc phosphate cement (normal- and fast-setting) showed approximately double the retention load compared to other tested cements.

Conclusions:

• Microfill composites are less retentive under thermal stress compared to gold and macrofill composites.
• The choice of cement significantly influences the retention strength of dental restorations.
• A specific zinc phosphate cement offers superior retentive capabilities, potentially enhancing restoration longevity.