Temperature transmission of high-output light-curing units through dentin

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• Light-curing units (LCUs) are essential for polymerizing dental restorative resins.
• LCUs generate heat during operation, with potential implications for pulp tissue.
• Novel LCUs with enhanced light delivery may reduce curing times but their thermal effects are not fully understood.

Purpose of the Study:

• To investigate the temperature rise transmitted through resin composite and dentin when using high-output light-curing units.
• To compare the thermal effects of a standard light guide, a concentrating light guide, and a plasma arc lamp.
• To assess the influence of dentin thickness on heat transfer from LCUs.

Main Methods:

• Temperature rise was measured for 40 seconds using an Optilux 401 Curing Light with standard and Turbo light guides, and for 3 seconds with an Apollo 95E Plasma Arc Curing Light.
• Temperatures were recorded directly at the light guide tip and through a 1 mm resin composite and dentin sandwich (0.58 mm or 1.45 mm dentin thickness).

Main Results:

• Maximum temperature rise occurred directly at the curing tip (up to 26.4°C with Turbo guide).
• The plasma arc unit produced the lowest temperature increase through the composite/dentin sandwich (1.8°C–5.1°C).
• The Turbo light guide significantly increased temperature by 42%–56% compared to the standard guide, with significant differences noted across curing units and dentin thicknesses.

Conclusions:

• High-output LCUs, particularly those with concentrating tips, can cause substantial temperature increases.
• Dentin thickness significantly influences heat transfer, with thicker dentin reducing temperature rise.
• Careful selection of LCU technology and consideration of dentin thickness are crucial to minimize potential pulpal damage during resin polymerization.