Influence of curing modes on crosslink density in polymer structures.

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Dental composites are widely used restorative materials.
• The degree of crosslinking in dental composites influences their physical properties and durability.
• Light-curing modes can affect the polymerization process and final material characteristics.

Purpose of the Study:

• To investigate how different light-curing modes affect the crosslinking density of dental composites.
• To evaluate the impact of curing modes on the susceptibility of dental composites to ethanol degradation.

Main Methods:

• Four light-curing modes (control, pulse delay, soft-start, pulse cure) were applied to dental composite specimens (Z100, 3M-ESPE) with constant light energy density.
• Degree of crosslinking was assessed directly using differential scanning calorimetry (DSC) to measure glass transition temperature.
• Indirect assessment of crosslinking involved measuring hardness before and after ethanol exposure (hardness deterioration).

Main Results:

• Direct assessment via DSC indicated the following ranking for crosslinking density: Control > Pulse Cure > Soft-Start > Pulse Delay.
• Indirect assessment using hardness deterioration showed the ranking: Pulse Cure > Soft-Start > Control > Pulse Delay.
• Specimens cured with Pulse Delay exhibited significantly greater softening in ethanol.

Conclusions:

• Pulse Delay polymerization resulted in a lower crosslink density in dental composites.
• Dental composites polymerized with Pulse Delay demonstrated increased susceptibility to softening when exposed to ethanol.
• The choice of light-curing mode significantly influences the crosslinking density and degradation resistance of dental composites.