The effect of "soft-start polymerization" on surface hardness of two packable composites

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Soft-start polymerization involves initial low-intensity light exposure followed by full-intensity curing.
• This technique is hypothesized to improve marginal integrity in light-cured composite fillings.
• The impact on material properties like hardness requires further investigation.

Purpose of the Study:

• To evaluate the effect of soft-start polymerization protocols on the Vickers hardness of packable dental composites.
• To compare the Vickers hardness of ALERT and Definite composite brands under different curing conditions.
• To assess if soft-start polymerization influences the degree of conversion and surface hardness.

Main Methods:

• Vickers hardness testing was performed on ALERT and Definite packable composites.
• Samples were subjected to different light-curing modes, including soft-start polymerization and conventional methods.
• Curing was done using various light guide tips to assess their influence.

Main Results:

• ALERT composite exhibited significantly higher Vickers hardness than Definite composite (p<0.05).
• No significant difference in Vickers hardness was observed between soft-start polymerization and conventional curing methods.
• The type of curing mode and light guide used did not significantly affect the Vickers hardness of the tested composites.

Conclusions:

• Soft-start polymerization does not significantly enhance the Vickers hardness or degree of conversion of the tested packable composites.
• The brand of the composite material is a more critical factor for Vickers hardness than the curing protocol.
• Different light guide tips showed no significant improvement in the surface hardness of the composites.