Curing behavior of a nanocomposite as a function of polymerization procedure

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Accurate curing of dental nanocomposites is crucial for material longevity and clinical success.
• High-power LED curing units are increasingly used, necessitating an understanding of their impact on polymerization dynamics.
• Shrinkage stress and incomplete cure in deeper layers remain challenges in dental restorative procedures.

Purpose of the Study:

• To analyze the real-time curing behavior of a nanocomposite at varying depths (2 mm and 6 mm).
• To investigate the influence of different curing regimes and light sources on hardness, shrinkage stress, and gelation time.
• To evaluate the efficacy of the soft-start polymerization concept with modern LED curing units.

Main Methods:

• Real-time assessment of the degree of cure at 2 mm and 6 mm depths.
• Investigation of hardness variation with depth, shrinkage stress, and gelation time under 16 distinct curing regimes.
• Utilized one halogen and three LED curing units for comparative analysis.

Main Results:

• The soft-start polymerization concept proved effective, even with high-power LED curing units, reducing shrinkage stress.
• Soft cure polymerization maintained consistent degree of cure and mechanical properties.
• A polymerization duration of 10 seconds was insufficient for adequate curing in deeper layers, leading to a hardness decrease of up to 30%.

Conclusions:

• Soft-start polymerization is a viable strategy to mitigate shrinkage stress in nanocomposites without sacrificing cure depth or mechanical integrity.
• Inadequate curing duration, even with advanced LED units, significantly compromises material properties in deeper regions.
• Optimized curing protocols are essential for achieving uniform and complete polymerization of dental nanocomposites.