[Studies on visible-light initiator system using thiobarbituric acid derivatives]

Area of Science:

• Polymer Chemistry
• Dental Materials Science

Background:

• Visible-light curing resins are crucial in dentistry.
• Initiator systems determine resin polymerization efficiency.
• Thiobarbituric acid derivatives are explored as novel reducing agents.

Purpose of the Study:

• To evaluate novel thiobarbituric acid derivatives as reducing agents in visible-light curing systems.
• To compare their efficacy against established reducing agents like N,N-dimethylaminoethyl methacrylate (DMAEMA).
• To determine the optimal thiobarbituric acid derivative for resin polymerization.

Main Methods:

• Preparation of experimental visible-light curing resins incorporating dl-camphorquinone and various thiobarbituric acid derivatives (5-methyl-2-thiobarbituric acid, 5-n-butyl-2-thiobarbituric acid, 1,3,5-trimethyl-2-thiobarbituric acid).
• Investigation of initiator system polymerization ability.
• Comparative analysis with systems containing 5-n-butyl-barbituric acid or DMAEMA.
• Evaluation of curing time, maximum exothermic rate, and depth of cure.

Main Results:

• 1,3,5-trimethyl-2-thiobarbituric acid (135 MS) showed minimal insufficient polymerization at low concentrations.
• 135 MS outperformed DMAEMA in curing time, maximum exothermic rate, and depth of cure at 1.0 mole%.
• The order of increasing reducing agent activity was 5-n-butyl-2-thiobarbituric acid < 5-methyl-2-thiobarbituric acid < DMAEMA ≤ 135 MS.
• Sulfur-containing 5-n-butyl-2-thiobarbituric acid was more effective than its non-sulfur analog, 5-n-butyl-barbituric acid.

Conclusions:

• 1,3,5-trimethyl-2-thiobarbituric acid (135 MS) is a highly effective reducing agent for visible-light curing resins.
• 135 MS shows comparable or superior performance to DMAEMA, a widely used reducing agent.
• Thiobarbituric acid derivatives, particularly sulfur-containing ones, represent a promising class of initiators for dental resin composites.