Comparison of urethane dimethacrylate monomer elution between indirect composites when subjecting to thermocycling

Context: The use of resin-based computer-aided design and computer-aided manufacturing (CAD/CAM) blocks is increasing in restorative dentistry. However, the potential elution of urethane dimethacrylate (UDMA) into saliva and its associated safety implications remain insufficiently investigated. Aims: To identify and quantify the monomer elution of two different indirect composite blocks before and after thermocycling. Settings and Design: In vitro study. Subjects and Methods: Two composite CAD-CAM blocks were investigated: a resin-based composite block (RCB, Shofu HC Block) and a polymer-infiltrated ceramic network block (PICN, Vita Enamic). Twenty specimens from each material ( n = 20) were prepared. All specimens ( n = 40) were immersed in artificial saliva at 37°C for 24 h before thermocycling. Extractions were performed after 24 h of immersion and subsequently after 500 and 10,000 cycles of thermocycling. UDMA monomer elution was analyzed using high performance liquid chromatography (HPLC). Statistical Analysis Used: Kruskal–Wallis test. Results: No quantifiable level of UDMA was observed in either RCB or PICN before thermocycling. After 500 cycles of thermocycling, UDMA elution was identified in RCB (0.04 mg/mL), but remained undetectable in PICN. Following 10,000 cycles of thermocycling, both RCB and PICN showed UDMA release of 0.01 mg/mL. However, the Kruskal–Wallis test revealed no statistically significant differences among groups ( P > 0.05). Conclusions: The highest UDMA elution occurred in RCB after 500 cycles of thermocycling. Despite differences in polymer structure, thermocycling did not significantly influence UDMA release in either material.