Properties of a Novel Brominated Radiopaque Dental Resin with Ethyl 4-(dimethylamino) Benzoate as a Photoinitiator

Abstract

Background: Resin infiltration effectively arrests early carious lesions but lacks radiopacity, complicating radiographic assessment. This study investigated a novel brominated dental resin using ethyl 4-(dimethylamino) benzoate (EDAB) as photoinitiator. Aim: To evaluate the characteristics of a new brominated infiltrant (BrM-BI) with EDAB, examining degree of conversion (DC%), radiopacity, water absorption and solubility compared to non-brominated basic infiltrant (BI). Method: Basic infiltrant (20% UDMA, 80% TEGDMA) was prepared with 1% photoinitiator (0.5% camphorquinone, 0.5% EDAB). For BrM-BI, 2,3-dibromobutane-1,4-diyl bis(2-methylacrylate) was incorporated (1:1 ratio). DC% was assessed using FTIR spectroscopy. Radiopacity was compared to aluminium step-wedge. Water absorption and solubility were evaluated through extended testing (66 days). Results: BrM-BI showed significantly lower DC% (62.99±3.22%) than BI (74.37±1.84%). Average radiopacity of BrM-BI was 1.79±0.18mm Al, exceeding dentine (1mm Al). Water absorption behaviour differed markedly between materials; BI reached equilibrium at 5.21±0.15% (24 days), while BrM-BI peaked at 4.5% (38 days) before declining to 0.86±0.17% (66 days). BrM-BI exhibited significantly higher solubility (6.02±0.09%) than BI (0.12±0.08%). Conclusion: The brominated resin successfully achieved radiopacity with potential for clinical visibility. However, reduced polymerisation efficiency and high solubility indicate further formulation optimization is necessary before clinical application.