Evaluation of the Adequate Radiopacity of Cavity Lining/Base and Core Build‐Up Light Cured Composite Resins

BACKGROUND: This study aimed to compare the radiopacity of composite resins (CR) used as lining, base, and core-build up materials with enamel and dentine and evaluate their compliance with ISO 4049. METHODS: Specimens of 1, 2, and 3 mm thicknesses; (n = 6) were fabricated from 13 low-viscosity and 10 regular-viscosity CRs. Slices of enamel and dentine from human molar crowns (1, 2, and 3 mm, n = 3) were used as references. Five radiographic exposures of all samples were taken and analysed through Welch One-way ANOVA with Games-Howell/Dunnett's or Kruskal-Wallis with Dwass-Steel-Critchlow-Fligner tests regarding viscosity, insertion technique, particle size, filler size and composition. RESULTS: At 1 mm thickness, the mean radiopacity of all materials was above 1 mm aluminium. At all thicknesses, bulk-fill application technique exhibited significantly higher radiopacity than incremental (p < 0.001). Regular viscosity composite resins were significantly more radiopaque than low viscosity at 2 mm (p = 0.013) and 3 mm (p = 0.005) thicknesses. All tested composite resins complied with ISO 4049 radiopacity requirements. However, for liner and core build-up applications, radiopacity higher than dentine may be clinically advantageous for reliable radiographic detection. Thus, material selection should consider the intended clinical use, as current ISO criteria may not fully address all restorative purposes.