Compressive Deflection of Biodentine and Two Glass Ionomer Bases

Objective: To determine the mechanical-support-equivalency of three materials used as bases below a composite. Base materials must develop adequate stiffness to support the restoration during masticatory loading. The stiffness of a new calcium silicate dentin substitute (B, Biodentine, Septodont) and two commercially successful glass ionomers (F, Fuji IX, GC America; V, Vitremer, 3M ESPE) was compared at 4 curing times when loaded in compression in a confined space similar to a Class I cavity. Methods: A stainless-steel test fixture composed of a base block and a matching square plate 1.85 mm-thick with a cylindrical hole 4.04 mm Φ drilled through it was assembled to produce a cylindrical cavity with one closed end. The materials were placed in this cavity and allowed to cure for the different time periods before applying a compressive load. Loading was performed using a flat-ended piston that closely fit the cavity and was driven into the cavity using a universal test machine (Instron 5866). Loading time points of 1/2, 1, 2, or 24 hours after initiation-of-mixing of the materials were used. The specimen was loaded to 1334 N with deflection measured at 500 and 1334 N. Results:

Base Material Deflection  @ ½ H Curing			Deflection @ 1 H Curing
Material	d@500 N, mm	d@1334 N, mm	d@500 N, mm	d@1334 N, mm
B	0.09(0.05)	0.17(0.06)	0.03(0.01)	0.07(0.01)
V	0.06(0.02)	0.10(0.02)	0.06(0.01)	0.12(0.02)
F	0.05(0.01)	0.09(0.02)	0.04(0.01)	0.07(0.02)

Conclusions: Biodentine at ½ H after initial mixing at 500 N load deflected 50% and 80% more under load than for Vitremer and Fuji IX, respectively. By 1 H of curing, Biodentine deflected 50% less than Vitremer and 25% less than Fuji IX. Between ½ H and 1 H, Biodentine was equivalent or slightly better at supporting load than Fuji IX or Vitremer. Funded in part by Septodont.