The chemical and optical stability evaluation of injectable restorative materials under wet challenge

To investigate and compare the chemical and optical stability of four restorative composite materials: two injectable resins, one flowable resin and one compomer.

Two injectable nano-filled composite resins: G-aenial Universal (GU) and Beautifil Injectable XSL (BI), a flowable composite resin: Filtek Supreme Flowable (FS) and a compomer: Dyract Flow (DF), in A2 shade were tested and compared. Water sorption and solubility were conducted according to ISO4049:2019 standard; ICP-OES and F-ion selective electrode were used to test the elemental release; Degree of conversion (DC) was obtained by using FTIR; water contact angle was obtained by static sessile drop method, and a spectrophotometer was used for optical properties (ΔE^⁎, ΔL^⁎ and TP). SPSS 28.0 was used for statistical analysis and the significant level was pre-set as α = 0.05.

GU performed the best in water sorption and solubility, FS had the lowest elemental release, the best colour stability, and the highest DC_IM and DC_24-h. DF, the compomer had the lowest, and GU and BI, the injectable composites had the largest water contact angle, respectively. Correlations were found between water sorption and water solubility.

The four composite restorative materials showed different chemical and optical behaviours. Overall, composite resins performed better than compomer, while additional laboratory and in vivo tests are necessary to obtain a more comprehensive comparison between injectable and flowable composite resins. W_sp and W_sl are influenced by many common factors, and the values are highly positively related.

A comprehensive understanding of materials is crucial before selecting materials for clinical practice. Composite resins rather than compomers are recommended because of their exceptional properties, which make them eligible for a wide range of clinical applications and an elongated lifespan.