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

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

Methods: 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.

Results: 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.

Conclusions: 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.

Clinical significance: 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.