Influence of artificial aging: mechanical and physicochemical properties of dental composites under static and dynamic compression

Abstract

Objective: The aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging.

Materials and methods: Specimens (1 mm³) of three commercially available composites (GrandioSO®, Arabesk Top®, Arabesk Flow®) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F = ± 7 N; f = 0.5 Hz, 1 Hz and 3.3 Hz; t = 0-170 °C).

Results: Incorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation.

Conclusion: Although the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard. Clinical relevance Preferential use of highly filled composites for occlusal fillings is recommended.

Keywords: Artificial aging; Dental composites; Mechanical and physicochemical properties; Static and dynamic compression tests.

Fig. 1

Ultrathin Sect. (90 nm); transmission electron microscopy (TEM) of tested composites

Fig. 2

Exemplary SEM-image of specimen (composite A/specimen number 585)

Fig. 3

Test procedure

Fig. 4

Penetration impression after measurement

Fig.5

Exemplary representation of frequency-dependent temperature profile of storage modulus E´ (MPa) and damping factor tan δ for the composites A, B and C in the initial state

Fig.6

Frequency dependency of storage modulus: E´ (GPa) of the composites A, B and C after 180 days (in order to determine the influence of time, data of different media were summarized)