# Impact of storage conditions on the fracture reliability and physical properties of a dental resin-based composite

## TL;DR

This study shows how different storage conditions and durations affect the strength and properties of a dental resin composite material.

## Contribution

The study provides new insights into how storage conditions influence the mechanical behavior of a nanofilled resin-based composite.

## Key findings

- Dry storage increased degree of conversion after 72 hours and improved flexural strength and hardness.
- Wet storage initially improved strength but led to a decline after 168 hours.
- Weibull modulus remained unchanged across all storage conditions.

## Abstract

This study investigated the impact of ‘storage condition’ and ‘period of storage’ on selected physico-mechanical properties and fracture reliability of a resin-based composite (RBC). Specimens, prepared from a nanofilled RBC (Filtek Z350 XT; 3M ESPE), underwent tests for degree of conversion (DC), flexural strength (σ), flexural modulus (E), and hardness. The specimens were initially grouped into dry storage at 37°C or wet storage in distilled water at 37°C. Subsequently, they were further divided into four subgroups based on the period of storage: 6, 24, 72, or 168 hours. Specimens tested immediately after preparation served as control. Data analysis employed two-way ANOVA and Weibull analysis (α = 5%). Compared to the control, an increase in DC was observed only after 72 hours of dry storage; σ showed higher values after both dry and wet storage, regardless of the storage period (except for the group wet-stored for 168 hours); E increased with dry storage for at least 24 hours or wet storage for 72 hours; and hardness increased after dry storage for at least 24 hours or wet storage for up to 72 hours. The Weibull modulus remained unchanged under any of the distinct storage conditions. Dry storage resulted in greater characteristic strength than the control, whereas wet storage contributed to higher strength values only at shorter periods (up to 24 hours). Overall, the inherent properties of RBCs with a similar composition to that tested in this study may change with varying storage conditions and periods.