Abstract
Industrially cured, high-translucent computer-aided design/computer-aided manufacturing (CAD/CAM) resin-based composites (RBC) are the most recently launched dental restoratives. Clinical treatments and laboratory tests are based on a homogeneous distribution of properties within CAD/CAM blocks to obtain constant and reproducible results. The study therefore aims to determine the spatial distribution of various micro-mechanical parameters (Vickers hardness, Martens hardness, indentation modulus, creep, elastic and total indentation work) in five representative CAD/CAM RBCs. The properties of the tooth structure were evaluated under similar conditions. Filler size and shape were analyzed by scanning electron microscopy. A multivariate analysis (general linear model) identified a very strong influence of the material on all measured properties (p < 0.001; partial eta squared ηP2 > 0.943), whereby the most sensitive parameters when identifying differences within regions were the indentation modulus and the elastic indentation work. CAD/CAM RBC blocks show gradually varying properties that can increase or decrease from central to peripheral areas regardless of the chemical composition of the materials or the inorganic filler fraction. The degree of variation in the measured properties is material-specific and less than 8.7%. Clinical applications and in vitro study designs should consider slight inhomogeneity in CAD/CAM RBC blocks, while the location of the regions with best mechanical performance depends on the material.
Highlights
Resin-based composites (RBC) are quoted as the most suitable restorative materials to meet the aesthetic and functional requirements of modern times [1]
In light-cured RBC restorations, these properties are directly related to the quality of curing, and in consequence to the amount of radiant exposure that reaches the surface of a restoration [6]
The quality of curing can be affected even more in deeper and peripheral areas of an RBC restoration, considering that the light is attenuated while passing through the material during curing, which induces a gradient of the properties within the restoration [8]
Summary
Resin-based composites (RBC) are quoted as the most suitable restorative materials to meet the aesthetic and functional requirements of modern times [1]. They enable the shade [2,3] and translucency [4] to be perfectly matched to the natural teeth, are suitable for a minimal invasive treatment, and offer good mechanical properties that are comparable to those of the human dentin [5]. In light-cured RBC restorations, these properties are directly related to the quality of curing, and in consequence to the amount of radiant exposure that reaches the surface of a restoration [6].
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