Abstract
Computer-aided design and computer-aided manufacturing (CAD/CAM) denture base manufacturers claim to produce their resin pucks under high heat and pressure. Therefore, CAD/CAM dentures are assumed to have enhanced mechanical properties and, as a result, are often produced with lower denture base thicknesses than conventional, manually fabricated dentures. The aim of this study was to investigate if commercially available CAD/CAM denture base resins have more favourable mechanical properties than conventionally processed denture base resins. For this purpose, a series of three-point bending tests conforming to ISO specifications were performed on a total of 80 standardised, rectangular CAD/CAM denture base resin specimens from five different manufacturers (AvaDent, Baltic Denture System, Vita VIONIC, Whole You Nexteeth, and Wieland Digital Dentures). A heat-polymerising resin and an autopolymerising resin served as the control groups. The breaking load, fracture toughness, and the elastic modulus were assessed. Additionally, the fracture surface roughness and texture were investigated. Only one CAD/CAM resin showed a significantly increased breaking load. Two CAD/CAM resins had a significantly higher fracture toughness than the control groups, and all CAD/CAM resins had higher elastic moduli than the controls. Our results indicate that CAD/CAM denture base resins do not generally have better mechanical properties than manually processed resins. Therefore, the lower minimum denture base thicknesses should be regarded with some caution.
Highlights
Cracks and fractures are the most common causes of failure among removable complete dentures [1]
ISO compliance, but to compare the mechanical performances of Computer-aided design and computer-aided manufacturing (CAD/CAM) denture base resins conventionally processed resins, since previous mechanical with conventionally processed resins, since previousstudies studiesinvestigating investigating the the mechanical properties of denture base resins had criticised the rationale of the cut-off values given in the the ISO
The results of the present study demonstrate that there are large variations in fracture resistance between the different available CAD/CAM denture base resins
Summary
Cracks and fractures are the most common causes of failure among removable complete dentures [1]. University of Innsbruck reports around 175 incidents of denture cracks and fractures per year. Besides poor denture design [2], denture failure is attributed to the denture base resins’ poor mechanical properties [3]. For enhancing these properties, different targets have been pursued, such as altering the microstructure by admixing additives [4,5,6], increasing the liquid/powder ratio [7], and optimising the processing protocol [8,9]. A comparative study from 2012 concluded that the introduction of completely new manufacturing techniques might be necessary [4].
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