Abstract

Aim. This paper presents a simple, versatile in vitro methodology that enables indirect quantification of shrinkage and expansion stresses under clinically relevant conditions without the need for a dedicated instrument. Methods. For shrinkage effects, resulting cusp deformation of aluminum blocks with MOD type cavity, filled with novel filling compositions and commercial cements, has been measured using a bench-top micrometer and a Linear Variable Differential Transformer (LVDT, a displacement transducer) based instrument. Results. The results demonstrated the validity of the proposed simple methodology. The technique was successfully used in longer-term measurements of shrinkage and expansion stress for several dental compositions. Conclusions. In contrast to in situ techniques where a measuring instrument is dedicated to the sample and its data collection, the proposed simple methodology allows for transfer of the samples to the environment of choice for storage and conditioning. The presented technique can be reliably used to quantify stress development of curing materials under clinically relevant (oral) conditions. This enables direct examination and comparison of structural properties corresponding to the final stage of formed networks. The proposed methodology is directly applicable to the study of self-curing systems as they require mouth-type conditions (temperature and humidity) to achieve their designed kinetics and reactions.

Highlights

  • Shrinkage stress of dental material has attracted the attention of many clinicians and researchers

  • This paper presents a simple, versatile in vitro methodology that enables indirect quantification of shrinkage and expansion stresses under clinically relevant conditions without the need for a dedicated instrument

  • The results demonstrated the validity of the proposed simple methodology

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Summary

Introduction

Shrinkage stress of dental material has attracted the attention of many clinicians and researchers. There has been significant activity in the development of low stress compositions to enable bulk-filling/curing as a faster and easier technique. Several new entries to the market, based on different monomer systems and/or reaction schemes, claim to have created low shrinkage stress. It has been shown that the inclusion of relatively small amount of AdditionFragmentation Monomers (AFM) can significantly reduce the polymerization stress in purely acrylate networks. The inclusion of this class of monomers into the polymerization mixture enables the network to rearrange, that is, adapt during and/or after the polymerization, to accommodate the shrinkage without developing significant stress [3, 4]

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