Project Details
Projekt
Addressing initial composite debonding in root canals: interactions between shrinkage, ageing and residual strains
Subject Area
Biomaterials
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 396127899
Resin dental composites are frequently used for direct fillings of cavities in vital human teeth as for building up and restoring root canal treated teeth. Our findings from the first funding period suggest that both, the interzone between adhesive filling and root dentine as well as the interzone between the flexible root filling material gutta-percha and restorative material are affected by the in situ polymerization dynamics of the composite and the resulting residual strains and stresses. The situation becomes even more complex over time, due to exposure to the humid environment, which may lead, for example, to composite swelling due to water uptake and degradation. In this extension project, we seek a deeper understanding of the complex interplay of polymerization shrinkage, debonding and residual strains for adhesive composite fillings in the upper part of root canals over time. Building on knowledge gained in the first funding period we will expand our bovine root canal model to cavity geometries with increasing complexity. We will analyse the spatial and temporal development of immediately released versus residual strains in composite fillings using high-resolution phase-contrast enhanced (PCE) radiographs and tomographs from min to months after filling placement to further understand and quantify the effects of storage up to and beyond a year. The image processing of the PCE-μCT data will involve AI-based segmentation approaches to quantitatively analyse the segmented gaps in 2D along the cavity depth, yielding the "gap percentage", and in 3D for determination of gap shapes and sizes in dependence of the cavity height. In addition, we will evaluate the effects of mechanical loading on the structural integrity of the interzone. By creating finite-element (FE) models we will gain knowledge on the stress-raising effect of gaps and delaminations in our root canal models, ultimately contributing to the question how dangerous the gaps at the deeper parts of the cavity are for a tight seal. We will apply the established hole drilling method from the first funding period to residual strain measurements in more complex geometries and aim to understand what strains are generated by and stored in the composite during shrinkage, and what is their influence on the local mechanical properties. The interzone between the flexible root-filling material gutta-percha and restorative materials will be specifically addressed by employing high-resolution PCE-µCT imaging before, during and after various loading conditions, and FE models will be developed to simulate changes in the stress state. The results will provide recommendations for the design of improved dental restoration materials, and, thus for treatment strategies for root-canal-treated teeth.
DFG Programme
Research Units
Subproject of
FOR 2804:
The Materials Science of Teeth in Function: Principles of Durable, Dynamic Dental Interphases
International Connection
Netherlands
Cooperation Partner
Professor Hagay Shemesh, Ph.D.
