A Review of Mechano-Biochemical Models for Testing Composite Restorations

Abstract

Due to the severe mechano-biochemical conditions in the oral cavity, many dental restorations will degrade and eventually fail. For teeth restored with resin composite, the major modes of failure are secondary caries and fracture of the tooth or restoration. While clinical studies can answer some of the more practical questions, such as the rate of failure, fundamental understanding on the failure mechanism can be obtained from laboratory studies using simplified models more effectively. Reviewed in this article are the 4 main types of models used to study the degradation of resin–composite restorations, namely, animal, human in vivo or in situ, in vitro biofilm, and in vitro chemical models. The characteristics, advantages, and disadvantages of these models are discussed and compared. The tooth–restoration interface is widely considered the weakest link in a resin composite restoration. To account for the different types of degradation that can occur (i.e., demineralization, resin hydrolysis, and collagen degradation), enzymes such as esterase and collagenase found in the oral environment are used, in addition to acids, to form biochemical models to test resin–composite restorations in conjunction with mechanical loading. Furthermore, laboratory tests are usually performed in an accelerated manner to save time. It is argued that, for an accelerated multicomponent model to be representative and predictive in terms of both the mode and the speed of degradation, the individual components must be synchronized in their rates of action and be calibrated with clinical data. The process of calibrating the in vitro models against clinical data is briefly described. To achieve representative and predictive in vitro models, more comparative studies of in vivo and in vitro models are required to calibrate the laboratory studies.

A critical analysis of research methods and experimental models to study the load capacity and clinical behaviour of the root filled teeth

“…Moreover, the environmental effects during testing of tooth and restorations have hardly been measured in previous laboratory studies. There are many other factors besides mechanical loading that affect the behaviour of restored teeth, like chemical and biological interactions among materials, fluids and microbial cells (Zhang et al, 2020(Zhang et al, , 2021.…”

“…To develop a gold standard to test different restorative modalities an accelerated multicomponent model needs to predict accurately the mode and the speed of the restoration failure. This can only be accomplished if the individual components are synchronized and calibrated with clinical data (Zhang et al, 2021). The future development of new laboratory models will bring not only precise but also highly accurate results (Figure 4).…”

“…This is relevant for direct restorations because debonding of the dentine–composite interface happens prior to longitudinal cracking or cuspal flexure in root‐filled teeth under mechanical loading (Lin et al, 2022b). While these relevant variables that contribute to the degradation of the restorative material interface or the substratum have been evaluated separately, they need to be considered concomitantly to account for synergistic effects in future studies (Orrego et al, 2017; Zhang et al, 2021). To develop a gold standard to test different restorative modalities an accelerated multicomponent model needs to predict accurately the mode and the speed of the restoration failure.…”

“…The temperature fluctuations, aeration and humidity control must mimic the conditions found in the natural environment. One additional requirement to improve accuracy is that the artificial oral conditions should stress the tested material in a mechano-biochemical environment also known as multicomponent model (Carrera et al, 2017;Zhang et al, 2020Zhang et al, , 2021. In the clinical scenario, dental materials and their respective bonding interfaces can worsen through polymerization shrinkage of resin composites, pH variation, biofilm colonization, wear and hydrolysis (Zhang et al, 2020(Zhang et al, , 2021.…”

Interface between Materials and Oral Biology

“…This special issue of the Journal of Dental Research contains 4 state-of-the-art critical reviews tackling regenerative engineering (Hosseini et al, 2021), oral biomineralization (Moradian-Oldak and George, 2021), advanced testing modalities for dental restorations (Zhang et al, 2021), and the important factors involved in commercializing new innovations in regenerative materials (Taylor et al, 2021). The complex interactions occurring between biomaterials and fluids, as well as living cells and tissues in the oral environment, are highlighted in a series of 17 original research reports.…”