Influence of chemomechanical caries removal methods on dentine

Abstract

Chemomechanical caries excavation is an excellent example of conservative caries removal methods due to its ability to reliably preserve a greater thickness of caries-affected dentine (CAD). Chemomechanical caries removal (CMCR) agents dissolve the denatured collagen fibrils leaving the sound and partially degraded fibrils intact. Also, one of the main advantages of the CMCR method is its characteristic visual excavation end point sign, after this point, the solution fails to become turbid. Chemomechanical caries removal agents are classified based on their chemistry into sodium hypochlorite (NaOCl)- or enzyme-based CMCR agents.

The aim of this project was to evaluate the efficacy of currently available chemomechanical caries removal methods and their effects on tooth substrate, residual bacteria, and bonding to dentine with either resin- or resin-modified glass ionomer (RM-GIC)-based adhesives. The current project was designed to answer five research questions. The first research question aimed to compare the caries excavation time between CMCR and rotary caries removal methods. According to the outcome of this study, the NaOCl-based CMCR method is more time consuming compared with the enzyme-based CMCR method. Furthermore, no significant difference in caries excavation time was found between the enzymebased CMCR and the caries-detector guided rotary caries excavation method.

The second research question investigated the effects of CMCR methods on surface topography, hardness and chemical structure of dentine. The morphological analysis showed that there was no smear layer formed following enzyme-based CMCR; while it was partially absent after the NaOCl-based CMCR method. Also, the Vickers hardness of residual dentine following both CMCR methods was lower than the hardness of dentine following the rotary caries removal method. Moreover, the outcome of this study also revealed that the CMCR methods investigated had no adverse effect on the chemical structure of dentine.

The third research question was regarding the evaluation of the antibacterial effects of CMCR agents. Accordingly, a study was conducted on coronal cariesfree dentine discs using a modified non-invasive protocol. This confocal laser scanning microscopy study reported that the enzyme-based CMCR agent (Papacarie) showed an antimicrobial effect similar to 2% chlorhexidine gluconate solution (gold standard antibacterial solution). The NaOCl-based CMCR agent (Carisolv) showed a weak antibacterial activity, which could be improved by subsequent application of a silver diamine fluoride and potassium iodide agent.

The ‘adhesion studies section’ of this project consists of three studies and was conducted to answer the fourth and fifth research questions of this project. The outcomes of the first and second studies showed that surface treatment of dentine with 37% phosphoric acid for 5 seconds had no adverse effect on bonding of RMGIC adhesives to both sound and caries-affected dentine, which addressed the fourth research question.

The purpose of the last research question was to evaluate the effect of CMCR method on bonding of MDP-containing self-etch and RM-GIC adhesives to residual caries-affected dentine. It was concluded that CMCR methods had no adverse effects on bonding to dentine and both adhesive systems showed good bond strengths to caries-affected dentine.