The effect of dentine conditioning agents on solubilisation of bioactive dentine matrix components and dentine regeneration

The dentine-pulp complex is a unique, dynamic organ capable of responding to mild and aggressive injurious stimuli. Deep caries or tooth fractures that extend close to the pulp can lead to inflammation and ultimate pulpal necrosis if not managed appropriately. Current therapeutic regimes for such scenarios include the use of vital pulp (capping) treatments, which attempt to stimulate the pulp’s auto-repair capacity which is still poorly understood and consequently not exploited to its full potential. Amongst the possible mechanisms involved in inducing a dentinogenic response in vital pulp therapy, the ability of dental materials in solubilising cell signalling molecules from dentine has been proposed recently. As such, the role of growth factors belonging to TGF-β superfamily in particular has been highlighted during dentine repair and regeneration (Graham et al. 2006). In recent times clinical practice has moved towards the use of dentine bonding agents and composite restorations even in deep dentinal cavities that extend close to the pulp in the hope of reducing the effects of microleakage, amongst others (Lynch 2008). However, although such treatments appear moderately successful in practice, the justifications for introducing new protocols to improve dental pulp protection and dentine bridge formation are not currently driven by biological knowledge. This in vitro study investigated the effects of dentine conditioning by several clinically used etching agents/ dentine conditioners (components of adhesive restorative systems) on the solubilisation of bioactive dentine matrix components and dentine regeneration (by assessing the impact on DPSC phenotype and behaviour). It was found that growth factors (TGF-β1, BMP2 and VEGF) were exposed and released following dentine treatment by EDTA, phosphoric and citric acid. Polyarcrylic acid on the other hand was ineffective in solubilising dentine matrix proteins. Dentine surface conditioning by EDTA, phosphoric and citric acid resulted in an up regulation in the expression of genes associated with osteoblast/odontoblast-like cell differentiation (OPN and ALP) in DPSCs, however surfaces treated with phosphoric acid appeared significantly less supportive of cell growth following 8 days in culture. These findings provide direction for future research and take crucial steps for informing clinical practice as to the choice of materials and techniques in vital pulp treatments

Effects of storage media on physical properties of selected tooth coloured restorative materials

It is known that storage media can affect the physical properties of some restorative dental materials. The purpose of this laboratory study was to investigate the possible effects of storage media on physical properties of a conventional glass-ionomer, a resin modified glass ionomer and a compomer. Specimens of the restorative materials in the study (FujiII LC, FujiIX and Dyract EXTRA) were prepared. The specimens were stored in either water or artificial saliva with or without exposure to Listerine. The compressive and diametral tensile strength and Vickers hardness of these materials were tested at 24 hours, 1 week, 4 weeks and 12 weeks. Compressive and diametral tensile strength for FujiII LC and Fuji IX had increased at 12 weeks. A decrease was observed for Dyract EXTRA in the same period. No significant differences were observed between the storage media (P>0.01). Vickers hardness values fluctuated during the testing period, with a pattern being consistent for each material. Storage of materials investigated for the period in this study resulted in superior compressive and diametral tensile strength for Fuji II LC and FujiIX. The opposite was true for Dyract EXTRA. Effects of time were found to be more pronounced than the media (P<0.01)