Novel light-curable materials containing experimental bioactive micro-fillers remineralise mineral-depleted bonded-dentine interfaces

Abstract

This study aimed at evaluating the therapeutic remineralising effects of innovative light-curable materials (LCMs) containing two experimental calcium silicate-based micro-fillers (TCS) modified with β-TCP only or β-TCP, zinc oxide (ZnO)/polyacrylic acid (PAA) on mineral-depleted bonded-dentine interfaces in simulated body fluids (SBFS). Three experimental LCMs were formulated: (1) resin A, containing a β-TCP-modified TCS (βTCS) micro-filler; (2) resin B, containing a polycarboxylated β-TCP/ZnO-modified TCS (βZn-TCS) micro-filler; and 3) resin C, containing no filler (control). Acid-etched (35% H₃PO₄) dentine specimens were bonded using the three LCMs and submitted to atomic force microscope (AFM)/nano-indentation analysis to evaluate the modulus of elasticity (Ei) and hardness (Hi) across the interface after SBFS storage (24 h/1 m/3 m). The ultramorphology and micropermeability of the resin–dentine interface were evaluated using confocal laser microscopy. Resin–dentine sticks were created and submitted to microtensile bond strength (μTBS) test (SBFS: 24 h/3 m). Scanning electron microscopy (SEM) was performed after de-bonding. The LCMs containing the experimental bioactive micro-fillers reduced the micropermeability and induced a significant increase of the Ei and Hi along the bonding interface. The specimens created using the resin B (βZn-TCS) attained the highest μTBS values both after 24 h and 3 m of SBFS storage. In conclusion, the innovative bioactive light-curable materials tested in this study are able to induce a therapeutic remineralising effect on the nano-mechanical properties and on the sealing ability of mineral-depleted resin–dentine interfaces. The contemporary idea of minimally invasive operative treatment, where therapeutic restorations are performed to combat the carious process and remineralise the dental hard tissues, may be satisfied by using such resin-base systems, containing βTCS or βZn-TCS bioactive micro-fillers.

Keywords:

• calcium silicate-based fillers
• remineralisation
• resin–dentine interfaces
• nano-mechanical properties
• micropermeability
• polyacrylic acid
• zinc oxide

Acknowledgements

This work was supported by grants CICYT/FEDER MAT2008-02347, CICYT/FEDER MAT2011-24551, JA-P07-CTS2568 and JA-P08-CTS-3944. This article also presents independent research commissioned by the National Institute for Health Research under the Comprehensive Biomedical Research Centre at Guy’s & St. Thomas’ Trust. The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. The authors also acknowledge support from the Centre of Excellence in Medical Engineering funded by the Wellcome Trust. The authors have no financial affiliation or involvement with any commercial organisation with direct financial interest in the materials discussed in this manuscript. Any other potential conflict of interest is disclosed.