Minimally Invasive Dentistry via Dual-Function Novel Bioactive Low-Shrinkage-Stress Flowable Nanocomposite.

Abstract

The application of biomaterials science is unique in dentistry because of the complexity of the oral cavity. The oral environment is considered the most challenging for material in the body in which high mechanical loading, bacteria, changing pH, and a warm, fluid environment. Understanding the physical, chemical, biological, and biocompatibility of restorative material is very important when choosing materials for specific dental applications and designing the best solution to replace tissue lost to disease or trauma. Resin-based composite has been introduced into conservative dentistry to minimize acrylic resins' drawbacks and silicate cements and amalgam restorations. It is the material of choice in dailydental practice for several reasons, including their good mechanical properties, conservative cavity design, and superior esthetics. However, the longevity of current resin composite restorations ranges only 5-10 years. Gap formation, recurrent caries and tooth fracture are the most common types of failure of clinical service. These failures are often caused directly or indirectly by the polymerization shrinkage stress of the dental composite materials. Thus, there is an increased need to develop a new generation of bioactive dental composite with the ability to reduce polymerization shrinkage stress, long-term antibacterial, remineralization abilities, and excellent mechanical properties. Therefore, this dissertation aims to develop a new bioactive low-shrinkage- stress dental composite containing dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) and nanoparticles of calcium fluoride (nCaF2) which could be a promising approach to increase the chances of success of composite restorations and strengthen tooth structures. First, we formulated optimum percentage of bioactive low-shrinkage-stress resin composite with proper concentration of long lasting copolymerized antibacterial DMAHDM, and adequate percentage of remineralization nanoparticles. Second, we performed several investigations to test the novel formulations. The physical, mechanical, and biological experiments were studied. We found that the new bioactive low-shrinkage-stress resin composite significantly reduced the bacterial counts and metabolic activites, without compromising their mechanical properties in comparing to the commercial control and experimental control composites. The novel formulation of “45% UV+5% DMAHDM+20% NACP+30% glass” and “47% UV+3% DMAHDM+20% nCaF2+30% glass” potent triple benefits of antibacterial, remineralization, and lower shrinkage stress. They have a great potential to inhibit recurrent caries and increase restoration longevity.