New antibacterial fillings ' Minimal Invasive (MI) Dentistry
New antibacterial fillings may combat recurring tooth decay
A new studies find potent antibacterial capabilities in novel dental restoratives, or filling materials. According to the researches, the resin-based composites, with the addition of antibacterial nano-assemblies, can hinder bacterial growth and viability on dental restorations, the main cause of recurrent cavities, which can eventually lead to root canal treatment and tooth extractions.
The scientists developed methods for incorporating the nano-assemblies within dental composite restoratives.
so, they evaluated the antibacterial capabilities of composite restoratives incorporated with nanostructures as well as their biocompatibility, mechanical strength and optical properties.
"This work is a good example of the ways in which biophysical nanoscale characteristics affect the development of an enhanced biomedical material on a much larger scale," Schnaider says.
There are two methodologies to resist dental caries. The first method is incorporating inorganic antibacterial NPs into resin composites and agents to reduce microorganism biofilm with direct contact .
the second is to alter oral environment to best reverse carious process .
Composite resins containing 1% silver nanoparticles (AgNPs) or zinc oxide nanoparticles (ZnO NPs) exhibited a better antibacterial activity. Note that the antibacterial effect of composite resin containing ZnO NPs on Streptococcus mutans (S. mutans) was significantly higher than that containing AgNPs . Additionally, S. mutans activity could be significantly inhibited by AgNPs which was formed in situ via a photoreduction mechanism concomitant to the polymerization reaction . Even dental resins containing a low concentration of novel nanofillers possessed adequate and long-term antimicrobial properties . An amount of 1 wt% quaternized copolymer functionalized nanodiamond-reinforced resin composites effectively inhibited the formation of biofilm without cytotoxicity . However, some researches related to the resin luting cements with AgNPs addition and dental sealants modified with nylon-6 and chitosan nanofibers did not show an antibacterial effect against S. mutans . The cooperation of graphite oxide, AgNPs and phthalocyanine molecules promoted lasting disinfection in the presence of near-infrared irradiation . The form of colloidal metal oxide NPs was also proven to have superior antibacterial activity .
Glass ionomer cements (GICs) with a good fluoride-ion release function have been applied to prevent and reduce the occurrence of secondary caries . The copper-doped glass ionomer-based materials greatly enhanced their antibacterial properties and reduced collagen degradation . The addition of titanium dioxide (TiO2) significantly improved mechanical and antibacterial activity .
Hexametaphosphate Nps incorporated in GICs effectively improved antibacterial properties and enhanced fluoride ion release . Nevertheless, ZnO as an additive into GICs could not promote the antimicrobial activity against S. mutans .
The second methodology is the usage of organic NPs to reduce demineralization and achieve remineralization. The nanoparticles of amorphous calcium phosphate (NACP) combined with polymerizable quaternary ammonium methacrylates (QAMs), such as quaternary ammonium polyethyleneimine (QPEI) , quaternary ammonium dimethacrylate (QADM) , dimethylaminohexadecyl methacrylate (DMAHDM) and organic antibacterial NPs was researched. Modified composite incorporating QPEI NPs had excellent antibacterial activity and long-term durability . A composite containing both QADM and AgNPs possessed a stronger antibacterial capability, which lasts for 12 months of water-aging . Antibacterial bonding agents containing DMADDM and AgNPs greatly inhibited biofilm activities such as reducing the metabolic activity, colony forming unit (CFU) and lactic acid of microcosm biofilms, even when the dental adhesive was pre-coated with salivary pellicles .
The combination of DMAHDM, 2-methacryloyloxyethyl phosphorylcholine (MPC) and NACP was also researched . MPC, one of the most common biocompatible and hydrophilic biomedical polymers, was incorporated into dentin bonding agents and composites due to its hydrophilicity that prevents the adsorption of proteins . NACP could release a high level of Ca and P ions, neutralize acids, and inhibit dental caries by matching mechanical properties when containing into resin composites .
A new rechargeable NACP composite with multiple re-release capability was developed for long-term caries inhibition . The methodologies of using NACP, MPC and DMAHDM may be applicable to other dental composites, adhesives and cements to reduce the formation of plaque biofilm in restorative dentistry.
Minimal Invasive (MI) Dentistry
The term "Minimal Invasive (MI) Dentistry" can best be defined as the management of caries with a biological approach, rather than with a traditional (surgical) operative dentistry approach. Where operative dentistry is required, this is now carried out in the most conservative manner with minimal destruction of tooth structure. This new approach to caries management changes the emphasis from diagnosing carious lesions as cavities (and a repeating cycle of restorations), to one of diagnosing the oral ecological imbalance and effecting biological changes in the biofilm. The goal of MI is to stop the disease process and then to restore lost tooth structure and function, maximizing the healing potential of the tooth. The thought process which underpins this new minimal invasive approach can be organized into three main categories:
(1) Recognize, which means identify patient caries risk,
(2) Remineralize, which means prevent caries and reverse non-cavitated caries, and
(3) Repair, which means control caries activity, maximize healing and repair the damage. The disease of dental caries is not just demineralization, but a process of repeated demineralization cycles caused by an imbalance in the ecological and chemical equilibrium of the biofilm /tooth interface (the ecological plaque hypothesis). Dietary and lifestyle patterns, especially carbohydrate frequency, water intake and smoking, play an important role in changing the biofilm ecology and pathogenicity. Tools for chairside assessment of saliva and plaque, allow risk to be assessed and patient compliance monitored. The remineralizing properties of saliva can be enhanced using materials which release biologically available calcium, phosphate and fluoride ions (CPP-ACP and CPP-ACFP). Use of biocides can also alter the pathogenic properties of plaque.
New materials mentioned improve minimal invasive (conservative) dentistry .
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