# Emergence of Nano-Dentistry as a Reality of Contemporary Dentistry
## 4 Discussion
### Conservative Nano-Dentistry
#### 4.1.2 Tooth Restoration Procedures with Nanomaterials  
Nanocomposites  
The major problem of resin composites is that more biofilms and plaques can be accumulated on their surface, compared to other restorative materials. Nanotechnology can aid in the development of bioactive dental materials to reduce or modify the influence of caries-related bacteria. Nanomaterials provide superior antimicrobial activity and display better physical properties in comparison to conventional materials. Agents such as silver, zinc oxide, calcium phosphate, calcium fluoride, quaternary ammonium polyethylenimine, and nanohydroxapatite and/or nanofluorohydoxyapatite are incorporated into restorative materials such as composite resins, glass ionomer cements, and adhesive systems [29]. The summary information of the nanoparticles listed above is given in Table 6[29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40]. One of the mainstreams of nanotechnology, which is widely used in dentistry, is incorporation of nanoparticles in composite materials. Composite resins are the most widely used dental materials for restoring dental cavities, especially because of their biomimetic ability [41]. Nanotechnologies make possible the emergence of materials with completely new characteristics--stronger, lighter, and thinner composite materials, and the quality of many materials can be improved using nanoparticles. Combining these properties in one material has led to the creation of a new class of materials, \"nanocomposites\", in which monomers and nanoclusters are used as fillers [42; 43]. The benefits of \"nanocomposites\" are widely known to dentists. The rationale for use of nanoparticles includes the main indicators that assess the quality of composite materials, namely:  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Name of** & **Advantages/Disadvantages** & \begin{tabular}{c} **Mechanism of** \\ **Co-Interaction** \\ \end{tabular}  & \begin{tabular}{c} **Examples of** \\ **Materials** \\ \end{tabular}  & \begin{tabular}{c} **Reason for Introduction** \\ **into Material** \\ \end{tabular}  \\ \hline \multirow{7}{*}{NAg (nanoparticles of silver)} & \multirow{7}{*}{ \begin{tabular}{c} Antibacterial/can alter \\ color of tooth \\ or restoration \\ \end{tabular}  } & \begin{tabular}{c} A bactericidal effect is \\ achieved by interactions \\ with the peptidoglycan \\ cell wall and the plasma \\ membrane, silver ions \\ prevent bacterial DNA \\ replication by interacting \\ with the exposed \\ sulfhydryl groups in \\ bacterial proteins \\ \end{tabular}  & \begin{tabular}{c} Composite resin; \\ metal adhesives \\ \end{tabular}  & \begin{tabular}{c} NAg and NZnO have \\ been incorporated in \\ dental materials to kill \\ carogenic \\ microorganisms in the \\ material surfaces \\ \end{tabular}  \\ \hline \multirow{7}{*}{ \begin{tabular}{c} NZnO (nano zinc \\ oxide particle) \\ \end{tabular}  } & \begin{tabular}{c} Antibacterial action \\ against several types of \\ microorganisms, \\ including S. Mutans/no \\ evidence about increased \\ mechanical properties \\ \end{tabular}  & \begin{tabular}{c} Bacterial effect is \\ modified cell membrane \\ activity and oxidative \\ stress; these generate \\ active oxygen species such \\ as H\({}_{2}\)O\({}_{2}\) that inhibit \\ growth of planktonic \\ microbes \\ \end{tabular}  & \ \begin{tabular}{c} Bacterial effect is \\ modified cell membrane \\ activity and oxidative \\ stress; these generate \\ reactive oxygen species such \\ as H\({}_{2}\)O\({}_{2}\) that inhibit \\ growth of planktonic \\ microbes \\ \end{tabular}  &
\begin{tabular}{c} \\ \multirow{7}{*}{Composite resin} \\  
high strength, which allows them to be used for restoration and filling procedures on anterior and posterior teeth;
* aesthetics, in particular the ability to manipulate the color shade of restorations in a wide range of values, as well as obtaining a stable shine;
* minimal polymerization shrinkage that would help avoid marginal leakage problems as it is the main reason for secondary caries progression.