# Dental Hydrogels with Essential Oils with Potential Activity in Periodontitis
## 3 UV-Vis Absorption Spectroscopy of the Hydrogels
### Antimicrobial Activity of the Experimental Gels Containing Natural Essential Oils
Natural materials are made up of a variety of chemical structures with a range of biological functions. They are hence the focus of discussion in this decade. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Total Amount** & **Dilution** & \begin{tabular}{c} **Quantity/Concentration** \\ **of Essential Oil (\(\upmu\)L)** \\ \end{tabular} & \begin{tabular}{c} **Gel without** \\ **of Essential Oil (\(\upmu\)/\(\upupsilon\)%)** \\ \end{tabular} & \begin{tabular}{c} **Gel with** \\ **Essential Oil** \\ \end{tabular} & \begin{tabular}{c} **Gel with** \\ **Oregano®** \\ \end{tabular} & \
\begin{tabular}{c} **Gel with** \\ **Thieves®** \\ \end{tabular} &
\begin{tabular}{c} **Gel with** \\ **Frankicense®** \\ \end{tabular} \\ \hline
50 & D1:1 & 2.2 & n.a & & & & \\  & D1:2 & 0.11 & n.a & & & + \\  & D1:3 & 0.072 & n.a & + & + & \\  & D1:4 & 0.055 & n.a & & & \\  & D1:5 & 0.044 & n.a & & & \\ \hline \end{tabular} n.a—not active. + = means that there was found the minimum inhibitory concentration.  
\end{table} 
Table 2: Bacteriostatic effect: MIC (minimum inhibitory concentration). \begin{table}
\begin{tabular}{c c c c c} \hline
**Type of Gels** & _S. aureus (mg)_ & _B. cereus (mg)_ & _E. fecalis_ (mg)_ & _E. coli (mg)_ \\ \hline Gel without oil & n.a & n.a & n.a & n.a \\ Gel with Oregon® & 16.8/16 1 & 11.15/8.4 1.3 & 8.4/8.4 1 & 8.4/8.4 1 \\ Gel with Thieves & 11.15/11.15 1 & 11.15/11.15 1 & n.a & n.a \\ Gel with Frankincense® & 11.15/11.15 1 & 11.15/11.15 1 & 8.4/8.4 1 & 8.4/8.4 1 \\ \hline \end{tabular} n.a.–not active. MIC/MBC ratio = 1, which represents the bactericidal effect.  
\end{table} 
Table 3: Antibacterial activity (MIC/MBC index). Due to their overall efficacy and safety, herbal medications have been utilized to treat periodontal disease [23]. The first studied compound was the Thieves(r) blend gel, in which four main constituents have different biological roles. Eugenol is said to have positive effects on human health, which is supported by a substantial body of contemporary scientific research. It is one of the major constituents of Clove (_Syzygium aromaticum_) oil. These effects are mostly linked to anti-inflammatory and antioxidant properties. In investigations, eugenol has also demonstrated exceptional antibacterial action, being effective against fungi and a variety of gram-positive and gram-negative bacteria [24]. In general, monoterenes alter the characteristics of the plant they are found based on their natural habitat. For instance, citral is a key ingredient in lemon's aroma. Mandarin orange flavor is influenced by thymol. Other monoterenes that are components of flower smells and draw pollinators to plants include limonene and geranyl. Menthol, camphor, carvone, thymol, fenchone, and a-pinene are a few examples of monoterenes that are significant commercially. Cienole, citral, geraniol, linalool, and menthol are other examples of monoterenes that were evaluated against several bacterial strains, including gram-positive cocci and rods, gram-negative rods, and yeast-like and filamentous fungi [25]. _Salmonella typhimurium_ and _Staphylococcus aureus_ viable counts have been demonstrated to be significantly reduced by EO of thyme or its component thymol, which is another constituent of our experimental gel. The chemically similar terpen p-cymene and y-terpinene displayed no antagonistic effects against \(S\). _typhimuriumium_, in contrast to the phenolic components of the oil, thymol, and carvacrol [25,26]. The monoterenes, which made up 84.86% of the total and were primarily composed of \(\alpha\)-pinene and D-limonene, were also a defining characteristic of the experimental Frankincense(r) essential oil gel. The majority of the monoterpenoids found in medicinal plants' essential oils, such as limonene, myrcrene, \(\alpha\)-terpineol, linalool, \(\beta\)-pinene, p-cymene, and endo-Borneol, are present.