# 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  
The increased bacteriostatic potential was recorded for the gel supplemented with Thieves(r) essential oil and Oregon(r) essential oil at dilution no. 3 = 16.6 \(\mu\)L containing 0.036 \(\mu\)L of essential oil against the _Staphylococcus aureus_ strain, while the bacteriostatic potency of the gel supplemented with Frankincense(r) essential oil was observed only at \(\sfrac{1}{2}\) of the dilution involving the use of a volume of 25 \(\mu\)L of gel containing an amount of 0.055 \(\mu\)L of essential oil. The same results were also obtained against the _Bacillus cereus_ strain. A higher bactericidal potential indicated the gel supplemented with Oregon(r) essential oil for all studied bacterial strains, especially against _Bacillus cereus_ strain, having  
Figure 9: D1 MSCs cells viability assessment after treatment with control gel and gel with Frankincense® essential oil, where Control = D1 MSCs cells in normal propagation medium; G1, 2, 3, 4 = the gel without essential oil in 4 different concentrations (2.4; 4.7; 7 and 9% (\(\
icefrac{\
u}{\
u}\))); F = the gel with Frankincense® essential oil in 4 different concentrations of gels (2.4; 4.7; 7 and 9% (\(\
icefrac{\
u}{\
u}\))), **\(p<0.001\)**. potency at the 4 th dilution (10 \(\upmu\)L) of the gel. A similar biological effect was observed for a gel with Frankincense oil, noting a lower efficacy against the _Bacillus cereus_ strain. Thieves essential oil supplemented gel did not appear to have a bactericidal effect against _Escherichia coli_ and _Enterococcus faecalis_ strains compared to the other two essential oils, but results are similar against _Staphylococcus aureus_ and _Bacillus cereus_ strains, respectively (Table 2). Bactericidal efficacy was demonstrated against all tested bacterial strains for gels supplemented with Oregon(r) and Frankincense(r) essential oil, but gels supplemented with Thieves(r) essential oil expressed bactericidal potential only against _S. aureus_ and _B. cereus_ strains (MBC/MIC \(\leq\) 4--this means the composites have a bactericidal effect and if MBC/MIC = 4, the composites have only bacteriostatic effect) (Table 3). Thieves(r) essential oil-supplemented gel did not appear to have a bactericidal effect against _Escherichia coli_ and _Enterococcus faecalis_ strains compared to the other two essential oils, but results are similar against _Staphylococcus aureus_ and _Bacillus cereus_ strains, respectively (Table 3). Dental hydrogels should be biocompatible and offer a non-toxic delivery mechanism with the regulated release of substances containing natural extracts. These extracts are primarily effective at local therapy, either by themselves or in combination with more traditional techniques such as mechanical cleaning or laser-assisted photodynamic therapy. These kinds of hydrogels with essential oils embedded could be used in a single treatment to reduce patient expenditures and possibly treat chronic mouth diseases. Nevertheless, the biological properties these gels possess make them perfect candidates for oral procedures, which contain natural products which are safe for oral cavity tissues and exhibit not only protective effects but also regenerative potential for soft and hard tissues. Research on innovative drug delivery devices focuses on designing multiple delivery systems for active substances, preventing drug side effects, and reducing dosing intervals [20]. Essential oils are great antibacterial, antifungal, antioxidant, and anti-inflammatory effects that can be augmented by combining them with nanotechnological designs [21]. Herbal materials, which have antibacterial, anti-inflammatory, and antioxidant properties, are widely and frequently utilized in the treatment of numerous oral illnesses that affect the periodontium, including periodontitis. Numerous studies support the positive effects of phytotherapy in treating periodontitis [22].