## 3 Results  
We explored the possibility of using the bioactive healing abutment (BHA) as an antibiotic carrier. The functional idea of the proposed BHA is based on the slow release of the substance on an appropriate carrier, deposited in the abutment chamber to the surrounding environment through the adjacent side openings. The standard healing abutment is commonly used in dental implantology for the healing of gums surrounding an implant bed, in order to allow attachment of the implant superstructure. However, it is in one piece, solid, and has a purely mechanical function--blocking and shaping of gum epithelialization over the implant bed after it has been uncovered. In the proposed version, the BHA, made with class V titanium (Ti6 Al4V), has an empty core and two parts: a corpus and a top lid. The corpus has screws allowing for attachment of the implant main body and a chamber for drug deposition. This chamber is connected with the external environment by eight equally distributed openings on the side walls, each with a diameter of 1 mm. The abutment is 5 mm long and the attachment screws and base diameter are adjusted to the TAV Dental Silhouette (Israel) implant bed with a diameter of 3.75 mm. The achieved capacity of the BHA chamber used in the experiment is, after the lid is screwed on, 0.019764 mL each (Figures 1-3). Figure 1: Bioactive healing abutment scheme. Figure 2: Bioactive healing abutment idea of action: (**A**) treatment with bioactive healing abutment; and (**B**) implant restoration after treatment. We first selected two antibiotics--clindamycin and tetracycline--to examine the antibacterial activity in _S. aureus_ and _S. epidermidis_, respectively. The antibacterial activity of antibiotics was analyzed by disk diffusion assay in two trials with BHA and paper discs (Figure 4). Table 1 lists the inhibition zone diameter of \(19.9\pm 2.3\) mm for clindamycin and \(15.5\pm 2.7\) mm for tetracycline for _S. aureus_; \(31\pm 0.6\) mm for clindamycin and \(11,3\pm 0.3\) mm for tetracycline for _S. epidermidis_ in the first trial (paper discs). In Table 1, a mild increase in the inhibition zone diameter can be observed in clindamycin and tetracycline in the second trial with BHA: \(27.4\pm 2.5\) mm and \(18.8\pm 3.4\) mm, respectively, for _S. aureus_ and \(34.7\pm 2.3\) mm and \(13\pm 3.0\) mm, respectively, for _S. epidermidis_. In the obtained results, statistically significant differences were observed for the individual study groups for the different antibiotic carriers (paper disc or BHA) in the case of the _S. aureus_ strain. The control study group, based on the antimicrobial activity of a titanium disc for individual bacteria cultures, showed homogenous and undisturbed micro-organism growth. No zone diameter \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Antibiotic** & \multicolumn{2}{c}{**Clindamycin 2 ug**} & \multicolumn{2}{c}{**Tetracycline 30 ug**} \\ \hline Bacterial strain & _Staphylococcus aureus_ & _Staphylococcus epidermidis_ & _Staphylococcus aureus_ & _Staphylococcus epidermidis_ \\ \hline Paper disc (mm) & \(19.9\pm 2.3\) & \(31\pm 0.6\) & \(15.2\pm 2.7\) & \(11.3\pm 0.3\) \\ \hline Bioactive healing & \(24.4\pm 2.5\) & \(34.7\pm 2.3\) & \(18.8\pm 3.4\) & \(13\pm 3.0\) \\ \hline Difference (mm) & \(4.5\pm 0.1\) & \(3.7\pm 2.4\) & \(3.7\pm 0.7\) & \(1.7\pm 3.0\) \\ \hline \(p\) & \(0.0000043\) & \(0.2018\) & \(0.00041\) & \(0.6164\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of median zone diameter breakpoint using a paper disc and bioactive healing abutment depending on antibiotic type and bacterial strain. Zone diameter breakpoint, mm; \(n=3\). Figure 4: Experimental scheme for the disk diffusion assay. Figure 3: Bioactive healing abutment structure and dental implant fixation: 1. Drug chamber vertical view; 2. Corpus and lid horizontal view; 3. Bioactive healing abutment with closed lid; 4. Bioactive healing abutment with closed lid mounted on the dental implant.