**5. Discussion**

Currently, only one study assessing clinical and microbiological effectiveness of locally applied piperacillin with tazobactam in patients with periodontitis is available.

Lack of placebo application may constitute a limitation of the study; both the person who collected the material and the laboratory staff were subjected to a blind test.

In our own studies on clinical parameters, such as bleeding on probing (BoP) index, periodontal pocket depth (PPD), and location of the connective tissue attachment (CAL), the following results were obtained after 2 months: BoP was reduced (−49.2% vs. 47.5% for SRP), the average PPD was shallowed (0.82 vs. 0.83 mm for SRP), and additionally, attachment location in the control pockets was improved (−0.81 mm). On the other hand, after 2 months of treatment, no differences in the assessed clinical parameters between the two groups were observed. In the studies conducted by Lauenstein et al. [9,10], in which piperacillin with tazobactam were applied locally, similar reduction in the values of clinical parameters was obtained. The difference in PPD measurements between the initial examination and the examination conducted in the control group after 26 weeks was 1.8 mm (SE ± 0.3; 95% CI 1.2, 2.3; *p* < 0.001). The average difference in PPD between the initial value and the 26th week in the study group was 1.5 mm (SE ± 0.2; 95% CI 1.1, 2.0; *p* < 0.001), and the statistical analysis did not show any differences in the study groups in terms of PPD values both at the beginning of the study and in its 26th week. Moreover, in the case of the parameter assessing inflammation (BoP) no statistically significant differences between the groups were proven, neither at the beginning of the study nor during the final

examination after 26 weeks. The fact that the study included smokers may constitute a disruptive factor [10]. The obtained reduction in the clinical parameters confirms the necessity of conducting nonsurgical treatment, especially in terms of reducing periodontal pocket depth and the location of connective tissue attachment, and confirms the gold-standard status of the scaling and root planning procedure in periodontal treatment [11–13]. Mechanical cleaning is necessary in order to improve clinical parameters, and the applied preparations can only support and consolidate the treatment results [14,15].

With regard to the microbiological tests, there are currently no reports confirming effective reduction of periopathogens in periodontal pockets after local application of piperacillin in combination with tazobactam in patients with moderate and advanced periodontitis. No statistically significant differences between the studied groups were found in our own studies. After local application of Gelcide in combination with SRP, a significant increase in *Treponema denticola* and decrease in *Micromonas micros* as well as a considerably higher number of *Capnocytophaga gingivalis* were found in the microbiological test in relation to the control pockets. After application of SRP alone, a decrease in the number of *Fusobacterium nucletaum* and *Micromonas micros* was observed. In the studies conducted by Lauenstein et al. [10], reduction in pathogens (including *Porphyromonas gingivalis, Tanerella forsythia,* or *Agregatibacter actinomycetemcomitans*) after local application of piperacillin with tazobactam, in comparison with application of only mechanical cleaning, was obtained in both groups after 26 weeks. On the other hand, significant reduction of *Fusobacterium nucleatum, P. micra*, and *T. denticola* was obtained in the group in which the treatment was combined with local antibiotic therapy.

Due to bacteria organization within the biofilm present in the periodontal pockets and the presence of periopathogenic bacteria in the tissues of the host, eradication of periopathogens and long-term improvement of clinical and in particular, microbiological parameters, is virtually impossible. In the case of local application of doxycycline, the results of clinical and microbiological tests are inconclusive. Reports on considerable improvement of clinical parameters and reduction in periopathogens after SPR combined with intrapocket administration of antibiotic [16,17] are available. Long-term observations, however, do not indicate considerable benefits [18]. At the same time, some scientists do not prove significant differences in results with regard to the independent use of SRP in periodontal disease treatment [19]. Difficulties in obtaining complete reduction of periopathogens, regardless of the type of therapy, were also presented in the studies by Mobelli et al. [20] after local application of tetracycline fibers [21]. The study included seventeen patients, with whom microbiological analysis of subgingival samples collected mesially–distally from 852 areas at the beginning and after a month of using the preparation was conducted. In the basic study, 46 samples, from 10 positive individuals, showed positive results for *P. gingivalis*; 82 samples, from 5 individuals, were also identified as positive in terms of *A. actinomycetemcomitans*. The presence of *A. actinomycetemcomitans* and *P. gingivalis* was not confirmed in the material collected from 3 patients. Microbiological tests conducted one month after periodontal treatment showed that 89% of areas which initially showed positive results in terms of pathogens were negative, while 16 areas which were initially identified as negative showed positive results. With regard to *A. actinomycetemcomitans*, 77% of areas which were identified as positive in terms of bacteria presence in the first test were later identified as negative, but 5 areas which were initially identified as negative showed positive results. During the examinations of patients whose results of the microbiological test remained positive, another attempt at applying local treatment using tetracycline fibers was made. Despite another attempt at treatment, microbiological tests still showed the presence of *P. gingivalis* in 5 individuals; and in 4 patients, the results for *A. actinomycetemcomitans* remained positive. Those 9 patients were finally subjected to systemic antibiotic treatment (3 × 250 mg metronidazole and 3 × 375 mg amoxicillin/per day for 7 days). Despite all the efforts, after 3 months *P. gingivalis* was again detected in 3 individuals and *A. actinomycetemcomitans* was isolated from 1 area.

Organization of periopathogens within the biofilm, their diversity, and ability to quickly recolonize bacteria still constitutes a grea<sup>t</sup> therapeutic challenge. Nonsurgical methods (SRP) are still the basis for treatment of periodontium diseases, and local or general application of antibiotic therapy is still ine ffective in terms of periopathogen elimination [22]. In summary, this study showed similar improvement of clinical parameters in patients treated with SRP combined with single administration of local antibiotic (piperacillin/tazobactam) or without it, without showing statistically significant di fferences in the microbiological tests results. Piperacilin in combination with tazobactam is used primarily for the general treatment of nosocomial infections. Clinical data indicate that the combination of piperacillin/tazobactam is e ffective in the treatment of moderate to severe polymicrobial infections, including intra-abdominal, skin, and soft-tissue and lower respiratory tract infections. It shows high e fficiency in the case of infections caused by *Escherichia coli,* many *Bacteroides* and *Klebsiella species, Staphylococcus aureus,* and *Haemophilus influenzae*, with low resistance after the treatment. The combination of piperacillin and tazobactam in dentistry has been not well documented. There are no medical studies that investigate the e ffectiveness against pathogens that cause periodontitis. Despite the broad spectrum of gram-negative bacteria, there is no evidence of the e ffects on periopathogens. It should be emphasized that, in the case of topical application in periodontal pockets, there is currently no available literature. It is required to conduct clinical trials confirming the spectrum of the drug's action on periopathogens, together with correlation of the clinical results. In vitro studies should also be considered to systematize and confirm the e fficacy of piperacillin/tazobactam on specific periopathogens.

Further clinical studies on larger groups of patients and long-term observations of the obtained results or changes occurring in them in order to optimize the algorithms of nonsurgical treatment of periodontal diseases and minimize application of general antibiotic therapy is required.

**Author Contributions:** Author A.S.-J. caried SRP, author J.Z. carried drug administration and article review and editing, author M.S. carried study design and draft preparation, author T.K. carried examination and project supervision.

**Funding:** This research received no external funding

**Conflicts of Interest:** The authors declare no conflict of interest.
