The aim of the study is to evaluate how a gel (1.2% lovastatin) applied under the gum improves the results of classic periodontal treatment (SRP-scaling, root planing). The study involves two groups of adults diagnosed with periodontitis: the first group consists of generally healthy individuals who do not smoke tobacco. The second group consists of generally healthy individuals who have been smoking for at least 5 years. Before the study begins, each participant will undergo gum health measurements. Changes in these parameters will be monitored throughout the study. Two teeth will be selected for each participant: * a gel containing the medication will be applied under the gum of one tooth * a gel that looks similar to the medication but does not contain any medicinal substance will be applied under the gum of the second tooth. Before applying the gel, each participant will undergo subgingival cleaning (SRP) to remove any debris that may prevent the medicine from working. The study will last six months. Expected results: * all participants will experience an improvement in the condition of their gums after treatment * the effect of treatment will be better in non-smokers than in smokers * the treatment outcome will be better in the area where the medicated gel was applied compared to areas where the gel without medicinal substances was applied.