Periodontitis is a chronic pathology induced by dental biofilm (polymicrobial community) characterized by an inflammatory response mediated by the host's immune system that determines the loss of periodontal attachment [1]. Therefore, it can no longer be considered a simple bacterial infection but must be interpreted as a complex disease with multifactorial etiology [2]. Socransky et al. divided the microorganisms located in subgingival zones into five complexes [3]. One of them, the so-called "red complex", which includes Tannerella forsythensis, Porphyromonas gingivalis and Treponema denticola, is strongly associated with a greater depth of periodontal and/or peri-implant pockets and increased bleeding on probing.
Treatment of periodontal disease is directed towards the removal of the subgingival microflora. Root debridment, scaling and root planing (SRP) are the most widely used therapeutic approach [4, 5]. However, complete mechanical removal in deep periodontal pockets is difficult to accomplish. When exclusively applied, It cannot eliminate the pathogenic microflora due to the localization of the bacteria in soft tissues or in areas not accessible to periodontal instruments [6]. Due to the complex ecosystem within the subgingival pocket, the combined use of mechanical instrumental therapy with antimicrobial agents has been proposed to reduce the need for surgical treatment of the periodontal pockets [7]. Local antimicrobial therapy has the advantage of providing good effective drug concentrations at the site of infection with minimal and low risk of bacterial resistance [6, 8]. Consequently, the clinical use of antibiotics and other antimicrobial agents, as adjuvants for the treatment of periodontitis, has been extensively studied [9–11]. There are currently several antimicrobials on the market, but the need to identify products without the side effects of synthetic drugs [12] is driving research towards natural remedies [13].
Particular attention has been paid to propolis [14–18] for its antibacterial [19], anti-inflammatory and antioxidant [20] activities. Propolis is a resinous substance collected by bees from the buds and bark of plants, in particular in Europe from poplar and birch. It is a substance of purely vegetable origin, even if the bees, after harvesting, process it by adding wax, pollen and enzymes produced by their own body, and use it in the construction, adaptation and protection of hives [14]. The composition of propolis is very complex and it is closely linked to its vegetable origin depending on the phytogeographic characteristics of the collection site and the season of collection [21–23]. Furthermore, the extraction methods and the different solvents used (ethanol, methanol and water) can vary the concentration of the components and influence the properties of propolis producing finished products with different chemical composition and bioactivity. It should be emphasized that propolis used for nutraceutical, medicinal and cosmetic purposes must not contain wood or metal fragments along with bee residues, parasites or harmful substances attributable to the environment and beekeeping practice, such as heavy metals and acaricides [24]. Propolis contains more than 300 different biocompounds that can be divide into main large groups [25–27] constituted of resins (~ 45–55%), wax and fatty acids (~ 25–35%), essential oils and volatile substances (~ 10%), and pollen (~ 5%). Particular mention deserves the group of flavonoids which are contained in large quantities in the resin of propolis (up to 20% of weight) [28]. They are endowed with a high chemical reactivity, anti-free radical action, anti-inflammatory, antithrombotic, vaso- and gastro-protective, and immunological activity. The bee modifies the structure of flavonoids originally present in plants by removing the sugars contained in the organic compounds thanks to the enzymes produced by their salivary glands [29]. The synergy of the action of the various components of propolis focus the attention not on a single compound but on the properties of its phytocomplexes.
Many studies have demonstrated the multiple biological activities of propolis [30–36] and highlighted its properties in the dental field [13, 37–39]. In fact, the antimicrobial activity of propolis against various periodontal pathogens has been largely demonstrated, including Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum and Prevotella intermedia [40, 41]. Moreover, propolis samples were observed to have a broad spectrum of antimicrobial activity against vancomycin- and methicillin-resistant Streptococcus aureus [19] and Enterococcus faecium [41]. The antimicrobial properties of propolis against oral pathogens are attributable to the flavonone pinocembrina, the flavonol galangin and the phenethyl ester caffeic acid (CAPE) with the mechanism of action probably based on the inhibition of bacterial RNA-polymerase [40]. Finally, the antibacterial properties of propolis on periodontopathogenic bacteria have been confirmed by other authors [9, 40, 42, 43].
The aim of the study is to evaluate the efficacy of a standardized sample of propolis associated with the Scaling and Root Planing (SRP) treatment in comparison with an antiseptic of proven efficacy, 1% chlorhexidine gel, and with only SRP treatment, in patients with chronic periodontitis, by evaluating the clinical parameters. Due to the considerable variability of the different types of propolis used in the various studies available in the scientific literature, a propolis extract with standardized polyphenolic composition and content was used in this research.