Chronic obstructive pulmonary disease (COPD) is characterized by irreversible, limited flow of air through the respiratory tract, related to a chronic inflammatory process in lung vessels, destruction of lung parenchyma, and progressive morphological changes in pulmonary alveoli (Murray and Lopez 1997). COPD mainly develops in active and passive smokers or persons exposed to air pollution. The course of the disease depends on patients’ general health, age, and the existence of comorbidities. COPD is currently one of the leading health issues in the world and is projected to be the third most common cause of death by 2020, one which substantially diminishes the quality of life (Zhou et al. 2011). Patients with frequent exacerbations require hospitalization and increasing financial expenditure for medical services. Infections constitute the main cause of exacerbations in the course of COPD, whereas a significant part of nosocomial pneumonias is initiated through the aspiration to the lower respiratory tract of opportunistic bacteria colonizing oral cavity and nasopharynx. Microorganisms mainly causing pneumonia in the course of COPD belong to the commensal bacterial flora colonizing the epithelium of the nasopharynx: Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae. In patients with severe COPD exacerbations, following types of bacteria are isolated from saliva: Pseudomonas aeruginosa, Escherichia coli, and Proteus mirabilis (Sethi 2010). Chronic local and systemic inflammation related to the colonization of bacteria in the respiratory tract impairs the mucociliary clearance, leading to the destruction of pulmonary alveoli and obturation of the respiratory tract. The etiology of COPD exacerbations depends on the severity of the disease, their frequency of appearance, and the applied antibiotics. Patients with COPD belong to the group of persons with acquired immunodeficiency, who are at risk of Candida infections and bacteremia. Chronic local oral cavity inflammation and systemic inflammation impair the mechanisms of humoral and cell-mediated immunity, which promotes the colonization of upper and lower respiratory tract pathogens. Hospitalized patients with advanced COPD are at the highest risk of developing pneumonia and bronchitis (Murphy 2006; Didilescu et al. 2005; Scannapieco et al. 2003).

Over the past decade there has been an increased interest in the link between respiratory tract diseases and infections within oral cavity and nosopharynx (Paju and Scannapieco 2007; Scannapieco 2006; Mojon 2002). Microorganisms exist in the oral cavity not in the form of single cells, but as organized structures forming an ecological niche called biofilm. The ability to form biofilm decides about the pathogenicity of the microorganism, and in this way directly influences the soft tissues of the upper respiratory tract. Their products have been shown to stimulate mucin secretion and may result in the release of antigens, including endotoxins, lipoproteins, peptidoglycans, and other molecules enhancing the effectiveness of anti-inflammatory activities in the respiratory tract and the whole body. Previous research indicates that insufficient oral cavity hygiene contributes to the development of pneumonia. A significant part of nosocomial pneumonias is initiated through the aspiration into lower respiratory tract of bacteria colonizing oral cavity (Scannapieco 2006).

Removable prosthetic restorations create convenient conditions for the growth of bacterial and fungal microflora in the oral cavity. Broad denture plaque impedes the saliva flow and its antiseptic action, limits the ingress of oxygen to the mucous membrane epithelial cells, causes a pH decrease and an increase in temperature, as well as contributes to the build-up of food debris. Elderly patients use dentures for many years, without appearing for control visits to reline them or replace with new ones. Poor stability and retention of prosthesis related to this fact becomes a traumatogenic factor for the oral cavity mucous membrane. Among COPD patients, predominate elderly persons using removable prosthetic restorations made of acrylic materials. These materials are characterized by porosity and surface roughness, which promote the adherence of microorganisms, food debris, and the formation of biofilm of the denture plaque. Strong acrylic surface adherence is shown by Candida albicans, owing to the presence of phospholipases and other hydrolytic enzymes. Poor hygiene of oral cavity and prosthetic restorations promotes the build-up of bacterial-fungal plaque, which interacts directly with the mucous membrane of the prosthetic area (Sumi et al. 2002). In certain patients, denture plaque contributes to the development of prosthetic stomatitis, a chronic local inflammation of the oral cavity mucous membrane. Denture stomatitis mostly concerns removable dentures, and affects from 15 % up to 70 % of denture users. Among the risk factors for the occurrence of stomatitis are: Candida spp fungal infections, mechanical damage, poor oral hygiene, and round-the-clock use of dentures (Ramage et al. 2004).

COPD patients are encumbered with a high risk of bacterial and fungal infections, particularly Candida spp. Our previous studies indicate that multiple pathogenic species related to pneumonia have been isolated from the removable denture plaque of COPD patients. Sixteen bacterial strains responsible for exacerbations of the disease have been identified, including: S. aureus, P. aeruginosa, E. coli, K. pneumoniae, and Serratia spp. COPD patients show poorer denture hygiene and prosthetic stomatitis complicated by fungal infection, being more frequent that could be explained by the use of chronic inhalation glucocorticosteroids and home oxygen therapy in this group of patients (Przybyłowska et al. 2015).