Gram-negative bacteria and the host inflammatory response which results in tissue destruction and tooth loss [2]. In the past two decades, many researchers have provided an increasing body of scientific evidence suggesting that moderately untreated periodontitis are associated with systemic health conditions such as cardiovascular disease, diabetes, and pre-term low birth weight [3]. These diseases are widely prevalent and are associated with an overall burden of the human health. Chronic obstructive pulmonary disease (COPD) is one of the most common and costly respiratory diseases. COPD is characterized by a slower progressive and irreversible airflow obstruction and the loss of lung tissue which leads to emphysema and tissue remodeling (fibrosis), both of which contribute to a further lung function decline and high mortality [4-6]. In COPD patients, a fixed airflow limitation often results in symptoms such as dyspnea, cough, and sputum production. It is currently the fourth leading cause of death worldwide and is projected to be the third cause of death in the developed countries by 2020 [7]. The association between periodontitis and COPD has been widely investigated. The anatomical continuity between the lungs and the oral cavity makes the latter a potential reservoir of the respiratory pathogens [8]. The exacerbation of COPD was reduced after periodontal treatment [9]. The possible association between periodontitis and COPD was shown in Figure 1. Epidemiological Studies Several studies have revealed an association between lung diseases and poor oral health, such as: 1) Alveolar bone injury; 2) Periodontal attachment loss; 3) Oral hygiene index; and 4) Oral plaque colonization [10-14].