**Abstract**

The 2017 World Workshop on the Classification of Periodontal and Peri-implant Diseases and Condition identified the gingivitis case by the presence of gingival inflammation at one or more sites and agreed upon bleeding on probing as the primary parameter for diagnosis of gingivitis. Clinical gingival health is generally associated with an inflammatory infiltrate and a host response consistent with homeostasis. The molecules that play a role in the pathogenesis are divided into two main groups: those derived from the subgingival microbiota (i.e., microbial virulence factors) and those derived from the host immune-inflammatory response. The immune system is essential for the maintenance of periodontal health and is categorized as innate immune system and the adaptive immune system. Innate immunity reflects the capacity of the host to defend against infectious attacks. Understanding the disease processes is important for the development of improved treatment strategies.

**Keywords:** pathogenesis, immune response, host susceptibility, inflammatory mediators

#### **1. Introduction**

Chronic gingivitis and periodontitis are chronic inflammatory lesions which display stages of inflammation as well as healing. The 2017 World Workshop on the Classification of Periodontal and Peri-implant Diseases and Condition identified the gingivitis case by the presence of gingival inflammation at one or more sites and agreed upon bleeding on probing as the primary parameter for diagnosis of gingivitis [1, 2]. Clinical gingival health is generally associated with an inflammatory infiltrate and a host response consistent with homeostasis.

The role of the immune response in periodontal destruction independent of bacteria was first described by Ivanyi et al. [3]. Later, Taubman et al. [4] studied the role of the immune response in a germ-free rat model of experimental periodontal disease and concluded that in order to control the disease, it would be crucial to enhance the protective "arm" of the immune response and suppress its destructive aspect [4]. The molecules that play a role in the pathogenesis are divided into two main groups: those derived from the subgingival microbiota (i.e., microbial virulence factors) and those derived from the host immune-inflammatory response. Even though "periopathogenic bacteria" are still regarded as the main initiating agents, immune-inflammatory response of the host to these pathogens plays an important role in the pathogenesis of PD [5].
