**2. Periodontal support tissues**

The periodontium is a complex of tissues with blood vessels, nerves, and bundles of fibers, which provide nutrition and sensibility, supporting and investing the tooth. The periodontium has the potential for regeneration and remodeling throughout life, which allows the primary dentition to be transient and to be

replaced by the permanent dentition [3, 4]. It is important to understand that each of the periodontal tissues has a very specialized structure and that these structural characteristics directly define the function. In fact, the proper functioning of the periodontium is only achieved through the structural integrity and interaction between its components [4].

The periodontium is one of the morphofunctional components of the stomatognathic system, and its "design" not only responds to intrinsic functions related to nutrition or the subjection of the tooth but also to functions integrated within the physiology of the stomatognathic system [5]. The main function of the periodontium is to join the tooth to the bone tissue and maintain integrity on the surface of the masticatory mucosa of the oral cavity [6]. The periodontium includes four tissues located near the teeth: (1) the alveolar bone (AB), (2) root cementum (CR), (3) periodontal ligament (PL), and (4) gingiva (G) (e.g., **Figure 1a**) [4, 7, 8].

#### **2.1 Alveolar bone**

The alveolar bone, together with the root cementum and the periodontal ligament, constitutes the tooth insertion apparatus, whose main function is to distribute the forces generated by chewing and other contacts [6]. The maxilla and mandible of the adult human can be subdivided into two parts: (a) the alveolar process that involves in housing the roots of the erupted teeth and (b) the basal body that does not involve in housing the roots [8].

#### **Figure 1.**

*Periodontal tissues. (a) Tissues that support the tooth include the alveolar bone (AB), root cementum (RC), periodontal ligament (PL), and gingiva (G). (b) Forms of cementum: acellular afibrillar cementum (AAC), acellular extrinsic fibers cementum (AEFC), cellular mixed stratified cementum (CMSC), and cellular intrinsic fibers cementum (CIFC). (c) Bundles of collagen fibers: crestal alveolar fibers (CAF), horizontal fibers (HF), oblique fibers (OF), and apical fibers (AF). (d) Parts of the gingiva: free gingiva (FG), interdental gingiva (IG), and attached gingiva (AG).*

**5**

*Pathogenesis of Periodontal Disease*

work together as a unit [4].

**2.2 Root cementum**

VI, XII, and XIV [4].

**2.3 Periodontal ligament**

oblique fibers (OF), and apical fibers (AF) [6].

*DOI: http://dx.doi.org/10.5772/intechopen.86548*

The alveolar process is the bone of the jaws that contain the sockets (alveoli) of the teeth. It consists of outer cortical plates (buccal, lingual, and palatal) of the compact bone, a central spongiosa, and bone lining the alveolus (alveolar bone) [4]. The alveolar process is dependent on the teeth as they develop and remodel with their formation and eruption. Therefore, the shape, location, and function of the teeth determine its morphology [8]. The periodontal ligament contains progenitor cells that can differentiate into osteoblasts for the maintenance and repair of the alveolar bone. However, in the absence of the tooth, it is lost. These characteristics suggest that the regulatory mechanisms are important for the alveolar bone, so there is an interdependence of the periodontal tissues, which

The root cementum is an avascular mineralized connective tissue covering the entire root surface, forming the interface between the root dentine and the periodontal ligament [6, 7]. In addition, the root cementum plays important roles in nourishing the tooth as well as in stabilizing the tooth via the attachment to the periodontal ligament. This enables the tooth to maintain its relationship to adjacent and opposing teeth [3]. Unlike the bone, the root cementum does not contain blood or lymphatic vessels, lacks innervation, and does not undergo remodeling or physiological resorption, but it is characterized by the fact that continues to be deposited throughout life [6]. The composition of cementum contains about 50% mineral (substituted apatite) and 50% organic matrix. Type I collagen is the predominant organic component, constituting up to 90% of the organic matrix. Other collagens associated with cementum include type I, III, V,

Cementum performs different functions: it fixes the main fibers of the periodontal ligament to the root and contributes in the repair process when the root surface has been damaged [6]. Cementum has been classified as cellular and acellular cementum depending on the presence and absence of cementocytes, further grouped into intrinsic and extrinsic fiber cementum depending on the presence of collagen fibers formed by cementoblasts or by fibroblasts, respectively [8]. There are different forms of cementum (e.g., **Figure 1b**): (1) acellular afibrillar cementum (AAC), (2) acellular extrinsic fiber cementum (AEFC), (3) cellular mixed stratified cementum (CMSC), and (4) cellular intrinsic fibers cementum (CIFC) [4, 6].

The periodontal ligament is the soft and specialized connective tissue situated between the cementum covering the root of the tooth and the bone forming the socket wall (alveolodental ligament) [4]. The periodontal ligament consists of cells and an extracellular compartment comprising collagenous and noncollagenous matrix constituents. The cells include osteoblasts and osteoclasts, fibroblasts, epithelial cell rests of Malassez, monocytes and macrophages, undifferentiated mesenchymal cells, and cementoblasts and odontoclasts. The extracellular compartment consists mainly of well-defined collagen fiber bundles embedded in an amorphous background material, known as ground substance [4, 8]. These bundles of collagen fibers can be classified into the following groups, according to their disposition (e.g., **Figure 1c**): crestal alveolar fibers (CAF), horizontal fibers (HF),

The main function of the periodontal ligament is to support the teeth in their sockets and at the same time allow them to withstand the considerable forces of

#### *Pathogenesis of Periodontal Disease DOI: http://dx.doi.org/10.5772/intechopen.86548*

The alveolar process is the bone of the jaws that contain the sockets (alveoli) of the teeth. It consists of outer cortical plates (buccal, lingual, and palatal) of the compact bone, a central spongiosa, and bone lining the alveolus (alveolar bone) [4]. The alveolar process is dependent on the teeth as they develop and remodel with their formation and eruption. Therefore, the shape, location, and function of the teeth determine its morphology [8]. The periodontal ligament contains progenitor cells that can differentiate into osteoblasts for the maintenance and repair of the alveolar bone. However, in the absence of the tooth, it is lost. These characteristics suggest that the regulatory mechanisms are important for the alveolar bone, so there is an interdependence of the periodontal tissues, which work together as a unit [4].

### **2.2 Root cementum**

*Periodontal Disease - Diagnostic and Adjunctive Non-surgical Considerations*

between its components [4].

**2.1 Alveolar bone**

replaced by the permanent dentition [3, 4]. It is important to understand that each of the periodontal tissues has a very specialized structure and that these structural characteristics directly define the function. In fact, the proper functioning of the periodontium is only achieved through the structural integrity and interaction

The periodontium is one of the morphofunctional components of the stomatognathic system, and its "design" not only responds to intrinsic functions related to nutrition or the subjection of the tooth but also to functions integrated within the physiology of the stomatognathic system [5]. The main function of the periodontium is to join the tooth to the bone tissue and maintain integrity on the surface of the masticatory mucosa of the oral cavity [6]. The periodontium includes four tissues located near the teeth: (1) the alveolar bone (AB), (2) root cementum (CR), (3) periodontal ligament (PL), and (4) gingiva (G) (e.g., **Figure 1a**) [4, 7, 8].

The alveolar bone, together with the root cementum and the periodontal ligament, constitutes the tooth insertion apparatus, whose main function is to distribute the forces generated by chewing and other contacts [6]. The maxilla and mandible of the adult human can be subdivided into two parts: (a) the alveolar process that involves in housing the roots of the erupted teeth and (b) the basal

*Periodontal tissues. (a) Tissues that support the tooth include the alveolar bone (AB), root cementum (RC), periodontal ligament (PL), and gingiva (G). (b) Forms of cementum: acellular afibrillar cementum (AAC), acellular extrinsic fibers cementum (AEFC), cellular mixed stratified cementum (CMSC), and cellular intrinsic fibers cementum (CIFC). (c) Bundles of collagen fibers: crestal alveolar fibers (CAF), horizontal fibers (HF), oblique fibers (OF), and apical fibers (AF). (d) Parts of the gingiva: free gingiva (FG),* 

body that does not involve in housing the roots [8].

**4**

**Figure 1.**

*interdental gingiva (IG), and attached gingiva (AG).*

The root cementum is an avascular mineralized connective tissue covering the entire root surface, forming the interface between the root dentine and the periodontal ligament [6, 7]. In addition, the root cementum plays important roles in nourishing the tooth as well as in stabilizing the tooth via the attachment to the periodontal ligament. This enables the tooth to maintain its relationship to adjacent and opposing teeth [3]. Unlike the bone, the root cementum does not contain blood or lymphatic vessels, lacks innervation, and does not undergo remodeling or physiological resorption, but it is characterized by the fact that continues to be deposited throughout life [6]. The composition of cementum contains about 50% mineral (substituted apatite) and 50% organic matrix. Type I collagen is the predominant organic component, constituting up to 90% of the organic matrix. Other collagens associated with cementum include type I, III, V, VI, XII, and XIV [4].

Cementum performs different functions: it fixes the main fibers of the periodontal ligament to the root and contributes in the repair process when the root surface has been damaged [6]. Cementum has been classified as cellular and acellular cementum depending on the presence and absence of cementocytes, further grouped into intrinsic and extrinsic fiber cementum depending on the presence of collagen fibers formed by cementoblasts or by fibroblasts, respectively [8]. There are different forms of cementum (e.g., **Figure 1b**): (1) acellular afibrillar cementum (AAC), (2) acellular extrinsic fiber cementum (AEFC), (3) cellular mixed stratified cementum (CMSC), and (4) cellular intrinsic fibers cementum (CIFC) [4, 6].
