**2. Dental anatomy of dogs**

As in most domestic mammals and in humans, dogs have diphyodont dentition, featuring two sets of teeth, a deciduous or primary and a permanent, although edentulous at birth (Harvey, 1992).

The oral anatomy of dogs has subdivisions and similar structures to those of humans (Figure 1), differing in the shape of the cavity, which also varies between breeds (Roza, 2004), anatomy and quantity of teeth and in the teeth apex (Harvey & Emily, 1993). Dogs

Periodontal Disease in Dogs 121

For a better understanding of periodontal disease it is important to have further information about a set of structures that constitute the alveolar-dental joint, the

The periodontium (peri, around; dental, tooth) (Lindhe & Karring, 1997) is the set of hard and soft tissues (Mitchell, 2005) that support (Harvey & Emily, 1993, Domingues et al., 1999), by fixing, adhering (Lindhe & Karring, 1997; Roza, 2004) and protecting the tooth in the alveolar bone (Roza, 2004). The structures that comprise the periodontium are the periodontal ligament, cementum, gingiva and alveolar bone (Carranza, 1983; Lindhe & Karring, 1997; Wiggs & Lobprise, 1997). There is a division of these structures according to their functions, so there is a periodontal support formed by the cementum, the periodontal ligament, alveolar bone, and gingiva that besides participating in the support also comprises

The gingiva (Figure 1) is the part of the masticatory mucosa that surrounds the cervical portion of the tooth and covers the alveolar process (Lindhe & Karring, 1997). Its main function is to protect structures adjacent to the tooth, being the first line of defence against periodontal disease (Harvey & Emily, 1993). Two parts can be distinguished: the free and

The free gingiva can be pink or pigmented in some breeds, with firm consistency and an opaque surface (Lindhe & Karring, 1997). The margin of the free gingiva is the edge of it. Between the free gingiva and the tooth, a groove is formed (Mitchell, 2005) known as the gingival sulcus, which, in normal conditions in the dogs, varies in depth from one to three millimeters (Harvey & Emily, 1993; Roza, 2004). The sulcus is surrounded by an adhered epithelium that secretes a fluid with inflammation mediatory cells, immunoglobulins and antibacterial substances important in the physical and immunological protection of the

The junctional epithelium (Figure 1) is located at the bottom of the sulcus, with flat and elongated cells (Hennet, 1995; Wiggs & Lobprise, 1997) adhering to the enamel through hemidesmosomes, promoting the junction between the gingiva and the tooth (Harvey & Emily, 1993). The junctional epithelium ends in the cementum-enamel junction (Roza, 2004). In processes such as inflammation, hyperplasia or in both, the junctional epithelium can recede apically or the gingiva can increase, making deeper the gingival sulcus (Harvey & Emily, 1993). In gingival hyperplasia the deepening of the sulcus occurs without loss of periodontal tissue, named false pocket, although when there is a loss of the support tissue and protection of the tooth, the sulcus is called periodontal pockets, which can be of two types: suprabone, when the bottom of the sulcus is coronal to the support alveolar bone, and intrabone, when the bottom is located apically in relation to the adjacent alveolar bone. The pocket depth can vary between regions of the mouth and even between neighbouring teeth

The attached gingiva (Figure 1) is the continuation of the free gingiva, that, is firmly attached to the underlying bone, and extends to the mucogingival junction (Carranza, 1983). Cementum (Figure 1) is a hard tissue with no vascularity (Harvey et al. 1994; Hennet, 1995) that covers the tooth root (Mitchell, 2005), is composed of collagen fibres embedded in an organic matrix, and has in its mineral portion, which is responsible for about 65% of its

periodontium (Picosse, 1987).

the protection periodontium (Roza, 2004).

attached gingiva (Harvey & Emily, 1993; Lindhe & Karring, 1997).

junctional epithelium and deeper tissues (Pope, 1993).

(Newman et al., 2004).

have, like humans, incisors, canines, premolars and molars, differing among themselves in functions and numbers of roots (Roza, 2004; Mitchell, 2005).

Fig. 1. Structures of dental organ in dogs

Domestic dogs have in their primary teeth, 28 teeth (12 incisors, four canines, 8 premolars and 4 molars), and in the permanent, 42 teeth (12 incisors, four canines, 16 premolars and 10 molars) (Roza, 2004). Regardless of the number of roots, function, size and shape, the teeth have subdivisions that are common to all types (Roza, 2004), and form the dental organ together with some adjacent structures (Gioso, 2007).

have, like humans, incisors, canines, premolars and molars, differing among themselves in

Domestic dogs have in their primary teeth, 28 teeth (12 incisors, four canines, 8 premolars and 4 molars), and in the permanent, 42 teeth (12 incisors, four canines, 16 premolars and 10 molars) (Roza, 2004). Regardless of the number of roots, function, size and shape, the teeth have subdivisions that are common to all types (Roza, 2004), and form the dental organ

functions and numbers of roots (Roza, 2004; Mitchell, 2005).

Fig. 1. Structures of dental organ in dogs

together with some adjacent structures (Gioso, 2007).

For a better understanding of periodontal disease it is important to have further information about a set of structures that constitute the alveolar-dental joint, the periodontium (Picosse, 1987).

The periodontium (peri, around; dental, tooth) (Lindhe & Karring, 1997) is the set of hard and soft tissues (Mitchell, 2005) that support (Harvey & Emily, 1993, Domingues et al., 1999), by fixing, adhering (Lindhe & Karring, 1997; Roza, 2004) and protecting the tooth in the alveolar bone (Roza, 2004). The structures that comprise the periodontium are the periodontal ligament, cementum, gingiva and alveolar bone (Carranza, 1983; Lindhe & Karring, 1997; Wiggs & Lobprise, 1997). There is a division of these structures according to their functions, so there is a periodontal support formed by the cementum, the periodontal ligament, alveolar bone, and gingiva that besides participating in the support also comprises the protection periodontium (Roza, 2004).

The gingiva (Figure 1) is the part of the masticatory mucosa that surrounds the cervical portion of the tooth and covers the alveolar process (Lindhe & Karring, 1997). Its main function is to protect structures adjacent to the tooth, being the first line of defence against periodontal disease (Harvey & Emily, 1993). Two parts can be distinguished: the free and attached gingiva (Harvey & Emily, 1993; Lindhe & Karring, 1997).

The free gingiva can be pink or pigmented in some breeds, with firm consistency and an opaque surface (Lindhe & Karring, 1997). The margin of the free gingiva is the edge of it. Between the free gingiva and the tooth, a groove is formed (Mitchell, 2005) known as the gingival sulcus, which, in normal conditions in the dogs, varies in depth from one to three millimeters (Harvey & Emily, 1993; Roza, 2004). The sulcus is surrounded by an adhered epithelium that secretes a fluid with inflammation mediatory cells, immunoglobulins and antibacterial substances important in the physical and immunological protection of the junctional epithelium and deeper tissues (Pope, 1993).

The junctional epithelium (Figure 1) is located at the bottom of the sulcus, with flat and elongated cells (Hennet, 1995; Wiggs & Lobprise, 1997) adhering to the enamel through hemidesmosomes, promoting the junction between the gingiva and the tooth (Harvey & Emily, 1993). The junctional epithelium ends in the cementum-enamel junction (Roza, 2004).

In processes such as inflammation, hyperplasia or in both, the junctional epithelium can recede apically or the gingiva can increase, making deeper the gingival sulcus (Harvey & Emily, 1993). In gingival hyperplasia the deepening of the sulcus occurs without loss of periodontal tissue, named false pocket, although when there is a loss of the support tissue and protection of the tooth, the sulcus is called periodontal pockets, which can be of two types: suprabone, when the bottom of the sulcus is coronal to the support alveolar bone, and intrabone, when the bottom is located apically in relation to the adjacent alveolar bone. The pocket depth can vary between regions of the mouth and even between neighbouring teeth (Newman et al., 2004).

The attached gingiva (Figure 1) is the continuation of the free gingiva, that, is firmly attached to the underlying bone, and extends to the mucogingival junction (Carranza, 1983).

Cementum (Figure 1) is a hard tissue with no vascularity (Harvey et al. 1994; Hennet, 1995) that covers the tooth root (Mitchell, 2005), is composed of collagen fibres embedded in an organic matrix, and has in its mineral portion, which is responsible for about 65% of its

Periodontal Disease in Dogs 123

cementum alveolus of neighbour teeth), the fibres of the dental alveolar group, which are the fibres of the alveolar ridge (connecting the alveolar ridge to the cementum, obliquely), the horizontal fires (connect the cementum to the ridge, horizontally), the oblique fibres (connect the cementum to the alveolar bone, has a higher number of ligaments), apical fibres (connecting the bone to the cementum around the apex) and the inter-root fibres (that are

physical features, support, shock absorption caused by the chewing strength and

 sensory, because it is abundantly innervated by sensory nerve fibres that are able to transmit tactile sensations of pressure and pain by the trigeminal pathways (Carranza,

 nutritive, since it has blood vessels that provide nutrients and other substances required by the ligament tissues by the cementocytes and the more superficial osteocytes of

 and homeostasis, because of its ability to absorb and synthesise the intercellular substance of the ligament connective tissue, alveolar bone and cementum (Carranza,

In cases where the complete avulsion of tooth occurs, there is a possibility of reintegration of the tooth to the body (Pieri, 2004) if it returns to the alveolus quickly, since the periodontal ligament has ability to rejoin the cementum (Harvey & Orr, 1990). In these cases the endodontic treatment should be performed since the apical vascularisation of the tooth was

Periodontal disease is a condition that affects the periodontium, therefore the structures that surrounds the teeth, whose role is to protect and provide support to it (De Marco & Gioso, 1997). It is an infectious disease (Mitchell, 2005) that affects more than 80% of dogs (Riggio, 2011), and climbing to about 85% of dogs over four years old (Roman et al., 1995; De Marco & Gioso, 1997). This fact makes it the most prevalent disease in dogs (Harvey & Emily, 1993; Gioso & Carvalho, 2004; Mitchell, 2005). It has been described as a multifactorial infection with aetiological factors such as bacterial plaque, microflora, immune status, the amount of saliva, breed, age, routine of prophylactic cleaning and type of food. However, plaque is the primary aetiological agent, which consists predominantly of gram-positive, aerobic, nonmotile bacteria early in the infection, and anaerobic, gram-negative and motile bacteria in

The disease is caused by the accumulation of bacterial plaque on teeth and gingiva (Harvey & Emily, 1993; Gioso & Carvalho, 2004), by toxic metabolism products of these microorganisms and the host immune response against infection (Mitchell, 2005) that triggers the inflammatory process. Initially this process affects only the gingiva tissue, which characterises the gingivitis that later may worsen and develop into a process of periodontitis

between roots of multirooted teeth) (Wiggs & Lobprise 1997; Roza, 2004).

transmission of occlusal forces to the bone (Figueiredo & Parra, 2002); formation, by osteoblasts, cementoblasts and fibroblasts (Clarke, 2001); reabsorption by osteoclasts, cementoclast and fibroclasts (Clarke, 2001);

The periodontal ligament plays several roles in the tooth, such as:

alveolar bone (Carranza, 1983; Figueiredo & Parra, 2002);

the later stages of infection (Harvey & Emily, 1993; Gioso, 2007).

1983; Figueiredo & Parra, 2002);

1983; Figueiredo & Parra, 2002).

ruptured (Pieri, 2004).

**3. Periodontal disease** 

weight, hydroxyapatite crystals (Lindhe & Karring, 1997). It has as its main functions the insertion of periodontal ligament fibres into the root of the tooth (Harvey & Emily, 1993; Lindhe & Karring, 1997; Roza, 2004), the contribution to the process of repair of the root surface and the maintenance of the periodontal ligament fibres (Picasso, 1987; Lindhe & Karring, 1997).

There are two types of cementum: the first, called primary or acellular cementum, is formed in association with root formation and teeth eruption (Lindhe & Karring, 1997). It occupies the coronal and middle thirds of the tooth root and is constituted mostly of Sharpey's fibres, which are the periodontal ligament collagen fibres that attach at one end to the cementum and at the other to the alveolar bone (Roza, 2004). The other type of cementum is called secondary or cellular cementum, formed after the teeth (Lindhe & Karring, 1997) and usually located in the periapical region. It is secreted by cementocytes or cementoblasts, which are cells that are trapped into the organic matrix of cementum. It does not have vascularization, therefore is nourished from the periodontal ligament. The cells secrete cellular cementum in response to functional demands (Wiggs & Lobprise, 1997). Despite the description of the location of each type of cementum, in some cases they can occur alternately in some areas of the root surface (Lindhe & Karring, 1997).

The alveolar bone (Figure 1) involves the maxilla, incisor bone and jawbone that support the teeth in cavities where they are inserted. These cavities are called alveolus (Picasso, 1987; Harvey & Emily, 1993; Roza, 2004).

Composed of 65% minerals (Wiggs & Lobprise, 1997), this bone has a hard consistency and is very dense and compact, but differs from the root cementum because it has innervation, blood and lymphatic vasculature (Lindhe & Karring, 1997).

The interior of the alveolus is where the cribriform plate is located, which radiographically is known as lamina dura, characterised as a radiopaque line around the alveolus. The fibres of the periodontal ligament that attach to the tooth are connected to this plaque and it is where the vessels pass for ligament irrigation and for the nutrition of the cementum organic matrix (Harvey & Emily, 1993; Roza, 2004)

The alveolar bone can be resorbed or remodelled, according to the stimuli that it may suffer (Harvey & Emily, 1993; Roza, 2004).

The periodontal ligament (Figure 1) is a connective tissue structure that binds the tooth to its alveolus, fixing it (Lindhe & Karring, 1997; Figueiredo & Parra, 2002). It originates from mesenchymal cells of the dental sac (Picasso, 1987; Wiggs & Lobprise, 1997).

The periodontal ligament contains nerves and great vascularity, with vessels emanating from the maxillary artery in the case of the maxilla and from the inferior alveolar artery in the case of the jaw, and other cells. It is located between the root cementum and the cribriform plate. Its height, width, quality and condition are crucial to give the tooth its characteristic mobility (Harvey & Emily, 1993; Lindhe & Karring, 1997; Roza, 2004).

There are three different categories of fibres in the periodontal ligament: the fibres of the gingival grouping, composed by dental gingival fibres (connect the cementum to the gingiva), the alveologingival fibres (connects the cribriform plate to the gingiva), the circular (surrounding the tooth at the free gingiva), the transseptal fibres (connects the supra

weight, hydroxyapatite crystals (Lindhe & Karring, 1997). It has as its main functions the insertion of periodontal ligament fibres into the root of the tooth (Harvey & Emily, 1993; Lindhe & Karring, 1997; Roza, 2004), the contribution to the process of repair of the root surface and the maintenance of the periodontal ligament fibres (Picasso, 1987; Lindhe &

There are two types of cementum: the first, called primary or acellular cementum, is formed in association with root formation and teeth eruption (Lindhe & Karring, 1997). It occupies the coronal and middle thirds of the tooth root and is constituted mostly of Sharpey's fibres, which are the periodontal ligament collagen fibres that attach at one end to the cementum and at the other to the alveolar bone (Roza, 2004). The other type of cementum is called secondary or cellular cementum, formed after the teeth (Lindhe & Karring, 1997) and usually located in the periapical region. It is secreted by cementocytes or cementoblasts, which are cells that are trapped into the organic matrix of cementum. It does not have vascularization, therefore is nourished from the periodontal ligament. The cells secrete cellular cementum in response to functional demands (Wiggs & Lobprise, 1997). Despite the description of the location of each type of cementum, in some cases they can occur

The alveolar bone (Figure 1) involves the maxilla, incisor bone and jawbone that support the teeth in cavities where they are inserted. These cavities are called alveolus (Picasso, 1987;

Composed of 65% minerals (Wiggs & Lobprise, 1997), this bone has a hard consistency and is very dense and compact, but differs from the root cementum because it has innervation,

The interior of the alveolus is where the cribriform plate is located, which radiographically is known as lamina dura, characterised as a radiopaque line around the alveolus. The fibres of the periodontal ligament that attach to the tooth are connected to this plaque and it is where the vessels pass for ligament irrigation and for the nutrition of the cementum organic

The alveolar bone can be resorbed or remodelled, according to the stimuli that it may suffer

The periodontal ligament (Figure 1) is a connective tissue structure that binds the tooth to its alveolus, fixing it (Lindhe & Karring, 1997; Figueiredo & Parra, 2002). It originates from

The periodontal ligament contains nerves and great vascularity, with vessels emanating from the maxillary artery in the case of the maxilla and from the inferior alveolar artery in the case of the jaw, and other cells. It is located between the root cementum and the cribriform plate. Its height, width, quality and condition are crucial to give the tooth its

There are three different categories of fibres in the periodontal ligament: the fibres of the gingival grouping, composed by dental gingival fibres (connect the cementum to the gingiva), the alveologingival fibres (connects the cribriform plate to the gingiva), the circular (surrounding the tooth at the free gingiva), the transseptal fibres (connects the supra

mesenchymal cells of the dental sac (Picasso, 1987; Wiggs & Lobprise, 1997).

characteristic mobility (Harvey & Emily, 1993; Lindhe & Karring, 1997; Roza, 2004).

alternately in some areas of the root surface (Lindhe & Karring, 1997).

blood and lymphatic vasculature (Lindhe & Karring, 1997).

Harvey & Emily, 1993; Roza, 2004).

matrix (Harvey & Emily, 1993; Roza, 2004)

(Harvey & Emily, 1993; Roza, 2004).

Karring, 1997).

cementum alveolus of neighbour teeth), the fibres of the dental alveolar group, which are the fibres of the alveolar ridge (connecting the alveolar ridge to the cementum, obliquely), the horizontal fires (connect the cementum to the ridge, horizontally), the oblique fibres (connect the cementum to the alveolar bone, has a higher number of ligaments), apical fibres (connecting the bone to the cementum around the apex) and the inter-root fibres (that are between roots of multirooted teeth) (Wiggs & Lobprise 1997; Roza, 2004).

The periodontal ligament plays several roles in the tooth, such as:


In cases where the complete avulsion of tooth occurs, there is a possibility of reintegration of the tooth to the body (Pieri, 2004) if it returns to the alveolus quickly, since the periodontal ligament has ability to rejoin the cementum (Harvey & Orr, 1990). In these cases the endodontic treatment should be performed since the apical vascularisation of the tooth was ruptured (Pieri, 2004).
