ASSESSMENT OF THE ORAL CAVITY AND DENTITION

A systematic approach to examination of the oral cavity is required to ensure no abnormalities are missed. Thorough oral assessment involves the use of two major diagnostic tools:

1.

2. Radiographic imaging to help identify and/or confirm abnormalities deep to the gingival margin.

The examination should begin with the superficial facial structures (extraoral assessment) and progress into the oral cavity proper (intraoral assessment) where the animal’s anatomy, occlusion, periodontium, endodontic system and oral soft tissues are examined. Each of the parameters mentioned will be discussed below with respect to the clinical and radiographic appearance and their clinical relevance. Discussion of normal radio­graphic dental anatomy is covered in Fiani (2015).

3.1 Extraoral assessment

The extraoral assessment involves visualisation and pal­pation of the superficial structures of the head. Starting rostrally and moving caudally, the clinician should pal­pate for any evidence of facial asymmetry. This may be caused by soft tissue changes such as localised swelling or muscle atrophy or it may be secondary to abnormalities of the bones, such as osteomyelitis, skeletal malformations or tumours of the jaw (Canfield et al. 1990; Brookins et al. 2008). In cases where maxillofacial trauma is suspected, assessment for jaw instability and crepitus is important (Pettett et al. 2012).

The proximity of the orbit to the oral cavity in many species leads to the possibility of odontogenic disease or oral tumours impinging on the periocular region (Kemp- ster and Hirst 2002). Therefore, assessment of the posi­tion of the globes visually and by retropulsion is pertinent to the extraoral examination.

Familiarity with the location of the superficial lymph nodes of the head is important because enlargement may be suggestive of a neoplastic or inflammatory process either within the oral cavity or in the surrounding tissues (Canfield et al.

3.2 Anatomical and developmental variations and abnormalities

Abnormalities and variations in dental anatomy are common in eutherian species (Verstraete et al. 1996; Pav- lica et al. 2001; Peralta and Fiani 2017) and have been reported in several Australian mammals, including Dasyuridae, Peramelidae, Phalangeridae, Phascolarctidae, Moacropodidae and Pinnipedia (Freedman 1967; Archer 1975; Logan and Sanson 2002b; Loch et al. 2010; Pettett 2016). Archer (1975) provides an extensive review of the variations in tooth number and crown shape, but does not refer to the clinical relevance of these findings. One can extrapolate that, as these anatomical and developmental variations occur across many mammalian species, paral­lels may be drawn with regards to their clinical relevance.

3.2.1 Supernumerary teeth

These are extra teeth that can be present at any location within the dental arches and have been reported in vari­ous marsupials and pinnipeds (Archer 1975; Loch et al. 2010; Drehmer et al. 2015). If the location of the extra tooth results in crowding, this will lead to plaque retention and/or food impaction, predisposing the teeth at that loca­tion to periodontitis. Supernumerary dentition can also lead to occlusal abnormalities (Pettett 2016). If the extra tooth erupts in an unfortunate location or forces sur­rounding dentition to do so, this could result in abnormal tooth-to-tooth wear (attrition) or tooth-to-soft tissue con­tact. In these cases, extraction of the supernumerary tooth may be indicated.

3.2.2 Missing teeth

This is a finding that must be confirmed radiographically. The simple absence of a tooth or teeth in the oral cavity does not exclude an unerupted tooth or retained roots sec­ondary to a tooth fracture. A case of hypodontia in an eastern grey kangaroo (Macropus giganteus) has been reported (Campbell et al. 2008). Some macropod species will have variable numbers of erupted teeth at different life stages because of late eruption of caudal molar teeth and mesial molar progression resulting in shedding of rostral molars as as the animal ages (Kirkpatrick 1964, 1965; Kirk­patrick and Johnson 1969; Vogelnest and Woods 2008).

3.2.3 Retained (unerupted or embedded) teeth

This important diagnosis can only be made radiographi­cally. If there is an obvious physical barrier to tooth erup­tion (e.g. tooth laying sideways) the tooth can be referred

Fig. 13.3. Intraoral radiograph of the right caudal mandible of a normal western grey kangaroo (Macropus fuliginosus). The deciduous 3rd premolar tooth (DP₃) is in functional occlusion and the permanent 3rd premolar tooth (PM₃) has not yet erupted. Note the unerupted 3rd molar tooth (M₃).

to as impacted. In some cases, historical or radiographic findings may suggest trauma during odontogenesis that then led to tooth retention (Fulton et al. 2014; Peralta and Fiani 2017). In most cases, however, the cause of the tooth retention is not known. The most important clinical aspect of retained teeth is the possibility of dentigerous cyst formation around the tooth. These odontogenic cysts result in expansile destruction of the jaw and surround­ing dentition (Verstraete et al. 2011). Unerupted teeth must be extracted and if a cyst has formed, enucleation of the epithelial lining is necessary to prevent further expan­sion.

3.2.4 Persistent deciduous teeth

The deciduous dentition is either absent or vestigial (mini­mally formed and unerupted) in all marsupials thus far examined (van Nievelt and Smith 2005; Smith 2006). The only exception to this is a single functional (erupted) deciduous tooth per quadrant. The tooth is generally thought to be the last premolar, termed deciduous premo­lar 3 (DP₃) (Flower 1867; Smith 2006). Bats, pinnipeds and the dingo (Canisfamiliaris) are also diphyodonts; however, they possess deciduous incisors, canines and some premo­lars (Thomson and Rose 1992; Brunner 1998; Giannini and Simmons 2007; Drehmer et al. 2015). Deciduous teeth are typically smaller and more radiolucent than their per­manent counterparts (Fiani 2015). The term persistent means that the deciduous tooth is erupted but has not been shed despite the animal’s age. Persistent deciduous teeth are associated with similar complications to super­numerary teeth and may be associated with impaction of the permanent tooth. Persistent deciduous teeth must be extracted to prevent the cascade of disease associated with their presence, unless a permanent counterpart is not demonstrated radiographically. In that case, the decidu­ous tooth may serve as a functional alternative.

3.2.5 Abnormalities of the crown

Double teeth - These teeth appear to have two crowns caused by gemination or fusion.

Enamel defects - Dental fluorosis has been reported to affect several herbivorous species, including eastern grey kangaroos and koalas, inhabiting high-fluoride areas (Death et al. 2015; Kierdorf et al. 2016). Excessive intake of fluoride during enamel formation leads to enamel hypoplasia and hypomineralisation (soft enamel). Affected teeth have a rough surface, are often stained brown and are much less resistant to wear. Enamel defects potentiate plaque retention and may predispose to perio­dontal disease. The defects can be seen clinically and radiographically as irregularities in the enamel. Enamel hypoplasia has been reported in other species, caused by distemper virus infection, nutritional factors, toxicosis and trauma during odontogenesis (Deem et al. 2000; Fiani and Arzi 2009). It is noteworthy that Otariids normally have heavy, dark black staining of their teeth that may mimic enamel defects (Barnes et al. 2008).

3.2.6 Abnormalities of the roots

Fused roots of multirooted teeth - These represent a non- pathological anatomical variation. Although not a prob­lem in itself, fused roots may alter the surgical approach in the event that the affected tooth requires extraction for another reason.

Dilacerated roots - These are tooth roots that are abnormally curved. Similar to fused roots, this is consid­ered a non-pathological anatomical variation that is only consequential if the affected tooth requires extraction.

Supernumerary roots - This term describes a tooth with extra roots. The supernumerary root will occasion­ally be positioned in such a location that it distorts the gingival margin, thereby creating a plaque retentive sur­face and predisposing the tooth to periodontitis. Super­numerary roots have been reported in the western quoll (Dasyurus geoffroii) (Archer 1975).

3.3 Occlusal assessment and malocclusion

The term ‘occlusion’ describes several complex relationships:

• the relationships between all four jaws (i.e. the facial skeleton)

• the relationship/interdigitation between maxillary and mandibular dentition

• the location and proximity of teeth within the same jaw relative to one another.

There have been numerous studies describing the normal skull morphometrics of several Australian mam­mals, including various marsupials (wombat, koala, wal­laby, Tasmanian devil and quoll), bats, rodents, pinnipeds and the dingo (Werdelin 1986; Kemper and Schmitt 1992; Nakajima and Townsend 1994; Dumont 2004; Flores et al. 2006; Giannini et al. 2006; Elledge et al. 2008; Saber and Gummow 2014; Drehmer et al. 2015; Pollock et al. 2021). These descriptions help to establish what the ‘normal occlusion’ is for these species.

Any variation from the normal relationships described above would then render that particular animal as maloc- cluded. Broadly speaking, malocclusions can fall into two aetiological groups: dental or skeletal. Dental malocclu­sions occur when a patient has a normal facial skeleton, but there is one or more teeth positioned abnormally within the jaw. Skeletal malocclusions occur when the jaws have abnormal relationships relative to each other, which results in inappropriate interdigitation between the upper and lower teeth as well as abnormal spacing between teeth within the same jaw.

The American Veterinary Dental College divides malocclusions into four classes (AVDC 1988).

• Class 1 Malocclusion: describes all dental malocclusions.

The useful suffix ’verted’, meaning tilted, is often used to further describe the abnormal position of a tooth. For example, a tooth may be buccoverted (tilted towards the cheek) or linguoverted (tilted towards the tongue). Class 1 malocclusions can be the result of supernumerary teeth, persistent deciduous teeth or trauma during odon­togenesis that displaces a dental bud.

• Class 2 Malocclusion: describes symmetrical skeletal malocclusion where the mandibular arch occludes caudal to its normal position relative to the maxillary arch. This is typically thought of as a genetic malocclusion.

• Class 3 Malocclusion: a symmetrical skeletal malocclu­sion where the maxillary arch occludes caudal to its normal position relative to the mandibular arch. This is also thought to be a genetic malocclusion.

• Class 4 Malocclusion: a group of skeletal malocclusions where there is maxillomandibular asymmetry in several directions:

• Rostrocaudal - where one side of the face is rela­tively shorter than the other.

• Side-to-side - where there is a loss of midline align­ment between the maxilla and mandible (Fig. 13.4). Dorsoventral - where there is an abnormal vertical space between the maxilla and mandible when the mouth is closed.

Asymmetrical malocclusions may be genetic in origin or acquired secondary to trauma either during develop­ment (e.g. joey tail sucking or poor hand-rearing tech­niques) or from jaw fracture malunion (McCracken 2008; Fulton et al. 2014).

Malocclusions are only of clinical significance if they result in trauma and/or dysfunction. This can happen if there is abnormal tooth-to-tooth contact leading to abra­sive wear and inability to close the mouth or abnormal tooth-to-soft-tissue contact resulting in trauma and pain. Malocclusions can have lifelong effects on body condition and oral health.

Fig. 13.4. Class 4, side-to-side malocclusion in a koala (Phascolarctos cinereus). Note the left lateral deviation of the mandible and the secondary 'slanted' attrition pattern of the incisor teeth. Photo: Taronga Zoo

Malocclusions have been observed in both free-rang­ing and zoo-housed koala populations with prevalence ranging from 22% to 39% (Pettett et al. 2019). Free-rang­ing koalas were more likely to be affected by Class 1 malocclusions, whereas all four classes have been noted in their zoo-housed counterparts (Pettett 2016). Pettett et al. (2019) observed a variety of skeletal malocclusions in both free-ranging and zoo-housed koalas, and they noted that affected individuals were more likely to develop tooth rotation, mobility and erosion, leading to poor mas­tication and food impaction. There was evidence of familial links to malocclusion types in zoo-housed ani­mals. Breeding recommendations for zoo-housed koalas should consider known koala malocclusion traits to min­imise their effect on future generations. Native rodents have been reported to develop malocclusion following jaw fractures, oral infections, tooth loss or poor nutrition (Breed and Eden 2008). Malocclusions also have been described in wombats (Bryant and Reiss 2008; Fagan and Ullrey 2008; Wilson and Gillett 2010). These animals are unique among Australian marsupials in that they possess solely aradicular hypsodont (elodont) dentition, meaning that their teeth never form an apex and so continue to grow throughout life (Clarke 2003; Fiani 2015). If a wombat does not receive an adequately abrasive diet or has a facial skeletal malformation, overgrowth of the teeth will lead to trauma and dysfunction (Bryant and Reiss 2008; Wilson and Gillett 2010). Skeletal malocclu­sions have been noted to occur in juvenile wombats as a result of one-sided bottle feeding and secondary to vehicular trauma at the time of orphaning (Bryant and Reiss 2008; McCracken 2008). The malocclusions can be seen on oral examination as overly long and deviated crowns with sharp buccal and lingual points caused by inappropriate wear. Although dental radiographs can be used in wombats, their small gape can makes intraoral radiography difficult. CT imaging is ideal for assessing both the dentition and facial skeleton in this species (Fiani 2015).

3.3.1 Treatment of malocclusions

Treatment will largely depend on the underlying cause for the malocclusion. In the case of wombats with teeth that have overgrown and developed sharp points, occlusal adjustment using dental files or burs may be indicated. Care must be taken when performing this procedure to not expose the sensitive pulp. It is impera­tive that instruments such as wire cutters, rongeurs or nail clippers never be used to trim the teeth as these can result in painful vertical tooth fractures. If the underly­ing reason for the malocclusion is not or cannot (skeletal malformation) be corrected, regular re-assessment of these patients is necessary to ensure their overall health and welfare are not compromised.

In cases of anelodont dentition (closed apicies) that have abnormal tooth-to-tooth or tooth-to-soft tissue con­tact several options may be available. These include extraction of the offending tooth, crown height reduction and root canal therapy, or orthodontic movement of the teeth (Fulton et al. 2014). Although the more advanced options have not been reported in Australian mammals, the principles may be directly applicable in certain cases.

3.4 Periodontal disease assessment, diagnosis and treatment

Periodontal disease is a term most commonly used to refer to plaque-induced inflammation and eventual destruction of the periodontum. Plaque biofilm is a com­plex material that begins as primary colonising bacteria suspended in a matrix of salivary glycoproteins that can adhere to the tooth surface (Teughels et al. 2012). The bacterial colonies mature and produce protective extracellular polysaccharides. If left undisturbed, this biofilm allows microcolonies to form complex groups with metabolic advantages and a primitive circulatory system, essentially behaving as a complex organism (Wolf et al. 2005). The presence of subgingival plaque induces inflammation of the gingiva (gingivitis). This inflamma­tion can progress apically and results in eventual destruc­tion of the periodontal structures. When loss of attachment occurs, the disease process is termed perio­dontitis. The most current theory regarding the develop­ment of periodontal disease is referred to as the ecological plaque hypothesis (Wolf et al. 2005; Teughels et al. 2012). It proposes that, rather than the simple presence of viru­lent bacteria, it is the relationship between the host envi­ronment (e.g. immune response, oral pH, environmental stress, periodontal trauma) and the plaque microflora that can lead to periodontal destruction. Several authors have published on the presence of certain bacterial popu­lations in the oral cavities of Australian mammals and their probable role in the induction of periodontitis; how­ever, causality has been difficult to prove (Bird et al. 2002; Mikkelsen et al. 2008; Lee et al. 2011; Borland et al. 2012; Antiabong et al. 2013; Bird et al. 2015).

Occasionally, the term periodontitis may also be used to refer to destruction of the periodontium secondary to other disease processes such as traumatising malocclu­sions (tooth-to-soft tissue contact) or focal inflammation secondary to food impaction (Lee et al. 2011; Pettett et al. 2012; Fulton et al. 2014; Pettett 2016). Macropod progres­sive periodontal disease or ‘lumpy jaw’ is discussed in Chapter 31.

Periodontal disease is often first noted during oral examination. Advanced disease should be suspected in cases of weight loss, reduced appetite, dropping of food, ptyalism, halitosis or facial swelling. Diagnosis of perio­dontal disease requires both a careful oral examination and radiographic imaging.

3.4.1 Oral examination and periodontal probing

A superficial oral examination will allow the clinician to assess the overall health of the oral cavity, but offers little information on the presence and degree of periodontal disease. It is important to note that periodontal disease is a tooth-by-tooth diagnosis, meaning that each tooth must be assessed individually, because different teeth within the same mouth may be affected by vastly different stages of periodontitis. Periodontal probing and charting is con­sidered an essential component of a comprehensive oral examination. A periodontal probe (Fig. 13.4) is used to measure several parameters that allow the assessment of the presence and extent of periodontitis.

1. Mobility: The elbow of the periodontal probe is used to apply gentle pressure to the crown of each tooth. A tooth requires at least 50% attachment loss before mobility is noted. It is also important to remember that teeth may become mobile from other causes such as root fracture, root resorption (as seen with rostral molar teeth in macropods because of molar progression) or neoplasia of the jaw.

2. Periodontal probing depth: Abnormal periodontal probing depth correlates accurately with the degree of attachment loss (Carranza and Camargo 2006). It is one of the most important parameters in assessing periodontitis. The periodontal probe, which is simply a modified ruler, is placed into the gingival sulcus of each tooth and walked around the circumference measuring the distance from the CEJ to the bottom of the sulcus. The reason that the measurement is obtained from the CEJ rather than the gingival margin is because the gingiva may change in size or location whereas the CEJ is a stable point. For example, if a patient has an area of gingival recession and a periodontal probe is used to measure from the gingival margin to the bottom of the sulcus, the probing depth would not reflect the true clinical attachment loss. However, when the measurement is obtained from the CEJ to the bottom of the sulcus, regardless of the location of the recessed gingiva, that would provide a much more accurate measurement of clinical attachment loss. The exception to this rule would be the canine teeth of the Tasmanian devil, which only have enamel covering the coronal two-thirds of the crowns (Fiani 2015). Pettett et al. (2012) found that the normal probing depth in the koala ranged from 0.5-1 mm. Normal probing depth for different species is likely to vary. No studies specifically measuring the normal probing depths in other Australian mammals are available. A probing depth of 0-3 mm is likely to be acceptable for most species until further research into normal probing depths for Australian mammal species has been undertaken.

3. Gingivitis: On probing of a normal gingival sulcus, the gingiva should be light pink in colour with a sharp margin and there should be no bleeding during periodontal probing. Inflammation and bleeding on probing are indicative of gingivitis; the earliest sign of periodontal disease. A gingival index

Fig. 13.5. Periodontal probe (P) and explorer (E). The markings on this periodontal probe are in 1-mm increments.

can be used to help assess the severity of the inflammation:

• Stage 1 gingivitis: mild inflammation and oedema, but no bleeding on probing

• Stage 2 gingivitis: moderate inflammation, swelling and bleeding on probing

• Stage 3 gingivitis: severe inflammation, ulceration and spontaneous haemorrhage.

4. Furcation involvement: When multirooted teeth are assessed, the periodontal probe is turned sideways and used to explore the furcation area where the roots meet. Loss of alveolar bone between the roots is problematic because it is a highly plaque retentive surface. A furcation index is used to help define the severity of periodontitis at this anatomical location:

• Stage 1 furcation: periodontal probe extends less than halfway under the crown

• Stage 2 furcation: periodontal probe extends more than halfway under the crown

• Stage 3 furcation: periodontal probe extends all the way under the crown and exits on the other side of the tooth. This is also referred to as furcation exposure or through-and-through furcation.

3.4.2 Dental radiographs

Dental radiogrpahs are essential in determining the degree of alveolar bone loss, the presence of furcational defects and periodontal-endodontic lesions.

1. Alveolar bone loss (Fig. 13.6): The alveolar margin should reach to within 1-2 mm of the CEJ. In general, alveolar bone loss can follow a vertical or horizontal pattern (Peralta and Fiani 2017). Vertical bone loss is when the defect is perpendicular to the CEJ. Horizontal bone loss is when the defect is parallel to the CEJ. A combined pattern can also occur. The pattern of bone loss is clinically relevant because it can affect therapeutic options (Newman et al. 2006). The amount of radiographic alveolar bone loss is usually consistent with the severity of the periodontitis. It is useful for the clinician to think of alveolar bone loss in terms of percentage root coverage: when the alveolar bone height is normal, that would be 100%; if half of the alveolar bone height is lost, that would be 50%. Less than 25% alveolar bone loss is considered mild

Fig. 13.6. Red-necked wallaby (Notamacropusrufogriseus) intraoral dental radiographs of the caudal mandibles. (a) Right caudal mandibular view showing complete dentition with minimal evidence of periodontal disease. (b) Left caudal mandibular view showing the absence of the 3rd premolar (PM₃) and 1st molar (M₁) teeth. There is severe horizontal bone loss (>50%) with furcation exposure at the 2nd molar tooth (M2). The solid white line denotes the cementoenamel junction. The tooth is also affected by a periodontal-endodontic lesion at the mesial (rostral) root. The dotted line outlines the periapical lucency. The apex of the mesial root is also affected by inflammatory root resorption, seen as a relatively shorter root with an irregular apex. The 3rd molar tooth (M₃) is affected by moderate (25-50%) vertical bone loss at the mesial root. The tooth also has furcation involvement (arrowhead) and root external surface resorption (arrow).

Fig. 13.7. Graphic demonstrating the process of periodontal- endodontic disease. The black arrow shows the progress of periodontitis down the length of one root, ultimately reaching the apex and resulting in a retrograde infection of the pulp. The other root has developed periapical disease secondary to the infected pulp system. (Graphic provided by Cornell University College of Veterinary Medicine, Dentistry and Oral Surgery Section.)

periodontitis, 25-50% is moderate and >50% is severe periodontitis. Teeth affected by severe periodontitis will usually require extraction.

2. Furcational defects (Fig. 13.7): Furcation involvement is the term used to describe incomplete bone loss at the furcation. In contrast, furcation exposure refers to complete loss of alveolar bone between the roots. If furcation exposure is detected, the long-term periodontal prognosis is poor because this is an extremely plaque retentive surface that cannot be adequately maintained. Extraction of teeth with furcation exposure is indicated, regardless of the severity of attachment loss.

3. Periodontal-endodontic lesions (Figs 13.6 and 13.7): If periodontitis is severe enough that it reaches the apex of a tooth, bacteria will enter the pulp cavity at the apex and kill the tooth. This will lead to endodontic disease (see below). Severe alveolar bone loss (>50%) and periapical lucency are characteristic radiographic findings. The prognosis for periodontal-endodontic lesions is poor.

3.4.3 Periodontal treatment

Periodontal treatment typically involves supra- and subgin­gival ultrasonic scaling to remove calculus (calcified plaque) and to disrupt the plaque biofilm. Dental extractions (see below for details) are indicated if there is periodontal- endodontic disease present and/or if there is >50% perio­dontal attachment loss and/or if there is furcation exposure. In certain cases, if the cause of the periodontitis is second­ary to occlusal trauma or food impaction, the elimination of the underlying cause may prevent further damage and allow retention of the affected tooth (Perry et al. 2014).

More advanced periodontal procedures may be possi­ble; however, their indication is heavily dependent on the extent and pattern of the periodontitis (Perry et al. 2014; Kao et al. 2015; Takei et al. 2015). Success not only relies on the clinician’s experience but also on the ability to provide oral hygiene and follow-up assessment in the future. Consultation with a veterinary dentist following the collection of the previously described diagnostics should be considered for teeth that are only mildly to moderately affected by periodontitis.

3.5 Endodontic disease assessment, diagnosis and treatment

Endodontics is the branch of dentistry that pertains to disease of the pulp and periapical tissues. Pulp trauma may result in inflammation, swelling and haemorrhage, leading to secondary necrosis. The necrotic tissue is pre­disposed to infection, which in turn results in the release of inflammatory mediators and, in some cases, bacteria through the apex of the tooth. Soon, periapical periodon­titis ensues and eventually progresses to the formation of a periapical granuloma or a periapical abscess. This stage of the disease is painful. There are several ways that teeth can become endodontically diseased.

1. Tooth fracture leading to pulp exposure (complicated tooth fracture) (Fig. 13.8): Pulp exposure has been reported in both free-ranging and managed Australian mammals, including Dasyuridae, Phascolartidae and Phalangeroidea (Jones et al. 2001; Jones and Rose 2001; Clarke 2003; Pettett 2016; Pollock et al. 2021).

2. Rapid abrasion: If teeth are worn faster than the odontoblasts can form tertiary (reparative) dentin, pulp will become exposed (Emily 1998).

3. Loss of blood supply to a tooth: This can occur following mild trauma that results in concussive damage to the pulp or from more extensive trauma that leads to tooth luxation, avulsion or even jaw fracture through the alveolus of a tooth. Animals that have undergone major trauma, such as being hit by a car, should be assessed carefully for endodontic disease.

Fig. 13.8. Complicated crown root fractures of the left maxillary 3rd premolar (PM³) and 2nd molar (M²) teeth in a Tasmanian devil (Sacrophilusharrissii). Note the exposed pulp and the extension of the fracture line below the gingival margin (arrow). Photo: Taronga Zoo

4. Periodontal-endodontic lesion: Severe periodontitis can result in retrograde infection of the pulp.

5. Deep caries: These are lesions that form when acidic bacterial byproduct degrades mineralised dental tissues and eventually result in pulpitis. Although these lesions have been sporadically mentioned in association with Australian mammals, the reports are not conclusive (Clarke 2003; Pettett 2016).

3.5.1 Oral examination

Patients with endodontic disease may present with facial swelling or a draining tract associated with the region of the affected tooth. Often, however, endodontic disease is noted incidentally on oral examination. During perio­dontal charting the clinician should carefully examine each tooth for fracture or severe abrasion. A dental explorer (Fig. 13.5) should be used to detect the presence of pulp exposure. The teeth should also be assessed for intrinsic discoloration, which can occur following con- cussive trauma (Hale 2001). Finally, mobility or displace­ment of a tooth may be present secondary to more extensive dentoalveolar trauma.

3.5.2 Dental radiographs

There are four common radiographic signs associated with endodontically diseased teeth (Fig. 13.9) (Peralta and Fiani 2017). All the signs may not be present at once because chronicity plays a role in the progression of the radiographic changes:

1. Loss of crown integrity: Tooth fractures are visible radiographically. It is not always easy to discern on radiographs if pulp exposure has occurred and so this finding must be combined with an oral examination. Retained roots are the ultimate example of ‘loss of crown integrity’ and are considered to be endodontically diseased teeth.

Fig. 13.9. Intraoral radiographs from a Tasmanian devil (Sarcophilusharrisii) (a and b). (a) Left lateral maxillary canine view showing loss of crown integrity (arrow) and failure of the pulp cavity to narrow (denoted by longer white line) when compared with the contralateral tooth in (b). Arrowheads show inflammatory root resorption (compare with the apex of the left maxillary canine tooth in (b)) and the dotted line outlines an ill-defined periapical lucency. (b) Right lateral maxillary canine view showing loss of crown integrity of the canine and 1st molar teeth (arrows). No other radiographic signs of endodontic disease are present. (c) Intraoral occlusal view of the rostral mandible of a koala (Phascolarctos cinereus). The right mandibular incisor is non-vital. When compared with the normal left mandibular incisor, the non-vital tooth has loss of crown integrity (shorter crown), failure of pulp cavity to narrow (denoted by the longer white line), well-defined periapical lucency (dotted line) and significant inflammatory root resorption (shorter root). Images: Taronga Zoo

2. Failure of the pulp cavity to narrow: When compared with the contralateral, opposing or adjacent teeth, the affected tooth will have a wider pulp cavity. This occurs because both the pulp and odontoblasts (see pulp-dentin complex in section 1) die and therefore no new dentin is produced. A lack of discrepancy in pulp cavity width does not rule out endodontic disease, especially in cases of endodontic disease of relatively short duration (a few days or weeks) (Peralta and Fiani 2017).

3. Periapical lucency: Inflammation of the periapical tissues is detectable radiographically once lysis of the associated bone has occurred. Typically, the lesion appears as an ill- or well-defined, round area of lucency encompassing the apical portion of the root(s).

4. Inflammatory root resorption: Persistent periapical inflammation leads to resorption of the apical aspect of the tooth. Radiographically this appears as a blunted apex or a relatively shorter root.

3.5.3 Endodontic treatment

Once a tooth is confirmed as endodontically diseased, treatment must be administered as soon as possible. Treat­ment options will depend on the aetiology and severity of the disease affecting the tooth.

Tooth fracture: Describing the fracture is a two-step process. The first is identifying any pulp exposure. If the pulp is exposed the fracture is referred to as complicated. If the pulp is not exposed, the fracture is uncomplicated. The second step is to identify the anatomy of the tooth involved in the fracture line. If only enamel and dentin are involved, the fracture is then limited to the crown. If the fracture involves enamel, dentin and cementum, it is known as a crown-root fracture. Finally, if the fracture only involves cementum and dentin, it is known as a root fracture. By combining the two steps, a clinician can then accurately describe a tooth fracture (e.g. complicated crown fracture or uncomplicated crown-root fracture etc). Treatment options for fractured teeth are outlined in Table 13.2.

Severe abrasion (wear) with pulp exposure: Teeth that are not behaviourally or functionally important or have minimal crown structure remaining are best extracted. However, if the teeth are strategic or poten­tially very difficult to extract, root canal therapy may be considered. Regardless of the treatment option chosen, addressing the reason for the severe abrasion (e.g. maloc­clusion) is important.

Loss of blood supply: Concussion - acutely concussed teeth may appear pink in colour if pulp haemorrhage has occurred. With time this discoloration will turn to a dark-brown or grey. However, not all concussed teeth become discoloured. It is possible that a clinically normal tooth may be found to be non-vital based on radiographic findings (see above). Unfortunately, there is no reliable method of diagnosing endodontic disease in acutely trau­matised teeth that are not discoloured because radio­graphic changes take time (usually months) to become evident. Obviously concussed and non-vital teeth should either undergo root canal treatment or extraction.

Luxation - This occurs when teeth are partially dis­placed within their alveoli, resulting in avulsion of the blood vessels at the apical delta. This type of trauma often results in alveolar bone fracture. Treatment of these teeth requires stabilisation of the tooth with a dental splint for several weeks. The affected tooth will also require a root canal treatment, typically performed at the time of splint removal for practical reasons. The alternative to this is extraction.

Avulsion - This occurs when a tooth has either com­pletely or almost completely (held in by a small amount of soft tissue) been displaced from its alveolus. For practical reasons, it is best to extract these teeth.

Teeth in fracture lines - Management of teeth in frac­ture lines is a large and complex topic that falls beyond the scope of this text. Suffice to say that repair of the jaw fracture while ignoring the endodontic consequences of the traumatised teeth will affect fracture healing.

3.6 Other findings

Tooth wear (abrasion): Dental wear is a common finding in herbivorous marsupials because of the abrasive nature of their diet. Masticatory efficiency is affected by tooth wear, which in turn influences the nutritional status of the affected individual (Lanyon and Sanson 1986; McAr­thur and Sanson 1988). Age-related increase in dental wear in free-ranging koalas is associated with an increase in the average amount of time spent feeding and the amount of food consumed, as well as a reduction in movement and social interaction (Logan and Sanson 2002a, Logan and Sanson 2002b). Similar findings were noted in eastern and western grey kangaroos (M. fuligino­sus) (McArthur and Sanson 1988). Some kangaroos, how­ever, have the distinct advantage of mesial molar progression allowing for replacement of worn teeth with new, sharp teeth. A study by Pollock et al. (2021) highlighted differences in the rate and nature of tooth wear between free-ranging and managed Tasmanian devils, with the former having more severe wear than the latter of the same estimated age. This correlated with the difference in the way teeth are being used and/or the type of food being consumed. Tooth wear is relevant from a nutritional standpoint, but should also prompt the clini­cian to assess the patient for pulp exposure.

Tooth resorption: This is the process by which odonto- clastic activity results in the breakdown of tooth struc­ture. Tooth resorption may be physiological, as seen during the normal exfoliation of deciduous teeth or in the case of molar progression in some macropods (Fig. 13.10) (Peralta et al. 2010b; Fiani 2015). However, it may also be pathological in nature, as seen with the inflammatory root resorption encountered in endodontic and periodon­tal disease (Fig. 13.9). Tooth resorption often affects the roots and is largely diagnosed on intraoral radiographs. Seven types of tooth resorption have been reported in the dog (Peralta et al. 2010a; Peralta et al. 2010b); however, no similar descriptions exist for Australian mammals.

3.8 Dental extractions

3.8.1 List of indications for tooth extraction and alternative treatments if available

• Unerupted teeth

• Supernumerary teeth that are causing crowding or occlusal trauma

• Persistent deciduous tooth with an erupted permanent counterpart

Table 13.2. Treatment options for fractured teeth

• Malocclusion where there is abnormal tooth-to-tooth contact or tooth-to-soft tissue contact. If the patient is a wombat, occlusal adjustment rather than extraction may be indicated

• Periodontitis where there is 50% or more attachment loss (noted on periodontal probing and radiographs)

• Furcation exposure

• Periodontal-endodontic lesion

• Complicated tooth fracture - endodontic treatment in the form of root canal therapy may be an option in certain cases

• Crown-root fracture -where a tooth fracture extends below the gingival margin

• Root fracture (retained root)

• Luxated or avulsed teeth - it may be possible to reposi­tion these teeth with a dental splint, but endodontic therapy will also be needed

3.8.2 Regional anaesthesia

Regional anaesthesia has long been an important com­ponent of dental extractions in veterinary dentistry. It helps reduce the required plane of general anaesthesia intraoperatively and provides analgesia postoperatively. A crucial component of performing regional anaesthesia is a thorough understanding of the neuroanatomy of the dentition in the specific species to be treated. The sen­sory innervation to the oral cavity and the intraoral structures is provided by the maxillary and mandibular divisions of the trigeminal nerve (cranial nerve V). The exact path that the nerve traverses and the location at which the local anaesthetic is to be placed to block sensa­tion to the teeth and periodontium have been studied and verified in the dog, cat and horse (Henry et al. 2014; Campoy et al. 2015; Hermans et al. 2017). No similar neuroanatomical studies or descriptions are available for Australian mammals. Equally important is the lack of pharmacological studies looking at the efficacy and dose of the various local anaesthetic drugs. Further research to map and test innervation to the dentition of Austral­ian mammals is necessary.

3.8.3 Extraction techniques

No specific or novel extraction techniques have been developed for Australian mammals. Rather, a combina­tion of well-described exodontic methods used in domes­tic species have been adapted to the various native mammals. Carnivorous and insectivorous species often have relatively simple radicular anatomy and large oral

Fig. 13.10. Intraoral radiograph of the right caudal mandible of an aged eastern grey kangaroo (Macropus giganteus). All teeth have erupted and molar progression is advanced, with loss of the 3rd premolar and 1st molar teeth and and root resorption and advanced wear evident in the remaining molars (M2, M₃ and M4).

openings. Standard simple or surgical extraction tech­niques used in dogs and cats work well for them (Lommer et al. 2015). Herbivorous species, however, can have more complex radicular anatomy as well as a small gape. The use of extraction techniques described in rabbits and horses, including extraoral extractions, commisurotomies or buccotomies to improve access, are helpful (Gaughan 1998; Tremaine 2004; Dixon et al. 2005; Capello 2007; Wilson and Gillett 2010; Bohmer 2015; Capello 2016).

3.8.4 Postoperative analgesia

Analgesia following any tooth extraction is always indi­cated. Regardless of the difficulty of the extractions, the manipulation of the highly innervated gingiva and perio­dontal ligament will result in discomfort for the patient (Pasco 2015). Multimodal analgesia is often used in domes­tic species. This usually includes a combination of regional anaesthesia, NSAIDs as well as opiates or their derivatives (see Appendix 4). The duration of analgesia may vary with the extent of the extractions. A minimum of 2-3 d of post­operative analgesia for minor extractions and 5-7 d for more extensive extractions is recommended.

3.9 Guidelines for antimicrobial use in the dental patient

3.9.1 Intraoperative antibiotics

Dentistry procedures, including scaling and extractions, can result in intraoperative bacteraemia (Harari et al. 1993; Nieves et al. 1997). The concern is that the bacteria will cause metastatic infection (septicaemia, endocardi­tis etc.). However, healthy animals are able to overcome the bacteraemia without the use of antibiotics. Intraop­erative antibiotics are therefore only indicated in patients that are immunocompromised (which in wild­life may be precipitated by stress of capture, handling or hospitalisation) or have a region or organ that is vascu- larly compromised (AVDC 2005). Some common indi­cations for intraoperative antibiotics in small animal patients include: diabetes, hyperadrenocorticism, surgi­cal implants and severe organ disease. If the patient has already been on antibiotics for several days, intraopera­tive antibiotics should be used. The concern is that there has been a pre-surgical selection for more resistant bac­teria. Intraoperative antibiotics are not commonly indi­cated during periodontal treatment and dental extractions (Peddle et al. 2009).

3.9.2 Postoperative antibiotics

The intention for postoperative antibiotics is to prevent, or in some cases control, infection at the oral surgery site. The oral cavity has an enormous blood supply and so extraction sites heal quickly. This is especially true if the tooth causing the infection (endodontic or periodontal) has been successfuly extracted. The decision to use post­operative antibiotics will depend on the individual case and the clincian’s judgment. Refer to Chapter 31 for spe­cific treatment recommendations of macropod progres­sive periodontal disease (‘lumpy jaw’).