Veterinary Dentistry for the General Practitioner VetCPD 2023 PDF

Dentistry for the General Practitioner VetCPD 2023 Rachel Perry BSc, BVM&S, MANZCVS (Small Animal Dentistry & Oral Surgery), PG Cert (VetEd), FHEA, Dipl.EVDC, MRCVS EBVS ® European Veterinary Specialist, Veter...

Dentistry for the General Practitioner VetCPD 2023 Rachel Perry BSc, BVM&S, MANZCVS (Small Animal Dentistry & Oral Surgery), PG Cert (VetEd), FHEA, Dipl.EVDC, MRCVS EBVS ® European Veterinary Specialist, Veterinary Dentistry RCVS Specialist, Veterinary Dentistry perryreferrals.co.uk [email protected] 1. ANATOMY, OCCLUSION and CHARTING Learning Outcomes By the end of this module you should be better able to: Use correct nomenclature when describing teeth and oral structures Discuss the clinical application of the anatomy of teeth and supporting structures Perform a detailed oral examination and document findings on a detailed dental chart. The general practitioner vet can play a significant role in the oral and dental health of dogs and cats. Very few other disciplines can provide such immediate and substantial improvements to the quality of life of their patients. This course will cover the common dental diseases seen in practice throughout the life of the pet. It will give practical advice on examining the oral and dental structures efficiently, producing a comprehensive dental chart, performing dental radiography and the interpretation of dental radiographs, and also performing periodontal hygiene procedures (scaling, polishing, sub-gingival débridement). ©Rachel Perry 2023 Periodontal disease and homecare options will also be discussed in detail. We will also cover extraction techniques and the challenges of anaesthesia, including regional anaesthesia (nerve blocks). Dental disease is common in pets and if we perform a thorough examination (including dental radiography) it is sometimes surprising just how much clinically relevant pathology we can detect. By learning the knowledge and skills with which to treat these problems, we can feel much happier about searching for them in the first place. If however, we are not confident in feline extractions or dealing with resorption appropriately, it is perhaps easier to perform a cursory examination looking for the gross (but neglecting the subtle) problems. Dentistry is a beautifully visual subject and by appreciating local/ regional anatomy and learning some simple principles, it becomes much easier to identify disease processes with confidence. Dental Terminology In order to accurately describe pathology in the mouth there is some dental specific terminology, which should be understood and used. A good resource is the American Veterinary Dental College website: https://avdc.org/avdc-nomenclature/ Palatal surface of tooth towards palate (maxillary teeth) Lingual surface of tooth towards tongue (mandibular teeth) Labial surface of tooth towards lip Buccal surface of tooth towards cheek Facial can be labial or buccal surface Occlusal surface facing tooth in opposite jaw Interproximal surface between two adjacent teeth Mesial towards mid-line along the dental arch Distal away from mid-line along the dental arch Apical towards the root tip Coronal towards the crown Rostral towards the tip of the nose Caudal towards the tail ©Rachel Perry 2023 Supragingival coronal to the gingival margin Subgingival apical to the gingival margin Periodontal Pertaining to the supporting structures of the tooth (gingiva, alveolar bone, periodontal ligament, cementum) Endodontic Pertaining to the pulp of the tooth Orthodontic Pertaining to the malposition of teeth or jaws Teeth Incisors 6 maxillary (101-103, 201-203) 6 mandibular (301-303, 401-403) Grooming (flea comb) and nibbling Canines 1 in each quadrant (104,204, 304, 404) Offence, defence, killing, communication, holding, mating Premolars Dog 4 maxillary (105-108, 205-208) and 4 mandibular (305-308, 405-408) Cat 3 maxillary (P2, P3, P4; 106-108, 206-208) and 2 mandibular (P3 & P4; 307,308, 407, 408). The tooth immediately distal to the maxillary canine is the 2nd pre-molar and that immediately distal to the mandibular canine is the 3rd pre-molar. Used for chopping/cutting food into smaller pieces, holding objects ©Rachel Perry 2023 Molars Dog 2 maxillary (109,110, 209,210) and 3 mandibular (309-311, 409-411) grinding Cat 1 in each quadrant (109, 209, 309, 409)- cutting only. The maxillary molar is small and easily missed during the oral examination. Carnassials In the dog and the cat, the carnassials are the large caudal chewing teeth: the maxillary 4th premolar (108 & 208) and the mandibular 1st molar (309 & 409). Tooth identification A tooth can either be identified by description: Right/left; maxillary/mandibular; 1st/2nd/3rd/4th; incisor/ canine/ premolar/ molar, e.g. right maxillary 4th premolar Alternatively, the Modified Triadan system (a numbering system adapted from human dentistry) may be used: Each tooth is denoted by a three-digit number The first digit identifies the quadrant location, and whether the tooth is deciduous or permanent. o 1à4: Right maxillary, left maxillary, left mandibular, right mandibular (permanent) o 5à8: Right maxillary, left maxillary, left mandibular, right mandibular (deciduous) o The second two digits identify the tooth, starting with the 1st incisor and counting distally. The canine is always 04 (e.g. 104, 204, 304, 404) The first molar is always 09 (e.g. 109, 209, 309, 409) ©Rachel Perry 2023 The cat has a reduced dentition and this is reflected in its numbering. In the mandible, the first and second premolars are missing, and thus there is no 305 or 306 (or 405,406). In the maxilla, the 1st premolar is missing, thus there is no 105 or 205. Modified Triadan system- cat ©Rachel Perry 2023  Modified Triadan system- dog ©Rachel Perry 2023 Deciduous teeth There are no deciduous molars, or premolar 1 in the dog. Deciduous teeth are identified by their shape- the crowns are small and delicate and the roots very long and slender. As a rule of thumb, there should not be two teeth of the same location at the same time. I.e. there should either be a deciduous or a permanent tooth. The exception is the canine where there may be a short period of crossover time when both are present. Dental radiograph showing deciduous right mandibular 3rd and 4th premolars (green stars) and permanent pre-molars erupting beneath (red stars). The permanent 1st molar has already erupted (red star) [No deciduous molars] ©Rachel Perry 2023 Tooth structure Enamel This is the hardest tissue in the body and consists of 96% inorganic hydroxyapatite crystals. The crystals are laid down by ameloblasts during a finite period of time in the bell stage of tooth formation, becoming mineralized and growing in size. Any disruption to this will result in the clinically obvious enamel hypoplasia (enamel thinner than normal or absent) or hypocalcification (poorly mineralized enamel). Affected teeth may potentially wear faster than normal, may be sensitive and allow bacterial entry into the porous dentine beneath. Once formed, enamel cannot be repaired or replaced, and is therefore subject to attrition (wear due to contact with another tooth) and abrasion (wear due to contact with an external object, such as a cage bar, stones, tennis balls, antlers, bones etc.). Enamel is much thinner in the dog and cat compared to man. (1mm vs. 2.5mm+). 12m MN GSD with severe abrasion of left mandibular canine tooth due to obsessive football chewing. The enamel covering the crown is seen, the inner dentine and an exposed pulp. The discoloured ring around the pulp shows evidence of tertiary dentine. The pulp was necrotic and tooth required treatment. Dentine Dentine is the hard substance making up the bulk of the tooth. It is covered by either enamel (in the crown) or cementum (in the root). It consists of 70% inorganic hydroxyapatite crystals. It appears solid, but actually consists of thousands of microscopic dentinal tubules extending from the dentino-enamel junction to the pulp (40-70 000/mm2). Within the tubules are cytoplasmic extensions from odontoblast cells lining the pulp space, fluid and nerve fibre endings. This means dentine is a sensitive structure. It also means once exposed, bacteria can potentially invade the dentine and therefore the pulp. As the dentine ©Rachel Perry 2023 is intimately associated with the pulp, it is known as the pulp-dentine complex. Various types of dentine exist. Primary dentine forms before eruption of the tooth. Secondary dentine forms continually after tooth eruption as long as the pulp remains vital. The odontoblast, which is at the outer periphery of the pulp space, is the cell responsible for dentine production. A young animal therefore has thin dentinal walls and a wide pulp space, which is a very delicate tooth. Care must be exercised when extracting persistent deciduous teeth not to damage the permanent, fragile tooth next to it. An old animal conversely has thick dentinal walls and a small pulp space. The apex is not fully formed immediately as the tooth erupts. Apexogenesis (physiological formation of the root apex) typically occurs at 8-9 months of age in the dog. In the cat, the mandibular 1st molar apices close at 7 months of age, and the canine at 11 months of age. If the pulp becomes necrotic (e.g. after dentinal fracture and pulp exposure) then secondary dentine production becomes arrested. Dental radiographs may therefore demonstrate a wider pulp space compared to the contralateral tooth. Tertiary dentine is formed as an attempt at tooth repair. If odontoblasts are traumatised (e.g. by attrition or abrasion exposing dentine) they are stimulated to produce more dentine. This tertiary dentine may be laid down rapidly and haphazardly and therefore stains easily. This causes the brown staining seen on many worn teeth. This must be differentiated from an exposed pulp (e.g. due to a fractured tooth). Using a sharp dental explorer probe in the anaesthetised patient will allow you to determine if pulp exposure has occurred. Here, you will feel the probe ‘drop’ into the pulp space. With tertiary dentine it will feel smooth like glass. If the trauma is rapid, the tertiary dentine will not have a chance to form, meaning the pulp may become exposed and therefore infected. ©Rachel Perry 2023  Tertiary dentine in the mandibular canines and incisors of a 12yr FN Labrador. The pulps were not exposed, dental radiography was normal and therefore treatment not required. Pulp In the crown the pulp space is known as the pulp chamber, and in the root the pulp space is known as the root canal. The pulp contains blood vessels, lymphatic vessels, nerves, fibroblasts, collagen fibres, undifferentiated mesenchymal cells and odontoblasts. The only nerve fibres within the pulp are nociceptors: i.e. they ONLY transmit PAIN signals. If you have ever experienced a sensitive tooth when eating ice cream or drinking a hot drink, the sensation is pain whether the stimulus is hot or cold. These are of the Aδ (myelinated fast conduction, sharp pain) or C type (unmyelinated, slow conduction, dull throbbing pain). Pulp extirpation from a canine tooth during root canal therapy Cementum Cementum is the hard, bone-like substance covering the root surface. It is roughly 45-50% inorganic. As it is less mineralised than enamel or dentine it is not readily visualised on radiographs. Sharpey’s fibres embedded within the cementum attach the tooth to the alveolus (socket). Cementum is vital and can repair itself if injured. Periodontal ligament This ligament attaches the tooth to the alveolus, and provides shock-absorption and micro-movement during chewing. It contains many collagen and elastic fibres ©Rachel Perry 2023 oriented in various arrangements to withstand masticatory forces. There are also blood vessels, nerves (proprioception, pain, pressure fibres), connective tissue cells and undifferentiated mesenchymal cells. This space is only about 0.25mm wide. To effectively disrupt these fibres during extraction, instruments must be carefully placed into the space to either cut or tear the fibres. Radiographically, this space appears black, and should be visible all the way round the root. Question: In order to extract a tooth from its alveolus (socket), how may we disrupt the periodontal ligament fibres? Alveolar bone The alveolar bone of the jaws forms the alveoli (tooth sockets), which support the teeth. The alveolus consists of three layers. The compact bone lining the socket is known as the cribriform plate. Radiographically, this appears denser than the surrounding bone and is known as the lamina dura. At the top of the socket the cribriform plate meets the cortical bone at the alveolar margin. The cortical bone is covered with periosteum and in between is spongy, cancellous bone. The periosteal covering is an important layer to understand; especially during an open/surgical extraction technique- a mucogingivoperiosteal flap is created as the periosteum is raised off the underlying bone using a periosteal elevator. Gingiva The oral soft tissues consist of the gingiva and oral mucosa, which are confluent with one another and demarcated at the mucogingival junction (MGJ). The gingiva comprises of: Attached gingiva, which is firmly attached to underlying alveolar bone. Free gingiva, which is not attached to underlying bone- the edge forms the gingival margin (most coronal part) and the tissue reflects back on itself forming the gingival sulcus, which is a potential space between the tooth and the attachment of the soft ©Rachel Perry 2023  tissue to the tooth. At the bottom of the sulcus, the gingiva attaches to the tooth surface via the junctional epithelium. This epithelial attachment to the tooth is a critical area in the pathogenesis of periodontal disease. This is the only area in body where the epithelial surface is broached (by a tooth), and thus is very susceptible to bacterial invasion. During the pathogenesis of periodontitis, the attachment migrates apically with loss of periodontal ligament and alveolar bone. The depth of the gingival sulcus can be measured by gently inserting a periodontal probe along the long axis of the tooth, until the attachment depth is palpated, and then measuring where the gingival margin is situated. This should be performed around the entire circumference of the tooth. Do not miss the palatal/lingual aspects of teeth. Deeper probing may denote attachment loss. Normal gingival sulcus depths are: Cat