Oral cavity

Congenital anomalies

• Facial clefts: may involve the skin only, or the deeper tissues as well, located variously.

• Primary cleft palate(harelip, cheiloschisis):

• Developmental anomalies of the lips rostral to the nasal septum, columella, and premaxilla.

• Unilateral or bilateral

• incomplete fusion of the frontonasal process with the maxillary processes

Secondary cleft palate (cleft palate, palatoschisis)

• Inadequate growth of the palatine shelves leaves a central defect,

• In either or both of the hard and soft palates, which communicates between the oral and nasal cavities

• Common in calves, foals, not in sheep

• Aspiration Penumonia

• Maternal ingestion of certain drugs, or consumption of teratogenic plants during pregnancy e.g. lupines (teratogen ammodendrine), tobacco, hemlok due to presece of Piperidine alkaloids (coniine, coniceine, and anabasine))

• Cleft palate and arthrogryposis mostly occur together

• Brachygnathia superior:

• shortness of the maxillae

• Inherited in dogs and swine

• Large White or Yorkshire breed

• Malapposition of the incisor and cheek teeth,

• Problems in prehension and mastication

Brachygnathia inferior or micrognathia

• Shortness of mandible

• Parrot mouth in horses

• Inherited (autosomal recessive)

• May occur with Cerebellar hypoplasia and osteopetrosis in aberdeen angus cattle

• Prognathism:Abnormal prolongation of the mandibles

• Common in sheep

• develop with recovery from calcium deficiency

• Agnathia: mandibulofacial malformation characterized by absence of the lower jaw

• failure of development of the first branchial arch and associated structures (common in lambs)

• Ateloprosopia: incomplete development of face.

• Bird Tongue: Glossopharyngeal defect in dogs

• Narrow tongue, especially the rostral half.

• Persistent oropharyngeal membrane

• Epitheliogenesis imperfecta: Defect in cutaneous and oral epithelium especially tongue

• Irregular, well-demarcated, red areas from which the epithelium of the oral mucosa

• Teeth develop from horseshoe-shaped thickenings in the oral ectoderm called dental laminae

• Neural crest cells…….tooth buds….enamel organs

• These epithelial structures grow into the underlying ectomesenchyme and organize it to form dental papillae, which they enclose like a cap.

• Dental sac cover both of these

• Tooth develop by root elongation, alveolar bone and periodontal ligament formation

• Tooth eruption initiated by enamel organs which produces TNF & IL-1

• Monocyte recruitment in dental follicle for osteoclast resorption and eruption pathway development

• Inner enamel epithelium initiates odontoblast differentiation from the mesenchyme of papilla

• Odontoblast produces dentin which induce enamel formation

• The free edge of the enamel organ extends beyond the enamel dentin junction, and this extension is called Hertwig's epithelial root

sheath.

• It molds the papilla to form root of tooth

• It fragments and mesenchymal cells from dental sac differentiate into cementoblastwhich produces cementum.

• Remnants of root sheat are called epithelial rests of Malassez. (They persist in the

• periodontal ligament, and may give rise to tumors or cysts)

• May also be important for cementum and periodontal repair

• Cells of the root sheath that adhere to the dentin can produce enamel pearls

• brachydont teeth : in which the enamel is restricted to the tooth crown e.g. carnivores

• hypsodont teeth: enamel extends far down on the roots, invaginated into the dentin to form infundibula

• hypsodont teeth of herbivores, except the mandibular premolars of ruminants, are covered by cementum

• The three hard tissues of teeth are dentin, enamel, and cementum.

• Dentin is light yellow and constitutes most of the tooth.

• It consists of 35% organic matter and 65% mineral

• Normal dentin contains incremental or imbrication lines of Von Ebner which represent normal variation in structure and mineralization of dentin

• contour lines of Owen: incremental lines due to injury

• Hypophosphatemia may cause irregular poorly mineralized dentin

• Enamel has "5% organic matter and "-95% mineral.

• Produced by the tall columnar ameloblasts of the inner enamel epithelium.

• Normalenamel contains incremental lines of Retzius.

• More severe injury, as in fluorosis, or infections by some viruses can produce focal hypoplasia

or aplasia of enamel.

• Cementum is an avascular, bonelike substance, produced by cementoblasts. it contains "55% organic and "-45% inorganic matter.

• Hypercementosis: When extra cementum

• improves the functional properties of teeth, it is called cementum hypertrophy; if not, it is called cementum hyperplasia.

• Periodontium comprises the periodontal ligament, gingival lamina propria, cementum, and alveolar bone

• The periodontium is also a site of origin of tumors

Developmentol onomolies of teeth

• Anodontia: Absence of teeth, sex linked inherited in male calves.

• Oligodontia: Fewer teeth than normal. In horse, cat, dog (inherited)

• In brachycephalic breeds, the cheek teeth are deficient; in toybreeds, the incisors are deficient

• Polyodontia: excessive teeth, occurs in brachycephalic dogs; the incisors are involved

• Pseudopolyodontia: retention of deciduous teeth after eruption of the permanent dentition.

• Heterotopic polyodontia: an extra too&, or teeth, outside the dental arcade e.g. ear tooth of horses in branchiogenic cyst

• Geminous teeth: Single root, partially or completely separate crowns(embryologic

partial division of a tooth primordium.)

• Fused teeth: When dentin of two teeth is confluent

• Concrescent teeth :The dentin is separate but the roots are joined by cementum

• Odontogenic cysts: Epithelium-lined cysts derived from cell rests of Malassez, cell rests of dental laminae, reduced enamel pithelium, or malformed enamel organs

• Dentigerous cysts: cysts that contain part or all of a tooth, which is often malformed e.g. vestigial wolf teeth and vestigial canine in horses

• Odontodysplasia cystica congenita: massivefibro-osseous enlargement of the maxillae and horizontal rami of the mandibles.• Teeth malformed or absent• Congenital disease in Germany• Canine distemper virus can produce hypoplasia of

dentin and enamel• Hypoplasia of the enamel of deciduous teeth

occurs in some calves with intrauterine BVD infection.

Degenerative conditions of teeth and dental tissue

• Pigmentation: Normal enamel white shiny, cementum offwhite/light yellow, dentin dark yellow.

• chronic fluorosis: enamel yellow/brown/black

• Discoloration of brachydont teeth results from pigmentation of dentin e.g. red-brown by pulpal hemorrhages/inflammation, gray-green in putrid pulpitis, yellow in icterus.

• Congenital erythropoietic porphyria(pink tooth)

• Tetracycline treatment of dam also induces yellow to brown pigmentation in calves.

• Tetracyclines are toxic to ameloblasts in late differentiation and early secretory stages.

• Black discoloration of ruminant cheek teeth due to impregnation of mineral salts with chlorophyll and porphyrin pigments from herbage.

• Dental attrition: Loss of tooth structure due to mastication

• Common in herbivores. Occur with age

• Subnormal wear: Occur due to loss of opposing teeth and in oligodontia.

• Abnormal wear: Abnormal chewing due to voluntary/mechanical impairment of jaw

• Odontodystrophies: diseases of teeth caused by nutritional, metabolic, toxic insults leading to malocclusion, and/or accelerated attrition

• Damage to ameloblasts leading to enamel defects• Fluorine poisoning, vitamin A deficiency lead to

ameloblasts, odontoblast differentiation defect. • Calcium deficiency retards eruption, and causes

enamel hypoplasia and mild dentin hypoplasia.• Phosphorus deficiency & vitamin D deficiency,

depresses dentin formation.

Infectious diseases

• Supragingival plaque: on the exposed crown of the tooth and causes dental caries.Bacteriaform a tight biofilm over the enamel pellicle.

• usually gram-positive aerobes. Most are streptococci and Actinomyces spp

• subgingival plaque:in the crevicular groove and causes periodontal disease. gram-negative anaerobes that are asaccharolytic, weakly adherent, and motile

• Porphyromonas spp. (formerly Bacteroides) and spirochetes are likely periodontal

• pathogens in animals.

• Dental calculus (tartar): mineralized plaque

• formed by the deposition of mineral, mainly from saliva, in dead bacteria.Caco3 in horse, dog.

• Chalky white in horse, easy to remove while in dog hard and discolored

Dental caries

• disease of the hard tissues of teeth

• demineralization of the inorganic part and enzymatic degradation of the organic matrix.

• equine infundibular necrosis

• Pit or fissure caries: occur where food and bacteria trap e.g. occlusal surface

• Smooth-surface caries: On proximal surface, plauqe essential.

• Organic acid e.g. lactic acid produced by bacteria induces demineralization

• Enzymes for organic matrix destruction from leucocytes

Pulpitis

• The dental pulp is derived from the dental papilla

• apical foramen, through which vessels and nerves pass is narrow and predisposes to vascular occlusion ischemic necrosis

• Pulpitis is always related to infection

• Bacteria entering via fractured teeth, carious perforations

• Periapical abscess and osteomyelitis of the jaws are complications of pulpitis

Periodontat disease

• most common dental disease of dogs and sheep

• begins as gingivitis associated with subgingival plaque gingival recession and loss of alveolar bone to chronic periodontitis and exfoliation of teeth.

• Clinical gingivitis is usually initiated by accumulation of plaque in the crevice but may be due to seed/fodder entrapment bw teeth

• prostaglandins and matrix metalloproteinasesgenerated in inflamed tissue & bacteria Porphyromonas gingivalis produce enzymes (gingipains) thought to damage junctional epithelium

• Grossly the gingiva is red and swollen, due to the hyperemia and edema of inflammation

• Chronic case….. resorption of alveolar bone

• In dogs gingivitis is proliferative, gingiva being replaced by collagen-poor, highly vascular granulation tissue. Same in cats

• sheep, periodontal disease may involve all teeth, but the effects are most severe on the incisors

• Cara inchada (swollen face) is an epidemic periodontitis of cattle (2-14 month) in Brazil

• Loss of teeth, leading to malnutrition.

• Prevotella (Bacteroides) melaninogenica

• Severe periodontitis and tooth loss are an important part of the syndrome associated with bovine leukocyte adhesion deficiency.