Dental Discolouration

Introduction

The normal colour of teeth varies and depends on the shade, translucency and thickness of the enamel.

There are two basic kinds of discolouration:

Intrinsic staining: secondary to endogenous factors discolouring the underlying dentine

Extrinsic staining: from surface accumulation of exogenous pigment

Discolourations can also be generalised or local, and pseudodiscolourations refer to extrinsic staining by dental plaque or agents in foods.

Discolouration of teeth is extremely common in all animals and affects all species and all breeds.

Aetiology

Extrinsic Staining

Bacterial stains: green to black-brown to orange colour, from chromogenic bacteria.

Plaque-related: black-brown stain, due to the formation of ferric-sulfide from interaction of bacterial ferric sulfide and iron in the saliva.

Foods: charcoal biscuits can penetrate pits and fissures in the enamel, green from foods containing abundant chlorophyll.

Gingival haemorrhage: green from breakdown of haemoglobin into green biliverdin

Dental restorative materials: black-grey from amalgam

Medications: black from products containing iron or iodide, yellow-brown from products containing sulfide or silver nitrate, green from products containing copper or nickel, golden brown from products containing cadmium.

Metal: wear from chewing on cages or from removed endodontic bands or wires

Crown fragments: less translucent due to dehydration of the fragment

Discoloured restorations

Tooth wear and dentin exposure: secondary dentin, tertiary dentin, reparative dentin

Intrinsic Staining

Hyperbilirubinaemia: affects all teeth, occurs when dentin is being formed and bilirubin accumulates in the tooth. Lines of resolution may be seen on the teeth if the problem is solved during dentin development

Red blood cell destruction: following traumatic injury to the tooth. Haemoglobin breakdown in the pulp from a pulpitis, which progresses from pink to grey to black.

Amelogenesis imperfecta: developmental alteration in the structure of the enamel, giving a chalky appearance and a pinkish colour to all teeth.

Infectious agents: parvovirus and distemper virus especially affect the formation of enamel. There is enamel hypoplasia and the pitted areas have black edges and the dentin is brownish.

Dental fluorosis: excess fluoride consumption leads to enamel hypoplasia with black edges. The enamel is lusterless and has yellow-brown zones of discolouration.

Internal Resorption

Pulpal injury causes vascular changes with increased oxygen tension and a decreased pH, resulting in destruction of the tooth from within the pulp from dentinoclasts.

The tooth has a pinkish hue.

External Resorption

This is caused by many conditions such as trauma, orthodontic treatment, periodontal disease, tumours and periapical inflammation. Osteoclasts resorb the tooth structure.

Medications

Tetracycline: binds to calcium and forms a calcium orthophosphate complex that is laid down into the collagen matrix of the enamel. It results in a yellow-brown discolouration. This can only occur when the enamel is being formed.

Amalgam

Iodine or essential oils

Macrolide antibiotics: hypocalcification leading to white lesions with horizontal stripes on the enamel

Clinical Signs

There will be abnormal colouration of a tooth or teeth.

There may only be rings or lines of discolouration.

Diagnosis

There may be a history of treatment with a particular drug or supplement, or a history of trauma.

If the animal is young this may indicate a developmental process.

Food or plaque-related discolourations should be obvious on close dental examination and probing.

Radiographs should be performed to assess the viability of the tooth.

Treatment

For extrinsic staining, internal or external bleaching can be performed, or veneers or crowns can be placed on the tooth.

For intrinsic staining, endodontic treatment is often the treatment of choice.

Restorative procedures such as crowns or veneers will protect both the tooth and the pulp.

Unfortunately, the discolouration often persists following treatment.

Dental Discolouration Learning Resources
Flashcards Test your knowledge using flashcard type questions	Veterinary Dentistry Q&A 04

References

Verstraete, F. (1999) Veterinary Dentistry Self-Assessment Colour Review Manson Publishing

Lobprise, H. (2007) Blackwell's Five Minute Consult Clinical Companion: Veterinary Dentistry Wiley-Blackwell

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