

Home | Up

The mouth - a hidden organ system

September 2007 is Pet Smile Month when nearly 1500 veterinary practices throughout the UK will be offering free dental check-ups as, it is very reliably estimated, 70-80 % of dogs older than three years old have some form of gum or mouth disease. This accounts for untold pain and illness most of which is treatable and nearly all is preventable. More to the point, how would you like doing agility with toothache? In the first of a series of articles, vet dentistry specialist Gerhard Putter explains more about this important and oft forgotten aspect of your dog's health.

The mouth and teeth of dogs is very important organ system that has a much wider function in the dogs than ingestion of food such as exploring the environment, handling toys, weapons for aggression and self protection to name but a few. Apart from relatively small differences, the anatomy of the mouth in humans and dogs are surprisingly similar. We can safely assume discomfort and pain associated with mouth and tooth disease in humans and dogs are experienced in a very similar way. 

Inside the mouth
The mouth cavity (oral cavity) consists of the space enclosed by the lips and extends backwards to the base of the tongue. It consist of various components including:-
  • Tongue
  • Hard and soft palate
  • Teeth gum (gingiva)
  • Mucus membrane

Some salivary glands are situated in the mouth, but others are remotely positioned( e.g. at the base of the ear) with the saliva transported to the mouth via tubes that opens into the oral cavity.

The enamel that forms a cap on the crown of all teeth is the hardest substance in the body and is completely formed by the time that the tooth erupts. The biggest bulk of the tooth consists of dentinDentin is very strong living tissue that is formed throughout life.

A dog mouth with well fitting teeth and only minimal tartar  accumulation

A space in the centre of all teeth - the so called root canal or pulp chamber - houses the pulp which consists of a fine network of blood and lymphatic vessels, nerves in loose connective tissue and supplies nutrients and oxygen and remove waste products to maintain the health of the tooth.  These vessels and nerves enter the tooth at the tip (or apex) of the root and are branches of larger vessels and nerves that lies within the bone of the upper and lower jaws.

The teeth are situated in special sockets in the bone of both the upper and lower jaws. A thin fibrous membrane attaches the root of the teeth to the bone of the jaw and is known as the periodontal ligament. This ligament allows slight movement of the tooth within the socket and acts as a shock absorber.

The soft tissue in the mouth consists basically of two types.

  1. Gum (or gingiva) is strong, inelastic and relatively insensitive tissue that forms a band along the dental arcade and forms a tight seal against the teeth.   The largest part of the palate is also covered by a very similar tough tissue.

  2. Mucus membrane
    The rest of the inside of the mouth (thus the inside of the lips and cheeks and the space between the insides if the lower teeth that reflects onto the underside of the tongue) is lined by mucus membrane (or oral mucosa).  This mucus membrane is far more elastic, mobile and fragile than gum tissue. The top surface of the tongue is covered by specialised tissue that includes the taste buds

Gum and tooth disease
Why do dogs then appear not to be bothered by gum and mouth disease that humans would find very painful? One possible explanation is that the survival instinct of dogs is much stronger than in humans and that the need to eat overrides even some significant discomfort.  Dogs also accommodate painful teeth by changing the way they chew, and could even swallow their food without much chewing at all.  So it does hurt, but our canine friends have other priorities!   

A safe assumption, therefore, is that if a condition or injury would be painful in our own mouths, it would be very similarly painful and distressing in our dogs!   The blood supply to the bone and soft tissue of the mouth is very well developed.  Wounds in the mouth therefore heal very rapidly even though the bacteria within the mouth are potentially harmful.  This has also some far reaching implication in the diseased mouth, but would be discussed later in this series.

September is Pet Smile Month and all participating veterinary practices offers free dental checks during this time. This is a genuine effort to inform pet owners about the importance of health mouths and teeth and its effect on longevity and quality of life. Consult the dedicated Pet Smile Month website for a list of participating veterinary practices as well as other information on dental issues. www.PetSmile.org

Diagram of dog tooth
Drawing: Ben CHaracter

Gingivitis and periodontal disease
This is therefore one of the most common disease complexes affecting out canine companions! The crowns of teeth protrude above the gum line and are for obviously functional reasons not covered by mucus membrane. This implies that teeth are not protected by the natural protective mechanisms (White blood cells and antibodies) that protect the soft tissue surfaces. Sticky sugars and proteins from saliva and food debris stick to this inert surface. It is very rapidly colonised by opportunistic bacteria that uses these substances as protection and nutrition and multiplies quickly. Undisturbed multiplication of these organisms change the conditions within this bio film and make it ideal for more harmful types. This soft film is known as plaque.

Calcium, phosphate and other minerals from saliva causes mineralisation of plague. The resultant tartar - also called calculus - is a rock hard and very firmly attaches to the tooth surface. Tartar slowly builds up over time the lower oxygen levels in the deeper layers of the tartar changes the environment and supports the establishment of more harmful bacterial populations. 

These bacteria also tend to produce more potent toxins that cause tissue injury and destruction. It is these bacterial products that trigger the inflammation of the gum (gingivitis).

The support system of the tooth consists of gum, periodontal ligament and the bony socket in the jaw and is collectively known as the periodontal tissue.  If left unattended gingivitis could affect this deeper support system of the tooth with the resultant attachment loss of the toothInflammation of periodontal tissue is known as periodontal disease or (periodontitis)

 Any questions about issues covered in this article could be sent to gerhard@mulberryvets.co.uk.  Other topics in this series will include:

  • Gingivitis and periodontal disease
  • Malocclusion
  • Fractured teeth
  • Dental home care

About the author
Gerhard Putter MRCVS qualified as a veterinary surgeon in 1984 in South Africa. He has a life long interest in veterinary dentistry and has concentrated on this discipline in recent years.  He is the principle veterinary surgeon of Mulberry Court Veterinary Surgery in Sudbury in Suffolk and accepts referral work in dentistry and orofacial surgery.

He is also currently the Public Relations Officer of the British Veterinary Dental Association (BVDA)

First published: 16 September 2007