Understanding Tooth Anatomy – What’s Happening Below the Gum Line

Teeth are like icebergs – two-thirds lies beneath.

When we look inside our pet’s mouth, we only see a portion of each tooth. In fact, a significant part of every tooth lies hidden below the gum line, which is why dental disease can be much more advanced than it appears during a quick visual examination.

To understand how periodontal disease develops, it helps to first understand the basic anatomy of a tooth and the structures that support it.

The Anatomy of the Tooth

The Crown

The crown is the visible part of the tooth above the gum line. It is covered by enamel, the hardest substance in the body, which protects the underlying structures from daily wear and tear. While enamel is incredibly strong, it cannot protect the tooth from the effects of plaque and periodontal disease that develop around the gums.

The Root

Below the gum line is the root of the tooth. The root anchors the tooth firmly within the jawbone and is often much longer than the visible crown. Because roots are hidden beneath the gums, problems such as infection, bone loss, root fractures, and abscesses may not be visible without dental X-rays.

Dentine and Pulp

Beneath the enamel lies dentine, a living tissue that makes up most of the tooth structure.
At the centre of the tooth is the pulp chamber, which contains:

• Blood vessels

• Nerves

• Connective tissue

The pulp is responsible for keeping the tooth alive and healthy. When disease or trauma reaches the pulp, it can be extremely painful and may result in infection.

The Periodontium: The Tooth’s Support System

Just as important as the tooth itself are the tissues that surround and support it. Collectively, these tissues are known as the periodontium, and they are the primary target of periodontal disease. The periodontium consists of:

• Gingiva (Gums)
  The soft tissue that surrounds the teeth and acts as a protective barrier against bacteria.

• Periodontal Ligament
  Tiny fibres that connect the tooth root to the surrounding bone. These fibres act like shock absorbers, helping support the tooth during chewing.

• Cementum
  A specialised layer covering the root surface that allows the periodontal ligament to attach to the tooth.

• Alveolar Bone
  The portion of the jawbone that surrounds and supports the tooth roots.

Why This Matters

Periodontal disease doesn’t usually start by damaging the tooth itself.
Instead, it attacks the structures that hold the tooth in place.

As inflammation progresses:

• The gums become irritated and inflamed.

• Bacteria move below the gum line.

• The periodontal ligament begins to break down.

• Supporting bone is lost.

• Teeth become loose and may eventually require extraction.

Think of it like a fence post. The post itself may be perfectly sound, but if the soil and concrete supporting it gradually erode, the fence will eventually become unstable and fall over.

The same thing happens with teeth. A tooth can appear relatively normal, but if the supporting structures beneath the gums are being destroyed by periodontal disease, that tooth is at risk.

This is why veterinarians are so focused not only on keeping teeth clean, but on preserving the health of the gums, ligaments, and bone that support them.