What Is the Cementoenamel Junction (CEJ)?

Understanding the various parts of the tooth can help patients understand the many conditions that can affect the teeth and gums. One of these components, the cementoenamel junction (CEJ), is the source of tooth sensitivity for many people. Learning more about the CEJ and how to protect it from unnecessary wear can help you prevent dental sensitivity.

What Is the Cementoenamel Junction (CEJ)?

The cementoenamel junction is the specific line around the perimeter of the tooth where the enamel covering the crown of the tooth meets the cementum covering the root. In most cases, the cementum overlaps the enamel around the tooth, but in some people this area is a thin band of exposed dentin. It is at this location where the hard, mineralized enamel stops and the less-mineralized root covering begins.

Ideally, the CEJ is covered by the gingiva (gums) and the periodontal ligaments (gingival fibers) that attach around it to the root of the tooth. This covering of connective tissue acts like a tight turtleneck around the neck of the tooth, keeping the less-mineralized root surface warm and protected from bacteria and acids.

What Happens When the CEJ Is Exposed?

If the gums recede and the CEJ is exposed to the rest of the mouth, the vulnerable cementum can be more easily removed by wear and tear from aggressive brushing, clenching or chewing. When the cementum is removed and the second layer, the dentin, is exposed, patients may start to feel sensitivity to hot and cold foods, according to the American Dental Association. This process of the gums coming away from the neck of the tooth and shrinking down is called recession. To determine whether the CEJ is exposed and to what degree, dental professionals will measure the clinical attachment of the gums to the tooth around the CEJ.

Measuring the Clinical Attachment of Gums

When probing the gum tissue to assess gingival health, dental professionals carefully place a small measuring ruler called a periodontal probe in the space along the CEJ. During this assessment, the clinician will also note any areas where the gums are receded, comparing those areas to previous charting visits. In completing this process, dental professionals can evaluate whether the attachment fibers between the teeth and the bone are healthy, or if the patient is at risk for periodontal infections, inflammation or future recession.

Tooth anatomy may seem complex, but it's worth learning a few basic terms to help you better understand your oral care. If you're curious for more facts, ask your dentist or dental hygienist; they know all about it!

This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to be a substitute for professional advice, diagnosis or treatment. Always seek the advice of your dentist or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.

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What Are The Different Parts Of A Tooth?

Each tooth has several distinct parts; here is an overview of each part:

  • Enamel – this is the outer and hardest part of the tooth that has the most mineralized tissue in the body. It can be damaged by decay if teeth are not cared for properly.

  • Dentin – this is the layer of the tooth under the enamel. If decay makes it through the enamel, it next attacks the dentin — where millions of tiny tubes lead directly to the dental pulp.

  • Pulp – this is the soft tissue found in the center of all teeth, where the nerve tissue and blood vessels are located. If tooth decay reaches the pulp, you usually feel pain and may require a root canal procedure.