Periodontal radiographic assessment: Normal appearances

I will be going over some basic radiographic appearances of periodontal health and disease for the next few weeks.  This first week is a starter on normal radiographic appearances of periodontal health.

Types of Radiographs

The two intraoral radiographs that are used for periodontal assessment are bitewing radiographs and periapical radiographs. Of these two, bitewing radiographs should ALWAYS be evaluated first (if they are available).  The reason for this is the vertical angulation of bitewing radiographs is closer to 0 degrees whereas periapical radiographs tend to have a large vertical angle of 30 degrees or more.  The closer the vertical angle is to 0, the better the radiograph will provide an accurate representation of where the bone level is in relation to the cemento-enamel junction.  Look at the example radiographs below specifically where the bone appears in relation to the cemento-enamel junction of the maxillary molars.

Normal Horizontal Bone Levels

The range of normal bone levels are when the crest of the alveolar ridge is 0.5 to 2.0 mm apical to the cemento-enamel junction.  In the anterior region, the crest of the alveolar ridge may have a pointed appearance due to smaller interproximal spacing between the teeth.

In the posterior region, the crest of the alveolar ridge will be flatter.  When evaluating the bone level in the posterior follow these steps.

• Identify the location of the cemento-enamel junction of two adjacent teeth.

• Imagine a line between these two points.

• Compare this line to the line of the crest of the alveolar ridge.

If both of the lines are parallel and the bone is 2.0 mm or less apical from the cemento-enamel junction, this is normal horizontal bone levels between the two adjacent teeth. Beware of when the crest of the alveolar ridge appears angled as it does not immediately indicate abnormal bone loss as seen on this bitewing radiograph between the mandibular premolars (follow the above steps and you will note that the crest of the alveolar ridge is within the range of normal).

The coming posts will define what to interpret when the lines are not parallel or more than 2.0 mm apical from the cemento-enamel junction.

Other Normal Radiographic Appearances

This last category is primarily about the periodontal ligament space and lamina dura at the crest of the alveolar ridge.  As the periodontal ligament space approaches the crest of the alveolar it tends to widen slightly due to everyday occlusal trauma (i.e. chewing, bruxism, clenching).  This is within the range of normal if it is a slight widening and not starting to pull away from the tooth creating a radiolucent triangle.

Note the slight widening of the distal of the maxillary second premolar (arrow).

On this radiograph, note the slight widening of the distal of the maxillary first premolar. The mesial of the maxillary second premolar is triangular in shape and abnormal bone loss (to be covered in coming posts).

Next week: Horizontal bone loss and vertical bone defects

If you have any questions or comments, please leave them below in the comments. Thanks and enjoy!