Cervical burnout is an area of apparently increased radiolucency in the mesial and distal cervical (neck) regions of the tooth. Such regions are often mistaken for interproximal caries when in fact they only appear radiolucent because they have neither the radiopaque enamel of the region immediately above nor the bone tissue below.
Figure 5 illustrates cervical burnout in a premolar bitewing radiographic image. Note that the cementoenamel junction and the crest of the alveolar bone lie respectively just above and just below the burnout area. As a point of comparison, note the interproximal enamel caries on the first and second premolars.