What distinguishes a Class III caries lesion?

A Class III caries lesion is characterized by its location and the extent of decay. Specifically, this type of cavity is found on the proximal surfaces of anterior teeth, typically between the incisors or between a lateral incisor and a canine. While the question addresses characteristics of Class III caries, the defining factor for this classification is that it does not involve the incisal edge but is instead primarily located between teeth.

The correct answer emphasizes that Class III carious lesions typically compromise the tooth structure without extending to the pulp, as seen in more advanced classifications, such as Class IV. Therefore, the defining feature of a Class III lesion is its specific interproximal location, which often involves dental surfaces that are least visible when teeth are in occlusion.

The other options do not accurately describe Class III caries. For instance, extending into the nasopalatine canal or involving any sort of cyst would pertain to different dental pathologies or anatomical considerations, and these do not define the nature of Class III lesions. Similarly, extending through the dentin-enamel junction (DEJ) towards the pulp would indicate a more severe degree of decay, typically aligned with Class IV or deeper carious lesions.