What symptom may indicate ankylosis when tapping on the affected tooth?

Ankylosis of a tooth is characterized by the fusion of the tooth's root to the surrounding bone, which can be indicated by the quality of sound produced when the tooth is tapped. When a tooth is ankylosed, the expected normal sound produced by tapping the tooth is altered.

A hollow sound is associated with the absence of a periodontal ligament, which is the case when ankylosis occurs. This absence changes the way sound is transmitted through the tooth and the surrounding structures, resulting in a more resonant, hollow sound that differentiates it from the sound produced by healthy teeth that are properly attached to the alveolar bone via the periodontal ligament. This hollow sound signifies the abnormality of the tooth's attachment and helps in diagnosing the condition.

In contrast, a soft or normal sound would indicate that the tooth is still correctly anchored with the periodontal ligament, while a deaf sound does not specifically signify ankylosis but may suggest other issues with tooth vitality or structure. Thus, the hollow sound is a telling indicator of the presence of ankylosis when tapping the affected tooth.