American Board of Orthodontics (ABO) Practice Exam 2026 - Free Orthodontics Practice Questions and Study Guide

Ankylosis is a condition in which a tooth becomes fused to the surrounding alveolar bone, leading to a lack of normal mobility that is typically associated with teeth. When a tooth is ankylosed, the periodontal ligament space is absent, and the tooth and bone essentially become one unit. This fusion typically results in a lack of physiological movement of the tooth during normal occlusion or when subjected to forces from neighboring teeth, which signifies that it is adhered to the bone structure.

The presence of ankylosis can often be observed radiographically, where the absence of the periodontal ligament space can be noted around the affected tooth. This concept differentiates it from other conditions that may affect dental health. For instance, mobility of the tooth would suggest a periodontal problem rather than ankylosis, vibrant color would have no direct relevance to the condition of the tooth being ankylosed, and development of caries pertains more to decay and does not indicate ankylosis. This is why fusion to bone is the hallmark indicator of ankylosis in a tooth.