Periodontal Ligament Space
The thin radiolucent line visible on dental radiographs between the root surface and the surrounding alveolar bone, representing the periodontal ligament.
Full Definition
The periodontal ligament space (PDL space) appears as a uniform radiolucent line of approximately 0.2–0.4 mm width on high-quality periapical radiographs in a healthy dentition. Widening of the PDL space is a key radiographic indicator of occlusal trauma, apical periodontitis, or early dental cyst formation, while its absence or obliteration may indicate ankylosis. Editors should note that 'periodontal ligament space' and 'periodontal ligament' are not synonymous: the former is the radiographic representation, while the latter is the anatomical structure. The term should always be written in full on first use; PDL space is acceptable thereafter.
Usage
Usage note: 'Periodontal membrane space' is an older synonym now largely superseded; editors should update this phrasing to 'periodontal ligament space' in manuscripts unless quoting historical literature.
In Context
- "Uniform widening of the periodontal ligament space around the root of the lower right second molar suggests occlusal overload." — Periodontal radiology report
- "Loss of the normal PDL space radiographic outline is a key finding in ankylosis following replantation of an avulsed tooth." — Oral surgery textbook