In which condition is the lamina dura completely absent?

The condition in which the lamina dura is completely absent is Paget's disease. In Paget's disease, there is abnormal bone remodeling that leads to the disruption of normal bone architecture, including significant changes to the lamina dura. This disease primarily affects older individuals and results in enlarged and weakened bones, making them more susceptible to deformation and fractures.

In Paget's disease, the lamina dura, which is a thin layer of dense bone that lines the tooth socket and is visible on dental radiographs, becomes compromised. The disease alters both the osteoblastic and osteoclastic activity, thus leading to a disorganized and poorly mineralized bone structure where the lamina dura is often completely lost.

Other conditions, such as those mentioned in the question, do not typically result in the complete absence of lamina dura. For instance, in osteosarcoma, while there may be involvement of the jawbone, the lamina dura might be affected depending on the extent of the disease but is not characteristically absent. Similarly, periapical granulomas are associated with a dental infection and can lead to changes in the surrounding bone but won’t cause a total absence of the lamina dura. Von Recklinghausen's disease, or neurofib