Osseous defects are the bone changes that are associated with periodontal disease other than the horizontal bone loss.
Interproximal crater is a trough like or saucer shaped defect occuring in the alveolar crest of the interproximal bone.The bony defect has four walls – the buccal and lingual cortical plates and the roots of two adjacent teeth.The marginal bone of the interproximal crater appears thin.
2.Proximal intrabony defect:
Proximal intrabony defect is a vertical defect of the bone extending from the crest of the alveolus and in an apical direction.It is a defect surrounded by four walls,the buccal and the lingual cortical plate,the hemiseptum and the root of the involved teeth.Radiographically the proximal intrabony defect appears “v” shaped adjacent to the affected root surface.
A hemiseptum is defined as the bone of the interdental septum that remains on the root of the uninvolved adjacent tooth after destruction of either the mesial or the distal portion of the interproximal bone septum.The hemiseptum results due to the loss of bone on the mesial or the distal aspect of a root surface.Radiographically the hemiseptum is a “V” or “U” shaped.
4.Inconsistent bony margins:
Inconsistent bony margins refer to irregular resorption of the cortical bone of the buccal or lingual alveolar cortical plate.Radiographically this bony change appears as irregular loss of the height of the alveolar crest.
Bony pockets usually occur together with proximal bony defects.Bony pockets are seen on the buccal aspect of the roots.Radiographs may not be very useful in the diagnosis of bony defects on the buccal or the lingual cortex.