The reversal line may be a key modulator of osteoblast function: observations from an alveolar bone wound-healing model.

The reversal line demarcates the cessation of osteoclast activity from the commencement of osteoblast activity at a remodeling site in bone. It is a seam between segments of bone that are formed at different times. We believe that the reversal line contains regulatory signals that, in part, control osteoblast activity. We have conducted a pilot study to examine the fate of reversal lines during abnormal bone remodeling in alveolar bone. A surgical periodontal defect was created in a Cynomolgus monkey (Macaca fascicularis), allowed to heal in the presence of plaque, and evaluated histologically. In this model, there is an acute inflammatory reaction followed by compromised bone formation. Woven bone rather than lamellar bone was deposited in the defect. A striking finding in this wound-healing model was the disruption of the carbohydrate material along the reversal line. This supports our theory that disruption of the signaling molecules in the reversal line may be responsible for uneven woven bone formation.