 Under ischaemic conditions numerous pathological changes in the bone marrow and trabeculae of oral cancellous bone have been documented.Microscopically, areas of ""apparent fatty degeneration and/or necrosis, often with pooled fat from destroyed adipose cells (oil cysts) and with marrow fibrosis (reticular fatty degeneration)"" are seen.These changes are present even if ""most bony trabeculae appear at first glance viable, mature and otherwise normal, but closer inspection demonstrates focal loss of osteocytes and variable micro cracking (splitting along natural cleavage planes).