Can Dexa scans reveal a false positive? Why would a normal X-ray not reveal fragile bones?

I think it is interesting that the moderators will allow open discussion of a brand name medication but not allow a book title!  Putting that aside, the medication under discussion, the brand name for  raloxifene does appear to be better than some of the meds that have been pushed on us over the years.  It works in a similar way with the bones, however, by decreasing the number and efficiency of the osteoclasts.  These are the cells that break down bone and are very important in maintaining the health and resiliency of bone.  The trick is to make sure they don't do their job more efficiently than the osteoblasts which create new bone.  We really want methods that encourage the production of natural new bone.  Does anyone out there know what the long term prognosis is for people on  raloxifene for several years?  We know that after a number of years with the traditional drugs the bones become more brittle and liable to fracture because old bone has not been properly replaced with new.