As I mentioned this is plant based not metal strontium. And I had a 5% increase in bone density in one year taking 16 mg /day

Yes, the dexa reading for a bone with strontium is considered to be over read by about 10% due to the way strontium affects the radiation used in the dexa analysis. But we no longer have to depend on DEXA; REMS and TBS both are not affected by the strontium radiation overread of DEXA. Interestingly, a TBS study of bone quality found strontium bones to be in the top 3 of treatments for bone quality. But even if you depend on DEXA it is only the first reading on strontium treatment that is pertinent for what is called the 10% strontium skew, after that you are just cking to make sure that your bone density continues to increase.
So this "oh no the dexa misreads strontium what will we do" scenario is no longer relevant. We now have REMS and TBS, and both those bone tests all say that strontium bone is dense and good quality bone. Plus, we have a research study with bone biopsies of strontium bone and viola good bone density and good bone quality. Amazing what mother nature has wrought with calcium and strontium in our water and ground.
https://www.inspire.com/groups/bone-health-and-osteoporosis/discussion/tbs-dexa-and-strontium/reply/7712668597918129698/
https://onlinelibrary.wiley.com/doi/full/10.1359/jbmr.071012