Yes, boron will combine/bind with fluoride rendering it impotent and allowing for harmless excretion. A casual search will find much supporting documentation for the following. Note though there is also such a thing as too much boron...
Fluoride in the form added to tap water and toothpaste is, I believe, a threat to health as evidenced by much research1 that has been totally ignored by those that want to make money out of finding a way to dispose of the toxic waste, that is too toxic to dump elsewhere, and the Government cronies that back them. Fluoride in sea water is in a form and combination with all the other minerals and trace elements that renders it non-toxic. There is good evidence that in Andra Pradesh India people can develop quadriplegia (when all four limbs are not working well as the result of skeletal fluorosis where 1.35 ppm fluoride was present in the water. Boron will inactivate fluoride in the body forming a harmless compound, according to Dr. Rex e. Newman.
Fluoride poisoning from MERCK Veterinary manual- I know it may be a controversial source for some...
Treatment and Control:
Acutely exposed animals require calcium gluconate (IV) and oral magnesium hydroxide or milk to bind fluoride before absorption. In chronic exposure, control is difficult unless animals are removed from affected areas. It has been suggested that affected areas may be used for animals with a relatively short production life, eg, pigs, poultry, or finishing cattle and sheep. Feeding calcium carbonate, aluminum oxide, aluminum sulfate, magnesium metasilicate, or boron has either decreased absorption or increased excretion of fluoride, and thus could offer some control of chronic fluorosis under some conditions. However, no treatment has been shown to cure the chronic effects of fluorine toxicity.
Elsar J, Merad B, Denine R, Reggabi M, Benali M, Alamir B, Rachidi MA. (1979). Effect of fluoride intoxication of several months on homeostasis in rabbit in the presence and absence of an antidote (Boron). Fluoride, 12: 136-143.
Fresh fruits and vegetables are the main dietary sources of boron. The estimated average daily intake for Americans is between 1.7 and 7 milligrams daily. A diet high in fresh fruits and vegetables is known to offer significant protection against osteoporosis and osteoarthritis (Murray, 1996).
If one wanted to supplement due to boron poor soils etc, I suspect the boron citrate would be good, although there are some food based boron supplements on the market that may be better.
If there is a fracture or even chipped bones - take extra magnesium plus a lick of borax (lick one side of the top third of the index finger is your best guide. Your finger is in proportion to the rest of the body.) These 2 minerals together take the pain out of a fracture (old or new) within 2 days and helps the fracture to heal better.