UVB light is very important for reptiles like bearded dragons to be exposed to. Though vitamin D3 can be provided by dusting insects with it, knowing the correct amount the dragon needs is extremely difficult, if not impossible by using dusting alone.
Also it is very unlikely you can visually tell if a dragon is 'ok' in bone density as MBD only really manifests itself visually when it has progressed to the point were bones are rubbery (weak jaws, long bones bending/curving when they shouldn't be), muscle spasms occur as calcium is also used to regulate nerve tissue etc.
The only way to know if you are giving enough D3 and calcium is regular blood tests and x-rays by an experienced vet who knows how to look for early signs of MBD. MBD is often a late sign of low blood calcium and lack of UVB rays or Vitamin D3 in the diet isn't the only cause of it.
Exposure to unfiltered natural sunlight will ensure the dragon naturally produces all the D3 it needs to properly metabolize calcium, providing he is getting enough calcium into his body, not getting too much phosphorus or oxates that interfere with absorption of calcium. I suggest an hour of natural sunlight (supervised, never leave your bearded dragon outside alone, especially if he isn't kept in a secure cage outside, with proper thermal gradients so he can escape the sun if it gets too hot) about 3-5 days a week. Three hours in the sun once a week isn't enough as the body will only make so much D3 before it stops, as the body will only produce as much as it needs for that day. D3 isn't stored for very long if at all.
Don't put dragons outside in glass tanks, these overheat too fast and will bake your dragon quickly. Rubbermaid containers that are large enough to give room for yoru dragon to move about and take shelter if it is too hot, are good. The screen cages are great, as most can be quickly folded away (most are tall but you can always lie down so there is more floor space than height. The screen will block some UVB rays but the sun puts out more than enough it won't be a real concern). IT is possible to use a harness with your dragon outside (keep on a tether, as dragons can move really fast if they decide they want to run) though I don't recommend these as it is just too easy for a dragon to get away or harm themselves as the harness or the lead can catch on something and injure your dragon. However, if you don't keep him in a container outside in natural sunlight, then use a lead but again, never leave your dragon tied outside alone like a dog, as they are not dogs and can quickly tangle themselves or wind up being a neighbor's cat or dog's dinner or a passing bird, such as a crow, raven or hawk.
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PHLdyPayne
