The book, The Sunlight Solution, by Laurie Winn Carlson has an excellent description of the investigation of the cause of rickets.
On pages 105-107, she describes how teeth health was known since the 1930's to be improved with vitamin D, sunshine, and full spectrum bulbs in classrooms.
800 IU was found to be needed for dental health in the Winter in one location, probably for light-skinned children.

You can "look inside" of the book at Amazon. New $15, Kindle $10, Used $2, published March 2009

You can see from the table of contents that this book is different from other books on vitamin D.
Many interesting ideas.

I am investigating her idea described chapter 8 Solar/Global Dimming: due to smog, contrails, dust in the air, tropospheric ozone, etc.
Lots of controversy about how much reduction in sunlight there has been in the past 40 or so years.

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See also VitaminDWiki

• All items in category Dental and Vitamin D 116 items
• Hypothesis: Periodontal disease is related to vitamin D – 2010 Dr. Grant
• Teeth and vitamin D 2009 book
  On pages 105-107, she describes how teeth health was known since the 1930's to be improved with vitamin D, sunshine, and full spectrum bulbs in classrooms.
• UVB and Vitamin D might decrease dental caries better than fluoride– July 2011
• Vitamin Deficiency Underlies Tooth Decay – 2009 and 1931
• Vitamin D history back to Egyptians and fortification - Aug 2011
  Herodotus noticed Egyptians with bare heads had much stronger skulls than Persians
• Even 1,000 IU vitamin D reduced periodontitis – Jan 2011
• Children with severe caries were 2X more likely to have inadequate vitamin D – July 2012
• Dental caries reduced by vitamin D by half, review of 24 old clinical trials – Nov 2012