Full-text evidence summary

Donate $100 or more...

...and receive an autographed and dedicated copy of Dr. Cannell's new book.

Dental caries Exposure to sunlight

There are a number of papers in the literature reporting prevalence of dental caries in the United States with respect to geographical location in which the strongest correlation is with solar UVB. 

There are a number of papers in the literature reporting prevalence of dental caries in the United States with respect to geographical location in which the strongest correlation is with solar UVB.

The first study reporting a latitudinal gradient in dental caries was a report of men rejected from the draft for the Civil War for lost teeth, from 8 per 1000 men in KY to 25 in New England1.

The first study to link geographical variation in caries prevalence to local hours of sunlight was that by Mills2 using data for adolescent males aged between 12 and 14 years from a cross-sectional survey in 1933-343. He placed isopleths of arithmetic averages of county indices of dental caries for school children living in rural areas or towns of less than 5000 population in 19 states on a map of the United States, revealing a general increase with increasing latitude, with an anomaly in the Rocky Mountain States. There was a factor of greater than three between the indices for Oklahoma (150 caries/100 children) and Pennsylvania (531). He also found an inverse correlation with respect to water hardness, with a estimated best-fit reduction of 33% for >500 ppm vs.

In another paper using the same data set, East4 found that dental caries were inversely related to mean hours of sunlight/year, with those living in the sunny west (3000 hours of sunlight/year) having half as many carious lesions as those in the much less sunny northeast (

East referred to other contemporaneous papers supportive of a role for vitamin D 5 and season6 in predicting the risk of caries.

Numerous other studies have reported geographical variations in dental caries, some linking the variations to differences in solar radiation. If a mechanism for the effect of sunlight was discussed, it was production of vitamin D and improved calcium absorption and metabolism.

In a later study, ranking of dental health systems were developed for young men entering the armed forces for World War I and World War II 7. The northeast had the worst ranking, while states near Texas had the best ranking. A simple ecological analysis of the rankings using summertime UVB and urban residence for 1960 found an adjusted R2 = 0.64 (standardized coefficient beta for UVB = -0.72, p8.

A series of studies on dental caries among school children were conducted in Oregon in the 1950s9 10 11 showed less dental caries in schoolchildren living in a sunny inland county than in those living in a coastal county or in Willamette Valley, known for its low annual hours of sunlight. These studies controlled for fluoride in water supply, density of dentists, consumption of candy bars and of carbonated drinks and it was suggested that vitamin D increased calcification during tooth formation.

Another study investigated dental status of prehistoric remains of residents in various regions in Oregon12. The poorest dental condition was found in Willamette Valley, as in the studies from the 1950s. The best dental conditions were found in the Lower Columbia Valley, the coast, and central Oregon. Some of the findings were related to diet, with poorer dental condition where plant foods were used predominantly whilst higher fish consumption in those living in the Lower Columbia Valley and on the coast could well have provided more dietary vitamin D.

The caries index score for "decay, missing, and fillings (DMF) in teeth in 12-yr-old children in Australia were higher in the southern states whilst rates of edentulousness in 35-44-yr-olds in Tasmania (latitude 40º-45º S) were double those found in the more northerly states13".

A study of 11-year-old children from across England and Wales, Scotland, Isle of Man, and Jersey was conducted in 2004/5. It found: Mean decayed, missing, and filled primary teeth (D3MFT) across England was 0.64 (D3T = 0.32, MT = 0.06, FT = 0.25), across Wales it was 1.09 (D3T = 0.48, MT 0.11, FT = 0.50), and across Scotland values were 1.29 (D3T = 0.52, MT = 0.17, FT = 0.60). Overall, 31.3% of children in England & Wales and 47.1% of children inspected in Scotland had evidence of caries experience in dentine (D3MFT > 0, including visual dentine caries)14.

Further evidence for a role of UVB in reducing the risk of dental caries comes from an ecological study of the geographical variation of dental caries with respect to that of multiple sclerosis in the United States, the world, and with respect to ethnic background. Multiple sclerosis is strongly linked to low solar UVB in winter15 and low serum 25(OH)D concentrations16.

“The geographical distribution and other epidemiological characteristics of multiple sclerosis (MS) are compared with those of dental caries. The rates of death due to MS in Australian states are linearly related to the numbers of decayed, missing, and filled (DMF) teeth found in individuals from those states (r=0.97, P less than 0.002). In the United States of America, a strong positive correlation (r=0.55, P less than 0.001) also exists between MS death rates and dental caries indices. The prevalence of MS in 45 countries or areas correlates well with the frequencies of DMF teeth among children of school age in those locations (r=0.78, P less than 0.001). The prevalence of MS also correlates well with the percentage of edentulous individuals in certain countries (r=0.99, P less than 0.001). A review of the literature shows that the risk for dental caries is lower among the following groups: the lower socioeconomic classes in the United States of America; Chinese immigrants to England compared with natives; blacks compared with whites; and males compared with females. The dental caries risk is higher during pregnancy and lactation. All these trends have been described for MS as well. It is suggested that dental caries may be a more accurate epidemiological model for MS than poliomyelitis. It is also suggested that MS and dental caries may share certain aetiological factors, two of which may be dietary excess of certain fats, and vitamin D deficiency.” 17

These findings were subsequently supported in a case-control study in Leicestershire, England in the years 1989-1990: “The odds of being a MS case increased multiplicatively by 1.09 (95% CI 1.00, 1.18) for every additional unit of DMFT index of dental caries. This represents an odds ratio of 1.213 or a 21% increase in risk of MS in relation to dental caries in this population. There was no difference between cases and controls in the number of amalgam fillings or in body mercury or lead levels. There was a significant correlation between body mercury levels and the number of teeth filled with amalgam (controls: r = +0.430, P = 0.006, cases: r = +0.596, P = 0.001)”18.

Page last edited: 08 August 2011


  1. Lewis, J. R. Exemptions from military service on account of loss of teeth. Dental Cosmos. 1865; 7 (5): 240-242.
  2. Mills, C. A. Factors Affecting the Incidence of Dental Caries in Population Groups. J Dental Res. 1937; 16417-430.
  3. U.S. Public Health Service, Dental Survey of School Children, Ages 6-14 Years Made in 1933-4 in 268 States. 1936;
  4. East, B. R. Mean Annual Hours of Sunshine and the Incidence of Dental Caries. Am J Public Health Nations Health. 1939 Jul; 29 (7): 777-80.
  5. McBeath, E. W. Zucker, T. F. The Role of vitamin D in the control of dental caries in children. J. Nutrition. 1938; 15 (6): 547-564.
  6. Erpf, S. F. Dental caries and paradental disturbances, II, The seasonable incidence of dental caries. J Am Dent Assoc. 1938; 25681-682.
  7. Dunning, J. M. The influence of latitude and distance from seacoast on dental disease. J Dent Res. 1953 Dec; 32 (6): 811-29.
  8. Grant, W. B. Boucher, B. J. Are Hill's criteria for causality satisfied for vitamin D and periodontal disease?. Dermatoendocrinol. 2010 January/February/March; 2 (1): 30-36.
  9. Hadjimarkos, D. M. Geographic variations of dental caries in Oregon. VII. Caries prevalence among children in the Blue Mountains region. J Pediatr. 1956 Feb; 48 (2): 195-201.
  10. Hadjimarkos, D. M. Storvick, C. A. Geographic variations of dental caries in Oregon: V. Dental caries among school children in the Willamette Valley region. Am J Public Health Nations Health. 1951 Sep; 41 (9): 1052-8.
  11. Hadjimarkos, D. M. Storvick, C. A. Sullivan, J. H. Geographic variations of dental caries in Oregon. III. A consideration of the influence of some environmental factors on the caries experience of native born and reared school children in two regions. Oral Surgery, Oral Medicine, Oral Pathology. 1950 April; 3 (4):
  12. Hall, R. L. Morrow, R. Clarke, J. H. Dental pathology of prehistoric residents of Oregon. Am J Phys Anthropol. 1986 Mar; 69 (3): 325-34.
  13. Powell, R. N. Geographic effects on dental caries prevalence and tooth loss in Australia. Community Dent Oral Epidemiol. 1983 Aug; 11 (4): 242-5.
  14. Pitts, N. B. Boyles, J. Nugent, Z. J. Thomas, N. Pine, C. M. The dental caries experience of 11-year-old children in Great Britain. Surveys coordinated by the British Association for the Study of Community Dentistry in 2004 / 2005. Community Dent Health. 2006 Mar; 23 (1): 44-57.
  15. Grant, W. B. The prevalence of multiple sclerosis in 3 US communities: the role of vitamin D. Prev Chronic Dis. 2010 Jul; 7 (4): A89; author reply A90.
  16. Ascherio, A. Munger, K. L. Simon, K. C. Vitamin D and multiple sclerosis. Lancet Neurol. 2010 Jun; 9 (6): 599-612.
  17. Craelius, W. Comparative epidemiology of multiple sclerosis and dental caries. J Epidemiol Community Health. 1978 Sep; 32 (3): 155-65.
  18. McGrother, C. W. Dugmore, C. Phillips, M. J. Raymond, N. T. Garrick, P. Baird, W. O. Multiple sclerosis, dental caries and fillings: a case-control study. Br Dent J. 1999 Sep 11; 187 (5): 261-4.