Changes in mandibular cortical width measurements with age in men and women

Automated software was used to measure the mandibular cortical width in a large sample of dental radiographs. We determined that cortical thinning normally starts in women at age 42.5 years and accelerates thereafter. We can estimate population referral rates and thus enable cost benefit analyses for osteoporosis detection by dentists.

Previous studies have shown that the mandibular cortical width is significantly correlated with the bone mineral density at sites which may undergo osteoporotic fracture, e.g. hip. Mandibular cortical width can be determined automatically from dental panoramic radiographs that dentists frequently request, using appropriate software. We study the distribution of cortical width given age to predict those patients requiring further investigation for osteoporosis.

The mandibular cortical width was measured in 4,949 dental panoramic tomograms, in patients aged 15-94 years. The inferior and superior cortical edges were detected automatically using a global active shape model image search, followed by an active appearance model search. Nonparametric statistical analysis and nonlinear piecewise linear/quadratic regression were used to analyse the data.

For females, the mean cortical width had a linear increase before the age of 17 years, a period of no change (estimate = 3.25 mm, se = 0.01) until the age of 42.5 years, followed by a quadratic decrease with age. For males, it had a linear increase before the age of 19 years, a constant value (estimate = 0.37 mm, se = 0.01) until the age of 36 years and then a slow linear decrease. The rate of decrease in mean cortical width goes from 0.049 to 0.105 standard deviations per year in the 60-80-year-old female age group, in line with published bone mineral density T-score reductions.

The pattern of decrease in mandibular cortical width with age was similar to the known pattern of bone loss from the hip, accelerating in women after the age of 42.5 years.