Forensic Dentistry, Second Edition

(Barré) #1

age estimation from oral and dental structures 283


rings. This new emphasis tends to overshadow simply measuring the
thickness of enamel.^10 Gustafson,^92 Johanson,^93 Solheim,^108 and several
others have documented a significant positive relationship between
cementum thickness and age (but with appreciable inaccuracy). This
method might be of some use when the tooth cannot be used to count
annulations, though one needs to control for differences among
tooth types. Researchers have also found systematic differences
when using impacted teeth (cementum is thicker^92 ) or periodontally
involved teeth (cementum is thicker^109 ). Johanson (p. 52) claimed that
“ extensive attrition is always followed by extensive increase in thick-
ness of the cementum.”^110


  1. Root resorption. E x ter na l apic a l root resor pt ion (E A R R) occ a siona l ly is
    seen to be age progressive. More accurately, t he incidence of resorption
    is somewhat more common in older-aged groups in cross-sectional
    studies. Woods et al.^111 found only a few cases of EARR (less than 5%)
    in contemporary American adults who had not experienced orthodon-
    tic treatment, and these cases characteristically are the result of com-
    promised dentitions (missing teeth, periodontal involvement) that led
    to lack of tooth support.^112 This perspective is in concert with Maples’
    1978 findings that root resorption is the least dependable predictor of
    t hose suggested by Gustafson. In modern popu lations, a ver y common
    cause of EARR is orthodontic treatment.^113

  2. Root transparency. Root transparency is due to the age-progressive
    occlusion of dentin tubules leading to sclerotic dentin. This change
    can occur in the crown and root of a tooth, but changes in the crown
    are in consequence to attrition, trauma, caries, and other noxious
    stimuli.93,100 Root transparency commences in the apical region,
    progressing coronally with age.


Various researchers have adapted and refined Gustafson’s method.114 –117
In contrast to his considerable biological and clinical expertise, Gustafson’s
method failed statistically. He assumed that all six of the parameters could
be visually graded on a four-step scale. This assumed that (1) these four
(unequally spaced) ordinal stages informatively reflect the trait distributions;
(2) all six parameters are equally effective at estimating age, so they can just be
added together; (3) the rates of change are equivalent among all of the param-
eters, so they can just be added together; and (4) the imprecision ( variability
of true and predicted ages) is the same for all parameters, so the variances
can be assumed to be equal. Gustafson’s scoring method also assumes that
the six pieces of age information are statistically independent, which is far
from true. These various shortcomings were overcome in sub sequent studies
using multiple linear regression methods and similar statistical techniques
that more appropriately account for the nature of the data.92 ,114

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