Tooth Development Stages [TDS01]

Choice of Tooth Development Stages (TDS)


This issue is one of the most contentious and difficult to reconcile within the field of Dental Age Estimation. Intuitively, it is reasonable to infer that a large number of TDS will provide a more sensitive estimate of a subject’s age whilst a small number stages will be less sensitive. That is to say more stages results in more accurate estimates.  There is no evidence to support this belief.

The number of TDSs is an important but little explored choice.  The number varies from 4 to 21.

1.  Four Stages        (Gustafson and Koch 1974).

2.  Five Stages         (Harris and Nortje 1984).

3.  Six   Stages         (Sarnat et al 2003).

4.  Seven  Stages     (Kullman et al 1992).

5.  Eight  Stages with one as tooth germ (Liliequist and Lundberg 1971).

6.  Eight Stages       (Demirjian et al 1973).  This is the most commonly used.

7.  Ten Stages modified from Demirjian et al 1973   (Solari and Abramovitch 2001).

8.  Ten Stages without detailed descriptions of radiological morphology (Nolla 1960).

9.  Ten Stages based on Demirjian’s radiographic criteria (Acharya 2010).

10. Twelve Stages (Haavikko 1970).

11.  Twelve Stages (Harris and McKee 1990)

13.  Fourteen Stages (Moorrees et al 1963)

14. Twenty Stage (Maheptimab 2009).


It is clear from this limited survey that there is considerable divergence of opinion about the appropriate number of TSDs required for reliable Dental Age Assessment. What is clear that is that at the time of publication none of the originators of the system of TDS recommended by them thought it appropriate to validate the system of age assessment using their own TDS classification by estimating the age of a group of subjects of known age not forming part of the RDS sample that the authors used, i.e. a wholly independent validation sample. The system of DAA devised in the UK has done this by focusing on specific age thresholds and then estimating the age of the study group around the specific age threshold using CA as the Gold Standard.

This has been carried out:

i. at the age of criminal responsibility which is 10 years of age in the UK (Yadava et al 2010),

ii.  the age of statutory rape which in the UK is 13 years old (Chudasama et al 2012),

iii. the age of consent for sexual intercourse which is 16 years of age (Mitchel et al 2009 [4]).


The underlying belief is that that a large number of TSDs will provide greater accuracy as the interval in years between the stages is smaller therefore correct identification of the TDS will lead to a more accurate Age Estimation. This approach fails when the reproducibility of the TDS assessments is considered. The assumed gain in accuracy is lost when the errors in TDS assessment lead to an increased (or decreased) age estimate. The Gold Standard test is to compare the estimated ages using a different number of age assessment systems.

A recent, but as yet unpublished, study (Parekh and Roberts 2014) shows no difference between the estimated age of 50 females and 50 males when the 8 Stage and 12 Stage systems are used.

[[Put some tabular data here PLUS the Reference]]


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Graham Roberts ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~