The application of computerized tomography (CT) to the dental ageing of children and adolescents

Abstract

Introduction

Following a mass disaster, the aim of the Disaster Victim Identification process is to establish the identity of the victims. The ageing screening process on victims in Victoria may now be complemented with the use of computerized tomography (CT), where previously any dental ageing analysis was performed using conventional radiographs.

The aim of this study was to assess the accuracy of age estimation using the dental ageing method proposed by Moorrees, Fanning and Hunt (MFH) using CT images. Intra- and inter-rater variability between two raters, one experienced and one inexperienced, was also assessed.

Materials and methods

The two raters were blinded to the ages of 96 deceased Australian children aged up to 15 years. Using three-dimensional (3D) shaded surface displays (SSD) and reformatted CT images, the age was first estimated based on prior experience alone, followed at a later date by the age estimation utilizing the MFH method. These estimates were then compared to the known chronological age. The results were statistically analyzed in a one-sample t-test, using the mean log-ratio of the estimated age to the chronological age.

Results

Our findings show that the experienced rater was more accurate in age estimation than the less experienced when using prior experience (p < 0.0001). The use of reformatted CT images to perform an ageing estimate using the MFH method was found to systematically underestimate the chronological age by 10% by both raters (p = 0.784). There was no significant difference between the two raters. Intra-rater reliability was high (p = 0.135).

Conclusions

CT can provide accurate estimates of dental ages. Prior experience with dental ageing and/or CT improves the accuracy. However, with the use of validated ageing charts, inexperienced raters can also achieve accurate age estimates using CT images.

Introduction

The identification of deceased persons by dental means is one of the most rapid and useful methods utilized by the investigating authorities following mass disasters [1]. The estimation of the chronological age of a deceased child, even when given as a range of ages, can be an essential factor in the subsequent identification of that child, enabling the investigating authorities to reduce the range of possible matches prior to the implementation of more expensive and time-consuming identification techniques.

Age estimation requires a thorough understanding of the chronological development of the dentition and research into it has undergone some modification over time. Different manners of showing the dental development have been utilized: diagrams [2], charts [3] and the assignation of formative stages [4]. Moorrees, Fanning and Hunt (MFH) divided the formation of teeth into 14 stages. They produced charts showing the mean age of attainment of each of the stages for each of the prescribed teeth, permanent and deciduous, from which the age is estimated using whatever teeth are visible [5], [6].

The abovementioned method relied on the use of intra-oral and panoramic radiographs which can be difficult to take in the deceased for a variety of reasons—rigor mortis, trauma to the head and lack of access to equipment.

The recent introduction of computerized tomography (CT) among a few forensic institutes around the world has facilitated obtaining images of deceased persons for post-mortem examinations. At the Victorian Institute of Forensic Medicine (VIFM) in Melbourne, Australia, CT imaging is routinely used as part of every post-mortem examination, including the dental examination where CT has a number of advantages over intra-oral radiography. It does not require placing image receptors into the mouth, nor does it require manipulation of the head in order to align the X-ray beam in the appropriate direction, even after severe head trauma.

CT also has the capability of producing cross-sectional and images in three-dimensions (3D) of an individual in a variety of ways. In the mortuary setting, it enables the emerged teeth and the skeletal system of the deceased to be viewed through shaded surface display (SSD) reconstruction of the original axial datasets. Axial CT images may also be reformatted using a curved multiplanar reconstruction (MPR) to produce images that resemble conventional panoramic dental radiographs.

The use of CT has not yet been tested in the estimation of children's ages.

The aims of this study were threefold: (1) to determine if the use of reformatted CT images was clinically useful for the estimation of chronological age in a cohort of deceased Australian children and adolescents using the dental ageing method of MFH; (2) to determine if prior dental experience affects the accuracy of age estimation using the above method; and (3) to determine the intra- and inter-rater variability in our setting.