DENTAL RADIOLOGY: AN ADJUNCTIVE AID IN AGE ESTIMATION

The concept of using radiographic methods for age estimation has kindled so much interest in the field of forensic dentistry in past few decades. Aim and Objectives: To evaluate the different dental radiographic methods for age estimation and their significance in the field of forensic dentistry. Methodology:64articles were collected after an extensive literature review. Literature survey of these articles was done.Conclusion:Radiographic methods play an indispensible role in age estimation specifically in living persons because of their non-invasive and non-destructive nature. This review paper focus on different radiographic methods and new developments available for radiological dental age estimation and their effective aid in identification and crime investigation.


INTRODUCTION
In the field of forensic anthropology and forensic dentistry, identification of unknown becomes an important question to answer. Photographs, identity cards and some advance methods based on DNA, biometrics and dental patterns are some of the tools that can be used for identification 1  Among the biological parameters of individualization of human remains, both sex and age are essential [4] . Age estimation plays a significant role in various criminal cases as well as to clarify civil liability and social issues and also in f o r e n s i c m e d i c i n e , p e d i a t r i c endocrinology, clinical dentistry, and a r c h a e o l o g y [ 5 , 6 , 7 , 8 ] . F o r e n s i c A g e Estimation (FAE) is defined as "Expertise in forensic medicine which aims to define in the most accurate way the chronological age of person of an unknown age involved in judicial or legal proceedings." [9] Although various methods for age estimation exists in literature but a universal system has not been achieved [10,11,12,13] . physiological and degenerative changes in dental tissues [14] . Application of multiple age indicators at the same time will provide more accurate results. But when these methods are analyzed separately, dental age estimation techniques offer more accurate results than other methods. [15,16,17,18]

IMPORTANCE OF TEETH AS AGE INDICATOR
Development pattern of teeth is very predictable in nature because they are tightly constrained by genetics [19,20,21] .
They are preserved for a longer period of time and thus used for more accurate age estimation. Teeth consist of enamel (outermost covering of crown), dentin and cementum (outermost covering of root) which makes it resistant to decomposition [22,23,24,25] . Morphological methods are subjective in nature and predict a wider range of age.

METHODS
Biochemical and histological methods are destructive methods as these methods require teeth to be extracted that cannot be possible for every case specially in living persons. [28] . This makes usage of dental radiographs, a more practical and relevant approach for age estimation in living individuals as it is no-destructive in nature [29] .

TYPES OF DENTAL RADIOGRAPHS
Various types of radiographs can be

FIRST PHASE
Age assessment in neonates: as the tooth germs starts developing in the sixteenth week of intrauterine life, they appear on radiographs as radiolucent areas. After twenty-sixth week, anterior teeth of foetus showed advanced mineralization [37,38] . Karus and Jordan categorized the mineralization degree of primary teeth into 10 stages [37,38] .

Age assessment in Children and
Adolescents: methods used in children a n d a d o l e s c e n t s a r e b a s e d o n radiographic analysis of various development stages of teeth and eruption in the oral [39] . Mineralization process of permanent teeth is divided into various stages by different researchers for the purpose of age estimation such as Schour a n d M a s s e l e r p u b l i s h e d s o m e development charts [39] . Moorees, Fanning a n d H u n t c l a s s i f i e d t h e t o o t h development into fourteen stages [40] .
Demirjian, Goldstein and Tanner described tooth development into eight stages [41,42,43,44] . Chaillet and Demerjian have derived a modification in original method and divided the calcification of teeth into ten stage (0-9) [45] . Nolla conducted another study to overcome the limitations of previous studies and divided the mineralization levels of teeth into ten stages. This method can be applied even in absence of third molar . Harris described the development of the mesial root of the third molar in five stages using dental radiographs. [48,49,50] .
Changes in tooth-pulp area/volume is also proved a significant tool for age estimation. Ikada and his associates studied the correlation between the chronological age and coronal tooth pulp index.Formula given as, Where, CPCH is coronal pulp cavity height and CL is coronal length in m m [51,52] . K v a a l c a l c u l a t e d s o m e measurements on intraoral radiographs of six mandibular and maxillary teeth as | 91 pulp, tooth, root lengths and their ratios at three different level [53]. In a study conducted by Robert Cameriere, age estimation was done using pulp tooth area ratios in 100 individuals aged between 18 to 72 years in right maxillary canines using orthopantamographs (OPG) [54,55,56,57,58] . Further studies were done by Jeevan, Zaher, Babshet and Acharya using this method.All these studies showed significant results and proved that change in tooth-pulp area can be used for determining the age of individual [59,60,61] .

A D V A N C E D R A D I O G R A P H I C
TECHNIQUES [62] Cone beam computed tomography (CBCT) is a non-invasive developing technique based on pulp/tooth volume assessment used for age estimation and gender determination. It is designed to reduce dose of radiation and to provide high resolution. Singaraju also has done study on age estimation using pulp/tooth area ratio in right maxillary canines and monoradicular teeth [63,64] .

CONCLUSIONS
As lot of research had been done in area of age estimation, numerous radiographic methods are available in literature for assessing dental age. But there is no study till now describing which digitized parameters are best suited for age determination in different age groups. More than one method of age estimation should be used to get a more effective and reproducible age range. To achieve more accurate age estimation, there is need for a corroborative population specific study with larger s a m p l e s o f v a r y i n g a g e groups.Development of this population specific age estimation tool may be significant to forensic odontologists and anthropologists in various civil and crime cases.