“The Silent Causes: Why Some Autopsies Can’t Reveal the Truth”

Need for Autopsy in every death –

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Use of Teeth in ascertaining ages: 

Ascertaining the age of an individual, whether living or dead, is a daunting task in forensic investigations, which over the decades have demonstrating hindrances in achieving. Verifying the age of an immigrant, of refugees with disputed birth records, and in the person having criminal antecedent who is reluctant to reveal his/her age. It is a darndest fact that teeth are the most durable and resilient parts of the skeleton, with their physiologic variations, pathoses and effects of therapy, they usually resist the influence of many factors including the taphonomic process, and disintegrate very slowly.

There are two principal methods, been used for dental age estimation:

• Radiography – a non-invasive method, plays a vital role in forensic dentistry to uncover the hidden facts of premolars, which cannot be determined by means of physical examination. Radiographic evaluation of teeth requires neither tooth extraction or processing.

• Cameriere Method: based on the measurement of the ratio between the length of the projection of the open apices and the length of the tooth axis major (known as the open apices method). Briefly, the method uses the seven left mandibular teeth.

• Bayesian Calibration: a fundamental tool in forensic and legal field where inferences and decisions are made. In this study, a full Bayesian calibration model was developed to make probabilistic inferences about age estimation in a reference sample of 891 periapical X-rays of upper and lower canines belonging to both deceased and living adults.

The ideal pH level in the mouth is slightly acidic to neutral, typically around 6.2 to 7.6, which supports a healthy balance of microorganisms and protects dental tissues. However, when the pH in the mouth drops below 5.5, the environment becomes too acidic, leading to the demineralisation of tooth enamel causing ‘Tooth Decay’.

A recent research suggests that: the mean of total Pulp Area / Tooth Area Ratio (P/T) was highly significant with p value <0.001; signifying that as age increases the P/T ratio decreases. It is note-worthy that a low P-value, meaning a P-value between 0 and 0.49, indicates that it is unlikely that the results of an experiment occurred due to random chance.

Regression equation using combined P/T ratio revealed that the value was 0.24 for all age group with constant age of 66.41 years with the significant p value <0.001.  The P/T ratio of the mandibular canine, post 1st Post Mortem and 2nd Post Mortem did not reveal any statistically significant differences between genders. This could be attributed that these teeth have less attrition or wear leading to less degree of change in the inner morphology of dentin and pulp in both males and females.

Regression analysis of canine and premolar teeth indicated that the P/T ratio regularly decreased with age and ranged from 0.04 to 0.10. Multiple regression analysis, with age as dependent variable and P/T ratio as predictor, yielded a path-breaking formula for age estimation.

Regression equation using combined P/T ratio revealed the value was 0.24 for all age group with the significant p value <0. 001.Regression equation using P/T ratio of individual tooth revealed that the 1st PM the value was 0.47, for canine the value was 0.42 and for 2nd PM the value was 0. 41. The predicted age difference for mandibular canine tooth ranged from 6.83-8.85years, for mandibular 1st PM tooth ranged from 6.55-8.47 years and for mandibular 2nd PM tooth ranged from 6.60-8.76 years.

It is suggested that there are several key factors which could influence the results that are to be taken into consideration. These key factors include:

• individual variability of tooth size,
• variations in patterns of secondary dentin apposition,
• differences in magnification of radiographs and the factors which influence the image quality includes errors in exposure, projection angle, radiation dose, accuracy of patient positioning and tongue position

From the results of the present study, it can be concluded that the radiographic method of using pulp/tooth ratio of mandibular canines and premolars is a useful technique to estimate dental age of an adult individual, as it helps forensic odontologist to develop a profile of a dead individuals as well as serve in determining age in living subjects.

To be continued…………..

Writer Suvro Sanyal

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