Deciduous or temporary dentition comprise the teeth present in an infant or toddler. These are also known as primary teeth. Deciduous teeth erupt during early postnatal life and shed after a particular time during the life. These teeth are then replaced by permanent teeth which comprise the dentition of a mature individual and do not shed or if shed, are not replaced.
The time of eruption and shedding of these two sets of teeth can be used to estimate the age of an individual by examining his dentition as this transition occurs during particular time intervals of the life. However, the age estimated by this method may not be accurate as the time of eruption and shedding of teeth in humans varies a lot with race, gender, heredity or dental abnormalities. Let us look at the eruption and shedding times of the two sets of dentition in the tables below.
1.1 Eruption of Deciduous teeth
| Upper jaw | Eruption | Shedding |
| Central incisor | 8-11 months | 6-7 years |
| Lateral incisor | 9-13 months | 7-8 years |
| Canine | 17-22 months | 10-12 years |
| First molar | 14-16 months | 9-11 years |
| Second molar | 21-32 months | 10-12 years |
| Lower jaw | Eruption | Shedding |
| Central incisor | 6-10 months | 6-7 years |
| Lateral incisor | 8-13 months | 7-8 years |
| Canine | 17-22 months | 9-12 years |
| First molar | 13-16 months | 9-11 years |
| Second molar | 20-32 months | 10-12 years |
Table 1 showing estimate time of eruption and shedding of deciduous teeth in humans.
1.2 Eruption of Permanent teeth
| Teeth | Eruption (Upper jaw) | Eruption (Lower jaw) |
| Central incisor | 6-9 years | 6-9 years |
| Lateral incisor | 8-10 years | 7-9 years |
| Canine | 10-12 years | 10-12 years |
| First premolar | 9.5-11 years | 9-11 years |
| Second premolar | 10-12 years | 10-12 years |
| First molar | 5-7 years | 6-8 years |
| Second molar | 12-14 years | 12-14 years |
| Third molar | 17-24 years | 17-24 years |
Table 2 showing estimate time of eruption of permanent teeth in humans.
Gustafson’s method
Till now we have studied age estimation from teeth in terms of dentition, but it is not necessary that the entire skull is found at the crime scene. With time, criminal minds have advanced and have known the fact that how science has developed various methods of identification of corpses even from minute details. In the present time, criminals tend to destroy every single detail that could lead to the identification of corpses and ultimately their conviction.
So, methods like burning the corpses or dismemberment of various body parts are the methods most likely adopted by criminals that challenge the scientific brains. In such cases, forensic scientists need to work at their best. Even a single tooth found at the scene of crime can be used to estimate the age, yes, a single tooth, how? Let us study this in detail:
Gustafson devised a method of age estimation on the basis of regressive changes that occur due to wear and tear of teeth. He developed a regression equation on the basis of his research which can be used to estimate the age from teeth. In this method, the morphological factors of a tooth that are taken into account can be divided into 6 categories as under and each factor has been allotted a score ranging from 0-3 based on observed condition of the tooth as mentioned below:
- Amount of attrition on incisal or occlusal surface (A): It is scored as under:
| Score | Condition |
| A0 | No attrition |
| A1 | Attrition limited to enamel level |
| A2 | Attrition limited to dentin level |
| A3 | Attrition up to pulp cavity |
- Secondary dentine deposition (S): It is scored as under:
| Score | Condition |
| S0 | No secondary dentin formation |
| S1 | Secondary dentin up to upper part of pulp cavity |
| S2 | Secondary dentin up to 2/3rd part of pulp cavity |
| S3 | Diffuse calcification of entire pulp cavity |
- Periodontal diseases (P): It is scored as under:
| Score | Condition |
| P0 | No obvious periodontal disease |
| P1 | Beginning of periodontal disease but no bone loss |
| P2 | Periodontal disease more than 1/3rd of the root |
| P3 | Periodontal disease more than 2/3rd of the root |
- Cementum apposition (C): It is scored as under:
| Score | Condition |
| C0 | Normal cementum |
| C1 | Thickness of cementum more normal |
| C2 | Abnormal thickness of cementum near the apex of the root |
| C3 | Generalized abnormal thickness of the cementum throughout the apex of the root |
- Root resorption at apex (R): It is scored as under:
| Score | Condition |
| R0 | No resorption |
| R1 | Spotted resorption |
| R2 | Resorption limited to cementum |
| R3 | Extensive resorption of the cementum and dentin both |
- Translucency of root (T): It is scored as under:
| Score | Condition |
| T0 | No translucency |
| T1 | Beginning of translucency |
| T2 | Translucency more than 1/3rd of apical root |
| T3 | Translucency more than 2/3rd of the apical root |
Once all the six observable factors of a tooth are allotted a particular score, all the scores are summed together to get a new value. For example- X = (A1+S2+P0+C3+R2+T3).
This new value i.e. ‘X’ is put in the regression formula developed by Gustafson and the age of person can be determined. The regression formula for the same is:
AGE = 11.43 + 4.56 (X)
The average error in the age estimated by this method is ±3.63.
*All the data of estimate time of epiphyseal fusion, fusion of joints, eruption and shedding of teeth etc. are obtained by comparative analysis of researches conducted across various parts of the world. The data provided is not universal and is a subject to vary.
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