Estimation of age from development and eruption of teeth.

The developing dentition is used to assess maturity and estimate the age in many disciplines including anthropology, archeology, forensic science, pediatric dentistry and orthodontics. There is evidence that dental development is less effected than skeletal development by malnutrition and hormonal disorders. There are two methods of dental age assessment, radiographically and by clinically visualization of eruption of teeth. The clinical method to assess dental age is based on the emergence of teeth in the mouth. This method is more suitable since it does not require any special equipment, expertise and is more economical. Tooth formation is the best choice for estimating the age as variations are less as compared to other development factors. Eruption of teeth is one of the changes observed easily among the various dynamic changes that occur from the formation of teeth to the final shedding of teeth. The times of eruption of teeth are fairly constant and this can be made use of in ascertaining the average age of eruption of the tooth. Assessment of age of an individual by examination of teeth is one of the accepted methods of age determination.

Introduction

The estimation of age is an important and is commonly carried in medico legal area. Assessment of age is often required while administering justice to an individual involved in the civil and the criminal litigation.[1] Teeth are known to aid in personal identification and age estimation as they are highly durable and resist putrefaction, fire, chemicals etc.[2] Dental age estimation in the living is mostly based upon non-invasive methods, which evaluate the timing and sequence of defined growth stages of the developing dentition and the sequence or modification of traits in the mature dentition and the surrounding tissues.[3] Eruption of teeth is one of the changes observed easily among the various dynamic changes that occur from the formation of teeth to the final shedding of teeth. The times of eruption of teeth are fairly constant and assessment of age of an individual by examination of teeth is one of the accepted methods of age determination. This fact can be made use of in ascertaining the average age of eruption of the tooth.[1]

Discussion

History

The use of teeth for determining someone's age has its origin 170 years ago when tooth eruption was first used for dental age estimation in connection with child labor. In response to the need for age estimation of factory children who were not allowed to be employed under the age of nine and with a restricted working time between 9 years and 12 years of age.[4]

In ancient times, age estimations of living adolescents were considered important. According to records in Ancient Rome adolescents were judged to be fit for service, as soon as the second molars had erupted completely.[5] It was mainly dentists who had to carry out age estimations.[6]

Earlier Charts and tables were used for the assessment of age during development period with the use of formation, eruption, and calcification of teeth. For this purpose, table of Krenfild and Logan was further modified by Kronfild and Schour (1939) is commonly used which has been accepted as standard for many years.[78] Gorden et al., described that during infancy and childhood, a fairly accurate estimate of age can be made from the study of teeth.[9] Gonzales et al.[10] described that the teeth may give, reliable information as to age in childhood and youth. Beyond adult life, the changes are too uncertain to be of value. Scot stated that if the third molars are fully erupted, it indicates that the age of an individual is above 17 years, and on X-ray examination if the root formation is not complete, one can definitely conclude than the person was probably less than 25 years of age.[11]

Most of the earlier studies in European populations found differences in the pattern of deciduous tooth emergence in both different genders. These studies have showed that the anterior dentition in males is developing early relative to the female dentition and the pattern reverses so that females lead males in the emergence of the posterior deciduous dentition. Little is known about sex differences in the dental development and the emergence of non-European populations. The results supported that the pattern of developmental cross-over observed in other populations.[12] They concluded that there is a little evidence to support the hypothesis of Tanguay et al.[13]

Camps has described that after birth and during a child is developing, it is possible to arrive at a close estimation of age by the presence of the deciduous dentition at its stages of eruption and also the mixed dentition period and its stages of eruption of the permanent teeth and loss of deciduous teeth. He also pointed that state of eruption only gives an indication of age since eruption dates are subject to wide variations.[14] Biggerstaff found that forensic dentist can estimate the age of a person by noting developing dentition. According to him, systemic observations can provide accurate age estimation depending upon the criteria used.[15] Tedeschi et al., have described that from birth to 6 months of life, accurate age estimation can be based on the mineralization of the deciduous crowns and from then up to 13 months of age, estimation may be determined by the state of eruption.[16]

However, the socioeconomic status of the child could also play a role. Studies show that underprivileged children show comparative retarded eruption relative to their ethnic counterparts from higher socioeconomic status.[1718] This observed difference have been attributed to the effect of nutrition as studies point to earlier eruption times in well-nourished children.[19] Eruption of the deciduous teeth in moderate to severely malnourished children showed 5-29% increase in times of emergence.[19] The effect of nutrition on the time of eruption of the deciduous teeth can be further corroborated by studies, which try to link the effect of breastfeeding on the timing of eruption. This is contrary to the observation by Holman and Yamaguchi[19] who noted a selective effect of nutritional status on the timing of tooth eruption-poor nutrition was associated with delayed emergence, while medium nutritional status showed significant delay in the emergence of incisors and canines of the maxilla and all five teeth in the mandible. They also noted a delay in the emergence of the upper incisors and accelerated emergence of the upper second molar in children not breast-fed in Japan. Partial breastfeeding had no observed effect on tooth eruption.[19]

Several biological factors have been associated with the timing of maturation. Since the development of teeth occurs during the prenatal period, it is appropriate to hypothesize that a shorter postnatal development may influence the development of deciduous dentition. It has been shown that dental development, dental eruption and tooth size may be delayed or reduced in low birth-weight (LBW) and prematurely born children.[20212223]

A longitudinal study of dental development by Fearne and Brook[20] in a group of LBW children was carried out to determine the tooth-crown size of primary molars and canines. The findings were compared to normal birth-weight (NBW) controls. Primary canines and molars were smaller in the LBW than the controls, with the significance values for the mesiodistal dimension of maxillary and mandibular canine compared to a non-significant difference for the buccolingual dimension of mandibular first primary molar. Within the LBW group, there was a positive correlation between birth weight and mesiodistal tooth size. Small primary tooth size in LBW children may be influenced by both genetic and environmental factors. The shorter prenatal growth period and poor perinatal and early postnatal development may influence the developing deciduous dentition.

Harris et al.[21] found that the development of early forming teeth (permanent incisors and first 20 molars) was significantly delayed in LBW children and individuals with the poorest height-forage had the greatest delay in tooth formation, but only teeth undergoing rapid differentiation neonatally were systematically affected.

Seow and Wan,[22] compared the dimensions of the primary incisors from pre-term children and full-term controls. The results showed that there was a dose-response effect of birthweight on the tooth size. The very-low-birthweight teeth showed the smallest dimensions, the NBW controls the largest, and the low-birthweight teeth intermediate dimensions. They hypothesized that primary incisors from children prematurely born with very LBW will have smaller dimensions compared with teeth from full-term children with NBW.

Helm and Prydso recorded permanent emergence of mandibular third molar at an early age of 14 years in 235 Danish Medieval skulls, 52 of whom were in various stages of mixed dentition. They argued that assessment of age at death could be made fairly accurately for the age group 5 to 30 years.[24]

Kumar and Sridhar[1] studied a total of 1008 individuals in between 5 years –and 14 years of age residing in Tirupati, Andra Pradesh. This study was community based on eruption times of permanent teeth to establish age of the individual. The median age of the eruption was computed based on the concept of “Ex” which is defined as the age at which specified percent of individuals shows eruption of a given permanent tooth. The median age “E50” was computed by transforming of percentages to probits and plotting a graph between age and probits. The-individual's age can be computed according to E50 value of permanent tooth, which erupted last. Given individuals probability being above or below the assessed age can be estimated by referring to graph and probit transformation table.

Kaul et al.[25] studied deciduous teeth emergence of 312 children aged 4 months to 31 months with Punjabi parenthood. For calculating medium age of tooth emergence, they used probit analysis. They found earlier tooth emergence in females than their male counterparts. In comparison with other population, it was found that in general, mean number of emerged teeth in Punjabi children is more at most ages and with lower medium age of eruption for most teeth. Variability in the eruption time was highest in 16-17 and 20-21 months. Thus, their study suggests that the number of teeth can be used as a parameter for estimation of age.

Foti et al.[26] studied for age determination both in living and dead children with the help of linear regression. The equation can be applied based on the number of erupted teeth and tooth germs detected during the clinical examination and radiograph. This equation helps in age estimation until 20 years of age.

Summary and Conclusion

The dental system is an integral part of the human body, its growth and development can be studied in parallel with other physiological maturity indicators such as bone age, menarche and height.[27] Several authors have shown that dental parameters are more suitable for age estimation in children because the variability is lower since calcification rates of teeth are more controlled by genes than by environmental factors. Rate of formation of the permanent teeth is not affected by premature loss of the primary teeth. Gingival emergence also called tooth eruption represents only one stage in the continuous process of dental eruption.[28]

Many studies have concluded that tooth formation is a more reliable indicator of dental maturity than gingival emergence or eruption.[293031] Tooth eruption is mostly influenced by environmental factors such as available space in the dental arch, extraction of primary teeth, teeth tipping or impaction of teeth. Until quite recently, clinical eruption has been the only criterion used for dental maturity or dental age.[28] The Demirjian scoring system based on the developmental stages of teeth is more useful since the tooth development is less influenced by environmental factors.[29] Tooth development shows less variability than other developmental features and also low variability in relation to chronological age.[32] Hortz observed a greater degree of association between dental age and chronological age than between dental and skeletal age.[33] The application of clinical emergence as an indicator of maturity has been much debated.