According to a new study from Sweden, the method of age determination based on the assessment of mandibular third molar root formation appears to be completely unreliable.
Determining a person's age plays a key role in various medical, legal, and anthropological contexts. Traditionally, the stage of development of the third molars of the lower jaw, in particular Demirjian's H-stage, served as a tool for such assessments. Researchers in Sweden conducted a systematic review to examine the reliability of this dental method from a statistical, clinical, technical and ethical perspective and found an overwhelming lack of scientific evidence for its reliability as an age estimate.
In 1973, Demirjian developed a map, later updated in 1976, of eight stages of tooth formation and development (A to H). Initially, the method was applied to seven permanent teeth in the lower jaw, and later an eighth permanent tooth, the third molar, was included. This tooth is particularly important in the forensic age assessment of older adolescents and young adults.
Demirjian's stages of tooth formation are subdivided using panoramic radiographs, and correct patient positioning is critical to obtaining quality images. These radiographs allow dentists to classify the developmental stage of the third molar using reference datasets to estimate chronological age. Stages G and H deserve special attention. In stage G, the root apices remain open, while in stage H they close, marking the full formation of the tooth. While factors such as gender, ethnicity, and genetics influence tooth formation, environmental stresses usually have a minimal effect, and diet, high temperature episodes, and certain medications can affect tooth morphogenesis.
Researchers from the University of Malmö and the Swedish Agency for Health Technology and Human Services Evaluation attempted to investigate the correlation between a fully mature mandibular third molar using Demirjian's method and chronological age. The main issue was the reliability of using Demirjian's H-stage to determine whether someone was 18 years of age.
The review included 15 studies that spanned 13 countries and included participants aged 3 to 27 years. The study found that in certain participants with a third mandibular molar at age 18, H-stage results ranged from 0% to 22% in men and 0% to 16% in women. The review was unable to definitively link Demirjian's H stage of mandibular third molar development to chronological age, indicating that it is unreliable to use this method to determine whether younger or older than 18 years of age. Clinically, the rate of development of third molars has been found to vary across populations, and their presence is inconsistent due to congenital absence or other dental problems.
From a technical point of view, image quality is critical, but radiographs can contain undetectable artifacts that affect reliability. Advanced methods such as machine learning could revolutionize age estimation in the future, potentially surpassing Demirjian's traditional manual method.
From an ethical point of view, the use of third molar maturity for age estimation presents challenges regarding gaps in knowledge, consistency, and potential long-term implications. The authors suggested that future studies, with better researcher training and higher quality radiographs, would provide more accurate results.