This study assessed symmetry of developmental stage of permanent teeth between the left and right side of the jaw, as well as between the maxilla and the mandible using Moorrees and Demirjian methods. These results suggest symmetric development for left and right side in both the maxilla and the mandible while asymmetric development was observed between maxilla and mandible.

Percentage of agreement for individual teeth between the left and right side of the jaw, as well as between the maxilla was slightly higher for Demirjian method compared to Moorrees stages. This reflects more agreements and fewer differences in Demirjian method compared to Moorrees stages and may relate to the fewer number of tooth stages in Demirjian compared with Moorrees.

With weighted kappa values κ > 0.87, both the inter-agreement and intra-agreement can be classified as very good, indicating that the observers were well-calibrated.

Tooth formation is a continuous process and may be classified into stages. Different systems are available for classifying stages of tooth development. They differ with regard to number of stages and presentation and definition of each stage. Some classification systems are defined by changes in tooth and root form, e.g., the method developed by Moorrees, Fanning and Hunt and Demirjian. Therefore, two popular methods are used for this study.

Differences in the eruption of first molars between the right and left sides of the jaw have been identified (Hirano et al. 2009), while no significant difference in the growth rates of bilateral homonymous teeth at different developmental stages was observed (Kuremoto et al. 2022).

In the present study, we found symmetry in developmental stage of permanent teeth among left and right sides of both jaws. This suggests that the results for the left and right sides can be combined. Moreover, contralateral homologous tooth on one side can be used when it is difficult to identify the developmental stage of a tooth on the other side. Homologous refers to corresponding teeth on the left and right sides of the jaw, such as left and right first molars. The findings of no significant differences between left and right sides of both jaws align with previous research, which reported similar symmetry (Garn et al. 1958; Grøn 1962). This reinforces the concept that left and right developmental stages are comparable and can be used interchangeably in forensic and orthodontic evaluations. However, the research expands the understanding of this symmetry by using two well-established staging methods, providing a comprehensive analysis. By employing both the Moorrees and Demirjian methods, we add a new dimension to this established understanding, highlighting the consistency across different scoring systems.

From a clinical perspective, asymmetric development between the maxilla and mandible is expected as mandibular anterior teeth have shorter roots and tend to erupt earlier than the corresponding teeth in the maxilla (Lam and Koudela 2010). This is supported by the radiographic study of Anderson et al. (1976), which found that the mean age of attainment of the maxillary central incisor was 10.6 years, whereas the mandibular central incisor was 9.2 years in males (Anderson et al. 1976). Additionally, mandibular incisors take a shorter time to develop than maxillary incisors and are smaller in all dimensions compared to maxillary incisors (Nelson 2014). The study not only confirms these developmental asymmetries but also provides quantitative analysis using the Moorrees and Demirjian methods, contributing to understanding of these differences.

There is little evidence-based information available, and clinicians and forensic odontologists often assume symmetry in dental development. This study provides the necessary evidence, showing that the observed symmetry between the left and right sides in both jaws supports the use of contralateral teeth as reliable references in clinical and forensic evaluations. This finding enhances the applicability of dental age estimation methods. Furthermore, the significant asymmetry between maxillary and mandibular teeth underscores the need for differential analysis when assessing dental development stages, which has practical implications for orthodontic planning and forensic casework.

One limitation of the study is the demographic origin of the sample, primarily comprising individuals of European ancestry from the Maxwell Museum’s orthodontic collection. This collection includes self-reported demographic data where individuals could select multiple ethnic or geographic categories; however, the sample predominantly represents European ancestry, a factor that may limit the applicability of the findings to broader populations. Additional ethnic or geographic categories within this collection include American Indian or Alaskan Native, Asian American, Black or African American, Hispanic or Latino, and Native Hawaiian or other Pacific Islander. While this lack of diversity may limit the applicability of the findings to broader populations, it is important to consider the relevance of these demographic factors in modern society. The critical need for inclusive and diverse representation in clinical research has been emphasised to ensure that findings are applicable to all demographic groups (Flanagin et al. 2021). As the global population becomes increasingly diverse, understanding and addressing health disparities that may exist across different ethnic and geographic groups is essential. In light of these considerations, future studies should aim to include more diverse samples to enhance the generalisability of findings and ensure their relevance to modern society.

Another limitation of this study is the small sample size for each age group resulting from the limited availability of high-quality panoramic radiographs. Although the findings demonstrate statistically significant differences, a larger sample size would provide improved statistical power, enabling more robust subgroup analyses and enhancing the generalizability of the study.

The radiographs which were obtained from the online open access resource of the Maxwell Museum of Anthropology’s orthodontic collection, Albuquerque, USA, were originally wet film which have been digitised so a loss of quality is to be expected. Therefore, additional methods such as intraoral examination or oblique X-rays are needed to complement and confirm the findings of this study.

Future research should aim to address these limitations by including a larger and more diverse sample, to enhance the generalisability of the findings. Furthermore, using multiple sources of radiographic data could improve the robustness and accuracy of the results.

Assessing symmetry of developmental stage of permanent teeth between the left and right side of the jaw offers several key advantages including implication for forensic age estimation, the correlation between chronological and dental age and sequence of tooth eruption between left and right side of the jaws. Moreover, the extent of asymmetric development between the left and right side of the arch can indicate the presence of some problem, i.e. pathological lesion, such as cysts or tumors, which need to be determined and treated accordingly.

This study provides evidence of symmetry in the developmental stages of permanent teeth between the left and right sides of both jaws. These findings have practical implications, such as in the assessment of dental maturity where methods require seven mandibular teeth; if one tooth is unclear or missing, the contralateral tooth can be used. In forensic age estimation, reference data from one side of the mandible can be applied when only the other side is available. Additionally, fragments of the maxilla can be used to estimate age based on mandibular reference data.

The observed differences between maxillary and mandibular teeth contribute to a deeper understanding of dental growth patterns, which can inform clinical practices and forensic investigations, ultimately benefiting dental professionals and organizations.