Malocclusion is a kind of craniomaxillofacial complex deformity caused by heredity, environment, bad habits, trauma, inflammation, tumor and aging. Notably, the last comprehensive national prevalence data on malocclusion in China, which encompassed a significant sample size, dates back over two decades. Given the evolving nature of these epidemiological metrics, such as prevalence rates, it is imperative to update our understanding. Consequently, there is an urgent need for China to undertake a unified, standardized epidemiological survey of malocclusion with a substantial sample size to ensure accurate and timely data collection.

With the improvement of our country's living and cultural level, orthodontic treatment for malocclusion has emerged as a critical need that significantly impacts individuals' physical and mental wellbeing, as well as their social life in contemporary society. To obtain the prevalence rate, demand index and risk factor analysis of malocclusion in China serves as a fundamental prerequisite for effective diagnosis, identifying the optimal treatment window, and devising tailored treatment plans.

The purpose of this study is as follows:

1. Obtaining epidemiological data such as the prevalence rate of malocclusion is the cornerstone of prevention and treatment of malocclusion, and is also the prerequisite of carrying out a series of studies;
2. Establishing China's orthodontic treatment demand index offers vital support for the advancement of orthodontics and oral healthcare.;
3. Updating and enhancing X-ray head image measurement normal reference value provides a more scientific and objective foundation for orthodontic planning, improves the level of diagnosis and treatment, and fosters the development of related disciplines.

The implementation of this project will not only foster an improvement in the overall oral health of the populace but also establish a scientific foundation for oral medicine research and the development of prevention and treatment strategies.

Inclusion Criteria:

1. Individuals with all genders;
2. Individuals with good general health;
3. Individuals with no history of orthodontic treatment or other maxillofacial surgical interventions;
4. Individuals who agree to and are willing to sign the informed consent form.

Exclusion Criteria:

1. Individuals diagnosed with genetic or systemic disorders;
2. Individuals with a recent (within the past 3 months) history of maxillofacial trauma;
3. Individuals who are incapable of undergoing oral examinations or completing the necessary questionnaires.

The study included four age groups: students aged 4-6 years (senior grade of kindergarten),9-11 years (fourth grade in primary school),13-15 years (eighth grade),and 17-20 years (freshman in college).