# Gender- and age-dependent prevalence of malocclusions requiring orthodontic treatment according to the KIG classification. A cross-sectional study over a 20-year-period from the district of Viersen/North rhine

## TL;DR

This study shows that the need for orthodontic treatment varies by age and gender, based on a 20-year analysis of German patients.

## Contribution

The study is the first to analyze KIG classification differences by gender and age over two decades.

## Key findings

- Females showed earlier peaks for several KIG classifications compared to males.
- The distribution of KIG classifications requiring treatment is age- and gender-dependent.
- Gender-specific trends in KIG classifications were observed across different treatment periods.

## Abstract

Patients with statutory health insurance (SHI) in Germany must undergo an assessment of orthodontic treatment need using the KIG classification system since 2002. Recent studies have shown that the prevalence of anomalies is not homogeneous when categorised according to patient age at treatment begin. The aim of this study was to analyse the KIG classifications over a period of 20 years to determine whether there is also a gender-specific prevalence.

Between 2002 and 2021, n = 4940 statutorily insured patients before the age of 18 presented themselves for an orthodontic consultation. Out of these, n = 3701 showed a treatment indication according to current SHI guidelines. The KIG classification was based on the highest existing KIG grade observed in these patients without multiple classifications. The patient cohort was then divided into 3 groups according to gender and chronological age, representing early (PG 1), main (PG 2) and late (PG 3) treatment.

N = 1934 (52.2%, mean age 11.00 ± 2.28 years) of the patients were female, n = 1767 (47.8%, mean age 11.44 ± 2.23 years) male. Out of those, n = 1109 and thus 30.0% of the total collective had the KIG classification D and 43.1% (n = 1595) combined sagittal classifications D + M. Regarding treatment period, the classification K was the most frequent in PG 1, D in PG 2 and E in PG 3 for both genders, and the combination D + M in all groups. Regarding the age at treatment begin, there were different peak values for males and females. Females reached D + M, O + T, B + K and E + P as well as the KIG classifications D, M, O, T, B and K earlier than males, but even age distributions occurred for E and P. The percentage gender distribution in the various age groups showed the opposite trend: In females, there was a decrease in PG 3 compared to PG 1 for all 4 KIG combinations and for 7 of 8 individual anomalies, while it was vice versa in males.

This study was the first to analyse the KIG classification for gender-specific differences and their possible age dependency over a period of 20 years and confirms that the distribution of KIG classifications requiring treatment is not homogeneous, but age-and gender-dependent.

The study results on gender- and age-specific differences in the KIG classification can be regarded as a step towards personalised medicine in orthodontics.