Age-dependent prevalence of malocclusions requiring treatment according to the KIG classification : A multipart cross-sectional study over a 10-year period from the district of Viersen/North Rhine.

Background and aim: Patients with statutory health insurance (SHI) in Germany must undergo an assessment of orthodontic treatment need using the "Kieferorthopädische Indikationsgruppen" (KIG; orthodontic indication groups) classification system since 2002. A treatment need only exists if anomalies of a certain degree of severity are present. The aim of this study was to evaluate the age-dependent prevalence and percentage distribution of KIG grades requiring treatment in patients with SHI before the age of 18 over a 10-year period.

Patients and methods: Between 2012 and 2021, treatment indication existed for 1951 (1025 female, 926 male) out of 2288 patients with SHI in the cohort of this study before the age of 18 according to current SHI guidelines. The KIG classification was based on the highest existing KIG grade. There were no multiple classifications. The patient cohort was divided into three patient groups (PG) according to chronological age for analysis: PG 1 < 10 years of age (early treatment), PG 2 10 to < 13 years of age (main treatment) and PG 3 13 to < 18 years of age (late treatment).

Results: In PG 1 (454 patients), the KIG classifications D (26.5%), K (25.5%), M (19.4%), and P (18.0%) dominated. In PG 2 (998 patients), classifications D (33.2%), predominated, whereas K (7.5%) and M (5.9%) rarely occurred. The classifications E (12.6%) and P (13.3%) appeared quite frequently. Transverse deviations occurred only about half as often in PG 2 as in PG 1 and PG 3. In PG 3 (499 patients), the classification E (17.6%) was particularly common, while P (2.6%) was rare. The proportion of KIG grades 5 decreased depending on age: 19% in PG 1, 13.5% in PG 2, 10.4% in PG 3. The prevalence of sagittal classifications was highest in all age groups (45.9% in PG 1, 39.1% in PG 2, 31.5% in PG 3).

Conclusions: The distribution of KIG classifications requiring treatment was not homogeneous, but age dependent. The differences were particularly evident in the early treatment group and may be due to the limited applicability of the KIG classification system in patients before late mixed dentition. With increasing age at initial examination, the prevalence of sagittal classifications decreased, while that of vertical classifications increased. Still, the sagittal classifications D and M occurred most frequently in all age groups. The KIG classification D was always the most common in all patients until the age of 18.