Prevalence of malocclusions requiring treatment according to the KIG classification : A multipart cross-sectional study over a 20-year period in the district of Viersen/North Rhine.

Background and aim: In Germany, the reimbursement of orthodontic treatment costs within the framework of the statutory health insurance (GKV) was restricted on 01 January 2002 by the introduction of the orthodontic indication groups (KIG). The aim of this study was to evaluate the prevalence of findings requiring treatment in a specialist practice over a 20-year period. The results were then compared with data from existing older studies.

Patients and methods: The distribution of treatment-eligible KIG (KIG classifications grades 3-5) among patients with statutory health insurance in an orthodontic practice in North Rhine was determined over a 20-year period (2002-2021) after the introduction of the KIG system. This period was additionally scrutinized in four 5‑year periods according to the operating cycles of the practice. Findings were classified into the highest of 19 possible KIG treatment needs levels. Multiple classifications were not made.

Results: Orthodontic treatment was indicated in a total of 4537 (2393 female, 2144 male) patients according to current statutory health insurance guidelines. The KIG classification "D" (increased overjet) was the most frequent within the observed 20 years with 24.3%. Among 11 KIG classifications, 86.1% of the 6 most frequent and 13.9% of the 5 rarest findings were observed constantly over all periods. Of 19 possible indications, "D4" was the most frequent with 19.6%. Of 4537 patients, 20.7% had KIG grade 3, 63.6% KIG grade 4 and 15.7% KIG grade 5. The prevalence of sagittal deviations "D" and "M" was 35.0%, transverse "B" and "K" 17.9% and vertical "O" and "T" 3.7%. Tooth position anomalies "E" and "P" had a share of 24.6%.

Conclusions: The present study confirms existing findings as well as the nationwide data of the National Association of Statutory Health Insurance Dentists (KZBV) from 2020: The sagittal deviations "D" (increased overjet) and "M" (negative overjet) represented the most frequent findings with KIG D4 as the most common classification. The prevalence and age distribution of KIG grades 3-5 requiring treatment corresponded to nationwide comparative data.