Objectification of Orthodontic Treatment Needs: Does the Classification of Malocclusions or a History of Orthodontic Treatment Matter?

Background: Orthodontic classifications make it possible to give an accurate diagnosis but do not indicate an objective orthodontic treatment need. In order to evaluate the need for treatment, it is necessary to use such indicators as the IOTN.
Objectives: The aim of the study was to find (i) relationships between individual diagnosis and objective recommendations for treatment and (ii) an answer to the question whether and which occlusal anomalies play an important role in the objectification of treatment needs.
Material and Methods: Two hundred three 18-year-old adolescents (104 girls, 99 boys) were examined. In order to recognize occlusal anomalies, the classifications proposed by Orlik-Grzybowska and Ackerman-Proffit were used. The occlusal anomalies were divided into three categories: belonging to both classifications, typical of OrlikGrzybowska classification and typical of Ackerman-Proffit classification. In order to determine the objective need for orthodontic treatment, the Dental Health Component (DHC) of the IOTN was used.
Results: The occurrence of the following malocclusions covered by both classifications, namely abnormal overjet, crossbite and Angle's class, had a statistically significant (p < 0.05) impact on an increase of treatment needs in the subjects (DHC > 3). As for the classification by Orlik-Grzybowska, dental malpositions and canine class significantly affected the need for orthodontic treatment, while in the case of the Ackerman-Proffit scheme, it was asymmetry and crowding. There was no statistically significant correlation between past orthodontic treatment and current orthodontic treatment need.
Conclusions: IOTN may be affected by a greater number of occlusal anomalies than it was assumed. Orthodontic treatment received in the past slightly reduces the need for treatment in 18-year-olds.