Validity and Reliability of the Photographic Open Bite Severity Index (POSI)

Abstract

Introduction: This study aimed to assess the validity and reliability of the Photographic Open Bite Severity Index (POSI), a recently developed measure of anterior open bite (AOB) severity. In addition, a formula to combine the POSI score and the vertical millimetric measure of AOB into the Combined Open Bite Severity Index (COSI) was developed to serve as a more comprehensive quantitative assessment of AOB severity.Methods: An experienced panel of 5 orthodontists viewed 84 intraoral frontal photos of adult AOB patients at two times to provide their subjective clinical evaluations of AOB severity and treatment difficulty, and a third time, to assign POSI scores. Inter- and intra-examiner reliability of clinical evaluation scores were assessed using the intraclass correlation coefficient and examiner-assigned POSI scores were compared to gold standard POSI scores for accuracy with the weighted kappa. Digitally-designed 3D printed AOB models were photographed from above and below the occlusal plane to assess the effects of photo angulation on POSI reliability. Correlations between examiners’ subjective clinical evaluations and POSI score were evaluated by Spearman rank correlation for POSI validity. Linear regression was used for the creation of the COSI formula. Results: The panel’s subjective clinical evaluations of AOB severity and treatment difficulty showed excellent intra-examiner reliability (ICCs between 0.78 and 0.97) and good inter-examiner reliability (ICC, 0.76 and 0.67, respectively). The examiner-assigned POSI scores were reliable (weighted kappas between 0.94 to 0.97) and accurate when compared to gold-standard POSI scores (weighted kappas between 0.90 and 0.96). Photographs of models obtained from ≤10 degrees above or below the occlusal plane resulted in the same POSI score as that of the un-angulated models. Correlations between gold standard POSI scores and both examiner-assigned AOB severity and treatment difficulty were moderate (Spearman rank correlation, 0.71 and 0.66, respectively). The combination of POSI and estimated clinical OB resulted in the highest correlations with AOB severity and treatment difficulty (correlation: 0.80 and 0.76, respectively) and they were used to create the COSI. Conclusion: The Photographic Open Bite Severity Index (POSI) is a valid and reliable measure of severity and treatment difficulty of anterior open bite (AOB), when scored on an intraoral frontal photograph captured from ≤10 degrees above or below the occlusal plane. While the correlations between POSI alone, estimated clinical OB alone, POSI + estimated clinical OB, and POSI + ceph-measured OB with AOB severity and treatment difficulty were all strong, the combination of POSI + estimated clinical OB (the COSI) produced the highest correlation. The POSI and the COSI can both be utilized as a standardized outcome measure in clinical research or as a measure for AOB in determining treatment need in public health and insurance domains.