Assessing Reliability of Salzmann Index Scoring Amongst Orthodontic Practitioners in Pennsylvania

Abstract

Objectives: The state of Pennsylvania uses the Salzmann Index as a qualifying criterion for patients to be covered for tax-supported orthodontic care. The Salzmann Index measures the severity of a malocclusion by giving different point values to certain intra-arch and inter-arch deviations, and produces a numeric score for each patient examined. The aim of this study was to assess the reliability of Salzmann Index scores amongst orthodontic practitioners in Pennsylvania. Methods: 20 participating orthodontists were asked to complete Salzmann Indices for three sets of pre-treatment dental study models which included: (a) A Class I malocclusion (b) A Class II malocclusion (c) A Class III malocclusion. The variability in examiner scoring was analyzed to determine the reliability of the Salzmann Index. This was then correlated with responses to survey questions to evaluate factors that may influence the practitioners’ scoring of the indices. Results: In total, 20 orthodontists completed the indices and survey. The Class II malocclusion had an average total score closest to the 25 point cut-off and the largest variability in scoring (M=27.15, SD=8.51), compared to the Class I malocclusion (M=18.6, SD=5.86) and Class III malocclusion (M=31.15, SD=4.11). Inter-rater reliability (IRR) for the index scores as measured by ICC(3) were 87.9% (F(2,38)= 226.50, p<.000) for the Class I malocclusion, 40.9% (F(2,38)=15.90, p<.000) for the Class II malocclusion, and 67.3% (F(2,38)=45.87, p<.000) for the Class III malocclusion. No significant correlation was found between the number of years in practice or percentage of patients covered under Medicaid plans and the index scoring. Conclusions: Overall, there was moderate reliability in the Salzmann Index scores amongst the participating orthodontists, with the Class II malocclusion scores having the poorest reliability. For the Class II case, the anterior segment inter-arch deviation score (overbite/overjet) showed the most variability, indicating orthodontists’ difficulty in scoring this relationship.