The 5-year-olds' Index: determining the optimal format for rating dental arch relationships in unilateral cleft lip and palate.

The aim of this investigation was to determine the optimal format for presenting the 5-year-olds' Index reference models for the assessment of dental arch relationships in unilateral cleft lip and palate (UCLP). The 5-year-olds' Index reference models were presented in four different formats: plaster models, coloured acrylic models, and two digital formats, which included three-dimensional digital models (3D), and black and white photographs. These formats were used to rate 45 plaster models of patients born with UCLP by a total of seven examiners comprising experienced and inexperienced examiners. Scoring was undertaken 1 week apart for each format with the patient models reassigned on each occasion to reduce the effect of memory bias. For intra-examiner agreement, the patient models were scored 3 weeks later under similar conditions by the same examiners. The reliability of using the different formats was determined using the plaster reference models as the 'gold' standard for comparison. Analysis of the results using weighted kappa (k) statistics showed the magnitude of agreement for all the formats of the 5-year-olds' Index were good to very good between examiners. The more experienced examiners were consistently more reliable in their scoring using the different formats. This study clearly demonstrated that 3D digital models of the 5-year-olds' Index could prove to be a promising alternative to physical models of the 5-year-olds' Index.