The Assessment of Digital Study Models Using the GOSLON Yardstick Index.

Objective : To investigate the reproducibility and repeatability of digital models of patients with a unilateral cleft lip and palate (UCLP) using the GOSLON yardstick. Design : Reproducibility and repeatability study. Method : Two examiners used the GOSLON yardstick to assess the intermaxillary dentoalveolar relationship of 30 consecutive UCLP patients by analyzing their 9-year (±3 months) dental study casts and digital study models. The records were rated 1 week apart to avoid bias. The process was repeated 1 month later as a measure of reproducibility. Reliability was assessed by comparing the GOSLON score achieved between the two modalities. Patient dental study casts were sent to 3M Unitek Australia to be scanned using the 3M Unitek Lava(TM) system to produce digital study models. The accuracy of the dental study cast occlusal registration was assessed by both raters prior to sending the study models for scanning. Statistical analysis : The Linear Weighted Kappa statistic and Kendall's Coefficient of Concordance statistic were used to determine the levels of agreement within and between raters. Results : The linear weighted Kappa statistic for intrarater repeatability of digital study models scores were very high (0.89 and 0.97). This compared favorably to the intrarater repeatability of study model casts scores (0.86 and 0.97). There was very good agreement for interrater digital study model scores (0.80 and 0.87) and also for the interrater study model casts scores (0.80 and 0.90). Kendall's Coefficient of Concordance statistic (0.99) and Correlation Coefficient (0.86) support the weighted Kappa results of the digital study model scores. Conclusion : Digital models can be used for GOSLON scoring with a high degree of reproducibility and repeatability.