Comparison of three different instruments for orthodontic study model analysis

Abstract

INTRODUCTION: A proper model analysis forms a vital part of the orthodontic diagnosis process, but it remains a time-consuming procedure. In day-to-day practice, many orthodontists assess the models subjectively, without applying analytical tests, due to the time it takes to do proper model analysis.^1,2 Plaster dental models have long been the gold standard for orthodontic study model analysis and to calculate the Bolton index for tooth size disproportions, as well as intra-arch space discrepancies.^3,4 Vernier callipers or needle pointed dividers are traditionally used to perform measurements on dental models.⁵ More recently digital orthodontic study models that are computer-based have been developed and have the potential to replace the traditional plaster orthodontic models.⁶ AIMS AND OBJECTIVES: The aim of this study was to do model analysis on one hundred orthodontic cases by making use of three different measuring tools. The objective was to see if a difference exists with regards to the measurements produced by the three different instruments and to compare the instruments with each other. MATERIAL AND METHODS: Three different instruments were used to measure Ave values on one hundred orthodontic study models. The three instruments included a Boley Gauge, Digital Vernier Calliper and Carestream 3600 scanner with accompanying software. The five values measured on the study models were: maxillary intercanine width, maxillary intermolar width, mesio-distal width of tooth 11, mesio-distal width of tooth 46 and mesio-distal width of tooth 41. RESULTS: The statistical analysis performed showed that the difference in measurements produced by the three instruments were not statistically significant for the inter-molar width (p = 0.849), intercanine width (p = 0.657), mesio-distal width of tooth 11 (p = 0.178) and mesio-distal width of tooth 41 (p = 0.240 The difference in measurements for the mesio-distal width of tooth 46 were statistically significant (p<0.01). However no clinically significant difference was found when the measurements produced by the three instruments were compared. CONCLUSIONS: All three of the instruments produced accurate measurements and can be used confidently when doing a comprehensive study model analysis for orthodontic diagnosis and treatment planning. The values produced were similar for all three instruments with insignificant differences between the three.