Reliability and Validity of Dental Measurements Made on Digital and Stone Orthodontic Models

A study model is a precise three dimensional replica of patient’s dentition and plays an important role in treatment planning. Many digital multi-media applications have become available to the clinician and his or her staff to facilitate standard procedures in practice and management. The aim of this study is to evaluate reliability and validity of dental measurement made on digital and stone orthodontic models. The study sample consisted of 22 pairs of randomly selected initial study models from patients that referred to the orthodontic clinic, school of dentistry, Guilan university of medical sciences for treatment. Three dimensional reconstructions of the stone model were generated by dental cone-beam computed tomograghy (CBCT). Mesiodistal widths, Little’s irregularity index, Bolton analysis, arch widths, available and required arch length were measured directly on the casts with a digital caliper and, also on the digital model in ALMA software. Reliability and validity were assessed by using intra-class correlation and paired t-test. Intra and inter-observer reliability for both methods was generally high and acceptable. Comparisons between the measurements on stone cast and digital model showed no statistically significant difference for available arch length, Little’s irregularity index and for mesiodistal tooth width, Bolton analysis and arch widths measure- ment. However, difference between required arch length and space analysis on digital and stone models were not clinically significant. The results of this study support the use of CBCT technology in dental measurements in routine orthodontic analysis except for space analysis.