Abstract
PurposeTo assess the validity, reliability, reproducibility, and objectivity of measurements on stone casts of patients with mixed dentitions compared to measurements on three-dimensional (3D) digital models derived from surface scans of the stone casts.MethodsPairs of stone casts of 30 young patients in their mixed dentition stage were included and processed into 3D digital models using an intraoral scanner (iTero Element 2; Align Technology, San Jose, CA, USA). Then an experienced and an inexperienced examiner independently performed measurements of five defined parameters, each in triplicate, both on the digital models with analysis software (OnyxCeph3™; Image Instruments, Chemnitz, Germany) and on the original casts with a vernier calliper. Paired t-tests were used for validity and interexaminer objectivity, Pearson correlation coefficients for intermethod reliability, and intraclass correlation coefficients (ICCs) for reproducibility testing.ResultsSignificant (p < 0.05) intermethod differences were identified for four parameters, but only the differences for overbite and intermolar distance exceeded the threshold of clinical relevance (≥ 0.5 mm). Intermethod reliability was high and method error invariably lower for the digital measurements and for the experienced examiner. Both examiners achieved ICCs > 0.907 with both methods. Interexaminer variation involved significant differences for all parameters but one (intermolar distance) on the stone casts and for three parameters on the digital models.ConclusionMeasurements performed on digital models of mixed dentitions can yield clinically acceptable outcomes with OnyxCeph3™ software. Both the digital and the analogue measurements were highly reproducible and reliable. Objectivity of the measurements could not be confirmed, as operator experience did make a difference.
Highlights
IntroductionPaperless patient information systems, including digital photographs and radiographs, are today standard [33]
Examiner 1 was most consistent with the transversal measurement according to McNamara on the stone casts (ICC: 0.998) and with overbite on the digital models (ICC: 0.999) versus least consistent with arch length discrepancies (ALD) upper jaw (UJ) (ICC: 0.918) and McNamara (ICC: 0.968), respectively
Digital models of permanent dentitions are today an accepted alternative to stone casts in orthodontics. Driven by both an emerging aesthetic idealism and intraoral scanners eliminating the need for impression-taking, the demand for orthodontic treatment of paediatric patients has been growing in recent years
Summary
Paperless patient information systems, including digital photographs and radiographs, are today standard [33]. It is essential for comprehensive orthodontic diagnostics and treatment planning to analyse study casts that represent the patient’s dentition. The gold standard for diagnostic measurements is to use a calliper on a stone cast [3]. Following research and development to address this issue, Cadent ( Align Technology, San Jose, CA, USA) introduced the first generation of OrthoCadTM software for “digital casts” in 1999 [15]. In 2006, this was followed by the iTero Element (Align Technology, San Jose, CA, USA) intraoral scanner (IOS), which uses parallel confocal imaging and point-and-stitch reconstruction to generate three-dimensional (3D) computerized images. Current software applications (e.g., OnyxCeph3TM; Image Instruments, Chemnitz, Germany) are capable of managing, analysing, and generating virtual arch models
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