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Accuracy and validity of space analysis and irregularity index measurements using digital models Cover

Accuracy and validity of space analysis and irregularity index measurements using digital models

Open Access
|Dec 2023

Abstract

Background

Digital copies of study models may avoid the storage and retrieval issues of plaster study models, but measurements made on digital models may not be as accurate as measurements made on traditional study models.

Aim

To determine the reliability and validity of tooth size–arch length discrepancies (TALD), irregularity indices and arch lengths (four- and six-segment analyses) measured directly on study models with digital calipers with the same measurements measured on digital copies of the study models with proprietary software.

Methods

The irregularity indices and TALDs (four- and six-segments) were measured on 50 sets of pretreatment plaster models. The plaster models were measured using manual calipers with a digital readout. The models were then couriered to OrthoCAD and digital copies emailed to the authors. The digital models were measured with the proprietary software provided with the digital models. Repeat measurements of the TALDs and the irregularity indices were subjected to intraclass correlations (ICC) to assess the reliability. The least squares means of variation was used to assess validity and the impact of measuring arch length (four- and six-segments) on the digital models, and the implications on the TALDs.

Results

There were high correlations (ICC) ranging from 98.6–99.9 per cent for both the irregularity indices and the TALDs. The choice of manual over computer and four-segment over six-segment analysis had a significant effect when measuring lower arch lengths (p < 0.05), but they had no effect on the upper arch findings.

Conclusions

Reliable measurements of the irregularity index and the TALD can be made on digital models. Computer measurements of TALDs on digital models were more consistent than manual measurements of TALDs on plaster models. Six-segment analyses of lower arch lengths on digital and plaster models gave more consistent findings than the four-segment analyses.

DOI: https://doi.org/10.2478/aoj-2008-0012 | Journal eISSN: 2207-7480 | Journal ISSN: 2207-7472
Language: English
Page range: 83 - 90
Submitted on: Mar 1, 2007
Accepted on: Jun 1, 2008
Published on: Dec 13, 2023
Published by: Australian Society of Orthodontists Inc.
In partnership with: Paradigm Publishing Services
Publication frequency: 1 times per year

© 2023 Roy W. Goonewardene, Mithran S. Goonewardene, John M. Razza, Kevin Murray, published by Australian Society of Orthodontists Inc.
This work is licensed under the Creative Commons Attribution 4.0 License.