SEARCH WITHIN CONTENT
Citation Information : Australasian Orthodontic Journal. Volume 33, Issue 1, Pages 73-81, DOI: https://doi.org/10.21307/aoj-2020-087
License : (CC BY 4.0)
Published Online: 30-July-2021
Introduction: Digital models have become more widely accepted for orthodontic diagnostic purposes. Intraoral scanners have the advantage of eliminating the need for conventional impressions. The aim of the present study was to assess the reliability and reproducibility of the Lythos intraoral scanner and to determine if a significant advantage is delivered over stone model and caliper measurements in tooth width and Bolton ratio accuracy.
Methods: The study comprised 30 typodont models for which conventional alginate impressions and digital scans were obtained to generate stone and digital models, respectively. Mesiodistal tooth width measurements and Bolton ratios were obtained with either calipers and stone models or with Digicast (Ormco Lythos digital model software, Ormco, CA, USA) software using digital models. Pearson’s correlation coefficients tested intra-examiner reliability. Interclass correlation coefficients were used to assess agreement between examiners (reproducibility). The differences in the mean tooth width measurements and Bolton ratios from the typodont values and either the digital or conventional method were used to assess validity by applying two tailed t-tests.
Results: The measurements obtained from the Lythos and stone models had near perfect intra-examiner agreement (Pearson ≥ 0.98). The inter-examiner reproducibility for tooth widths, anterior Bolton and overall Bolton ratio was high and similar for both methods (Lythos scanner Interclass correlation coefficient (ICC) above 0.89, stone models ICC above 0.92). Stone model measurements were statistically twice as accurate as those derived from the digital system (0.032 mm versus 0.074 mm). There were no significant differences in accuracy between the methods for Bolton calculations. Clinically, there was no difference between the methods for tooth width measurements and Bolton calculations.
Conclusions: The Lythos system is as reliable and reproducible as conventional calipers and stone models in tooth width measurements and Bolton calculations. The caliper method presents a statistically more valid tooth width measurement technique but the clinical significance of this is questionable.
1. Bailey E, Nelson G, Miller AJ, Andrews L, Johnson E. Predicting tooth-size discrepancy: A new formula utilizing revised landmarks and 3-dimensional laser scanning technology. Am J Orthod Dentofacial Orthop 2013;143:574-85.
2. Tomassetti JJ, Taloumis LJ, Denny JM, Fischer JR Jr. A comparison of 3 computerized Bolton tooth-size analyses with a commonly used method. Angle Orthod 2001;71:351-7.
3. Shellhart WC, Lange DW, Kluemper GT, Hicks EP, Kaplan AL. Reliability of the Bolton tooth-size analysis when applied to crowded dentitions. Angle Orthod 1995;65:327-34.
4. Stevens DR, Flores-Mir C, Nebbe B, Raboud DW, Heo G, Major PW. Validity, reliability, and reproducibility of plaster vs digital study models: comparison of peer assessment rating and Bolton analysis and their constituent measurements. Am J Orthod Dentofacial Orthop 2006;129:794-803.
5. Cuperus AM, Harms MC, Rangel FA, Bronkhorst EM, Schols JG, Breuning KH. Dental models made with an intraoral scanner: a validation study. Am J Orthod Dentofacial Orthop 2012;142:308-13.
6. Wiranto MG, Engelbrecht WP, Tutein Nolthenius HE, van der Meer WJ, Ren Y. Validity, reliability, and reproducibility of linear measurements on digital models obtained from intraoral and conebeam computed tomography scans of alginate impressions. Am J Orthod Dentofacial Orthop 2013;143:140-7.
7. Fleming PS, Marinho V, Johal A. Orthodontic measurements on digital study models compared with plaster models: a systematic review. Orthod Craniofac Res 2011;14:1-16.
8. Naidu D, Freer TJ. Validity, reliability, and reproducibility of the iOC intraoral scanner: a comparison of tooth widths and Bolton ratios. Am J Orthod Dentofacial Orthop 2013;144:304-10.
9. Houston WJ. The analysis of errors in orthodontic measurements. Am J Orthod 1983;83:382-90.
10. Roberts CT, Richmond S. The design and analysis of reliability studies for the use of epidemiological and audit indices in orthodontics. Br J Orthod 1997;24:139-47.
11. Luu NS, Nikolcheva LG, Retrouvey JM, Flores-Mir C, El-Bialy T, Carey JP et al. Linear measurements using virtual study models. Angle Orthod 2012;82:1098-106.
12. Santoro M, Galkin S, Teredesai M, Nicolay OF, Cangialosi TJ. Comparison of measurements made on digital and plaster models. Am J Orthod Dentofacial Orthop 2003;124:101-5.
13. Torassian G, Kau CH, English JD, Powers J, Bussa HI, Salas-Lopez AM et al. Digital models vs plaster models using alginate and alginate substitute materials. Angle Orthod 2010;80:662-9.
14. Lundstrom A. Intermaxillary tooth width ratio and tooth alignment and occlusion. Acta Odontol Scand 1955;12:265-92.
15. Hunter WS, Priest WR. Errors and discrepancies in measurement of tooth size. J Dent Res 1960;39:405-14.
16. Coleman RM, Hembree JH Jr, Weber FN. Dimensional stability of irreversible hydrocolloid impression material. Am J Orthod 1979;75:438-46.
17. Endo T, Uchikura K, Ishida K, Shundo I, Sakaeda K, Shimooka S. Thresholds for clinically significant tooth-size discrepancy. Angle Orthod 2009;79:740-6.
18. Othman S, Harradine N. Tooth size discrepancies in an orthodontic population. Angle Orthod 2007;77:668-74.