A Comparative Study of Two Digital Model Analysis Based on Bolton Ratio

Jumana Al-Abbadi^1*, Başak Baş², Rojda Akçar², Anwar Rahamneh³, M Alp Tavas⁴

¹Specialist in Orthodontics, Dental Department, Jordanian Royal Medical Services, Amman, Jordan
²PhD Student in Orthodontics, Orthodontic Department, Medipol University Graduate School of Health Sciences, Istanbul, Türkiye
³Senior Specialist in Orthodontics, Dental Department, Royal Medical Services, Amman, Jordan
⁴Professor of Orthodontics, Orthodontic Department, Istinye University Dental Hospital, Istanbul, Türkiye

*Correspondence author: Jumana Al-Abbadi, Specialist in Orthodontics, Dental Department, Jordanian Royal Medical Services, Amman, Jordan; E – mail: [email protected]

Citation: Al-Abbadi J, et al. A Comparative Study of Two Digital Model Analysis Based on Bolton Ratio. J Dental Health Oral Res. 2025;6(3):1-9.

Copyright^© 2025 by Al-Abbadi J, et al. All rights reserved. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Table 1: This table represents the descriptive statistics. Mean values of Bolton ratios and anterior ratios obtained by digital model analyses. T (total Bolton ratio), A (anterior Bolton ratio), 1 and 2 denote first and second round of measurements.

Table 2: Represents the intra – class correlation coefficient, which gives the inter – examiners reproducibility/reliability. T (total Bolton ratio), A (anterior Bolton ratio), 1 and 2 denote first and second round of measurements. ICC (intra – class correlation coefficient).

Table 3: Represents the intra – examiners reproducibility/reliability. T (total Bolton ratio), A (anterior Bolton ratio), 1 and 2 denote first and second round of measurements. ICC (intra – class correlation coefficient). N (sample number).

Table 4: Concordance correlation coefficient between OrthoCad – NEMOCAST for total and anterior Bolton ratio. T (total Bolton ratio), A (anterior Bolton ratio), 1 and 2 denote first and second round of measurements. ICC (intra – class correlation coefficient). N (sample number). CCC (Concordance Correlation Coefficient).

Table 5: Comparison for the 3 examiners for Total and Anterior Bolton between Nemocast and OrhoCad, difference I – N in T and A, have statistically significant difference. (p<0,05) .SD (Standard deviation), T (total Bolton ratio), A (anterior Bolton ratio).

Discussion

A tooth-size study typically requires a Boley gauge, Vernier caliper or a needle – point divider. Indeed many clinicians still use these traditional devices to measure variations in tooth size. However, they are not in the majority as was shown by Shreidan who said only 47% of orthodontists he surveyed regularly use Bolton analysis [14]. The surge of computerized orthodontic diagnosis is likely to render this customary approach obsolete and already digital methods are in vogue. Hence the goal of our study was to compare the measurement accuracy of the Bolton tooth – size difference between the OrthoCad and Nemocast software. Digital Bolton analysis has been available in orthodontics for many years. OrthoCAD accuracy for Bolton analysis was shown by Naidu and Freer over a decade ago. Nemocast (Nemostudios, Madrid, Spain) has a good reputation and underwent an improvement process over the years [2]. Hence the effectiveness of both software is well established. Our literature review did not reveal previous research comparing the two software utilized in this study. Apart from contrasting the two methods, intra – and inter – examiner reliability within each was evaluated during the process of digital model measurements.

The use of digital models in clinical practice has significant promise if the models are dependable and simple to operate [24]. Like many other researchers who naturally share this opinion, we chose to work on accurately prepared virtual models. Besides fracture, loss and difficulties in storage disadvantages linked to plaster models, their three – dimensional operation in the semi – adjustable articulators is practically defunct due to virtual digital articulators and three – dimensional orthognathic surgery planning software. Dalstra, et al., White, et al., and Flügge, et al., are among the workers who favored virtual digital models [14-16]. At this time, digital orthodontic model technologies are almost perfected and problems of laboratory time, archiving and cost inherent in stone models are eliminated. Furthermore, the transferability of digital models to any location is unrivaled. It is well known that if pouring of stone is delayed with alginate impressions, plaster models may lack accuracy. Hence there might be marginal dimensional errors in measuring. This is another shortcoming no matter how remote.

These computer programs give numerous different analyses in addition to the Bolton analysis. OrthoCad and Nemocast have too many diagnostic tools to list individually. In this article, only Bolton analysis was investigated.

Selecting exactly the same mesial or distal points of tooth crowns on plaster model images generated by the Nemocast versus Orthocad software is practically impossible, which may explain the variations in total and anterior Bolton ratios between the two software. This issue may have been considerably influenced by the inability to enlarge digital models. According to Houston, the difficulty in identifying landmarks is one of the greatest sources of random error [26]. This is of particular importance for digital models, because a 3-dimensional structure appears as a 2-dimensional image, making it more difficult to detect landmarks [17,19]. Furthermore, it may be difficult for examiners to locate the exact mesial and distal locations on tooth crowns, making it difficult to quantify consistently and accurately. Using the OrthoCad software for the Bolton tooth-size study, Tomasetti, et al., reached the same finding [20,21].

In our study, when OrthoCad and Nemoceph were compared, clinically significant differences were detected between total and anterior ratios calculated with these respective software [22-30]. In other words, Nemocast and OrthoCad created total and/or anterior ratios were found to be statistically different. These deviations could be attributable to a number of factors: 1 – OrthoCad and Nemocast may have different fabrication process distortions; operators were less familiar with the Nemocast software than they were with OrthoCad. 2-In comparison to OrthoCad, the Nemocast software is more complex and requires an excessive number of steps and additional time to calculate the Bolton analysis. 3-Potential operator differences, it was difficult to pinpoint the exact mesial and distal points to be used for the width measurement when clicking the mouse on tooth locations for width. OrthoCad utilizes a “click and drag” method to mark the mesial and distal points, making it difficult to measure tooth widths consistently and precisely. 4 – differences in model details between OrthoCad and Nemocast software around tooth borders or contact points to determine an accurate point of measurement.

The intra – examiner and inter – examiner coherence of total and anterior Bolton ratios were almost perfect for both software which means that both software are beneficial. These offer time – efficient and reproducible methods of teeth measurements. Clinicians can orientate themselves rapidly to these software. Thus these are invaluable tools in a teaching clinic. These can substitute for the original ways of tooth size measurement, but further upgrades in the computerized methods are advised to overcome the drawbacks discussed above. Finally, it is the decision of the clinician to decide if these software alternative methods are acceptable and cost – effective.

Conclusion

Orthocad and Nemocast are new and promising software that will be enormously popular in the near future, both of them can generate reproducible results and can be used easily by trained clinicians. Some of the drawbacks especially those related to the difficulty in identifying landmarks need to be solved and these computerized software should be upgraded to make them more precise and user friendly. Further research using layer samples could be helpful in order to evaluate various software in calculating the Bolton ratios which are indispensable for detailing and finishing stage of fixed appliance treatment. 

Conflict of Interest

There are no conflicts of interest that may have influenced the research, authorship or publication of the article.

Financial Disclosure

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical Statement

This project was exempt from IRB review as it did not qualify as human subject research under federal regulations.

Author Contributions

Jumana Al – Abbadi, Başak Baş, Rojda Akçar, contributed to the conception, design, data acquisition, analysis and interpretation, drafted and critically revised the manuscript and gave the final approval; Anwar Rahamneh, M.Alp Tavas, contributed to the conception, design and data interpretation, critically revised the manuscript and gave the final approval. All authors gave final approval and agreed to be accountable for all aspects of the work.

References

1. Bell A, Ayoub AF, Siebert P. Assessment of the accuracy of a three – dimensional imaging system for archiving dental study models. J Orthod. 2003;30(3):219 – 23.
2. Nalcaci R, Topcuoglu T, Ozturk F. Comparison of Bolton analysis and tooth size measurements obtained using conventional and three – dimensional orthodontic models. Eur J Dent. 2013;7(1):66 – 70.
3. Taneva E, Kusnoto B, Evans C. 3D scanning, imaging and printing in orthodontics. Am J Orthod Dentofac Orthop. 2015;148(5):862 – 72.
4. Costalos PA, Sarraf K, Cangialosi TJ, Efstratiadis S. Evaluation of the accuracy of digital model analysis for the American Board of Orthodontics objective grading system for dental casts. Am J Orthod Dentofac Orthop. 2005;128(5):624 – 9.
5. Bichu YM, Alwafi A, Liu X, Andrews J, Ludwig B, Bichu AY, et al. Advances in orthodontic clear aligner materials. Bioact Mater. 2023;22:384 – 403.
6. Lippold C, Kirschneck C, Schreiber K, Abukiress S, Tahvildari A, Moiseenko T, et al. Methodological accuracy of digital and manual model analysis in orthodontics: A retrospective study. Comput Biol Med. 2015;62:103 – 9.
7. Harrell WR, Hatcher DC, Bolt RL. In search of anatomic truth: 3 – dimensional digital modeling and the future of orthodontics. Am J Orthod Dentofac Orthop. 2002;122(3):325 – 30.
8. 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 Dentofac Orthop. 2006;129(6):794 – 803.
9. Mullen SR, Martin C, Ngan P, Gladwin M. Accuracy of space analysis with emodels and plaster models. Am J Orthod Dentofac Orthop. 2007;132(3):346 – 52.
10. Leifert MF, Leifert MM, Efstratiadis SS, Cangialosi TJ. Comparison of space analysis evaluations with digital models and plaster dental casts. Am J Orthod Dentofac Orthop. 2009;136(1):16.e1 – 7.
11. Fleming P, Marinho V, Johal A. Orthodontic measurements on digital study models compared with plaster models: A systematic review. Orthod Craniofac Res. 2010;14(1):1 – 16.
12. Reuschl RP, Heuer W, Stiesch M, Wenzel D, Dittmer MP. Reliability and validity of measurements on digital study models and plaster models. Eur J Orthod. 2016;38(1):22 – 6.
13. Bootvong K, Liu Z, McGrath C, Hägg U, Wong RWK, Bendeus M, et al. Virtual model analysis as an alternative approach to plaster model analysis: Reliability and validity. Eur J Orthod. 2010;32(5):589 – 95.
14. Dalstra M, Melsen B. From alginate impressions to digital virtual models: accuracy and reproducibility. J Orthod. 2009;36(1):36 – 41.
15. White AJ, Fallis DW, Vandewalle KS. Analysis of intra – arch and interarch measurements from digital models with 2 impression materials and a modeling process based on cone – beam computed tomography. Am J Orthod Dentofac Orthop. 2010;137(4):456.e1 – 9.
16. Flügge TV, Schlager S, Nelson K, Nahles S, Metzger MC. Precision of intraoral digital dental impressions with iTero and extraoral digitization with the iTero and a model scanner. Am J Orthod Dentofac Orthop. 2013;144(3):471 – 8.
17. Zilberman O, Huggare JAV, Parikakis KA. Evaluation of the validity of tooth size and arch width measurements using conventional and three – dimensional virtual orthodontic models. Angle Orthod. 2003;73(3):301 – 6.
18. Quimby ML, Vig K, Rashid R, Firestone A. The accuracy and reliability of measurements made on computer – based digital models. Angle Orthod. 2004;74(3):298 – 303.
19. Sousa MVS, Vasconcelos EC, Janson G, Garib D, Pinzan A. Accuracy and reproducibility of 3 – dimensional digital model measurements. Am J Orthod Dentofac Orthop. 2012;142(2):269 – 73.
20. Bolton WA. The clinical application of a tooth – size analysis. Am J Orthod. 1962;48(7):504 – 29.
21. Tomassetti JJ, Taloumis LJ, Denny JM, Fischer JR. A comparison of 3 computerized Bolton tooth – size analyses with a commonly used method. Angle Orthod. 2001;71(5):351 – 7.
22. Alamir G, Tsay TP, Manasse RJ. Reliability study of the Bolton analysis using dental models from cases passed by the American Board of Orthodontics Clinical Examination. J Dent Oral Disord. 2017;3(1):1053.
23. Tunca M, Tunca Y, Kotan S, Bilen S. Comparison of linear measurements and Bolton analysis on the model obtained from conventional method with OrthoCAD software. Van Dent J. 2021;2(2):1 – 10.
24. Akdeniz BS, Aykaç V, Turgut M, Çetin S. Digital dental models in orthodontics: A review. J Exp Clin Med. 2022;39(1):250 – 5.
25. Hunter WS, Priest WR. Errors and discrepancies in measurement of tooth size. Am J Orthod. 1960;39(2):405 – 14.
26. Houston WJ. The analysis of errors in orthodontic measurements. Am J Orthod. 1983;83(5):382 – 90.
27. Phulari BS. History of orthodontics: A glance at an exciting path, the oldest specialty of dentistry has treaded so far. New Delhi: Jaypee Brothers Medical Publishers. 2013.
28. Camardella LT, Breuning H, de Vasconcellos Vilella O. Accuracy and reproducibility of measurements on plaster models and digital models created using an intraoral scanner. J Orofac Orthop. 2017;78(3):211 – 20.
29. Lee SP, DeLong R, Hodges JS, Hayashi K, Lee JB. Predicting first molar width using virtual models of dental arches. Clin Anat. 2007;21(1):27 – 32.
30. Sheridan JJ. The Readers’ Corner: Topics are tooth – size discrepancies and extractions. J Clin Orthod. 2000;34(10):593 – 7.