Digital model as an alternative to plaster model in assessment of space analysis

Three-Dimensional Analysis of Upper and Lower Arches Using Digital Technology: Measurement of the Index of Bolton and Correspondence between Arch Shapesand Orthodontic Arches

INTRODUCTION

Thanks to the great development of digital technology, viaCAD (computer-aided design) and CAM (computer-aided manufacturing) systems, digital models canbe used as an aid for orthodontic planning decision-making processes as there are numerous studies in the literature that support the validity ofthe digital model measurements of anterior teeth and the total coefficient of Bolton analysis. The aim of the present study isto compare the average length value of the current upper and lower arches with that of a hypothetical nickel-titanium wire and to confirm the reliability and accuracy of digitally taken measurements of the anterior and total Bolton coefficients.In this retrospective study, dental casts of 138 Caucasian adolescent patients were scanned with an extraoral scanner, and Ortho3Shape software was adopted for the following dental cast measurements: actual and ideal lengths of the lower arches and anterior and total Bolton coefficients.In the present study, we found that the mean value of the anterior coefficients of the Bolton index was compatible with those of previous studies, confirming the reliability of digital measurements.Therefore, digital CAD/CAM models may be a viable alternative to plaster models, as they can facilitate model preservation and recovery. For future studies, it would be better to use intraoral scanners (IOSs) to ensure greater accuracy, since they only require one step and allow obtaining better results for the patients.

Estimation of Distances within Real and Virtual Dental Models as a Function of Task Complexity

Orthodontists have seen their practices evolve from estimating distances on plaster models to estimating distances on non-immersive virtual models. However, if the estimation of distance using real models can generate errors (compared to the real distance measured using tools), which remains acceptable from a clinical point of view, is this also the case for distance estimation performed on digital models? To answer this question, 50 orthodontists (31 women and 19 men) with an average age of 36 years (σ = 12.84; min = 23; max = 63) participated in an experiment consisting of estimating 3 types of distances (mandibular crowding, inter-canine distance, and inter-molar distance) on 6 dental models, including 3 real and 3 virtual models. Moreover, these models were of three different levels of complexity (easy, medium, and difficult). The results showed that, overall, the distances were overestimated (compared to the distance measured using an instrument) regardless of the situation (estimates on real or virtual models), but this overestimation was greater for the virtual models than for the real models. In addition, the mental load associated with the estimation tasks was considered by practitioners to be greater for the estimation tasks performed virtually compared to the same tasks performed on plaster models. Finally, when the estimation task was more complex, the number of estimation errors decreased in both the real and virtual situations, which could be related to the greater number of therapeutic issues associated with more complex models.

Accuracy and reproducibility of dental measurements on tomographic digital models: a systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review with meta-analysis was to assess the accuracy and reproducibility of dental measurements obtained from digital study models generated from CBCT compared with those acquired from plaster models.

METHODS

The electronic databases Cochrane Library, Medline (via PubMed), Scopus, VHL, Web of Science, and System for Information on Grey Literature in Europe were screened to identify articles from 1998 until February 2016. The inclusion criteria were: prospective and retrospective clinical trials in humans; validation and/or comparison articles of dental study models obtained from CBCT and plaster models; and articles that used dental linear measurements as an assessment tool. The methodological quality of the studies was carried out by Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. A meta-analysis was performed to validate all comparative measurements.

RESULTS

The databases search identified a total of 3160 items and 554 duplicates were excluded. After reading titles and abstracts, 12 articles were selected. Five articles were included after reading in full. The methodological quality obtained through QUADAS-2 was poor to moderate. In the meta-analysis, there were statistical differences between the mesiodistal widths of mandibular incisors, maxillary canines and premolars, and overall Bolton analysis. Therefore, the measurements considered accurate were maxillary and mandibular crowding, intermolar width and mesiodistal width of maxillary incisors, mandibular canines and premolars, in both arches for molars.

CONCLUSIONS

Digital models obtained from CBCT were not accurate for all measures assessed. The differences were clinically acceptable for all dental linear measurements, except for maxillary arch perimeter. Digital models are reproducible for all measurements when intraexaminer assessment is considered and need improvement in interexaminer evaluation.