Intra-observer reliability and agreement of manual and digital orthodontic model analysis

Reliability and time-based efficiency of artificial intelligence-based automatic digital model analysis system

OBJECTIVES

To compare the reliability, reproducibility, and time-based efficiency of automatic digital (AD) and manual digital (MD) model analyses using intraoral scan models.

MATERIAL AND METHODS

Two examiners analysed 26 intraoral scanner records using MD and AD methods for orthodontic modelling. Tooth size reproducibility was confirmed using a Bland-Altman plot. The Wilcoxon signed-rank test was conducted to compare the model analysis parameters (tooth size, sum of 12-teeth, Bolton analysis, arch width, arch perimeter, arch length discrepancy, and overjet/overbite) for each method, including the time taken for model analysis.

RESULTS

The MD group exhibited a relatively larger spread of 95% agreement limits when compared with AD group. The standard deviations of repeated tooth measurements were 0.15 mm (MD group) and 0.08 mm (AD group). The mean difference values of the 12-tooth (1.80-2.38 mm) and arch perimeter (1.42-3.23 mm) for AD group was significantly (P < 0.001) larger than that for the MD group. The arch width, Bolton, and overjet/overbite were clinically insignificant. The overall mean time required for the measurements was 8.62 min and 0.56 min for the MD and AD groups, respectively.

LIMITATIONS

Validation results may vary in different clinical cases because our evaluation was limited to mild-to-moderate crowding in the complete dentition.

CONCLUSIONS

Significant differences were observed between AD and MD groups. The AD method demonstrated reproducible analysis in a considerably reduced timeframe, along with a significant difference in measurements compared to the MD method. Therefore, AD analysis should not be interchanged with MD, and vice versa.

Accuracy and eligibility of Bonwill⁃Hawley arch form established by CBCT image for dental crowding measurement: a comparative study with the conventional brass wire and caliper methods

OBJECTIVES

The purpose of this study was to develop a novel Bonwill⁃Hawley method (Bonwill⁃Hawley arch form based on CBCT image) for the assessment of dental crowding, and to investigate and compare the accuracy and eligibility with the conventional brass wire and caliper methods under different crowding conditions.

MATERIAL AND METHODS

Sixty patients with the pair of plaster casts and CBCT data were collected. All the casts were marked and transformed into digital models using iTero scanner, and imported into OrthoCAD software to measure the required space. Using the conventional brass wire (M1) and caliper methods (M2), the available space and dental crowding were measured and calculated basing on digital models, respectively. Correspondingly, the axial planes in the level of dental arches were oriented and captured from the CBCT images to draw the Bonwill⁃Hawley arch forms (M3), which were used to measure and calculate the available space and dental crowding. For each method, intra and inter-examiner reliabilities were evaluated with intra-class correlation coefficients (ICCs). Wilcoxon test and Kruskal-Wallis test were performed for statistically analyzing the discrepancy among different groups.

RESULTS

Both intra- and inter-examiner reliability were generally excellent for all parameters obtained by the three methods, except for the dental crowding measured using M1(ICC: 0.473/0.261). The dental crowding measured using M2 were significantly increased in mild, moderate and severe-crowding groups compared with M1. However, no significant difference was detected between M1 and M3 in severe-crowding group (maxilla, p = 0.108 > 0.05; mandible, p = 0.074 > 0.05). With the deterioration of crowding condition, the discrepancy of dental crowding between M1 and M2, or M1 and M3 were significantly decreased (maxilla, M2-M1, mild VS serve, p = 0.003 < 0.05; maxilla, M3-M1, mild VS serve, p = 0.003 < 0.05; mandible, M2-M1, mild VS serve, p = 0.000 < 0.001; mandible, M3-M1, mild VS serve, p = 0.043 < 0.05).

CONCLUSION

Dental crowding measured using the novel Bonwill⁃Hawley method was relatively greater than the caliper method, but not exceeding the brass wire method, which wound gradually come close to the brass wire method with the deterioration of crowding condition.

CLINICAL RELEVANCE

The Bonwill⁃Hawley method basing on CBCT image proved to be a reliable and acceptable choice for orthodontists to analyze the dental crowding.

[Degree of reliability of the assessment of the Bolton analysis in three-dimensional virtual models versus plaster models. a review]

Introduction

Bolton analysis is used to determine anomalies with respect to the dental mass, for diagnosis and treatment planning purposes, the possibility of using a digital method was introduced and tested to measure the size of the mesiodistal tooth. In this way, digital dental technology has made digital study models become popular in orthodontics.

Objective

to evaluate the degree of reliability of the evaluation of the Bolton analysis in three-dimensional virtual models versus plaster models through a review of the literature.

Materials and methods

A search was carried out in the primary databases of the international scientific literature on health sciences: Medline, through PubMed, SciELO, Lilacs, and Embase. Review articles published between the year 2000 and October 2021 were included.

Results

The desktop scanner was the best option for digitizing dental models, but this does not detract from CBCT and intraoral laser scanners, which are still an option. Reasonable validity for digitizing 3D models with results within the "clinically acceptable" range was found.

Conclusions

3D digital models generated with intraoral and extraoral scanners are reliable and accurate compared to conventional impressions and save time, in most cases statistically significant differences were found, but of little clinical relevance.

Comparison of intraoral scanning and CBCT to generate digital and 3D-printed casts by fused deposition modeling and digital light processing

OBJECTIVES

to evaluate trueness and precision of digital casts from intraoral scanning (IOS) and cone beam computed tomography (CBCT); trueness and precision of 3D-printed casts using digital light processing (DLP) and fused deposition modeling (FDM); the influence of digitizing method in the 3D-printed casts and, to compare STL data after DICOM segmentation and conversion.

METHODS

a reference cast was digitized with IOS and CBCT, and 3D-printed using FDM and DLP. Linear measurements of occlusocervical (OC), interarch (IEA), and mesiodistal (MD) dimensions were taken on reference, digital and 3D-printed casts. Trueness was observed as the distortion, and precision was observed as the variation of measurements. One and Two-way ANOVA, Student t-test, and Chi-Square were applied to analyze data.

RESULTS

distortion varied between digital casts for all dimensions; at OC, both showed expanded dimensions with IOS being significantly greater; in turn, CBCT digital casts showed higher distortion at IEA and MD. Dimensions of 3D-printed casts showed a predominance of shrinkage, DLP presented higher distortion compared to FDM for both digitizing methods. Digitizing methods influenced the 3D-printing of casts, especially for DLP. Regarding precision, no statistical difference was found. STL converted from DICOM showed statistical difference in IEA (p < 0.001).

CONCLUSIONS

digital casts showed distortion depending on the digitizing method. IOS was better in IEA and MD, and CBCT in OC dimensions. Overall, DLP casts presented higher distortion compared to FDM. The digitizing method influences trueness on 3D-printed casts. File conversion from DICOM to STL per se could change the dimension.

CLINICAL SIGNIFICANCE

This investigation showed that digital casts from IOS and CBCT as well 3D-printed casts from FDM and DLP can show different trueness. It is clinically relevant as clinicians have various workflows available in Digital Dentistry which involve these digitizing and manufacturing methods.

Bone Modifications Induced by Rapid Maxillary Expander: A Three-Dimensional Cephalometric Pilot Study Comparing Two Different Cephalometric Software Programs

Cone-beam computed tomography (CBCT) allows for more accurate 3D study of the craniofacial region and the development of a very precise treatment plan. The present pilot study aims to evaluate the skeletal outcomes of the rapid maxillary expander (RME) on the sagittal, transverse and vertical planes in growing patients subjected to CBCT at T0 and T1, and to compare the results from two different programs. The effects of the RME are monitored in 11 patients who were subjected to CBCT at T0, before the expansion, and at T1, 6 months after the end of the RME therapy. The results obtained are evaluated using two programs: Simplant and Delta-Dent. All of the analyses were performed by the same operator. Both programs reported statistically significant differences between the pre- and post-expansion values of the parameters on the transverse plane. On the vertical plane, only posterior facial height showed a statistically relevant variation. Both programs underlined a discrepancy between the pre- and post-expansion infraorbital and mental foramina distance values; however, this difference was considered statistically significant by Delta-Dent, and not by Simplant. CBCT is a reliable and effective tool for orthodontic diagnosis and treatment planning. Both of the evaluated programs are efficient in tridimensional cephalometric analysis.

Reliability of Tooth Width Measurements Delivered by the Clin-Check Pro 6.0 Software on Digital Casts: A Cross-Sectional Study

The purpose of this study was to assess the accuracy and reliability of tooth width measurements and Bolton Indices delivered by the Clin-Check Pro 6.0 software (Align Technology, San José, CA, USA). Fifty-four plaster casts were selected and measured with a manual calliper by a trained and calibrated observer. The data gathered were compared with those delivered by the software on the corresponding fifty-four virtual casts. The method reliability of the software was assessed by comparing the measurements performed by the software on 201 pairs of clin-checks corresponding to two consecutive treatment phases. Accuracy and reliability were statistically assessed using a mixed model. The software tends to provide larger widths compared with the manual method. Statistically significant differences were found in 23 teeth. At a global level, the mean difference between the methods was −0.19 mm, with a Dahlberg error of 0.24 mm and an intraclass correlation coefficient of 0.98. The Bolton Indices delivered by the two methods had a moderate correlation (ICC = 0.59; 0.69). The within method reliability of the software was extremely high. Tooth width measurements delivered by the software, despite the positive bias, can be considered accurate and clinically acceptable for all teeth except molars. The Bolton Indices made available by the software are not accurate and clinically acceptable, especially in the case of mandibular excess.

Comparison between stone and digital cast measurements in mixed dentition : Validity, reliability, reproducibility, and objectivity

Purpose

To 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.

Methods

Pairs 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.

Results

Significant (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.

Conclusion

Measurements 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.

Evaluation of the accuracy of orthodontic models prototyped with entry-level LCD-based 3D printers: a study using surface-based superimposition and deviation analysis

OBJECTIVES

The objective of this study was to evaluate the accuracy of dental models prototyped via entry-level liquid crystal display (LCD) 3D printers.

MATERIALS AND METHODS

Identical prototyped models were generated from a master digital file testing two entry-level LCD-based 3D printers and using one professional-grade 3D printer as gold standard (GS), with 50-µm and 100-µm layer thickness. Each 3D-printed model was scanned, and a specific 3D technology was used to perform surface-based superimposition and deviation analysis to evaluate trueness and precision. The distances between surface points of two superimposed models were converted to root mean square (RMS) and statistically analyzed.

RESULTS

The RMS values detected were significantly higher in dental models prototyped with entry-level compared to the SLA printer (p < 0.001), in terms of trueness (50 µm: GS 0.075 mm, LCD1 0.192 mm, LCD2 0.179 mm; 100 µm: GS 0.066 mm, LCD1 0.209 mm, LCD2 0.199 mm) and precision (50 µm: GS 0.028 mm, LCD1 0.075 mm, LCD2 0.085 mm; 100 µm: GS 0.039 mm, LCD1 0.096 mm, LCD2 0.101 mm). No significant differences were found between the values of RMS of both entry-level 3D printers (p > 0.05). Layer thickness did not affect either the trueness or precision of the 3D-printed models (p > 0.05).

CONCLUSION

Entry-level LCD-based 3D printers are not as accurate as professional-grade 3D printer, but still close to orthodontics clinical threshold values.

CLINICAL RELEVANCE

Clinicians should evaluate the intended application of 3D-printed orthodontic models before using entry-level 3D printers.

Digital (R)Evolution: Open-Source Softwares for Orthodontics

Among the innovations that have changed modern orthodontics, the introduction of new digital technologies in daily clinical practice has had a major impact, in particular the use of 3D models of dental arches. The possibility for direct 3D capture of arches using intraoral scanners has brought many clinicians closer to the digital world. The digital revolution of orthodontic practice requires both hardware components and dedicated software for the analysis of STL models and all other files generated by the digital workflow. However, there are some negative aspects, including the need for the clinician and technicians to learn how to use new software. In this context, we can distinguish two main software types: dedicated software (i.e., developed by orthodontic companies) and open-source software. Dedicated software tend to have a much more user-friendly interface, and be easier to use and more intuitive, due to being designed and developed for a non-expert user, but very high rental or purchase costs are an issue. Therefore, younger clinicians with more extensive digital skills have begun to look with increasing interest at open-source software. The aim of the present study was to present and discuss some of the best-known open-source software for analysis of 3D models and the creation of orthodontic devices: Blue Sky Plan, MeshMixer, ViewBox, and Blender.

Reliability and accuracy of automatic segmentation of mandibular 3D models on linear measurements

OBJECTIVE

Evaluate if automatic segmentation of mandibular three-dimensional (3D) models is reliable and accurate.

MATERIALS AND METHODS

Eight dry mandibles with eight silica markers were scanned in the i-CAT Classic device (Imaging Sciences International). Automatic segmentation was performed using nine standard preset thresholds in the Dolphin software (Dolphin Imaging & Management Solutions). Three observers individually made twice eight linear measurements on the mandibular 3D models. Another observer made physical measurements, twice as well, on the dry mandibles. Reliability and accuracy were evaluated with intraclass correlation coefficients (ICCs), Dahlberg's formula, Bland-Altman analyses, and changing bias with regression analyses.

RESULTS

Inter-observer and intra-observer ICCs and Dahlberg's error were ≥ 0.75 and ≤ 1.0 mm, respectively, for all measurements. Inter-observer agreement between mandibular 3D models and physical measurements ranged from -0.37 to 0.91 mm.

CONCLUSIONS

Linear measurements made on mandibular 3D models obtained using standard preset thresholds are reliable and accurate. However, additional studies are necessary to confirm this hypothesis for clinical applications.

CLINICAL RELEVANCE

Since the 3D models are useful for diagnostics and surgical planning, it is necessary to determinate whether the linear measurements made on 3D models obtained by automatic segmentation are sufficiently reliable and accurate.

Accuracy of intraoral scan images in full arch with orthodontic brackets: a retrospective in vivo study

Objectives

The purpose of this retrospective study was to evaluate the accuracy of intraoral scan (IOS) images in the maxillary and mandibular arches with orthodontic brackets.

Material and methods

From digital impressions of 140 patients who underwent orthodontic treatment, consecutive IOS images were selected based on standardized inclusion criteria: Two pre-orthodontic IOS images (IOS1 and IOS2) of permanent dentition with fully erupted second molars and IOS images obtained immediately after orthodontic bracket bonding (IOSb). Superimpositions were performed to evaluate the reproducibility of repeated IOS images. Accuracy of IOSb images was analyzed by comparing the average surface errors between IOS1c and IOS2c images, which were IOS images cut based on the same region of the interest as between IOS1 and IOSb images.

Results

A total of 84 IOS images was analyzed. The average surface errors between IOS1 and IOS2 images were 57 ± 8 μm and 59 ± 14 μm in the maxillary and mandibular arch, respectively, and their reliability was almost perfect. The average errors between IOSb and IOS1c images exhibited an increase, which measured 97 ± 28 μm in the maxillary arch and 95 ± 29 μm in the mandibular arch. These surface deviations between IOSb and IOS1c images were significantly larger in each region as well as entire dentition (P < 0.001) compared to those between IOS1c and IOS2c images.

Conclusions

The average surface errors of the scans with brackets showed increased values compared with those without brackets. This suggests that orthodontic brackets could affect the trueness of intraoral scan images.

Clinical relevance

It is necessary for clinicians to consider the effect of brackets on digital impression when using IOS images in orthodontic patients.

Side effects of twistflex retainers-3D evaluation of tooth movement after retainer debonding

PURPOSE

Evaluation of tooth movement after retainer debonding in retainer-associated misalignment cases.

METHODS

This pilot study is based on a retrospective data analysis. Adult patients (age 25.5 ± 4.9 years) wearing fixed twistflex retainers and having visible retainer-associated misalignment were included and examined for tooth movement after retainer debonding. Orthodontic study models were taken at retainer debonding (t0) and 14 (±1) weeks later (t1). They were digitally superimposed using 2D/3D dental imaging software and tooth movement was analyzed in all three dimensions.

RESULTS

A total of 23 teeth (12 upper teeth: 10 incisors, 2 canines; 11 lower teeth: 7 incisors, 4 canines) were analyzed. Mean overall tipping was 1.11 ± 0.82° in the mesial/distal direction (angulation, x‑axis), 2.02 ± 1.9° in the buccal/lingual direction (inclination, y‑axis) and 1.28 ± 0.99° around the tooth axis (z-axis). Mean overall bodily movement was 0.30 ± 0.31 mm in the mesial/distal direction (angulation, x‑axis), 0.10 ± 0.13 mm in the buccal/lingual direction (inclination, y‑axis), and mean in- or extrusion 0.22 ± 0.24 mm (z-axis). Mean tipping and bodily movement were more pronounced in the upper jaw.

CONCLUSION

The present data shows that tooth movement after debonding of twistflex retainers can be expected in misalignment cases.

Accuracy of fully guided orthodontic mini-implant placement evaluated by cone-beam computed tomography: a study involving human cadaver heads

OBJECTIVES

The aim of this study was to evaluate the accuracy of fully guided orthodontic mini-implant (OMI) placements supported by tooth- (TBGs) or gingiva-borne silicone guides (GBGs) based on virtually superimposed lateral cephalograms on virtual plaster models.

MATERIALS AND METHODS

Lateral cephalograms and corresponding plaster models were virtually superimposed for the planning of OMI positions; fully guided TBGs and GBGs were fabricated (each, n = 10). A total of 40 OMIs were inserted in a paramedian position into the palate of 20 human cadavers. Postoperative cone-beam computer tomographies (CBCTs) were carried out, and an accuracy evaluation was performed by comparing preoperative planning models and postoperative CBCTs. Deviations of the axis, tip, centre of the shoulder and vertical position of each of the implants were evaluated. Furthermore, the transfer accuracy measured by postoperative CBCT scans were compared with the accuracy determined using an intraoral scanner.

RESULTS

A significant deviation between TBGs (2.81° SD 2.69) and GBGs (6.22° SD 4.26) regarding implant angulation was evaluated (p = 0.005). Implant tip and implant shoulder deviations revealed no statistical differences between the guides. Accuracy values of oral scans regarding vertical deviations were significantly more inaccurate when compared with CBCTs (p < 0.001).

CONCLUSIONS

The accuracy of an OMI position can be significantly increased by using a guide extension over the teeth. Vertical implant positions presented the lowest deviations. Postoperative oral scans and CBCTs represent diverging accuracy measurements when compared with virtual planning.

CLINICAL RELEVANCE

Users must keep in mind that despite virtual planning deviations, inaccuracies of a few millimetres may occur.

The effect of regular dental cast artifacts on the 3D superimposition of serial digital maxillary dental models

Superimpositions of serial 3D dental surface models comprise a powerful tool to assess morphological changes due to growth, treatment, or pathology. In this study, we evaluated the effect of artifacts on the superimposition outcome, using standard model acquisition and superimposition techniques. Ten pre- and post-orthodontic treatment plaster models were scanned with an intraoral scanner and superimposed using the iterative closest point algorithm. We repeated the whole process after manual removal of plaster artifacts, according to the current practice, as well as after re-scanning the cleaned models, to assess the effect of the model acquisition process derived artifacts on the superimposition outcome. Non-parametric multivariate models showed no mean effect on accuracy and precision by software settings, cleaning status (artifact removal), or time point. The choice of the superimposition reference area was the only factor that affected the measurements. However, assessment of individual cases revealed significant differences on the detected tooth movement, depending on artifact removal and on the model acquisition process. The effects of all factors tended to decrease with an increase in the size of the superimposition reference area. The present findings highlight the importance of accurate, artifact-free models, for valid assessment of morphological changes through serial 3D model superimpositions.

Reliability and intra-examiner agreement of orthodontic model analysis with a digital caliper on plaster and printed dental models

OBJECTIVE

To investigate if orthodontic model analysis with a digital caliper can be interchangeably performed between plaster and printed dental models.

MATERIALS AND METHODS

Forty-eight plaster models were digitized with orthoX®scan (DENTAURUM) and 48 counterparts were printed with Objet30 Dental Prime (Stratasys). One examiner performed five repeated orthodontic model analyses (41 outcomes) with a digital caliper in each plaster and the corresponding printed model and was externally validated by a second examiner. Inter- and intra-examiner reliability and error were evaluated with intraclass correlation coefficients (ICCs) and Dahlberg's formula, intra-examiner agreement with Bland-Altman analyses and Lin's correlation coefficients (CCCs), and changing bias with regression analyses.

RESULTS

Inter- and intra-examiner ICCs and Dahlberg's error were ≥ 0.75 and ≤ 0.5 mm, respectively, for most outcomes in both plaster and printed models. Intra-examiner agreement (systematic bias) between plaster and printed models ranged from - 0.45 to 0.45 mm. Ranges of limits of agreement were wide for cumulative outcomes, such as crowding maxilla and mandible (2.69 mm and 3.07 mm around zero, respectively). Tooth widths were measured slightly larger in printed models. Lin's CCCs were ≥ 0.87 for all the outcomes between plaster and printed models, while no changing bias was detected.

CONCLUSION

If orthodontic model analyses are consistently performed, plaster casts and their corresponding printed models obtained with orthoX®scan and Objet30 Dental Prime can be interchangeably used for clinical purposes in orthodontics.

CLINICAL RELEVANCE

Orthodontic model analysis is important in treatment planning and printed dental models need to be validated regarding this diagnostic procedure.

Conformity, reliability and validity of digital dental models created by clinical intraoral scanning and extraoral plaster model digitization workflows

BACKGROUND

In dentistry, digitization of dental arches with intraoral scanners could one day replace impressions and plaster model digitization processes, if accuracy is clinically sufficient. This study aimed to assess the reliability, validity and conformity of an intraoral scanning procedure (Lythos^©, Ormco) and of two extraoral digitization workflows via alginate impression and plaster model scanning with the D810^© (3shape) or the Atos II Triple Scan^© (GOM) under clinical conditions.

METHODS

In 20 subjects three consecutive intraoral scans, three alginate and one reference polyether impression were taken of both the upper and lower dental arch, respectively. The digital models created from the corresponding plaster models and the intraoral scans were superimposed with the polyether reference standard by both a global and a local best-fit algorithm. Reliability, validity and conformity of the three digital workflows were assessed via intraclass (ICC) and Lin's concordance correlation coefficients (CCC) as well as analyses according to Bland-Altman.

RESULTS

The digital models created from the intraoral scanning procedure were less in agreement with the polyether reference (validity) than those from the extraoral procedures with reduced conformity and reliability. Local numerical deviations from the reference standard were approximately twice as high compared to the extraoral procedures, which showed high conformity and were equivalent and clinically acceptable in terms of reliability and validity.

CONCLUSIONS

Although the intraoral scanning method with Lythos^© seems to have drawbacks in terms of reliability, validity and conformity to the indirect alginate methods, all procedures proved to be clinically equivalent for diagnostic purposes.