The holodent system, a new technique for measurement and storage of dental casts

Comparison of Dental Stone Models and Their 3D Printed Acrylic Replicas for the Accuracy and Mechanical Properties

This study was conducted to test possibilities of application of 3D printed dental models (DMs) in terms of their accuracy and physical properties. In this work, stone models of mandibles were cast from alginate impressions of 10 patients and scanned in order to obtain 3D printed acrylic replicas. The diagnostic value was tested as matching of model scans on three levels: peak of cusps, occlusal surface, and all teeth surfaces. The mechanical properties of acrylic and stone samples, specifically the impact strength, shore D hardness, and flexural and compressive strength were investigated according to ISO standards. The matching of models' surfaces was the highest on the level of peaks of cusps (average lack of deviations, 0.21 mm) and the lowest on the level of all teeth surfaces (average lack of deviations, 0.64 mm). Acrylic samples subjected to mechanical testing, as expected, showed higher mechanical properties as compared to the specimens made of dental stone. In the present study we demonstrated that 3D printed acrylic models could be ideal representatives in the case of use as a diagnostic tool and as a part of medical records. The acrylic samples exhibited not only higher mechanical properties, but also showed better accuracy comparing to dental stone.

Asymmetric dental arch treatment with Forsus fatigue appliances: Long-term results

OBJECTIVES

To investigate the treatment efficacy and follow-up stability of the asymmetric Forsus appliance by evaluating longitudinal changes in dental arch asymmetry on digital dental models from 21 patients.

MATERIALS AND METHODS

Maxillary and mandibular reference lines were used for measurements of intra-arch asymmetry at pretreatment (T1), posttreatment (T2), and 4.2 years after treatment (T3). Maxillary and mandibular measurements were performed relative to the dental midline and anterior reference line on digital dental models. To determine the amount of asymmetry between the Class I and Class II sides of a given arch, all maxillary and mandibular parameters were measured on each side of the model separately. Repeated-measures analysis of variance/paired sample t-tests were performed to evaluate dental arch asymmetries at the P < .05 level.

RESULTS

The alveolar transverse dimensions of the posterior segment of both arches were increased during treatment (P < .05) and remained stable during the retention period. Class II subdivision malocclusion was caused by distal positioning of the mandibular canine, premolars, and first molar on the Class II side (P < .05). Asymmetry was resolved by treatment with asymmetric Forsus appliances. The resolved asymmetry remained stable over the long term. There were no significant differences between T2 and T3 (P > .05).

CONCLUSIONS

The asymmetric Forsus appliance can be used to treat dental arch asymmetry in patients with Class II subdivision malocclusions.

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.

Bolton tooth size ratio among qatari population sample: An odontometric study

Objectives:

To establish the overall and anterior Bolton ratio among a sample of Qatari population and to investigate whether there is a difference between males and females, as well as to compare the result obtained by Bolton.

Materials and Methods:

The current study consisted of 100 orthodontic study participants (50 males and 50 females) with different malocclusions and age ranging between 15 and 20 years. An electronic digital caliper was used to measure the mesiodistal tooth width of all maxillary and mandibular permanent teeth except second and third molars. The Student's t-test was used to compare tooth-size ratios between males and females and between the results of the present study and Bolton's result.

Results:

The anterior and overall ratio in Qatari individuals were 78.6 ± 3.4 and 91.8 ± 3.1, respectively. The tooth size ratios were slightly greater in males than that in females, however, the differences were not statistically significant (P > 0.05). There were no significant differences in the overall ratio between Qatari individuals and Bolton's results (P > 0.05), whereas statistical significant differences were observed in anterior ratio (P = 0.007).

Conclusions:

Within the limitation of the limitations of the present study, definite conclusion was difficult to establish. Thus, a further study with a large sample in each malocclusion group is required.

Bolton tooth size ratio among Sudanese Population sample: A preliminary study

Background:

The study of the mesiodistal size, the morphology of teeth and dental arch may play an important role in clinical dentistry, as well as other sciences such as Forensic Dentistry and Anthropology.

Aims:

The aims of the present study were to establish tooth-size ratio in Sudanese sample with Class I normal occlusion, to compare the tooth-size ratio between the present study and Bolton's study and between genders.

Materials and Methods:

The sample consisted of dental casts of 60 subjects (30 males and 30 females). Bolton formula was used to compute the overall and anterior ratio. The correlation coefficient between the anterior ratio and overall ratio was tested, and Student's t-test was used to compare tooth-size ratios between males and females, and between the present study and Bolton's result.

Results:

The results of the overall and anterior ratio was relatively similar to the mean values reported by Bolton, and there were no statistically significant differences between the mean values of the anterior ratio and the overall ratio between males and females. The correlation coefficient was (r = 0.79).

Conclusions:

The result obtained was similar to the Caucasian race. However, the reality indicates that the Sudanese population consisted of different racial groups; therefore, the firm conclusion is difficult to draw. Since this sample is not representative for the Sudanese population, hence, a further study with a large sample collected from the different parts of the Sudan is required.

Longitudinal evaluation of dental arch asymmetry in Class II subdivision malocclusion with 3-dimensional digital models

INTRODUCTION

Class II subdivision malocclusions with their asymmetric occlusal relationships often pose treatment difficulties. The aim of this study was to evaluate the longitudinal changes of dental arch asymmetry in untreated subjects with Class II subdivision malocclusion.

METHODS

From 706 files from the University of Michigan Growth Study, longitudinal records of 17 untreated subjects with Class II subdivision malocclusion were included this study. Dental arch changes at 3 consecutive longitudinal intervals, defined by the cervical vertebral maturation method, were analyzed on digital dental models. The average ages of the subjects were 12.4, 15.1, and 19.1 years at the 3 time periods, respectively. Maxillary and mandibular reference lines were constructed and used for the intra-arch asymmetry measurements. The Friedman test and analysis of variance with repeated measures were used to determine dental arch asymmetries at the P <0.05 level.

RESULTS

All subjects were found to have a type 1 Class II subdivision malocclusion characterized by distal positioning of the mandibular first molar on the Class II side. No statistically significant intra-arch asymmetry changes were found for the maxillary and mandibular dental arches in any time period. Between the baseline and the final follow-up, the data indicated decreases in maxillary and mandibular intercanine arch widths and arch lengths symmetrically.

CONCLUSIONS

The results of this study indicate that the dental arch asymmetry in patients with Class II subdivision malocclusions did not improve or worsen with growth.

Comparison of Bolton analysis and tooth size measurements obtained using conventional and three-dimensional orthodontic models

Objectives:

The aim of this study was to compare the accuracy, reproducibility, efficacy and effectiveness of measurements obtained using digital models with those obtained using plaster models.

Materials and Methods:

A total of 20 digital models were produced by the Ortho Three-dimensional Models (O3DM) Laboratory and their software (O3DM version 2) was used to obtain measurements. Identical plaster models were used to obtain measurements of teeth with a vernier caliper. The maximum mesiodistal width of each study model, from first molar to first molar, was measured. All measurements were repeated at least 1 month later by the same operator for both digital and manual methods. The data were analyzed using Cronbach α, Wilcoxon signed rank test and the McNemar test.

Results:

Cronbach α value of the data at T1 and T2 for 6 anterior and 12 overall teeth measured using the two methods was very close to the ideal value of 1, indicating high intra-observer reliability. The Wilcoxon signed rank test showed statistically significant differences between the two methods (P = 0.000, P < 0.001). The measurements obtained using the digital models were lower than those obtained using the plaster models. No statistically significant differences were found between the two methods for anterior Bolton discrepancies (P = 0.375) or overall Bolton discrepancies (P = 0.00). Paired comparisons of repeated measurements for Bolton ratios showed no statistically significant differences for anterior or overall Bolton discrepancies (P = 0.688 and P = 0.375, respectively).

Conclusions:

Use of O3DM software is an acceptable alternative to the traditional vernier caliper method in orthodontic practice.

Reproducibility, reliability and validity of measurements obtained from Cecile3 digital models

The aim of this study was to determine the reproducibility, reliability and validity of measurements in digital models compared to plaster models. Fifteen pairs of plaster models were obtained from orthodontic patients with permanent dentition before treatment. These were digitized to be evaluated with the program Cécile3 v2.554.2 beta. Two examiners measured three times the mesiodistal width of all the teeth present, intercanine, interpremolar and intermolar distances, overjet and overbite. The plaster models were measured using a digital vernier. The t-Student test for paired samples and interclass correlation coefficient (ICC) were used for statistical analysis. The ICC of the digital models were 0.84 +/- 0.15 (intra-examiner) and 0.80 +/- 0.19 (inter-examiner). The average mean difference of the digital models was 0.23 +/- 0.14 and 0.24 +/- 0.11 for each examiner, respectively. When the two types of measurements were compared, the values obtained from the digital models were lower than those obtained from the plaster models (p < 0.05), although the differences were considered clinically insignificant (differences < 0.1 mm). The Cécile digital models are a clinically acceptable alternative for use in Orthodontics.

The Relationship between Digital Model Accuracy and Time-Dependent Deformation of Alginate Impressions

Objectives: To investigate the effects of different storage periods of alginate impressions on digital model accuracy.

Materials and Methods: A total of 105 impressions were taken from a master model with three different brands of alginates and were poured into stone models in five different storage periods. In all, 21 stone models were poured and immediately were scanned, and 21 digital models were prepared. The remaining 84 impressions were poured after 1, 2, 3, and 4 days, respectively. Five linear measurements were made by three researchers on the master model, the stone models, and the digital models. Time-dependent deformation of alginate impressions at different storage periods and the accuracy of traditional stone models and digital models were evaluated separately.

Results: Both the stone models and the digital models were highly correlated with the master model. Significant deformities in the alginate impressions were noted at different storage periods of 1 to 4 days. Alginate impressions of different brands also showed significant differences between each other on the first, third, and fourth days.

Conclusions: Digital orthodontic models are as reliable as traditional stone models and probably will become the standard for orthodontic clinical use. Storing alginate impressions in sealed plastic bags for up to 4 days caused statistically significant deformation of alginate impressions, but the magnitude of these deformations did not appear to be clinically relevant and had no adverse effect on digital modeling.

OrthoCAD: digital models for a digital era

This article describes the use of OrthoCAD--a digital study model capture, assessment and storage system. It is estimated that approximately 10% of orthodontists in USA and Canada now utilize digital study models, and improving technology is making it increasingly popular worldwide. The technology behind digital study models is briefly reviewed. The OrthoCAD system is described, and the advantages and disadvantages of using digital study models are highlighted.

Comparison of measurements made on digital and plaster models

Measuring plaster models by hand is the traditional method of assessing malocclusion. Recent technologic advances now allow the models to be digitized, measured with software tools, stored electronically, and retrieved with a computer. OrthoCAD (Cadent, Fairview, NJ) performs this service. The purpose of this study was to evaluate the reliability of the OrthoCAD system. Two independent examiners measured tooth size, overbite, and overjet on both digital and plaster models. The results were compared, and interexaminer reliability was assessed. The study sample consisted of 76 randomly selected pretreatment patients. The results showed a statistically significant difference between the 2 groups for tooth size and overbite, with the digital measurements smaller than the manual measurements. However, the magnitude of these differences ranged from 0.16 mm to 0.49 mm and can be considered clinically not relevant. No difference was found between the 2 groups in the measurement of overjet. Interexaminer reliability was consistent for both the plaster and the digital models.

Construction and testing of a computer-based intraoral laser scanner for determining tooth positions

An optical set-up for intraoral data acquisition based on the principle of laser triangulation was developed. The system consists of a pig-tailed laser with line generating optics, a stepping motor driven positioning stage, a commercial CCD (charge coupled device) camera system with frame grabber interface, a control personal computer and a mirror system compensating for the fact that there is no possibility of watching an object directly in the mouth under a certain angle except from a facial position during intraoral scanning. Due to the size of the prototype measurements were still restricted to plaster casts. In order to evaluate its accuracy, the measurements were compared with those taken with a commercial laser scanner and a coordinate measurement table. The accuracy of the prototype scanner was determined to be DeltaXYZ=0.04 mm using gauge blocks of given dimensions and proved to range between the commercial laser scanner and the coordinate measurement table (i.e., it was slightly better than that of the commercial scanner). Applications in orthodontics were demonstrated by scanning plaster casts and measuring distances on reconstructed surfaces. The measured distances showed a maximum deviation of about +/-0.2 mm compared with the data of the coordinate measurement table, which served as a reference. In addition, reconstruction of three-dimensional tooth movements was performed on the scan data. The translational and rotational parameters gained from the superimposition of scanned point clouds and describing tooth movement were also in good accordance with the reference. The achieved accuracy proved to be sufficient for further development which should include a reduction in size and the use of more precise device components.

A three-dimensional photographic method for documentation and measurement of dental conditions

A 3-D photographic technique was developed for the registration of bite conditions. This technique may replace plaster models for archiving purposes. To achieve this, photographic equipment and computer programs should be user friendly, not too expensive, and allow measurements that satisfy scientific demands. This purpose was fulfilled by combining the following elements: a photographic unit with standardized conditions for 3-D photography and a reference object with known coordinates where bite impressions or models are placed during photography. To reconstruct 3-D coordinates from photographs these are placed on a digitizer connected to a computer programmed for reconstructing 3-D coordinates from the digitized 2-D data. The accuracy of the 3-D reconstruction of coordinates, x, y, z, was tested by means of 3-D photographs of a test object with reference points having a precision of +/- 0.5 micron. The mean error for distances of 5 mm and 15 mm varied between -0.17 mm and +0.15 mm. Measurements of 45 degrees and 90 degrees angles had an accuracy that varied from -0.5 degree to +0.9 degree and from -1.2 degrees to +1.5 degrees respectively. An angle between lines and a plane of 54.7 degrees displayed a mean error of +/- 1.6 degrees. The test of the accuracy of the 3-D photographic technique for calculating distances and angles demonstrated that it fulfills demands for scientific applications on clinical material.

Accuracy of orthodontic force and tooth movement measurements

This study was designed to test the accuracy of measurement methods for assessment of force and tooth movement in orthodontic procedures. Daily in vivo measurements of the force produced by activated archwires showed that the initial force declined substantially (by 20 per cent of mean value) within 3 days. Both the 'trueness' (validity) and precision of the force measurements, obtained with a strain gauge, were found to be high (SD values were 1.0 cN and 0.4 cN, respectively). Horizontal tooth movements were measured with three different instruments: a slide calliper, a co-ordinate measuring machine, and laser measuring equipment based on holograms. There was a good level of agreement between these methods. This was also confirmed by calibration data. The precision of the methods was (SD values) 0.06, 0.07, and 0.13 mm, respectively. The benefits of the use of the co-ordinate measuring machine are obvious, since it can measure tooth movements in relation to reference planes in all directions.