Measuring 3-dimensional tooth movement with a 3-dimensional surface laser scanner

Biomechanical model registration for monitoring and simulating large orthodontic tooth movements in the maxilla and mandible

PURPOSE

Superimposition of digital dental-arch models allows quantification of orthodontic tooth movements (OTM). Currently, this procedure requires stable reference surfaces usually only present in the maxilla. This study aimed to investigate the accuracy of a novel superimposition approach based on biomechanical principles of OTM and the equilibrium of forces and moments (EFM)-applicable in both jaws-for monitoring and simulating large OTM.

METHODS

The study included 7 patients who had undergone extraction of the first (PM1-Ex) or second (PM2-Ex) premolar in each quadrant. Digital models taken at start and end of the T‑Loop treatment phase were superimposed by applying 3 EFM variants differing in the number of teeth used for registration. Maxillary OTM results for EFM were validated against those for a conventional surface registration method (SRM). In an additional case study, OTM were simulated for PM1-Ex, PM2-Ex and non-extraction treatment strategies.

RESULTS

The EFM variant that included all teeth of the dental arch achieved the highest accuracy, with median translational and rotational OTM deviations from SRM of only 0.37 mm and 0.56°, respectively. On average, retracted canines and first premolars were distalized by 3.0 mm, accompanied by 6.2° distal crown tipping and 12.2° distorotation. The share of space closure by molar mesialization was 19.4% for PM1-Ex quadrants and 34.5% for PM2-Ex quadrants.

CONCLUSION

EFM allows accurate OTM quantification relative to the maxillary and mandibular bases even in challenging situations involving large OTM. Superimposition of malocclusion and setup models enables realistic simulation of final tooth positions. This may greatly enhance the value of digital setups for decision-making in orthodontic treatment planning.

Methods of measuring distal canine movement and rotation- A review

This article provides an overview of the various methods for measuring distal canine movement and rotation during retraction. Various databases, including PubMed Central, Science Direct, Wiley Online Library, the Cochrane Library, Textbooks, Google Scholar, and Research Gate, and a manual search up until September 2022, were used to search for various methods of measuring distal canine movement and rotation during retraction. After excluding the duplicate articles, the papers explaining these techniques were included. Four significant techniques were identified. The digital method with 3D superimposition is the safest, most accurate, and most accessible of the methods reviewed.

Comparison of 2 different wear protocols of vacuum-formed retainers with respect to the conventional parameters and 3-dimensional superimpositional analysis

INTRODUCTION

This study aimed to compare the effectiveness of 2 different wear protocols of vacuum-formed retainers (VFR) in terms of angular and linear displacement of teeth using 3-dimensional (3D) superimpositional analysis and conventional model parameters.

METHODS

The study was conducted on 2 groups, each consisting of 17 patients randomly assigned to the part-time group or full-time group of VFR wearing after a nonextraction treatment. While conventional model measurements were assessed on 3D dental casts, 3D tooth movements were evaluated by digitally superimposed scans of casts acquired at 4-time points (debonding and 1, 3, and 6 months after debonding). Regarding conventional parameters, the difference between time-dependent changes among the groups was tested using the nonparametric Brunner-Langer and parametric linear mixed models. Considering 3D measurements, comparisons of groups were made using the Student t tests.

RESULTS

There were no significant intergroup differences regarding conventional model parameters at any time (P >0.05). Significant intergroup differences were observed regarding angular and linear relapses in the labiolingual direction for maxillary and mandibular incisors, as well as the rotational relapses for maxillary left canine and mandibular right lateral incisor, which were greater in the part-time group in the first month and at the end of 6 months (P <0.05).

CONCLUSIONS

Conventional model parameters appear to play a debatable role in evaluating the effectiveness of a retainer wear regimen. Three-dimensional analysis of tooth movements revealed that part-time VFR wear was less effective in retaining labiolingual and rotational tooth movements for the first month after debonding.

Clinical implementation of axial angulation of incisors in the course of routine fixed appliance treatment - a retrospective cohort study

PURPOSE

To identify clinically relevant factors for changes in axial angulation of incisors during routine fixed appliance orthodontic treatment.

METHODS

A total of 106 patients (grades 1-2 of IOTN, 64 females, 42 males; mean age: 15.5 years) from a private practice and treated with metal or ceramic brackets were included in this retrospective cohort study. The axial angulation of the upper and lower incisors was measured on lateral cephalograms before insertion of the first rectangular 0.016 × 0.022-in NiTi archwire (T0) and at the end of treatment about 8 weeks after insertion of the working 0.019 × 0.025-in stainless steel archwire (T1). Treatment-related changes according to bracket type, initial situation, premolar extraction, angle class, and skeletal vertical configuration were analyzed.

RESULTS

Although statistically significant treatment-related changes were seen for both the upper incisors (+ 1.3°) and the lower incisors (- 5.2°), only in ten patients (9.4%) was the prescribed torque value of 17° for the upper incisors and in no patient for the lower incisors achieved. A negative association between the induced change of axial angulation of incisors and the initial values was detected for the upper incisors as well as for the lower incisors. A comparison of the angle classes revealed significant differences in incisor changes. At the end of therapy, only a slight change for the upper central incisors in patients in angle class I cases and a significantly greater change in patients with angle class II/2 was observed. Cases with premolar extraction ended with lower axial angulation of the incisor than cases without extraction. The individual analysis of possible influencing factors also revealed an association with the vertical skeletal configuration.

CONCLUSIONS

For the first time, the presented data show clinically relevant influencing factors for incisor axial angulation changes of the upper and lower incisors in relation to the torque value of the applied brackets in the course of routine clinical practice. For the orthodontist, it remains mandatory to decide whether a customized system must be individualized in order to achieve individual therapy goals.

Exploring the mylohyoid area as a reference for three-dimensional digital mandibular superimposition

INTRODUCTION

the quantification of tooth movements should be obtained at different specific times and compared at different stages for every orthodontic treatment. These movements are generally measured on teleradiographs or casts. The use of Cone Beam Computed tomography (CBCT) for maxillary superimposition is clearly established in the literature, but not well defined for mandibular superimposition. This study aims to explore and evaluate the accuracy of the mylo-hyoid area as a reference for mandibular Digital Dental Cast (DDC) three-dimensional (3D) superimposition.

MATERIALS AND METHODS

the study compared mandibular 3D overlays with profile teleradiographs in 30 patients followed at Nice Saint Roch University Hospital. The molar and incisor coordinates on the 3D superimposition based on the mylo-hyoid area were compared to the ones on the 2D lateral cephalogram. Differences between the two methods of superimposition were assessed using paired t-tests.

RESULTS

No statistically significant difference was observed between the lateral cephalogram-based and mandibular DDC superimposition methods in 3D sagittal and vertical displacements of the lower first molars and central incisors.

CONCLUSION

The study showed the mylo-hyoid area to be an accurate superimposition landmark for the 3D evaluation of mandibular orthodontic tooth displacement. This method is also applicable for patients with conventional orthodontic treatment records. Other studies should be conducted on larger populations, subgroups (malocclusions, therapeutics) and on the use of an intra-oral camera.

Comparison of retraction efficacy of titanium-molybdenum and titanium-niobium alloy wires – A prospective split-mouth study

Objectives:

The study aimed to compare the efficacy of Titanium-Molybdenum (Ti-Mo) and Titanium-Niobium (Ti-Nb) alloy wires as retraction springs, by comparing: The amount and rate of canine retraction, the degree of canine rotation, the change in axial inclination of canines, and the associated anchorage loss.

Material and Methods:

All 17 participants (age: 18–25 years) to be treated with the first premolar extraction approach by canine retraction were assigned Ti-Mo and Ti-Nb alloy T-loop springs to either of the upper quadrants randomly. Digital intraoral 3-D scans and panoramic radiographs orthopantomagram (OPG) were taken before (T0) and after (T1) the study period (4 months). 3-D superimposition was performed and using the digital models and OPG, changes in canine position, angulation, and anchorage loss were compared between the two groups.

Results:

There was no significant difference between the two treatment groups for all the parameters pertaining to maxillary canine retraction, that is, canine retraction (P = 0.72), change in axial inclination of canines (P = 0.71), rotation of canines (P = 0.74), and anchorage loss (P = 0.13) as well as extraction space closure (P = 0.74).

Conclusion:

Ti-Nb and Ti-Mo alloy wires show a similar potency for use in retraction mechanics for orthodontic space closure.

Validation of three-dimensional digital model superimpositions based on palatal structures in patients with maximum anterior tooth retraction following premolar extraction

Objective

This study aimed to evaluate the superimposition accuracy of digital modes for measuring tooth movement in patients requiring anterior retraction after premolar extraction based on the proposed reference regions.

Methods

Forty patients treated with bilateral maxillary first premolar extraction were divided into two groups: moderate retraction (< 7.0 mm) and maximum retraction (≥ 7.0 mm). Central incisor displacement was measured using cephalometric superimpositions and three-dimensional (3D) digital superimpositions with the 3rd or 4th ruga as the reference point. The Wilcoxon signed-rank test and linear regression analyses were performed to test the significance of the differences and relationships between the two measurement techniques.

Results

In the moderate retraction group, the central incisor anteroposterior displacement values did not differ significantly between 3D digital and cephalometric superimpositions. However, in the maximum-retraction group, significant differences were observed between the anteroposterior displacement evaluated by the 3rd ruga superimposition and cephalometric methods (p < 0.05).

Conclusions

This study demonstrated that 3D digital superimpositions were clinically as reliable as cephalometric superimpositions in assessing tooth movements in patients requiring moderate retraction. However, the reference point should be carefully examined in patients who require maximum retraction.

Digital model superimpositions: are different software algorithms equally accurate in quantifying linear tooth movements?

Background

To evaluate the accuracy of three different 3D digital model registration software packages for linear tooth movement measurements, with reference to a 3D digital virtual setup (DS).

Methods

Twenty maxillary and mandibular pre-treatment scans of patients undergoing clear aligner therapy were used. Digital Setups were generated from pre-treatment scans using OrthoAnalyzer software. Both the pretreatment digital scans (T1) and Digital Setups (T2) were converted to STL files to be imported to the three studied software packages: Geomagic, OrthoAnalyzer and Compare. Linear changes in tooth positions were calculated for all the registered pairs.

Results

The change in tooth position was compared between the calculated tooth movement using each of the registration software packages versus the actual generated tooth movement from the Digital Setups. Continuous data was expressed as mean and standard deviation. Intraclass Correlation Coefficients for agreements between Digital Simulation and each software was used. Intra and Inter-examiner reliabilities were also assessed using Intraclass Correlation Coefficients. Significance of the obtained results was expressed at p ≤ 0.01. Geomagic software showed agreements > 0.90 for maxillary linear tooth movements and between 0.75 and 0.90 for mandibular measurements. OrthoAnalyzer software showed agreements between 0.50 and < 0.75 for maxillary and mandibular measurements. Compare software showed agreements > 0.90 for maxillary and mandibular linear tooth movements, indicating the best consistency.

Conclusions

Compare and Geomagic software packages consistently showed maximum accuracy in measuring the amount of tooth movement in the maxillary arch compared to the reference standard. Compare software showed the highest agreements in the mandibular arch. None of the three studied software packages showed poor agreement with the Digital Setup across all tooth movement measurements. Buccolingual tooth movements showed the highest agreements amongst linear measurements.

TIP, TORQUE & ROTATIONS: How accurately do digital superimposition software packages quantify tooth movement?

Background

To investigate the accuracy of three different 3D digital model registration software for tip, torque and rotation measurements, with reference to a 3D digital virtual setup. Twenty maxillary and mandibular pre-treatment scans of patients undergoing clear aligner therapy were used. Digital setups were generated from pre-treatment scans using a tooth movement software. Both the pretreatment digital scans (T1) and digital setups (T2) were converted to STL files to be exported to the 3 studied software that employed: (1) Semiautomatic best fit registration (S-BF), (2) Interactive surface-based registration (I-SB), and (3) Automatic best fit registration (A-BF) respectively. Changes in tip, torque and rotation were calculated for all the registered pairs.

Results

The change in tooth position was compared between the calculated tooth movement using each of the registration software packages versus the actual generated tooth movement from the digital setups. Continuous data was expressed as mean and standard deviation. Intra Class Correlation Coefficient for agreement between digital simulation and each software was used. Intra and Inter-examiner reliabilities were also assessed using Intra Class Correlation Coefficient. Significance of the obtained results was expressed at p ≤ 0.01. Semiautomatic best fit registration software showed excellent agreement (> 0.90) for all tooth movements, except for good agreement for torque (0.808). Interactive surface-based registration software showed moderate agreement for all measurements (0.50 and < 0.75), except for good agreement for rotation (0.783). Automatic best fit registration software demonstrated excellent agreement (> 0.90) for rotation, good agreement for tip (0.890) and moderate agreement for torque (0.740).

Conclusions

Overall, semiautomatic best fit registration software consistently showed excellent agreement in superimpositions compared to other software types. Automatic best fit registration software consistently demonstrated better agreement for mandibular superimpositions, compared to others. Accuracy of digital model superimpositions for tooth movements studied in superimposition studies, can be attributed to the algorithm employed for quantification.

Evaluation of the stability of the palatal rugae using the three-dimensional superimposition technique following orthodontic treatment

OBJECTIVES

To determine the uniqueness and stability of the palatal rugae after orthodontic treatment.

METHODS

Cast models of untreated subjects (n=50) were obtained twice at intervals of 8-30 months. Cast models of patients who received non-extraction (n=50) and extraction (n=50) orthodontic treatment were obtained before and after treatment at intervals of 11-41 months and 14-49 months, respectively. All 300 cast models were scanned digitally. The palatal rugae were manually extracted and transformed into 3D point clouds using reverse engineering software. An iterative closest point (ICP) registration algorithm based on correntropy was applied, and the minimum point-to-point root mean square (RMS) distances were calculated to analyze the deviation of palatal rugae for scans of the same subject (intrasubject deviation [ISD]) and between different subjects (between-subject deviation [BSD]). Differences in ISD between each group and the deviation between ISD and BSD of all 150 subjects were evaluated.

RESULTS

Significant differences were found in the 150 ISD and 1225 BSD in each group, as well as the 150 ISD and 11175 BSD across all groups. The mean values of ISD in untreated, non-extraction and extraction group were 0.178, 0.229 and 0.333 mm, respectively. When the first ruga was excluded in the extraction group, the mean ISD decreased to 0.241 mm, which was not significantly different from that in the non-extraction group (p=0.314).

CONCLUSIONS

Orthodontic treatment can influence the palatal rugae, especially in cases of extraction. Furthermore, variation mainly existed in the first ruga in cases of extraction. However, palatal rugae are still unique and may be used as a supplementary tool for individual identification.

CLINICAL SIGNIFICANCE

This study indicates that palatal rugae might be applied in the evaluation of orthodontic tooth movement and forensic individual identification. The registration algorithm based on correntropy provides a credible, precise, and convenient method for palatal rugae superimposition.

Comparison and reproducibility of three methods for maxillary digital dental model registration in open bite patients

OBJECTIVE

To compare and assess the reproducibility of 3 methods for registration of maxillary digital dental models in patients with anterior open bite. Settings and sample population Digital dental models of 16 children with an anterior open bite in the mixed dentition were obtained before (T1) and after 12 months of treatment with bonded spurs (T2).

METHODS

Landmarks were placed on all T2 models and 3 registration methods (R1, R2 and R3) were independently performed by 2 observers. R1 was based on 10 landmarks placed on posterior teeth. R2 was based on 5 landmarks on the palate (2 anterior, 2 posterior and 1 central). R3 used regions of interest around the 5 palatal landmarks used in R2. The differences between the registration methods were calculated by comparing the mean differences and standard deviations between the corresponding x, y and z coordinates of 6 corresponding landmarks in the T2 registered models. Repeated measures analysis of variance followed by post-hoc Bonferroni tests were used for comparisons (P < .05). The agreement between methods and the intra and interobserver reproducibility were assessed with Bland-Altman tests and intraclass correlation coefficients (ICC).

RESULTS

Comparisons of R2 with R3 methods showed greater agreement, mean differences ≤0.50 mm for all landmarks, than comparisons of R1 with R2, and R1 with R3, mean differences >0.50 mm for most of the y and z coordinates (P < .05). The R1 and R3 methods presented excellent intra and interobserver reproducibility and R2 method had moderate interobserver reproducibility.

CONCLUSIONS

Longitudinal assessments of open bite treatment using digital dental models could consider the posterior teeth and/or the palate as references. The R1 and R3 methods showed adequate reproducibility and yield different quantitative results. The choice will depend on the posterior teeth changes and dental models' characteristics.

Distal extension of palatal rugae as a limitation for donor soft tissue grafts in a Jordanian population: A cross-sectional study

Background

The purpose of the cross sectional study was to investigate the distal extension of the rugae area in a Jordanian (Middle Eastern) population, as an anatomical limitation influencing the surgical decision of harvesting a palatal soft tissue graft. Factors that may influence or predict the extension were also assessed.

Methods

Sixty periodontally healthy participants (29 males and 31 females) were included. Maxillary alginate impressions were made and casts were poured. The measurements were highlighted from the origin of the rugae (near mid palatine raphe) to the terminal end with a sharp graphite pencil on the cast and a magnification lens was used for identification. The most posterior extension of the rugae were marked on the casts and determined by a standardized periodontal probe. The normal approximation test for binomial distribution was used to determine the proportion of the subjects with rugael extensions beyond the mesial end of the upper second premolar and fisher’s exact test for the purpose of analysis of the association of this extension with other factors.

Results

In almost half (41.7%) of the sample, the rugae extended distal to the upper second premolar, 23.3% extended to the mid-palatal of the upper second premolar, and 11.7% extended to the mesial of the upper second premolar. The implication is that 90.0% of the rugae reached the upper second premolar and 78.3% extended beyond its mesial aspect. The normal approximation test performed with 95% CI with the "rugael extension proximal to the mesial end of the upper 2nd premolar" considered to be the "success" category revealed that the proportion of the subjects with rugael extensions proximal to the mesial end of the upper second premolar was significantly lower than the proportion beyond the mesial end of the upper second premolar (95% CI of 11.2–32.0%, p = .00001). There was no significant difference between gender, smoking status, gingival phenotype and palatal shape with the posterior extension of palatal rugae.

Conclusions

Palatal rugae in a sample of a Jordanian population extends beyond the mesial aspect of the upper second premolar which may cause a substantial limitation for graft harvesting from the palate. The hard palate of Jordanian patients may not be a reliable source of soft tissue grafts required for aesthetic mucogingival surgery. No significant association existed between the most posterior extent of palatal rugae and gender, gingival phenotype or palatal shape. Other possible sources should be explored.

Three-Dimensional Facial Anthropometric Analysis With and Without Landmark Labelling: Is There a Real Difference?

INTRODUCTION

The actual role of landmarks labeling before three-dimensional (3D) facial acquisition is still debated. In this study, several measurements were compared among textured labeled (TL), unlabeled (NL), and untextured (NTL) 3D facial models.

MATERIALS AND METHODS

The face of 50 subjects was acquired through stereophotogrammetry. Landmark coordinates were extracted from TL, NL, and NTL facial models, and 33 linear and angular measurements were calculated, together with surface area and volume. Accuracy of measurements among TL, NL, and NTL models was assessed through calculation of relative technical error of measurement (rTEM). The intra- and inter-observer errors for each type of facial model were calculated.

RESULTS

Intra- and inter-observer error of measurements increased passing from textured to NTL and NL 3D models. Average rTEMs between TL models, and NTL and NL models were 4.5 ± 2.6% and 4.7 ± 2.8%, respectively, almost all measurements being classified as "very good" or "good." Only for orbital height and its inclination, mandibular ramus length, nasal convexity, alar slope angle, and facial divergence, rTEM was classified as "moderate" or "poor."

CONCLUSIONS

Accuracy and precision of measurements decrease when landmarks are not previously labeled; attention must be taken when measurements have a low magnitude or involve landmarks requiring palpation.

Unilateral intrusion in a medically complex patient using an orthodontic mini-implant: A case report

Orthognathic surgery offers a predictable treatment option for patients with skeletal discrepancies and corresponding dental malocclusions. In cases where surgery is not advised due to significant medical co-morbidity, the orthodontist must approach the treatment using different mechanical modalities. Orthodontic mini-implants can be a valuable adjunct in these cases. We describe a case where a palatal mini-implant was used during orthodontic treatment in a patient with a complex capillary malformation, which precluded surgical correction.

Comparison of 3-dimensional postoperative dental movement in Class III surgical correction with and without presurgical orthodontic treatment

Background

Surgery-first approach (SFA) is an emerging concept that surgically reposition the jaw bones without presurgical orthodontic treatment phase. The study investigated 3D dental movement in the postoperative orthodontic phase with orthodontic-first (OF) and SFA in orthognathic surgery (OGS).

Methods

This study included consecutive 40 patients (20, SF group; 20, OF group) skeletal Class III who underwent 2-jaw OGS correction. The data of cone-beam computed tomography were acquired at 3 stages with the scan of dental models to replace the dentition of the craniofacial images; at before OGS (T0), 1 week after OGS (T1) and at the completion of treatment (T2). The skeletal changes were obtained by overall superimposition. The post-operative dental movement was measured by 3D regional superimposition between T1 and T2.

Results

There were no significant difference in the postsurgical orthodontic movement in both groups except significant upper and lower molars extrusion by 2 mm in the SF group. Both groups exhibited no significant difference in mandibular stability in sagittal and vertical directions. The amount of extrusion in the molars was correlated with a postoperative sagittal mandibular forward movement. The total treatment duration was significantly shorter 230 days in the SF group.

Conclusion

The completion of the orthodontic treatment after OGS in the SFA was mainly accomplished through molar extrusive movement in both arches. The surgical setup of dental occlusion with 4 mm posterior open bite could be corrected during the postsurgical orthodontics in SFA through molar extrusion. The dental occlusion outcome was no different between OF and SFA.

3D-analysis of unwanted tooth movements despite bonded orthodontic retainers: a pilot study

Background

Recently, reports of unwanted tooth movements despite intact orthodontic bonded retainers have increased. These movements are not subject to relapse but are classified as a new developed malocclusion. The aims of the present pilot study were to analyze the prevalence of unwanted tooth movements despite intact bonded cuspid-to-cuspid retainers and to identify possible predisposing factors.

Materials and methods

Plaster casts of all patients finishing orthodontic treatment during three consecutive years were assessed before treatment (T0), after multibracket appliance debonding (T1) and after two years of retention (T2). After multibracket appliance treatment, all patients received a cuspid-to-cuspid flexible spiral wire retainer bonded to each tooth of the retained segment in the upper and lower jaw. The study group (SG) consisted of 44 patients (16 male, 28 female) with tooth movements (T1–T2) of the retained segment despite intact bonded cuspid-to-cuspid retainer and the control group (CG) of 43 patients (19 male, 24 female) without unwanted tooth movements. The casts of the SG were digitized, superimposed and measured. Using the Chi-square test, Fisher´s exact test and Mann–Whitney-U-test (p < 0.05), mandibular plane angle, incisor proclination, oral dysfunctions or habits (T0) and intercanine distance, overjet and interincisal relationship (T0, T1, T2) were compared between SG and CG.

Results

The prevalence of patients with unwanted tooth movements in one or both jaws was 27.0%. Maxillary retainers were affected more often (20.9%) than mandibular retainers (14.1%). The median amount of tooth movements was 0 to 0.66 mm with large interindividual variations. Oral dysfunctions or habits at T0, such as a lack of interincisal contact at all time points, were associated with unwanted tooth movements.

Conclusion

Unwanted tooth movements occurred more often with maxillary than mandibular retainers. Patients with oral dysfunctions/habits and without interincisal contact had a higher prevalence of unwanted tooth movements.

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.

Superimposition of 3D maxillary digital models using open-source software

Historically, whether for research purposes or clinical monitoring, orthodontic evaluation of dental movements has been done using plaster study models and two dimensional (2D) radiographs. However, new frontiers for the diagnosis, planning and outcome assessment of orthodontic treatments have arisen, due to the revolutionary digital tools which enable a three dimensional (3D) computerized analysis of dental movements by means of digital models. However, the software for 3D analysis are often costly, resulting in limited access to orthodontists. The present study aims to describe, through a clinical case presented to the Brazilian Board of Orthodontics and Dentofacial Orthopedics, a method for the superimposition of maxillary digital models using an open-source software to evaluate dental movements.

Does anchorage loss differ with 0.018-inch and 0.022-inch slot bracket systems?

OBJECTIVES

To compare maxillary first molar anchorage loss between 0.018-inch and 0.022-inch slot fixed appliance systems.

MATERIALS AND METHODS

Patients requiring bilateral maxillary premolar extractions (n = 74) within a randomized clinical trial comparing the effectiveness of 0.018-inch and 0.022-inch slot MBT bracket systems (3M-Unitek, Monrovia, Calif) were included. Three-dimensional pre- and posttreatment digital models were landmarked and measured (R700 scanner and OrthoAnalyzer software, 3Shape, Copenhagen, Denmark). Anteroposterior position of the first molars was measured using the third medial rugae point as a reference. Anchorage loss (AL) represented the subtraction of the posttreatment distance from the pretreatment distance for both anchorage loss right (ALR) and left (ALL) sides. The values were then compared using a two-way analysis of variance.

RESULTS

There were 41 and 33 cases for the 0.018-inch and 0.022-inch bracket slot systems, respectively. The baseline characteristics were similar between groups, except for the presence or absence of anchorage devices (P = .050). For the total sample: 0.018-inch ALR = 3.86 mm, ALL = 3.30 mm and 0.022-inch ALR = 3.73 mm, ALL = 3.47 mm (P = .970). There was also no significant difference between the 0.018-inch and 0.022-inch groups when subjects with anchorage devices were excluded (P = .383).

CONCLUSIONS

Bracket slot size does not influence maxillary molar anchorage loss during orthodontic treatment.

Superimposition of maxillary digital models using the palatal rugae: Does ageing affect the reliability?

OBJECTIVES

The aim of this study was to evaluate the reliability of 3-dimensional maxillary dental changes using two methods of digital model superimposition.

SETTING AND SAMPLE POPULATION

The Department of Orthodontics of Bauru Dental School, University of São Paulo and University of Michigan Craniofacial Growth Center. Fifteen subjects with normal occlusion.

MATERIAL & METHODS

The sample was composed of digital study models of 15 normal occlusion subjects taken at 13 (T1), 18 (T2) and 60 years of age (T3). Using the software SlicerCMF 3.1, superimposition (registration) was conducted using 9 landmarks placed on the incisive papilla, second and third palatal rugae and 10 mm distal to the third palatal rugae. Two registration methods were compared: landmarks (LA) and regions of interest (ROI). Three-dimensional changes of landmarks on the buccal cusp tip of posterior teeth bilaterally and the incisal edge of the right central incisor were measured by three examiners. Intraclass correlation coefficients and Bland-Altman method evaluated intra- and inter-examiner agreements.

RESULTS

Good or excellent intra-examiner agreement was found for T1-T2 and T2-T3 measurements using both registration methods. Inter-examiner agreements were good to excellent for T1-T2 measurements and poor to fair for most T2-T3 measurements. Mean T1-T2 differences were less than 0.5 mm for most measurements.

CONCLUSION

Maxillary digital dental models of patients with normal occlusion superimposed on palatal rugae showed an adequate reliability for a 5-year interval comparison using landmarks or regions of interest. Lower than acceptable reproducibility using both superimposition methods was found for a 40-year interval comparison.

Analysis of the Morphological Characteristics of the Palatal Rugae for Three-Dimensional Superimposition of Digital Models in Korean Subjects

Objective

The aim of this study was to evaluate the morphological characteristics of the palatal rugae in Korean subjects to determine whether the palatal rugae can be used as an appropriate reference area for three-dimensional digital model superimpositions.

Materials and Methods

In total, 343 patients (110 men, 233 women; mean age, 25.6±8.2 years) who had a digital model taken at their initial visit were included, and the numbers and types of right and left palatal rugae were investigated according to the primary, secondary, and fragmentary rugae. Finally, the differences in the positions of the third primary ruga were investigated according to the presence of additional rugae posterior to the third primary ruga.

Results

The number of primary palatal rugae ranged from one to six, with 43.5% of the subjects having three primary rugae and 36.1% having four primary rugae; there were no significant differences between sexes. Except for the fragment rugae, the numbers of primary and secondary rugae were not significantly different between the left and right sides. The third primary ruga was located more significantly anteriorly when there was an additional ruga posterior to the third primary ruga (P < 0.001).

Conclusions

The numbers of the palatal rugae vary greatly among individuals, and this affects the anteroposterior position of the third primary ruga. When the third primary ruga is located anteriorly, care should be taken when using it as a reference area for superimposition with a digital model before and after orthodontic treatment.

A novel method for superimposition and measurements on maxillary digital 3D models-studies on validity and reliability

Background

Serial 3D models can be used to analyze changes, but correct superimposition is crucial before measurements can be assessed. Earlier studies show that every palatal structure changes due to growth or treatment. Here, we describe a new method that uses an algorithm-based analysis to perform superimpositions and measurements in maxillary 3D models. This method can be used to identify deformations. In a second step, only unchanged areas are used for superimposition.

Objectives

This study investigates the validity and reliability of this novel method.

Methods

Digital 3D models from 16 cases were modified by an independent 3D engineer to simulate space closure and growth. True values for tooth movements were available as reference. Measurements and repeated measurements were performed by four observers.

Results

The total tooth movement had an absolute mean error of 0.0225 mm (SD 0.03). The intraclass correlation coefficient (ICC) was 0.9996. Rotational measurements had an absolute mean error of 0.0291 degrees (SD 0.04 degrees) and an ICC of 0.9999.

Limitations

Serial models need to be taken with a moderate interval (1 to 2 years). Obvious changed areas in the palate need to be cropped before processing the models.

Conclusion

The tested method is valid and reliable with excellent accuracy and precision even when changes through growth or orthodontic treatment occur.

Comparison of orthodontic tooth movement between adolescents and adults based on implant superimposition

OBJECTIVE

We compared tooth movement under maximum anchorage control with mini-screw implants in growing and non-growing patients.

METHODS

In total, 15 adolescent (G1) and 19 adult (G2) patients with prognathic profiles were selected. All patients underwent first premolar extraction treatment with mini-screw implants for maximum anchorage control. Cone-beam computed tomography (CBCT) data were obtained immediately after implant placement (T1) and at the end of anterior tooth retraction (T2). Tooth movement and root length changes of the maxillary first molar, canine, and incisors were evaluated with three-dimensional models constructed using CBCT data obtained before and after orthodontic retraction through the superimposition of stable implants.

RESULTS

Distal movement of the molar crown was observed in G2, but mesial movement was observed in G1. Mesial tipping of the first molar (1.82 ± 6.76°) was seen in G1 and distal tipping (4.44 ± 3.77°) was observed in G2. For the canines, mesial crown tipping (0.33 ± 4.99°) was noted in G1 and distal crown tipping (8.00 ± 5.57°) was observed in G2. In adults, the lingual inclinations of the lateral and central incisors were 11.91 ± 7.01° and 11.47 ± 6.70°, with 0.99 ± 1.22 mm and 1.08 ± 1.20 mm root retraction, respectively. In adolescents, the torque changes were smaller (lateral incisors, 8.25 ± 10.15°; central incisors, 9.82 ± 8.97°) and the root retractions were 0.31 ± 1.81 mm and 0.77 ± 1.59 mm, respectively. Less shortening of the central incisor roots occurred in adolescents than in adults.

CONCLUSIONS

Tooth movements, such as anchor molar angular change, the canine tipping pattern, and the amount of incisor retraction, differed between adolescents and adults treated using the same anchorage with mini-screw implants, bracket prescription, and en masse retraction method. Anchorage strength of the first molars, canine movement patterns, and incisor retraction ranges are not determined by the anchorage device alone; growth and alveolar limitations also play roles.

Evaluation of crown inclination and angulation after orthodontic treatment using digital models : Comparison to the prescription of the brackets used

PURPOSE

To compare crown inclination and angulation results obtained after orthodontic treatment to the Roth prescription.

METHODS

The study design was based on files and documents obtained from a database of 26 patients who had undergone orthodontic treatment using the straight-wire technique and the Roth prescription. The crown inclination and angulation were measured using a three-dimensional (3D) cephalometric module (VistaDent, Dentsply, New York, NY, USA) by an orthodontist. A coordinate system (x, y, z) was developed for each tooth that used the Andrews plane as a para-axial reference. Descriptive statistical analysis provided the mean and standard deviation (SD) of crown inclination and angulation obtained after orthodontic treatment, which were compared to the Roth prescription.

RESULTS

Method reproducibility is an important test to investigate the margin of error and to verify the reliability of results. The results at time 1 (1.6° ± 1.1°) and time 2 (1.7° ± 1.2°) of the pilot study were not statistically different (p = 0.99). Maxillary lateral and central incisors presented significant differences in crown angulation (p < 0.05) compared to the Roth prescription. The crown angulation of maxillary second premolars with regard to the occlusal plane presented a similar value to the Roth prescription.

CONCLUSION

Crown inclination and angulation found at the end of orthodontic treatment did not match the prescription of the brackets for most teeth, as measured using digital models.

Superimposition of 3D digital models: A case report

INTRODUCTION

Superimposition of digital models may be performed to assess tooth movement in three dimensions. Detailed analysis of changes in tooth position after treatment may be achieved by this method.

AIM

This article describes the method of superimposing digital models with a clinical case. It emphasizes the difficult procedure of superimposing 3D models in the lower arch. A methodology for superimposing mandibular models acquired with a structured light 3D scanner is discussed.

CONCLUSION

Superimposition of digital models is useful to analyse tooth movement in the three planes of space, presenting advantages over the method of cephalogram superimposition. It seems feasible to superimpose digital models in the lower arch in patients without growth by using a coordinate system based on the palatal rugae and occlusion. The described method aims to advance the difficult procedure of superimposing digital models in the mandibular arch, but further research is nonetheless required in this field.

Maxillary incisors changes during space closure with conventional and skeletal anchorage methods: a systematic review

PURPOSE

The objective of this systematic review was to compare the antero-posterior, vertical and angular changes of maxillary incisors with conventional anchorage control techniques and mini-implant based space closure methods.

MATERIALS AND METHODS

The electronic databases Pubmed, Scopus, ISI Web of knowledge, Cochrane Library and Open Grey were searched for potentially eligible studies using a set of predetermined keywords. Full texts meeting the inclusion criteria as well as their references were manually searched. The primary outcome data (linear, angular, and vertical maxillary incisor changes) and secondary outcome data (overbite changes, soft tissue changes, biomechanical factors, root resorption and treatment duration) were extracted from the selected articles and entered into spreadsheets based on the type of anchorage used. The methodological quality of each study was assessed.

RESULTS

Six studies met the inclusion criteria. The amount of incisor retraction was greater with buccally placed mini-implants than conventional anchorage techniques. The incisor retraction with indirect anchorage from palatal mini-implants was less when compared with buccally placed mini-implants. Incisor intrusion occurred with buccal mini-implants, whereas extrusion was seen with conventional anchorage. Limited data on the biomechanical variables or adverse effects such as root resorption were reported in these studies.

CONCLUSION

More RCT's that take in to account relevant biomechanical variables and employ three-dimensional quantification of tooth movements are required to provide information on incisor changes during space closure.

Skeletally anchored mesialization of molars using digitized casts and two surface-matching approaches : Analysis of treatment effects

PURPOSE

To (1) quantify the three-dimensional treatment effect of a Mesialslider appliance using superimposed digital models, (2) to evaluate anchorage loss (measured by incisor displacement), and (3) to assess agreement between two different matching approaches, i.e., control point (CP)-based and iterative closest point (ICP) matching.

METHODS

In a retrospective study, the effects of a skeletally anchored uni- and bilateral mesialization appliance (Mesialslider) as well as simultaneous mesialization and distalization appliance (Mesio-Distalslider) were evaluated in 48 subjects (aged 11-53 years). Pre- and posttreatment casts were digitized and superimposed with two different approaches, i.e., using ten manually selected control points located at the anterior palate and by means of an automated ICP-matching approach using a standardized palatal reference area. The treatment effects were evaluated using control points on the maxillary central incisors and maxillary molar teeth, and the methods were compared through the application of linear regression analyses and computation of alignment errors.

RESULTS

Average upper molar mesialization was 6.3 ± 2.6 mm. Anchorage loss, designated as the mean amount of upper incisor displacement, was less than 0.5 mm in all dimensions investigated. Using the measurement method sufficient registration was possible using both approaches and corresponding tooth movements were significantly correlated (p < 0.01).

CONCLUSIONS

Accurate measurements of tooth displacement can be performed using both CP- and ICP-based matching approaches. Within the limits of performing a retrospective study, a premolar width of molar mesialization appeared possible without clinically relevant anchorage loss.

A novel approach for intra-operative shape acquisition of the tibio-femoral joints using 3D laser scanning in computer assisted orthopaedic surgery

BACKGROUND

Image registration (IR) is an important process of developing a spatial relationship between pre-operative data and the physical patient in the operation theatre. Current IR techniques for Computer Assisted Orthopaedic Surgery (CAOS) are time consuming and costly. There is a need to automate and accelerate this process.

METHODS

Bespoke quick, cost effective, contactless and automated 3D laser scanning techniques based on the DAVID Laserscanner method were designed. 10 cadaveric knee joints were intra-operatively laser scanned and were registered with the pre-operative MRI scans. The results are supported with a concurrent validity study.

RESULTS

The average absolute errors between scan models were systematically less than 1 mm. Errors on femoral surfaces were higher than tibial surfaces (P<0.05). Additionally, scans acquired through the large exposure produced higher errors than the smaller exposure (P<0.05).

CONCLUSION

This study has provided proof of concept for a novel automated shape acquisition and registration technique for CAOS.

Assessment of different techniques for 3D superimposition of serial digital maxillary dental casts on palatal structures

Serial 3-dimensional dental model superimposition provides a risk-free, detailed evaluation of morphological alterations on a patient’s mouth. Here, we evaluated accuracy and precision of five palatal areas, used for superimposition of maxillary 3D digital dental casts. Sixteen pre- and post-orthodontic treatment dental casts of growing patients (median time lapse: 15.1 months) were superimposed on each palatal area using the iterative closest point algorithm. Area A (medial 2/3 of the third rugae and a small area dorsal to them) was considered the gold standard, due to high anatomical stability. Areas B, C, and D added a distal extension along the midpalatal raphe, an anterior extension to the second rugae, and the remaining palatal surface, respectively. Area E was similar to A, located more posteriorly. Non parametric multivariate models showed minimal or no effect on accuracy and precision by operator, time point, or software settings. However, the choice of superimposition area resulted in statistically significant differences in accuracy and clinically significant differences in detected tooth movement (95% limits of agreement exceeding 1 mm and 3°). Superimposition on area A provided accurate, reproducible, and precise results. Outcomes were comparable for area B, but deteriorated when alternative areas were used.

Association among geometric configurations of palatal rugae

BACKGROUND

The associations between the length and morphological shape-related characteristics of palatal rugae have not been fully explored.

OBJECTIVE

We aimed to assess the possible association among various geometric configurations of the palatal rugae in an adult population.

MATERIALS AND METHODS

The maxillary dental casts of 217 non-growing subjects (95 males, 122 females, mean age 25.5±7.6 years) were scanned (laser scanning system Perceptron ScanWorks® V5) and digitized for linear measurements. The casts were also surveyed for visual categorization into curved, wavy, straight and other topographical forms, along with spatial direction of the rugae and the presence of unification. The rugae were categorized as primary, secondary, and fragmentary based on their lengths (> 5mm, 2-3mm, < 2mm, respectively). Chi square and one-way ANOVA and post-hoc tests were used to compare the palatal rugae groupings.

RESULTS

Primary and backward-directed rugae prevailed in the total sample (84.7% and 49.3%, respectively). Wavy form was dominant among primary lengths, while straight form was associated with the shorter secondary and fragmentary groups (p=0.0042). Absence of unification was the norm (88.8%).

CONCLUSIONS

Associations of length and shape characteristics among palatal rugae combine wavy patterns with increased length, and straight forms with shorter folds. These features contribute to the definition of ruga individuality in combination rather than separately.

A retrospective study comparing the loss of anchorage following the extraction of maxillary first or second premolars during orthodontic treatment with fixed appliances in adolescent patients

INTRODUCTION

This retrospective study assessed the difference in anchorage loss using 3D superimposition of study models between cases treated with extraction of maxillary first premolars and maxillary second premolars carried out in orthodontic specialist practice.

METHOD

Sixty subjects who have undergone extractions of either maxillary first or second premolars as part of their orthodontic treatment were selected. Eligibility criteria included patients with a Class I, mild Class II or III malocclusions, mild-to-moderate crowding with no anchorage reinforcement. Pre- and post-treatment maxillary dental study cases were scanned using a surface laser scanner to produced 3D digital images which were superimposed using areas of stability on the anterior hard palate. Anchorage loss was measured by the mesial movement of the maxillary first permanent molar.

RESULTS

The mean mesial movement for the maxillary first molars, when adjusted for confounding factors was 4.7 mm (SD 1.6) in the maxillary first premolar extraction group and 4.6 mm (SD 1.6) in the maxillary second premolar extraction group.

CONCLUSIONS

There is no difference in anchorage loss when comparing the extraction of the maxillary first premolars to the extraction maxillary second premolars.

Dentoalveolar and arch dimension changes in patients treated with miniplate-anchored maxillary protraction

INTRODUCTION

The aim of this study was to evaluate dentoalveolar and arch dimension changes in 2 miniplate-anchored maxillary protraction protocols in relation to an untreated control group using 3-dimensional digital models.

METHODS

Thirty growing Class III subjects with maxillary deficiency in the late mixed or early permanent dentition phase were randomly divided into 3 groups. In group 1 (n = 10), patients were treated with skeletally anchored facemasks anchored with miniplates placed at the zygomatic buttress. In group 2 (n = 10), patients were treated with Class III elastics extending from infrazygomatic miniplates in the maxilla to symphyseal miniplates in the mandible. Group 3 (n = 10) was an untreated control group. The decision to discontinue orthopedic treatment was made when the patients had 3 to 4 mm of positive anterior overjet. Pretreatment, posttreatment, and observation 3-dimensional digital models were analyzed, superimposed, 3 dimensionally mapped, and sectioned.

RESULTS

In this study, there were no significant changes in maxillary arch depth and maxillary or mandibular intermolar width before and after maxillary protraction or after the observation period in the control group. The mandibular arch depth decreased by a small but statistically significant amount only in groups 1 and 3. Superimposition of the pretreatment and posttreatment or observation maxillary 3-dimensional digital models showed minimal clinically significant dentoalveolar changes.

CONCLUSIONS

Miniplate-anchored maxillary protraction protocols can accomplish maxillary advancement by eliminating movements of teeth and dentoalveolar changes. No spontaneous improvement in transverse deficiency was detected after correction of the anteroposterior deficiency at this age. Consequently, patients with transverse maxillary deficiency should have rapid maxillary expansion before or during the miniplate-anchored protraction period to improve the transverse deficiency.

Measuring molar movement: A reliable technique

A technique of accurately assessing left and right maxillary molar movement is described, using superimposition of digital study models. This method has distinct advantages over the traditional method of measuring tooth movement using cephalometric radiographs.

Registration of serial maxillary models via the weighted rugae superimposition method

OBJECTIVES

We introduce a weighted method for superimposition of serial digital maxillary models based on the variable stability of rugae points.

SETTING AND SAMPLE POPULATION

Plaster maxillary models of 24 randomly selected 12-year-olds as well as their models at the age of 14 were obtained and scanned using a benchtop structured-light 3D scanner.

METHODS

The models were registered twice, once via the unweighted and again via the proposed weighted rugae superimposition method based on 12 rugae landmarks. For each superimposition, distances between the corresponding rugae points were measured and compared with reported displacements of rugae points in literature.

RESULTS

The unweighted superimposition produced no meaningful differences in terms of total displacements of registration landmarks, whereas the weighted method recognized the medial points of the third ruga as the most stable landmarks. Results of the weighted method also demonstrated statistically significant smaller changes for medial rugae points in almost every dimension compared to the lateral rugae points. These results comply with the growth patterns of maxilla and rugae point displacements reported in similar studies.

CONCLUSION

Considering the variable stability of rugae points during growth, the weighted rugae superimposition method results in more promising registrations on serial models. This method prioritizes registration landmarks based on clinical criteria of choice and is suitable for analysis of other structures such as tooth movements.

Three-dimensional evaluation of tooth movement in Class II malocclusions treated without extraction by orthodontic mini-implant anchorage

OBJECTIVE

The aim of this study was to analyze tooth movement and arch width changes in maxillary dentition following nonextraction treatment with orthodontic mini-implant (OMI) anchorage in Class II division 1 malocclusions.

METHODS

Seventeen adult patients diagnosed with Angle's Class II division 1 malocclusion were treated by nonextraction with OMIs as anchorage for distalization of whole maxillary dentition. Three-dimensional virtual maxillary models were superimposed with the best-fit method at the pretreatment and post-treatment stages. Linear, angular, and arch width variables were measured using Rapidform 2006 software, and analyzed by the paired t-test.

RESULTS

All maxillary teeth showed statistically significant movement posteriorly (p < 0.05). There were no significant changes in the vertical position of the maxillary teeth, except that the second molars were extruded (0.86 mm, p < 0.01). The maxillary first and second molars were rotated distal-in (4.5°, p < 0.001; 3.0°, p < 0.05, respectively). The intersecond molar width increased slightly (0.1 mm, p > 0.05) and the intercanine, interfirst premolar, intersecond premolar, and interfirst molar widths increased significantly (2.2 mm, p < 0.01; 2.2 mm, p < 0.05; 1.9 mm, p < 0.01; 2.0 mm, p < 0.01; respectively).

CONCLUSIONS

Nonextraction treatment with OMI anchorage for Class II division 1 malocclusions could retract the whole maxillary dentition to achieve a Class I canine and molar relationship without a change in the vertical position of the teeth; however, the second molars were significantly extruded. Simultaneously, the maxillary arch was shown to be expanded with distal-in rotation of the molars.

3D evaluation of palatal rugae for human identification using digital study models

Background:

While there is literature suggesting that the palatal rugae could be used for human identification, most of these studies use two-dimensional (2D) approach.

Aim:

The aims of this study were to evaluate palatal ruga patterns using three-dimensional (3D) digital models; compare the most clinically relevant digital model conversion techniques for identification of the palatal rugae; develop a protocol for overlay registration; determine changes in palatal ruga individual patterns through time; and investigate the efficiency and accuracy of 3D matching processes between different individuals’ patterns.

Material and Methods:

Five cross sections in the anteroposterior dimension and four cross sections in the transverse dimension were computed which generated 18 2D variables. In addition, 13 3D variables were defined: The posterior point of incisive papilla (IP), and the most medial and lateral end points of the palatal rugae (R1MR, R1ML, R1LR, R1LL, R2MR, R2ML, R2LR, R2LL, R3MR, R3ML, R3LR, and R3LL). The deviation magnitude for each variable was statistically analyzed in this study. Five different data sets with the same 31 landmarks were evaluated in this study.

Results:

The results demonstrated that 2D images and linear measurements in the anteroposterior and transverse dimensions were not sufficient for comparing different digital model conversion techniques using the palatal rugae. 3D digital models proved to be a highly effective tool in evaluating different palatal ruga patterns. The 3D landmarks showed no statistically significant mean differences over time or as a result of orthodontic treatment. No statistically significant mean differences were found between different digital model conversion techniques, that is, between OrthoCAD™ and Ortho Insight 3D™, and between Ortho Insight 3D™ and the iTero^® scans, when using 12 3D palatal rugae landmarks for comparison.

Conclusion:

Although 12 palatal 3D landmarks could be used for human identification, certain landmarks were especially important in the matching process and were arranged by strength and importance. Proposed values for 3D palatal landmarks were introduced that could be useful in biometrics and forensic odontology for the verification of human identity.

Predicted and actual end-of-treatment occlusion produced with aligner therapy

OBJECTIVE

To compare three-dimensional (3D) ClinCheck™ models with the subjects' actual 3D posttreatment models using the American Board of Orthodontics Objective Grading System (OGS).

MATERIALS AND METHODS

This prospective, within-subject study included 27 consecutive cases treated with aligner therapy. The posttreatment plaster models taken immediately after treatment were scanned and converted to stereolithography (STL) files; the ClinCheck models were also converted to STL format. MeshLab software was used to measure the seven components of the OGS, including alignment, marginal ridges, buccolingual inclinations, occlusal contacts, occlusal relationships, overjet and interproximal contacts. An overall OGS deduction score was also calculated.

RESULTS

Compared with the posttreatment models, the ClinCheck models showed significantly (P  =  .016) fewer overall OGS point deductions (24 vs 15). These overall differences were due to significantly (P < .05) more deductions among the posttreatment models than the ClinCheck models for alignment (4.0 vs 1.0 deductions), buccolingual inclinations (4.0 vs 3.0 deductions), occlusal contacts (3.0 vs 2.0 deductions), and occlusal relations (4.0 vs 2.0 deductions).

CONCLUSION

The ClinCheck models do not accurately reflect the patients' final occlusion, as measured by the OGS, at the end of active treatment.

A reliable method for evaluating upper molar distalization: Superimposition of three-dimensional digital models

Objective

The aim of this study was to evaluate the reliability of measurements obtained after the superimposition of three-dimensional (3D) digital models by comparing them with those obtained from lateral cephalometric radiographs and photocopies of plaster models for the evaluation of upper molar distalization.

Methods

Data were collected from plaster models and lateral cephalometric radiographs of 20 Class II patients whose maxillary first molars were distalized with an intraoral distalizer. The posterior movements of the maxillary first molars were evaluated using lateral cephalometric radiographs (group CP), photocopies of plaster models (group PH), and digitized 3D models (group TD). Additionally, distalization and expansion of the other teeth and the degrees of molar rotation were measured in group PH and group TD and compared between the two groups.

Results

No significant difference was observed regarding the amount of molar distalization among the three groups. A comparison of the aforementioned parameters between group PH and group TD did not reveal any significant difference.

Conclusions

3D digital models are reliable to assess the results of upper molar distalization and can be considered a valid alternative to conventional measurement methods.

Reliability of linear and angular dental measurements with the OrthoMechanics Sequential Analyzer

INTRODUCTION

The aim of this study was to evaluate the reliability of newly developed software in the assessment of orthodontic tooth movement 3 dimensionally.

METHODS

The sample consisted of pretreatment and posttreatment computed tomography scans and plaster dental models of 20 orthodontic patients treated with a hyrax palatal expander as a part of their comprehensive orthodontic treatment. Dental-arch measurements, including arch widths, tooth inclinations, and angulation parameters, were measured on the scans using InvivoDental 3D imaging software (version 5.1; Motionview, Hixson, Tenn). The plaster dental models were laser scanned and superimposed, and measurements were obtained digitally using the new software. Agreement between the digital models and the computed tomography measurements was evaluated with intraclass correlation coefficients, paired t tests, and Bland-Altman plots. A P value of ≤0.05 was considered statistically significant.

RESULTS

High agreement, a nonsignificant paired t test, and no indication of agreement discrepancies were observed for most of the measured parameters.

CONCLUSIONS

The results confirmed that the new software program offers a reliable tool for dental-arch measurements obtained from 3-dimensional laser-scanned models.

A three-dimensional comparison of torque achieved with a preadjusted edgewise appliance using a Roth or MBT prescription

OBJECTIVE

To investigate if there are any significant differences in the final inclination of the upper and lower anterior teeth of patients treated with a Roth or an MBT bracket prescription.

MATERIALS AND METHODS

Forty sets of posttreatment study models from patients treated using a preadjusted edgewise appliance (20 Roth and 20 MBT) were selected using predetermined inclusion and exclusion criteria. The models were masked and laser-scanned, and the final crown inclinations of UL1, UR3, and LR1 were assessed from the digital images. A two-way analysis of variance was undertaken with the dependent variable of final crown inclination and independent variables of bracket prescription (Roth or MBT) and tooth type.

RESULTS

There were no statistically significant differences in terms of the final inclination of the anterior teeth between the two bracket prescriptions (P  =  .132). Statistically significant differences were found between the final inclinations of different tooth types investigated (P < .001).

CONCLUSION

In this group of selected patient records, the differences in torque values between the two bracket prescriptions did not lead to any real clinically detectable differences in the final inclination of teeth.