Reliability and accuracy of a method for measuring temporomandibular joint condylar volume

OBJECTIVE

The aim of this study was to develop and validate a technique for mandibular condyle segmentation and volume determination by using cone beam computed tomography (CBCT).

STUDY DESIGN

A dry skull was used to generate 3 dimensional (3-D)-printed mandible models that were then imaged by using CBCT. Semiautomatic segmentation of condyles was completed. The Frankfurt plane was established and translated to the most inferior point of the sigmoid notch, and the condylar volume superior to the plane was determined. This procedure was repeated on 3-D-printed mandibles by using physical landmarks and the water displacement method to obtain the physical volume. This was repeated 3 times to evaluate reliability. Sensitivity analysis was performed to demonstrate the effect of discrepancies in locating landmarks in the Frankfurt plane. Condylar volume measurements obtained from CBCT were compared with physical measurements through repeated-measures analysis of variance (ANOVA) to determine accuracy.

RESULTS

Condylar volume obtained from CBCT and physical measurements resulted in an intraclass correlation coefficient of 0.988 (0.918, 0.998) (P < .01) with both modalities, demonstrating excellent intrarater reliability. The mean difference of volume measurements between the modalities was not statistically significant (P = .365). Potential discrepancies in porion coordinates had minimal impact on condylar volume change.

CONCLUSIONS

The condylar segmentation technique proved to be a reliable and accurate method for evaluating condylar volume.

Fully Automated Segmentation of Alveolar Bone Using Deep Convolutional Neural Networks from Intraoral Ultrasound Images

Delineation of alveolar bone aids the diagnosis and treatment of periodontal diseases. In current practice, conventional 2D radiography and 3D cone-beam computed tomography (CBCT) imaging are used as the non-invasive approaches to image and delineate alveolar bone structures. Recently, high-frequency ultrasound imaging is proposed as an alternative to conventional imaging methods to prevent the harmful effects of ionizing radiation. However, the manual delineation of alveolar bone from ultrasound imaging is time-consuming and subject to inter and intraobserver variability. This study proposes to use a convolutional neural network-based machine learning framework to automatically segment the alveolar bone from ultrasound images. The proposed method consists of a homomorphic filtering based noise reduction and a u-net machine learning framework for automated delineation. The proposed method was evaluated over 15 ultrasound images of tooth acquired from procine specimens. The comparisons against manual ground truth delineations performed by three experts in terms of mean Dice score and Hausdorff distance values demonstrate that the proposed method yielded an improved performance over a recent state of the art graph cuts based method.

Reliability and accuracy of segmentation of mandibular condyles from different three-dimensional imaging modalities: a systematic review

OBJECTIVE

To critically synthesize the literature surrounding segmentation of the mandibular condyle using three-dimensional imaging modalities. Specifically, analyzing the reliability and accuracy of methods used for three-dimensional condyle segmentation.

METHODS

Three electronic databases were searched for studies reporting the reliability and accuracy of various methods used to segment mandibular condyles from three-dimensional imaging modalities. Two authors independently reviewed articles for eligibility and data extraction.

RESULTS

Nine studies fulfilled the inclusion criteria. Eight studies assessed the condylar segmentation from CBCT images and limited studies were available on non-CBCT three-dimensional imaging modalities. Threshold-based volume segmentation, manual segmentation, and semi-automatic segmentation techniques were presented. Threshold-based volume segmentation reported higher accuracy when completed by an experienced technician compared to clinicians. Adequate reliability and accuracy were observed in manual segmentation. Although adequate reliability was reported in semi-automatic segmentation, data on its accuracy were lacking.

CONCLUSION

A definitive conclusion with regards to which current technique is most reliable and accurate to efficiently segment the mandibular condyle cannot be made with the currently available evidence. This is especially true in terms of non-CBCT imaging modalities with very limited literature available.

Dental and skeletal changes associated with the Damon system philosophical approach

OBJECTIVE

To compare the skeletal and dentoalveolar changes produced by the Damon system's treatment philosophy to traditional orthodontic treatment techniques.

MATERIALS AND METHODS

An electronic search in four major databases was completed: Cochrane, PubMed, EMBASE, and Google Beta Scholar on October 5th, 2018. Randomized controlled trials, prospective and retrospective controlled clinical trials were included in this systematic review. The quality assessment of individual studies was done using two different tools: The Cochrane Risk of Bias Assessment Tool (RTCs) and The Methodological Index for Non-Randomized Studies (MINORS) (non-RCTs).

RESULTS

Seven studies were included for this qualitative analysis. Six studies compared the Damon system to various types of conventional (non self-ligating bracket) system as a comparison group. One study used a quad helix as a comparison for a few months before a full bonding appointment with conventional brackets. The majority of studies found an increase in maxillary inter-canine, inter-premolar, and intermolar distance after the treatment in both the Damon and comparison groups. Yet, all studies concluded that there is no significant difference in the final transverse dimension between the two groups. One study also found that the transverse expansion was achieved mainly by tipping movement of posterior dentition, and a decrease in the posterior buccal bone area was evident in both groups after treatment.

CONCLUSION

There is not enough evidence to support the claim that the Damon system allows additional arch expansion with better tipping control than with traditional techniques.

Additional appointments and discomfort associated with compliance-free fixed Class II corrector treatment: a systematic review

OBJECTIVE

A critical analysis of the literature to determine the prevalence and type of emergency/additional appointments, and discomfort levels associated with fixed Class II correctors.

METHODS

Studies examining patient's sources of discomfort or emergency appointments associated with compliance-free Class II correctors were included. Comprehensive searches up to July 2018 were conducted using the following databases: MEDLINE (OvidSP), PubMed, Web of Science, and Embase. A partial grey literature search was taken using Google Scholar and OpenGrey. Two reviewers independently performed the selection process and risk of bias assessment. The Newcastle-Ottawa Scale for cross-sectional studies were used. A summary of the overall strength of evidence was presented using 'Grading of Recommendations, Assessment, Development and Evaluation' (GRADE) tool. Included studies were evaluated according to their design, study quality, consistency, and directness.

RESULTS

The selected studies were published between 2001 and 2018, and the number of patients per studied group ranged from 8 to 182. One thousand five hundred forty-two patients were evaluated in total. The patients' mean age at start of treatment ranged from 10 to 16.9 years and the fixed Class II corrector treatment duration ranged from 4 to 12 months. The included studies in this systematic review were too clinically heterogeneous (different appliances, different data recollection processes) to justify a meta-analysis.

LIMITATIONS

This review was not previously registered. A low level of evidence was observed among the two randomized trials, the 10 cohorts and three cross-sectional studies identified.

CONCLUSIONS

The main source of discomfort from Forsus-type appliances appears to be soreness in the cheeks (low level of evidence with a weak recommendation strength). Most evaluated patients treated with a Herbst appliance, regardless of design, will experience complications (fractures and/or dislodging) requiring emergency appointments (low level of evidence with a weak recommendation strength).

REGISTRATION

The review protocol was not registered.

Diagnostic ultrasound assessment of temporomandibular joints: a systematic review and meta-analysis

OBJECTIVES:

The purpose of this systematic review was to determine the diagnostic capability of ultrasound to assess TMJ alterations as disc displacement (DD), joint effusion (JE) and condylar changes (CC) using 3D imaging modalities as reference standard.

METHODS:

Studies were gathered by searching several electronic databases and partial grey literature up to January eighth, 2018 without restrictions of language and time. The risk of bias was evaluated using the second version of Quality Assessment Tool for Diagnostic of Accuracy Studies-2 (QUADAS-2). The grading of Recommendation, Assessment, Development and Evaluation (GRADEpro system) instrument was applied to assess the level of evidence across the studies.

RESULTS:

After applying the eligibility criteria, 28 studies were identified and synthesized. All studies were methodologically acceptable presenting low applicability concerns, although none of them fulfilled all QUADAS-2 criteria. The quantitative analysis included 22 studies, 2829 joints in total. The quality of the evidence evaluated by GRADE system suggested moderate confidence in estimating the outcomes.

CONCLUSION:

This systematic review demonstrated the ultrasound has acceptable capability to screen for DD and JE in TMD patients. For screening of condylar changes, ultrasound needs further studies using CT or CBCT as reference standard to support its use. More advanced imaging such as MRI can thereafter be used to confirm the diagnosis if deemed necessary.

Comparison of ultrasound imaging and cone-beam computed tomography for examination of the alveolar bone level: A systematic review

Background and objective

The current methods to image alveolar bone in humans include intraoral 2D radiography and cone-beam computed tomography (CBCT). However, these methods expose the subject to ionizing radiation. Therefore, ultrasound imaging has been investigated as an alternative technique, as it is both non-invasive and free from ionizing radiation. In order to assess the validity and reliability of ultrasonography in visualizing alveolar bone, a systematic review was conducted comparing ultrasound imaging to CBCT for examination of the alveolar bone level.

Study design

Seven databases were searched. Studies addressing examination of alveolar bone level via CBCT and ultrasound were selected. Risk of bias under Cochrane guidelines was used as a methodological quality assessment tool.

Results

All the four included studies were ex vivo studies that used porcine or human cadaver samples. The alveolar bone level was measured by the distance from the alveolar bone crest to certain landmarks such as cemento-enamel junction or gingival margin. The risk of bias was found as low. The mean difference between ultrasound and CBCT measurements ranged from 0.07 mm to 0.68 mm, equivalent to 1.6% - 8.8%.

Conclusions

There is currently preliminary evidence to support the use of ultrasonography as compared to CBCT for the examination of alveolar bone level. Further studies comparing ultrasound to gold standard methods would be necessary to help validate the accuracy of ultrasonography as a diagnostic technique in periodontal imaging.

Parent's Sense of Coherence and Children's Oral Health-Related Behaviors: Is There an Association?

PURPOSE

Parental capacity to face day-to-day stressors has a relevant role in recognizing and mobilizing resources to control children's oral health behaviors. This capacity has been explored by means of the sense of coherence. The purpose of this study was to explore the association between mothers' sense of coherence (SOC) and their preschool children's oral health-related behaviors.

METHODS

Mothers and their pre-school children were recruited during immunization programs at community health centers in Edmonton, Canada. Participants answered eight questions on socio-demographics (covariates), parents' SOC (main independent variable), and children's oral health-related practices (outcome variables). Statistical analyses comprised a two-sample t test, chi-square test, and logistic regression.

RESULTS

A total of 378 pairs of mothers/ children participated in this study. Children's mean age was 3.92±(1.33) years. Mothers' SOC was statistically associated with children's frequency of sugar consumption and frequency and pattern of dental visits. The children of mothers who had higher levels of SOC presented a lower frequency intake of food or drink containing sugar and were more likely to visit the dentist for preventive purposes.

CONCLUSIONS

Mothers' sense of coherence had a significant association with children's oral health-related behaviors; a higher SOC of mothers was associated with more positive behaviors among their children.

The effect of buccal-lingual slot dimension size on third-order torque response

Introduction

The focus of the presented study was to investigate the effect of buccal-lingual (B-L) orthodontic bracket slot dimension on third-order torque mechanics.

Materials and methods

Three types of orthodontic brackets and two archwire sizes were considered. Ortho Classic H4 (0.026″ B-L slot, passive), Ormco Damon Q (0.028″ B-L slot, passive), and In-Ovation R (0.028″ slot, active) brackets were tested using 0.017″ × 0.025″ and 0.019″ × 0.025″ beta-titanium archwires. An in vitro orthodontic torque simulator (OTS) was used to rotate archwires relative to a single bracket while recording forces and moments in three directions. For each bracket-archwire combination, a total of n = 47 samples were tested. Repeated measures analysis of variance between brackets was conducted for third-order torque values at 3° increments between 9° and 30° during loading and unloading for each archwire size.

Results

Statistically significant differences between H4 and Q brackets were only found for 0.017″ × 0.025″ archwires during loading, and 0.019″ × 0.025″ archwires during unloading. Conversely, differences between H4 and R brackets were found for both archwires during loading and unloading phases. Finally, when using a 0.017″ × 0.025″ archwire the H4 brackets reached the 5 Nmm threshold before R and Q brackets; however, there was little difference found when using a 0.019″ × 0.025″ archwire.

Conclusions

The concept of using a smaller B-L bracket slot dimension in orthodontic treatment showed it may theoretically allow for more options, primarily using smaller archwires to correct third-order rotational misalignments. However, it is suspected that bracket material limitations and added loading on the door currently prevent this from being clinically applicable.

New algorithm for semiautomatic segmentation of nasal cavity and pharyngeal airway in comparison with manual segmentation using cone-beam computed tomography

INTRODUCTION

Our objectives were to assess reliability, validity, and time efficiency of semiautomatic segmentation using Segura software of the nasal and pharyngeal airways, against manual segmentation with point-based analysis with color mapping.

METHODS

Pharyngeal and nasal airways from 10 cone-beam computed tomography image sets were segmented manually and semiautomatically using Segura (University of Alberta, Edmonton, Alberta, Canada). To test intraexaminer and interexaminer reliabilities, semiautomatic segmentation was repeated 3 times by 1 examiner and then by 3 examiners. In addition to volume and surface area, point-based analysis was completed to assess the reconstructed 3-dimensional models from Segura against manual segmentation. The times of both methods of segmentation were also recorded to assess time efficiency.

RESULTS

The reliability and validity of Segura were excellent (intraclass correlation coefficient, >0.9 for volume and surface area). Part analysis showed small differences between the Segura and manually segmented 3-dimensional models (greatest difference did not exceed 4.3 mm). Time of segmentation using Segura was significantly shorter than that for manual segmentation, 49 ± 11.0 vs 109 ± 9.4 minutes (P <0.001).

CONCLUSIONS

Semiautomatic segmentation of the pharyngeal and nasal airways using Segura was found to be reliable, valid, and time efficient. Part analysis with color mapping was the key to explaining differences in upper airway volume and provides meaningful and clinically relevant analysis of 3-dimensional changes.

Using cone beam CT to assess the upper airway after surgery in children with sleep disordered breathing symptoms and maxillary-mandibular disproportions: a clinical pilot

BACKGROUND

The surgical excision of anatomic obstructions such as adenoids, palatine or lingual tonsils are commonly performed in children with sleep disordered breathing (SDB). Imaging studies measuring airway changes post-surgery in the SDB pediatric population are scarce, rarely addresses the nasal cavity, and are based on global measures (e.g. volume) that do not represent the complexity of the upper airway anatomy. The purpose of this pilot is to test the feasibility in using cone beam CT (CBCT) to analyze the nasal and pharyngeal airway space post-surgery using meaningful methods of analyses, and correlating imaging findings with clinical outcomes in children with SDB symptoms and maxillary-mandibular disproportion.

METHODS

Twelve non-syndromic children with SDB symptoms and jaw disproportions were evaluated by interdisciplinary airway team before and after upper airway surgery. CBCT and OSA-18 quality of life questionnaire pre and post-operatively were completed. Conventional and new airway variables were measured based on 3D models of the upper airways and correlated with OSA-18. Conventional measures include volume, surface area, and cross-sectional area. New airway measures include constriction and patency; point-based analyses.

RESULTS

Eight females and four males were 8.8 ± 2 years with mean BMI of 18.7 ± 3. OSA-18 improved, median (lower quartile-upper quartile) from 64.2 (54.7-79.5) to 37.6 (28.7-43) postoperatively, p < 0.001. The median of all airway measures improved however with very wide range. Subjects with the smallest amounts of constriction relief and/or gain in airway patency presented with least improvement in OSA-18. New airway measures show strong correlation with changes in OSA-18 (ρ = 0.44 to 0.71) whereas conventional measures showed very weak correlation (ρ = -0.04 to 0.37).

CONCLUSIONS

Using point-based analyses, new airway measures better explained changes in clinical symptoms compared to conventional measures. Airway patency gained by at least 150% and constriction relief by at least 15% showed marked improvement in OSA-18 by 40-55%, after surgery in the tested cohort.

RANKL release from self-assembling nanofiber hydrogels for inducing osteoclastogenesis in vitro

PURPOSE

To develop a nanofiber hydrogel (NF-hydrogel) for sustained and controlled release of the recombinant receptor activator of NF-kB ligand; (RANKL) and to characterize the release kinetics and bioactivity of the released RANKL.

METHODS

Various concentrations of fluorescently-labelled RANKL protein were added to NF-hydrogels, composed of Acetyl-(Arg-Ala-Asp-Ala)₄-CONH₂ [(RADA)₄] of different concentrations, to investigate the resulting in vitro release rates. The nano-structures of NF-hydrogel, with and without RANKL, were determined using atomic force microscopy (AFM). Released RANKL was further analyzed for changes in secondary and tertiary structure using CD spectroscopy and fluorescent emission spectroscopy, respectively. Bioactivity of released RANKL protein was determined using NFATc1 gene expression and tartrate resistant acid phosphatase (TRAP) activity of osteoclast cells as biomarkers.

RESULTS

NF-hydrogel concentration dependent sustained release of RANKL protein was measured at concentrations between 0.5 and 2%(w/v). NF-hydrogel at 2%(w/v) concentration exhibited a sustained and slow-release of RANKL protein up to 48h. Secondary and tertiary structure analyses confirmed no changes to the RANKL protein released from NF-hydrogel in comparison to native RANKL. The results of NFATc1 gene mRNA expression and TRAP activities of osteoclast, showed that the release process did not affect the bioactivity of released RANKL.

CONCLUSIONS

This novel study is the first of its kind to attempt in vitro characterization of NF-hydrogel based delivery of RANKL protein to induce osteoclastogenesis. We have shown the self-assembling NF-hydrogel peptide system is amenable to the sustained and controlled release of RANKL locally; that could in turn increase local concentration of RANKL to induce osteoclastogenesis, for application to the controlled mobilization of tooth movement in orthodontic procedures.

STATEMENT OF SIGNIFICANCE

Orthodontic tooth movement (OTM) occurs through controlled application of light forces to teeth, facilitating the required changes in the surrounding alveolar bone through the process of bone remodelling. The RANKL system regulates alveolar bone remodelling and controls root resorption during OTM. The use of exogenous RANKL to accelerate OTM has not been attempted to date because large quantities of RANKL for systemic therapy may subsequently cause serious systemic loss of skeletal bone. The controlled and sustained local release of RANKL from a carrier matrix could maximize its therapeutic benefit whilst minimizing systemic side effects. In this study a NF-hydrogel was used for sustained and controlled release of RANKL and the release kinetics and biofunctionality of the released RANKL was characterized. Our results provide fundamental insight for further investigating the role of RANKL NF-hydrogel release systems for inducing osteoclastogenesis in vivo.

Three-dimensional morphological changes of the temporomandibular joint and functional effects after mandibulotomy

BACKGROUND

The midline and paramedian mandibulotomy are surgical procedures that divide the mandibular bone into two halves and disconnects the condylar heads of the TMJ from each other. This study aimed to prospectively evaluate the temporomandibular joint (TMJ) functional and morphological changes after mandibulotomy using a reconstructed 3D models of the TMJ.

METHODS

Sixteen adult patients diagnosed with oral and oropharyngeal tumors with planned surgical mandibulotomy (test group, 9 patients) or transoral (control group, seven patients) treatments were included in the study. MRI and CBCT images were obtained immediately preceeding surgery and 6-8 weeks after surgery. Using the MRI-CBCT registered images, TMJ tissues were segmented at the two occasions by the same operator and 3D models were reconstructed for morphological assessment. Changes across time were measured using the volume overlap and Hausdorff distance of the disc and condyle 3D models. Disc-condyle relationship was measured using point-based and color map analysis. To assess the early functional changes, the Jaw function limitation scale (JFLS) and the maximum mouth opening were measured. Two-sample Hotelling T² t-test was performed to determine the significance of the morphological and clinical outcomes' differences between the two groups.

RESULTS

The two-sample Hotelling T² t-test showed significant differences (T² (df1,df2) = 0.97 (5,26), p <0.01) between the mean values of all outcomes among the 2 groups. The change in disc displacement was significantly different between the two groups (p <0.05). However, the condylar displacement was not significantly different between the two groups (p =0.3). The average of the JFLS score was five times larger after mandibulotomy, and was 2 times larger after transoral surgery (p < 0.01). Patients showed decrease in the average of the maximum interincisal mouth opening by 11 mm after mandibulotomy, and by 5.4 mm after transoral surgery.

CONCLUSION

The quantitative assessment of the TMJ showed minimal changes of the condylar position and variable degrees of articular disc displacement associated with the paramedian split mandibulotomy. As well, limited jaw functions and vertical mouth opening were noticed more in the mandibultomy group compared to the transoral group in 6- weeks after surgery.

Three-Dimensional Assessment of Temporomandibular Joint Using MRI-CBCT Image Registration

Purpose

To introduce a new approach to reconstruct a 3D model of the TMJ using magnetic resonance imaging (MRI) and cone-beam computed tomography (CBCT) registered images, and to evaluate the intra-examiner reproducibility values of reconstructing the 3D models of the TMJ.

Methods

MRI and CBCT images of five patients (10 TMJs) were obtained. Multiple MRIs and CBCT images were registered using a mutual information based algorithm. The articular disc, condylar head and glenoid fossa were segmented at two different occasions, at least one-week apart, by one investigator, and 3D models were reconstructed. Differences between the segmentation at two occasions were automatically measured using the surface contours (Average Perpendicular Distance) and the volume overlap (Dice Similarity Index) of the 3D models. Descriptive analysis of the changes at 2 occasions, including means and standard deviation (SD) were reported to describe the intra-examiner reproducibility.

Results

The automatic segmentation of the condyle revealed maximum distance change of 1.9±0.93 mm, similarity index of 98% and root mean squared distance of 0.1±0.08 mm, and the glenoid fossa revealed maximum distance change of 2±0.52 mm, similarity index of 96% and root mean squared distance of 0.2±0.04 mm. The manual segmentation of the articular disc revealed maximum distance change of 3.6±0.32 mm, similarity index of 80% and root mean squared distance of 0.3±0.1 mm.

Conclusion

The MRI-CBCT registration provides a reliable tool to reconstruct 3D models of the TMJ’s soft and hard tissues, allows quantification of the articular disc morphology and position changes with associated differences of the condylar head and glenoid fossa, and facilitates measuring tissue changes over time.

Initial forces experienced by the anterior and posterior teeth during dental-anchored or skeletal-anchored en masse retraction in vitro

OBJECTIVE

To investigate initial forces acting on teeth around the arch during en masse retraction using an in vitro Orthodontic SIMulator (OSIM).

MATERIALS AND METHODS

The OSIM was used to represent the full maxillary arch in a case wherein both first premolars had been extracted. Dental and skeletal anchorage to a posted archwire and skeletal anchorage to a 10-mm power arm were all simulated. A 0.019 × 0.025-inch stainless steel archwire was used in all cases, and 15-mm light nickel-titanium springs were activated to approximately 150 g on both sides of the arch. A sample size of n = 40 springs were tested for each of the three groups. Multivariate analysis of variance (α = 0.05) was used to determine differences between treatment groups.

RESULTS

In the anterior segment, it was found that skeletal anchorage with power arms generated the largest retraction force (P < .001). The largest vertical forces on the unit were generated using skeletal anchorage, followed by skeletal anchorage with power arms, and finally dental anchorage. Power arms were found to generate larger intrusive forces on the lateral incisors and extrusive forces on the canines than on other groups. For the posterior anchorage unit, dental anchorage generated the largest protraction and palatal forces. Negligible forces were measured for both skeletal anchorage groups. Vertical forces on the posterior unit were minimal in all cases (<0.1 N).

CONCLUSIONS

All retraction methods produced sufficient forces to retract the anterior teeth during en masse retraction. Skeletal anchorage reduced forces on the posterior teeth but introduced greater vertical forces on the anterior teeth.

MRI alone versus MRI-CBCT registered images to evaluate temporomandibular joint internal derangement

OBJECTIVE

To evaluate the effect of magnetic resonance imaging-cone beam computed tomography (MRI-CBCT) image registration on inter- and intraexaminer consistency when evaluating temporomandibular joint (TMJ) internal derangement compared to MRI alone.

METHODS

MRI and CBCT images of 25 patients (50 TMJs) were obtained and coregistered using mutual-information rigid image registration via Mirada XD software. Two experienced radiologists independently and blindly evaluated two types of images (MRI alone and MRI-CBCT registered images) at two different times (T1 and T2) for TMJ internal derangement, based on sagittal and coronal articular disc position in relation to the head of the condyle and the posterior slope of the articular eminence.

RESULTS

The intraexaminer consistency with MRI alone (examiner 1 = 0.85 [0.74-0.92]; examiner 2 = 0.91 [0.84-0.95]) was lower than for the MRI-CBCT registered images (examiner 1 = 0.95 [0.91-0.97]; examiner 2 = 0.97 [0.96-0.99]). The interexaminer consistency of evaluating internal derangement with MRI alone (0.52 [0.18-0.73] at T1; 0.71 [0.45-0.84] at T2) was lower than for the MRI-CBCT registered images (0.97 [0.95-0.98] at T1; 0.98 [0.96-0.99] at T2). When disc position classification was dichotomized to normal versus anteriorly displaced, intraexaminer agreement for the two examiners was 0.52 and 0.63 for MRI alone, but was 0.91 and 0.92 for MRI-CBCT registered images. Interexaminer agreement for MRI alone was 0.29 at T1 and 0.42 at T2, but was 0.96 at both examination times for MRI-CBCT registered images.

CONCLUSION

The MRI-CBCT registered images improved intra- and interexaminer consistency in the evaluation of internal derangement of TMJ.

Measurement accuracy and reliability of tooth length on conventional and CBCT reconstructed panoramic radiographs

INTRODUCTION:

This in vivo study assessed accuracy and reliability of tooth length measurements obtained from conventional panoramic radiographs and CBCT panoramic reconstructions to that of a digital caliper (gold standard).

METHODS:

The sample consisted of subjects who had CBCT and conventional panoramic radiographic imaging and who required maxillary premolar extraction for routine orthodontic treatment. A total of 48 teeth extracted from 26 subjects were measured directly with digital calipers. Radiographic images were scanned and digitally measured in Dolphin 3D software. Accuracy of tooth length measurements made by CBCT panoramic reconstructions, conventional panoramic radiographs and digital caliper (gold standard) were compared to each other by repeated measures one-way ANOVA with Bonferroni correction and by single measures intraclass correlation coefficient.

RESULTS:

Repeated root length measures with digital calipers, panoramic radiographs and CBCT constructed panoramic-like images were all individually highly reliable. Compared to the caliper (gold standard), tooth measurements obtained from conventional panoramic radiographs were on average 6.3 mm (SD = 2.0 mm) longer, while tooth measurements from CBCT panoramic reconstructions were an average of 1.7 mm (SD = 1.2 mm) shorter.

CONCLUSIONS:

In comparison to actual tooth lengths, conventional panoramic radiographs were relatively inaccurate, overestimating the lengths by 29%, while CBCT panoramic reconstructions underestimated the lengths by 4%.

MRI and CBCT image registration of temporomandibular joint: a systematic review

Purpose

The purpose of the present review is to systematically and critically analyze the available literature regarding the importance, applicability, and practicality of (MRI), computerized tomography (CT) or cone-beam CT (CBCT) image registration for TMJ anatomy and assessment.

Data sources

A systematic search of 4 databases; MEDLINE, EMBASE, EBM reviews and Scopus, was conducted by 2 reviewers. An additional manual search of the bibliography was performed.

Inclusion criteria

All articles discussing the magnetic resonance imaging MRI and CT or CBCT image registration for temporomandibular joint (TMJ) visualization or assessment were included.

Results and included articles’ characteristics

Only 3 articles satisfied the inclusion criteria. All included articles were published within the last 7 years. Two articles described MRI to CT multimodality image registration as a complementary tool to visualize TMJ. Both articles used images of one patient only to introduce the complementary concept of MRI-CT fused image. One article assessed the reliability of using MRI-CBCT registration to evaluate the TMJ disc position and osseous pathology for 10 temporomandibular disorder (TMD) patients.

Conclusion

There are very limited studies of MRI-CT/CBCT registration to reach a conclusion regarding its accuracy or clinical use in the temporomandibular joints.

Electronic supplementary material

The online version of this article (doi:10.1186/s40463-016-0144-4) contains supplementary material, which is available to authorized users.

Influence of second-order bracket-archwire misalignments on loads generated during third-order archwire rotation in orthodontic treatment

OBJECTIVE

To investigate the influence of a rotational second-order bracket-archwire misalignment on the loads generated during third-order torque procedures. Specifically, torque in the second- and third-order directions was considered.

MATERIALS AND METHODS

An orthodontic torque simulator (OTS) was used to simulate the third-order torque between Damon Q brackets and 0.019 × 0.025-inch stainless steel archwires. Second-order misalignments were introduced in 0.5° increments from a neutral position, 0.0°, up to 3.0° of misalignment. A sample size of 30 brackets was used for each misalignment. The archwire was then rotated in the OTS from its neutral position up to 30° in 3° increments and then unloaded in the same increments. At each position, all forces and torques were recorded. Repeated-measures analysis of variance was used to determine if the second-order misalignments significantly affected torque values in the second- and third-order directions.

RESULTS

From statistical analysis of the experimental data, it was found that the only statistically significant differences in third-order torque between a misaligned state and the neutral position occurred for 2.5° and 3.0° of misalignment, with mean differences of 2.54 Nmm and 2.33 Nmm, respectively. In addition, in pairwise comparisons of second-order torque for each misalignment increment, statistical differences were observed in all comparisons except for 0.0° vs 0.5° and 1.5° vs 2.0°.

CONCLUSION

The introduction of a second-order misalignment during third-order torque simulation resulted in statistically significant differences in both second- and third-order torque response; however, the former is arguably clinically insignificant.

Imaging the Cemento-Enamel Junction Using a 20-MHz Ultrasonic Transducer

The cemento-enamel junction (CEJ), which is the intersection between enamel and cementum, is an important landmark in the diagnosis of periodontal disease. Pulse-echo ultrasound was used to image the CEJs of six porcine lower central incisors with a single 20-MHz transducer. A notch was longitudinally created on the enamel as a stable marker, from which the CEJ was measured. Data were acquired along the tooth's axis at 0.4-mm intervals. Time-distance data were bandpass-filtered to enhance signal-to-noise ratio and record density was increased fourfold to 0.1-mm spacing by a frequency-distance interpolation scheme. Reflections from the CEJ were unambiguously identified along with those from enamel, dentin and cementum. The notch-CEJ distances measured by the ultrasound and micro-computed tomography methods correlated strongly (r = 0.996, p < 0.05) and were in good agreement with the 95% lines of agreement between -0.49 and 0.17 mm, as statistically determined by Bland-Altman analysis. The results indicate the potential of ultrasound to be a reliable and non-ionizing technique to image the CEJ.

Accuracy of magnetic resonance imaging-cone beam computed tomography rigid registration of the head: an in-vitro study

OBJECTIVE

To evaluate the performance of cross-modality image registration procedure between magnetic resonance imaging (MRI) and cone beam computed tomography (CBCT).

METHODS

In vitro diagnostic MRI and CBCT images of 5 cadaver swine heads were obtained prospectively. Five radiopaque fiducial markers were attached to each cadaver skull by using resin screws. Automatic MRI-CBCT rigid registrations were performed. The specimens were then scanned using a 3-dimensional (3-D) laser scanner. The 3-D coordinate points for the centroid of the attached fiducial markers from laser scan were identified and considered ground truth. The distances between marker centroids were measured with MRI, CBCT, and MRI-CBCT. Accuracy was calculated by using repeated measures analysis of variance and mean difference values. The registration method was repeated 10 times for each specimen in MRI to measure the average error.

RESULTS

There was no significant difference (P > .05) in mean distances of the markers between all images and the ground truth. The distances' mean difference between MRI, CBCT, and MRI-CBCT and the ground truth were 0.2 ± 1.1 mm, 0.3 ± 1.0 mm, 0.2 ± 1.2 mm, respectively. The detected method error ranged between 0.06 mm and 0.1 mm.

CONCLUSION

The cross-modality image registration algorithm is accurate for head MRI-CBCT registration.