Three-dimensional video recordings: Accuracy, reliability, clinical and research guidelines - Reliability assessment of a 4D camera.

OBJECTIVES: In addition to studying facial anatomy, stereophotogrammetry is an efficient diagnostic tool for assessing facial expressions through 3D video recordings. Current technology produces high-quality recordings but also generates extremely excessive data. Here, we compare various recording speeds for three standardized movements using the 3dMDface camera system, to assess its accuracy and reliability. MATERIALS AND METHODS: A linear and two circular movements were performed using a 3D-printed cube mounted on a robotic arm. All movements were recorded initially at 60 fps (frames/second) and then at 30 and 15 fps. Recording accuracy was tested with best-fit superimpositions of consecutive frames of the 3D cube and calculation of the Mean Absolute Distance (MAD). The reliability of the recordings were tested with evaluation of the inter- and intra-examiner error. RESULTS: The accuracy of movement recordings was excellent at all speeds (60, 30 and 15 fps), with variability in MAD values consistently being less than 1 mm. The reliability of the camera recordings was excellent at all recording speeds. CONCLUSIONS: This study demonstrated that 3D recordings of facial expressions can be performed at 30 or even at 15 fps without significant loss of information. This considerably reduces the amount of produced data facilitating further processing and analyses.

Quantification of temporomandibular joint space in patients with juvenile idiopathic arthritis assessed by cone beam computerized tomography.

OBJECTIVE: To describe a method to calculate the total intra-articular volume (inter-osseous space) of the temporomandibular joint (TMJ) determined by cone-beam computed tomography (CBCT). This could be used as a marker of tissue proliferation and different degrees of soft tissue hyperplasia in juvenile idiopathic arthritis (JIA) patients. MATERIALS AND METHODS: Axial single-slice CBCT images of cross-sections of the TMJs of 11 JIA patients and 11 controls were employed. From the top of the glenoid fossa, in the caudal direction, an average of 26 slices were defined in each joint (N = 44). The interosseous space was manually delimited from each slice by using dedicated software that includes a graphic interface. TMJ volumes were calculated by adding the areas measured in each slice. Two volumes were defined: Ve-i and Vi , where Ve-i is the inter-osseous space, volume defined by the borders of the fossa and Vi is the internal volume defined by the condyle. An intra-articular volume filling index (IF) was defined as Ve-i /Vi , which represents the filling of the space. RESULTS: The measured space of the intra-articular volume, corresponding to the intra-articular soft tissue and synovial fluid, was more than twice as large in the JIA group as in the control group. CONCLUSION: The presented method, based on CBCT, is feasible for assessing inter-osseus joint volume of the TMJ and delimits a threshold of intra-articular changes related to intra-articular soft tissue proliferation, based on differences in volumes. Intra-articular soft tissue is found to be enlarged in JIA patients.

Management of unilateral craniofacial microsomia with orthopaedic functional appliances: A systematic literature review.

The study aimed to summarize current knowledge regarding the use of orthopaedic functional appliances (OFA) in managing unilateral craniofacial microsomia (UCM). The eligibility criteria for the review were (1) assessing use of OFA as a stand-alone treatment and (2) using OFA in combination during or after MDO. The PICO (population, intervention, comparison and outcome) format formulated clinical questions with defined inclusion and exclusion criteria. No limitations concerning language and publication year were applied. Information sources: A literature search of Medline, Scopus, Embase, Cochrane Central Register of Controlled Trials, Web of Science databases without restrictions up to 30 September 2022. The risk of bias was assessed. According to Cochrane and PRISMA guidelines, two independent authors conducted data extraction. The level of evidence for included articles was evaluated based on the Oxford evidence-based medicine database. Due to the heterogeneity of studies and insufficient data for statistical pooling, meta-analysis was not feasible. Therefore, the results were synthesized narratively. A total of 437 articles were retrieved. Of these, nine met inclusion criteria: five assessing OFA and four assessing OFA during or after MDO. There is limited evidence to suggest that stand-alone and combination treatment with OFA is beneficial for treating mild-to-moderate UCM-related dentofacial deformities in short term. No studies assessed the burden of care. In the management of UCM, there is insufficient evidence supporting the efficacy of OFA as a stand-alone treatment or when combined with MDO. Additionally, there is a lack of evidence regarding treatment protocols and the effect on the condyles and the TMJ. The study was registered at Prospero database number CRD42020204969.

Image quality assessment of three cone beam computed tomography scanners-an analysis of the visibility of anatomical landmarks.

BACKGROUND/OBJECTIVES: The aim of this study was to evaluate large field of view (FoV) subjective image quality of three cone-beam computed tomography (CBCT) machines to assess the threshold for reliable diagnostic perceptibility when lowering exposure settings. MATERIALS AND METHODS: One entire cadaver's head was scanned using three CBCT scanners. The largest available FoV of each device, imaging orthodontic relevant structures, was applied. CBCT datasets with different image quality based on standard to minimum scanning parameters were acquired. Five dentists evaluated the visibility of selected anatomical structures of the upper and lower jaw using a 5-point rating scale. RESULTS: Image quality depends on parameters such as a minimum voxel size of 0.2 to 0.4mm or a minimum of 4mA. A reduction in number of images (scanning protocol) reduces image quality. Visualization of different anatomical structures for orthodontic treatment planning requires distinct scanning protocols to support adequate perception of these structures. LIMITATIONS: This study does not account for the evaluation of paediatric anatomical structures due to the availability of cadaver's head. CONCLUSIONS: CBCT scans performed for orthodontic purposes using a large FoV with reduced parameters (400 µm, 2 to 4 mA and low dose protocols) are acceptable for visualization of large anatomical structures. Further lowering these parameters will not be sufficient to view small anatomical structures. Orthodontic indications will have to define specific anatomical structures to choose adequate scanning protocols to reduce dose and ensure reliable diagnostic visibility.

The effect of orthodontic treatment on facial attractiveness: a systematic review and meta-analysis.

BACKGROUND: Facial and smile attractiveness are significant motivating factor for patients to seek orthodontic treatment. Although there is a general belief that orthodontic treatment improves facial appearance, this has yet not been systematically evaluated. OBJECTIVE: The objective of this study was to assess the current evidence on the effect of orthodontic treatment on facial attractiveness. SEARCH METHODS: Systematic and unrestricted search of nine databases were performed up to January 2022. SELECTION CRITERIA: Studies evaluating facial attractiveness before and after orthodontic treatment. DATA COLLECTION AND ANALYSIS: Extracted data included study design and setting, sample size and demographics, malocclusion type, treatment modality, and method for outcome assessment. Risk of bias was assessed with the ROBINS-I tool for non-randomized studies and with RoB-2 for randomized controlled trials (RCTs). Random-effects meta-analyses of mean differences and their 95% confidence intervals (CIs) were performed. RESULTS: Twenty studies were included in data synthesis; three randomized controlled clinical trials and 17 non-randomized clinical studies of retrospective or prospective design. One of the RCTs was found to have low risk of bias, one presented some concerns and the third showed a high risk of bias. All non-randomized studies showed either unclear or high risk of bias. Data syntheses showed that orthodontic treatment improved facial attractiveness ratings by 9% when compared with untreated controls (MD: 9.05/95% CI: 4.71; 13.39). A combination of orthodontics and orthognathic surgery also showed a positive effect of 5.5% (MD: 5.51/95% CI: 1.55; 9.47) when compared with orthodontic treatment alone. There was no difference in effect between extraction and non-extraction treatments (MD: -0.89/ 95% CI: -8.72; 6.94) or between different types of Class II correctors (MD: 2.21/95% CI: -16.51; 20.93). LIMITATIONS: With the exception of two RCTs, included studies were of unclear or low quality. CONCLUSIONS: Orthodontic treatment has a clinically weak effect on facial attractiveness when compared to no treatment. The same is true when a combined orthodontic/surgical treatment is compared to orthodontics alone. REGISTRATION: PROSPERO #: CRD42020169904.

Impact of the COVID-19 pandemic on urgent dental care delivery in a Swiss university center for dental medicine.

OBJECTIVES: This study aimed to assess whether the emergency service of a major Swiss dental institution faced different demands (patient volume, treatment needs, dental care characteristics) during a lockdown, issued to mitigate the COVID-19 pandemic, compared with the weeks before and after. MATERIALS AND METHODS: Data of patients receiving urgent care at a university center for dental medicine (Basel, Switzerland) during the 6-week lockdown, pre-lockdown, and post-lockdown periods were retrospectively evaluated. Statistical analysis involved tests for equal proportions and logistic regression models. The level of significance was set at α=0.05. RESULTS: The study comprised 3109 dental emergency visits in the period from February 2 to June 5, 2020. Daily caseloads increased during lockdown. Abscesses, orthodontic emergencies, and surgical follow-ups were more common during lockdown, whereas the number of dento-alveolar injuries declined (≤0.048). Urgent dental care provision involved intraoral radiographs more frequently in the pre-lockdown period compared with the following weeks (p<0.001). Among all treatments, aerosol-generating procedures dropped from 56.1% (pre-lockdown) to 21.3% during lockdown (p<0.001), while teledentistry follow-ups became more frequent (p<0.001). Patients with comorbidities sought urgent dental care less frequently during the post-lockdown period (p=0.004). CONCLUSIONS: The lockdown significantly impacted the dental emergency service in terms of patients' diagnoses, treatment needs, and the characteristics of the urgent care that was delivered. CLINICAL RELEVANCE: Access to essential dental care must be monitored and safeguarded throughout the COVID-19 pandemic and beyond as deferred care entails risks for serious sequelae and persons with comorbidities may change their dental care-seeking behavior.

In vitro comparison of the torsional load transfer of various commercially available stainless-steel wires used for fixed retainers in orthodontics.

OBJECTIVE: To assess the torsional load transfer of various commercially available stainless-steel wires used for fixed retainers. DESIGN: An in vitro study using a robotic device. SETTING: Department of Pediatric Oral Health and Orthodontics, University of Basel. METHODS: A 10° proclination of a maxillary lateral incisor of a 2-2 retainer was simulated with a robotic device. Eight stainless-steel wires with different shapes (round or rectangular), types (plain, braided, coaxial or chain) and dimensions were selected to measure the torsional load transfer at the adjacent central incisor. The influence of annealing was also tested. RESULTS: The 0.016 × 0.016 and Bond-A-Braid™ wires (0.02645 × 0.01055-inch, 8-stranded, braided) showed the largest relative torsional load transfer (3.7% and 3.3%, respectively). The two multistranded wires - Triple Flex™ and Respond® - showed the smallest values of 1.0% and 0.7%, respectively. The spiral direction of these two multistranded wires affected the load transfer, the twisting showing larger torsional load transfer than the untwisting one. CONCLUSION: The effective torsional load transfer depends on the dimension, shape and type of a wire. Plain and braided retainers were more predictable in torsional load transfer than multistranded retainers, which may have stored more energy in the area between the composite bonding sites. This may explain the unexpected complications reported in multistranded retainers.

The biomechanical evaluation of magnetic forces to drive osteogenesis in newborn's with cleft lip and palate.

This study examined the potential for dental magnets to act as a driving force for osteogenesis in the palate of newborns with a unilateral cleft lip and palate. In the first part of the study dental magnets were arranged in a set up mimicking a distraction device and the curves of the magnetic attraction force versus gap distance curves generated, with and without the presence of palatal rugae tissue in between both sides of the distraction device. The attraction forces ranged from 1 to 12 N depending on the gap distance and the presence of soft tissue in the gap. In the second part of the study these forces were used as input for a 3D finite element model of the palate of a newborn affected by unilateral cleft lip and palate. In the analysis of load transfer, it was found that the strains generated by a magnetically induced distraction exceed 1,500 µstrain suggesting that bone locally is submitted to mild overload leading to bone apposition.

Corticotomy affects both the modus and magnitude of orthodontic tooth movement.

Objective: To analyze whether the decreased bone density due to the manipulation of bone remodeling rate has an influence on the type of the planned tooth movement. Materials and methods: A finite element model of a lower incisor has been developed. The density of the alveolar bone surrounding the tooth has been assumed to simulate the one occurring after corticotomy to increase tooth movement rate. Moment-to-force ratios corresponding to three different types of movements have been simulated; uncontrolled tipping, translation, and root movement. The three tooth movements have been analyzed in both corticotomized and non-corticotomized simulations, and the final effects on the amount and type of tooth movement analyzed. The stress and strain levels in the periodontal ligament have been analyzed too. Results: The amount of tooth movement obtained in case of lower bone density is higher in all types of movement simulations. The centre of rotation of the movement shifts more apically in case of translation, controlled and uncontrolled tipping. In the corticotomy simulations, the compressive stresses in the periodontal ligament decreased while the tensile stresses increased. Conclusion: A decreased bone density influences not only the amount of tooth movement, but also its type. This study suggests that the moment-to-force ratios used in conventional orthodontics should be modified in case of techniques that decrease bone density to enhance tooth movement rate.

The Effect of Enamel Sandblasting on Enhancing Bond Strength of Orthodontic Brackets: A Systematic Review and Meta-analysis.

PURPOSE: To critically appraise the evidence regarding the effect of enamel sandblasting on the bond strength of orthodontic brackets on either the labial or lingual tooth surface. MATERIALS AND METHODS: An electronic database search of published and unpublished literature was performed. Search terms included sandblasting, enamel abrasion, tooth surface, bond strength, bond failure, and adhesive remnant; data were extracted in standardized piloted forms. Risk of bias was assessed using the Cochrane risk of bias tool, adapted for in vitro studies where necessary. RESULTS: Of the 81 articles initially retrieved, 13 were eligible for inclusion in the systematic review. All of the latter were in vitro studies with unclear risk of bias primarily due to unclear reporting of blinding of outcome assessors. Eight studies assessed the combined effect of enamel sandblasting and etching, while only five evaluated the isolated effect of sandblasting on the buccal enamel surface. In view of the apparently heterogeneous study settings, intervention protocols, specimen preparation and storage sequences, only two studies were deemed eligible for quantitative synthesis. Random effects meta-analysis revealed no evidence to support sandblasting prior to etching over etching alone with regard to shear bond strength of orthodontic brackets bonded in vitro to lingual enamel surfaces of extracted premolars (standardized mean difference: 0.36; 95% CI: -0.21, 0.94; p = 0.22). CONCLUSIONS: The findings of the present study cannot support lingual enamel sandblasting prior to etching for augmentation of the bond strength of orthodontic brackets.

Torque resistance of different stainless steel wires commonly used for fixed retainers in orthodontics.

OBJECTIVE: Movements of teeth splinted by fixed retention wires after orthodontic treatment have been observed. The aetiological factors for these movements are unknown. The aim of this in vitro study was to compare the resistance to torque of different stainless steel wires commonly used for fixed retainers in orthodontics. MATERIALS AND METHODS: Torquing moments acting on a retainer wire were measured in a mechanical force testing system by applying buccal crown torque to an upper lateral incisor in both a 3-teeth and in a 2-teeth setup. Seven stainless steel wires with different shape, type (plain, braided, coaxial, or chain) and dimensions were selected for this study. RESULTS: For a torquing angle of 16.2° in the 3-teeth setup torsion moments can vary between 390 cNmm and 3299 cNmm depending on the retainer wire. For the 2-teeth setup the torsion moments are much smaller. Exposure to the flame of a butane-gas torch for 10 seconds to anneal the wire reduces the stiffness of the retainer wire. CONCLUSIONS: Clinicians must select wires for fixed retainers very carefully since the difference in resistance to torque is large. A high level of torque control can be achieved with a plain 0.016 × 0.016-inch or a braided 0.016 × 0.022-inch stainless steel wire. A tooth attached by a retainer wire to only one neighbouring tooth is less resistant to torque than a tooth connected to two neighbouring teeth. Annealing a retainer wire with a flame reduces the stiffness of the wire markedly and can lead to a non-uniform and non-reproducible effect.

Treatment strategies for infraoccluded dental implants.

Single-tooth implants in the maxillary anterior region have the highest risk of esthetic complications from infrapositioning due to continuing maxillary growth and the eruption of adjacent teeth. Although the placement of anterior single-tooth implants should normally be postponed, particularly girls and young women with a hyperdivergent growth pattern, if an infraposition of an implant is present, then thorough examination and strategic planning are required. According to the severity, the strategic treatment options are as follows: simple retention; adjustment or replacement of the implant restoration, possibly including adjacent teeth; surgical implant repositioning by segmental osteotomy combined with osseodistraction; or submergence or removal of the implant. With the patient presented, an interdisciplinary approach that combined orthodontic alignment, surgical segmental osteotomy, distraction osteogenesis, and restorative features offered the opportunity to realign the adjacent teeth into the arch and to harmonize the gingival contour by means of continuous soft tissue enlargement and adaptation.

Antimicrobial effect of probiotic bacteriocins on Streptococcus mutans biofilm in a dynamic oral flow chamber model - an in vitro study.

Aim: To determine the antimicrobial activity of the bacteriocin-producing probiotic strains Streptococcus salivarius K12 and Streptococcus salivarius M18 alone or in combination against caries-associated Streptococcus mutans. Methods: Antimicrobial activity of S. salivarius K12 and/or S. salivarius M18 against S. mutans ATCC 25175 growth and biofilm formation on hydroxyapatite (HA) discs was determined in a flow chamber model by recording the colony forming units (CFU/ml) after 48 h of co-cultivation. The biofilm was analyzed by scanning electron microscopy (SEM) and by confocal laser scanning microscopy (CLSM). Additionally, the simultaneous antagonism assay was used to assess the inhibitory effect of S. salivarius K12 and/or S. salivarius M18 against S. mutans ATCC 25175 and 21 clinical isolates of S. mutans. Results: Co-cultivation of S. mutans and S. salivarius K12 and/or S. salivarius M18 led to the inhibition of S. mutans viability, thereby, preventing its biofilm formation on HA discs. Furthermore, S. salivarius K12 and S. salivarius M18 exhibited antimicrobial activity against most clinical isolates of S. mutans. Conclusion: The in vitro flow chamber system used in this study allows the simulation of time-dependent administration of S. salivarius probiotic strains, either alone or in combination, to investigate the prevention of S. mutans biofilm formation in a standardized model.

The use of CBCT in orthodontics with special focus on upper airway analysis in patients with sleep-disordered breathing.

Applications of cone-beam CT (CBCT) in orthodontics have been increasingly discussed and evaluated in science and practice over the last two decades. The present work provides a comprehensive summary of current consolidated practice guidelines, cutting-edge innovative applications, and future outlooks about potential use of CBCT in orthodontics with a special focus on upper airway analysis in patients with sleep-disordered breathing. The present scoping review reveals that clinical applications of CBCT in orthodontics are broadly supported by evidence for the diagnosis of dental anomalies, temporomandibular joint disorders, and craniofacial malformations. On the other hand, CBCT imaging for upper airway analysis-including soft tissue diagnosis and airway morphology-needs further validation in order to provide better understanding regarding which diagnostic questions it can be expected to answer. Internationally recognized guidelines for CBCT use in orthodontics are existent, and similar ones should be developed to provide clear indications about the appropriate use of CBCT for upper airway assessment, including a list of specific clinical questions justifying its prescription.

Incidence of Orofacial Manifestations of Juvenile Idiopathic Arthritis From Diagnosis to Adult Care Transition: A Population-Based Cohort Study.

OBJECTIVE: To estimate the cumulative incidences of orofacial conditions related to temporomandibular joint (TMJ) juvenile idiopathic arthritis (JIA) between diagnosis in childhood to transition into adult care, and to identify features in JIA associated with TMJ involvement. METHODS: A population-based cohort analysis was conducted of patients with JIA involving longitudinal data on orofacial health from 2000 to 2018. Regardless of TMJ status, the patients were referred to the Regional Specialist Craniofacial Clinic of Western Denmark for routine orofacial examinations. Data collection included information about disease-specific background characteristics, TMJ involvement, JIA-induced dentofacial deformity, and orofacial symptoms and dysfunction. RESULTS: A total of 613 patients were followed up with a mean clinical TMJ observation time of 4.0 years. From JIA onset to transition into adult care, the cumulative incidence of patients with JIA involvement of the TMJ was 30.1%. Furthermore, 20.6% of the cohort had developed arthritis-induced dentofacial deformity. A substantial proportion of the cohort experienced several events with orofacial symptoms (23.5%) and dentofacial dysfunction (52%). Young age at diagnosis (<9 years), female gender, and antinuclear antibody positivity were significantly associated with TMJ involvement. CONCLUSION: Orofacial signs and symptoms were frequent findings in children and adolescents with JIA. TMJ involvement was seen in 30.1% of the cohort; and 20.6% of the total cohort developed JIA-related dentofacial deformity before transition into adult care. This is the first population-based study in the era of available biologic treatments to document these frequent orofacial complications in children with JIA.

Accuracy of facial skeletal surfaces segmented from CT and CBCT radiographs.

The accuracy of three-dimensional (3D) facial skeletal surface models derived from radiographic volumes has not been extensively investigated yet. For this, ten human dry skulls were scanned with two Cone Beam Computed Tomography (CBCT) units, a CT unit, and a highly accurate optical surface scanner that provided the true reference models. Water-filled head shells were used for soft tissue simulation during radiographic imaging. The 3D surface models that were repeatedly segmented from the radiographic volumes through a single-threshold approach were used for reproducibility testing. Additionally, they were compared to the true reference model for trueness measurement. Comparisons were performed through 3D surface approximation techniques, using an iterative closest point algorithm. Differences between surface models were assessed through the calculation of mean absolute distances (MAD) between corresponding surfaces and through visual inspection of facial surface colour-coded distance maps. There was very high reproducibility (approximately 0.07 mm) and trueness (0.12 mm on average, with deviations extending locally to 0.5 mm), and no difference between radiographic scanners or settings. The present findings establish the validity of lower radiation CBCT imaging protocols at a similar level to the conventional CT images, when 3D surface models are required for the assessment of facial morphology.

Management of Orofacial Manifestations of Juvenile Idiopathic Arthritis: Interdisciplinary Consensus-Based Recommendations.

Involvement of the temporomandibular joint (TMJ) is common in juvenile idiopathic arthritis (JIA). TMJ arthritis can lead to orofacial symptoms, orofacial dysfunction, and dentofacial deformity with negative impact on quality of life. Management involves interdisciplinary collaboration. No current recommendations exist to guide clinical management. We undertook this study to develop consensus-based interdisciplinary recommendations for management of orofacial manifestations of JIA, and to create a future research agenda related to management of TMJ arthritis in children with JIA. Recommendations were developed using online surveying of relevant stakeholders, systematic literature review, evidence-informed generation of recommendations during 2 consensus meetings, and Delphi study iterations involving external experts. The process included disciplines involved in the care of orofacial manifestations of JIA: pediatric rheumatology, radiology, orthodontics, oral and maxillofacial surgery, orofacial pain specialists, and pediatric dentistry. Recommendations were accepted if agreement was >80% during a final Delphi study. Three overarching management principles and 12 recommendations for interdisciplinary management of orofacial manifestations of JIA were outlined. The 12 recommendations pertained to diagnosis (n = 4), treatment of TMJ arthritis (active TMJ inflammation) (n = 2), treatment of TMJ dysfunction and symptoms (n = 3), treatment of arthritis-related dentofacial deformity (n = 2), and other aspects related to JIA (n = 1). Additionally, a future interdisciplinary research agenda was developed. These are the first interdisciplinary recommendations to guide clinical management of TMJ JIA. The 3 overarching principles and 12 recommendations fill an important gap in current clinical practice. They emphasize the importance of an interdisciplinary approach to diagnosis and management of orofacial manifestations of JIA.

Smile Reproducibility and Its Relationship to Self-Perceived Smile Attractiveness.

The reproducibility of facial expressions has been previously explored, however, there is no detailed information regarding the reproducibility of lip morphology forming a social smile. In this study, we recruited 93 young adults, aged 21−35 years old, who agreed to participate in two consecutive study visits four weeks apart. On each visit, they were asked to perform a social smile, which was captured on a 3D facial image acquired using the 3dMD camera system. Assessments of self-perceived smile attractiveness were also performed using a VAS scale. Lip morphology, including smile shape, was described using 62 landmarks and semi-landmarks. A Procrustes superimposition of each set of smiling configurations (first and second visit) was performed and the Euclidean distance between each landmark set was calculated. A linear regression model was used to test the association between smile consistency and self-perceived smile attractiveness. The results show that the average landmark distance between sessions did not exceed 1.5 mm, indicating high repeatability, and that females presented approximately 15% higher smile consistecy than males (p < 0.05). There was no statistically significant association between smile consistency and self-perceived smile attractiveness (η2 = 0.015; p = 0.252), when controlling for the effect of sex and age.

The Effect of Ligature Type on Lateral Tooth Movement during Orthodontic Treatment with Lingual Appliances-An In Vitro Study.

(1) Background: One of the most challenging parts in lingual orthodontics is the control and correction of the tip of anterior teeth, due to the occlusal open vertical slot of the incisors in lingual systems. The presented experimental in-vitro study was performed to determine the maximal tipping moment of the anterior teeth between two types of lingual brackets, the Incognito™ Appliance System (Incognito, TOP-Service, Bad Essen, Germany) and Tip-Bar™ system (Incognito, TOP-Service, Bad Essen, Germany). Furthermore, twelve different ligation methods and two different ligature materials were investigated. (2) Methods: The measurement was performed by assessing the stiffness and ultimate strength of the ligature in a uniaxial material testing machine (Instron, Norwood, MA, USA) using a 0.025 × 0.018 inch stainless steel wire. (3) The results showed that the highest precision for control tipping of anterior teeth was determined for the 0.010 inch Stainless Steel Tie (Pelz and Partner). Furthermore, the Tip-Bar™ brackets increased the maximal moment by 33.8% for elastic and steel ligatures. (4) Conclusions: The lateral tooth movement is highly dependent on the type of ligature and applied material during orthodontic treatment with lingual appliances. The use of 0.010 inch steel ligatures and the Tip-Bar™ bracket design results in better alignment in the anterior teeth segment.

Effect of field of view (FOV) positioning and shielding on radiation dose in paediatric CBCT.

OBJECTIVE: To investigate the effect of two different large field of view (FOV) positions in the vertical dimension and shielding (thyroid collar and eyeglasses) on the effective dose and the local doses of various sites of the craniofacial complex. METHODS: Organ doses and effective doses were calculated based on the measured doses using 27 pairs of thermoluminescent dosemeters in a paediatric tissue-equivalent of a 10-year-old anthropomorphic phantom. The large FOV of the 3D Accuitomo F170 CBCT scanner was used to image parts of the craniofacial complex. Six protocols were performed: (A) cranial position without shielding; (B) cranial position with shielding; (C) caudal position without shielding; (D) caudal position with shielding, (E) similar to C with 3600 rotation and (F) similar to D with 360° rotation. Measurements were obtained in duplicate, and the relative δ value (%) was applied to compare the average doses between the protocols. RESULTS: Changing the FOV position from cranial to caudal without using shielding resulted in an increase of the effective dose of 18.8%. Use of shielding in the caudal position reduced the dose by 31.6%. Local absorbed dose of the thyroid had the most relevant impact on calculation of the effective dose, followed by oesophagus, bone marrow and bone surfaces, especially when comparing the different protocols. CONCLUSIONS: Application of shielding devices for thyroid in combination with a most caudal positioning of FOV led to the lowest local absorbed doses as well as the effective dose in a child phantom model.