Root Position Research Articles

Hand measurement and analysis based on image and mark watershed algorithm

PurposeThe purpose of this paper is to propose a method for hand measurement based on image and marker watershed algorithm, and combine the data to analyze the shape and characteristics of the hand.Design/methodology/approachA portable hand image capturing instrument was designed and manufactured, and the hand images and dimensions of 328 young men in Zhejiang area were obtained. The outer contour curve of the hand and the key points of finger root, fingertip, wrist and knuckle position were extracted. Then, the size of each hand part was calculated. The hand data obtained from the two-dimensional image was compared with the manual measurement data. Finally, the hands were classified according to the measurement data, and the relationship between hand control size and hand length, hand width and the relationship between hand length and height were explored.FindingsThe data comparison results show that the two measurement methods have high data consistency and are replaceable. In addition, analyzing the data obtained four major characteristic factors that affect the shape of the hand, divided the hands of young men in Zhejiang into five categories, and obtained the regression equations of basic hand size, hand length and hand width, and obtained the regression equation of hand length and height.Originality/valueThe method proposed in this study to obtain hand size based on the image and mark watershed algorithm has lower requirements on the external environment and testers, conforms to the development trend of applying artificial intelligence to anthropometric engineering and provides a useful reference value for data collection of gloves specification design. In addition, the results of data analysis can provide a valuable reference basis for consumer hand shape predictions, which can be used to guide the research and production of hand instruments, the design of specifications series and the purchase of hand products.

Relationship between anterior maxillary tooth sagittal root position and periodontal phenotype: a clinical and tomographic study.

To evaluate the relationship between the tomographic sagittal root position (SRP) of maxillary anterior teeth and periodontal phenotype (PP). Seventy volunteers (420 teeth) were evaluated. Clinical and photographic exams included the evaluation of gingival phenotype (GP) by transparency of the periodontal probe, keratinized tissue width (KTW), gingival architecture, tooth shape, and papilla height (PH). Soft tissue tomographic scan (ST-CBCT) measurements included the SRP classification, GP, gingival thickness in the tissue zone (GT-TZ) and in the bone zone (GT-BZ), buccal bone thickness (BBT), and the distances from the gingival margin and from cementoenamel junction to the buccal bone crest (GM-BBC and CEJ-BBC). Kruskal-Wallis test and a linear regression analysis model were used. The frequency of SRP over the 420 teeth was 65.2% (class I), 9.3% (class II), 0.7% (class III), and 24.8% (class IV). Linear regression analysis showed that SRP is related to PP (p < 0.05). Significantly different measurements of PP parameters were found in SRP classes. The higher and lower GT and BBT were found in classes II and I, respectively. Class IV presented the highest KTW, PH, CEJ-BBC, and GM-BBC. Central incisors (CI) classes I and II were most frequently square-shaped, while 89% of CI Class IV were triangular-shaped. The SRP of maxillary anterior teeth is related to periodontal phenotype. Clinical and ST-CBCT individual analysis of PP and SRP may be helpful for an esthetic and functional treatment plan based on soft and hard tissue thickness and tooth positioning.

Neutron computed laminography yields 3D root system architecture and complements investigations of spatiotemporal rhizosphere patterns

PurposeRoot growth, respiration, water uptake as well as root exudation induce biogeochemical patterns in the rhizosphere that can change dynamically over time. Our aim is to develop a method that provides complementary information on 3D root system architecture and biogeochemical gradients around the roots needed for the quantitative description of rhizosphere processes.MethodsWe captured for the first time the root system architecture of maize plants grown in rectangular rhizotrons in 3D using neutron computed laminography (NCL). Simultaneously, we measured pH and oxygen concentration using fluorescent optodes and the 2D soil water distribution by means of neutron radiography. We co-registered the 3D laminography data with the 2D oxygen and pH maps to analyze the sensor signal as a function of the distance between the roots and the optode.ResultsThe 3D root system architecture was successfully segmented from the laminographic data. We found that exudation of roots in up to 2 mm distance to the pH optode induced patterns of local acidification or alkalization. Over time, oxygen gradients in the rhizosphere emerged for roots up to a distance of 7.5 mm.ConclusionNeutron computed laminography allows for a three-dimensional investigation of root systems grown in laterally extended rhizotrons as the ones designed for 2D optode imaging studies. The 3D information on root position within the rhizotrons derived by NCL explained measured 2D oxygen and pH distribution. The presented new combination of 3D and 2D imaging methods facilitates systematical investigations of a wide range of dynamic processes in the rhizosphere.

Influence of sagittal root positions on the stress distribution around custom-made root-analogue implants: a three-dimensional finite element analysis

BackgroundStress concentration may cause bone resorption even lead to the failure of implantation. This study was designed to investigate whether a certain sagittal root position could cause stress concentration around maxillary anterior custom-made root-analogue implants via three-dimensional finite element analysis.MethodsThe von Mises stresses in the bone around implants in different groups were compared by finite element analysis. Six models were constructed and divided into two groups through Geomagic Studio 2012 software. The smooth group included models of unthreaded custom-made implants in Class I, II or III sagittal root positions. The threaded group included models of reverse buttress-threaded implants in the three positions. The von Mises stress distributions and the range of the stresses under vertical and oblique loads of 100 N were analyzed through ANSYS 16.0 software.ResultsStress concentrations around the labial lamella area were more prominent in the Class I position than in the Class II and Class III positions under oblique loading. Under vertical loading, the most obvious stress concentration areas were the labial lamella and palatal apical areas in the Class I and Class III positions, respectively. Stress was relatively distributed in the labial and palatal lamellae in the Class II position. The maximum von Mises stresses in the bone around the custom-made root-analogue implants in this study were lower than around traditional implants reported in the literature. The maximum von Mises stresses in this study were all less than 25 MPa in cortical bone and less than 6 MPa in cancellous bone. Additionally, compared to the smooth group, the threaded group showed lower von Mises stress concentration in the bone around the implants.ConclusionsThe sagittal root position affected the von Mises stress distribution around custom-made root-analogue implants. There was no certain sagittal root position that could cause excessive stress concentration around the custom-made root-analogue implants. Among the three sagittal root positions, the Class II position would be the most appropriate site for custom-made root-analogue implants.

A Critical Review of the Differential Diagnosis of Root Fracture Line in CBCT scans.

The objective of this critical review of literature is to discuss relevant clinical factors associated with root fractures (RF) visualized by using a new CBCT software. RF constitutes a common occurrence and a challenge in clinical practice, in which the diagnosis becomes essential for the definition of rapid and precise decision-making. The characterization of RF may involve different aspects, such as orientation of the fracture line (horizontal, vertical, oblique), root position of the fracture (cervical, middle, apical third), fracture's coronal-radicular position (coronary, coronal-radicular, radicular), continuity of the fracture (crack, incomplete fracture, complete), bone extension of the fracture (supraosseous, bone level, infraosseous fracture). Imaging examinations have been routinely used to aid in the RF diagnosis. Even with high-resolution cone-beam computed tomography (CBCT) scans, many doubts often remain about the diagnostic outcome. Many interferences in the analysis of image quality to determine the diagnosis are identified, such as the sharpness, the noise, light and dark artifacts, among others. The professional's knowledge is essential for identifying the different patterns of fracture lines and their repercussions on adjacent bone tissues, as well as for the analysis of artifacts that may hide or show similarities to fracture lines. Fractures lines and root fractures that may be associated with phantom conditions that mimic fractures should be carefully analyzed. CBCT is the exam indicated to identify a root fracture. It is also added to the success of the diagnosis that the professional has scientific knowledge, training and mastery of advanced CBCT software.

Potential Circumferential Bone Engagement following Tooth Extraction in the Posterior Mandible: Computed Tomography Assessment.

Background and Objectives: Immediate implant placement (IIP) is a popular surgical procedure with a 94.9–98.4% survival rate and 97.8–100% success rate. In the posterior mandible, it poses a risk of injury to adjacent anatomical structures if the implant engages apical bone. This study sought to assess the implant dimensions that allow for circumferential bone engagement at each position in the posterior mandible without additional apical drilling. Materials and Methods: An observational, cross-sectional study design was used. The pre-extraction cone beam computed tomography scans of 100 candidates for IIP were analyzed. Measurements of each root of the posterior mandibular second premolar, first molar, and second molar were taken from three aspects: buccolingual, mesiodistal, and vertical. Two-sided p values < 0.05 were considered statistically significant. Results: A total of 478 mandibular teeth and 781 roots were assessed. Based on Straumann® BLX/BLT implant-drilling protocols, predicted rates of radiological circumferential engagement (RCE) were 96% for implants 5 mm in diameter in the second premolar root position; 94% for implants 4.0–4.2 mm in diameter in the first molar root position; and 99% for implants 4.5–4.8 mm in diameter in the second molar root position. Corresponding rates of achieving an available implant length (AIL) of 10 mm were 99%, 90%, and 86%. Patients <40 years old were at higher risk of lower RCE and lower AIL (p < 0.005) than older patients for all roots measured. Conclusions: The high primary stability prediction rates based on the calculation of RCE and AIL support the use of IIPs without further apical drilling in the posterior mandible in most cases.

Assessing Confidence in Root Placement on Phylogenies: An Empirical Study Using Nonreversible Models for Mammals.

Using time-reversible Markov models is a very common practice in phylogenetic analysis, because although we expect many of their assumptions to be violated by empirical data, they provide high computational efficiency. However, these models lack the ability to infer the root placement of the estimated phylogeny. In order to compensate for the inability of these models to root the tree, many researchers use external information such as using outgroup taxa or additional assumptions such as molecular clocks. In this study, we investigate the utility of nonreversible models to root empirical phylogenies and introduce a new bootstrap measure, the rootstrap, which provides information on the statistical support for any given root position. [Bootstrap; nonreversible models; phylogenetic inference; root estimation.]

A Digital Approach to Evaluating Tooth Root Position Without Repeated Cone-beam Computed Tomography Scans.

The purpose of this report is to introduce a digital approach to evaluating three-dimensional root position without radiation using virtual tooth model which is composed of intraoral-scanned crown and cone-beam computed tomography (CBCT)-scanned root. Successful treatment depends not only on the formulation of a proper initial diagnosis, but also on an accurate assessment of treatment progress, which should include the monitoring and evaluation of tooth and root movements. Although CBCT allows the visualization of the true root position and angulation in three-dimensions, the obtaining of serial CBCT scans for this purpose is associated with concerns regarding radiation exposure. This report introduces a method for monitoring three-dimensional root position following tooth movement during treatment that does not require repeated CBCT scans. This method uses an individual virtual tooth model composed of intraoral-scanned crowns and CBCT-scanned roots. When an evaluation of root positions is needed during treatment, only additional intraoral scan is needed and is integrated into the tooth model; this allows root positions to be estimated without the need for another CBCT scan. The use of a virtual tooth model can potentially allow clinicians to accurately monitor tooth position in routine clinical practice, without the hazards of increased radiation exposure.

A Novel Method of Hyperbola Recognition in Ground Penetrating Radar (GPR) B-Scan Image for Tree Roots Detection

Ground penetrating radar (GPR), as a newly nondestructive testing technology (NDT), has been adopted to explore the spatial position and the structure of the tree roots. Due to the complexity of soil distribution and the randomness of the root position in the natural environment, it is difficult to locate the root in the GPR B-Scan image. In this study, a novel method for root detection in the B-scan image by considering both multidirectional features and symmetry of hyperbola was proposed. Firstly, a mixed dataset B-Scan images were employed to train Faster RCNN (Regions with CNN features) to obtain the potential hyperbola region. Then, the peak area and its connected region were filtered from the four directional gradient graphs in the proposed region. The symmetry test was applied to segment the intersecting hyperbolas. Finally, two rounds of coordinate transformation and line detection based on Hough transform were employed for the hyperbola recognition and root radius and position estimation. To validate the effectiveness of this approach for tree root detection, a mixed dataset was made, including synthetic data from gprMax as well as field data collected from 35 ancient tree roots and fresh grapevine controlled experiments. From the results of hyperbola recognition as well as the estimation for the radius and position of the root, our method shows a significant effect in root detection.

Molecular Phylogenesis and Spatiotemporal Spread of SARS-CoV-2 in Southeast Asia.

Background: The ongoing coronavirus disease 2019 (COVID-19) pandemic has posed an unprecedented challenge to public health in Southeast Asia, a tropical region with limited resources. This study aimed to investigate the evolutionary dynamics and spatiotemporal patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the region.Materials and Methods: A total of 1491 complete SARS-CoV-2 genome sequences from 10 Southeast Asian countries were downloaded from the Global Initiative on Sharing Avian Influenza Data (GISAID) database on November 17, 2020. The evolutionary relationships were assessed using maximum likelihood (ML) and time-scaled Bayesian phylogenetic analyses, and the phylogenetic clustering was tested using principal component analysis (PCA). The spatial patterns of SARS-CoV-2 spread within Southeast Asia were inferred using the Bayesian stochastic search variable selection (BSSVS) model. The effective population size (Ne) trajectory was inferred using the Bayesian Skygrid model.Results: Four major clades (including one potentially endemic) were identified based on the maximum clade credibility (MCC) tree. Similar clustering was yielded by PCA; the first three PCs explained 46.9% of the total genomic variations among the samples. The time to the most recent common ancestor (tMRCA) and the evolutionary rate of SARS-CoV-2 circulating in Southeast Asia were estimated to be November 28, 2019 (September 7, 2019 to January 4, 2020) and 1.446 × 10−3 (1.292 × 10−3 to 1.613 × 10−3) substitutions per site per year, respectively. Singapore and Thailand were the two most probable root positions, with posterior probabilities of 0.549 and 0.413, respectively. There were high-support transmission links (Bayes factors exceeding 1,000) in Singapore, Malaysia, and Indonesia; Malaysia involved the highest number (7) of inferred transmission links within the region. A twice-accelerated viral population expansion, followed by a temporary setback, was inferred during the early stages of the pandemic in Southeast Asia.Conclusions: With available genomic data, we illustrate the phylogeography and phylodynamics of SARS-CoV-2 circulating in Southeast Asia. Continuous genomic surveillance and enhanced strategic collaboration should be listed as priorities to curb the pandemic, especially for regional communities dominated by developing countries.

Retrospective Analysis on Inferior Third Molar Position by Means of Orthopantomography or CBCT: Periapical Band-Like Radiolucent Sign

Background: Orthopantomography (OPG) is usually used as a primary diagnostic radiological exam in the planning of third molar surgery because it is deeply available in dental clinics and has lower radiation doses compared to Cone-beam computed tomography (CBCT). The OPG provides a bi-dimensional image, but several radiological signs have been proposed to study the position of the lower third molar and to predict surgical risks. Methods: Patients were divided into two groups, the OPG with a radiolucent area (D-group) and the OPG without any sign (C-group) in correspondence of inferior wisdom tooth roots. Results: The mean distance between the inferior third molar root and the lingual cortical mandibular bone was −1.09 ± 1.5 mm. The nearness of the root that is less than 1 mm was more frequent in the D-group (84.85%) compared to the C-group (14.58%) with statistical significance (Odd ratio: 32.8) using the Chi-square test. Conclusions: When the root of the impacted inferior third molar is impacted into the lingual cortical plate, a periapical band-like radiolucent sign may appear in the OPG image. It could be useful for the prediction of root position and surgical risks.

Failure Analysis of Worm Gear in Worm Transmission

The failure cause of the worm drive in the NMRV reducer of the grounding knife-switch mechanism of State Grid was analyzed in this paper. The macroscopic analysis, chemical composition inspection, microscopic metallographic observation, hardness test, SEM analysis were carried out to evaluate the worm gear failure mechanism. The stress distributions of the tooth flank using dynamic contact finite element simulation were obtained based on ANSYS Workbench software. The results showed that an initial crack at the root position of softer worm gear was caused by excessively high impact at the initial stage of meshing in the worm drive, whose value was 308MPa higher than the allowable contact stress of 220MPa. The main reason for the hardness of the worm gear decreasing was that the amount of (α+δ) eutectoids fell and distributed unevenly.

Observing the Eruption of Canine After Secondary Alveolar Bone Grafting

Alveolar bone grafting is undertaken to provide stability to the dental arch and facilitate the eruption of permanent canine as teeth in the line of cleft usually have an altered pattern of eruption. The purpose of this study was to assess the eruption status and the change in the position and pattern of canine eruption after secondary alveolar bone grafting. An ambispective cohort study was conducted in patients operated for alveolar bone grafting with unilateral/bilateral alveolar cleft between the age of 9 to 13 years using autogenous iliac crest bone graft. The predictor variables of interest include the preoperative eruption status of canine (completely erupted/partially erupted/unerupted), stage of root development (one-third/two-third/more than two-third/complete) and position (vertical/lateral/buccopalatal) of the canine. The primary outcome variable is the eruption status of the canine (completely erupted/partially erupted/unerupted) at 6 months postoperatively. Secondary outcome variables include the stage of root development, change in the vertical, lateral and buccopalatal position of the canine observed in the first 6 months postoperatively with follow-up at 1 and 3 months. Another secondary outcome variable was the status of bone graft at 6 months postoperatively. Statistical analysis was done using Spearman's rank correlation and ANOVA chi-square test. The study sample consisted of 30 non-syndromic alveolar cleft patients with a mean age of 11.9 years, out of which partial and complete eruption of canine was seen in 43.33 and 36.67%, respectively. The canine was unerupted in 20% of the cases (P=.001). There was evidence of continued root development through the grafted bone. No significant change in the angulation of canine was observed in the postoperative period. Significant change in the eruption status and root development of canine with no statistically significant change in the vertical and lateral angulation during eruption was observed. Identifying these risk factors by continuous postoperative monitoring will help in identifying the malposition at an early stage.

Rotational Position of the Aortic Root is Associated with Increased Aortic Dimensions in Marfan and Loeys-Dietz Syndrome.

Progressive aortic dilation is common in Marfan syndrome (MFS) and Loeys-Dietz syndrome (LDS). Risk factors for progression are poorly understood. Normal variation in the aortic root (AoR) rotational position relative to the left ventricular base may impact this risk. We aimed to assess the relationship between the rotational position of the AoR and aortic dimensions in this population. Patients with a genetic diagnosis of MFS or LDS were included. AoR and ascending aorta (AAo) dimensions were measured from the first and most recent transthoracic echocardiogram. The AoR rotational angle was measured in the parasternal short-axis plane in diastole. Linear regression was used to study the correlation between AoR rotation angle and aortic dimensions. 53 MFS and 14 LDS patients were included (age 11.5 ± 5.8years at first TTE and 21.2 ± 7.2years at most recent, 68% male). The mean indexed AoR and AAo values were 2.26 ± 0.58cm/m2 and 1.64 ± 0.35cm/m2 at the first TTE and 1.98 ± 0.39cm/m2 and 1.45 ± 0.25cm/m2 at the most recent TTE, respectively. The mean AoR rotational angle was 8 ± 14°. AoR rotational angle was central (-9 to + 14°) in 42, clockwise (≥ + 15°) in 19, and counterclockwise (≤ -10°) in 6. The six outliers with counterclockwise position were excluded. There was a positive association between the AoR rotation angle and most recent TTE indexed AoR (r2 = 0.08, p = 0.02) and AAo sizes (r2 = 0.08, p = 0.02). There was no association between AoR rotational angle and rate of change in indexed AoR size (p = 0.8). There was a positive association between AoR rotation angle and rate of change in indexed AAo size (r2 = 0.10, p = 0.01). There is an association between clockwise rotational position of the AoR and increased AoR and AAo dimensions in children and young adults with MFS and LDS patients. The rotational position of the AoR may guide follow-up in these patient populations. However, this potential risk factor for dilation warrants further investigation.

Nomogram prediction of vulnerable periodontal condition before orthodontic treatment in the anterior teeth of Chinese patients with skeletal Class III malocclusion

Objective To establish and verify models predictive of thin periodontal phenotype and alveolar fenestration/dehiscence in the anterior teeth of patients with skeletal Class III malocclusion. Material and methods Retrospective data of 669 anterior teeth (305 in maxillae and 364 in mandibles) from 80 patients with skeletal Class III malocclusion before augmented corticotomy were collected. Distribution of thin periodontal phenotype and alveolar fenestration and dehiscence were evaluated and their associations with potential influencing factors were explored using univariate and multivariate analyses. The predictive models were visualized as nomograms, the accuracy of which was tested by receiver operating curve analyses. Results Thin phenotype was associated with Mazza bleeding index, sex, tooth type, probing depth and width of keratinized gingiva (WKG). Labial dehiscence was associated with age, jaw, labial bone thickness, mandibular plane angle, sagittal root position (SRP), sex, tooth type, and WKG. Labial fenestration was associated with sex, tooth type, SRP, and periodontal phenotype. The areas under the curves of nomogram prediction models for periodontal phenotype, alveolar dehiscence, and alveolar fenestration were 0.84, 0.81, and 0.73, respectively. Conclusions Female sex, lateral incisor, and limited WKG may be risk factors for thin periodontal phenotype. Age, canine, male sex, mandible, thin labial bone thickness, and root positioned against the labial plate may be risk factors for labial dehiscence; and female sex, thick phenotype, root positioned against the labial plate, lateral incisor, and canine may be risk factors for labial fenestration. The predictive performance of the models was acceptable.

Experience with the Freestyle Valve: A Versatile Option

Objective: The Medtronic Freestyle bioprosthesis is a stentless porcine aortic root. It provides a versatile implantation option either as a full root replacement or a sub-coronary aortic valve replacement. In this study we present our experience with the Freestyle valve in all circumstances over a 10-year period. Methods: All consecutive patients (n=70) undergoing Freestyle valve implantation either in the isolated or concomitant (n=9) setting were included between Jan 2009 to Jan 2020. A retrospective analysis of prospectively collected data was undertaken over 10 years. All case notes were reviewed (operation notes and follow up correspondence). Serial follow up echocardiography was reviewed to assess prosthesis function for structural valve deterioration. Echocardiography data was correlated with patient’s clinical status during the follow up period. Mortality data was checked with national registries. Results: In-hospital mortality was 5.7% (n=4). Of the 66 patients, there were 6 deaths during follow up. Surviving patients were followed for a median period of 2 years (IQR 1-3 years). No patients underwent re-intervention for structural valve deterioration. At follow up, 90% patients’ symptoms were consistent with NYHA class I-II and were successfully discharged to their primary care physician. Conclusions: Our experience with the Freestyle valve shows this to be a feasible bioprosthetic valve with good early and late outcomes. It is a versatile option both in the subcoronary position or as a complete aortic root replacement with low morbidity. Our experience has shown that the Freestyle valve is a preferable option in the setting of infective endocarditis with tissue destruction. Long-term follow-up has shown no structural valve deterioration in our experience, with good clinical outcomes. Freestyle valve used as aortic root versus subcoronary position Valve Position Root Replacement Subcoronary 35 35 Redo 18 16 Infective Endocarditis 12 19 Death (follow up) 3 3 Mean Bypass (Cross clamp) time/min 269 (185) 240 (156) Mean haemodynamic data MG- mmHg/PG-mmHg/AVA-cm2 6.6/12.5/1.6 6.0/8.0/0.7 Aortic regurgitation at follow up 0 0

Failure analysis of screw shaft in screw compressor

This paper analyses the root causes of screw shaft failure in screw compressors. The failure mechanism was studied by visual inspection, macro- and microfractography, chemical characterization, and mechanical property analysis. The results reveal that the main reason for the failure was multisource fatigue due to the lack of surface quenching at the fracture position of the shaft root. To prevent similar failures, better control of surface quenching is strongly recommended.

Variation in the articulation of Russian stressed vowels and the mechanics of palatalization in consonants

A 3D/4D ultrasound study of Russian stressed vowels in the context of ‘soft’ (phonetically palatalized or palatal) versus ‘hard’ consonants reveals that vowels in these two contexts differ systematically in terms of the position of the tongue root while the tongue dorsum is less consistently modified depending on the speaker, vowel or consonant context. This paper proposes that the observed vowel allophony, as well as the softness contrast in Russian consonants, and the contrast between front and central high vowels, are all defined in terms of the feature [ATR].

Volumetric cone-beam computed tomography evaluation and risk factor analysis of external apical root resorption with clear aligner therapy.

To investigate the prevalence and severity of external apical root resorption (EARR) volumetrically with clear aligner therapy using cone-beam computed tomography (CBCT) as well as determine the possible risk factors and develop a prediction model for EARR. In this retrospective study, 320 incisors from 40 Class II patients treated with aligners (Invisalign) were included in this study. CBCT images were obtained at pretreatment (T0) and posttreatment (T1). Root volume was calculated by three-dimensional reconstruction of CBCT images, and apical tooth movement was measured from superimposed CBCT images. Changes in root volume were compared using paired t-tests, and the relationship between root volume loss and potential risk factors was analyzed by multiple linear regression. All of the measured incisors showed root volume loss, with an average of 11.48 ± 6.70 mm3, and the prevalence of severe resorption was 0.625%. The prediction model for EARR included variables of posttreatment sagittal root position (SRP), extraction, tooth type, and apical intrusion and extrusion displacements, with an R2 of 0.51. Age, sex, duration, pretreatment SRP, attachment, advancement, and retraction movements were excluded from the model. Most incisors showed mild to moderate resorption during aligner treatment; only a minimal percentage showed severe resorption. Posttreatment SRP (which showed the highest association with EARR), extraction, tooth type, and apical intrusion and extrusion displacements were risk factors for EARR.

Study of double-chamber air arc plasma torch and the application in solid-waste disposal

Arc plasma can be applied in hazardous solid waste disposal for higher temperature than common heating methods, but some practical issues exist in practical engineering application. In this study, an air arc plasma torch with double chambers and magnetic controlling is designed to realize wide variable power and long electrode life. The detailed characteristics and laws of the air arc are studied. The condition parameters of arc current (I), air flow rate (G) and the structure parameters of inlet area ratios and electrode diameters influence both the arc voltage and arc root positions. The arc rotating driven by magnetic field effectively lengthens the electrode life. The gasification process and product of organic wastes by air plasma are influenced largely by the waste compositions and the air flow rate. A furnace structure with more even atmosphere and longer residence time should be considered for better gasification. Oxygen-deficient environment is important to suppress NO x formation during the application of air plasma. Inorganic solid wastes can be melt by the air plasma and cooled down to form compact vitreous structures in which heavy metals can be locked and the leaching rates significantly decrease down.