Biomechanical behavior of three maxillary expanders in cleft lip and palate: a finite element study.

This study evaluated the stress distribution in the dentoalveolar and palatal bone structures during maxillary expansion in a 17-year-old male patient with bilateral cleft lip and palate (BCLP) using expanders with dental (HYRAX) and skeletal anchorage (MARPE). For the generation of the specific finite element models, cone-beam computed tomography was used, and the DICOM files were exported to Mimics 3-Matic (Materialise) and Patran (MSC Software) software. Three specific three-dimensional models were generated: A) HYRAX: conventional four-banded hyrax screw (9 mm); B) MARPE-DS: 3 miniscrews (1.8 mm diameter - 5.4 mm length) and four-banded dental anchorage; and C) MARPE-NoDS: 3 miniscrews without dental anchorage. Maxillary expansion was simulated by activating the expanders transversely 1 mm on the "X" axis. HYRAX resulted in higher levels of deformation predominantly in the dentoalveolar region. MARPE-DS showed stress in the dentoalveolar region and mainly in the center of the palatal region, at approximately 4,000 µÎµ. MARPE-NoDS exhibited evident stress only in the palatal region. High stress levels in the root anchoring teeth were observed for HYRAX and MARPE-DS. In contrast, MARPE-NoDS cause stress on the tooth structure. The stress distribution from the expanders used in the BLCP showed asymmetric expansive behavior. During the initial activation phase of expansion, the HYRAX and MARPE-DS models produced similarly high strain at the dentoalveolar structures and upper posterior teeth displacement. The MARPE-NoDS model showed restricted strain on the palate.

Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe-Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi-Valent Catalysts.

The precise and reversible detection of hydrogen sulfide (H2 S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self-assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2 S (≈0.1 ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2 S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe-doped CuO hollow spheres as H2 S gas-sensing materials via spray pyrolysis. 4 at.% of Fe-doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1 ppm) and reversible sensing characteristics (100% recovery) to 0.1 ppm of H2 S under high humidity (relative humidity 80%) at 175 °C. The effect of multi-valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti- or Nb ions into CuO sensors. Mechanistic details of these excellent H2 S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe-doped CuO sensing materials. The selective and reversible detection of H2 S using the Fe-doped CuO sensor suggested in this work opens a new possibility for halitosis self-monitoring.

Relapse and failure rates between CAD/CAM and conventional fixed retainers: a 2-year follow-up of a randomized controlled clinical trial.

BACKGROUND: Retention has been always considered a major challenge in orthodontics. Recently computer-aided design/computer-aided manufacturing (CAD/CAM) fixed retainers (FRs) have been introduced as a marked development in retainer technology, offering potential advantages. OBJECTIVE: The objective of this study was to compare the differences in relapse and failure rates in patients treated with FRs using CAD/CAM technology, lab-based technique, and chairside method. TRIAL DESIGN: A double-blinded, prospective, randomized controlled clinical trial was conducted over a 2-year period at a single centre. INTERVENTIONS: These patients were divided into three groups: CAD/CAM group with multistranded Stainless Steel wires (CAD/CAM, n = 14), lab group with the same multistranded wires (lab, n = 15), and a chairside group with Stainless Steel Ortho-FlexTech wires (chairside, n = 14). OUTCOMES: Inter-canine width (ICW) and Little's irregularity index were digitally measured from scans at the orthodontic debonding (T1), 6-month retention (T2), 1-year retention (T3), and 2-year retention (T4) visits. All forms of failure were documented and analyzed. RANDOMIZATION: Participants were randomly assigned to the three groups using online randomization software (randomization.com) by a statistician who was not involved in the study. BLINDING: Patients were blinded in terms of the FR group to which they were each randomly assigned. The principal investigator was blinded upon data analysis since patients' records were coded to minimize observer and measurement bias. RESULTS: Initially 81 patients were assessed for eligibility. Seventy-five patients were randomly allocated into the three study groups. After 2-year follow-up, 43 patients came back for the follow-up and were analyzed. The CAD/CAM group showed significantly less reduction in ICW compared to the chairside group at all time intervals (P < .05) and compared to the lab group at 6 months (P = .038). In terms of LII, the CAD/CAM group exhibited significantly less change than the chairside and lab groups at all time intervals (P < .05). The CAD/CAM group had the lowest failure rate (21.4%), followed by chairside group (28.6%) and then lab group (33.3%), however the differences were insignificant. No harms were observed in the current study. CONCLUSION: Within 2 years of fixed retention, CAD/CAM FRs showed significantly less relapse than lab-based and chairside FRs. However, there was no significant difference in failure rates among the groups. TRIAL REGISTRATION: NCT05915273.

Synergistic Integration of Machine Learning with Microstructure/Composition-Designed SnO2 and WO3 Breath Sensors.

A high-performance semiconductor metal oxide gas sensing strategy is proposed for efficient sensor-based disease prediction by integrating a machine learning methodology with complementary sensor arrays composed of SnO2- and WO3-based sensors. The six sensors, including SnO2- and WO3-based sensors and neural network algorithms, were used to measure gas mixtures. The six constituent sensors were subjected to acetone and hydrogen environments to monitor the effect of diet and/or irritable bowel syndrome (IBS) under the interference of ethanol. The SnO2- and WO3-based sensors suffer from poor discrimination ability if sensors (a single sensor or multiple sensors) within the same group (SnO2- or WO3-based) are separately applied, even when deep learning is applied to enhance the sensing operation. However, hybrid integration is proven to be effective in discerning acetone from hydrogen even in a two-sensor configuration through the synergistic contribution of supervised learning, i.e., neural network approaches involving deep neural networks (DNNs) and convolutional neural networks (CNNs). DNN-based numeric data and CNN-based image data can be exploited for discriminating acetone and hydrogen, with the aim of predicting the status of an exercise-driven diet and IBS. The ramifications of the proposed hybrid sensor combinations and machine learning for the high-performance breath sensor domain are discussed.

Biomechanical analysis for different mandibular total distalization methods with clear aligners: A finite element study.

Objective: : The purpose of this finite element method (FEM) study was to analyze the biomechanical differences and tooth displacement patterns according to the traction direction, methods, and sites for total distalization of the mandibular dentition using clear aligner treatment (CAT). Methods: : A finite element analysis was performed on four FEM models using different traction methods (via a precision cut hook or button) and traction sites (mandibular canine or first premolar). A distalization force of 1.5 N was applied to the traction site by changing the direction from -30 to +30° to the occlusal plane. The initial tooth displacement and von Mises stress on the clear aligners were analyzed. Results: : All CAT-based total distalization groups showed an overall trend of clockwise or counterclockwise rotation of the occlusal plane as the force direction varied. Mesiodistal tipping of individual teeth was more prominent than that of bodily movements. The initial displacement pattern of the mandibular teeth was more predominant based on the traction site than on the traction method. The elastic deformation of clear aligners is attributed to unintentional lingual tipping or extrusion of the mandibular anterior teeth. Conclusions: : The initial tooth displacement can vary according to different distalization strategies for CAT-based total distalization. Discreet application and biomechanical understanding of traction sites and directions are necessary for appropriate mandibular total distalization.

Evaluation of maxillary canine and molar movement during the first phase of extraction space closure: a multilevel analysis.

OBJECTIVE: This study was designed to analyze and compare the cusp and apex movements of the maxillary canines and first molars during canine retraction in the first step of extraction space closure, and to evaluate if these teeth follow a curvilinear (acceleration and/or deceleration) movement rate. MATERIAL AND METHODS: Twenty-five patients (23.3 ± 5.1 years of age) were enrolled. The retraction of the maxillary canines was accomplished using nickel-titanium closed coil springs (100gf) on 0.020-in stainless steel archwire. Oblique cephalograms were traced and superimposed on the anatomic best fit of the maxilla (before the retraction [T0], and after one month [T1], three [T3], five [T5] and seven [T7] months). Statistics was based in a normally distributed data. Multilevel procedures were used to derive polynomials for each of the measurements. Student's t-test and one-way repeated measures ANOVA were conducted. The level of significance of 5% was adopted. RESULTS: Canine cusps and apexes did not follow a quadratic curve regarding horizontal movement (neither accelerate nor decelerate). Canine and molar cusps showed more horizontal movement than apexes (4.80 mm vs. 2.78 mm, and 2.64 mm vs. 2.17 mm, respectively). CONCLUSIONS: Canine did not accelerate or decelerate overtime horizontally; the cusps and apexes of the canines and molars showed more horizontal movement and larger rate at the beginning of canine retraction, followed by significantly smaller and constant movement rate after the first month.

Erratum: Correction of Affiliations in the Article "Establishment of a Nationwide Korean Imaging Cohort of Coronavirus Disease 2019".

This corrects the article on p. e413 in vol. 35, PMID: 33258333.

Correction: Deep Learning With Chest Radiographs for Making Prognoses in Patients With COVID-19: Retrospective Cohort Study.

[This corrects the article DOI: 10.2196/42717.].

Forces and moments generated by 3D direct printed clear aligners of varying labial and lingual thicknesses during lingual movement of maxillary central incisor: an in vitro study.

OBJECTIVE: The objective of this study was to measure the forces and moments exerted by direct printed aligners (DPAs) with varying facial and lingual aligner surface thicknesses, in all three planes of space, during lingual movement of a maxillary central incisor. MATERIALS AND METHODS: An in vitro experimental setup was used to quantify forces and moments experienced by a programmed tooth to be moved and by adjacent anchor teeth, during lingual movement of a maxillary central incisor. DPAs were directly 3D-printed with Tera Harz TC-85 (Graphy Inc., Seoul, South Korea) clear photocurable resin in 100-µm layers. Three multi-axis sensors were used to measure the moments and forces generated by 0.50 mm thick DPAs modified with labial and lingual surface thicknesses of 1.00 mm in selective locations. The sensors were connected to three maxillary incisors (the upper left central, the upper right central, and the upper left lateral incisors) during 0.50 mm of programmed lingual bodily movement of the upper left central incisor. Moment-to-force ratios were calculated for all three incisors. Aligners were benchtop tested in a temperature-controlled chamber at intra-oral temperature to simulate intra-oral conditions. RESULTS: The results showed that increased facial thickness of DPAs slightly reduced force levels on the upper left central incisor compared to DPAs of uniform thickness of 0.50 mm. Additionally, increasing the lingual thickness of adjacent teeth reduced force and moment side effects on the adjacent teeth. DPAs can produce moment-to-force ratios indicative of controlled tipping. CONCLUSIONS: Targeted increases in thickness of direct 3D-printed aligners change the magnitude of forces and moments generated, albeit in complex patterns that are difficult to predict. The ability to vary labiolingual thicknesses of DPAs is promising to optimize the prescribed orthodontic movements while minimizing unwanted tooth movements, thereby increasing the predictability of tooth movements.

Forces and moments generated during extrusion of a maxillary central incisor with clear aligners: an in vitro study.

OBJECTIVE: To assess the possibility of extrusion of a maxillary central incisor with the use of buccal and lingual pressure columns in the absence of attachments, and to evaluate the forces and moments experienced by the teeth using both thermoformed and 3D-printed clear aligners. MATERIALS AND METHODS: A three-axis force and moment sensor (Aidin Robotics, Anyang, South Korea) was used to measure the forces and moments during extrusion of an upper left central incisor (UL1) and any forces experienced by the upper right central incisor (UR1) using thermoformed aligners and 3D-printed aligners. For the thermoformed aligners, the materials used were ATMOS® (American Orthodontics, Sheboygan, WI) and Zendura FLX® (Bay Materials LLC, Fremont, CA). 3D-printed aligners were fabricated using TC-85 clear photocurable resin (Graphy Inc., Seoul, South Korea). For each material type, three conditions were tested: Group 1: No attachment or pressure columns (control); Group 2: Attachment only; and Group 3: Pressure columns only. Each group was planned for 0.5 mm of extrusion on the UL1. RESULTS: All force readings collected demonstrated statistically significant differences when compared by materials and when compared by groups, with a P value of < 0.001. In the absence of attachment or pressure columns (Group 1), ATMOS® and TC-85 groups exerted extrusive force on the UL1. However, significantly lower forces and moments were exerted by the TC-85 group in comparison to the ATMOS® and Zendura FLX® groups. In the presence of attachment (Group 2), all three ATMOS®, Zendura FLX® and TC-85 groups exerted extrusive force on the UL1, with the TA group showing different directions of faciolingual force, mesiodistal force and faciolingual inclination on the UR1 when compared to the other two thermoformed groups. Whereas in the presence of pressure columns (Group 3), only the TC-85 3D-printed aligner group exerted extrusive force. Thermoformed aligners generated significantly higher mean forces and moments than 3D-printed aligners. Significant levels of unintended forces and moments were present in all groups. CONCLUSIONS: Force levels generated during extrusion with clear aligners are significantly lower with those 3D-printed using TC-85 than with those thermoformed using ATMOS® or Zendura FLX®. Attachments consistently generated extrusive forces, and may be an effective adjunct in achieving extrusion of incisors. Extrusion may be achieved without the use of attachments by utilizing pressure columns in 3D-printed aligners using TC-85. While different strategies can generate extrusive forces, there are significant unintended forces and moments.

Comparison of translucency, thickness, and gap width of thermoformed and 3D-printed clear aligners using micro-CT and spectrophotometer.

The present study compared the thickness and gap width of thermoformed and 3D-printed clear aligners (CAs) using micro-computed tomography (micro-CT) and evaluated their translucency using spectrophotometer. Four groups of CAs were tested: thermoformed with polyethylene terephthalate glycol (TS) or copolyester-elastomer combination (TM), and 3D-printed TC-85 cleaned with alcohol (PA) or with centrifuge (PC). CIELab coordinates were measured (n = 10) to evaluate translucency. CAs (n = 10) were fitted onto respective models and micro-CT was performed to evaluate the thickness and gap width. Thickness and gap width were measured for different tooth type and location in sagittal sections on all sides. The PC group showed significantly higher translucency than the PA group, which was similar to the TS and TM groups (p < 0.01). After the manufacturing process, thickness reduction was observed in the thermoformed groups, whereas thickness increase was observed in the 3D printed-groups. The TM group showed the least gap width amongst the groups (p < 0.01). Thermoformed and 3D-printed CAs had significantly varied thicknesses and regions of best fit depending on the tooth type and location. Differences in the translucency and thickness of the 3D-printed CAs were observed depending on the cleaning methods.

Anatomical proposal of local anesthesia injection for median nerve block in treating hyperhidrosis with botulinum neurotoxin.

INTRODUCTION: Hyperhidrosis, causing excessive sweat, can be treated with Botulinum neurotoxin injection. Botulinum toxin, an effective and safe treatment for hyperhidrosis, unfortunately involves significant pain due to multiple injections. This study aims to propose a more efficient and less painful approach to nerve blocks for relief, by identifying optimal injection points to block the median nerve, thereby enhancing palmar hyperhidrosis treatment. METHODS: This study, involving 52 Korean cadaver arms (mean age 73.5 years), measured the location of the median nerve relative to the transverse line at the pisiform level to establish better nerve block injection sites. RESULTS: In between the extensor carpi radialis and palmaris longus, the median nerve was located at an average distance of 47.39 ± 6.43 mm and 29.39 ± 6.43 mm from the transverse line at the pisiform level. DISCUSSION: To minimize discomfort preceding the botulinum neurotoxin injection, we recommend the optimal injection site for local anesthesia to be located 4 cm distal to the transverse line of the pisiform, within the tendons of the palmaris longus and flexor carpi radialis muscles.

Deep Learning With Chest Radiographs for Making Prognoses in Patients With COVID-19: Retrospective Cohort Study.

BACKGROUND: An artificial intelligence (AI) model using chest radiography (CXR) may provide good performance in making prognoses for COVID-19. OBJECTIVE: We aimed to develop and validate a prediction model using CXR based on an AI model and clinical variables to predict clinical outcomes in patients with COVID-19. METHODS: This retrospective longitudinal study included patients hospitalized for COVID-19 at multiple COVID-19 medical centers between February 2020 and October 2020. Patients at Boramae Medical Center were randomly classified into training, validation, and internal testing sets (at a ratio of 8:1:1, respectively). An AI model using initial CXR images as input, a logistic regression model using clinical information, and a combined model using the output of the AI model (as CXR score) and clinical information were developed and trained to predict hospital length of stay (LOS) ≤2 weeks, need for oxygen supplementation, and acute respiratory distress syndrome (ARDS). The models were externally validated in the Korean Imaging Cohort of COVID-19 data set for discrimination and calibration. RESULTS: The AI model using CXR and the logistic regression model using clinical variables were suboptimal to predict hospital LOS ≤2 weeks or the need for oxygen supplementation but performed acceptably in the prediction of ARDS (AI model area under the curve [AUC] 0.782, 95% CI 0.720-0.845; logistic regression model AUC 0.878, 95% CI 0.838-0.919). The combined model performed better in predicting the need for oxygen supplementation (AUC 0.704, 95% CI 0.646-0.762) and ARDS (AUC 0.890, 95% CI 0.853-0.928) compared to the CXR score alone. Both the AI and combined models showed good calibration for predicting ARDS (P=.079 and P=.859). CONCLUSIONS: The combined prediction model, comprising the CXR score and clinical information, was externally validated as having acceptable performance in predicting severe illness and excellent performance in predicting ARDS in patients with COVID-19.

The effect of maxillary first and mandibular second premolar extractions on the posterior Bolton ratio.

INTRODUCTION: The anterior and overall Bolton ratios and their application in orthodontics are widely known. However, little has been reported about the posterior Bolton ratio, how it is affected by the extraction of posterior teeth, and its application in orthodontic treatment planning. This study aimed to investigate how extracting maxillary first and mandibular second premolars affects the posterior Bolton ratio. METHODS: The sample included 55 patients with Class I occlusion within 1 standard deviation of ideal anterior and overall Bolton ratios. The digitized models were subjected to virtual extraction of maxillary first premolars and mandibular second premolars and setup of posterior teeth in ideal occlusion. If space closure compromised occlusion, the teeth were moved to achieve ideal cusp-fossa or cusp-marginal ridge occlusion. The ideal setups were measured for residual interproximal spacing. Statistical analysis used R statistical software (version 2018; R Core Team, Vienna, Austria). RESULTS: The ideal nonextraction posterior Bolton ratio was determined from the sample to be 105.77 ± 1.99%. The ideal expected posterior Bolton ratio for maxillary first and mandibular second premolar extraction patients was 106.52 ± 2.52%. This significantly differed from the expected posterior Bolton ratio for the 4 first premolar extractions. Patients finished with an average of 1.28 mm net residual spacing between mandibular first premolars and first molars; 38.2% of patients finished with at least 1.5 mm of residual space, and 9.1% of patients finished with at least 2 mm of residual space. CONCLUSIONS: A patient with ideal anterior, posterior, and overall Bolton ratios treated with maxillary first and mandibular second premolar extractions to ideal occlusion will likely finish with some spacing in the mandibular dentition.

DLX6 and MSX1 from saliva samples as potential predictors of mandibular size: A cross-sectional study.

INTRODUCTION: Morphologic features of the mandible are influenced by the genes of each individual. Mandible size is important to orthodontists because the mandible is the mechanism by which the lower face influences facial esthetics and dental function. To date, no biological marker has been identified that indicates eventual mandible size. This study aimed to correlate the expression of DLX5, DLX6, EDN1, HAND2, PRRX1, and MSX1 to mandible size. METHODS: Fifty-nine orthodontic patients aged >6 years who had available cephalometric radiographs were studied. Patients were classified on the basis of condylion-to-gnathion measurements. Messenger RNA was isolated from saliva and subjected to real-time quantitative polymerase chain reaction. RESULTS: Threshold cycle values for subjects with small mandibles (>1 standard deviation [SD] from the mean) had the least expression of DLX6 and MSX1. Threshold cycle values for subjects with large mandibles (>1 SD) had less expression of DLX6 and MSX1 than subjects within 1 SD but more than those with small mandibles. CONCLUSIONS: DLX6 and MSX1 are related to mandible development and size. This finding could be used to improve treatment planning for medical and dental professionals seeking to understand the impact of genetics on bone growth.

Evaluation of maxillary canine and molar movement during the first phase of extraction space closure: a multilevel analysis

ABSTRACT Objective: This study was designed to analyze and compare the cusp and apex movements of the maxillary canines and first molars during canine retraction in the first step of extraction space closure, and to evaluate if these teeth follow a curvilinear (acceleration and/or deceleration) movement rate. Material and Methods: Twenty-five patients (23.3 ± 5.1 years of age) were enrolled. The retraction of the maxillary canines was accomplished using nickel-titanium closed coil springs (100gf) on 0.020-in stainless steel archwire. Oblique cephalograms were traced and superimposed on the anatomic best fit of the maxilla (before the retraction [T0], and after one month [T1], three [T3], five [T5] and seven [T7] months). Statistics was based in a normally distributed data. Multilevel procedures were used to derive polynomials for each of the measurements. Student's t-test and one-way repeated measures ANOVA were conducted. The level of significance of 5% was adopted. Results: Canine cusps and apexes did not follow a quadratic curve regarding horizontal movement (neither accelerate nor decelerate). Canine and molar cusps showed more horizontal movement than apexes (4.80 mm vs. 2.78 mm, and 2.64 mm vs. 2.17 mm, respectively). Conclusions: Canine did not accelerate or decelerate overtime horizontally; the cusps and apexes of the canines and molars showed more horizontal movement and larger rate at the beginning of canine retraction, followed by significantly smaller and constant movement rate after the first month.

RESUMO Objetivo: O objetivo deste estudo foi analisar a movimentação das cúspides e dos ápices de caninos e primeiros molares superiores durante a retração de caninos na primeira fase do fechamento do espaço pós-extração, e avaliar se esses dentes apresentam mudança na taxa de movimentação (aceleração e/ou desaceleração). Material e Métodos: Vinte e cinco pacientes (idade = 23,3 ± 5,1 anos) foram incluídos. A retração dos caninos superiores foi realizada com molas helicoidais fechadas de níquel-titânio (100gf) em arco 0,020" de aço inoxidável. Foram feitos traçados cefalométricos de telerradiografias oblíquas e sobrepostos ao melhor ajuste anatômico da maxila (antes da retração [T0]; após um mês [T1], três meses [T3], cinco meses [T5] e sete meses [T7]). A estatística foi baseada em dados com distribuição normal. Procedimentos multiníveis foram usados para derivar polinômios para cada uma das medidas. Teste t de Student e ANOVA de uma via para medidas repetidas foram realizados, adotando-se um nível de significância de 5%. Resultados: As cúspides e os ápices dos caninos não seguiram uma curva quadrática em relação ao movimento horizontal (sem aceleração ou desaceleração). As cúspides dos caninos e molares apresentaram mais movimento horizontal do que os ápices (4,80 mm vs. 2,78 mm e 2,64 mm vs. 2,17mm, respectivamente). Conclusões: A movimentação horizontal dos caninos não acelerou ou desacelerou ao longo do tempo; as cúspides e os ápices dos caninos e molares apresentaram maior movimento horizontal e maior taxa de movimentação no início da retração dos caninos, seguida por uma taxa de movimentação significativamente menor e constante após o primeiro mês.

Force profile assessment of direct-printed aligners versus thermoformed aligners and the effects of non-engaged surface patterns.

BACKGROUND: The purpose of the study was to measure the forces delivered by direct-printed aligners (DPA) in the vertical dimension and compare the force profile with traditional thermoformed aligners (TFA) and to investigate the impact of non-engaged surface patterns to the properties of DPA and TFA. METHODS: A force-measuring appliance was fabricated capable of displacing the aligner in 0.10 mm increments and measuring the resultant force. Polyethylene terephthalate glycol (ATMOS 0.030″ American Orthodontics) and TC-85DAC resin (Graphy Inc) were used to create TFA and DPA, respectively. Aligners were temperature-controlled prior to and during testing to simulate the oral environment. The resultant forces from displacements ranging from 0.10 to 0.30 mm were measured. RESULTS: At intraoral temperatures, DPA demonstrated significantly less force than TFA. TFA demonstrated a substantial statistically significant increase in force with each 0.10 mm increase in vertical displacement. DPA demonstrated a much more consistent force profile across the range of displacements. The effects of surface patterns in both DPA and TFA were generally a decrease in force. Statistical significance of surface patterns was detected for TFA at displacements of 0.30 mm and greater and significant for DPA only at a displacement of 0.10 mm. Surface patterns in both DPA and the TFA did not show any statistical difference when assessing force proprieties. CONCLUSIONS: Forces delivered by aligners in the vertical dimension by DPA are more consistent and of lower magnitude than those of TFA aligners. Surface patterns were not capable of altering the force properties of both DPA and TFA.

Cephalometric and model evaluations after molar distalization using modified C-palatal plates in patients with severe arch length discrepancy.

INTRODUCTION: This study aimed to evaluate the dentoskeletal and soft-tissue changes after molar distalization using modified C-palatal plates in patients with severe maxillomandibular arch length discrepancies. METHODS: Twenty-four patients with Class I and II malocclusion (19.0 ± 7.3 years; 17 females and 8 males), who had severe maxillary crowding of >10 mm, and moderate mandibular crowding of >6 mm, underwent molar distalization using modified C-palatal plates and buccal miniscrews with approximately 300 g of force per side. Models were made, and cephalograms were taken before and after treatment. Cephalometric variables and arch dimensions were measured. Paired t test and Wilcoxon rank sum test were used for statistical analysis. RESULTS: In the maxillary dentition, an average of 12.4 mm of crowding was resolved by molar distalization of 4.4 mm, interproximal stripping of 0.7 mm, and arch expansion. In the mandibular dentition, crowding of 6.7 mm was alleviated by molar distalization of 2.4 mm, an interproximal of 1.5 mm, and additional arch expansion. The incisor positions were maintained (SN-U1, 101.3°; IMPA, 88.8°), and soft-tissue profiles were improved (LL/E-line -1.1 mm; P < 0.001) after treatment. CONCLUSIONS: Maxillary and mandibular tooth-size arch length discrepancy of 12.4 mm and 6.7 mm, respectively, were resolved by molar distalization, interproximal reduction, and arch expansion, whereas incisor positions were maintained, and soft-tissue profiles were improved. This could be a viable treatment option in patients with moderate-to-severe crowding.