Esthetic orthodontic aligners are removable polymer-based devices fabricated via thermoforming (TM) or direct three-dimensional printing (DTP). However, a gap remains in the literature regarding how these two manufacturing methods differ in their mechanical and physical properties. This systematic review aimed to assess and compare changes in the physical and mechanical properties of orthodontic aligners fabricated by TM or DTP methods. However, it should be noted that the included evidence does not allow a clear separation between manufacturing method and material system, as TM and DTP aligners were based on fundamentally different polymer. A systematic search was conducted in six electronic databases in May 2025. Selection criteria: In vitro studies comparing these properties between TM and DTP aligners were included. Data collection and analysis: Two reviewers independently selected studies, extracted data, and performed risk-of-bias assessments and meta-analyses. Twenty-three studies were selected, and four were included in the meta-analysis. TM and DTP aligners exhibited distinct mechanical patterns. TM aligners generally showed higher flexural strength, storage modulus stability, and surface microhardness, reflecting greater initial rigidity. In contrast, DTP aligners demonstrated higher shape recovery potential, greater traction forces in vertical tests, and improved geometric accuracy under laboratory conditions. Regarding physical characteristics, TM aligners exhibited an average thickness reduction of -39.76% after fabrication, color change, and lower ultraviolet stability; while geometric accuracy tended to favor DTP aligners with a thickness increase of +11.02%, and better marginal adaptation. DTP aligners also exhibited a lower glass transition temperature (Tg = 42.3°C), suggesting differences in thermomechanical response. The meta-analysis showed that surface roughness assessments revealed higher Sa (mean surface amplitude) values in DTP aligners, whereas TM aligners exhibited greater Sv (valley depth). Following clinical use, DTP aligners maintained higher Sz (total amplitude) values, while TM aligners demonstrated reduced Sa values. There was no statistically significant difference in thickness variation between the two fabrication methods (standardized mean difference = 1.48; 95% confidence interval: -7.26-4.30; P = .62), with high heterogeneity (I2 = 97%). TM and DTP aligners show distinct physical and mechanical behaviors influenced by manufacturing and material characteristics. As current evidence is limited to in vitro studies, further clinical research is needed to confirm these findings and their relevance in patient care. Therefore, any clinical extrapolation should be taken with caution and interpreted within the limitations of the current evidence based on in vitro research. https://doi.org/10.17605/OSF.IO/BT98F.

Obstructive sleep apnea (OSA) is characterized by recurrent collapses of the upper airway during sleep. Although nasal obstruction has been identified as an independent risk factor for OSA and extensively studied, the relationship between nasal anatomical structures and OSA remains poorly understood. The objective of this study was to determine the relationship between the nasal cross-sectional area (CSA), as measured by magnetic resonance imaging in the supine position, and the presence of OSA, as well as to investigate its correlation with OSA severity. In this cross-sectional study, a total of 111 participants were enrolled, comprising 88 patients with OSA and 23 healthy controls. All participants underwent polysomnography to determine their apnea-hypopnea index (AHI). Subsequently, MRI scans were performed in the supine position to measure CSA at distances of 1.5, 2, 2.5, 3, 4, 5, and 6 cm posterior to the most anterior point of the nasal cavity. Participants were stratified into groups based on AHI severity, and statistical analyses were conducted to determine the correlation between CSA measurements and the AHI. Significant intergroup differences were observed in the minimum CSA at the 2.5 and 4.0 cm levels. No difference was found in the sum of nasal CSA at any level. Furthermore, no group differences were found in either nasal cavity volume or surface area. A comparison between healthy individuals and OSA patients revealed that advanced age, a higher body mass index, male sex, and a reduced total minimum nasal cross-sectional area (TMCA) were independent and significant predictors of OSA. TMCA was identified as a predisposing factor for OSA, but it was not found to be associated with the severity of the condition. Furthermore, long-term, severe OSA may contribute to an enlargement of the CSA.

Quantification of the effect of orthodontic treatment on the gingival mircroaesthetics is lacking. The aim of this exploratory investigation was to investigate the effect of fixed orthodontic appliance therapy on gingival aesthetics associated with the anterior maxillary dentition. A bespoke gingival aesthetic criterion was used to assess 150 sets of pre- and post-treatment intra-oral photographs from a consecutively treated patient sample who had completed fixed appliance therapy. Five assessors rated the images assigning a score per criterion. Reliability of the method was assessed with concordance correlation coefficient (CCC) and Bland-Altman limits of agreement (LOA). Differences by timepoint, assessors, and treatment characteristics were assessed with statistical tests or generalized linear models at α = 5%. In the sample of 150 cases, the most common pre-treatment incisor classification was Class III (n = 57) followed by Class II Div 1 (n = 52). The majority of cases were treated on a nonextraction basis (n = 95) and involved orthodontic appliances only (n = 134). The CCC and LOA values for the aesthetic gingival criterion ranged from good-excellent. Average aesthetic summary scores differed from before pre-treatment [median = 33.9; interquartile range (IQR) = 24.5-45.2] and post-treatment (median = 75.8; IQR = 65.2-85.3) to a significant degree (mean difference = 38.5; standard deviation = 17.8; P < 0.001). No difference in aesthetic criterion points score was evident for treatment plan (nonextraction vs extraction) (P = 1.00) and treatment type (orthodontic only or orthognathic) (P = 0.52). Considerable variation in summary scores among assessors with different specialty/grades was seen (P < 0.001). Gingival aesthetic ratings were undertaken in isolation without the assessment of specific contributions made by soft and hard tissues, and changes in tooth position. Orthodontic treatment with fixed appliances can have a positive effect on the gingival margin, gingival zenith, gingival embrasure, connector area, and overall rating of gingival symmetry of the anterior maxillary teeth. However, aesthetic ratings depend on the assessor.

Panoramic X-rays (OPGs) play a crucial role in both pre- and post-treatment orthodontic evaluation. Binary segmentation of tooth versus background regions in these images is fundamental for dental image analysis, enabling automated diagnosis and improving treatment planning in orthodontics and general dentistry. Although various deep learning approaches have been investigated, standardized performance benchmarks on publicly available datasets remain limited. This study aims to establish a benchmark for binary semantic segmentation of tooth versus background regions as a basis for orthodontic applications by applying an attention-gated U-Net (Att-U-Net) architecture to a large, publicly accessible dataset. An Att-U-Net model was used to perform tooth versus background binary segmentation on the 'Teeth Segmentation on Dental X-ray Images' dataset, which includes 598 annotated OPGs. The dataset was divided into training (70%), validation (10%), and testing (20%) sets using stratified sampling to maintain a representative class distribution. The model was trained with a combined loss function that merges binary cross-entropy and dice loss to address class imbalance. Its performance was assessed using a comprehensive set of metrics, including the dice coefficient, mean IoU, precision, recall, and receiver operating characteristic AUC in the entire dataset, quintiles based on the tooth-to-background pixel ratio, and a subset of radiographs that can present challenges during artificial intelligence-based tooth segmentation. Finally, evaluations of the model's consistency and computational performance, as well as visual inspections, were conducted. The Att-U-Net model demonstrated strong and accurate performance. Training and validation curves indicated stable convergence, with the model reaching a final dice coefficient of 0.911, a mean IoU of 0.838, and a pixel accuracy of 0.974 on the held-out test set. The model's sensitivity increased, and its overall performance saw a slight improvement in challenging segmentation cases. The inference times indicated that the model was both fast and highly stable. Visual inspection confirmed the high quantitative scores. The Att-U-Net model demonstrated robust and reliable performance, with the training process being stable and consistent. The high quantitative performance was complemented by qualitative analysis, which showed that the model produces precise and visually accurate segmentation masks, even in cases that pose challenges. This can be useful for OPG quality reviews and lays the groundwork for tackling more complex segmentation tasks and enhancing automated diagnosis systems in orthodontics.

Interproximal enamel reduction (IER) is a common orthodontic procedure used to correct tooth-size discrepancies, create space, and reduce black triangles. Although several studies have examined the effects of IER on enamel roughness, caries risk, and periodontal health, none have investigated patient-reported pain associated with different IER techniques. As pain is a key patient-reported outcome, understanding how it varies between manual and motor-driven techniques can help clinicians improve patient comfort, refine treatment planning, and enhance informed consent discussions. The primary objective was to compare pain experienced during IER using manual abrasive strips versus motor-driven abrasive strips in patients undergoing orthodontic treatment at Royal Surrey County Hospital NHS Foundation Trust. There is no significant difference in patient-reported pain between manual and motor-driven IER methods in the lower labial segment. This prospective, randomised, crossover clinical trial used visual analogue scale (VAS) questionnaires to measure pain. In accordance with a power calculation based on detecting a 10 mm difference in VAS scores as statistically significant, a total of 68 subjects were required. A total of 34 participants (due to the crossover design) aged 16 years or older were recruited. Participants were randomly assigned via concealed allocation into two groups. Group A underwent manual IER first, followed by motor-driven IER after a 6-week washout period; Group B underwent the reverse sequence. Due to the practical nature of the interventions, blinding of participants and operators was not possible. Randomisation, data measurement, and statistical analysis were conducted by clinicians blinded to allocation. Participants recorded their pain levels on a VAS immediately before and after each IER session. The difference in pre- and post-procedure scores represented the pain outcome. Two independent, blinded assessors measured VAS scores to ensure inter- and intra-rater reliability. Inclusion criteria required participants to be, over 16 years old and undergoing fixed appliance therapy involving IER. Exclusion criteria included systemic health conditions, chronic pain disorders, or previous hypersensitivity to IER procedures. All 34 participants completed the study, with no dropouts or adverse events. The mean increase in VAS pain score following manual IER was 18.5 mm (SD 16.6; 95% CI 15.6-21.3), compared with 15.6 mm (SD 16.0; 95% CI 12.9-18.3) for motor-driven IER. The mean difference in pain between techniques was 2.9 mm (SD 2.0; 95% CI -1.0 to 6.8), which was not statistically significant. No significant effects were observed for intervention order, age, or gender. Inter- and intra-rater agreement for VAS scoring was excellent (ICC = 1.00 for both). No participant reported harm, discomfort, or undue stress during participation. No significant difference in pain was found between manual and motor-driven IER techniques in orthodontic patients. Therefore, the choice of technique should be based on operator preference, efficiency, and patient comfort rather than pain expectations. Further research could explore other patient-reported outcomes, including treatment duration, anxiety, and perceived ease of procedure. ClinicalTrials.gov: NCT02455700.

This study aimed to assess the frequency of distoangulation of mandibular second premolars (MnP2) in individuals with complete unilateral cleft lip and palate, the angular changes of distoangulated MnP2 from the mixed to the permanent dentition, the clinical outcomes after the follow-up period and the frequency of other associated dental anomalies. The distoangulation group (DA) was composed of 37 patients (mean age 9.29, SD = 1.24 years, 15 females, 22 males) with distoangulation of MnP2. The control group (CG) was composed of 37 patients (mean age 9.9 years, SD = 1.13, 13 females, 24 males) without distoangulation of MnP2. Digital panoramic radiographs taken in the mixed dentition (T1) and early permanent dentition (T2) were analyzed in both groups. Longitudinal angular changes, the degree of root formation, second premolar depth, and the frequency of associated dental anomalies were analyzed. Intergroup comparison was performed with paired and independent t tests and χ² test (p < 0.05). The prevalence of MnP2 distoangulation in the mixed dentition was 18.5%. The DA showed a smaller initial distal angle (θ = 56.45° ± 6.72) compared to the CG (78.24° ± 6.09). The most common clinical outcome was the uprighting and spontaneous eruption of the MnP2 observed in 80.0% of the sample. MnP2 distoangulation was significantly associated with deciduous molar infraocclusion, agenesis of maxillary second premolar and ectopic eruption of maxillary first permanent molar. The frequency of MnP2 distoangulation among individuals with UCLP was 18.5%, with favorable spontaneous uprighting and eruption observed in most cases.

Maxillary transverse discrepancies are routinely addressed by palatal expansion. Nasal septum deviation is suspected to be related to these discrepancies. Current evidence using linear and angular measurements from two-dimensional radiographs on the effect of rapid palatal expansion on the nasal septum is not conclusive. The objective of this study was to apply three-dimensional geometric morphometric analyses to cone-beam computed tomography scans of the nasal septum to investigate changes in response to palatal expansion. Cone-beam computed tomography scans of the nasal septa of 71 subjects (53, expansion and 18, control) from 2 timepoints were segmented on using Mimics™ software. Anatomical landmarks and semilandmarks were digitized using Checkpoint™. Differences in septal deviation between the two timepoints were tested. Generalized Procrustes analysis and principal component analysis assessed overall shape differences and pattern variance in the septum. Least square regression was used to test for correlations. Heat maps visualized which areas exhibited the greatest amount of change. In the control group, none of the septum deviation variables changed significantly between the timepoints, while all were significantly different for the expansion group. Heatmaps showed greater increase in interlandmark distances for the expansion group compared with the controls, with the posterosuperior part of the septum bearing the greatest change and the central, inferior part showing the least change. Findings suggest that the septum does not straighten during expansion but continues to deviate with age.

Therapeutic mouthwashes are commonly used in dentistry to support mechanical plaque removal. Their interaction with orthodontic materials is increasingly studied due to potential effects on biocompatibility and biomechanics. To investigate in a systematic manner and evaluate the quality of the available evidence from randomized clinical trials regarding the effects of various mouthwashes on the morphology, structure, and mechanical properties of polymeric and metallic orthodontic materials. Comprehensive electronic and manual searches were conducted in seven databases from inception until August 2024. We analysed randomized controlled clinical studies that examined the impact of mouthwashes on the morphology, structure, and mechanical properties of both polymeric and metallic orthodontic materials. Data eligibility, data extraction, and risk of bias (RoB-2 tool) were performed independently. Ten studies were included, with most of them presenting some concerns in terms of bias. Chlorhexidine mouthrinse use did not affect the shear bond strength of polycarbonate brackets, the soldering alloys, as well as the stainless-steel bracket surfaces, but increased the roughness and friction of stainless-steel wires. The corrosion and mechanical properties of NiTi wires were not significantly affected by chlorhexidine. Rinsing with fluoride solutions increased surface roughness of NiTi wires, with more pronounced effects seen in acidulated fluoride solutions. While yield strength increased, no significant impacts on unloading force or modulus of elasticity was observed. Mouthwashes containing Salvadora persica did not significantly alter the surface topography of stainless-steel brackets and the roughness of stainless-steel archwires. The evidence from randomized clinical trials suggests that chlorhexidine- and fluoride-containing mouthwashes may impact the structure and certain mechanical properties of stainless-steel and NiTi archwires. While study limitations exist, clinicians should be mindful of possible effects on orthodontic treatment. Open Science Framework: osf.io/hz6wk.

Functional appliances, such as Twin Block and Herbst, produce dental and skeletal effects to correct Class II division 1 malocclusion. Although widely studied, there are no prospective randomized studies in the literature evaluating the effects of these appliances on the condyle (CO) and glenoid fossa (GF). To evaluate the differences in the CO and GF after treatment using Twin Block (TB) and Herbst (HB) functional appliances for skeletal Class II malocclusions. A single-center, two-arm, parallel-group randomized controlled trial. The sample consisted of 24 patients (12 in the TB group, 11.9 ± 1 year; 12 in the HB group, 12.5 ± 1.8 years) with Class II division 1 malocclusion. Cone beam computed tomography (CBCT) scans were recorded before (T0) and after (T1) treatment (12 months). Superimpositions were performed on Dolphin Imaging software, and partial 3D models of CO and GF were segmented in ITK-SNAP software. A coordinate system (X, Y, and Z axes) was created using Geomagic Qualify software in each 3D T0 model. CO and GF models were aligned in the 3D T0 and T1 models. A 3D centroid point was generated between T0 and T1 in each CO and GF. The TB group showed posterior growth in the right CO (1.3mm), left CO (1.3mm), right GF (0.8mm), and left GF (0.4mm). The HB group showed posterior growth in the right CO (1.4mm), left CO (1.7mm), right GF (0.1mm), and left GF (0.1mm). As the operator and patients were aware of the type of functional appliance, blinding could be performed only to assess and measure the CBCT exams. In both groups, CO and GF grew posteriorly; CO grew vertically in the superior direction, and GF in the inferior direction. The effects on CO and GF were similar when using TB or HB. ClinicalTrials.gov (ID: NCT02411812). It was registered before commencement.