Comparing Torque Transmission of Different Bracket Systems in Combination with Various Archwires Considering Play in the Bracket Slot: An In Vitro Study.

This study aims to examine the play between various archwires and bracket systems, exploring potential variations in angle values for specific torque and torque values for a given angle along different bracket systems. Therefore, seven brackets systems were evaluated in conjunction with different stainless steel archwires of varying dimensions (0.016″ × 0.022″, 0.018″ × 0.025″, and 0.019″ × 0.025″). Biomechanical behavior during torque development and transmission was assessed using a six-component force/torque sensor. Torque angles (5-45°) were specified with subsequent torque measurement, and the sequence was reversed by setting the torque (5-30 Nmm) and measuring the angle. A reference measurement with 0 Nmm torque served to evaluate bracket slot play. Bracket play (0 Nmm) during palatal load ranged between 20.06° and 32.50° for 0.016″ × 0.022″ wire, 12.83° and 21.11° for 0.018″ × 0.025″ wire, and 8.39° and 18.73° for 0.019″ × 0.025″ wire. The BioQuick® bracket exhibited the highest play, while Wave SL® and Damon® Q brackets demonstrated the lowest play (p < 0.001). Significant differences (p < 0.001) between the brackets were observed in the torque angles required to achieve torques of 5-20 Nmm. In summary, each bracket system has a different torque transmission, which is of great clinical importance in order to achieve correct torque transmission and avoid complications such as root resorption.

Influence of the design of 3D-printed indirect bonding trays and experience of the clinician on the accuracy of bracket placement.

PURPOSE: The aim was to investigate the influence of three different three-dimensional (3D)-printed bonding tray designs and professional experience on accuracy of indirect bracket placement. METHODS: Virtual bracket placement was performed on a scanned dental model using OnyxCeph software (Image Instruments, Chemnitz, Germany). Three different designs for indirect bonding trays (open, semi-open, and closed design) were created and produced using a 3D printer. To analyze the influence of professional experience, one of the three tray designs was produced twice. In this case, bracket placement was performed by an inexperienced dentist. Bracket positions were scanned after the indirect bonding procedure. Linear and angular transfer errors were measured. Significant differences between the target and actual situation were analyzed using the Kruskal-Wallis and χ2 test. RESULTS: All bonding tray designs resulted in comparable results. The results of the unexperienced dentist showed significantly higher deviations than those for the experienced orthodontist in the torque direction. However, the mean values were comparable. The open tray design exceeded the clinically acceptable limits of 0.25 mm and 1° more often. The inexperienced dentist exceeded these limits significantly more often than the experienced orthodontist in the vertical and torque direction. The immediate bracket loss rate showed no significant differences between the different tray designs. Significantly more bracket losses were observed for the inexperienced dentist during the procedure compared to the experienced orthodontist. CONCLUSIONS: The bonding tray design and professional experience had an influence on the exceedance of clinically relevant limits of positioning accuracy and on the bracket loss rate.

Biomechanical Simulation of Orthodontic En-Bloc Retraction Comparing Compound Technique and Sliding Mechanics Using a HOSEA Robotic Device.

En-bloc retraction is a common procedure in orthodontic therapy. The application of palatal root torque moments is required to control incisor inclination during retraction, yet studies comparing forces and moments with respect to different mechanics are lacking. This study aimed to investigate the forces and moments during orthodontic en-bloc retraction using a robotic biomechanical simulation system, comparing two distinct approaches: (I) compound technique [stainless steel (SS) combined with nickel-titanium (NiTi)] using industrially pretorqued retraction-torque-archwires (RTA) in combination with NiTi closed coil springs; (II) conventional sliding mechanics using SS archwires with manually applied anterior twist bends in combination with elastic chains. Two dimensions (0.017" × 0.025" and 0.018" × 0.025") and ten archwires per group were investigated using 0.022" slot self-ligating brackets. Kruskal-Wallis tests with a significance level of α = 0.05 were conducted. The biomechanical simulation showed that en-bloc retraction was characterized by a series of tipping and uprighting movements, differing significantly regarding the examined mechanics. Collateral forces and moments occurred in all groups. Notably, RTA exhibited fewer extrusive forces. The most bodily movement was achieved with the compound technique and the 0.018" × 0.025" RTA. Sliding mechanics exhibited maximum palatal root torque moments of more than 20 Nmm, exceeding recommended values.

Load Deflection Characteristics of Orthodontic Gummetal® Wires in Comparison with Nickel-Titanium Wires: An In Vitro Study.

The aim of this study was to investigate the load deflection characteristics of Gummetal® wires in comparison to nickel-titanium (NiTi) wires. Four different NiTi wires and one Gummetal® archwire were analyzed in two dimensions (0.014″ (0.36 mm) and 0.016″ × 0.022″ (0.41 mm × 0.56 mm)) and in two different orientations (edgewise and ribbonwise) using three-point bending tests at T = 37 °C. Force-displacement curves were recorded and analyzed. The Gummetal® 0.014″ wires exhibited higher forces compared to the NiTi wires at 2.0 mm deflection. At 1.0 mm deflection, the opposite pattern was observed. For the 0.016″ × 0.022″ Gummetal® wires, the forces were within the force interval of the NiTi wires at 2.0 mm deflection. At a deflection of 1.0 mm, no residual force was measurable for the Gummetal® wires. All the NiTi wires investigated showed hysteresis and a superelastic plateau. However, the Gummetal® did not form a plateau, but hysteresis was present. An easier plastic deformability compared to the NiTi wires was observed for all the tested geometries.

Investigation of Forces and Moments during Orthodontic Tooth Intrusion Using Robot Orthodontic Measurement and Simulation System (ROSS).

The Robot Orthodontic Measurement and Simulation System (ROSS) is a novel biomechanical, dynamic, self-regulating setup for the simulation of tooth movement. The intrusion of the front teeth with forces greater than 0.5 N poses a risk for orthodontic-induced inflammatory root resorption (OIIRR). The aim was to investigate forces and moments during simulated tooth intrusion using ROSS. Five specimens of sixteen unmodified NiTi archwires and seven NiTi archwires with intrusion steps from different manufacturers (Forestadent, Ormco, Dentsply Sirona) with a 0.012″/0.014″/0.016″ wire dimension were tested. Overall, a higher wire dimension correlated with greater intrusive forces Fz (0.012″: 0.561-0.690 N; 0.014″: 0.996-1.321 N; 0.016″: 1.44-2.254 N) and protruding moments Mx (0.012″: -2.65 to -3.922 Nmm; 0.014″: -4.753 to -7.384 Nmm; 0.016″: -5.556 to -11.466 Nmm) during the simulated intrusion of a 1.6 mm-extruded upper incisor. However, the 'intrusion efficiency' parameter was greater for smaller wire dimensions. Modification with intrusion steps led to an overcompensation of the intrusion distance; however, it led to a severe increase in Fz and Mx, e.g., the Sentalloy 0.016″ medium (Dentsply Sirona) exerted 2.891 N and -19.437 Nmm. To reduce the risk for OIIRR, 0.014″ NiTi archwires can be applied for initial aligning (without vertical challenges), and intrusion steps for the vertical levelling of extruded teeth should be bent in the initial archwire, i.e., 0.012″ NiTi.

Force-Controlled Biomechanical Simulation of Orthodontic Tooth Movement with Torque Archwires Using HOSEA (Hexapod for Orthodontic Simulation, Evaluation and Analysis).

This study aimed to investigate the dynamic behavior of different torque archwires for fixed orthodontic treatment using an automated, force-controlled biomechanical simulation system. A novel biomechanical simulation system (HOSEA) was used to simulate dynamic tooth movements and measure torque expression of four different archwire groups: 0.017″ x 0.025″ torque segmented archwires (TSA) with 30° torque bending, 0.018″ x 0.025″ TSA with 45° torque bending, 0.017″ x 0.025″ stainless steel (SS) archwires with 30° torque bending and 0.018″ x 0.025″ SS with 30° torque bending (n = 10/group) used with 0.022″ self-ligating brackets. The Kruskal-Wallis test was used for statistical analysis (p < 0.050). The 0.018″ x 0.025″ SS archwires produced the highest initial rotational torque moment (My) of -9.835 Nmm. The reduction in rotational moment per degree (My/Ry) was significantly lower for TSA compared to SS archwires (p < 0.001). TSA 0.018″ x 0.025″ was the only group in which all archwires induced a min. 10° rotation in the simulation. Collateral forces and moments, especially Fx, Fz and Mx, occurred during torque application. The measured forces and moments were within a suitable range for the application of palatal root torque to incisors for the 0.018″ x 0.025″ archwires. The 0.018″ x 0.025″ TSA reliably achieved at least 10° incisal rotation without reactivation.

Accuracy of maxillary positioning using computer-designed and manufactured occlusal splints or patient-specific implants in orthognathic surgery.

OBJECTIVE: To determine the accuracy of maxillary positioning using computer-designed and manufactured occlusal splints or patient-specific implants in orthognathic surgery. MATERIAL AND METHODS: A retrospective analysis of 28 patients that underwent virtually planned orthognathic surgery with maxillary Le Fort I osteotomy either using VSP-generated splints (n = 13) or patient-specific implants (PSI) (n = 15) was conducted. The accuracy and surgical outcome of both techniques were compared by superimposing preoperative surgical planning with postoperative CT scans and measurement of translational and rotational deviation for each patient. RESULTS: The 3D global geometric deviation between the planned position and the postoperative outcome was 0.60 mm (95%-CI 0.46-0.74, range 0.32-1.11 mm) for patients with PSI and 0.86 mm (95%-CI 0.44-1.28, range 0.09-2.60 mm) for patients with surgical splints. Postoperative differences for absolute and signed single linear deviations between planned and postoperative position were a little higher regarding the x-axis and pitch but lower regarding the y- and z-axis as well as yaw and roll for PSI compared to surgical splints. There were no significant differences regarding global geometric deviation, absolute and signed linear deviations in the x-, y-, and z-axis, and rotations (yaw, pitch, and roll) between both groups. CONCLUSIONS: Regarding accuracy for positioning of maxillary segments after Le Fort I osteotomy in orthognathic surgery patient-specific implants and surgical splints provide equivalent high accuracy. CLINICAL RELEVANCE: Patient-specific implants for maxillary positioning and fixation facilitate the concept of splintless orthognathic surgery and can be reliably used in clinical routines.

Biomechanical simulation of forces and moments of initial orthodontic tooth movement in dependence on the used archwire system by ROSS (Robot Orthodontic Measurement & Simulation System).

OBJECTIVES: Aim of this study was to determine the forces and moments during simulated initial orthodontic tooth movements using a novel biomechanical test setup. METHODS: The test setup consisted of an industrial precision robot with a force-torque sensor, a maxillary model and a control computer and software. Forces and moments acting on the corresponding experimental tooth during the motion simulations were dynamically measured for two 0.016" NiTi round archwires (Sentalloy Light/Sentalloy Medium). Intrusive (#1), rotational (#2) and angular (#3) tooth movements were simulated by a control program based on the principle of force control and executed by the robot. The results were statistically analysed using K-S-test and Mann-Whitney U test with a significance level of α = 5%. RESULTS: Sentalloy Medium archwires generated higher forces and moments than the Sentalloy Light archwires in all simulations. In simulation #1 the mean initial forces/moments reached 1.442 N/6.781 Nmm for the Light archwires and 1.637 N/9.609 Nmm for the Medium archwires. In movement #2 Light archwires generated mean initial forces/moments of 0.302 N/-8.271 Nmm whereas Medium archwires generated 0.432 N/-9.653 Nmm. Simulation #3 showed mean initial forces/moments of -0.122 N/8.477 Nmm from the Light archwires compared to -0.300 N/11.486 Nmm for the Medium archwires. SIGNIFICANCE: The measured forces and moments were suitable for initial orthodontic tooth movement in simulations #2 and #3, however inadequate in simulation #1. Reduced archwire dimensions (<0.016″) should be selected for initial leveling of vertical malocclusions.

Thermal Programming of Commercially Available Orthodontic NiTi Archwires.

The shape of superelastic Nickel-Titanium (NiTi) archwires can be adjusted with thermal treatments using devices such as the Memory-MakerTM (Forestadent), which potentially affects their mechanical properties. The effect of such treatments on these mechanical properties was simulated by means of a laboratory furnace. Fourteen commercially available NiTi wires (0.018″ × 0.025″) were selected from the manufacturers American Orthodontics, Dentaurum, Forestadent, GAC, Ormco, Rocky Mountain Orthodontics and 3M Unitek. Specimens were heat treated using different combinations of annealing duration (1/5/10 min) and annealing temperature (250-800 °C) and investigated using angle measurements and three-point bending tests. Complete shape adaptation was found at distinct annealing durations/temperatures for each wire ranging between ~650-750 °C (1 min), ~550-700 °C (5 min) and ~450-650 °C (10 min), followed by a loss of superelastic properties shortly afterwards at ~750 °C (1 min), ~600-650 °C (5 min) and ~550-600 °C (10 min). Wire-specific working ranges (complete shaping without loss of superelasticity) were defined and a numerical score (e.g., stable forces) was developed for the three-point bending test. Overall, the wires Titanol Superelastic (Forestadent), Tensic (Dentaurum), FLI CuNiTi27 (Rocky Mountain Orthodontics) and Nitinol Classic (3M Unitek) proved to be the most user-friendly. Thermal shape adjustment requires wire-specific working ranges to allow complete shape acceptance and high scores in bending test performance to ensure permanence of the superelastic behaviour.

Influence of growth structures and fixed appliances on automated cephalometric landmark recognition with a customized convolutional neural network.

BACKGROUND: One of the main uses of artificial intelligence in the field of orthodontics is automated cephalometric analysis. Aim of the present study was to evaluate whether developmental stages of a dentition, fixed orthodontic appliances or other dental appliances may affect detection of cephalometric landmarks. METHODS: For the purposes of this study a Convolutional Neural Network (CNN) for automated detection of cephalometric landmarks was developed. The model was trained on 430 cephalometric radiographs and its performance was then tested on 460 new radiographs. The accuracy of landmark detection in patients with permanent dentition was compared with that in patients with mixed dentition. Furthermore, the influence of fixed orthodontic appliances and orthodontic brackets and/or bands was investigated only in patients with permanent dentition. A t-test was performed to evaluate the mean radial errors (MREs) against the corresponding SDs for each landmark in the two categories, of which the significance was set at p < 0.05. RESULTS: The study showed significant differences in the recognition accuracy of the Ap-Inferior point and the Is-Superior point between patients with permanent dentition and mixed dentition, and no significant differences in the recognition process between patients without fixed orthodontic appliances and patients with orthodontic brackets and/or bands and other fixed orthodontic appliances. CONCLUSIONS: The results indicated that growth structures and developmental stages of a dentition had an impact on the performance of the customized CNN model by dental cephalometric landmarks. Fixed orthodontic appliances such as brackets, bands, and other fixed orthodontic appliances, had no significant effect on the performance of the CNN model.

Influence of the force magnitude of fixed functional appliances for class II subdivision 1 treatment-a cephalometric study.

PURPOSE: To investigate the skeletal and dental effects of a hybrid fixed functional appliance (FFA) used with different force magnitudes for class II subdivision 1 treatment. METHODS: Treatment records from 70 patients were evaluated: 35 patients were treated with a FFA with standard activation (SUS group) and 35 with a FFA with an additional force-generating spring (TSUS group). Two control groups were matched from the American Association of Orthodontists Foundation (AAOF) Craniofacial Growth Legacy Collection for comparison with the two treatment groups to determine skeletal and dental treatment effects. The cephalometric parameters at T0 (before treatment) and T1 (before debonding) were assessed using the Munich standard cephalometric analysis and by the sagittal occlusal analysis (SO) according to Pancherz. Data were analyzed statistically using SPSS. RESULTS: No statistically significant difference for any cephalometric parameter was observed between the SUS and TSUS groups concerning the measurements at T0 and T1. Both treatment groups exhibited an effective class II therapy mainly due to a significant reduction in SNA, and ANB and an increase in SNB. In contrast to the control group, as the result of treatment a skeletal class I was achieved. CONCLUSION: No significant statistical differences were observed between the patient group treated with the FFA with standard activation (SUS) and those treated with an additional spring (TSUS) regarding the cephalometric parameters investigated. Both variants were equally effective in treating class II division 1 malocclusions.

Force behaviour of elastic chains during a simulated gap closure in extraction therapy cases.

OBJECTIVE: Tooth movement with elastic chains requires defined force magnitudes. This study assessed the force behaviour of different elastic chains at different configurations of gap width. METHODS: Self-ligating brackets of teeth 5 & 6 and 2 & 3 were bonded to two movable aluminium plates. The plates were positioned on a joint basis with varying distances of 0.5, 2.0, 4.0, 6.0, and 8.0 mm. Reset forces of open and closed chains from four different manufacturers were investigated in four different configurations. Configurations differed in either having an additional intermediate ring within the gap (#1, #3) and/or having intermediate rings between teeth adjacent to the gap (#1, #2), or by no intermediate rings (#4). Forces were measured with a universal testing machine. The results were statistically analysed using U-test, H-test and (if applicable) post-hoc tests with a significance level of .05. RESULTS: Configurations #1 and #3, and #2 and #4 formed homogenous subgroups (P < .001). Initial forces in configuration #4 were significantly higher than in configuration #3 (P = .029). Initial forces in closed chains were significantly higher than for open chains (P = .029). CONCLUSIONS: Intermediate chain rings adjacent to the gap are not required to modulate the force. In contrast, leaving a ring unapplied in the tooth gap can help modulate the force. Open thermoset chains with an additional ring within the gap (#3) seem to produce suitable initial forces for a gap closure of 4 mm. With a residual gap width of <2 mm, open thermoset chains and closed thermoset chains (#4) seem suitable.

Functional Orthodontic Treatment of Mandibular Condyle Fractures in Children and Adolescent Patients: An MRI Follow-Up.

BACKGROUND: The purpose of this study was to retrospectively evaluate and follow up a conservative treatment approach with functional orthodontic appliances for the management of mandibular condyle fractures in children and adolescent patients. METHODS: Between 2020 and 2022, the treatment records of patients with mandibular condyle fractures receiving a functional orthodontic treatment (FOT) were evaluated. In addition to the clinical and functional findings, magnetic resonance images of the mandibular condyles and surrounding structures were assessed. RESULTS: Out of 61 patients, 8 met the inclusion criteria. The follow-up examination records showed no functional limitations. In 75% of cases, mild midline deviations persisted (mean 1.1 mm) without significant alterations to the occlusal relationships. Magnetic resonance imaging (MRI) showed the remodeling of the condyles and the restitution of the ramus heights, even in dislocated and displaced fractures. In three cases, a partial displacement of the articular disc was observed at the follow-up. No differences in the remodeling patterns were noted depending on age, sex, or fracture location. CONCLUSIONS: A FOT led to favorable functional and morphologic outcomes, supporting the concept of a conservative functional approach in children and adolescent patients. Functional adjunctive therapy should be considered in the conservative treatment of mandibular condyle fractures in growing patients.

Dental management before radiotherapy of the head and neck region: 4-year single-center experience.

OBJECTIVE: To review our experience with a standardized dental management approach in patients with planned radiotherapy of the head and neck region based on preradiation and follow-up data. MATERIAL AND METHODS: Records of patients who underwent radiotherapy between June 2016 and November 2020 were reviewed. Data on dental findings and therapeutic recommendations were extracted from a prospectively managed database. Hospital records were used to obtain follow-up data. RESULTS: Two hundred eighty-one patient records were identified. After the exclusion of 81 patients because of incomplete data, 200 patients were included in the study. Dental findings relevant to radiotherapy were found in 144 cases (72.0%). Teeth extractions were recommended in 112 (56.0%) patients. Follow-up data were available for 172 (86.0%) patients (mean follow-up: 16.8 ± 10.7 months). Radiodermatitis was the most frequently observed sequela of radiotherapy (42.4%), followed by dysphagia (38.4%) and stomatitis (36.6%). Osteoradionecrosis was observed in only 2.3% of the patients. CONCLUSION: Dental findings relevant to planned radiotherapy were frequent and in many cases resulted in recommendations for teeth extraction. Based on our standardized dental management protocol, we observed low rates of late oral complications after radiotherapy of the head and neck region.

Accuracy of 3D Tooth Movements in the Fabrication of Manual Setup Models for Aligner Therapy.

Background: The clinical outcome of aligner therapy is closely related to the precision of its setup, which can be manually or digitally fabricated. The aim of the study is to investigate the suitability of manual setups made for aligner therapy in terms of the precision of tooth movements. Methods: Six dental technicians were instructed to adjust each of eleven duplicate plaster casts of a patient models as follows: a 1 mm pure vestibular translation of tooth 11 and a 15° pure mesial rotation of tooth 23. The processed setup models were 3D scanned and matched with the reference model. The one-sample Wilcoxon signed-rank test (p < 0.05) was used for evaluation. Results: The overall precision of the translational movement covers a wide range of values from 0.25 to 2.26 mm (median: 1.09 mm). The target value for the rotation of tooth 23 was achieved with a median rotation of 9.76° in the apical-occlusal direction. Unwanted movements in the other planes also accompanied the rotation. Conclusions: A manual setup can only be fabricated with limited precision. Besides the very high variability between technicians, additional unwanted movements in other spatial planes occurred. Manually fabricated setups should not be favored for aligner therapy due to limited precision.

Bracket Transfer Accuracy with the Indirect Bonding Technique-A Systematic Review and Meta-Analysis.

PURPOSE: To investigate the bracket transfer accuracy of the indirect bonding technique (IDB). METHODS: Systematic search of the literature was conducted in PubMed MEDLINE, Web of Science, Embase, and Scopus through November 2021. SELECTION CRITERIA: In vivo and ex vivo studies investigating bracket transfer accuracy by comparing the planned and achieved bracket positions using the IDB technique were considered. Information concerning patients, samples, and applied methodology was collected. Measured mean transfer errors (MTE) for angular and linear directions were extracted. Risk of bias (RoB) in the studies was assessed using a tailored RoB tool. Meta-analysis of ex vivo studies was performed for overall linear and angular bracket transfer accuracy and for subgroup analyses by type of tray, tooth groups, jaw-related, side-related, and by assessment method. RESULTS: A total of 16 studies met the eligibility criteria for this systematic review. The overall linear mean transfer errors (MTE) in mesiodistal, vertical and buccolingual direction were 0.08 mm (95% CI 0.05; 0.10), 0.09 mm (0.06; 0.11), 0.14 mm (0.10; 0.17), respectively. The overall angular mean transfer errors (MTE) regarding angulation, rotation, torque were 1.13° (0.75; 1.52), 0.93° (0.49; 1.37), and 1.11° (0.68; 1.53), respectively. Silicone trays showed the highest accuracy, followed by vacuum-formed trays and 3D printed trays. Subgroup analyses between tooth groups, right and left sides, and upper and lower jaw showed minor differences. CONCLUSIONS AND IMPLICATIONS: The overall accuracy of the indirect bonding technique can be considered clinically acceptable. Future studies should address the validation of the accuracy assessment methods used.

Influence of normal forces on the frictional behavior in tribological systems made of different bracket types and wire dimensions.

The aim of the present work was measuring the effect of varying normal forces on frictional forces applied to different bracket types in combination with archwires made of NiTi and stainless steel of variable cross section. The measurements were carried out in artificial saliva. Three-way ANOVA and Bonferroni post-hoc tests (α=0.05) were applied. Except for one subgroup the combination of normal force, bracket system and wire dimension had significant effect on friction (p<0.001) as friction increased with increasing normal forces. Only moderately tied ligatures or passive self-ligating brackets generate low friction forces. There was a statistically significant order (0.016"×0.022"<0.018"×0.025"<0.019"×0.025") for stainless steel wire material. Finite element modeling simulation showed the increasing effect of active clip force on friction especially for 0.025" wire profiles. If compared to NiTi wires, stainless steel archwires delivered higher friction. Combinations between wire-type and ligation should be chosen carefully for the intended treatment step.

Bracket transfer accuracy with two different three-dimensional printed transfer trays vs silicone transfer trays.

OBJECTIVES: To compare the transfer accuracy of two different three-dimensional printed trays (Dreve FotoDent ITB [Dreve Dentamid, Unna, Germany] and NextDent Ortho ITB [NextDent, Soesterberg, the Netherlands]) to polyvinyl siloxane (PVS) trays for indirect bonding. MATERIALS AND METHODS: A total of 10 dental models were constructed for each investigated material. Virtual bracket placement was performed on a scanned dental model using OnyxCeph (OnyxCeph 3D Lab, Chemnitz, Germany). Three-dimensional printed transfer trays using a digital light processing system three-dimensional printer and silicone transfer trays were produced. Bracket positions were scanned after the indirect bonding procedure. Linear and angular transfer errors were measured. Significant differences between mean transfer errors and frequency of clinically acceptable errors (<0.25 mm/1°) were analyzed using the Kruskal-Wallis and χ2 tests, respectively. RESULTS: All trays showed comparable accuracy of bracket placement. NextDent exhibited a significantly higher frequency of rotational error within the limit of 1° (P = .01) compared with the PVS tray. Although PVS showed significant differences between the tooth groups in all linear dimensions, Dreve exhibited a significant difference in the buccolingual direction only. All groups showed a similar distribution of directional bias. CONCLUSIONS: Three-dimensional printed trays achieved comparable results with the PVS trays in terms of bracket positioning accuracy. NextDent appears to be inferior compared with PVS regarding the frequency of clinically acceptable errors, whereas Dreve was found to be equal. The influence of tooth groups on the accuracy of bracket positioning may be reduced by using an appropriate three-dimensional printed transfer tray (Dreve).

Clinical effects with customized brackets and CAD/CAM technology: a prospective controlled study.

OBJECTIVE: Nowadays, CAD/CAM technologies enrich orthodontics in several ways. While they are commonly used for diagnoses and treatment planning, they can also be applied to create individualized bracket systems. The purpose of this prospective quasi-randomized study was to evaluate the clinical efficiency of a customized bracket system and its comparison with directly bonded conventional self-ligating bracket treatment. MATERIALS AND METHODS: Altogether 38 patients were separated into two groups, treated either with direct bonded self-ligating brackets (Damon, Ormco, USA) or with indirect bonded customized CAD/CAM brackets (Insignia™, Ormco, USA). Overall treatment time, number of treatment appointments, number of lost or repositioned brackets, number of arch wires and wire bends, Little Irregularity Index, cephalometric analyses and ABO scores were compared. Superimpositions of the virtual set-ups and the treatment results of the CAD/CAM group were performed to evaluate the clinical realization of the treatment planning. RESULTS: No differences between both treatment groups were found concerning overall treatment time, number of appointments and number of archwire bends. Bonding failures occurred more often using the CAD/CAM system. Indirectly bonded brackets did not have to be repositioned as often as directly bonded brackets. Treatment results with both systems were similar concerning their effects on the reduction of ABO scores. The number of used archwires was higher in the CAD/CAM group. Treatment with both systems led to further proclination of the incisors. Proclination in the lower jaw was greater than proclination in the upper jaw, and there was a statistically significant difference between the two treatment systems. Comparing the treatment results with the virtual set-ups, mesial positions were met best, followed by vertical positions. Transversal positions showed the greatest discrepancies. Concerning angles, values of angulation showed greatest accordance to the virtual set-up, while values of inclinations showed greatest discrepancies. CONCLUSION: In comparison with a direct bonded self-ligating bracket system the use of indirect bonded customized CAD/CAM brackets showed only minor influence on treatment efficiency and treatment outcomes. Transversal expansion, deep bite correction, expression of torque and anchorage loss remain challenges in the treatment with straight-wire appliances. Trial registration DRKS, DRKS00024350. Registered 15 February 2021, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00024350 .

Effect of different media on frictional forces between tribological systems made from self-ligating brackets in combination with different stainless steel wire dimensions.

The purpose was to determine the effect of different environments (artificial saliva, human saliva, distilled water, dry storage) on frictional forces between various tribological systems made from self-ligating brackets in combination with stainless-steel wires (dimensions: 0.016″×0.022″, 0.018″×0.025″ and 0.019″×0.025″). An universal testing-machine applied a normal force of 1 N. Two-way ANOVA and Tukey post-hoc tests (α=5%) were used. Saliva had significantly higher frictional forces (p<0.001). Yet, the influence of the media depends on the wire dimensions. The results were not as straightforward as in 0.018″×0.025″, which had a clear order (dry storage