Search

As an innovative approach to overcome the rate-limiting staging of conventional aligners, using shape memory polymers (SMPs) as aligners’ materials was investigated in this in vitro study. The ability of SMPs to shape recover and consequently move tooth, upon appropriate stimuli, was evaluated on a typodont model before clinical application. The study design was to achieve 1.9 mm correction movement of an upper central incisor by one aligner after multiple steps/activation. A custom-made aligned typodont model with a movable upper central incisor was scanned. Using an orthodontic software and a 3D printer, resin-models were generated. Seven aligners of ClearX sheets (SMPs) were fabricated by thermoforming on the resin aligned model. Each aligner was tested for repositioning of the central incisor in the typodont model. The model was scanned after each step and the corrective movement was measured through the superimposition of scans. Results showed that the total correction efficiency of the SMPs’ aligner was ≈93% (1.76 mm). The corrective movement was 0.94 ± 0.04 mm after the reforming step, 0.66 ± 0.07 mm after the first activation step, and 0.15 ± 0.10 mm after the second activation step. It was concluded that aligners made of SMPs could have a promising future-use in orthodontic aesthetic treatment.

To evaluate the efficacy of chewing gum on the intensity of pain in patients undergoing orthodontic treatment. A search strategy that included both a manual search and a search of electronic databases was implemented; the electronic databases included PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), ScienceDirect, Scopus, and EBSCO. Only randomized controlled trials were included in this study. All of the studies were assessed independently and in duplicate in accordance with the exclusion and inclusion criteria. The Cochrane risk of bias tool was used to evaluate the risk of bias within the included studies, and the GRADE approach was used to evaluate the certainty of evidence. Sixteen RCTs were included in the final analysis. The meta-analysis revealed that chewing gum significantly reduced pain intensity in comparison to pharmacologic agents (mean difference [MD] −0.50 [95% confidence interval {CI} −0.90 to −0.10], P =.01). When compared with a placebo, chewing gum significantly reduced pain intensity (MD −0.60 [95% CI −1.06 to −0.13], P =.01), while bite wafer and chewing gum groups had the same levels of reduction in pain intensity (MD −0.15 [95% CI −0.56 to 0.26], P =.48). In patients undergoing fixed orthodontic treatment, chewing gum was significantly more effective than both pharmacologic agents and placebo in reducing orthodontic pain 24 hours after the initial placement of the archwire. [ABSTRACT FROM AUTHOR]

To evaluate the predictability of (SARDAC) technique regarding torque control and vertical movement during en-masse retraction in lingual orthodontics. Different setups of the SARDAC technique were tested during en-masse retraction in lingual orthodontics. Simulated retraction was performed using the Orthodontic Measurement and Simulation System (OMSS). Lever arms were welded between the lateral incisor and canine brackets bilaterally on a 0.017"X0.025" inch maxillary lingual stainless- steel wire. Bilateral, nickel titanium coil springs were used to apply a retraction force of 1.5 N per side on para-median mini-screws, inter radicular mini-screws and to the first molar brackets. Regarding the torque, the group where the force was applied between the 15 mm lever-arm and the first molar bracket, was the only group that showed statistically significant difference (palatal root torque) during en-masse retraction compared to the control group. Regarding the vertical movement, no statistically significant difference was found between any mechanical setup and the control group. SARDAC technique is predictable and efficient in controlling torque and vertical movement during en-masse retraction in lingual orthodontics. [ABSTRACT FROM AUTHOR]

The aim of the study is to investigate the effects of artificial aging by thermocycling and mechanical loading on force/torque delivery by thermoplastic orthodontic aligners. Ten thermoformed aligners, made of Zendura™ thermoplastic polyurethane sheets, were aged over two weeks in deionized water by thermocycling alone (n = 5) and by both thermocycling and mechanical loading (n = 5). The force/torque generated on upper second premolar (Tooth 25) of a plastic model was measured before aging (as control), and after 2, 4, 6, 10, and 14 days of aging, using a biomechanical set-up. Before aging, the extrusion-intrusion forces were in the range of 2.4–3.0 N, the oro-vestibular forces were 1.8–2.0 N, and the torques on mesio-distal rotation were 13.6–40.0 Nmm. Pure thermocycling had no significant effect on the force decay of the aligners. However, there was a significant decrease in force/torque after 2 days of aging for both thermocycling and mechanical loading aging group, which is no longer significant over 14 days of aging. In conclusion, artificial aging of aligners in deionized water with both thermocycling and mechanical loading results in a significant decrease in force/torque generation. However, mechanical loading of aligners has a greater impact than pure thermocycling. [Display omitted] • Thermomechanical loading of aligners results in significant force decay over time. • Pure thermocycling has insignificant effect on force generation by aligners. • Mechanical loading of aligners has a greater impact than thermocycling alone. • The significant force decay by aligners occurs in the first two days. • Force/torque generation by orthodontic aligners is direction dependent. [ABSTRACT FROM AUTHOR]

The periodontal ligament is a complex tissue with respect to its biomechanical behaviour. It is important to understand the mechanical behaviour of the periodontal ligament during physiological loading in healthy patients as well as during the movement of the tooth in orthodontic treatment or in patients with periodontal disease, as these might affect the mechanical properties of the periodontal ligament (PDL). Up to now, only a limited amount of in vivo data is available concerning this issue. The aim of this study has been to determine the time dependent material properties of the PDL in an experimental in vivo study, using a novel device that is able to measure tooth displacement intraorally. Using the intraoral loading device, tooth deflections at various velocities were realised in vivo on human teeth. The in vivo investigations were performed on the upper left central incisors of five volunteers aged 21–33 years with healthy periodontal tissue. A deflection, applied at the centre of the crown, was linearly increased from 0 to 0.15 mm in a loading period of between 0.1 and 5.0 s. Individual numerical models were developed based on the experimental results to simulate the relationship between the applied force and tooth displacement. The numerical force/displacement curves were fitted to the experimental ones to obtain the material properties of the human PDL. For the shortest loading time of 0.1 s, the experimentally determined forces were between 7.0 and 16.2 N. The numerically calculated Young's modulus varied between 0.9 MPa (5.0 s) and 1.2 MPa (0.1 s). By considering the experimentally and numerically obtained force curves, forces decreased with increasing loading time. The experimental data gained in this study can be used for the further development and verification of a multiphasic constitutive law of the PDL. [ABSTRACT FROM AUTHOR]

Objective: To compare the archwires inserted during the final stages of the orthodontic treatment with the generated moments at 0.018- and 0.022-inch brackets. Materials and Methods: The same bracket type, in terms of prescription, was evaluated in both slot dimensions. The brackets were bonded on two identical maxillary acrylic resin models, and each model was mounted on the orthodontic measurement and simulation system. Ten 0.017 x 0.025-inch TMA and ten 0.017 x 0.025-inch stainless steel archwires were evaluated in the 0.018- inch brackets. In the 0.022-inch brackets, ten 0.019 x 0.025-inch TMA and ten 0.019 x 0.025-inch stainless steel archwires were measured. A 15° buccal root torque (+15°) and then a 15° palatal root torque (-15°) were gradually applied to the right central incisor bracket, and the moments were recorded at these positions. A f-test was conducted to compare the generated moments between wires within the 0.018- and 0.022-inch bracket groups separately. Results: The 0.017 x 0.025-inch archwire in the 0.018-inch brackets generated mean moments of 9.25 Nmm and 14.2 Nmm for the TMA and stainless steel archwires, respectively. The measured moments in the 0.022-inch brackets with the 0.019 x 0.025-inch TMA and stainless steel archwires were 6.6 Nmm and 9.3 Nmm, respectively. Conclusion: The 0.017 x 0.025-inch stainless steel and ß-Ti archwires in the 0.018-inch slot generated higher moments than the 0.019 x 0.025-inch archwires because of lower torque play. This difference is exaggerated in steel archwires, in comparison with the β-Ti, because of differences in stiffness. The differences of maximum moments between the archwires of the same cross-section but different alloys were statistically significant at both slot dimensions. [ABSTRACT FROM AUTHOR]

The introduction of nickel-titanium (NiTi) wires has revolutionized the field of orthodontics by delivering light continuous forces over a wider range of displacements than the traditional stainless-steel wires. Over the years improvements in NiTi wire manufacturing and composition have been introduced; however, the claimed wire capabilities are not always easy to verify in the clinical setting. We aim at presenting an overview of the use and applications of NiTi alloys in orthodontics. The implications of the metallurgical and mechanical properties and intraoral aging of the wires in their clinical application is discussed. Finally, time variants of orthodontic therapy duration with the use of NiTi and alternative arch wires are presented, and the clinical implication of superelasticity is analyzed. [ABSTRACT FROM AUTHOR]