Forces and moments generated by removable thermoplastic aligners: Incisor torque, premolar derotation, and molar distalization

Objective: To determine whether orthodontic treatment with removable aligners vs fixed orthodontic appliances is associated with a different frequency of orthodontically induced external apical root resorption (OIEARR) when genetic, radiographic, and clinical factors are accounted for. Materials and Methods: Three hundred seventy-two orthodontic patients treated with removable aligners (Invisalign) or fixed appliances were genetically screened for interleukin 1B gene (IL1B) (rs1143634), interleukin 1 receptor antagonist gene (IL1RN) (rs419598), and osteopontin gene (SPP1) (rs9138/rs11730582). Twelve clinical variables, potentially associated with OIEARR, were also considered. Subjects were divided according to the presence of radiographically determined OIEARR (.2 mm). The association between OIEARR and appliance type, and radiographic, clinical and genetic factors, was assessed using backward stepwise conditional logistic regression. Odds ratios (ORs) and 95% confidence intervals (CIs) were reported. Results: Reliability of the methods was adequate. Clinical case complexity (American Board of Orthodontics [ABO] Discrepancy Index) (OR: 1.032; 95% CI: 1.005-1.061; P ¼ .021) and extent of incisor apical displacement in the sagittal plane (OR: 1.478; 95% CI: 1.285-1.699; P ¼ .001) were associated with an increased OIEARR risk. After adjusting for associations between clinical/ radiographic/genetic factors, there were no statistically significant differences with respect to OIEARR or type of orthodontic appliance used, whether removable aligners or fixed appliances (OR: 1.662; 95% CI: 0.945-2.924; P ¼ .078). Only subjects homozygous for the T allele of IL1RN (rs419598) were more prone to OIEARR during orthodontic treatment (OR: 3.121; CI: 1.93-5.03; P , .001). Conclusions: A similar OIEARR predisposition was identified using either removable aligners (Invisalign) or fixed appliances. (Angle Orthod. 2017;87:3-10)

Section: Discussionmentioning

confidence: 99%

Orthodontically induced external apical root resorption in patients treated with fixed appliances vs removable aligners

Iglesias-Linares

Sonnenberg

Beatriz

et al. 2016

“…However, with respect to the large difference in the required M/F ratio of 0 mm, it must be emphasized that even for aligning a palatally displaced maxillary incisor, aligners without any modifications such as specific pressure points or stiffer cervical regions do not seem to be efficient for bodily tooth movement. 18 Furthermore, the forces and moments generated by the aligner are significantly influenced by the direction and type of tooth displacement in the setup as well as the morphology of the tooth and the location of its center of resistance. These aspects have also to be considered when transferring the results of this in vitro study to specific clinical situations.…”

Section: Discussionmentioning

confidence: 99%

Forces and moments delivered by novel, thinner PET-G aligners during labiopalatal bodily movement of a maxillary central incisor: An in vitro study

Elkholy

Schmidt

Jäger

et al. 2016

Objective: To evaluate whether overloading of teeth can be avoided by utilizing aligners with reduced thicknesses of 0.4 mm or 0.3 mm. Materials and Methods: The experimental setup included an acrylic maxillary jaw model with tooth 11 separated and fixed via a 3-D force-moment transducer to a hexapod for experimental movement. Aligners tested were fabricated on duplicate stone models using commercially available polyethylene terephthalate glycol (PET-G) foils with thicknesses between 0.5 and 0.75 mm, and novel 0.4-mm-and 0.3-mm-thick foils. With the test aligner seated, 11 was bodily displaced in a labiopalatal direction in the range of 60.25 mm while all six force-and-moment components exerted on this tooth were registered. Results: With the thinnest commercially available 0.5-mm aligner, median forces of À7.89 N and 8.37 N were measured for the maximum 0.25-mm movement of 11 in a labial and palatal direction, respectively. In comparison, force values were 35% and 71% lower for the novel aligners with a thickness of 0.4 mm and 0.3 mm, respectively. Conclusions: Novel ''leveling'' aligners with reduced thickness may reduce overloading of individual teeth during aligner therapy. Due to form instability of 0.3-mm aligners, we suggest a novel sequence of 0.4-0.5-0.75 mm for aligner systems using several foil thicknesses for load graduation within single setup steps. This would combine low stiffness of the initial aligner and relatively constant load increases throughout the treatment. (Angle Orthod. 2016;86:883-890)

“…In accordance with the existing literature, the initial distalizing force was 1 N. 18 Two weeks before beginning the study, all the subjects underwent a supragingival prophylaxis and were given oral hygiene instructions to follow at home to eliminate inflammation. The study lasted for 21 days and involved three visits.…”

Section: Interventionmentioning

confidence: 99%

Biochemical markers of bone metabolism during early orthodontic tooth movement with aligners

Castroflorio

Gamerro

Caviglia

et al. 2016

Objective: To evaluate the expression of receptor activator of nuclear factor-kappa ligand (RANKL), osteoprotegerin (OPG), osteopontin (OPN), interleukin 1b (IL-1b), and transforming growth factor ß1 (TGF-ß1) in the gingival crevicular fluid (GCF) of teeth subjected to orthodontic forces released by aligners. Materials and Methods: A total of 10 healthy, adult patients were selected to participate in this split-mouth study. The treatment plan was designed to obtain only one movement with the first aligner: distalization of a second molar. GCF samples were obtained from pressure and tension sites of the test tooth and from the mesiobuccal and distobuccal sites of the control tooth. The GCF sample volumes were measured using a Periotron 8000. Levels of TGF-b, IL-1b, RANKL, OPG, and OPN were measured by enzyme-linked immunosorbent assay. Results: IL-1b showed a significant increase at the pressure sites after 1 week and 3 weeks with respect to baseline (P , .05) compared with control sites. The kinetics of TGF-1b and OPN were characterized by a significant increase at the tension sites of the test teeth (P , .05) after 3 weeks from the application of orthodontic force. The RANKL level was significantly increased at pressure and tension sites after 1 hour and after 1 week from the application of the orthodontic forces (P ¼ .023 and P ¼ .043, respectively). Conclusions: An increased concentration of bone modeling and remodeling mediators at the pressure sites (IL-1b, RANKL) and tension sites (TGF-1b, OPN) was observed. These scenarios are compatible with previous in vivo and in vitro studies investigating the biological effects of orthodontic tooth movement. (Angle Orthod. 2017;87:74-81)