The Effect of Extrinsic Factors on the Mechanical Behavior and Structure of Elastic Dental Ligatures and Chains

Force provided by elastomers used in orthodontics can be affected by several factors present in the oral cavity. The aim of our study was to investigate the role of mouthwashes, toothbrushing, and smoking in the force decay of such elastomers. Tensile strength, changes in the force continuously exerted, and force decay of elastic chains (Ortho Organizer and Masel Short Power Chain) and elastic ligatures (Dentaurum and Masel) by two separate manufacturers were measured. Measurements were initially made on untreated elastics, followed by exposure to different environmental factors including cigarette smoke, toothbrushing (mechanical plaque control), and two different mouthwashes (chemical plaque control). Changes on the surface of the elastics were studied with scanning electron microscopy (SEM). Untreated Masel elastic ligature showed lower tensile strength than Dentaurum elastic ligature (2339 cN vs. 3660 cN), while significantly higher tensile strength was measured for Ortho Organizer elastic chains than Masel chains (2639 cN vs. 1324 cN). The decrease in the elastic force of Masel ligature was greater in response to all external factors compared to Dentaurum. Although brushing with toothpaste and toothbrush impacted the force of both Masel and Ortho organizer ligatures negatively, force degradation was more apparent in the case of the Ortho organizer. Surface changes were more visible when applying Curasept mouthrinse, however force decay was higher in the Corsodyl group. Mechanical and chemical plaque control can influence the tensile strength and force decay of orthodontic elastomers, which should be considered by selecting the elastomers or determining their changing interval for the practice.

Force decay of polyethylene terephthalate glycol aligner materials during simulation of typical clinical loading/unloading scenarios

Background This in vitro study investigated the effect of three distinct daily loading/unloading cycles on force delivery during orthodontic aligner therapy. The cycles were applied for 7 days and were designed to reflect typical clinical aligner application scenarios. Materials and methods Flat polyethylene terephthalate glycol (PET-G) specimens (Duran®, Scheu Dental, Iserlohn, Germany) with thicknesses ranging between 0.4 and 0.75 mm were tested in a three-point-bending testing machine. Measurements comprised loading/unloading intervals of 12 h/12 h, 18 h/6 h, and 23 h/1 h, and specimens were exposed to bidistilled water during loading to simulate intraoral conditions. Results A very large decay in force for the PET‑G specimens could already be observed after the first loading period, with significantly different residual force values of 24, 20, and 21% recorded for the 12 h/12 h, 18 h/6 h, and 23 h/1 h loading/unloading modes, respectively (Mann–Whitney U test, p < 0.01). In addition, further decays in force from the first to the last loading period at day 7 of 13.5% (12 h/12 h), 9.7% (18 h/6 h), and 8.4% (23 h/1 h) differed significantly among the three distinct loading modes (Mann–Whitney U test, p < 0.01). Conclusion Although the initial material stiffness of PET‑G is relatively high, the transmission of excessive forces is attenuated by the high material-related force decay already within a few hours after intraoral insertion.

Comparison of force decay pattern in orthodontic elastomeric chains and NiTi closed coil springs, affected by five different mouthwashes: An in vitro Study

Background: The aim of this study was to compare the force decay pattern of elastomeric chains and NiTi coil springs which were exposed to five different commercially available mouthwashes.Methods: In this in vitro study, 60 pieces of elastomeric chain (EC) and 60 NiTi closed coil springs (CS) were divided into 6 groups. The specimens were exposed to one of these mouthwashes twice a day for 60 seconds: Listerine, chlorhexidine, Orthokin, Persica, fluoride and artificial saliva as the control group. The elastomeric chains and NiTi springs were stretched so that they exert the initial force of 250 gr. Their force was measured on the 1, 7, 14 and 28 following days by means of a digital gauge.Results: Elastomeric chains and coil springs had force decrease over time, but EC' force reduction was greater with the highest reduction rate in the first week. However, in the CS group, the force decrease wasn't statistically significant in the first two weeks. After 28 days in the control groups, 49.8% of the initial force was remained in ECs while the value was 93.3% for CSs. In comparison between mouthwashes, in EC groups, in all mouthwashes except Persica, the remained force was statistically less than control group.Conclusion: Force degradation of elastomeric chains could be exacerbated by use of mouthwashes. About coil springs, force decay was also observed. However, it was not statistically significant. Force reduction was detectable after four weeks of coil springs usage, but in EC groups, the greatest reduction was after the first week.

A Comparison of Force Decay between Coil Spring, Elastomeric Chain and Tie-backs in Various Alcohol Concentrations found in Mouth Rinse: An In-vitro Study

Background: The ability to close space efficiently in Orthodontics is of major clinical importance. Elastomeric power chain, coil spring, and tiebacks are commonly used in Orthodontics to achieve tooth movement during the closure of spaces. Many mouth rinses which are used by the patients to achieve good oral hygiene affect the properties of the material used during treatment resulting in force decay if they contain alcohol. Aim: To know the effect of mouth rinses containing different alcohol Concentrations on the force decay of retraction materials. Materials and Methods: A study was carried out to test the effect of alcohol exposure found in mouth rinses on orthodontic NiTi closing coils, elastomeric chains, and tie-back. A total of 135 specimens were divided into one control group and two test groups submerged in artificial saliva at 37⁰ C. Two test groups each of them exposed to different alcohol-containing mouthwashes (Listerine and Povidone-iodine) for 60 seconds twice a day and the control group were exposed only to deionized (DI) water for 28 days. Force measurements were taken at six-time points (initial, 7 days, 14 days, 21 days, and 28 days) using a digital force gauge. Results: The comparison between the tensile strength was made by digital force gauge and the p-value (≤ 0.05) for tensile strength was derived by ANOVA test, multiple comparisons, and Tukey’s correction. Significant force decay was seen in test groups when compared to the control group. Conclusion: Force degradation of retraction products used during orthodontic treatment was effected by mouth rinses containing alcohol.

Effect of sodium fluoride in chlorhexidine mouthwashes on force decay and permanent deformation of orthodontic elastomeric chain

Introduction: Orthodontic elastomeric chain is polyurethane elastomer that is widely used among orthodontists due to its functions. Chlorhexidine (CHX) and sodium fluoride (NaF) are listed in mouthwash composition which could affect the mechanical properties of the elastomeric chain. This study was aimed to analyze the effect of sodium fluoride in chlorhexidine mouthwashes on force decay and permanent deformation of orthodontic elastomeric chains. Methods: This research is an experimental analytic laboratory with pretest-posttest control group design. 150 samples of orthodontic chains were divided into three groups. Group 1: artificial saliva (control group); Group 2: 0,1% chlorhexidine gluconate solution (CHX); Group 3: 0,1% chlorhexidine digluconate with sodium fluoride solution (CHX-NaF). The orthodontic elastomeric chain was stretched and maintained at a standardized distance equivalent to a force of 300 g. The measurement of force decay and permanent deformation were performed with digital force gauge and digital caliper (0.01mm) at intervals of the first, seventh, fourteenth, twenty-first, and twenty-eighth days, respectively. Results: The force decay and permanent deformation of the elastomeric chain compared between three groups (control, CHX mouthwash and CHX+NaF mouthwash) showed did not have any significantly different (p-value>0,05) at the first, seventh, fourteenth, twenty-first, and twenty-eighth days, respectively. Conclusion: Sodium fluoride in chlorhexidine mouthwash showing no significant difference among saliva, CHX mouthwash and CHX+NaF mouthwash on force decay and permanent deformation of elastomeric chain.

Effects of stress relaxation in beta-titanium cantilevers used in orthodontic mechanics

ABSTRACT Objective: This study evaluated the force decay and design shape changes caused by stress relaxation in two different orthodontic cantilever configurations. Methods: Eighty cantilevers made of 0.017 x 0.025-in beta-titanium wires were standardized in a passive position, using real scale templates, and randomly divided into two groups (n = 40): Type 1 and Type 2. Each group received a different design (Type 1 with three bends, and Type 2 with two bends), and both were divided in four subgroups (n = 10) according to the evaluation periods: G1 = 24h, G2 = 1 week, G3 = 4 weeks, and G4 = 8 weeks. Mechanical tests were performed immediately after preactivation and at the end of each period, to evaluate force decay. The cantilevers were also scanned and the angles of the bends were measured to assess shape changes. Results: Cantilever forces decayed over time. Type 1 - G1 showed less force decay than Type 2 (10.83 cN vs 17.87 cN). Type 1 cantilevers showed significant force decay only when G4 was compared to G1 (9.05 cN), G2 (11.73 cN), and G3 (9.78 cN). Type 2 cantilevers presented differences when G1 was compared to G2 (9.57 cN) and G3 (7.89 cN). Regarding to the cantilever angle closest to the bracket insertion, Type 1 cantilevers showed significant decrease for G2 (1.58°) and G4 (1.52°). Conclusions: Cantilevers’ design and proximity of the bends influenced force decay pattern overtime. Type 1 cantilevers presented more stable design at the first weeks than Type 2.

Generation I and Generation II Elastomeric Chains Characteristics Comparison in Artificial Saliva Immersion

Objective: To determine the force decay and discoloration in Generation I and Generation II elastomeric chain on artificial saliva immersion. Material and methods: Generation I and Generation II elastomeric chains stretched on an acrylic board and immersed in artificial saliva for 1, 7, 14, 21, and 28 days according to the group of days. On each specified day, the force of each sample measured by an orthodontic force gauge and the magnitude of the force obtained is entered to the formula to find out the force decay in percentage, whereas discoloration of each sample analyzed by the color reader with CIE Lab analysis. Results: The force decay between Generation I and Generation II elastomeric chains showed a statistically significant difference in every group of days, in which Generation II is more effective in maintaining stretch force. Similar to force decay, the discoloration in Generation I elastomeric chains on the 14th day showed significant value and Generation II elastomeric chains were more stable in maintaining color compared to Generation I. Conclusions: over the entire research period time, Generation II elastomeric chains are more stable in maintaining stretch forces and color compared to Generation I elastomeric chains. KEYWORDS Discoloration; Elastomeric chain; Force decay; Generation I; Generation II.