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Mouthwashes are used during dental treatments to mitigate the complications caused by poor oral hygiene. However, these solutions also affect the properties of dental appliances, including those used in orthodontics. This point has been investigated in this study focusing on the changes in mechanical properties of polymeric orthodontic ligature ties. Commercial ties from four brands were characterized in terms of their maximum forces and displacement, delivery forces, molecular structures, and microscopic morphology. These properties were compared against the ties, which were rinsed with commercial mouthwashes from three manufacturers. The results showed that mouthwash rinsing significantly reduced the maximum bearable forces of ligature ties by up to 73.1%, whereas the reduction in their maximum displacement was up to 74.5% across all tested brands. Significant changes in microscopic morphology of ligature ties were observed after mouthwash rinsing, but not their molecular structure. Furthermore, mouthwash rinsing also reduced the delivery forces from ligature ties by between 20.9 and 32.9% at their first deformation cycle. It can be concluded from this study that mouthwashes have significant impact on the mechanical properties of polymeric orthodontic ligature ties and could also potentially affect the overall efficacy of orthodontic and other dental treatments.

This study aims to investigate mechanical properties and transformation behavior of TiNiCu shape memory alloys to obtain optimal conditions for utilizing as orthodontic wires. TiNi binary alloys with Ni-content 50.6 at.%, TiNiCu alloys with Cu-content ranging from 5 to 10 at.% were prepared. The alloys were melted by electrical arc-melting method and then homogenized at 800°C for 3600 s. The alloys were subsequently sliced into thin plates (1.5 mm) by EDM wire cutting machine. To evaluate mechanical properties, the specimens were cold-rolled with 10, 20 and 30%, followed by heat treatment at 400°C and 600°C for 3600 s, respectively. A Differential Scanning Calorimeter (DSC) was used to detect transformation temperatures. Mechanical properties were evaluated by micro hardness and three-point bending tests. The results showed that transformation temperatures were strongly increased with increasing Ni-content. Moreover, the decrease in transformation temperature after increasing level of cold-rolling reduction ratio suggests that internal stress can depress transformation. However, internal stress seemed to support the introduction of superelasticity for each specimen. In addition, specimens heat treated at 400°C have, more appropriate properties as orthodontic wires than those heat-treated at 600°C due to the remaining effect of cold-working. These results can be take into consideration for optimizing alloy composition and mechanical properties of TiNiCu shape memory alloys for orthodontics wires purposes.

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The aim of this study is to investigate effect of Cu and Co additions on corrosion behavior of NiTi shape memory alloys for orthodontic application. Ni50.6Ti49.4, Ti49Ni46Cu5 and Ti50Ni47Co3 (at%) alloys were prepared. The specimens were melted by arc-melting furnace and homogenized at 800oC for 3.6 ks. Transformation temperatures were analyzed by differential scanning calorimeter (DSC). The corrosion behavior was assessed electrochemically in artificial saliva (pH 5.35) at 37oC. Open circuit potential (OCP) was monitored 3.6 ks followed by potentiodynamic techniques. The results show that all of specimens revealed transformation temperature close to oral temperature which may be utilized as orthodontic wire. Surface roughness was measured in order to ensure that there is no significant difference which might affect corrosion resistance. It is seen that by adding Co and Cu into NiTi alloys, the corrosion potential (Ecorr) and pitting corrosion potential (Ebreak) increase resulting in lower corrosion rate. Conceivably, Co and Cu additions considerable affect the corrosion behavior of NiTi alloys by improving corrosion resistance in artificial saliva.