Salt Heat Treatment and Passivation to Improve the Corrosion Resistance of Nitinol (Ni-Ti)

Corrosion of nitinol (NiTi) is a major factor in the failure of implantable materials. Recently, as the importance of corrosion of metals has increased, testing according to international guidelines is essential. The purpose of this study was to evaluate the corrosion resistance of NiTi wire through heat treatment and passivation process. In this study, NiTi wire used two commercially available products and a self-manufactured stent. Experimental consideration was carried out according to ASTM standards. Heat treatment was carried out in an air or a salt furnace, and the corrosion was measured after additional process, such as passivation and scratch tests. As a result, the metal potential was rapidly decreased in the air furnace group. On the other hand, the potential of wires was dramatically increased in the salt furnace group compared to the air furnace group. The dislocation decreased below the acceptance criteria (>600 mV) within 60 s of heat treatment time in the air furnace. Moreover, the potential was dramatically improved, even after only 20 min of passivation treatment (1076 mV, 442% compared to the non-passivated group), and it continued to rise until 180 min. This phenomenon was similarly observed in the group of self-manufactured stents. The potential slightly decreased by the scratch process (93.1%) was significantly reduced by the air furnace process (315 mV, 24.4% of the nontreated group). In the passivated group of the air furnace sample with reduced potential, the potential was restored to the level before the air furnace (scratch stage) (1032 mV). In conclusion, the heat treatment is preferably carried out in a salt furnace rather than an air furnace, and the passivation process can be an advantageous tool to improve corrosion resistance by suppressing the oxidation process.

Softening Effects in Biological Tissues and NiTi Knitwear during Cyclic Loading

Samples of skin, tendons, muscles, and knitwear composed of NiTi wire are studied by uniaxial cyclic tension and stretching to rupture. The metal knitted mesh behaves similar to a superelastic material when stretched, similar to soft biological tissues. The superelasticity effect was found in NiTi wire, but not in the mesh composed of it. A softening effect similar to biological tissues is observed during the cyclic stretching of the mesh. The mechanical behavior of the NiTi mesh is similar to the biomechanical behavior of biological tissues. The discovered superelastic effects allow developing criteria for the selection and evaluation of mesh materials composed of titanium nickelide for soft tissue reconstructive surgery.

Influence of Physical Dimension and Morphological-Dependent Antibacterial Characteristics of ZnO Nanoparticles Coated on Orthodontic NiTi Wires

White spot lesions (WSLs) are one of the adverse effects of fixed orthodontic treatments. They are the primary sign of caries, which means inhibiting this process by antibacterial agents will reverse the procedure. The current study tested the surface modification of nickel-titanium (NiTi) wires with ZnO nanoparticles (NPs), as antimicrobial agents. As the morphology of NPs is one of the most critical factors for their properties, the antibacterial properties of different morphologies of ZnO nanostructures coated on the NiTi wire were investigated. For the preparation of ZnO nanostructures, five coating methods, including chemical vapor deposition (CVD), chemical precipitation method, polymer composite coating, sol-gel synthesis, and electrospinning process, were used. The antibacterial activity of NPs was assessed against Streptococcus mutans by the colony counting method. The obtained results showed that all the samples had antibacterial effects. The antibacterial properties of ZnO NPs were significantly improved when the specific surface area of particles increased, by the ZnO nanocrystals prepared via the CVD coating method.

Correction of persistent crowding in the lower anterior region: A case report

Aim: This case report demonstrates the application of piezocision in correcting persistent crowding in the lower anterior region of dental arch. Methodology: A female aged 14 years and 3 months presented to the Selcuk University Department of Orthodontics due to aesthetic complaints. Clinical and radiological examination revealed crowding in the upper and lower dental arches as well as skeletal and dental Class I malocclusion. First, bonding and arch wire were applied to the patient’s upper jaw. The patient then had check-up appointments at 4-week intervals. In the second session, bonding was applied to the lower jaw. As the leveling was completed in the upper jaw, thicker arch wires were used. However, 4 months after the bonding of the lower anterior region, leveling did not occur. Consequently, piezocision was applied to the lower anterior region. Then, two applications of 0.014'' and 0.016'' NiTi wire were carried out, respectively. After the completion of the leveling, intrusion was provided with the utility arch placed on the lower incisor brackets. Orthodontic treatment was concluded with the use of NiTi and steel angle wires. Conclusion: Efficient leveling was achieved in the lower anterior region with piezocision applications. How to cite this article: Cime Akbaydogan L, Baka ZM, Uulusoy Mutluol E. Correction of persistent crowding in the lower anterior region: A case report. Int Dent Res 2021;11(Suppl.1):303-7. https://doi.org/10.5577/intdentres.2021.vol11.suppl1.45 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Bacterial Biofilm Growth on Various Dental Stabilization Systems for Avulsed and Luxated Teeth

With the increased incidence of traumatic injuries and the advanced understanding of the periodontal and alveolar healing process, teeth splinting has become a common practice for stabilizing traumatized teeth. Consequently, several splinting materials and techniques have been introduced in the past few years. Despite the detrimental role of bacterial biofilm on healing, the level of biofilm development on these material surfaces has not been well investigated. Bacterial biofilms are severely detrimental for periodontal healing of avulsed and luxated teeth. Thus, biofilm growth becomes a critical factor in selecting the material of choice for dental splints. In this study, we aim to assess the level of oral biofilm growth on four different splinting systems: Ribbond©, orthodontic NiTi wire, monofilament fishing line, and Titanium Trauma Splint. A total of 72 extracted anterior teeth were divided into four groups. We splinted six rows of three teeth each per group. The teeth selected were caries-free and periodontitis-free at the time of extraction. To assess biofilm growth, a supragingival dental plaque sample was cultured and directly inoculated into all groups. After 7 days, bacterial growth was quantified by live/dead fluorescent microscopy assay and colony forming unit counts (CFU). Using one-way ANOVA and Bonferroni’s post hoc tests, we demonstrated that all splint systems allowed for bacterial growth. However, the Titanium Trauma Splint (TTS) allowed for the least amount of biofilm growth compared to other splint systems.

Simulation of superelastic NiTi wire force application on orthodontic alignment case

Nickel Titanium (NiTi) orthodontic wires are the most accurate initial wires to align the teeth by producing the less painful bone remodeling. Coupling their mechanical response, while they are engaged in the oral cavity, with the bone remodeling would permit to elucidate the reaction and the effect of this wire during the orthodontic tooth alignment. Therefore, A two-dimensional numerical long-term orthodontic tooth correction was performed to simulate a tooth intrusion movement. This simulation was achieved by taking into consideration the effect of an orthodontic appliance action on three multiteeth models. The superelastic behavior of the NiTi wire was integrated in the computer software ABAQUS via a UMAT subroutine. The orthodontic arch was initially deformed to simulate its insertion in brackets and then unloaded to apply an orthodontic load and produce initial tooth displacement. A bone remodeling process was implemented to displace the teeth depending on the strain within the periodontal ligament. The results were obtained for a treatment period of 30 days. The NiTi wire was able to recuperate its initial position, and the teeth were aligned. The numerical results of the teeth displacement were in agreement with what is expected to be produced during the alignment phase.

Comparison of rotary NiTi reciprocating file systems using Cone Beam CT in root canal transportation

Aim: T assess the root canal transportation caused by these rotary NiTi reciprocating file systems using 3D cone beam computed tomography Method: This experimental study was conducted on 60 samples of rotary NiTi reciprocating file systems using CBCT. The extent of canal transportation and the centering ratio was analyzed using independent sample t test. The significance level was set at 95%. Results: Mean apical canal transportation was lower in wave one Gold groups as compare to Reciproc (0.8724±0.04SD vs 0.9463±0.02SD, p=0.000). Mean apical canal transportation at 5 mm was lower in wave one gold group as compare to reciproc blue group (0.5610±0.02SD vs 0.7253±0.06SD, p=0.000). Mean apical canal transportation at 8mm was lower in wave one group as compare to reciproc blue (0.358±0.03SD vs 0.5766±0.10SD, p=0.000). Conclusion: Wave one Gold had high centering ability and lower canal transportation as compare to Reciproc Blue single file system. CBCT is an efficient method of understanding Canal transportation Keywords: CBCT, NiTi wire, Root canal transportation, Reciproc blue

Microtomography Evaluation of The Efficacy of Reciprocating And Rotary Instruments Followed By Different Complementary Steps In The Retreatment of Curved Root Canals

Objectives: The purpose of this study was to evaluate the efficacy of steps, isolated or in cumulative means, in the endodontic retreatment of curved canals. Methodology: Forty mesial roots of mandibular molars were divided into two groups. In the group 1 the filling removal was done with NiTi reciprocating M-wire and NiTi control memory wire rotary instruments followed by a passive ultrasonic irrigation solution agitation. In the group 2, the initial filling removal was done with NiTi reciprocating M-wire and conventional NiTi wire rotary instruments followed by a rotary plastic instrument for irrigation solution agitation. The results were analyzed through micro-computed tomography. Results: The filling material was not completely removed for both groups. All steps did not statically differ between groups regarding to the filling removal. In the intragroup analyses, the results differed in some levels, mainly in the apical level, but did not statistically differ in all the different levels after each step. A statistical significant increase (P<.05), for both groups, in the volume of filling material in the isthmus was observed. Conclusions: None of the protocols completely removed the filling material. The better results were found for the apical level and after passive ultrasonic irrigation. Vertical warm condensation filling technique enhanced the volume of filling material in the root canal system including the isthmus. Clinical relevance: the control memory NiTi instruments could be considered a good choice for use as an additional step in the procedure of filling removal from curved mesial root canals.