• The korean journal of orthodontics
• /
• v.33 no.6 s.101
• /
• pp.465-474
• /
• 2003

The great variety of commercial brands of orthodontic wires available on the market, stimulated by the so called superior wires (nickel titanium with shape memory effect and superelastic nickel titanium), makes the professional choice for a suitable and less expensive material difficult. The in vitro study of the mechanical properties of the orthodontic wires acts as an auxiliary tool for the professional. In this paper, a comparative study of mechanical properties was made, using stress strain tests for 4 types of orthodontic wires (conventional stainless steel, multistranded steel, superelastic nickel titanium and thermoactivated nickel titanium) separated into 5 groups. A series of 6 tests were tested for each group of wires. Initially, each group was tested 3 times until the wires broke. Furthermore, 3 more tests for each group were performed, stretching the wires under standardized activation loads, for a reliable comparison of their mechanical properties, during loading and unloading. 1 tests were applied to check differences among the groups. In vitro, the results suggest that regarding the mechanical properties supposedly desirable for physiological teeth movement, such as resilience, elasticity modulus, strength liberated during unloading, and the way that strength is liberated, thermoactivated nickel titanium wires, acting under mouth temperature, seems to be a good choice, fellowed by superelastic nickel titanium, multistranded stainless steel, and conventional stainless sleet. Superelasticity was demonstrated for superelastic nickel titanium wires. When at $37^{\circ}C$, thermoactivated nickel titanium wires showed shape memory effect, showing that temperature is important for enhancing the mechanical properties.

• The korean journal of orthodontics
• /
• v.36 no.5
• /
• pp.349-359
• /
• 2006

Objective: Nickel-titanium alloy wire possesses excellent spring-back properties, shape memory and super-elasticity. In order to adapt this wire to clinical use, it is necessary to bend as well as to control its super-elastic force. The purpose of this study is to evaluate the effects of heat treatment on the load-deflection properties and transitional temperature range (TTR) of nickel-titanium wires. Methods: Nickel-titanium wires of different diameters ($0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ and $0.0215"\;{\times}\;0.028"$) were used. The samples were divided into 4 groups as follows: group 4, posterior segment of archwire (24 mm) without heat treatment; group 2, posterior segment of archwire (24 mm) with heat treatment only; group 3, anterior segment with bending and heat treatment; group 4, anterior segment with bending and 1 sec over heat treatment. Three point bending test was used to evaluate the change in load-deflection curve and obtained DSC (different scanning calorimetry) to check changes in $A_f$ temperature. Results: In the three point bending test, nickel-titanium wires with heat treatment only had higher load-deflection curve and loading and unloading plateau than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment had lower Af temperature than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment and bending had higher load-deflection curve than nickel- titanium wires with heat treatment and nickel-titanium wires without heat treatment. Nickel-titanium with heat treatment of over 1 sec and bending had the highest load-deflection curve. Nickel-titanium wires with heat treatment and bending had lower Af temperature, Nickel-titanium wires with heat treatment of over Af sec and bending had the lowest Af temperature. Conclusion: From the results of this study, it can be stated that heat treatment for bending of Nickel-titanium wires does not deprive the superelastic property but can cause increased force magnitude due to a higher load-deflection curve.

• The korean journal of orthodontics
• /
• v.54 no.1
• /
• pp.16-25
• /
• 2024

Objective: To compare the effectiveness of laser-engineered copper-nickel titanium (SmartArch) and superelastic nickel-titanium (SENT) archwires in aligning teeth and inducing root resorption and pain experienced by patients. Methods: Two-arm parallel groups with a 1:1 allocation ratio were used. The participants were patients aged 11.5 years and older with 5-9 mm of mandibular anterior crowding who were indicated for non-extraction treatment. The primary outcome was alignment effectiveness, assessed using Little's irregularity index (LII) over 16 weeks with a single wire (0.016-inch) in the SmartArch group and 2 wires (0.014- and 0.018-inch) in the SENT group (8 weeks each). Secondary outcomes included root resorption evaluated by pre- and post-intervention periapical radiographs and pain levels recorded by the participants during the first week. Results: A total of 40 participants were randomly allocated into 2 groups; 33 completed the study and were analyzed (16 in the SmartArch group and 17 in the SENT group, aged 16.97 ± 4.05 years). The total LII decrease for the SmartArch and SENT groups was 5.63 mm and 5.29 mm, respectively, which was neither statistically nor clinically significant. Root resorption was not significantly different between the groups. The difference in pain levels was not statistically significant for the first 5 days following wire placement; however, there was a significant difference favoring the SENT group in the final 2 days. Conclusions: SmartArch and SENT archwires were similarly effective during the alignment phase of orthodontic treatment. Root resorption should be observed throughout the treatment with either wire. SmartArch wires demonstrated higher pain perception than SENT wires.

• The korean journal of orthodontics
• /
• v.30 no.4 s.81
• /
• pp.453-465
• /
• 2000

The purpose of this study was to investigate the change of mechanical properties, surface topography and frictional force of various nickel titanium wires after recycling. Three types of nickel-titanium wires and one type of stainless steel wire were divided to three groups: as-received condition(T0:control group), treated in artificial saliva for four weeks(T1) and autoclaved after being treated in artificial saliva(T2). Some changes were observed for the selected mechanical properties in tensile test, surface topography by means of SEM and 3D profilogram, and frictional coefficient. The findings suggest that: 1. Nickel-titanium wires demonstrated no statistically significant differences in maximum tensile strength, elongation rate and modulus of elasticity, but stainless steel wire demonstrated statistically significant differences in maximum tensile strength, elongation rate and modulus of elasticity between the groups(p<0.05). 2. NiTi, Optimalloy, Stainless Steel wires demonstrated increased pitting and corrosion in SEM finding. 3. Recycled NiTi, Optimalloy and stainless steel wires demonstrated significantly greater surface roughness(Ra and Rq) through 3D profilogram when compared with the control wires(p<0.05), but Sentalloy didn't demonstrate significant difference. 4. Recycled NiTi, Optimalloy and stainless steel wires demonstrated significantly greater maximum frictional coefficient when compared with the control wires(p<0.05), but Sentalloy didn't demonstrate significant difference The changes of surface roughness and frictional coefficient in NiTi and Optimalloy had no clinical implication. Consequently recycled nickel titanium wires demonstrated no clinical problem in tensile properties, surface topography and frictional coefficient.

• The korean journal of orthodontics
• /
• v.37 no.2 s.121
• /
• pp.137-149
• /
• 2007

Objective: The purpose of this study was to compare changes in frictional resistance between the bracket and wire under dry and wet conditions according to a change in moment. Methods: A stainless steel bracket of $0.022"{\times}0.028"$ slot, and $0.019"{\times}0.025"$ stainless steel, beta-titanium, and nickel-titanium wires were used. A 10 mm length lever was attached to the test (sliding) brackets to generate a moment. The experimental model was designed to allow tipping until contacts were established between the wire and the mesiodistal edges of the bracket slot. The moment was generated by suspending a 100 g or 200 g weight on the end of the lever. The moments applied were $1000g{\cdot}mm\;(100g{\times}10mm)\;and\;2000g{\cdot}mm\;(200g{\times}10mm)$. The test brackets were ligated with elastomeric ligature for a constant ligation force and the fixed brackets were ligated with stainless steel ligature. Brackets were moved along the wire by means of an universal testing machine, and maximum frictional resistances were recorded. Results: Stainless steel wire showed least frictional resistance and there was no significant difference between beta-titanium and nickel-titanium except at $2000g{\cdot}mm$ moment in wet conditions. Frictional resistance of all wires increased as the moment increased from $1000g{\cdot}mm\;to\;2000g{\cdot}mm$. Under wet conditions, the frictional resistance of stainless steel wires increased in both $1000g{\cdot}mm\;and\;2000g{\cdot}mm$ moment conditions, but frictional resistance of nickel-titanium and beta-titanium increased only in $2000g{\cdot}mm$ conditions. Conclusion: These results indicated that various conditions influence on frictional resistance. Therefore, laboratory studies of frictional resistance should simulate clinical situation.

• The korean journal of orthodontics
• /
• v.48 no.3
• /
• pp.153-162
• /
• 2018

Objective: The aim of this trial was to compare the alignment efficiency and intermaxillary arch dimension changes of nickel-titanium (NiTi) or copper-nickel-titanium (CuNiTi) round archwires with increasing diameters applied sequentially to the mandibular arch. Methods: The initial alignment phase of fixed orthodontic treatment with NiTi or CuNiTi round archwires was studied in a randomly allocated sample of 66 patients. The NiTi group comprised 26 women, 10 men, and the CuNiTi ($27^{\circ}C$) group comprised 20 women, 10 men. The eligibility criteria were as follows: anterior mandibular crowding of minimum 6 mm according to Little's Irregularity Index (LII), treatment requiring no extraction of premolars, 12 to 18 years of age, permanent dentition, skeletal and dental Class I malocclusion. The main outcome measure was the alignment of the mandibular anterior dentition; the secondary outcome measure was the change in mandibular dental arch dimensions during 12 weeks. Simple randomization (allocation ratio 1:1) was used in this single-blind study. LII and mandibular arch dimensions were measured on three-dimensional digital dental models at 2-week intervals. Results: No statistically significant difference was observed between NiTi and CuNiTi according to LII (p > 0.05). Intercanine and intermolar arch perimeters increased in the CuNiTi group (p < 0.001). Inter-first premolar width showed a statistically significant interaction in week ${\times}$ diameter ${\times}$ application (p < 0.05). Conclusions: The effects of NiTi and CuNiTi round archwires were similar in terms of their alignment efficiency. However, the intercanine and intermolar arch perimeters, and the inter-first premolar width changes differed between groups.

• The korean journal of orthodontics
• /
• v.47 no.4
• /
• pp.268-274
• /
• 2017

The purpose of this article is to introduce a simple appliance that uses a setup model and a nickel-titanium (Ni-Ti) wire for correcting the mesial rotation and drift of the permanent maxillary first molar. The technique involves bonding a Ni-Ti wire to the proper position of the target tooth on a setup model, followed by the fabrication of the transfer cap for indirect bonding and its transfer to the patient's teeth. This appliance causes less discomfort and provides better oral hygiene for the patients than do conventional appliances such as the bracket, pendulum, and distal jet. The treatment time is also shorter with the new appliance than with full-fixed appliances. Moreover, the applicability of the new appliance can be expanded to many cases by using screws or splinting with adjacent teeth to improve anchorage.

• The korean journal of orthodontics
• /
• v.44 no.5
• /
• pp.236-245
• /
• 2014

Objective: To evaluate the therapeutic effects of a preformed assembly of nickel-titanium (NiTi) and stainless steel (SS) archwires (preformed C-wire) combined with temporary skeletal anchorage devices (TSADs) as the sole source of anchorage and to compare these effects with those of a SS version of C-wire (conventional C-wire) for en-masse retraction. Methods: Thirty-one adult female patients with skeletal Class I or II dentoalveolar protrusion, mild-to-moderate anterior crowding (3.0-6.0 mm), and stable Class I posterior occlusion were divided into conventional (n = 15) and preformed (n = 16) C-wire groups. All subjects underwent first premolar extractions and en-masse retraction with preadjusted edgewise anterior brackets, the assigned C-wire, and maxillary C-tubes or C-implants; bonded mesh-tube appliances were used in the mandibular dentition. Differences in pretreatment and post-retraction measurements of skeletal, dental, and soft-tissue cephalometric variables were statistically analyzed. Results: Both groups showed full retraction of the maxillary anterior teeth by controlled tipping and space closure without altered posterior occlusion. However, the preformed C-wire group had a shorter retraction period (by 3.2 months). Furthermore, the maxillary molars in this group showed no significant mesialization, mesial tipping, or extrusion; some mesialization and mesial tipping occurred in the conventional C-wire group. Conclusions: Preformed C-wires combined with maxillary TSADs enable simultaneous leveling and space closure from the beginning of the treatment without maxillary posterior bonding. This allows for faster treatment of dentoalveolar protrusion without unwanted side effects, when compared with conventional C-wire, evidencing its clinical expediency.

• The korean journal of orthodontics
• /
• v.28 no.6 s.71
• /
• pp.927-935
• /
• 1998

The purpose of this study is to investigate the changes of mechanical properties and surface topography of various nickel titanium wires after heat sterilization for recycling with quantitative method. The materials used were four kinds of nickel titanium orthodontic wires including a Korean product. Experimental specimens were treated with two kinds of heat sterilization methods ; dry heat ($180^{\circ}C$, 60min) and autoclave ($121^{\circ}C$, 15-20psi, 30min). Mechanical properties were evaluated by tensile test with Instron 4466 (load cell capacity:.1000 kg, cross head speed:5mm/min, grip distince:40mm in room temperature). Surface topography of various wires was compared with each other qualitatively by using scanning electron microscopy and quantitatively by using profilometer. The findings were analyzed statistically with student t-tests. The results were as follows; 1. Neither method of heat sterilization had any effects on tensile properties of the nickel-titanium wires used in this experiment. 2. Before heat sterilization, the surface smoothness was highest in Optimalloy, followed by Align and Sentalloy, with NiTi showing the lowest smoothness value. 3. In surface topography, Align and Optimalloy were not influenced by heat sterilization. NiTi, on the other hand, had increased roughness after dry heat sterilization and Sentalloy showed the same tendency after each of the two heat sterilization procedures.

• Restorative Dentistry and Endodontics
• /
• v.42 no.4
• /
• pp.301-308
• /
• 2017

Objectives: It was aimed to compare the cyclic fatigue resistances of ProTaper Universal (PTU), ProTaper Next (PTN), and ProTaper Gold (PTG) and the effects of sterilization by autoclave on the cyclic fatigue life of nickel-titanium (NiTi) instruments. Materials and Methods: Eighty PTU, 80 PTN, and 80 PTG were included to the present study. Files were tested in a simulated canal. Each brand of the NiTi files were divided into 4 subgroups: group 1, as received condition; group 2, pre-sterilized instruments exposed to 10 times sterilization by autoclave; group 3, instruments tested were sterilized after being exposed to 25%, 50%, and 75% of the mean cycles to failure, then cycled fatigue test was performed; group 4, instruments exposed to the same experiment with group 3 without sterilization. The number of cycles to failure (NCF) was calculated. The data was statistically analyzed by using one-way analysis of variance and post hoc Tukey tests. Results: PTG showed significantly higher NCF than PTU and PTN in group 1 (p < 0.05). Sterilization significantly increased the NCF of PTN and PTG (p < 0.05) in group 2. PTN in group 3 had significantly higher cyclic fatigue resistance than PTN group 4 (p < 0.05). Also, significantly higher NCF was observed for PTG in group 2 than in groups 3 and 4 (p < 0.05). Conclusions: PTG instrument made of new gold alloy was more resistant to fatigue failure than PTN and PTU. Autoclaving increased the cyclic fatigue resistances of PTN and PTG.