Superelastic Nickel-titanium Archwires Research Articles

Comparison of alignment efficiency of different sizes of superelastic nickel-titanium archwires in the initial phase of fixed orthodontic treatment: A single-center, double-blind randomized clinical trial

Comparison of alignment efficiency of different sizes of superelastic nickel-titanium archwires in the initial phase of fixed orthodontic treatment: A single-center, double-blind randomized clinical trial

Optimizing ageing conditions for commercial NiTi archwires: Insights from thermal phase transformation and tensile deformation analysis

Superelastic nickel-titanium (NiTi) archwires are now commonly used as the standard archwire during the orthodontic alignment and levelling stage. They are preferred due to their ability to apply minimal force on teeth while allowing for a wide range of tooth movements. During orthodontic treatment, the orthodontist assesses the dimension and shape of the NiTi archwire to determine the amount and direction of force required to align misaligned teeth. The main contribution of this study is the parametric analysis and establishment of a set of optimal ageing temperatures and duration for the investigation of functionally graded nickel-titanium archwire using differential scanning calorimetry (DSC) and tensile deformation testing. The mechanical and thermal phase transformation behavior after ageing at six temperatures for duration of 15 minutes have been investigated using tensile deformation test and differential scanning calorimetry (DSC) test in this paper. Experimental results reveal that in thermal analysis as the ageing temperatures increase from 400 °C to 490 °C, the austenite finish temperature rises to a value between 9.53 °C and 35.48 °C, and subsequently decreases to 520 °C. The archwire specimen aged for temperature of 490 °C exhibited the austenite finish temperature of around 35.48 °C, and it is highest among the aged wire specimens closest to oral temperature. In tensile deformation, the ideal ageing temperature for orthodontic applications was determined to be 490 °C for 15 minutes, resulting in relatively low plateau slope 13.73 GPa with high superelatic ratio 12.04, and maximum plateau strain of 7 %.

Uprighting horizontally impacted third molars by super-elastic nickel-titanium wire in patients with an extracted first molar.

Protracting lower second molars and uprighting horizontally impacted third molars is a significant orthodontic challenge in patients who require the extraction of severely decayed first molars. Here, we describe the use of biomechanics to upright 90°-tilted lower third molars following second molar protraction. Herein, we introduce a technique for uprighting the lower third molars by (1) the placement of superelastic nickel titanium archwires, (2) bonding, and (3) repositioning of a buccal tube in a tilted position to compensate for the efficiency of Ni-Ti (nickel-titanium) wire. The treatment mechanics used for our two cases showed that even severely impacted third molars can be uprighted by routine continuous straight-wire techniques. This technique proved to be a simple, efficient and reliable treatment option for uprighting horizontally impacted third molars.

Effectiveness of laser-engineered copper-nickel titanium versus superelastic nickel-titanium aligning archwires: A randomized clinical trial.

: 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. : 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. : 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. : 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.

Thermal Programming of Commercially Available Orthodontic NiTi Archwires.

The shape of superelastic Nickel-Titanium (NiTi) archwires can be adjusted with thermal treatments using devices such as the Memory-MakerTM (Forestadent), which potentially affects their mechanical properties. The effect of such treatments on these mechanical properties was simulated by means of a laboratory furnace. Fourteen commercially available NiTi wires (0.018″ × 0.025″) were selected from the manufacturers American Orthodontics, Dentaurum, Forestadent, GAC, Ormco, Rocky Mountain Orthodontics and 3M Unitek. Specimens were heat treated using different combinations of annealing duration (1/5/10 min) and annealing temperature (250-800 °C) and investigated using angle measurements and three-point bending tests. Complete shape adaptation was found at distinct annealing durations/temperatures for each wire ranging between ~650-750 °C (1 min), ~550-700 °C (5 min) and ~450-650 °C (10 min), followed by a loss of superelastic properties shortly afterwards at ~750 °C (1 min), ~600-650 °C (5 min) and ~550-600 °C (10 min). Wire-specific working ranges (complete shaping without loss of superelasticity) were defined and a numerical score (e.g., stable forces) was developed for the three-point bending test. Overall, the wires Titanol Superelastic (Forestadent), Tensic (Dentaurum), FLI CuNiTi27 (Rocky Mountain Orthodontics) and Nitinol Classic (3M Unitek) proved to be the most user-friendly. Thermal shape adjustment requires wire-specific working ranges to allow complete shape acceptance and high scores in bending test performance to ensure permanence of the superelastic behaviour.

Effects of wearing fixed orthodontic appliance on dynamic balance, reaction time, and pain perception in adolescents and young adult elite athletes

ABTRACT Objective To investigate the effects of using fixed orthodontic appliance on dynamic balance, auditory/visual reaction times, as well as pain perception in adolescent and young adult elite athletes. Methods A total of 34 elite athletes (n = 19 males) aged 16–21 years from different sports (track and field sprint, long jump and discus throw) were randomly allocated to treatment (n = 17) or control (n = 17) groups. The treatment group received self-ligating brackets with 0.04 cm super-elastic nickel-titanium arch wire, placed in the brackets to correct the teeth position. Perceived pain (i.e., visual analogue scale), dynamic balance (i.e., Y balance test), and auditory reaction time and visual reaction time using Direct RT software were assessed before (day−1), and on five occasions after fixed orthodontic appliance placement (day+1, +3, +7, +14, and +30). The two groups’ quantitative data [expressed as mean (standard deviation)] for each occasion were compared using the Student’s t-test. Comparisons of the Y-balance test, auditory reaction time, visual reaction time, and pain visual analogue scale data were each made between the 6 occasions via a factorial A × B analysis of variance in order to check for the possible interaction between the two groups and the (6) consecutive days (occasions). Results Compared to the control group, the treatment group showed significantly (i) lower values of anterior reach for both the dominant ([78(4) vs. 75(3)%, respectively]) and the non-dominant [76(3) vs. 74(4)%, respectively] legs at day+3, and (ii) higher values of pain visual analogue scale at day+1, day+3, and day+7 [0.00(0.00) vs. 4.94(1.25); 0.00(0.00) vs. 4.12(1.17), and 0.00(0.00) vs. 0.41(0.51), respectively). Factorial analysis of variance revealed that only pain visual analogue scale values were different between the two groups at day+1 and day+3. Conclusion FOA induced a high pain level during the first week following its placement in elite athletes.

Alignment efficiency of heat activated and superelastic nickel-titanium archwires in orthodontic patients over three months: A Single-center, randomized clinical trial.

The aim of this 2-arm parallel study was to evaluate the alignment efficiency of heat-activated nickel-titanium (NiTi-TE) and superelastic nickel titanium (NiTi-PSE) archwires over the first 3 months of orthodontic treatment and compare these groups. Randomized, double-blind, controlled, single-center trial in 52 patients with fixed orthodontic appliances from an orthodontic graduate program in the permanent dentition and moderate crowding in the lower arch. Patients were randomly allocated to one of two interventions: NiTi-TE and NiTi-PSE archwires, 0.014-inch (3M Unitek™, CA, USA) with a follow-up period of 3 months. The primary outcome was the alignment efficiency determined by the reduction in Little's irregularity index (mm), measured in three points, T0: before the start of orthodontic treatment, T1: 1 month later, T2: 2 months later, T3: 3 months later. Data were analyzed using independent sample t tests and repeated measures ANOVA. 52 patients (NiTi-TE n = 26; NiTi-PSE n = 26) were randomized and analyzed (average age: 21.73; standard deviation (SD): 6.07; average lower anterior irregularity: 5.20; SD: 0.76) for intention-to-treat (ITT) analysis. No statistically significant differences between the groups were found (mean of the differences: T1: 0.20; 95% CI: -0.558; 0.958; T2: 0.49: 95% CI: -0.339; 1.319; T3: 0.33; 95% CI: -0.308; 0.968). The resolution of crowding with each of the wires was significant (P < 0.0001) at all times. Twelve participants (2 treated with NiTi-TE and 10 treated with NiTi-PSE) lost follow-up due to face-to-face dental-procedures restrictions during the COVID-19 pandemic, the missing data was imputed. NiTi-TE and NiTi-PSE wires of 0.014-inch were similar in their clinical efficiency for the resolution of crowding during the first 3 months of orthodontic treatment. Clinical Trials NCT03256279.

Salivary Electrolytes in Patients Undergoing Fixed Orthodontic Treatment

The base metal alloys are more susceptible to corrosion than nobl ealloys, and fixed orthodontic appliances are generally made of base alloys. Fixed orthodontic appliances in the oral cavity are exposed to destructive physical and chemical agents, resulting in metallic corrosion. The present study aimed to evaluate the concentration of cobalt, zinc, and magnesium in patients' saliva with fixed orthodontic appliances at three different times. Saliva samples from 18 patients (9 males and 9 females) between 15-25 years were taken at three different time points. Group I: Pretreatment saliva sample, group II: one month after appliance placement, Group III: four months after appliance placement. The fixed appliance consists of 20 stainless steel brackets, 4 buccal tubes, and a super elastic nickel-titanium arch wire. Inductively Coupled Plasma Optical Emission Spectrometry analyzed the level of ions in salivary samples. Ions are recorded in parts per billion. Statistical analysis was performed by non-parametric tests (Friedman) and one-way repeated measures ANOVA. Levels of cobalt, magnesium, and zinc ions in saliva were highest in group II, lowest in group I for both zinc and cobalt, and lowest in group III for magnesium. On a pair wise comparison between different groups, it was statistically significant for all groups (&lt;0. 005) except for cobalt and magnesium level between group I and group III and zinc level between groups II and III. Cobalt, magnesium, and zinc levels in saliva were increased after placing a fixed orthodontic appliance.

Frictional Resistance of Non Coated and Epoxy Coated Superelastic NiTi Wires used for Aligning in Three Types of Brackets

Introduction: Coated archwires are preferred in combination with aesthetic orthodontic brackets by orthodontists over non metallic aesthetic archwires. Studies evaluating the frictional properties of epoxy coated round superelastic Nickel Titanium (NiTi) archwires are limited to stainless steel brackets. Aim: To evaluate and compare the frictional resistance of an epoxy coated 0.016" superelastic NiTi archwire in stainless steel, composite and ceramic brackets and to compare it with the frictional resistance generated by non coated 0.016" superelastic NiTi archwire in same brackets. Materials and Methods: An in-vitro experimental study was conducted in the Department of Orthodontics at SRM Dental College from January to February 2020. Frictional resistance of 30 epoxy coated aesthetic 0.016" upper superelastic NiTi wires (G4™ Nickel Titanium, 0.016, Upper Trueform™ I, ToothColored) and 30 conventional 0.016" upper superelastic NiTi wires (G4™ Nickel Titanium, 0.016, Upper Trueform™) from G&amp;H® orthodontics while sliding across three different types of brackets were evaluated. Twenty stainless-steel (Gemini® 3M unitek, Monrovia, California), 20 composite (FLI® RMO, Denver, Colo.), and 20 gemini clear ceramic (Gemini clear ® 3M unitek, Monrovia, California) 0.022x0.028" Slot Roth prescription maxillary first premolar brackets were used. The brackets and archwires were divided into six groups of different bracket and archwire combination with 10 samples in each. An Instron testing machine with a 10 N tension was used to measure the frictional resistance. The obtained values were analysed using One-way ANOVA and followed by Post Hoc Tukey HSD for multiple comparison. Results: Coated wires generated significantly high friction in ceramic brackets (136.90±3.79 gms) followed by composite brackets (125.66±3.44 gms) and stainless steel brackets (92.53±8.70 gms). Non non coated wires generated significantly high friction with ceramic brackets (89.60±2.90 gms) whereas the friction generated in composite (70.87±5.79 gms) and stainless steel brackets (67.70±2.80 gms) was not significantly different. Conclusion: Epoxy coating increased the frictional resistance generated by the 0.016 superelastic NiTi archwires irrespective of bracket materials. The coated wires generated less friction in composite brackets compared to ceramic brackets. Further clinical trial are recommended to evaluate the aligning efficacy of these archwires in aesthetic brackets.

A clinical comparison of the effectiveness of two types of orthodontic aligning archwire materials: a multicentre randomized clinical trial.

To compare the heat-activated nickel titanium (HANT) with superelastic nickel-titanium (SENT) archwires in terms of their effectiveness of aligning teeth, possibility of inducing root resorption, and perception of pain. Orthodontic patients aged 12 years or over with mandibular anterior crowding of 3-6 mm, who required treatment without extractions were randomly allocated (a simple non-stratified randomization) to the HANT and SENT archwires groups with a 1:1 allocation ratio. The archwire sequence in both groups was 0.014-inch and 0.016-inch, respectively. Each archwire was placed for 4 weeks. The outcome measures included the amount of crowding assessed blindly using Little's irregularity index (LII), apical root resorption, and pain perception. The effectiveness of alignment was tested using 2 × 2 mixed factorial analysis of variance (ANOVA) model, while root resorption and pain perception were tested by the Mann-Whitney U-test and Wilcoxon signed-rank test (P < 0.05). Thirty-four patients were randomized and recruited from four centres, of those 31 were analysed (15 participants for the HANT and 16 for the SENT groups) with an overall mean age of 19.13 ± 5.73 years. The total reduction in the LII was 2.69 mm and 2.74 mm for the HANT and SENT groups, respectively. This did not reach the level of statistical (P = 0.809) or clinical significance. Similarly, root resorption and pain perception showed non-significant difference between groups. However, there was a slight increase in root resorption with the SENT group. A long-term evaluation of root resorption is required. Both HANT and SENT archwires were equally effective in the aligning stage of orthodontic treatment. Root resorption with SENT wires should be monitored throughout treatment. The trial was registered with ClinicalTrials.gov on 18 September 2019, registration number: NCT04090931.

A comparative assessment of clinical efficiency between premium heat-activated copper nickel-titanium and superelastic nickel-titanium archwires during initial orthodontic alignment in adolescents: a randomized clinical trial

BackgroundTo compare the clinical efficiency of premium heat-activated copper nickel-titanium (Tanzo Cu-NiTi) and NT3 superelastic NiTi during initial orthodontic alignment.Subject and methodsA total of 50 patients were randomly allocated to 1 of 2 different archwire types (group 1, Tanzo Cu-NiTi; group 2, NT3 superelastic NiTi). Eligibility criteria included Class I or Class II malocclusion, moderate maxillary anterior crowding, and healthy periodontal condition. Impressions of the upper arches were taken before archwire placement (T0) and at every 4 weeks (T1, T2, T3, and T4). For T1 and T2 stages, 0.014-in., and for T3 and T4 stages, 0.018-in. archwires were used. The primary outcome was the alignment efficiency assessed using Little’s irregularity index. The secondary outcomes were arch width and incisor inclination changes. Data were analyzed using independent samples t test, repeated measures ANOVA, and Mann-Whitney U test. Marginal models were established for the estimation of coefficients.ResultsThe anterior irregularity index reduction was mostly observed between T0 and T2 periods, which were respectively − 7.40 ± 0.50 mm (p < 0.001; 95% CI, − 8.94, − 5.85) and − 6.80 ± 0.55 mm (p < 0.001; 95% CI, − 8.49, − 5.12) for groups 1 and 2 (p < 0.001). With both wires, Little’s irregularity index decreased over time, and the difference between the groups was not significant (p = 0.581; estimated effect size, 0.011). No statistically significant difference was found between the groups in terms of intercanine and intermolar width and incisor inclination changes.ConclusionThere were no significant between-group differences in alignment efficiency, arch width, and incisor inclination change. There was an increased alignment with 0.014-in. compared with 0.018-in. diameter archwire.

Functional properties of superelastic orthodontic nickel-titanium archwires with protective titanium nitride coatings

Today there are many manufacturers of orthodontic archwires composed of a nickel-titanium (TiNi) alloy with different elastic-force characteristics. A limited number of orthodontic archwires is available for initial tooth alignment, since reactive stresses do not always satisfy the condition 160 ≤ σc ≤ 200 MPa. The use of orthodontic archwires with polymer coatings having better aesthetics is increasing. However, they show excessive wear and color change during a long-term orthodontic treatment. The aim of this paper is to study and optimize the functional characteristics of superelastic archwires composed of Ti-50.8 аР % Ni alloy with TiN coatings deposited at varying deposition times. A three-point bending test was carried out to evaluate the functional properties. The distance between the supporters was 10 mm. The archwires were subjected to bending at a temperature of 23 ± 3 °C. Each test was continued until deformation of 1.5; 3; 4.5 and 6 % was reached. It has been found that titanium nitride coatings deposited on the Ti-50.8 at. % Ni surface alloy by the vacuum-plasma method act as the barrier layer to prevent the release of nickel ions into biological environment. Heat treatment (~400 °C) during deposition allows the required elastic-force characteristics and functional properties of the material to form. The optimal reactive stress (160-200 MPa) and the reverse martensitic transformation temperature occurred near room temperature can be obtained due to an appropriate selection of the deposition parameters. In the martensitic phase at room temperature, the archwire can be deformed. When the archwire sample is placed in oral cavity and heated to temperatures above 30 °C the material is in the superelastic state. Further research is needed in terms of coating stability during deformation when the material in superelastic state, as well as conducting corrosion testing, studying biocompatibility of archwire samples with titanium nitride coatings in order to successfully implement the proposed technology in dental practice. The prototypes of orthodontic TiNi archwires with protective and decorative TiN coatings will be obtained for medical application.

Clinically relevant sample size calculations for trials.

An orthodontist attends the scientific orthodontic congress and passing by the company exhibitions receives a free sample of a novel orthodontic archwire introduced in the market for initial alignment/levelling with favourable performance over conventional superelastic nickel-titanium archwires. This novel archwire should increase according to the manufacturer’s claims alignment efficacy and halve the pain for the patient. After using the free sample wire on a patient and observing that the patient felt little to no pain during the alignment/levelling phase, the orthodontist decides to venture into unknown territory and find out if this holds true for most of her patients by doing a randomised clinical trial in her practice.

Assessment of Pain, Anxiety, and Cortisol Levels During the Initial Aligning Phase of Fixed Orthodontic Treatment.

We assessed pain and anxiety using psychological testing instruments (State-Trait Anxiety Inventory for Children, visual analog scale) and a physiological testing instrument (salivary cortisol hormone level) after the insertion of orthodontic appliances and during the initial alignment phase of orthodontic treatment. The study group involved two groups matched according to age and gender. Group 1 used 0.016-, 0.016×0.016-, and 0.16×0.22-inch and Group 2 used 0.014-, 0.016-, and 0.016×0.016-inch superelastic nickel-titanium archwires in the initial alignment phase of treatment. Pain and anxiety instruments were applied, and saliva samples were collected from the patients before and after molar band insertions, and bracket and initial archwire placement, and 7 days after the initial bonding and archwire replacements. Cortisol levels and state anxiety scores revealed statistically significant differences within groups (p<0.01, p<0.05). No significant differences were found between Group 1 and Group 2 in cortisol hormone levels, anxiety scores, or pain measurements (p>0.05). Although not statistically significant, the most severe pain was measured in the posterior teeth after band insertion and in the anterior teeth after the first archwire insertion (p>0.05). Orthodontic appliances and the initial alignment phase of orthodontic treatment affect patients' anxiety and cortisol hormone levels. Both archwires were equally effective with regard to perceived pain, anxiety, and stress hormone levels.

In-vitro investigation of the mechanical friction properties of a computer-aided design and computer-aided manufacturing lingual bracket system under diverse tooth displacement condition.

ObjectiveThe purpose of this study was to compare the static (SFF) and kinetic frictional forces (KFF) of a computer-aided design and computer-aided manufacturing lingual bracket (CAD/CAM-LB) with those of conventional LB (Con-LB) and Con-LB with narrow bracket width (Con-LB-NBW) under 3 tooth displacement conditions.MethodsThe samples were divided into 9 groups according to combinations of 3 LB types (CAD/CAM-LB [Incognito], Con-LB [7th Generation, 7G], and Con-LB-NBW [STb]) with 3 displacement conditions (no displacement [control], maxillary right lateral incisor with 1-mm palatal displacement [MXLI-PD], and maxillary right canine with 1-mm gingival displacement [MXC-GD]; n = 6/group). While drawing a 0.016-inch copper or super-elastic nickel-titanium archwire with 0.5 mm/min for 5 minutes in a chamber maintained at 36.5℃, SFF and KFF were measured. The Kruskal-Wallis method with Bonferroni correction was performed.ResultsThe Incognito group demonstrated the highest SFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD, Stb-MXC-GD] < [7G-MXC-GD, 7G-MXLI-PD, 7G-control] < [Incognito-MXLI-PD, Incognito-control, Incognito-MXC-GD]; p < 0.001). However, there were no significant differences in SFF among the 3 displacement conditions within each bracket group. Within each displacement condition, the Incognito group demonstrated the highest KFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD] < Stb-MXC-GD < 7G-MXLI-PD < [7G-control, 7G-MXC-GD] < [7G-MXC-GD, Incognito-MXLI-PD, Incognito-control] < [Incognito-control, Incognito-MXC-GD]; p < 0.001). MXC-GD exhibited higher KFFs than MXLI-PD in the same bracket group.ConclusionsThe slot design and ligation method of the CAD/CAM-LB system should be modified to reduce SFF and KFF during the leveling/alignment stage.

Evaluation of Salivary Nickel, Chromium and Iron Ions in Patients Treated with Fixed Orthodontic Appliances in Vivo Study

Background and objectives: Most fixed orthodontic appliances are made of stainless steel and Nickel-Titanium alloys, which can release metal ions into the oral cavity. The present study aimed to determine the release of Nickel, Chromium and Iron ions into saliva of patients treated with a fixed orthodontic appliance. Subjects and methods: Saliva samples from 18 patients (9 males and 9 females) between 15-25 years were taken at three different time points, group A: before placement of the appliance directly (baseline), group B: one month after appliance placement, Group C: four months after appliance placement. The fixed appliance consists of 20 stainless steel brackets, 4 buccal tubes, and superelastic Nickel-Titanium archwires. Level of ions in salivary samples was analyzed by Inductively Coupled Plasma Optical EmissionSpectrometry. Ions recorded in parts per billion. Statistical analysis was performed by nonparametric tests (Friedman) and one way repeated measures ANOVA. Results: Level of Nickel, Chromium and Iron ions in saliva were highest in group B and lowest in group A. on a pairwise comparison between different groups, it was statistically significant for all groups (< 0.05) except for Iron levels between group A and group C which was not statistically significant. Conclusion: Nickel, Chromium and Iron levels in saliva were increased after the placement of fixed orthodontic appliance.

Changes in mandibular border movements in adult patients after correction of functional anterior crossbite

Background/purposeAn effective approach for assessing masticatory function is necessary. The goal of this study was to establish an efficient method for evaluating mandibular border movements in patients after functional anterior crossbite was corrected. Materials and methodsFive patients with functional anterior crossbite were included in this study. They were treated with edgewise appliance and improved super-elastic nickel–titanium archwire. The digital images were collected before and after anterior crossbite was corrected. The trajectory paths of mandibular border movement were evaluated on both the frontal and sagittal planes. ResultsWhen the mandibular border movement paths were analyzed on the frontal plane for the vertical displacement, significant increases in the maximum left- and right-lateral movements were observed. For the horizontal displacement, although decreasing trends were observed in the maximum mouth opening and protrusive movements, no significant difference was detected. However, horizontal displacements were generally greater in men than in women. When the mandibular border movement paths were analyzed on the sagittal plane, significant increases in all the vertical and horizontal displacements were observed at all border movements, except the maximum mouth opening. However, if the data were compared between men and women, significant difference was shown only in the horizontal displacement of the maximum protrusion. ConclusionOn both the frontal and sagittal planes, after correction of the anterior crossbite there are increases in vertical and horizontal displacements at all kinds of mandibular border movements except for the horizontal displacements at the maximum mouth opening and the maximum protrusion.

Differences in cytocompatibility, dynamics of the oxide layers' formation, and nickel release between superelastic and thermo-activated nickel-titanium archwires.

Superelastic (SE) and thermo-activated (TA) nickel-titanium (NiTi) archwires are used in everyday orthodontic practice, based on their acceptable biocompatibility and well-defined shape memory properties. However, the differences in their surface microstructure and cytotoxicity have not been clearly defined, and the standard cytotoxicity tests are too robust to detect small differences in the cytotoxicity of these alloys, all of which can lead to unexpected adverse reactions in some patients. Therefore, we tested the hypothesis that the differences in manufacture and microstructure of commercially available SE and TA archwires may influence their biocompatibility. The archwires were studied as-received and after conditioning for 24h or 35days in a cell culture medium under static conditions. All of the tested archwires, including their conditioned medium (CM), were non-cytotoxic for L929 cells, but Rematitan SE (both as received and conditioned) induced the apoptosis of rat thymocytes in a direct contact. In contrast, TruFlex SE and Equire TA increased the proliferation of thymocytes. The cytotoxic effect of Rematitan SE correlated with the higher release of Ni ions in CM, higher concentration of surface Ni and an increased oxygen layer thickness after the conditioning. In conclusion, the apoptosis assay on rat thymocytes, in contrast to the less sensitive standard assay on L929 cells, revealed that Rematitan SE was less cytocompatible compared to other archwires and the effect was most probably associated with a higher exposition of the cells to Ni on the surface of the archwire, due to the formation of unstable oxide layer.

Evaluation of Mechanical and Physical Properties of Clinically Used and Recycled Superelastic NiTi Wires.

The initial leveling and aligning phase has been simplified with the introduction of superelastic nickel-titanium archwires. The relatively high cost of these wires has prompted some of the clinicians to reuse them after sterilization. The quantitative changes in the surface properties of superelastic 'NiTi' wires after clinical application and recycling by autoclave method have not been established in earlier studies. To quantify the changes in mechanical and physical properties of four different commercially available superelastic nitinol (NiTi) archwires after clinical usage and recycling. The superelastic 'NiTi archwires obtained from four different manufacturers: Group I-GAC (McMinnville, USA); Group II- 3M Company (California, USA); Group III- G&H Company(Franklin, USA) and Group IV- American Orthodontics (AO) (Sheboygan, USA) were selected for the study. Each of the four groups comprised of 20 samples of wire with 10 of them selected randomly as control and remaining 10 as test specimen in each group. The experimental archwires were placed on selected patients for a period of three months followed by Standard Autoclave sterilization at 121°C and 15 to 20 psi pressure for 20 minutes and were retrieved. The tensile strength was evaluated by Instron-Universal Testing Machine. The quantification of changes in surface roughness was investigated by grid method using Scanning Electron Microscope (SEM). The Control Wires (C) were evaluated at initial time "T1" where as the Experimental sample of wires (T) were subjected to testing at an initial time 'T1' and after clinical usage and sterilization at 'T2'. Paired t-test was used for intra-group comparison and one way ANOVA and Post Hoc Tukey tests were used for inter-group comparison. There was significant decrease in tensile strength (p = 0.0015 to 0.001) and surface roughness (p< 0.001) between control and experimental arch wires within each group when properties at T1 and T2 were compared. The study suggests discouraging the use of clinically used and sterilized superelastic NiTi archwires.

Fixed orthodontic appliances cause pain and disturbance in somatosensory function

This study aimed to assess the short-term effects of orthodontic pain on quantitative sensory testing (QST) in subjects receiving fixed orthodontic treatment. Twenty patients and 12 healthy volunteers (as controls) participated. All 20 patients had bonded AO self-ligating brackets, with a 0.014 super elastic nickel-titanium arch wire placed in the brackets. Pain [self-reported on a visual analog scale (VAS)], and thermal and mechanical thresholds, were tested at six time points--before (baseline), and 2 h, 24 h, 7 d, 14 d, and 30 d after, force application--in the treatment group. The attached gingiva adjacent to the left upper central incisor (21 gingiva) was hypersensitive to cold stimuli (i.e. increased cold detection thresholds were detected) in the treatment group. The pressure pain thresholds of the left upper central incisor (21) and 21 gingiva were significantly reduced. Our results suggest clear signs of sensitization of the trigeminal nociceptive system up to 1 month after force application and orthodontic pain. Quantitative assessment of somatosensory function may help to provide a better understanding and profiling of the underlying neurobiological mechanisms related to orthodontic pain.