Influence of various fluoride agents on working properties and surface characteristics of uncoated, rhodium coated and nitrified nickel-titanium orthodontic wires

Assessment of Nickel and Chromium Level in Gingival Crevicular Fluid in Patients Undergoing Orthodontic Treatment with or without Fluoridated Tooth Paste

BACKGROUND

Release of metallic ions, especially nickel and chromium, present in orthodontic fixed appliance attachments such as brackets and archwires has been a basis of concern in current years. The present study was conducted to assess nickel and chromium level in gingival crevicular fluid in patients undergoing orthodontic treatment.

MATERIALS AND METHODS

Forty patients undergoing fixed orthodontic treatment were divided into 2 groups of 20 each. Group I was fixed orthodontic treatment group and was given nonfluoridated toothpaste and Group II was fixed orthodontic treatment group and was given fluoridated toothpaste. The assessment of salivary nickel and chromium levels was done using inductively coupled plasma mass spectrometry.

RESULTS

In group I, there were 6 male and 14 female and in group II 7 males and 13 females. The mean nickel level (ng/ml) before treatment in group I was 0.49 and in group II was 0.52, on 7^th day was 0.52 and 0.54, on 30^th day was 13.4 and 100.2, and on 6^th month was 0.54 and 0.52 in Group I and II, respectively. The mean chromium level (ng/ml) before treatment in Group I was 0.48 and in Group II was 0.52, on 7^th day was 0.52 and 0.53, on 30^th day was 40.6 and 62.4 and on 6^th month was 4.9 and 0.52 in Group I and II, respectively. The difference was significant (P < 0.05).

CONCLUSION

The release of metal ions such as nickel and chromium was more with fluoridated toothpaste as compared to nonfluoridated toothpaste in patients undergoing fixed orthodontics.

The effect of fluoride gel on tensile properties, surface morphology and chemical composition of two types of orthodontic wires (an in-vitro study)

OBJECTIVE:

Stainless steel and nickel-titanium wires are commonly used in fixed orthodontic appliances. Orthodontists often prescribe fluoride gel to avoid demineralization of teeth. This study investigated the effect of acidulated phosphate fluoride gel on the tensile properties, surface morphology and surface chemical composition of stainless steel and nickel-titanium wires.

METHODS:

Forty samples of stainless steel and nickel-titanium wires were examined, twenty for each type. Each wire type was divided into four subgroups. The first subgroup was not immersed in fluoride gel and considered as control, while the other three subgroups were immersed in 10 mL of fluoride gel for different periods of time. Then, the wires were removed from the gel, rinsed in a distilled water and left to dry. The ultimate tensile force of each wire was measured using a tensile testing machine. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to examine the control and 24 h immersed subgroups.

RESULTS:

One-way analysis of variance ANOVA showed that there were no significant differences in the ultimate tensile forces between control and fluoride-treated subgroups (P = 0.172 for SS wires and P = 0.672 for NiTi wires). However, changes in the surface morphology and elemental composition of wires were shown by the SEM and EDX.

CONCLUSIONS:

Although immersion of stainless steel and nickel-titanium wires in the fluoride gel did not affect their tensile properties, however, surface deterioration was evident. So, further investigations are recommended to study the effect of these changes on the oral health of patients.

Influence of intraoral application of antiseptics and fluorides during orthodontic treatment on corrosion and mechanical characteristics of nickel-titanium alloy in orthodontic appliances

OBJECTIVES

To explore whether the commercial agents recommended for controlling dental biofilm formation had a significant effect in vivo on mechanical and corrosion properties of nickel-titanium (NiTi) alloy.

MATERIALS AND METHODS

NiTi archwires (dimensions 0.508 × 0.508 mm) were collected from 36 orthodontic patients aged 13-42 years after a 3-month intraoral exposure. Three experimental groups were formed: (1) subjects conducting regular oral hygiene, (2) subjects who used fluorides for intensive prophylaxis for the first month, and (3) subjects who used chlorhexidine in the same manner. Corrosion behavior, surface characteristics, stiffness, hardness, and friction were analyzed.

RESULTS

Exposure to intraoral conditions significantly reduced the stiffness and hardness of the NiTi alloy (P ≤ .015). Fluoride tended to reduce stiffness and hardness more than did saliva or antiseptic, but not significantly. Roughness and friction were not significantly influenced by oral exposure. Intraoral aging predominantly produced general corrosion independent of the adjuvant prophylactic agent, although localized corrosion may also have occurred.

CONCLUSIONS

Fluorides and the antiseptic chlorhexidine do not increase corrosion more than saliva itself, nor do they further modify the mechanical properties of the NiTi alloy.

Effect of gastric acids on surface topography and bending properties of esthetic coated nickel-titanium orthodontic archwires

OBJECTIVE

The purpose of this study was to evaluate the effect of simulated gastric acid solution on surface topography and bending properties of esthetic coated nickel-titanium (NiTi) archwires.

MATERIALS AND METHODS

Three brands of as-received white-coated superelastic NiTi upper archwires were used in this study: Dany, Perfect, and Nitanium. Uncoated metallic areas for each white-coated NiTi archwire were used for comparison with the coated areas. The specimens for each archwire were divided into two groups according to coating as follows: Group A, uncoated, and group B, coated. Then, each group was further subdivided into two subgroups according to the immersion medium as follows: Subgroup 1, immersed in artificial saliva, and subgroup 2, immersed in simulated gastric acid. Surface roughness, surface morphology, and three-point bending test were performed. The data were analyzed statistically using ANOVA and Tukey test.

RESULTS

The archwires immersed in simulated gastric acid solution showed significantly higher surface roughness and lower forces on loading and unloading than the archwires immersed in artificial saliva (P < 0.001). Perfect archwire showed significantly the highest surface roughness compared with Dany and Nitanium archwires (P < 0.001). The uncoated archwires showed higher loading and unloading forces compared with coated archwires for all groups (P < 0.001). Nitanium archwire showed the lowest loading and unloading forces at different deflections (P < 0.001).

CONCLUSIONS

The simulated gastric acid solution decreased considerably the amount of force applied at a given deflection. The loading-deflection and surface roughness properties of coated archwires were affected by the type of coating material.

CLINICAL RELEVANCE

The impact of gastric acids on surface and mechanical properties of orthodontic archwires depend on type of coating materials.

Effect of 0.05% Sodium Fluoride Mouthwash on Surface Roughness and Friction between Ceramic Brackets and Rhodium-Coated and Uncoated Stainless Steel Wires

Objectives:

This study aimed to assess the effect of 0.05% sodium fluoride (NaF) mouthwash on the surface roughness and friction between ceramic brackets and rhodium-coated (RC) and uncoated stainless steel (SS) wires.

Materials and Methods:

This experimental study was performed on 48 maxillary premolar ceramic brackets. Twenty-four pieces of RC-SS wires were used. Samples were divided into four groups. Groups 1 and 2 were immersed in artificial saliva, and groups 3 and 4 were immersed in a solution consisting of artificial saliva (9%) and mouthwash (91%). To assess surface roughness, images were obtained from the surface of wires and brackets with atomic force microscopy (AFM) and scanning electron microscopy (SEM) before and after the intervention. To assess friction, the wires were ligated into brackets, and friction was measured at a crosshead speed of 0.5 mm/minute using a universal testing machine. Data were analyzed using one-way analysis of variance (ANOVA) at the 0.05 significance level.

Results:

Friction during sliding in RC wires was significantly less than that in SS wires (P<0.05). Increase in the friction in SS wires by mouthwash was significantly greater compared to RC wires (P<0.05). Surface roughness coefficients of the wires before the intervention were not significantly different. The surface roughness of the wires significantly increased after the intervention and it was greater in SS wires than in RC wires (P<0.05).

Conclusion:

Considering the lower friction and surface roughness of SS-RC wires compared to SS wires, SS-RC wires may be a better alternative for use with ceramic brackets.

Oral antiseptics and nickel-titanium alloys: mechanical and chemical effects of interaction

The effect of oral antiseptics on the corrosion of nickel-titanium (NiTi) alloys with various coating was investigated. Uncoated, titanium nitride-coated and rhodium-coated NiTi archwires (0.020 × 0.020″) were tested in interaction with artificial saliva pH 4.8 and oral antiseptics based on hyaluronic acid (Gengigel), chlorhexidine (Curasept) and essential oils in alcohol base (Listerine). The dynamics of nickel and titanium ions release were recorded during 28 days. Springback ratio and modulus of resilience were assessed by three-point bending test. The results showed that corrosion of NiTi is related to type of antiseptic mouth rinse and coating formulations. Exposure to an artificial saliva and antiseptics tend to reduce flexibility and resilience of NiTi archwires. The influence of the media is more significant than the influence of the type of the alloys coating. The largest release of nickel ions is in the first 3 days. Antiseptics do not cause further deterioration of the elastic properties in uncoated NiTi compared to saliva. As a result of exposure of nitrified NiTi wires in Listerine, there is bigger release of nickel ions, decrease in elastic properties and lower force delivery in unload. Listerine tends to reduce elastic properties of rhodium-coated wires also. In conclusion, except for Listerine, changes of mechanical characteristics induced by antiseptics are small and would not have a clinically important impact. Generally, Curasept would be the most suitable option.

Deflection and Flexural Strength Effects on the Roughness of Aesthetic-Coated Orthodontic Wires

The aim was to evaluate the flexural strength and the effects of deflection on the surface roughness of esthetic orthodontic wires. The sample consisted of 70 archwire 0.014-inch: polytetrafluorethylene (PTFE)-coated Nickel-Titanium (Niti) archwires (Titanol Cosmetic-TC, Flexy Super Elastic Esthetic-FSE, esthetic Nickel Titanium Wire-ANT); epoxy resin-coated Niti archwires (Spectra-S, Niticosmetic-TEC); gold and rhodium coated Niti (Sentalloy-STC) and a control group (superelastic Niti (Nitinol-NS). The initial roughness was evaluated with a rugosimeter. After that, the wires were submitted to flexural test in an universal testing machine. Each wire was deflected up to 2 mm at a speed of 1 mm/min. After flexural test, the roughness of the wires was evaluted on the same surface as that used for the initial evaluation. The data of roughness and flexural strength were analyzed by one-way ANOVA and Tukey's test (a=0.05). Student t-test compared roughness before and after deflection (a =0.05). The roughness of S and ANT (epoxy resin and PTFE-coated wires, respectively), before and after deflection, was significantly higher than the other groups (p<0.05). Wire deflection significantly increased the roughness of the wires S and STC (p<0.05). The flexural strength of groups FSE and NS (PTFE and uncoated) was higher compared with that of the other groups (p<0.05). We concluded that the roughness and flexural strength of the orthodontic wires does not depend on the type of the esthetic coating, but it is influenced by the method of application of this coating. The deflection can increase the roughness of the esthetic orthodontic wires.