Evaluation of cytotoxicity and corrosion resistance of orthodontic mini-implants

Abstract

Objective: To evaluate and compare in vitro cytotoxicity and corrosion resistance of mini-implants from three different commercial brands used for orthodontic anchorage. Methods: Six mini-implants (Conexão(tm), Neodent(tm) and SIN(tm)) were separately immersed in artificial saliva (pH 6.76) for 30 and 60 days. The cytotoxicity of the corrosion extracts was assessed in L929 cell cultures using the violet crystal and MTT assays, as well as cell morphology under light microscopy. Metal surface characteristics before and after immersion in artificial saliva were assessed by means of scanning electron microscopy (SEM). The samples underwent atomic absorption spectrophotometry to determine the concentrations of aluminum and vanadium ions, constituent elements of the alloy that present potential toxicity. For statistical analysis, one-way ANOVA/Bonferroni tests were used for comparisons among groups with p < 0.05 considered significant. Statistical analysis was carried out with Graph Pad PRISM software Version 4.0. Results: No changes in cell viability or morphology were observed. Mini-implants SEM images revealed smooth surfaces with no obvious traces of corrosion. The extracts assessed by means of atomic absorption spectrophotometry presented concentrations of aluminum and vanadium ions below 1.0 µg/mL and 0.5 µg/mL, respectively. Conclusion: Orthodontic mini-implants manufactured by Conexão(tm), Neodent(tm) and SIN(tm) present high corrosion resistance and are not cytotoxic.

Corrosion and Micromorphological Analysis of Temporary Stainless Steel and Titanium Alloy Anchorage Devices

“…The absence of mass and the ion loss in the solution after storage characterizes resistance to alloy degradation during the immersion period. This may be associated with how easily the chemical elements making up the Ti and stainless steel alloys formed oxide films on the surfaces of the metals [20], when in contact with the solution under the test conditions [18]. Passive film formation can occur by various means.…”

“…Some recent studies have shown that titanium alloys (TADs) may be considered corrosion-resistant [16][17][18], in compliance with the biosafety standards of alloys for human use [19], based on the stability of the passive titanium oxide layer on their surface [20]. However, Pavlic et al [21] showed that chlorhexidine increased the roughness of stainless steel mini-implants, whose mechanism is associated with pit corrosion and may cause the release of some ions from the material to the solution.…”

Cytotoxicity of bracket identification dyes

“…Previously, many studies have examined the tissue biocompatibility of orthodontic materials. [1][2][3][4][5][6][7][8][9][10] However, there has been no trial of the dyes used in the colored identification dots.…”

“…15 This model has also been used in many previous orthodontic studies. 3,4,7 Real-time cell-monitoring systems can be used conveniently for a wide variety of cell-based assays in scientific trials. 16 Although it is an in vitro method, it has considerable advantages over conventional animal testing methods and over other in vitro methods.…”

“…In the literature, many different orthodontic materials that could be considered innocent on first assessment, perhaps even more innocent than the dye, have been examined for their toxicity. Orthodontic brackets, 1 bands, 2 elastomeric ligatures, 3 mini-implants, 4 composites, 5 and aligners 6 have been evaluated by researchers, and information has been presented previously. In those papers, the biocompatibility of different orthodontic materials was investigated to determine whether they release ingredients that can be harmful to cells.…”