A comparative evaluation of ion release from different commercially-available orthodontic mini-implants - an in-vitro study.

Background: Titanium alloy mini-implants have become popular in recent times and have been extensively used and studied. Although corrosion resistance of orthodontic materials has always been of concern, this property has been the least explored. The present study aimed to assess the composition, surface characterisation and corrosion resistance of five commercially available mini-implants by assaying ion release in artificial saliva.

Methods: Ten mini-implants each from five companies were obtained: Group 1 - AbsoAnchor (Dentos Inc, South Korea); Group 2 - Microimplant Anchorage System (MIA, Biomaterials Korea); Group 3 - The Orthodontic Mini Anchorage System (TOMAS, Dentaurum, Germany); Group 4 - mini-implants (Denticon, Maharashtra, India); Group 5 - orthodontic mini-implants (lJ.Orthodontics, Kerala, India). One mini-implant from each group was subjected to characterisation and surface microstructure analysis using Energy Dispersive Atomic Spectrometry (EDAX) and Scanning Electron Microscope (SEM), respectively. Ten mini- implants were immersed for 30 days in Fusayama-Meyer artificial saliva solution and the release of titanium, aluminium and vanadium ions was detected with Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES). The Kruskal-Wallis test was used for multi-variate analysis. In order to determine the significant differences between the groups on independent samples, the Mann-Whitney U test (bi-variate analysis) was applied.

Results and conclusion: All groups showed machining defects but surface pitting after immersion was mostly evident in Group 4. Although the composition of all the implants was comparable, there was a statistically significant difference in the Ti, Al and V release between Group 4 - the group with maximum release - and Group 2, the group with least release.