Evaluation of sterilising methods for re-implantation of orthodontic mini-implants
di Pasquale, Taryn
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Re-implantation of mini-implants would be financially advantageous in orthodontics and could encourage an increase in use of these devices. An analysis of the bacterial contamination after different sterilising methods has currently not been performed. The aim of this study was to determine the most effective method in sterilising of orthodontic mini-implants for re-implantation in the same patient. The sample included 40 retrieved mini-implants which were collected from private orthodontists, orthodontic registrars, and a maxillo-facial and oral surgeon in South Africa after completed use in patients. They were allocated into groups that underwent different sterilising processes. Gr1 was autoclaved; Gr2 was immersed in 37% phosphoric acid for 10 minutes, followed by being soaked in Milton for 30 minutes; Gr3 was dipped in 70% ethanol and then flamed in a butane gas burner; and GrC did not undergo any processing and served as the control. Bacteria remaining after processing were cultured in Brain Heart Infusion Medium and incubated at 37 degrees Celsius to determine whether any bacterial contamination remained on the mini-implant. To investigate the effects of the sterilising methods on the surface of the mini-implants, they then underwent scanning electron microscopy analysis to assess amount of visible tissue remnants which remained on the surface. These miniimplants were further subjected to energy dispersive spectroscopy (EDS) to investigate their elemental composition. All processing methods were able to sterilise the mini-implants tested and no bacterial growth was present after culturing in Brain Heart Infusion Medium. There were, however, differences in their surface appearances. Gr2 displayed the least amount remaining surface remnants (mean 5.21%), whereas Gr1 (autoclave) and Gr3 (burnt) showed mean of 30.08 and 47.04% tissue remnants on their surfaces respectively. Titanium, aluminium, vanadium, carbon and oxygen were found on all surfaces of the groups. Additional elements, namely, calcium, potassium, sodium, phosphorous, sulphur, silicon, bromine, chlorine, nitrogen, and magnesium were found in the tissue remnants of all the processing groups. Sterilising methods autoclave and burning (Gr1 and Gr3), which made use of heat, had almost double the atomic percentage of carbon. Gr2, etch and Milton, had the lowest atomic percentage of calcium and none of the mini-implants in this group showed traces of iron, which was present in the other groups. Based on the methods tested in this study, Gr2 which involves immersing the mini-implant in 37% phosphoric acid for 10 minutes, followed by soaking mini-implant in Milton for 30 minutes is the suggested method of sterilising mini-implants before re-implantation. Further studies looking into additional sterilisation methods, possibly with the use of sonication or scrubbing, are required to draw up protocols on reimplantation of mini-implants. Additional histological and ion release tests will also be required to confirm which method of sterilisation will result in no additional complications in the patient to that of insertion of a new, unused mini-implant.