these situations be studied to answer the question of whether miniimplants can be re-used or not.Therefore, the objective of this study was to compare as-received, sterilized and retrieved mini-implants as to their surface topography and fracture torque resistance in order to evaluate the mechanical risks of re-using orthodontic mini-implants after sterilization.
Materials and MethodsAll mini-implants in this study were of the same type and from the same manufacturer (SIN, São Paulo, Brazil), self-drilling, made from Ti6Al4V alloy and with a diameter of 1.4 mm and a thread length of 8 mm.Forty mini-implants from a single manufacturing lot were purchased from the manufacturer. Twenty mini-implants were submitted to a sterilization process in a dental steam autoclave (STERMAX, Pinhais, Brazil). The autoclave fulfilled the requirements of the British Stardards Institution ISO 9001:2000. Its efficacy was previously tested by a biological indicator test (Clean Test 10, SIEGER, Campo Mourão, Brazil). Each mini-implant was inserted in an individual auto-sealing envelope (ZERMATT, São Paulo, Brazil) and all mini-implants were then submitted to one sterilizing cycle of 30 minutes at 121 °C, according to the recommendations of the manufacturer of the autoclave. The other 20 mini-implants served as a control group and were analyzed and tested as received from the manufacturer.
IntroductionMini-implants have been used for over a decade now since their introduction in Orthodontics as a skeletal anchorage system. They are an important aid in anchorage control and a determinant factor for success in orthodontic treatment. Their popularity is due especially to their simple placement with less traumatic surgery, less discomfort for patients, possibility of immediate loading and high versatility [1][2][3][4][5][6][7] . Biomaterials may be used for temporary purposes in the body, like coverscrews for dental implants, wires or fracture fixation plates 8 . The mini-implants are included in this category, as they are removed once they are of no further assistance in the orthodontic treatment. After removal of temporary devices, the recovered devices are usually discarded. However, economic factors have caused some clinicians to re-use implants or other medical devices that are meant to be disposable, like pacemakers, intra-aortic balloons, haemodialysis membranes, coronary angioplasty catheters and orthodontic brackets and wires [8][9][10] . In case of re-use, it is mandatory to ensure the sterility and mechanical qualities of the device 11 . Not all implants can be re-used, but metal implants, like those made from titanium may be more amenable to re-use because they can be mechanically and chemically cleaned and re-sterilized with potentially little or no loss of form or function 8 . One study investigated the characterization of retrieved orthodontic mini-implants by optical microscopy, Scanning Electron Microscopy (SEM), X-ray microtomography and X-ray microanalysis 12 , but no studies have assessed re-use of mini-implants. As p...