Morphological evaluation of the active tip of six types of orthodontic mini-implants.

Objective: To morphologically evaluate the active tip of six different types of self-drilling mini-implants for orthodontic anchorage.

Methods: Images of the active tips of the mini-implants were obtained with a Zeiss optical microscope Stemi 200-C, with magnification of 1.6X. The images of the surface were viewed with the Axio Vision program (Zeiss, Jena, Germany) to calculate linear and angular measures. Mini-implant morphology and the details of tips and threads were also evaluated through Scanning Electronic Microscopy (SEM) (JEOL, model JSM5800 LV - JEOL, Tokyo, Japan) with magnifications of 90X and 70X, respectively. The evaluation of the mini-implant taper shape was assessed using the formula: (b - a) / (2 x D).

Results: The following variables were measured: (1) active tip width, (2) major diameter of external thread, (3) minor diameter of internal thread and taper of the mini-implant, (4) number of threads and lead of the screw, (5) angle of thread, (6) flank width and (7) pitch width.

Conclusions: Mini-implants from different manufacturers presented active tips with different characteristics. Mechanical testing is necessary to correlate the analyzed characteristics aiming to determine the best performance.