Effect of Recycling Protocol on Mechanical Strength of Used Mini-Implants

Abstract

Purpose. This study evaluated the influence of recycling process on the torsional strength of mini-implants. Materials and Methods. Two hundred mini-implants were divided into 4 groups with 50 screws equally distributed in five diameters (1.3 to 1.7 mm): control group (CG): unused mini-implants, G1: mini-implants inserted in pig iliac bone and removed, G2: same protocol of group 1 followed by sonication for cleaning and autoclave sterilization, and G3: same insertion protocol of group 1 followed by sonication for cleaning before and after sandblasting (Al2O3-90 µ) and autoclave sterilization. G2 and G3 mini-implants were weighed after recycling process to evaluate weight loss (W). All the screws were broken to determine the fracture torque (FT). The influence of recycling process on FT and W was evaluated by ANOVA, Mann-Whitney, and multiple linear regression analysis. Results. FT was not influenced by recycling protocols even when sandblasting was added. Sandblasting caused weight loss due to abrasive mechanical stripping of screw surface. Screw diameter was the only variable that affected FT. Conclusions. Torsional strengths of screws that underwent the recycling protocols were not changed. Thus, screw diameter choice can be a more critical step to avoid screw fracture than recycling decision.

Biochemical Characteristics of Mini-implants Sterilised by Different Chemical and Physical Procedures

“…It was also suggested that, by mechanical stripping, the surface of a used implant is better cleaned. Regarding its effect on the mechanical properties, it has been suggested [3,23] that the removal torque was increased while, the fracture torque was not modified [6]. We found statistically significant greater insertion torque for the sandblasted Link mini-implants (26.94 Ncm) and lower insertion torque for Yesanchor (36.46 Ncm) implants.…”

“…Analyzing the effect of the sonification to the mechanical properties of a mini-implant, it can be concluded that, in both types (Link and Yesanchor), the maximum insertion torque slightly but not significantly decreased. Estelita et al [6] compared the fracture torque of the new and ultrasonically cleaned miniimplants fracture torque and revealed no significant differnces. Group G2 underwent chemical cleaning with phosphoric acid.…”

“…Maximum insertion torque is defined as the maximum torque recorded during the insertion procedure of a miniimplant measured in Ncm. It is a result of friction between screw threads and bone (artificial or human) and can be used as a reliable parameter to determine whether primary mini-implant stability can be achieved [1][2][3][4][5][6]. Although the success rate of the mini-implants might be affected by its maximum insertion torque.…”

“…The reinsertion of a mini-implant might be necessary in some cases, especially when mobility of the mini-screw, due to bone resorption or soft tissue inflammation is observed or when it is used in other part of the mouth for another purpose [4][5][6].…”

“…The effect of different sterilization protocols on other orthodontic products (pliers, archwires, ligatures etc) was widely studied in the orthodontic literature [7][8][9][10][11][26][27][28], but there is less information about the effect of chemical and physical sterilization methods on the surface topography and mechanical properties of the orthodontic mini-screws. Important parametes to test a mini-implant stability and mechanical property are the insertion and the fracture torque [4,6]. Especially, the insertion torque is a * email: danacristinabratu@yahoo.com; Phone: 0040744835314 reliable stability measurement when a mini-implant is desired to be reinserted several times.…”