http://www.revmaterialeplastice.ro MATERIALE PLASTICE ♦54♦No.2 ♦2017 253 Biochemical Characteristics of Mini-implants Sterilised by Different Chemical and Physical Procedures SILVIA IZABELLA POP 1 , DANA CRISTINA BRATU 2 *, RADU CHIOREAN 3 , RALUCA ADRIANA BALAN 2 , ANAMARIA BUD 4 , HORATIU POMPILIU PETRESCU 5 , CATALIN PETRU SIMON 6 , MIRCEA DUDESCU 3 1 University of Medicine and Pharmacy Targu-Mures, Department of Orthodontics, 38 Gh. Marinescu Str., 540139, Targu Mures, Romania 2 University of Medicine and Pharmacy Victor Babes, Faculty of Dentistry, Department of Orthodontics, 9 Revolution Str., 300070, Timisoara, Romania 3 Technical University of Cluj-Napoca, Department of Mechanical Engineering, 28 Memorandumului Str., 400114, Cluj Napoca, Romania 4 University of Medicine and Pharmacy Targu-Mures, Department of Paedodontics, 38 Gh. Marinescu Str., 540139, Targu Mures, Romania 5 University of Medicine and Pharmacy Victor Babes, Department of Orthopedy and Traumatology, 2 Eftimie Murgu Sq., , 300041, Timisoara, Eomania 6 University of Medicine and Pharmacy Victor Babes, Department of Anatomy and Embriology, 2 Eftimie Murgu Sq., 300041, Timisoara, Romania One hundred micro-implants from two different manufacturers were used in the study. From each manufacturer (Link from MIS TM and Yesanchor from Orlus TM ) the implants were divided in 5 groups: G0 (n= 10) new, unused, G1 (n= 10) mini-implants inserted in pig bone and removed, ultrasonically cleaned, followed by autoclave sterilization, G2 (n= 10) same insertion protocol of group 2 followed by chemical cleaning with phosphoric gel and autoclave strerilization, G3 (n= 10) same insertion protocol of group 1 followed by sandblasting and autoclave sterilization, G4 (n= 10) same insertion protocol of group 2 followed by cleaning with distilled water and autoclave sterilization. Maximum insertion torque was recorded and subjected to statistical testing. Our results showed significant differences of the maximum insertion torques between groups of Link mini-implant (p= 0.006), and no statistical differences of the maximum insertion torques of the Yesanchor implants (p= 0.33). Significant differences (p< 0.001) were also recorded between the groups of the two types of minii-mplants when compared. Our findings showed that brand-specific differences in maximum insertion torque exist between the two types of mini-implants. Keywords: micro-implants; sterilizations; maximum insertion torque Orthodontic mini-implants or TADs (Temporary anchorage devices) are more and more popular in clinical orthodontics. These devices are mainly used to reinforce the anchorage and to facilitate difficult tooth movements. Mini-implants offer numerous advantages: small size, which permits rapid and atraumatic placement in almost all sites within the mouth [1-3]. 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 [4-6]. Treatment costs are significantly increased if new mini- implants are used every time a retrieved one is not reused, in the same patient. On the other side, reusing a medical device can only be performed when its sterilization and preparation does not alter the clinical and mechanical properties of the device [2,4]. The effect of different sterilization protocols on other orthodontic products (pliers, archwires, ligatures etc) was widely studied in the orthodontic literature [7-11, 26-28], 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. Previous studies [5,7,12, ] emphasized that only autoclaving sterilization does not affect the fracture torque of the mini-implants. However, microscopic images demonstrated that organic tissue remains are hardly removed from a mini-implants surface, even after many cleanings and sterilization [7]. The objective of this study was to evaluate the insertion torque of mini-implants which underwent different cleaning and sterilization protocols after insertion in pig mandibular bone. It was also aimed to compare the insertion torque of the sterilized implants with the new, unused ones. Experimental part A total number of 100 mini-implants from two different manufacturers (Link from MIS TM , MIS Implants Distribution, Bucharest and Yesanchor from Orlus TM , Seoul, Korea), were included in this study. These two manufacturers were chosen because their mini-implants are the most used and popular in Romania. On the other hand one of the mini- implants type was cylindrical and the other conic, both having the same dimension 1.6 x 8 mm. From each manufacturer the implants were randomly divided in 5 groups from G0 to G4. Group G0 (n= 10) included new, unused mini-implnats as control group. The G1 group (n= 10) consisted of mini-implants inserted in pig