The insertion torque and pullout strength of orthodontic mini-implants

Introduction: Different configurations of mini-implants screw can influence the torque of insertion, the pullout strength and consequently, the primary stability. The objective was to evaluate the insertion torque and pullout strength of five types of mini-implants. Material and Method: Were obtained images of the mini-implants active points (STEMI 2000-C and MEV) and analyzed by the Axio Vision program (Zeiss, Jena, Germany). Five mini-implants in each group: NEO(Neodent), SIN, CON (Connection), DEN (Dentaurum) and RMO were inserted into porcine rib and the insertion torque recorded by the Lutron 101 software. The tensile test was carried out in the Universal Machine Emic DL 10000 (100kgf/0.05mm/sec). Results: The torque of insertion ranged from 6.40 Ncm to 14.60 Ncm, with a statistically significant difference between groups and RMO DEN, and DEN, CON, NEO and CON; and NEO and RMO. The pullout strength ranged between 136.45 N and 227.30 N, and there was no statistically significant difference between groups. Conclusions: Different mini implants showed active spikes with different characteristics. The torque of insertion was directly proportional to the number of threads and inversely to the fillet angle and bottom of the threads (p 0.05).Introdução: Diferentes configurações de filete de mini-implantes podem influenciar no torque de inserção, na força de arrancamento e conseqüentemente, na estabilidade primária. Objetivou-se avaliar torque de inserção e força de arrancamento de cinco tipos de mini-implantes. Material e Método: Foram obtidas imagens das pontas ativas dos mini-implantes (Stemi 2000-C e do MEV) e analisadas através do programa Axio Vision (Zeiss, Jena, Alemanha). Cinco mini-implantes de cada grupo (Neodent-NEO, SIN, Conexão-CON, Dentaurum-DEN e RMO) foram inseridos em costela suína e o torque de inserção registrado pelo programa Lutron 101. O ensaio à tração foi realizado em máquina Universal Emic DL 10000 (100kgf/0,05mm/seg). Resultados: O torque de inserção variou de 6,40Ncm a 14,60Ncm, com diferença estatisticamente significativa entre os grupos DEN e RMO; DEN e CON; NEO e CON e; NEO e RMO. A força de arrancamento variou entre 136,45N e 227,30N, não houve diferença estatisticamente significativa entre os grupos. Conclusões: Diferentes mini-implantes apresentaram pontas ativas com características distintas. O torque de inserção se mostrou diretamente proporcional ao número de filetes e inversamente ao passo, ângulo e fundo do filete (p0,05)

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

Fracture strength of orthodontic mini-implants

ABSTRACT Objective: This study aimed at evaluating the design and dimensions of five different brands of orthodontic mini-implants, as well as their influence on torsional fracture strength. Methods: Fifty mini-implants were divided into five groups corresponding to different manufactures (DEN, RMO, CON, NEO, SIN). Twenty-five mini-implants were subjected to fracture test by torsion in the neck and the tip, through arbors attached to a Universal Mechanical Testing Machine. The other 25 mini-implants were subjected to insertion torque test into blocks of pork ribs using a torquimeter and contra-angle handpiece mounted in a surgical motor. The shape of the active tip of the mini-implants was evaluated under microscopy. The non-parametric Friedman test and Snedecor’s F in analysis of variance (ANOVA) were used to evaluate the differences between groups. Results: The fracture torque of the neck ranged from 23.45 N.cm (DEN) to 34.82 N.cm (SIN), and of the tip ranged from 9.35 N.cm (CON) to 24.36 N.cm (NEO). Insertion torque values ranged from 6.6 N.cm (RMO) to 10.2 N.cm (NEO). The characteristics that most influenced the results were outer diameter, inner diameter, the ratio between internal and external diameters, and the existence of milling in the apical region of the mini-implant. Conclusions: The fracture torques were different for both the neck and the tip of the five types evaluated. NEO and SIN mini-implants showed the highest resistance to fracture of the neck and tip. The fracture torques of both tip and neck were higher than the torque required to insert mini-implants