Fracture strength of orthodontic mini-implants.

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.

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.

RESUMO Objetivo: o objetivo do presente estudo foi avaliar o desenho e as medidas de cinco marcas diferentes de mini-implantes ortodônticos, e sua influência na resistência à fratura em torção. Métodos: cinquenta mini-implantes foram divididos em cinco grupos, correspondentes a diferentes fabricantes (DEN, Dentaurum; RMO, Rocky Mountain Orthodontics; CON, Conexão; NEO, Neodent; SIN, Sistema de Implantes Nacional). Vinte e cinco mini-implantes foram submetidos ao teste de fratura por torção no pescoço e na ponta, com mandris fixados a uma máquina universal de testes mecânicos. Os outros 25 mini-implantes foram submetidos ao teste de torque de inserção em blocos de costelas suínas, utilizando-se um torquímetro e um contra-ângulo montado em motor cirúrgico. O formato da ponta ativa dos mini-implantes foi avaliado por microscopia. O teste não-paramétrico de Friedman e o teste F de Snedecor na análise de variância (ANOVA) foram utilizados para avaliar as diferenças entre os grupos. Resultados: o torque de fratura do pescoço variou de 23,45 N.cm (DEN) a 34,82 N.cm (SIN); e o da ponta, entre 9,35 N.cm (CON) e 24,36 N.cm (NEO). O valor do torque de inserção variou de 6,6 N.cm (RMO) a 10,2 N.cm (NEO). As características que mais influenciaram os resultados foram: diâmetro externo, diâmetro interno, razão entre o diâmetro interno e o externo, e a presença de fresagem na região apical do mini-implante. Conclusões: os torques de fratura foram diferentes entre os cinco tipos avaliados, tanto no pescoço quanto na ponta. Os mini-implantes NEO e SIN foram os mais resistentes à fratura do pescoço e da ponta. Os torques de fratura tanto na ponta quanto no pescoço foram maiores do que o torque necessário para a inserção dos mini-implantes.

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.

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.

OBJETIVO: avaliar morfologicamente a ponta ativa de seis diferentes tipos de mini-implantes autoperfurantes para controle de ancoragem ortodôntica. MÉTODOS: foram obtidas imagens das pontas ativas dos mini-implantes com o microscópio óptico Stemi 2000-C (Zeiss) com aumento de 1,6X. As imagens das superfícies foram analisadas no programa Axio Vision (Zeiss, Jena, Alemanha) para cálculo das medidas lineares e angulares. As morfologias dos mini-implantes e os detalhes das pontas e das roscas também foram avaliados por meio do Microscópio Eletrônico de Varredura (MEV) (JEOL, modelo JSM-5800 LV - JEOL, Tóquio, Japão) com aumentos de 90X e 70X, respectivamente. A avaliação da conicidade do mini-implante foi calculada de acordo com a fórmula: (b - a) / (2 x D). RESULTADOS: foram medidos (1) comprimento da ponta ativa, (2) diâmetro externo, (3) alma e conicidade do mini-implante, (4) número e passo das roscas, (5) ângulo do filete da rosca, (6) comprimento do flanco da rosca e (7) comprimento do fundo do filete da rosca. CONCLUSÕES: mini-implantes de diferentes fabricantes apresentaram suas pontas ativas com características diversas. Ensaios mecânicos são necessários para correlacionar as características analisadas.

Assessment of enamel damage after removal of ceramic brackets.

INTRODUCTION: Since the introduction of ceramic brackets, research has been performed to evaluate enamel damage caused during their removal. One problem in comparing treated and control groups is the absence of assurance that the surfaces were undamaged before the brackets were bonded and debonded, or that superficial treatment applied to the enamel could hinder damage detection. The aim of this in-vitro study was to evaluate enamel injuries during debonding of 3 types of ceramic brackets. METHODS: Forty-five premolars, extracted for orthodontic purposes, were divided into 3 groups of 15. The enamel surfaces were photographed with a magnifying loupe (60 times) in an optical stereomicroscope (Stemi 2000-C, Zeiss, Oberkochen, Germany) with a digital camera. A different type of backet was bonded and debonded in each group: mechanical retention, mechanical retention with a polymer base, and chemical retention. After debonding, the surfaces were again photographed. The photographs were evaluated for quality of enamel surface according to a predetermined scale. The results were tested by method error and the chi-square test. RESULTS: The damage evaluation comparing the same surface before bonding and after debonding showed no significant statistical difference between the mechanical retention group and the polymer base retention group. There was a significant statistical difference (P <0.05) for the chemical adhesion ceramic bracket group. CONCLUSIONS: The difference between the enamel surfaces before bonding and after debonding brackets with chemical retention was statistically significant; bonding and debonding these brackets resulted in enamel damage.