Análise da superfície e osseointegração de implantes dentários com superfícies biomiméticas contedo Ca, Mg e F

Os tratamentos das superfícies dos implantes dentários osseointegráveis sofreram modificações significativas com o objetivo de melhorar a estabilidade primária e secundária. Entre as modificações destaca-se a deposição de íons, como flúor, cálcio e magnésio. Estes íons possuem baixa taxa de degradação no meio corpóreo e ótima interação biológica com as células e com os tecidos ósseos. No presente trabalho, para avaliar os efeitos do F, Ca e do Mg na osseointegração foram realizados ensaios in vitro e in vivo. Implantes foram inseridos em tíbias de coelhos e determinou-se os torques de inserção e remoção após 2, 4 e 8 semanas. Os ensaios in vivo foram complementados pela medida da rugosidade, molhabilidade e análise da superfície em microscopia eletrônica de varredura. Os resultados foram comparados com os obtidos com implantes com a superfície tratada com ácido (superfície Porous) e com deposição de flúor (superfície Porous Nano). Os resultados obtidos mostraram que o torque para remover os implantes Porous 8 semanas após a cirurgia foi de 16,96 + 1,32 N.cm, o tratado com flúor apresentou melhores resultados (17,93 ± 4,47 N.cm) e a superfície com Ca e Mg foi a que apresentou a interface osso-implante com menor resistência (10,83 + 1,20 N.cm). O maior torque indica que a adição de flúor facilita os mecanismos envolvidos na osseointegração dos implantes e permite o carregamento da prótese em tempos menores

Influence of Screw Length and Bone Thickness on the Stability of Temporary Implants

The purpose of this work was to study the influence of screw length and bone thickness on the stability of temporary implants. A total of 96 self-drilling temporary screws with two different lengths were inserted into polyurethane blocks (n = 66), bovine femurs (n = 18) and rabbit tibia (n = 12) with different cortical thicknesses (1 to 8 mm). Screws insertion in polyurethane blocks was assisted by a universal testing machine, torque peaks were collected by a digital torquemeter and bone thickness was monitored by micro-CT. The results showed that the insertion torque was significantly increased with the thickness of cortical bone from polyurethane (p < 0.0001), bovine (p = 0.0035) and rabbit (p < 0.05) sources. Cancellous bone improved significantly the mechanical implant stability. Insertion torque and insertion strength was successfully moduled by equations, based on the cortical/cancellous bone behavior. Based on the results, insertion torque and bone strength can be estimate in order to prevent failure of the cortical layer during temporary screw placement. The stability provided by a cortical thickness of 2 or 1 mm coupled to cancellous bone was deemed sufficient for temporary implants stability

Influence of surface treatment on shear bond strength of orthodontic brackets

INTRODUCTION: The shear bond strength of orthodontic brackets bonded to micro-hybrid and micro-particulate resins under different surface treatment methods was assessed. METHODS: Two hundred and eighty test samples were divided into 28 groups (n = 10), where 140 specimens were filled with Durafill micro-particulate resin and 140 with Charisma composite. In 140 samples, a coupling agent (silane) was applied. The surface treatment methods were: Phosphoric and hydrofluoric acid etching, sodium bicarbonate and aluminum oxide blasting, stone and burs. A Universal Instron Machine was used to apply an occlusal shear force directly to the resin composite bracket surface at a speed of 0.5 mm/min. The means were compared using analysis of variance and multivariate regression to assess the interaction between composites and surface treatment methods. RESULTS: Means and standard deviations for the groups were: Sodium bicarbonate jet 11.27±2.78; burs 9.26±3.01; stone 7.95±3.67; aluminum oxide blasting 7.04±3.21; phosphoric acid 5.82±1.90; hydrofluoric acid 4.54±2.87, and without treatment 2.75±1.49. An increase of 1.94 MPa in shear bond strength was seen in Charisma groups. Silane agent application reduced the Charisma shear bond strength by 0.68 Mpa, but increased Durafill means for bicarbonate blasting (0.83), burs (0.98) and stone drilling (0.46). CONCLUSION: The sodium bicarbonate blasting, burs and stone drilling methods produced adequate shear bond strength and may be suitable for clinical use. The Charisma micro hybrid resin composite showed higher shear bond means than Durafill micro particle composite

Insertion torque versus mechanical resistance of mini- implants inserted in different cortical thickness

OBJECTIVE: This study aimed to measure insertion torque, tip mechanical resistance to fracture and transmucosal neck of mini-implants (MI) (Conex&#227;o Sistemas de Pr&#243;teseT), as well as to analyze surface morphology. METHODS: Mechanical tests were carried out to measure the insertion torque of MIs in different cortical thicknesses, and tip mechanical resistance to fracture as well as transmucosal neck of MIs. Surface morphology was assessed by scanning electron microscopy (SEM) before and after the mechanical tests. RESULTS: Values of mechanical resistance to fracture (22.14 N.cm and 54.95 N.cm) were higher and statistically different (P < 0.05) from values of insertion torque for 1-mm (7.60 N.cm) and 2-mm (13.27 N.cm) cortical thicknesses. Insertion torque was statistically similar (P > 0.05) to torsional fracture in the tip of MI (22.14 N.cm) when 3 mm cortical thickness (16.11 N.cm) and dense bone (23.95 N.cm) were used. Torsional fracture of the transmucosal neck (54.95 N.cm) was higher and statistically different (P < 0.05) from insertion torsional strength in all tested situations. SEM analysis showed that the MIs had the same smooth surface when received from the manufacturer and after the mechanical tests were performed. Additionally, no significant marks resulting from the manufacturing process were observed. CONCLUSION: All mini-implants tested presented adequate surface morphology. The resistance of mini-implants to fracture safely allows placement in 1 and 2-mm cortical thickness. However, in 3-mm cortical thickness and dense bones, pre-drilling with a bur is recommended before insertion

Análise da superfície e osseointegração de implantes dentários com superfícies biomiméticas contedo Ca, Mg e F

Os tratamentos das superfícies dos implantes dentários osseointegráveis sofreram modificações significativas com o objetivo de melhorar a estabilidade primária e secundária. Entre as modificações destaca-se a deposição de íons, como flúor, cálcio e magnésio. Estes íons possuem baixa taxa de degradação no meio corpóreo e ótima interação biológica com as células e com os tecidos ósseos. No presente trabalho, para avaliar os efeitos do F, Ca e do Mg na osseointegração foram realizados ensaios in vitro e in vivo. Implantes foram inseridos em tíbias de coelhos e determinou-se os torques de inserção e remoção após 2, 4 e 8 semanas. Os ensaios in vivo foram complementados pela medida da rugosidade, molhabilidade e análise da superfície em microscopia eletrônica de varredura. Os resultados foram comparados com os obtidos com implantes com a superfície tratada com ácido (superfície Porous) e com deposição de flúor (superfície Porous Nano). Os resultados obtidos mostraram que o torque para remover os implantes Porous 8 semanas após a cirurgia foi de 16,96 + 1,32 N.cm, o tratado com flúor apresentou melhores resultados (17,93 ± 4,47 N.cm) e a superfície com Ca e Mg foi a que apresentou a interface osso-implante com menor resistência (10,83 + 1,20 N.cm). O maior torque indica que a adição de flúor facilita os mecanismos envolvidos na osseointegração dos implantes e permite o carregamento da prótese em tempos menores

Influence of cortical thickness on the stability of mini-implants with microthreads

The objective of this study was to assess the influence of cortical thickness and bone density on the insertion torque of a mini-implant (MI) with microthreads. Mini-implants with lengths of 6 and 8 mm in the active part were inserted into synthetic bone blocks (polyurethane resin). The density of these blocks was 20 pounds per cubic foot (pcf), simulating bone marrow, and that of blocks 1, 2, and 3-mm-thick blocks was 40 pcf, simulating cortical bone. Blocks with uniform density of 40 pcf were also used to simulate bone areas of greater density. Insertion torque was quantified with a universal testing machine (EMIC). For both MIs, increasing insertion torque was associated with increasing cortical bone thickness. For the same MI length, significant differences were observed among all assessed groups. The insertion torque of the 6-mm-long MI inserted in a 3-mm-thick cortical bone was equivalent to that of the 8-mm-long MI inserted in a 1-mm-thick cortical bone. MIs inserted in bone blocks of greater density presented insertion torque values almost twice as high as those in other groups. The shorter MI, the lower the insertion torque, and the greater the cortical bone thickness, the greater the insertion torque. To minimize fracture risk, the size of MI should be selected according to the insertion site

Mechanical and clinical properties of titanium and titanium-based alloys (Ti G2, Ti G4 cold worked nanostructured and Ti G5) for biomedical applications

Commercially pure titanium (Ti G2 and Ti G4) and the Ti–6Al–4V (Ti G5) alloy have limitations for biomedical applications, due to either low mechanical strength (Ti G2, Ti G4) or the possible release of toxic ions (Ti G5). Since Ti alloys have a low hardening coefficient, it is very difficult to improve their mechanical properties by work hardening. The purpose of this work was to compare the mechanical and clinical properties of Ti G4 nanostructured after severe plastic deformation by ECAP (Ti G4 Hard) with those of Ti G2, Ti G4 and Ti G5. Bars, disks and dental implants made with Ti G2, Ti G4, Ti G5 and Ti G4 Hard were tested. Mechanical tests (tension, compression, hardness, elastic modulus, fatigue and torque) and roughness measurements were performed. The results of the mechanical tests showed that Ti G4 Hard has a higher mechanical strength and a lower elastic modulus than Ti G2, Ti G4 and Ti G5. Scanning electron microscopy and roughness measurements results showed that acid etched Ti G4 Hard nanostructured has better surface morphological features than Ti G2, Ti G4 and Ti G5. The clinical performances of Ti G4 and Ti G4 Hard were similar. The high mechanical strength of Ti G4 Hard means that it can be used to replace Ti G5 in several clinical applications, with the advantage of not releasing toxic ions. The Ti G4 Hard dental implants have adequate mechanical properties and can be inserted in areas with low bone volume. Keywords: Titanium, High strength cp Ti, Strain hardening, Ti nanostructured, Dental implant, ECA