Anaerobic adhesives effect on counter-torque of abutment screws on implants with external hexagon and conical connections: An in vitro study.

BACKGROUND: Abutment screw loosening is a common complication of implant supported prostheses, especially for single crowns. In engineering, anaerobic adhesives (AA) are used to provide chemical locking between screw surfaces, but their application in implantology remains unclear. PURPOSE: The purpose of this article is to evaluate, in vitro, the effect of AA on counter-torque of abutment screws for cemented prosthesis on dental implants with external hexagon connection (EHC) and conical connection (CC). MATERIALS AND METHODS: Sample was composed by 60 specimens, 30 dental implants with EHC and 30 with CC. Abutments (transmucosal 3 mm straight universal abutment) were installed without AA (control group) or with application of AA with two different adhesive strength: medium strength (LOCTITE® 242) and high strength (LOCTITE® 277). The specimens were subjected to mechanical cycling at 37°C, with a load setting of 133 N, a 1.3 Hz frequency, and 1 200 000 cycles. The abutments were removed, and the counter-torque values were registered. Screws and implants were inspected using a stereomicroscope to verify the presence of residual adhesive and damage the internal structures. The data were analyzed using descriptive statistics and comparison tests (p < 0.05). RESULTS: Comparing to the torque of installation, the medium strength AA kept the counter-torque values for CC implants and the high strength AA kept the counter-torque for EHC implants and increased for CC implants. In the intergroup comparisons, control group presented significantly lower counter-torque values than other groups, both for EHC and CC implants. High strength AA presented similar results to medium strength AA in the EHC implants, but in the CC implants presented higher counter-torque values. Damage in threads was more frequent in the groups that received high strength AA. CONCLUSION: The use of AA increased the counter-torque of abutment screws, both in implants with EHC and CC.

Efeito da curcumina e três análogos ­ DMAD, DMAM E RI75 ­ sobre viabilidade, diferenciação e expressão gênica em pré-osteoblastos / Effect of curcumin and three of its analogues - DMAD, DMAM and RI75 - on pre-osteoblast cells' viability, differentiation, and gene expression

A curcumina, encontrada nos rizomas da cúrcuma (Curcuma longa L.), tem sido amplamente estudada devido aos seus potenciais benefícios à saúde que, entre outros, incluem propriedades anti-inflamatórias, antioxidantes e cicatrizantes. No entanto, devido à sua baixa biodisponibilidade e farmacocinética desfavorável, compostos análogos são desenvolvidos e estudados para obter melhores características biofarmacêuticas e aumentar os efeitos biológicos. Neste trabalho, avaliamos a atividade da curcumina e três de seus análogos sintéticos (DMAD, DMAM e RI75) sobre a viabilidade e diferenciação de uma linhagem celular pré-osteoblástica (MC3T3-E1). A expressão dos genes fator de crescimento endotelial vascular (vegf), do ligante 12 da quimiocina de motivo C-X-C (cxcl12) e do fator de transcrição runt- related 2 (runx2) também foi avaliada. As células foram estimuladas com curcumina e os três análogos usando concentrações de 10, 30 ou 50 µM. A curcumina e os análogos testados apresentaram nenhuma, ligeira ou moderada citotoxicidade celular em comparação com o controle negativo, após 24, 48 e 72 horas, nas concentrações testadas. Os resultados de atividade de mineralização para a curcumina e o análogo DMAD não apresentaram diferença estatística com o grupo controle, enquanto os análogos DMAM e RI75 apresentaram menor atividade de mineralização. Nenhuma das substâncias apresentou expressão gênica diferencial de cxcl12, um ativador de células endoteliais e inflamatórias. Por outro lado, em comparação com o controle, o análogo de curcumina RI75 mostrou regulação positiva de runx2 e vegf, ambos relacionados ao reparo tecidual. Os resultados sugerem que os análogos DMAD, DMAM e RI75 apresentam citotoxicidade semelhante ou inferior à curcumina natural e maior atividade biológica, com destaque para o análogo RI75, sendo substâncias com potencial promissor para biomodificações de materiais.

Curcumin, found in the rhizomes of turmeric (Curcuma longa L.), has been widely studied due to its potential health benefits which, among others, include anti inflammatory, antioxidant and healing properties. However, due to their low bioavailability and unfavorable pharmacokinetics, analogous compounds are developed and studied to obtain better biopharmaceutical characteristics and increase biological effects. In this work, we evaluated the activity of curcumin and three of its synthetic analogues (DMAD, DMAM and RI75) on the viability and differentiation of a pre-osteoblastic cell line (MC3T3-E1). The expression of the genes vascular endothelial growth factor (vegf), C-X-C motif chemokine ligand 12 (cxcl12) and runt related transcription factor 2 (runx2) was also evaluated. Cells were stimulated with curcumin and the three analogues using concentrations of 10, 30 or 50 µM. Curcumin and the analogues tested showed no, slight or moderate cellular cytotoxicity compared to the negative control, after 24, 48 and 72 hours, at the concentrations tested. The mineralization activity results for curcumin and the DMAD analogue showed no statistical difference with the control group, while the DMAM and RI75 analogues showed lower mineralization activity. None of the substances showed differential gene expression of cxcl12, an activator of endothelial and inflammatory cells. On the other hand, compared to the control, the curcumin analogue RI75 showed upregulation of runx2 and vegf, both related to tissue repair. The results suggest that the DMAD, DMAM and RI75 analogues present similar or lower cytotoxicity compared to natural curcumin and greater biological activity, especially the RI75 analogue, being, therefore, substances with promising potential for biomodification of materials.

Koh group influence on titanium surfaces and pure sol-gel silica for enhanced osteogenic activity.

Although, the excellent level of success of titanium surfaces is based on the literature, there are some biological challenges such as unfavorable metabolic conditions or regions of poor bone quality where greater surface bioactivity is desired. Seeking better performance, we hypothesized that silica-based coating via sol-gel route with immersion in potassium hydroxide basic solution induces acceleration of bone mineralization. This in vitro experimental study coated titanium surfaces with bioactive glass synthesized by route sol-gel via hydrolysis and condensation of chemical alkoxide precursor, tetraethylorthosilicate (TEOS) and/or deposition of chemical compound potassium hydroxide (KOH) to accelerate bone apposition. The generated surfaces titanium(T), titanium with potassium hydroxide deposition (T + KOH), titanium with bioactive glass deposition synthesized by sol-gel route via tetraethylorthosilicate hydrolysis (TEOS), titanium with bioactive glass deposition synthesized by sol-gel route via tetraethylorthosilicate hydrolysis with potassium hydroxide deposition (TEOS + KOH) were characterized by 3D optical profilometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), contact angle by the sessile drop method, x-ray excited photoelectron spectroscopy (XPS) and energy dispersive x-ray spectrometer (EDX). The addition of the KOH group on the pure titanium (T) or bioactive glass (TEOS) surfaces generated a tendency for better results for mineralization. Groups covered with bioactive glass (TEOS, TEOS + KOH) tended to outperform even groups with titanium substrate (T, T + KOH). The addition of both, bioactive glass and KOH, in a single pure titanium substrate yielded the best results for the mineralization process.