Evaluation of an antibacterial orthodontic adhesive incorporated with niobium-based bioglass : an in situ study

This in situ study aimed to evaluate the antibacterial and anti-demineralization effects of an experimental orthodontic adhesive containing triazine and niobium phosphate bioglass (TAT) around brackets bonded to enamel surfaces. Sixteen volunteers were selected to use intra-oral devices with six metallic brackets bonded to enamel blocks. The experimental orthodontic adhesives were composed by 75% BisGMA and 25% TEGDMA containing 0% TAT and 20% TAT. Transbond XT adhesive (TXT) was used as a control group. Ten volunteers, mean age of 29 years, were included in the study. The six blocks of each volunteer were detached from the appliance after 7 and 14 days to evaluate mineral loss and bacterial growth including total bacteria, total Streptococci, Streptococci mutans, and Lactobacilli. Statistical analysis was performed using GLM model - univariate analysis of variance for microhardness and 2-way ANOVA for bacterial growth (p<0.05). The 20% TAT adhesive caused no difference between distances from bracket and the sound zone at 10-μm deep after 7 and 14 days. After 14 days, higher mineral loss was shown around brackets at 10- to 30-μm deep for TXT and 0% TAT adhesives compared to 20% TAT. S. mutans growth was inhibited by 20% TAT adhesive at 14 days. Adhesive with 20% TAT showed lower S. mutans and total Streptococci growth than 0% TAT and TXT adhesives. The findings of this study show that the adhesive incorporated by triazine and niobium phosphate bioglass had an anti-demineralization effect while inhibiting S. mutans and total Streptococci growth. The use of this product may inhibit mineral loss of enamel, preventing the formation of white spot lesions

Evaluation of the physicochemical and antibacterial properties of experimental adhesives doped with lithium niobate

The aim of the present study was to formulate dental adhesives with different concentrations of LiNbO3 and to evaluate their physicochemical and antibacterial properties. A dental adhesive was formulated using methacrylate monomers and photoinitiators and used as a control filler-free group. Subsequently, three experimental adhesives doped with LiNbO3 at different concentrations (1 wt.%, 2 wt.%, and 5 wt.%) were also formulated. All the experimental adhesives were assessed to evaluate the degree of conversion (DC), softening in solvent, immediate and long-term microtensile bond-strength (μ-TBS), radiopacity, ultimate tensile strength, and antibacterial activity. The incorporation of 1 wt.% of LiNbO3 had no negative effect on the DC of the adhesive resin compared to the control group (p > 0.05). We observed a decrease in the percentage of softening in solvent in the group LiNbO3 at 1 wt.% (p 0.05). After six months, the group with 5 wt.% still presented the highest μ-TBS (p 0.05). LiNbO3 was successfully incorporated in dental adhesives, increasing the radiopacity and their resistance to degradation. Although LiNbO3 offered no antibacterial properties, the reliability of LiNbO3 incorporation in the adhesive encourages new tests to better investigate the antimicrobial action of LiNbO3 through temperature variation

Nanotubos de nitreto de boro e brometo de alquil trimetil amônio como carga em um adesivo ortodôntico experimental

O objetivo do presente estudo foi formular um adesivo ortodôntico experimental com a incorporação de nanotubos de nitreto de boro (BNNTs) e brometo de alquil trimetil amônio (ATAB) como carga, e caracterizar conforme suas propriedades. Foi formulada uma resina base, composta por 75% de Bis-GMA e 25% TEGDMA, 1% mol de CQ, EDAB, DPIH, 0,01% de BHT em peso, além de 5% de sílica coloidal. Foi adicionado à resina base 0,1% BNNT (GBNNT); 0,1% ATAB (GATAB) e 0,2% BNNT/ATAB (GBNNT/ATAB), e um grupo permaneceu sem adição de carga o qual foi usado como grupo controle (GCtrl). Os grupos foram avaliados através dos testes de resistência de união ao cisalhamento (n=15), ação antimicrobiana (n=3), grau de conversão (n=3), ângulo de contato e energia livre de superfície (n=5), amolecimento em solvente (n=5), deposição mineral (n=5) e citotoxicidade (n=3). Os dados foram analisados utilizando teste t-student pareado para amolecimento em solvente e ANOVA de uma via para os outros testes, havendo diferenças entre os grupos, foi aplicado o teste de comparações múltiplas de Tukey. O nível de significância foi de 5%. Todos os grupos alcançaram valores de conversão acima de 50% e viabilidade celular superior a 90%. Os adesivos GBNNT (12,74±7,32) e GATAB (13,67±8,28) exibiram redução do amolecimento no solvente em comparação com o adesivo GCtrl. O valor médio da energia livre de superfície foi diminuído (p0,05). Teste de deposição mineral revelaram deposição de fosfato nos grupos GBNNT, GATAB e GBNNT/ATAB após 14 e 28 dias. A adição de 0,2% de BNNT/ATAB a um adesivo ortodôntico experimental é capaz de inibir o crescimento bacteriano e induzir deposição mineral sem afetar as propriedades do material.The aim of the present study was to formulate an experimental orthodontic adhesive with the incorporation of boron nitride nanotubes (BNNTs) and alkyl trimethyl ammonium bromide (ATAB) as a filler, and characterize according to its properties. A base resin composed of 75% Bis-GMA and 25% TEGDMA, 1 mol% of CQ, EDAB, DPIH, 0.01% BHT by weight, and 5% of colloidal silica was formulated. 0.1% BNNT was added to the base resin (GBNNT); 0.1% ATAB (GATAB) and 0.2% BNNT/ATAB (GBNNT/ATAB), and one group remained unfilled, which was used as the control group (GCtrl). The groups were evaluated through shear bond strength tests (n = 15), antimicrobial action (n = 3), degree of conversion (n = 3), contact angle and free surface energy (n = 5), softening in solvent (n = 5), mineral deposition (n = 5) and cytotoxicity (n = 3). The data were analyzed using paired t-student test for solvent softening and one-way ANOVA for the other tests. There were differences between groups, Tukey's multiple comparisons test was applied. The level of significance was 5%. All groups achieved conversion values above 50% and cell viability greater than 90%. GBNNT (12.74 ± 7.32) and GATAB (13.67 ± 8.28) adhesives exhibited reduced softening in solvent compared to GCtrl adhesive. The mean free surface energy was decreased (p 0,05). Mineral deposition test revealed phosphate deposition in the GBNNT, GATAB and GBNNT/ATAB groups after 14 and 28 days. The addition of 0.2% of BNNT/ATAB to an experimental orthodontic adhesive is able to inhibit bacterial growth and induce mineral deposition without affecting the properties of the material

Mineral deposition promoted by resin-based sealants with different calcium phosphate additions.

The aim of this study was to evaluate the influence of different calcium phosphates (CaPs) on the physical, biological, and remineralizing properties of experimental resin-based sealants (RBSs). Triethylene-glycol dimethacrylate (90wt%) and bisphenol A-glycidyl methacrylate (10wt%) were used to produce resin-based sealants. Hydroxyapatite (SHAp), α-tricalcium phosphate (Sα-TCP) and octacalcium phosphate (SOCP) were added to the sealants in a 10wt% concentration. One group without CaPs was used as the control group (SCG). The degree of conversion (DC) was assessed with Fourier-transformed infrared spectroscopy, whereas cytotoxicity was tested with the HaCaT keratinocyte cell line. The ultimate tensile strength (UTS) was used to assess the mechanical strength of the experimental RBSs. Sealed enamel was used for colorimetric assay. Mineral deposition was assessed with Raman spectroscopy after 7, 14, and 28 days of sample immersion in artificial saliva. Scanning electron microscopy was used to analyze the surface morphology after 28 days of immersion. The addition of 10wt% of fillers significantly reduced the DC of sealants. SOCP groups showed reduced cell viability. Higher UTS was found for Sα-TCP and SHAp. The color analysis showed that SGC and demineralized teeth presented higher mismatches with the sound tissue. Mineral deposition was observed for SHAp and Sα-TCP after 7 days, with increased phosphate content and mineral deposits for SHAp after 28 days. RBS with the addition of 10% HAp promoted increased mineralization in vitro after 28 days, and did not affect cell viability, DC, mechanical properties, or RBS color in the enamel

Cimentos a base de resina metacrilato associado ao fosfato de cálcio : propriedades biológicas

Este trabalho teve como objetivo avaliar as propriedades biológicas de cimentos experimentais a base de resina metacrilato contendo α-tricálcio fosfato (α-TCP) ou hidroxiapatita nanoparticulada (HAp) in vitro e in vivo. Para isto, os cimentos experimentais foram avaliados e comparados com AH Plus (AHP). Na etapa in vitro, os materiais foram mantidos em contato com meio de cultura por 24 horas, coletados e avaliados na concentração de 10%. Células-tronco da papila apical humana (SCAPs) foram submetidas aos ensaios de viabilidade brometo de 3-(4,5-dimetiltiazólio)-2,5-difenil tetrazólio (MTT) e sulfurodamina B (SRB) no período de 24 horas; e a bioatividade foi avaliada pela atividade da enzima fosfatase alcalina (ALP) e deposição de nódulos mineralizados pelo corante vermelho de Alizarina (AR), nos períodos de 1, 5, 10 e 15 dias. Na etapa in vivo, os materiais foram inseridos em tubos de polietileno e colocados no tecido subcutâneo de ratos para avaliação da reação inflamatória, sendo utilizado um tubo vazio como controle e avaliados os períodos de 7, 30 e 90 dias; para avaliação da deposição óssea, os cimentos α-TCP e AHP foram inseridos em cavidades confeccionadas no fêmur de ratos, sendo utilizada uma cavidade vazia como controle e avaliados os períodos de 30 e 90 dias. Para o ensaio de viabilidade e ensaios in vivo, foram utilizados os testes de Kruskal-Wallis e post hoc de Dunn; para avaliação da bioatividade in vitro foram utilizados os testes ANOVA e post hoc de Tukey (P 0,05) e o α-TCP apresentou menor resultado de viabilidade no teste MTT, sendo estatisticamente diferente dos outros (P 0.05), AHP apresentou menores valores em 5 dias (P 0.05), α-TCP, HAp e controle foram semelhantes aos 5 dias (P > 0.05), e em 10 e 15 dias, α-TCP apresentou os maiores valores, sendo diferente dos outros cimentos (P > 0.05). Na avaliação da resposta inflamatória in vivo, observou-se diminuição da inflamação e aumento de fibras colágenas em todos os grupos. Em 7 dias, α-TCP e HAp mostraram resultados semelhantes ao controle CT (P>0.05) e diferentes do AHP (P 0.05), diferindo do AHP (P 0.05), and α-TCP presented a lower viability result in MTT assay, being statistically different from the other sealers (P 0.05), AHP had the lowest values at 5 days (P 0.05), α-TCP, HAp and control were similar at 5 days (P > 0.05), and at 10 and 15 days, α-TCP presented the highest values, being different of the other sealers (P > 0.05). Regarding the evaluation of the inflammatory response in vivo, there was a decrease in inflammation and increase of collagen fibers in all groups. At 7 days, α-TCP and HAp showed similar results to the control (P > 0.05) and different from AHP (P 0.05), differing from the AHP (P < 0.05). It was concluded that the association of calcium phosphates and methacrylate resin showed good biocompatibility and bioactivity results in vitro and in vivo, presenting potential to be used as endodontic sealers in clinical practice

Heat treatment, microstructure and properties of 75Cr1 steel, for use in heavy loaded elements

This study aims to optimize the heat treatment of tool steel 75Cr1 which is used for heavy loaded elements in transmissions. A salt bath was used to quench and temper the steel at different temperatures. Mechanical tests and microstructural characterization were done to define the heat treatment parameters corresponding to the optimal performance of the elements. Optical microscopy, electron back scatter diffraction and x-ray diffraction were used to characterize the microstructure, while tensile tests and toughness tests were employed to determine the mechanical properties after different heat treatments. It was found that the yield strength decreases with increasing annealing temperature and that the toughness decreases with increasing annealing time and temperature. The changes of the mechanical properties are discussed in relation with the thermal treatment and the corresponding microstructures

Radiopaque Crystalline, Non-Crystalline and Nanostructured Bioceramics

Radiopacity is sometimes an essential characteristic of biomaterials that can help clinicians perform follow-ups during pre- and post-interventional radiological imaging. Due to their chemical composition and structure, most bioceramics are inherently radiopaque but can still be doped/mixed with radiopacifiers to increase their visualization during or after medical procedures. The radiopacifiers are frequently heavy elements of the periodic table, such as Bi, Zr, Sr, Ba, Ta, Zn, Y, etc., or their relevant compounds that can confer enhanced radiopacity. Radiopaque bioceramics are also intriguing additives for biopolymers and hybrids, which are extensively researched and developed nowadays for various biomedical setups. The present work aims to provide an overview of radiopaque bioceramics, specifically crystalline, non-crystalline (glassy), and nanostructured bioceramics designed for applications in orthopedics, dentistry, and cancer therapy. Furthermore, the modification of the chemical, physical, and biological properties of parent ceramics/biopolymers due to the addition of radiopacifiers is critically discussed. We also point out future research lacunas in this exciting field that bioceramists can explore further

Bacterial Interactions with Dental and Medical Materials

The interaction of bacteria with biomaterials’ surfaces has critical clinical implications on the development and progression of biofilm-related diseases. In this book "Bacterial Interactions with Dental and Medical Materials", encouraging findings on tissue-contacting biomaterials to control biofilms, enhanced understanding of key mechanisms, and clinical perspectives are discussed toward improving healthcare