Influence of standard load micro- and nanopatterned in surface roughness of bleached teeth and submitted to different surface treatments.

The aim of this study was evaluate the dental enamel after whitening treatment with Opalescence Boost PF™ 38%, correlating the structural alterations in the surface of the enamel with its respective pH and verify if whitened teeth submitted to different finishing and polishing techniques show similar surface texture to healthy teeth (control group). Sixty premolars were divided in 6 groups (n = 10), which had been immersed in artificial saliva during all the experiment. Protocol whitening was performed according to the manufacturer recommendations, and then the specimens were submitted to different polishing technique with Sof-Lex Pop On™ disks, Flex Diamond™ felt disks using two different micrometric polishing pastes (Enamelize™ and Diamond Polish™) and two nanometric polishing pastes (Lummina-E Diamond and Lummina-E Alumina), according to the groups. Representative specimens were analyzed in scanning electronic microscopy (SEM). Whitening gel used in this experiment had modified the morphologic aspect of the enamel surface. It was found that two nanometric polishing pastes (G5 and G6) promoted a less rough surface compared to control group even after the whitening process.

Prefabricated 3D-Printed Tissue-Engineered Bone for Mandibular Reconstruction: A Preclinical Translational Study in Primate.

The advent of three dimensionally (3D) printed customized bone grafts using different biomaterials has enabled repairs of complex bone defects in various in vivo models. However, studies related to their clinical translations are truly limited. Herein, 3D printed poly(lactic-co-glycolic acid)/ß-tricalcium phosphate (PLGA/TCP) and TCP scaffolds with or without recombinant bone morphogenetic protein -2 (rhBMP-2) coating were utilized to repair primate's large-volume mandibular defects and compared efficacy of prefabricated tissue-engineered bone (PTEB) over direct implantation (without prefabrication). 18F-FDG PET/CT was explored for real-time monitoring of bone regeneration and vascularization. After 3-month's prefabrication, the original 3D-architecture of the PLGA/TCP-BMP scaffold was found to be completely lost, while it was properly maintained in TCP-BMP scaffolds. Besides, there was a remarkable decrease in the PLGA/TCP-BMP scaffold density and increase in TCP-BMP scaffolds density during ectopic (within latissimus dorsi muscle) and orthotopic (within mandibular defect) implantation, indicating regular bone formation with TCP-BMP scaffolds. Notably, PTEB based on TCP-BMP scaffold was successfully fabricated with pronounced effects on bone regeneration and vascularization based on radiographic, 18F-FDG PET/CT, and histological evaluation, suggesting a promising approach toward clinical translation.

Reinforcing 13-93 bioglass scaffolds fabricated by robocasting and pressureless spark plasma sintering with graphene oxide.

13-93 bioglass (BG) scaffolds reinforced with graphene oxide (GO) were fabricated by robocasting (direct-ink-writing) technique. Composite scaffolds with 0-4 vol% content of GO platelets were printed, and then consolidated by pressureless spark plasma sintering at 650 °C. It was found that, despite hampering densification of the bioglass, the addition of GO platelets up to a certain content enhanced the mechanical performance of the 13-93 bioglass scaffolds in terms of strength and, especially, toughness. Best performance was obtained for 2 vol.% GO, which increased strain energy density (toughness) of the scaffolds by ∼894%, and their compressive strength by ∼26%. At higher contents, agglomeration of the nanoplatelets and increased porosity significantly reduced the mechanical enhancement obtained. Implications of the results on the fabrication of novel bioglass scaffolds that may find use in load-bearing bone tissue engineering applications are discussed.

Enhancing the mechanical and in vitro performance of robocast bioglass scaffolds by polymeric coatings: Effect of polymer composition.

The effect of different polymeric coatings, including natural and synthetic compositions, on the mechanical performance of 45S5 bioglass robocast scaffolds is systematically analyzed in this work. Fully amorphous 45S5 bioglass robocast scaffolds sintered at 550 °C were impregnated with natural (gelatin, alginate, and chitosan) and synthetic (polycaprolactone, PCL and poly-lactic acid, PLA) polymers through a dip-coating process. Mechanical enhancement provided by these coatings in terms of both compressive strength and strain energy density was evaluated. Natural polymers, in general, and chitosan, in particular, were found to produce the greater reinforcement. The effect of these coatings on the in vitro bioactivity and degradation behavior of 45S5 bioglass robocast scaffolds was also investigated through immersion tests in simulated body fluid (SBF). Coatings from natural polymers, especially chitosan, are shown to have a positive effect on the bioactivity of 45S5 bioglass, accelerating the formation of an apatite-like layer. Besides, most coating compositions reduced the degradation (weight loss) rate of the scaffold, which has a positive impact on the evolution of their mechanical properties.

Influence of Cervical Preflaring on the Incidence of Root Dentin Defects.

INTRODUCTION: This study evaluated the influence of cervical preflaring on the incidence of root dentin defects after root canal preparation. METHODS: Extracted human maxillary central incisors were selected and allocated to 1 control group and 12 experimental groups (n = 15). Teeth in the control group were left unprepared, whereas the others were prepared using 2 reciprocating single-file systems (Reciproc and WaveOne [WO]), 3 full-sequence rotary systems (ProTaper Universal, ProTaper Next [PTN], and ProFile), and K-files driven by an oscillatory system, with and without cervical preflaring. Roots were then horizontally sectioned at 4, 8, and 12 mm from the apex, stained with 1% methylene blue, and viewed through a stereomicroscope at ×25 magnification. Slices were inspected and the absence/presence of defects (fractures, partial cracks, and craze lines) recorded. Data were analyzed using Kolmogorov-Smirnov and Levene tests followed by the Tukey post hoc test at a significance level of P < .05. RESULTS: No root dentin defects were observed in the control group. WO was associated with a significantly higher number of defects than K-files, ProFile, and PTN (P < .05), but was not significantly different from Reciproc or ProTaper Universal (P > .05). Cervical preflaring significantly reduced the incidence of fractures and other defects in the WO and PTN groups (P < .05). CONCLUSIONS: All instruments caused root dentin defects, regardless of the enlargement or not of the cervical portion. Cervical preflaring was associated with a lower incidence of defects, mainly in root canals prepared with WO and PTN.

Fracture modes under uniaxial compression in hydroxyapatite scaffolds fabricated by robocasting.

The fracture modes of hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) are analyzed in this work. Concentrated HA inks with suitable viscoelastic properties were developed to enable the fabrication of prototype structures consisting of a 3-D square mesh of interpenetrating rods. The fracture behavior of these model scaffolds under compressive stresses is determined from in situ uniaxial tests performed in two different directions: perpendicular to the rods and along one of the rod directions. The results are analyzed in terms of the stress field calculated by finite element modeling (FEM). This analysis provides valuable insight into the mechanical behavior of scaffolds for bone tissue engineering applications fabricated by robocasting.

Case study: Reinforcement of 45S5 bioglass robocast scaffolds by HA/PCL nanocomposite coatings.

The purpose of this study is to analyze the mechanical enhancement provided by nanocomposite coatings deposited on robocast 45S5 bioglass (BG) scaffolds for bone tissue regeneration. In particular, a nanocomposite layer consisting of hydroxyapatite (HA) nanoparticles, as reinforcing phase, in a polycaprolactone (PCL) matrix was deposited onto the surface of the BG struts conforming the scaffold. Three different HA nanopowders were used in this study. The effect of particle size and morphology of these HA nanopowders on the mechanical performance of 45S5 BG scaffolds is evaluated.

Sintering and robocasting of beta-tricalcium phosphate scaffolds for orthopaedic applications.

beta-Tricalcium phosphate (beta-TCP) scaffolds with designed, three-dimensional (3-D) geometry and mesoscale porosity have been fabricated by direct-write assembly (robocasting) techniques. Concentrated beta-TCP inks with suitable viscoelastic properties were developed to enable the fabrication of the complex 3-D structures. A comprehensive study of the sintering behavior of TCP as a function of the calcium content in the starting powder was also carried out, and the optimal heat treatment for fabricating scaffolds with dense beta-TCP rods has been determined. Such analysis provides clues to controlling the microstructure of the fabricated structures and, therefore, enabling the fabrication by robocasting of TCP scaffolds with tailored performance for bone tissue engineering applications.

Understanding the role of dip-coating process parameters in the mechanical performance of polymer-coated bioglass robocast scaffolds.

The effect of different dip-coating variables-solvent, deposition temperature and polymer concentration-on the mechanical performance of polycaprolactone-coated 45S5 bioglass robocast scaffolds is systematically analyzed in this work. The reproducible geometry of the scaffolds produced by this additive manufacturing technique makes them an optimal model system and facilitates the analysis. The results suggest that the mechanical performance of the hybrid scaffolds is improved monotonically with polymer concentration, but this concentration cannot be increased indefinitely if the macroporosity interconnectivity, and thus the scaffold׳s capacity to promote tissue ingrowth, are to be preserved. An optimal concentration, and therefore viscosity (~1-4Pas in the present case), exists for any given set of process variables (scaffold geometry and material, polymer, solvent and process temperature) that yields coatings with optimal reinforcement and minimal reduction of scaffold functionality. Solvent and process temperature do not directly affect the strengthening provided by the polymeric coating. However they can determine the maximum concentration at the critical viscosity, and thereby the maximum achievable mechanical performance of the resulting hybrid scaffold.

The Influence of Cervical Preflaring on the Amount of Apically Extruded Debris after Root Canal Preparation Using Different Instrumentation Systems.

INTRODUCTION: The objective of this study was to evaluate the influence of cervical preflaring on the amount of apically extruded debris after root canal preparation using different instrumentation systems. METHODS: One hundred eighty human maxillary central incisors were selected and randomly divided into 12 groups (n = 15). Root canals were instrumented according to manufacturers' instructions using 2 reciprocating single-file systems (Reciproc [VDW, Munich, Germany] and WaveOne [Dentsply Maillefer, Ballaigues, Switzerland]), 3 full-sequence rotary systems (ProTaper Universal [Dentsply Maillefer], ProTaper Next [Dentsply Tulsa Dental, Tulsa, OK], and ProFile [Dentsply Maillefer]), and K-files (Dentsply Maillefer) driven by an oscillatory system with and without cervical preflaring. Bidistilled water was used as irrigant. Apically extruded debris was collected in preweighed glass vials using the Myers and Montgomery method. After drying, the mean weight of debris was determined using a microbalance. Kolmogorov-Smirnov and Levene tests followed by the Tukey post hoc test were used for statistical analysis. RESULTS: K-files produced significantly more debris than all of the other systems (P < .05). For all systems, cervical preflaring reduced the amount of apically extruded debris when compared with no cervical preflaring (P < .05). CONCLUSIONS: All of the systems extruded debris, irrespective of the preparation technique used (with or without cervical preflaring). Cervical preflaring was associated with the extrusion of smaller quantities of apical debris.

Fracture of ceramic/ceramic/polymer trilayers for biomechanical applications.

Fracture damage in trilayers consisting of outer and inner brittle layers bonded to a compliant (polycarbonate) substrate and subjected to concentrated surface loading is analyzed. The principal mode of fracture is radial cracking at the undersurface of the inner (core) layer, even in the strongest of core ceramics--other damage modes, including radial cracking in the outer (veneer) layer, are less invasive in these all-brittle coating systems. Tests on simple trilayer structures fabricated from glasses, sapphire, and dental ceramics are used to examine the dependence of the critical load for radial fracture in terms of relative outer/inner layer thickness and modulus, and inner layer strength. An explicit relation for the critical load, based on a flexing plate model in which the outer/inner bilayer is reduced to an "equivalent" monolithic coating with "effective" composite modulus, is used to examine these dependencies. The theoretical relation describes all the major trends in the critical load data over a broad range of variables, thus providing a sound basis for trilayer design. Relevance of the analysis to dental crowns and other biomechanical applications is a central theme of the study.

Reinforcing bioceramic scaffolds with in situ synthesized ε-polycaprolactone coatings.

In situ ring-opening polymerization of ε-caprolactone (ε-CL) was performed to coat ß-tricalcium phosphate (ß-TCP) scaffolds fabricated by robocasting in order to enhance their mechanical performance while preserving the predesigned macropore architecture. Concentrated colloidal inks prepared from ß-TCP commercial powders were used to fabricate porous structures consisting of a three-dimensional mesh of interpenetrating rods. Then, ε-CL was in situ polymerized within the ceramic structure using a lipase as catalyst and toluene as solvent, to obtain a highly homogeneous coating and full impregnation of in-rod microporosity. The strength and toughness of scaffolds coated by ε-polycaprolactone (ε-PCL) were significantly increased (twofold and fivefold increase, respectively) over those of the bare structures. Enhancement of both properties is associated to the healing of preexisting microdefects in the bioceramic rods. These enhancements are compared to results from previous work on fully impregnated structures. The implications of the results for the optimization of the mechanical and biological performance of scaffolds for bone tissue engineering applications are discussed.

Impregnation of ß-tricalcium phosphate robocast scaffolds by in situ polymerization.

Ring-opening polymerization of ε-caprolactone (ε-CL) and L-lactide (LLA) was performed to impregnate ß-tricalcium phosphate (ß-TCP) scaffolds fabricated by robocasting. Concentrated colloidal inks prepared from ß-TCP commercial powders were used to fabricate porous structures consisting of a 3D mesh of interpenetrating rods. ε-CL and LLA were in situ polymerized within the ceramic structure by using a lipase and stannous octanoate, respectively, as catalysts. The results show that both the macropores inside the ceramic mesh and the micropores within the ceramic rods are full of polymer in either case. The mechanical properties of scaffolds impregnated by in situ polymerization (ISP) are significantly increased over those of the bare structures, exhibiting similar values than those obtained by other, more aggressive, impregnation methods such as melt-immersion (MI). ISP using enzymatic catalysts requires a reduced processing temperature which could facilitate the incorporation of growth factors and other drugs into the polymer composition, thus enhancing the bioactivity of the composite scaffold. The implications of these results for the optimization of the mechanical and biological performance of scaffolds for bone tissue engineering applications are discussed.

Biological properties of solid free form designed ceramic scaffolds with BMP-2: in vitro and in vivo evaluation.

Porous ceramic scaffolds are widely studied in the tissue engineering field due to their potential in medical applications as bone substitutes or as bone-filling materials. Solid free form (SFF) fabrication methods allow fabrication of ceramic scaffolds with fully controlled pore architecture, which opens new perspectives in bone tissue regeneration materials. However, little experimentation has been performed about real biological properties and possible applications of SFF designed 3D ceramic scaffolds. Thus, here the biological properties of a specific SFF scaffold are evaluated first, both in vitro and in vivo, and later scaffolds are also implanted in pig maxillary defect, which is a model for a possible application in maxillofacial surgery. In vitro results show good biocompatibility of the scaffolds, promoting cell ingrowth. In vivo results indicate that material on its own conducts surrounding tissue and allow cell ingrowth, thanks to the designed pore size. Additional osteoinductive properties were obtained with BMP-2, which was loaded on scaffolds, and optimal bone formation was observed in pig implantation model. Collectively, data show that SFF scaffolds have real application possibilities for bone tissue engineering purposes, with the main advantage of being fully customizable 3D structures.

Improving the compressive strength of bioceramic robocast scaffolds by polymer infiltration.

The effect of polymer infiltration on the compressive strength of ß-tricalcium phosphate (TCP) scaffolds fabricated by robocasting (direct write assembly) is analyzed in this work. Porous structures consisting of a tetragonal three-dimensional mesh of interpenetrating rods were fabricated from concentrated TCP inks with suitable viscoelastic properties. Biodegradable polymers (polylactic acid (PLA) and poly(ε-caprolactone) (PCL)) were infiltrated into selected scaffolds by immersion of the structure in a polymer melt. Infiltration increased the uniaxial compressive strength of these model scaffolds by a factor of three (PCL) or six (PLA). It also considerably improved the mechanical integrity of the structures after initial cracking, with the infiltrated structure retaining a significant load-bearing capacity after fracture of the ceramic rods. The strength improvement in the infiltrated scaffolds was attributed to two different contributions: the sealing of precursor flaws in the ceramic rod surfaces and the partial transfer of stress to the polymer, as confirmed by finite element analysis. The implications of these results for the mechanical optimization of scaffolds for bone tissue engineering applications are discussed.

Finite element modeling as a tool for predicting the fracture behavior of robocast scaffolds.

The use of finite element modeling to calculate the stress fields in complex scaffold structures and thus predict their mechanical behavior during service (e.g., as load-bearing bone implants) is evaluated. The method is applied to identifying the fracture modes and estimating the strength of robocast hydroxyapatite and beta-tricalcium phosphate scaffolds, consisting of a three-dimensional lattice of interpenetrating rods. The calculations are performed for three testing configurations: compression, tension and shear. Different testing orientations relative to the calcium phosphate rods are considered for each configuration. The predictions for the compressive configurations are compared to experimental data from uniaxial compression tests.

Mechanical properties of calcium phosphate scaffolds fabricated by robocasting.

The mechanical behavior under compressive stresses of beta-tricalcium phosphate (beta-TCP) and hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) technique is analyzed. Concentrated colloidal inks prepared from beta-TCP and HA commercial powders were used to fabricate porous structures consisting of a 3-D tetragonal mesh of interpenetrating ceramic rods. The compressive strength and elastic modulus of these model scaffolds were determined by uniaxial testing to compare the relative performance of the selected materials. The effect of a 3-week immersion in simulated body fluid (SBF) on the strength of the scaffolds was also analyzed. The results are compared with those reported in the literature for calcium phosphate scaffolds and human bone. The robocast calcium phosphate scaffolds were found to exhibit excellent mechanical performances in terms of strength, especially the HA structures after SBF immersion, indicating a great potential of this type of scaffolds for use in load-bearing bone tissue engineering applications.

Efecto de la inducción de enfermedad endodóntica sobre el sistema nervioso central (SNC): estudio en ratones / Effect of endodontic disease induction on the central nervous system (CNS): a study in mice

El objetivo de este estudio fue comprender el efecto de la infección periapical asociada a un modelo de estrés sobre los parámetros de evaluación del sistema nervioso central. Para este experimento se seleccionaron 20 ratones machos de la especie Rattus Novergicus en dos grupos, respectivamente, de estrés y apertura (GEA) y apertura (GA). Los procedimientos de inducción de la enfermedad endodóntica se realizaron por medio de una apertura coronaria del 1º molar inferior derecho. Después de la institución del modelo de estrés fue realizada la evaluación motora y psicológica de los animales por medio de pruebas de comportamiento del tipo laberinto elevado en forma de cruz y campo abierto. En relación a la evaluación en el campo abierto no existieron diferencias estadísticas (p>0,05) entre los grupos. Para la evaluación del laberinto en cruz, fueron observadas dos variables. En relación al tiempo de permanencia en el brazo cerrado el GA demostró un mayor tiempo de permanencia comparado al GEA (p<0,05). En relación al brazo abierto, el GEA tuvo un tiempo mayor de permanencia en la región en comparación al GA, inclusive con diferentes estadísticas (p<0,05). Dentro de las limitaciones del estudio, se puede notar que el estrés asociado a la inflamación de los tejidos periapicales llevaron a la modificación del comportamiento del animal.

The aim of this study was to understand the effect of periapical infection associated with a model of stress on the parameters of the central nervous system evaluation. For this experiment we selected 20 male rats divided into two groups: stress and opening group (SOG) and opening group (OG). In the first group, rats were tested for induction of stress associated with endodontic disease through coronary opening of the first lower right molar, the second group, the same procedure was carried out but without the stress partner. After 30 days of the imposition of the stress model was evaluated for motor and mental development of animals through field testing of high-maze behavior in a cross and open. Regarding the open-field assessment there was no statistically significant differences (p> 0.05) for the evaluation of the maze, there are two variables. In terms of time spent in closed arm OG showed a longer hospital stay compared to SOG (p <0.05). Regarding the open design industry, the SOG had a longer hospital stay in the region against the OG, including statistically significant differences (p <0.05). It was seen that the stress associated with inflammation of periapical tissues led to the modification of animal behavior.

Effect of two models of stress associated with ligature-induced periodontitis on hematological parameters in rats / Efeito de dois modelos de estresse associados à periodontite induzida por ligadura sobre parâmetros hematológicos em ratos

Purpose: To evaluate the effect of two models of chronic stress in rats and their association with induced periodontitis on hematological parameters: mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), hematocrit (Ht), erythrocytes (Hm), hemoglobin (Hg) and leukocytes (Lk). Methods: Forty-eight adult Wistar rats were randomly distributed into four groups (n=12): physical stress (PSG), variable stress (VSG), ligature (LG) and control (CG) and then started the test of physical stress (restraint and exposure to cold) and variable stress (exposure to flashing light, isolation, examination of the oral cavity, congested environment, the smell of blood and noise). After 10 days of the stress test, the animals in Groups PS, VS and L were anesthetized, and a silk thread was adapted around the upper right second molar; subsequently, the stress test continued for 50 days. The animals were anesthetized and held up the incision and visualization of the posterior vena cava for blood puncture vacuum in tubes containing EDTA. Data were collected by blinded and trained examiners and were statistically analyzed by means of ANOVA and Bonferroni?s test at the significance level of 0.05. Results: The two models of stress changed all of the hematological parameters tested, with the exception of VCM. Conclusion: The stress associated with periodontitis is able to modify blood parameters in rats.

Objetivo: Avaliar o efeito de dois modelos de estresse crônico - físico e variável - em ratos, associados à periodontite induzida, sobre parâmetros hematológicos: volume corpuscular médio (VCM), hemoglobina corpuscular média (HCM) e concentração hemoglobínica corpuscular média (CHCM) hematócrito (Ht), hemácias (Hm), hemoglobina (Hg) e leucócitos (Lc). Metodologia: Selecionaram-se 48 ratas adultas da linhagem Wistar divididas aleatoriamente em 4 grupos (n=12): estresse físico (GEF), estresse variável (GEV), ligadura (GL) e controle (GC). Iniciou-se o ensaio de estresse físico (contenção e exposição ao frio) e estresse variável (exposição à luz piscante, isolamento, exame da cavidade bucal, ambiente congestionado, odor de sangue e barulho). Decorridos 10 dias do início do ensaio de estresse, os animais dos Grupos EF, EV e L foram anestesiados e um fio de seda foi adaptado em volta do segundo molar superior direito, sendo o ensaio de estresse mantido por mais 50 dias. Os animais foram anestesiados e procedeu-se a incisão e visualização da veia cava posterior. Realizou-se a punção sanguínea a vácuo, em tubos com EDTA. Os dados foram coletados por examinadores cegos e treinados e analisados por ANOVA e teste de Bonferroni, ao nível de significância de 0,05. Resultados: Os dois modelos de estresse alteraram todos os parâmetros hematológicos do estudo com exceção do VCM. Conclusão: O estresse associado à periodontite é capaz de modificar parâmetros sanguíneos em ratas.