Nanohybrid Composite Resin Research Articles

Mechanical Properties of Nanohybrid Resin Composites Containing Various Mass Fractions of Modified Zirconia Particles.

PurposeThe aim of this study was to investigate the effect of various mass fractions of 10-methacry-loyloxydecyl dihydrogen phosphate (MDP)-conditioned or unconditioned zirconia nano- or micro-particles with different initiator systems on the mechanical properties of nanohybrid resin composites.MethodsBoth light-cured (L) and dual-cured (D) resin composites were prepared. When the mass fraction of the nano- or micro-zirconia fillers reached 55 wt%, resin composites were equipped with dual-cured initiator systems. We measured the three-point bending-strength, elastic modulus, Weibull modulus and translucency parameter of the nanohybrid resin composites containing various mass fractions of MDP-conditioned or unconditioned zirconia nano- or micro-particles (0%, 5 wt%, 10 wt%, 20 wt%, 30 wt% and 55 wt%). A Cell Counting Kit (CCK)-8 was used to test the cell cytotoxicity of the experimental resin composites. The zirconia nano- or micro-particles with MDP-conditioning or not were characterized by transmission electron microscopy (TEM), Fourier infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS).ResultsResin composites containing 5–20 wt% MDP-conditioned or unconditioned nano-zirconia fillers exhibited better three-point bending-strength than the control group without zirconia fillers. Nano- or micro-zirconia fillers decreased the translucence of the nanohybrid resin composites. According to the cytotoxicity classification, all of the nano- or micro-zirconia fillers containing experimental resin composites were considered to have no significant cell cytotoxicity. The FTIR spectra of the conditioned nano- or micro-fillers showed new absorption bands at 1719 cm−1 and 1637 cm−1, indicating the successful combination of MDP and zirconia particles. The XPS analysis measured Zr–O–P peak area on MDP-conditioned nano- and micro-zirconia fillers at 39.91% and 34.89%, respectively.ConclusionNano-zirconia filler improved the mechanical properties of nanohybrid resin composites, but cannot be the main filler to replace silica filler. The experimental dual-cured composites can be resin cements with better opacity effects and a low viscosity.

THE EFFECT OF THE ACIDITY OF FERMENTED MILK AGAINST THE HARDNESS OF NANOHYBRID COMPOSITE RESIN

Background : The hardness of nanohybrid composite resin can decrease due to the acidic condition of the oral cavity. The acidic condition of the oral cavity can cause continuous degradation in composite resin. Fermented milk is a beverage that is widely sold in the market and is good for consumption however this beverage has the acid potential of hydrogen (pH) which can reduce the composite resin toughness. Aim : To determine the acidity effect of fermented milk on the hardness of nanohybrid composite resin. Method: Experimental study with a post test control group design. There were 27 samples of nanohybrid composite resin. One time immersion for three seconds in each group of beverages namely Milk, Cimory, and Yakult. After 15 days, a composite resin hardness test was performed using a Micro Vickers Hardness Tester with a load of 100 grams for 10 seconds. Statistical tests using One Way ANOVA. Results: The nanohybrid composite resin exhibited significant reduction in hardness between three beverage groups. Post hoc LSD test showed that there were significant differences between Milk with Yakult (p = 0.006) and Cimory with Yakult (p = 0.008) while Milk with Cimory (p = 0.907) did not have significant. Conclusions : There is a effect of fermented milk influences the hardness. There is a significant difference between Milk and Yakult and between Cimory and Yakult and there is no significant difference between Milk and Cimory.

Adherence of Streptococcus mutans to Nanoceramic and Nanohybrid Resin Composites: An In vitro Study

Streptococcus mutans (S. mutans) is one of the cariogenic microorganisms. The restorative materials which harbor a biofilm with high number of S. mutans can accelerate the occurrence of dental caries. The purpose of this study was to evaluate the adherence of S. mutans to nanoceramic and nanohybrid resin composites. Fifteen discs of each material (Nanohybrid resin composite, Nanoceramic resin composite) were prepared, polished, and sterilized in a gamma radiation chamber. Specimens were exposed to the S. mutans bacterial suspension (0.5 McFarland) and were incubated for 4 hours. Specimens were rinsed and sonicated in normal saline, 10 μl of the obtained suspension was cultured in a sterile blood agar medium. After 24 hours, the number of colony forming units of S. mutans was counted. A sterility test control was considered for each group of materials. The data was analyzed by Independent t test. The means and standard deviations of the logarithmic counts of the colonies on the surfaces of nanohybrid resin composites and nanoceramic resin composite were equal to 3.2±0.87 and 2.8±0.324 respectively. Ceram X Universal did not show any significant difference in the bacterial adhesion compared to Filtek Z350XT. Both composites showed similar behaviour in terms of S. mutans colonization in a simple biofilm formation model.

Effect of Different Polishing Systems on the Surface Roughness and Gloss of Novel Nanohybrid Resin Composites.

Objectives To evaluate the surface roughness and gloss of three nanohybrid resin composites after polishing with three different polishing systems. Materials and Methods A total number of 112 disc specimens (10 × 3 mm) were prepared from nanohybrid—Empress Direct (ID), Grandio (GR), Filtek Z350 (Z350) and a microhybrid resin composite restorative materials—Filtek Z250 (Z250). Following 24-hour storage in 37°C distilled water, each composite group ( n = 28) was assigned into four groups ( n = 7) according to finishing/polishing (F/P) system: Mylar strip, Optrapol, Politip, and Sof-Lex (SL). The surface roughness (Ra, mm) was measured by a novel three-dimensional method using an image analysis software attached to an environmental scanning electron microscope. A glossometer was used to measure the surface gloss. Results Statistical analysis used was ANOVA test. Two-way Anova test revealed that the “type of composite” and “F/P techniques” had a significant effect on both surface roughness and gloss of the tested resin composite materials ( p < 0.05). Tukey’s post hoc test showed that ID, GR, and Z350 revealed lower surface roughness and higher surface gloss than Z250 within the same polishing system ( p < 0.05). Sof-Lex polishing discs produced the lowest surface roughness and highest surface gloss values compared with Optrapol and Politip ( p < 0.05). Conclusion The tested F/P systems provided comparable surface roughness and gloss for nanohybrid composites. The Sof-Lex system provided the best surface roughness and gloss for nanohybrid composites.

Reanatomização estética do sorriso com auxílio de elásticos separadores: relato de caso

A diferença de tamanho, as variações na forma bem como a permanência dos diastemas nos dentes anteriores em pacientes adultos promovem alterações que muitas vezes se destacam negativamente na face. O objetivo deste estudo é apresentar um relato de caso clínico cujos diastemas foram reanatomizados por técnica restauradora direta e elástico separador, com clareamento dental prévio. Paciente do sexo feminino, 37 anos, compareceu à Escola Policlínica da Faculdade Patos de Minas (FPM) insatisfeita com o sorriso devido à cor e aos espaços entre os dentes. O tratamento pode depender da estética do paciente, da condição socioeconômica, da funcionalidade mastigatória, disponibilidade e da capacidade do profissional para realizar a tarefa. O clareamento dental foi proposto para resolver a queixa em relação à cor do dente. Posteriormente, para melhor proporção de tamanho entre os incisivos centrais, foi realizada movimentação com elásticos ortodônticos para melhor distribuição dos diastemas entre os centrais. Foi utilizada uma resina composta nanohíbrida. Esse método oferece, além do menor custo, a reversibilidade, a possibilidade de reparo e menor tempo na execução por não apresentar a fase laboratorial. Assim, o tratamento foi bem aceito e foi capaz de proporcionar satisfação à paciente, pois contribuiu para a melhora de sua autoestima e aceitação social.

Avaliação da rugosidade superficial de uma resina composta com uso de diferentes polidores

Introdução: A rugosidade superficial é definida pela superfície de um material restaurador após as etapas de acabamento e polimento, e é afetada pelas propriedades do compósito resinoso, bem como pelos instrumentos utilizados para a realização do polimento. Objetivos: Avaliar a rugosidade superficial de uma resina composta nano-híbrida polida com diferentes sistemas de polimento por Microscopia de Força Atômica (MFA) e análise dos polidores por Microscopia Eletrônica de Varredura (MEV). Materiais e métodos: Os fatores em estudo são os sistemas de polimento em três níveis: Enhance (Dentsply), Ultra-Gloss (American Burrs) e Dura-Gloss (American Burrs). As unidades experimentais são formadas por 30 corpos de prova em resina composta convencional nano-híbrida, divididos aleatoriamente em 3 grupos (n=10). O Grupo G1 recebeu tratamento com o sistema de polimento de uma única etapa: Dura-Gloss; o Grupo G2, sistema de polimento de múltiplas etapas: Ultra-Gloss; e o Grupo G3 recebeu o tratamento com o sistema de polimento de uma única etapa: Enhance. A variável de resposta quantitativa se dá pela rugosidade superficial avaliada pela Microscopia de Força Atômica (MFA). Resultados: Os resultados obtidos demonstram que os sistemas de polidores Dura-Gloss e Ultra-Gloss apresentaram rugosidade superficial similar entre si (p=0,201) e diferiram estatisticamente do sistema Enhance (p=0,023, Ultra-Gloss e p=0,000, Dura-Gloss), o qual apresentou maior rugosidade superficial para a resina composta nano-híbrida. Conclusão: Os polidores Dura-Gloss e Ultra-Gloss tem maior capacidade de polimento da resina composta nano-hibrida.

Effect of Different Finishing and Polishing Techniques on Surface Roughness of Two Universal Nanohybrid Composite Resins

AIM: This study investigated the effect of different finishing and polishing systems on surface roughness of two types of universal nanohybrid composite resins.&#x0D; MATERIALS AND METHODS: A total number of 40 samples will be prepared to form two main equal groups of specimens (n = 20), according to the composite resin materials. Two universal nanohybrid resin composites were used in this study. First group (A1) is a universal nanohybrid composite resin (Mosaic) and the second group (A2) is a universal nanohybrid composite resin (Harmonize). Each group was subdivided equally into four equal subgroups (n = 5), according to the used finishing and polishing systems. Mold was made to prepare the specimens with a central hole of 4 mm in diameter and 4 mm in thickness. Light curing tip was placed touching the glass slab for 20 s then the cured specimens were removed from the mold and the specimens immediately and immersed in distilled water at 37°C for 24 h. Surface roughness (Ra) was measured using light sectioning vision system. SEM was done to support the results.&#x0D; RESULTS: The results showed that the lowest (Ra) values were recorded by the specimens under Myler strip followed by Polishing Discs treated specimens followed by Diacomp Plus specimens and the highest (Ra) values were recorded by white polishing stone specimens and regardless to finishing or polishing, it was found that mosaic resin composites group recorded statistically significant (p &lt; 0.05) lower roughness mean value than Harmonize resin composites group. p ≤ 0.05 is statistically significant in all tests.&#x0D; CONCLUSION: Achieving long-lasting esthetics in resin composites restorations needs special attention for obtaining optimal resin polymerization and a perfect surface finish using the appropriate finishing and polishing system.

Evaluation of the response of esthetic restorative materials to ultraviolet aging

Statement of problemThe optical properties of esthetic computer-aided design and computer-aided manufacturing (CAD-CAM) materials can change depending on the clinical situation. Studies that compare esthetic CAD-CAM materials based on their optical properties are lacking. PurposeThe purpose of this in vitro study was to evaluate the optical properties of esthetic CAD-CAM specimens after ultraviolet (UV) aging based on the type and thickness of the material. Material and methodsIn total, 240 plate-shaped specimens (14×12×1 mm and 14×12×2 mm) of a nanohybrid composite resin (Tetric CAD), a fine-structure feldspathic ceramic (Vitablocs Mark II), 2 different glass-ceramics (IPS Empress CAD and IPS e.max CAD), a zirconia-reinforced lithium silicate glass-ceramic (Celtra Duo), a polymer-infiltrated ceramic network (Vita Enamic), and 2 different resin nanoceramics (Cerasmart and Lava Ultimate) were fabricated (n=15). The optical parameters were analyzed by spectrophotometry before and after UV aging. The brightness (L∗), red green (a∗), yellow-blue (b∗), chroma (Ch), and hue (h) were measured, and the color difference (ΔE00) values were calculated. The translucency parameter (TP), total transmittance (Tt), and contrast ratio (CR) were also determined. Statistical analyses were performed with 1-way ANOVA, the Tukey honestly significant difference post hoc test, independent- and paired-samples t tests, and 2-way ANOVA (α=.05). ResultsSignificant interactions were observed for the aging process, material type, and thickness for all optical parameters (P<.05). L∗, TP, and Tt had lower values, while CR had higher values for the aging group than that of the control group (P<.05). The h, TP, and Tt values were higher, whereas the b∗ and CR values were lower for the 1-mm group than those of the 2-mm group (P<.05). The highest ΔE00 value was found in the Lava Ultimate 1-mm group (ΔE00=3.21) and 2-mm group (ΔE00=2.42). The lowest ΔE00 value was found in the Vitablocs Mark II 1-mm group (ΔE00=0.31). The highest TP and Tt and the lowest CR values were observed for Tetric CAD; the lowest TP and Tt, and the highest CR values were noted in Celtra Duo (P<.05). ConclusionsThe optical properties of the CAD-CAM specimens were affected by the aging process, material type, and thickness, and the color stability was clinically applicable in all CAD-CAM materials except groups Lava Ultimate and Cerasmart(ΔE00<2.25). Resin nanoceramics exhibited the greatest color changes after UV aging, and a 2-mm thickness is recommended to ensure acceptable color stability. The zirconia-reinforced lithium silicate glass-ceramic was the most opaque, with a 1-mm thickness providing increased translucency.

The effects of activated charcoal and calcium carbonate based toothpastes on surface properties of composite resin restorative materials.

Objectives: The aim of the study was to evaluate, in vitro, the surface roughness and microhardness of two different composite resin materials submitted to simulated tooth brushing with activated charcoal and calcium carbonate toothpastes. Materials and Methods: Microfilled (Heliomolar) and nanohybrid (Tg-nanohybrid) composite resins were studied, 30 disc-shaped specimens were prepared from each composite, then divided to 3 groups (n=10); group A (control group): brushed with distilled water, group B: brushed with Perfect white (Black)® toothpaste group, and group C: brushed with Depurdent® toothpaste, with a powered toothbrush for 30 seconds daily for 7 days. Vickers Microhardness was measured at 10N load and the surface roughness was measured using a surface roughness tester, SEM examination of some selected samples after brushing was conducted. Two-way analysis of variance (ANOVA) and Kruskal-Wallis were used to analyze the data with 5% level of significance between the means of tested groups. Results: The two composites showed significant increase in surface roughness after brushing in all groups, the highest values occurred in nanohybrid/Depurdent group, while the lowest values were in microfilled/control group. Microhardness increased significantly in nanohybrid/Depurdent group and decreased in microfilled/Depurdent group, while no significant change in microhardness was noted after brushing with Perfect white (Black) in both composites compared to the control group. Conclusion The tested dentifrices significantly influenced the surface roughness and microhardness of microfilled and nanohybrid composite resins.

Comparative evaluation of mechanical properties of three resin composite materials with different filler particle sizes

Aim: The aim of this study was to evaluate and compare the mechanical properties of three resin composites core materials with different filler particle sizes. Materials and methods: nanofilled (Filtek Z350 XT , 3M, ESPE USA), microhybrid (Te Econom, Ivoclar, Vivadent, India) and nanohybrid (Nexcomp, Meta biomed, korea) resin composites were used during this study. Mechanical properties regarding the compressive strength, diametral tensile strength and surface hardness were tested and results were collected and evaluated. Data were statistically analyzed using one-way Analysis of Variance and Tukey HSD test. Results: The nanofilled type revealed the highest significant compressive and diametral tensile strength values while the nanohybrid type showed the least significant hardness values among the results of the two types of composite resin for the three tests. Conclusions: after evaluation it was shown that the tested nanofilled resin composite type is more appropriate for use as core material compared to the other tested types.

Non-silicate nanoparticles for improved nanohybrid resin composites

ObjectiveZirconia and alumina nanoparticles were coated with a silica-rich layer (ALSI and ZRSI) and used to prepare experimental nanohybrid resin composites, which were characterized and compared to a control commercial resin composite (Filtek Z350 XT). MethodsSilica nanoparticles with sizes compatible to ALSI (Aerosil 150) and ZRSI (Aerosil OX 50) were tested as references. The volume of nanoparticles was equivalent across the composites, which also had consistent content of glass microparticles. CC conversion, viscosity, depth of cure, surface topography, hardness, opacity, radio-opacity, and edge chipping resistance (ReA) were tested after 24 h. Flexural strength (σf) and fracture toughness (KIC) were also tested after 15 K thermal cycles. Data were analyzed using one-way or two-way ANOVA and Tukey’s test (α = 0.05). ResultsALSI and ZRSI yielded resin composites with lower viscosity and more irregular nanoagglomerates compared to nanosilica-based composites. CC conversion and depth of cure were lower for ZRSI composite, which had higher opacity, radio-opacity, and hardness. ReA was higher for ALSI composite. Composites with ALSI and ZRSI showed stable σf after aging, whereas the control and Aerosil 150 resin composites showed significant degradation. The commercial and nanosilica-based composites showed up to 42% reduction in KIC after aging, whereas resin composites with ZRSI and ALSI showed a more stable KIC. SignificanceALSI and ZRSI generated nanohybrid resin composites with improved and/or more stable physical properties compared with nanosilica-based and commercial composites. This study suggests that changing the composition of nanofillers is a simple method to enhance the performance of nanohybrid composites.

The influence of the restorative material on the mechanical behavior of screw-retained hybrid-abutment-crowns

BackgroundThe use of polymers in implant dentistry is gaining popularity, as they might have several advantages due to their shock absorption capacity. PurposeThe aim of this study was to evaluate the performance and fracture strength of three resilient shock-absorbing polymer-based materials as well as the widely used ceramics as one-piece screw-retained implant-supported hybrid-abutment-crowns. Materials and methodsForty custom-made CAD/CAM one-piece screw-retained restorations were milled out of 5 different monolithic materials (n = 8); Z: 3Y-TZP zirconia, L: lithium disilicate, P: ceramic-reinforced polyetheretherketone (PEEK), C: nano-hybrid composite resin and E: polymer-infiltrated ceramic-network. Specimens were subjected to dynamic loading for 1,200,000 cycles with integrated thermal cycling. The surviving specimens were subjected to quasi-static loading until failure. Shapiro-Wilk test was used to test for normality, and Levene test was conducted to test the homogeneity of variance. One-way ANOVA test followed by Tukey's post-hoc test were used to detect statistically significant differences between groups. ResultsAll specimens withstood 1,200,000 cycles of thermo-dynamic loading with no signs of cracks or screw loosening. The median values of fracture strength varied from a minimum of 670 N for group E to a maximum of 2645 N for group Z. ConclusionsFracture strength of screw-retained hybrid-abutment-crowns is influenced by the material used. Zirconia showed superior results. However, its fracture strength was comparable to that of PEEK, which additionally enjoys a shock absorbing property.

COMPARISON OF VOLUMETRIC SHRINKAGE OF COMPOSITE RESIN NANOCERAMIC AND NANOFILLER

Objective: The main cause of failure of composite resin restorations is volumetric shrinkage. The aim of this study was to analyze and comparevolumetric shrinkage in nanohybrid and nanoceramic composite resins.Methods: A total of 32 (3 cm×3 cm× 2 mm) cavities were analyzed for volume using micro-CT. The samples were divided randomly into two groups: 16 cavities that were restored using nanohybrid composite resin and 16 cavities that were restored using nanoceramic composite resin. The composite resin volume was analyzed using micro-CT.Results: The difference in volumetric shrinkage between nanohybrid composite resin 245,866.5 mm3 (3%) and nanoceramic composite resin 3,470,175.13 mm3 (5%) was not significant (p=0.585).Conclusion: Nanohybrid and nanoceramic composite resins have the same volumetric shrinkage rate.

The Effects of Mouthwashes on the Color Stability of Resin-Based Restorative Materials

Objective: This study investigated the effects of three types of mouthwash on the color stability of three resin-based restorative materials (nanohybrid resin composite, sonic-activated bulk-fill material, and compomer). Materials and Methods: To this end, 120 cylindrical disc specimens were prepared and polished, after which they were incubated in distilled water for 24 hours for post-polymerization. The baseline color values of each specimen were measured with a spectrophotometer, then the specimens were randomly divided into four groups. Following immersion in the mouthwashes for 24 hours, the specimens were rinsed with distilled water and dried before the color measurement was repeated. The values of color change (∆E₀₀) were subsequently calculated. A two-way analysis of variance and Duncan’s post hoc multiple comparison tests were conducted to determine statistically significant differences among the restorative materials. Results: All samples showed discoloration after immersion, albeit some instances of discoloration were imperceptible. In this respect, a statistically significant difference was found among the restorative materials and mouthwashes (p&lt;0.05). Imperceptible ∆E₀₀ values were derived on the nanohybrid resin composite and compomer, but perceptible and acceptable ∆E₀₀ values were detected on the sonic-activated bulk-fill materials (p&lt;0.05). The clinically unacceptable discoloration was observed on the sonic-activated bulk-fill composite immersed in Listerine®. Conclusions: Clinicians should make recommendations based on the potential staining capacity of mouthwashes prescribed for daily use in restorative materials. In this way, the need for renewal of restorations due to discoloration could be avoided.

Effect of surface treatments on repair strength, roughness and morphology in aged metal-free crowns

Aim: The roughness and micromorphology of various surface treatments in aged metal-free crowns and the bond strength of these crowns repaired with composite resin (CR) was evaluated in vitro. Methods: A CR core build-up was confectioned in 60 premolars and prepared for metal-free crowns. Prepared teeth were molded with the addition of silicone, and the laboratory ceromer/fiber-reinforced crowns (SR Adoro/Fibrex Lab) were fabricated. Subsequently, the crowns were cemented and artificially aged in a mechanical fatigue device (1.2 X 106 cycles), then divided into 4 groups (n = 15) according to the surface treatment: 1) phosphoric acid etching (PA); 2) PA + silane application; 3) roughening with a diamond bur + PA; and 4) sandblasting with Al2O3 + PA. After the treatments, the crowns (n = 2) were qualitatively analyzed by scanning electron microscope (SEM) and surface roughness (n = 5) was analyzed before and after the surface treatment (Ra parameter). The remaining crowns (n = 8) received standard repair with an adhesive system (Tetric N-Bond) and a nanohybrid CR (Tetric N-Ceram), and the microshear bond strength (SBS) test was performed (0.5 mm/min). Roughness and SBS data were analyzed by one- and two-way ANOVA, respectively, as well as Tukey’s post-test (α = 0.05). Results: Sandblasting with Al2O3 + PA resulted in the highest final roughness and SBS values. The lowest results were observed in the PA group, whereas the silane and diamond bur groups showed intermediate values. Conclusion: It may be concluded that indirect ceromer crowns sandblasted with aluminum oxide prior to PA etching promote increased roughness surface and bond strength values.

Influence of Water Aging on Microtensile Bond Strength of a Flowable and a Packable Bulk-fill Resin Composites to Dentin

AIM: Investigation of the aging effect on the microtensile bond strength (μTBS) of bulk-fill resin composite (RC) versus a conventionally incrementally applied one.&#x0D; MATERIALS AND METHODS: A total number of 45 sound human impacted third molars extracted molars have been selected to prepare specimens for the μTBS test. Teeth were randomly divided into three groups (C) according to type of RC material which used for restoring the teeth. Where nanohybrid RC (Grandio®SO) was used as the control Group (C1), packable bulk-fill RC (X-tra fil®) was used for restoring teeth in C2 group and flowable bulk-fill RC (X-tra base®) was used for restoring teeth in C3 group. Each group was further subdivided into 3 subgroups (n = 5) according to the water storage time, where in subgroup 1; teeth were stored for 24 h, subgroup 2; teeth were stored for 3 months while for subgroup 3; and teeth were stored for 6 months. After water storage, teeth were sectioned for preparation of μTBS testing beams. Maximum tensile stresses were recorded in megapascal (MPa).&#x0D; RESULTS: After 24 h of water storage, the X-tra base® showed a higher statistically significant μTBS to dentin (33.82 ± 9.84 MPa) than did the other two types of RCs. After 3 months, the X-tra fil® showed the lowest mean value of μTBS (10.90 ± 5.66 MPa), meanwhile, after 6 months of water storage Grandio®SO showed the highest mean value of μTBS (15.85 ± 6.76 MPa). Regardless of the time the X-tra fil® showed the lowest mean of μTBS (15.07 ± 11.73 MPa), while there is no significant difference between the X-tra base® and Grandio®SO. Furthermore, the water aging adversely affects μTBS values which deceased gradually by time.&#x0D; CONCLUSION: The packable bulk-fill RC characterized by lower μTBS to dentin in comparison to the flowable bulk fill and the incrementally applied nanohybrid RCs. Furthermore, the μTBS of the three tested materials decreased gradually by aging.

Effect of using Different Remineralizing Agents on Micro-shear Bond Strength of Nanohybrid Composite Resin

AIM: This study was conducted to evaluate the effect of different remineralizing agents on micro-shear bond strength (SBS) of nanohybrid composite resin to dentin.&#x0D; METHODS: Thirty-six human molars were divided into four main equal groups (nine teeth each) according to the type of remineralizing agent used; nanohydroxyapatite, sodium fluoride, fluorohydroxyapatite, and control without remineralizing agent. Each group was divided into three equal subgroups (three teeth each) according to the storage time; 1 day, 1 month, and 3 months. Specially fabricated cylindrical plastic mold was made, and teeth were embedded vertically in the mold to the level of cementoenamel junction of the tooth leaving the occlusal surface projecting above the surface of the mold. Cylindrical fissure carbide bur was used in teeth preparation. Teeth were trimmed perpendicular to the long axes of them. Demineralizing agents (Nano hydroxyapatite, sodium fluoride, and fluorohydroxyapatite) were applied then adhesive system applied then composite resin was applied using five sections of a pediatric intravenous tube to act as molds for composite specimen then the specimens stored in artificial saliva at 37°C for different storage times in an incubator. The micro-SBS was assessed using universal testing machine. Then, the mode of failure for each group was determined using stereomicroscope device. Then, the obtained data were tabulated and statistically analyzed. One-way ANOVA was used to compare between more than two non-related samples. The significance level was set at p ≤ 0.05. Statistical analysis was performed with IBM SPSS Statistics.&#x0D; RESULTS: There was statistically significant difference between the four studied groups regarding bond strength at different storage times. Fluorohydroxyapatite had the highest bond strength mean values followed by nanohydroxyapatite, while the lowest value was the sodium fluoride group.&#x0D; CONCLUSION: Fluorohydroxyapatite and nanohydroxyapatite had a positive effect on micro-SBS to dentin, but sodium fluoride had a negative effect. The storage time increase had a positive effect on the micro-SBS of dentin with fluorohydroxyapatite and nanohydroxyapatite, also it had adverse effect on the dentin bond strength with sodium fluoride and control groups.

Effect of Dentin Desensitizing Agents on Shear Bond Strength of Two Total-Etch Adhesive Systems

Aim: it is to evaluate the effect of dentine desensitizing agents on shear bond strength of two totals-etch adhesive systems. Subjects and methods: Sixty human premolars free from caries or cracks were used in the study and randomly divided into six groups, group1; Adper Single bond 2, group 2; Prime & Bond NT, Group3; Adper Single Bond and Gluma desensitizing agent, group4,Adper Single Bond2 and Vivasens desensitizer, group5;Prime& Bond NT and Gluma desensitizer, group 6; Prime& Bond and Vivasens, then Z250 XT nanohybrid composite resin was packed in the mould and cured, then shear bond strength was measured by INSRTON universal testing machine, One-way ANOVA and Turhey’s tests were used for statistical analysis (P value ≤ 0.05). Results: group 3 Adper single bond2 and Gluma registered the highest mean shear bond strength value (12.806 ± 0.89), followed by group 1: Adper Single bond2 registered (12.046 ± 0.84), group 2; Prime & Bond NT recorded (11.21 ±0.47), group 4, Adper Single bond2 and Gluma registered (11.1435 ± 0.54), group 5, Prime & Bond and Gluma registered (11.818 ± 0.56), and group 6, Primr & Bond and Vivasens recorded (11.0485 ± 0.54). Conclusion: Gluma improved shear bond strength with both tested total-etch adhesive systems

The different effects of preheating and heat treatment on the surface microhardness of nanohybrid resin composite

Background: A composite resin is used as restorative material in dentistry because it has the same colour as dental enamel, is easy to use in an oral cavity and offers good biocompatibility. Based on the size of filler, composite resin is divided into types, one of which is a composite resin nanohybrid. An important mechanical property of restorative material is microhardness. The mechanical properties of restorative material is highly affected by both polymerisation and heating process. There are many methods to improve composite resin’s microhardness, including preheating and heat treatment. Purpose: The purpose of this study was to evaluate different effects of preheating and heat treatment on the microhardness of nanohybrid composite resin. Methods: This study is an experimental laboratory research with post-test-only group design. Samples were divided into six groups: preheating groups at temperatures of 37oC and 60oC, heat treatment groups at temperatures of 120oC and 170oC, a negative control group and a positive control group. Afterwards, the resulting data were analysed using one-way ANOVA. Results: The result based on the one-way ANOVA test indicated that there was a difference in microhardness in each group with a significance of 0.000 (p&lt;0.005) between preheating and heat treatment. Conclusion: The conclusion of this study was the best microhardness of composite resin nanohybrid is the heat treatment group at temperature 170oC.

Mechanical performance of monolithic materials cemented to a dentin-like substrate

Statement of problemStudies on the mechanical behavior of restorative materials bonded to tooth structure and considering the properties of the material and the bonding between both substrates are lacking. PurposeThe purpose of this in vitro study was to evaluate the hardness, fracture toughness, load-to-failure, cyclic fatigue, and stress distribution of 4 computer-aided design and computer-aided manufacturing (CAD-CAM) materials when bonded to a substrate similar to dentin (G10). Material and methodsDisks (11×1.2 mm) of lithium disilicate (LD), feldspathic ceramic (FC), polymer-infiltrated ceramic (PC), and a nanohybrid composite resin (NC) were fabricated (n=45) and had their surfaces polished. Microhardness was measured by the Knoop indentation (19.61 N, 12 seconds, n=5). Indented specimens were subjected to biaxial flexural strength testing, and the fracture origin defect was measured to calculate fracture toughness (n=5). Forty disks from each material were adhesively bonded to G10. Half of the specimens were subjected to load-to-failure testing, and remaining specimens (n=20) were subjected to cyclic fatigue (400 N, 106 cycles). The test was suspended every 200 000 cycles, and specimens were examined for cracks, debonding, or catastrophic failure. Obtained data were evaluated by analysis of variance and the Tukey post hoc test (α=.05). Weibull analysis was also performed. A 3D model of the tested specimens was constructed in a design software program, and the stress distribution was evaluated by finite element analysis, with the application of a 100-N load normal to the restoration surface. ResultsHardness values with statistically significant differences were LD (540.4)>FC (474.6)>PC (176.6)>NC (58.26). Fracture toughness vales (MPa.m1/2) and statistical significance were as follows: LD (2.25)=NC (2.46)>FC (1.14)=PC (1.18). Load-to-failure values (N) were LD (2881.6)=FC (2881.6)=PC (3200.6)>NC (2367.5). A specimen each of LD and NC fractured during the fatigue test, and LD and PC had a high percentage of subsurface cracks (55% and 75%, respectively). The FC had the lowest debonding rate after load-to-failure testing and no catastrophic fractures or cracks during fatigue. ConclusionsThe materials tested had different mechanical behaviors depending on the tests performed. Feldspathic ceramic had the best fatigue behavior when cemented to a dentin-like substrate.