Conventional Composite Resin Research Articles

Investigation of Water Absorption and Color Change of Indirect Composite Resins

Purpose:Since conventional composite resins have some disadvantages such as polymerization shrinkage and secondarycaries formation, indirect restorations are preferred in cases where tooth tissue loss is high. The aim of this study is toexamine the water absorption and color change of indirect composite resins in different beverages.Materials & Methods:In the study, 40 specimens (10×2 mm) were arranged from each composite using three indirect(Signum Composite, Signum Ceramis and Gradia Plus) and one conventional (GrandioSO) composite resin. After thespecimens were polished, they were used for water absorption and color change test. The water absorption test wasperformed through keeping them in water for 7 days as specified in ISO 4049:2009. Samples were kept in coffee, tea anddistilled water for 7 days in order to examine color differences. The water absorption and color change values of thecomposite resins at the end of the 7th day were appraised using one-way analysis of variance (ANOVA) and Tukey’s test(p<0.05).Results:While there was no statistically considerable difference between the water absorption data of the indirect andtraditional composite resin materials we used in the study (p>0.05). When the color changes of resin-containingcomposites in water, coffee and tea were examined, traditional composite resin (GrandioSO) showed statistically lesscolor change than indirect composites in water, coffee and tea (p<0.05).Conclusion:Although indirect composite resins showed similar water absorption with conventional composite, theyshowed more color change than conventional composite. The highest color change in indirect composites was seen incoffee solution. Particle size of the indirect composites do not affect water absorption, but the decrease in particle size ofcomposites shows less color change.

Monowave and polywave light-curing of bulk-fill resin composites: degree of conversion and marginal adaptation following thermomechanical aging

Aim: This study aimed to evaluate the effect of polymerization with either a monowave (MW) or a polywave (PW) light-curing unit (LCU) on the degree of conversion (DC) and marginal adaptation following thermomechanical aging of an ormocer bulk-fill resin composite (RC) (Admira fusion X-tra Bulk Fill – AB), a methacrylate-based bulk-fill RC (Tetric N-Ceram Bulk Fill – TB) and a conventional RC (Tetric N-Ceram – TC). Methods: DC was assessed in five samples of each RC using Fourier transform infrared spectroscopy. For determination of marginal adaptation, standard preparations were made in 60 bovine incisors, divided into three groups, according to the RC. The bulk-fill RC was inserted in a single increment of 4 mm. In contrast, the conventional RC was inserted in three increments. Marginal gap was evaluated after thermomechanical aging. Data were analyzed using a two-way analysis of variance (ANOVA) and Tukey’s tests for multiple comparisons (α = 0.05). Results: The two-way ANOVA showed a significant effect (p<.05) of the RC factor but not of the LCU factor. The Tukey test showed that TB had the significantly lowest DC followed by TC, and with AB having the significantly highest DC. For the marginal adaptation, a significant effect was found for the LCU factor and the for the interaction RC × LCU (p<.05). Groups light-cured with PW showed significantly wider marginal gaps than MW. TC presented wider marginal gaps (17.36 µm) when cured with PW than when cured with MW (13.05 µm). The two bulk-fill RC resulted in similar marginal gap formation to each other. Conclusion: The ormocer-based bulk-fill RC showed a higher DC than the methacrylate-based bulk-fill RC but similar marginal adaptation. The LCU, MW or PW, had no significant influence on the DC, and no relevance on the marginal adaptation.

Immediate and long-term microshear bond strength of resin-based cements to core build-up materials.

BackgroundTo evaluate the microshear bond strength (μ-SBS) between resin-based cements and core build-up materials after water storage. Material and MethodsCylinders (1x1 mm) of conventional dual-cure resin cement (RelyX ARC, 3M ESPE), universal dual-cure resin cement (RelyX Ultimate, 3M ESPE) or self-adhesive resin cement (RelyX U200, 3M ESPE) were adhered to disks (6x2 mm) made with commercial core build-up materials (Bis-Core, Bisco or LuxaCore Z, DMG) or conventional nanocomposite resin (Filtek Z350 XT, 3M ESPE). The specimens (n=10) were submitted to μ-SBS test using a universal testing machine and fracture pattern analysis at 48 hours or after 9 months of water storage. The data were evaluated by three-way ANOVA for repeated measures and Tukey’s test (α=0.05). ResultsAfter 48 hours, regardless of the resin-based cement used, the μ-SBS to the conventional resin composite (Filtek Z350 XT) was greater compared to other materials. However, after 9 months, there was a statistically significant decrease in μ-SBS values between the conventional resin composite and evaluated luting agents. The μ-SBS values of core build-up commercial materials (Bis-Core and LuxaCore Z) did not change over time. Regardless of the composite used and storage time, there was no statistically significant difference between the resin-based cements. After 48 h, the most prevalent failure was mixed for all groups. However, after 9 months, the core build-up materials showed a predominantly mixed fracture pattern whereas the resin composite presented an adhesive pattern. ConclusionsCommercial core build-up materials achieved stable bonding performance with resin-based cements over time. Key words:Composite resins, resin cement, dental restoration failure.

Physicochemical characterization of two bulk fill composites at different depths.

ObjectivesThis study analyzed the physical-chemical behavior of 2 bulk fill resin composites (BFCs; Filtek Bulk Fill [FBF], and Tetric-N-Ceram Bulk Fill [TBF]) used in 2- and 4-mm increments and compared them with a conventional resin composite (Filtek Z250).Materials and MethodsFlexural strength and elastic modulus were evaluated by using a 3-point bending test. Knoop hardness was measured at depth areas 0–1, 1–2, 2–3, and 3–4 mm. The translucency parameter was measured using an optical spectrophotometer. Real-time polymerization kinetics was analyzed using Fourier transform infrared spectroscopy.ResultsFlexural strength was similar among the materials, while TBF showed lower elastic modulus (Z250: 6.6 ± 1.3, FBF: 6.4 ± 0.9, TBF: 4.3 ± 1.3). The hardness of Z250 was similar only between 0–1 mm and 1–2 mm. Both BFCs had similar hardness until 2–3 mm, and showed significant decreases at 3–4 mm (FBF: 33.45 ± 1.95 at 0–1 mm to 23.19 ± 4.32 at 3–4 mm, TBF: 23.17 ± 2.51 at 0–1 mm to 15.11 ± 1.94 at 3–4 mm). The BFCs showed higher translucency than Z250. The polymerization kinetics of all the materials were similar at 2-mm increments. At 4-mm, only TBF had a similar degree of conversion compared with 2 mm.ConclusionsThe BFCs tested had similar performance compared to the conventional composite when used in up to 2-mm increments. When the increment was thicker, the BFCs were properly polymerized only up to 3 mm.

Evaluation of bond strength of self-adhesive resin composite repairs

ABSTRACT Objective: To evaluate the bond strength of repairs with the self-adhering flowable composite Vertise Flow (Kerr) and a conventional composite resin Filtek Z350 (3M ESPE) subjected to different surface treatments. Methods: Forty specimens were divided into four groups: ZV (Filtek Z350 + Vertise Flow, without prior treatment); ZAV (Z350 + Vertise Flow with prior treatment with Single Bond Universal Adhesive System (3M ESPE)); ZAZ (Filtek Z350 + Filtek Z350 with prior treatment with Single Bond Universal Adhesive System (3M ESPE)); VV (Vertise Flow + Vertise Flow, without prior treatment). After 15 days of storage, the specimens were subjected to microtensile tests (Kratos IKCL3-USB, SP, Brazil), with speed of 0.5 mm/min and 20kg load. For statistical analysis, ANOVA with Tukey tests were used (p &lt; 5%). Results: The mean values of the bond strength were highest respectively in the groups: ZV (36.07 ± 37.63); ZAZ (24.04 ± 28.51); VV (19.39 ± 28.24) and ZAV (16.06 ± 15.66). The bond strength of the repairs between the groups presented satisfactory results. Conclusion: The self-adhesive composite resin Vertise Flow seems to be a viable and fast alternative for composite resins repairs.

Evaluating the Failure of Resin-based Materials on the Proximal Cervical Dentin

Background: Resin-based materials are the popular restorative material in dentistry. The majority of these materials are light cured with a major disadvantage: marginal leakage. Objective: To evaluate the gap width of different resin-based materials at the cervical dentin when achieved mechanical force. Methods: Class II cavities were prepared on extracted premolar teeth with the gingival margin 1 mm below the Cementoenamel Junction (CEJ). In the first three experimental groups, three different lining materials (flowable resin composite, bulk-fill flowable resin composite, and resin-modified glass ionomer cement) were placed at the cervical dentin with a thickness of 1 mm. The rest of the cavities were restored with conventional resin composite. The other two groups were restored with conventional resin composite (control) or high viscosity bulk-fill resin composite, respectively. All groups were thermocycled and underwent vacuum pressure 2.6 KPa for 30 min in a Scanning Electron Microscope (SEM). Results: There was no gap formation at the cervical dentin on the external surface when restored with high-viscosity bulk fill resin composite. Almost all gaps occurred at the interface between restorative materials and the hybrid layer. The flowable bulk fill resin composite showed a significantly smaller gap width on both the external and internal surfaces compared to the other groups (p&lt; 0.05). The resin-modified glass ionomer cement showed the largest gaps in the cervical dentin (p &lt; 0.05). Conclusion: The different types of resin-based materials demonstrated a different failure of gap width under mechanical force. It clearly occurred at the restorative material-hybrid layer interface.

Color Stability of Bulk Fill Composite Resins Submitted to Coffee Staining

Objective: The aim of this in vitro study was to evaluate the color stability of different bulk fill composite resins after extrinsic staining with coffee. Material and methods: Forty-eight disk-shaped specimens (6 mm diameter x 2 mm thick) of each composite resin were prepared for color change test. The composite resins were divided into 4 groups (n=12): one conventional composite resin (Filtek Z250) and three bulk-fill composite resins (Filtek Bulk Fill, Aura Bulk Fill, and Opus Bulk Fill). The samples were stained with 20 mL coffee solution for 7 days, with the solution being replaced every 24 h. The color change analysis was performed using a spectrophotometer, according to the CIE Lab formula. Data were analyzed using the Analysis of variance (ANOVA) and Tukey HSD tests (?=0.05). Results: The results revealed significant differences in color change among the composite resins tested (?&lt;0.0001). The Aura Bulk Fill and Opus Bulk Fill showed the highest color change values. Conclusions: Thus, all the resins analyzed were susceptible to extrinsic staining with coffee, and the Filtek Bulk Fill showed the lowest color change value.

Bond Strength Evaluation of Bulk- fill Composites to Dentin Under Different Surface Treatments

Purpose: The aim of this study is to compare the shear bond strength of three high-viscosity bulk-fill composite resins applied as single layers of 4mm thickness and of one microhybrid composite resin applied incrementally with a thickness of 2mm on dentin surfaces prepared with different surface preparation methods. Materials and Methods: A total of 132 caries-free human molars whose dentines had been exposed were used. Three groups, each containing 44 teeth, were formed. The acid group was etched with 32% phosphoric acid; laser group was etched with Er, Cr; YSGG laser and the control group was prepared with silicon carbid paper. Following the application of bonding agent, composite resin materials were applied on teeth using teflon moulds of 4x4mm. The samples were then subjected to shear bond strength tests. Two-way variance analysis and Tukey HSD multiple comparison test were applied on collected data. Results: There was a significant difference between surface treatment methods used regarding shear bond strength (P&lt;0.001). The highest shear bond strength values were detected in the “Acid” group while the lowest shear bond strength values were detected in the “control” group. On the other hand, there was no statistically significant difference among composite resins (P&gt;0.05). Conclusions: Laser etching of the dentin tissues is not as effective as acid etching. Bulk-fill composites had similar effects compared with conventional composite resins with regard to bonding strength. More in vitro studies supported with clinical data are required to investigate the performance of bulk-fill composites and laser.

Effect of Fiber-Reinforced Composite and Elastic Post on the Fracture Resistance of Premolars with Root Canal Treatment—An In Vitro Pilot Study

(1) Background: To analyze the fracture resistance of endodontically upper premolar teeth restored with glass fiber reinforced posts, glass fiber elastic posts, conventional composite resin (CR) and glass fiber reinforced composite (FRC) resins as restorations. (2) Methods: Seventy premolars were submitted to root canal treatment and restored with the following restorative materials (n = 10): A. FRC posts restored with resin; B. Elastic FRC posts restored with resin; C. FRC posts restored with FRC resin; D. Elastic FRC posts restored with FRC resin; E. Direct restoration with resin; F. Direct restoration with FRC resin; G. Untreated teeth. The teeth were embedded in an epoxy resin model, thermal cycling fatigued in distilled water and mechanical cycling fatigued inducing 80 N load. Loading was applied axially on the center of the occlusal surface with a vertical displacement. The fracture was produced by a universal machine at a crosshead speed of 0.5 mm/s with a 5000 N load cell. The results were analyzed by ANOVA and Tukey’s test and Weibull characteristic strength and modulus were calculated. (3) Results: The group that obtained the greatest fracture resistance was D (3620 ± 470 N) and the least resistant was group A (2420 ± 1010 N). Statistically significant differences were observed between the groups restored with Elastic FRC posts-CR versus FRC post-CR and only CR (p = 0.043 and p = 0.008). (4) Conclusions: The glass fiber reinforced restorative materials increase the fracture resistance of endodontically treated teeth.

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.

Comparative Effectiveness of Two Light Curing Units on the Properties of Dental Resin Composites

Background: Setting of conventional glass ionomers cement and dental resin composites as filling materials is predominantly through polymerization reaction, which is usually induced by light. The objective of this study was to assess the temperature changes, light intensities, sorption and solubility capability and comparative micro hardness in Dental Resin Composites (DRC) by using two different light curing units that is Quartz Tungsten Halogen (QTH) and Light Emitting Diodes (LED). Methods: This analytical, experimental, in-vitro study was spanned over one month, conducted in the laboratory of Dental Materials, Dr. Ishrat-ul-Ibad Khan Institute of Oral Health Sciences. Through non-probability, convenient sampling, 60 samples of DRCs was prepared as 10mm in diameter and 2mm in thickness in the steel moulds by a single trained operator. Effect of heat generation, light intensities, sorption and solubility and micro hardness during polymerization of DRCs were all measured. Statistical analysis was done using SPSS with descriptive statistics and two sample independent t-tests. The p-value of &lt;0.05 was considered significant at 95 % confidence level. Results: Mean surface micro hardness of DRC was found to be 15.48±0.46 and 18.26±0.53 when QTH and LED lamps were employed respectively. Whereas, mean light intensity of QTH and LED lamps were found to be 434 and 925mW/cm2. No significant difference in temperature change during polymerization reaction (p=0.128) and in sorption and solubility capability (p=0.001) of DRC was observed. Conclusion: Light-emitting diodes were evaluated to be more effective than Quartz Tungsten Halogen Light in achieving increased surface micro hardness of DRC. Keywords: Light; Glass Ionomer Cements; Tungsten; Hardness.

Flexural strength of CAD-CAM and conventional interim resin materials with a surface sealant

Statement of problemThe flexural strength of computer-aided design and computer-aided manufacturing (CAD-CAM) and conventional interim resin materials when they are used with a surface sealant is unclear. PurposeThe purpose of this in vitro study was to evaluate the flexural strength of different CAD-CAM polymethyl methacrylate (PMMA)-based polymers and conventional interim resin materials, autopolymerized bisacrylate composite resin and polyethyl methacrylate (PEMA) with and without a surface sealant after thermocycling. Material and methodsFourteen rectangular-shaped specimens (25×2×2 mm) were fabricated from 5 different interim resin materials, 3 different CAD-CAM PMMA-based polymers: Polident-PMMA, Telio CAD, M-PM-Disc; 2 different conventional interim resin materials, and 1 autopolymerized bisacrylate composite resin: Acyrtemp and 1 PEMA resin: Bosworth Trim according to ISO 10477:2018. Two different types of surface treatments (n=7), conventional polishing and surface sealant application, were applied to 1 surface of the specimens. Ten thousand thermocycles were applied in distilled water for all specimens (5 °C and 55 °C). A 3-point bend test was used to measure the flexural strength of specimens in a universal testing device at a 1 mm/min crosshead speed. The flexural strength data (σ) were calculated in megapascals (MPa) and analyzed by using a 2-way ANOVA. Post hoc pairwise comparisons and independent t test analysis were done (α=.05). ResultsAccording to the 2-way ANOVA, material type (P<.001) significantly affected the flexural strength. Surface treatment type (P=.818) had no significant effect on flexural strength, and no significant interaction was found between material type and surface treatment type (P=.111). CAD-CAM PMMA-based polymers had significantly higher flexural strength than the conventional interim resin materials. However, no significant difference was found within groups of the same type. Also, no significant difference was found in flexural strength values between the conventional polishing and surface sealant groups within each interim resin material (P≥.162). ConclusionsThe flexural strength of CAD-CAM PMMA-based polymers was higher than the flexural strength of conventional bisacrylate composite resin and PEMA interim resin materials after thermocycling. The surface treatment type (conventional polishing and surface sealant application) was not found to affect the flexural strength of CAD-CAM PMMA-based polymers, conventional bisacrylate composite resin, or PEMA interim resin materials.

The Use of Bulk-Fill Flow in the Customization of Glass Fiber Post.

Objectives The aim of this study is to evaluate the influence of different composite resin in the customization of glass fiber posts (GFPs) on bond strength and failure mode. Materials and Methods Thirty bovine roots were selected. The wall roots were reduced so that each wall had a minimum dentin thickness of 1 mm. Thirty GFPs were divided into three groups ( n = 10), which received different types of customization. The first had the GFP relined by bulk-fill flowable composite resin (BF), the second group had the GFP customized by conventional regular composite resin (CR), and the third group was cemented with dual resin cements (DRC), without relining. The root were sectioned, resulting in two 1.0-mm thick slices from cervical root regions only and push-out bond strength test was performed (EMIC, Universal testing machine). To determine failure mode, a stereomicroscope was used at ×40 magnification, with a 2.5D analysis. Statistical Analysis Data were analyzed using two-way ANOVA ( α = 0.05) and Tukey’s test. Results BF (9.08 ± 1.9) and CR (9.17 ± 3.00) did not show a statistically significant difference ( p = 0.961), regarding the bond strength test values. However, there was a statistically significant difference between DRC (5.44 ± 1.89) and the others ( p < 0.05). BF (66.66%) and the CR group (47.61%) presented a predominantly failure mode type 6: mixed between resin cement and composite. While the highest failure index of the DRC group was type 2: adhesive between resin cement and dentin (47.61%). Conclusion BF can be an alternative for the customization of fiber posts, since it presented a similar behavior to the established technique with conventional composites.

Interfacial Stress and Bond Strength of Bulk-Fill or Conventional Composite Resins to Dentin in Class II Restorations

The aim was to evaluate the microtensile bond strength (mTBS) to dentin and interfacial stress in a class II cavity restored with bulk-fill or conventional composite resins and the margin interfaces. Vertical slot class II cavities in the mesial face, with the gingival end in dentin, were prepared in 72 third molars, being divided into groups (n=24): G1-Tetric N-Ceram; G2-Tetric N-Ceram Bulk-Fill; G3-SonicFill. Clearfil SE Bond adhesive system was used in all groups. Half of the teeth in each group (n=12) were submitted to thermo-mechanical cycling (TMC). Restored teeth (n=9) were cut perpendicular to obtain beams, which were submitted to a mTBS test in an EMIC machine. The cervical margins in dentin of the restored teeth (n=3) were assessed using SEM through epoxy resin replicas as well as the section of the restoration. Interfacial stresses after load application were calculated by 2D finite element analysis. The mTBS means-MPa followed by different letters represent statistical difference by ANOVA and Games-Howell's test (p<0.05): Without TMC: G1-15.68±6.10a; G2-10.08±5.21ab; G3-7.98±3.76b. With TMC: G1-9.70±5.52a; G2-5.79±1.42a; G3-4.37±1.87a. Interfacial stress (MPa) was 4.4 for SonicFill, 3.9 for Tetric N-Ceram, and 3.5 for Tetric N-Ceram Bulk-Fill. SEM images showed continuous margins for all composite resin restorations. It was possible to conclude that SonicFill obtained a slightly higher interfacial stress and lower bond strength to dentin in comparison with Tetric N-Ceram and Tetric N-Ceram Bulk-Fill. Continuous margin interfaces were obtained for Tetric N-Ceram, Tetric N-Ceram Bulk-Fill, and SonicFill. However, voids were observed in the SonicFill restorations.

Effect of bleaching protocols on surface roughness and color change of high- and low-viscosity bulk-fill composite resins.

The aim of this in vitro study was to evaluate the effect of bleaching protocols on the surface roughness (Ra), color change and surface micromorphology of a low-viscosity bulk-fill composite (Filtek Bulk Fill Flow, 3M ESPE), a highviscosity bulk-fill composite (Filtek Bulk Fill, 3M ESPE) and a conventional nanoparticulate composite resin (control) (Filtek Z350 XT, 3M ESPE). Forty samples of each composite (disks 5 mm in diameter and 2 mm thick) were randomly divided into four groups (n=10), according to bleaching protocol: a) 10% carbamide peroxide gel (Opalescence, Ultradent Products) (2 h/ day, for 14 days); b) 40% hydrogen peroxide gel (Opalescence Boost, Ultradent Products) (three bleaching sessions, once a week, 45 min/session); c) whitening rinse (Listerine Whitening Extreme, Johnson &amp; Johnson) (2 min/day, for 14 days); and d) distilled water (control). The samples were submitted to triplicate readings (Ra and color [CIELAB parameters]) before and after contact with bleaching protocols. Micromorphology was analyzed in a scanning electron microscope (SEM). Ra and color parameters (ΔL, Δa, Δb and ΔE) were analyzed by generalized linear models (α=0.05). The Ra of the high-viscosity bulk-fill was significantly higher than that of the other composites (p&lt;0.05). Ra increased significantly (p&lt;0.05) and surface became more irregular (SEM analysis) in all the composite resins, regardless of the bleaching protocol (p&lt;0.05). The high-viscosity bulk-fill composite resin group had significantly lower ΔE (p&lt;0.05) than the nanoparticulate composite resin group immersed in distilled water. It was concluded that the characteristics of each resin significantly influenced the Ra more than the bleaching protocol. The high-viscosity bulk-fill resin presented minor color change.

Comparative analysis of the surface roughness of conventional resins and filling after immersion in mouthwashes

Aim: Bulk Fill composite resins were released on the market in order to reduce the time in clinical sessions by using increments of up to 5.0 mm thickness. The aim of this study was to evaluate the effect of the rinsing solutions on the surface roughness of the conventional composite and Bulk fill composite resins. Methods: 40 specimens were prepared from a 4.0mm x 10.0mm teflon matrix and photoactivated for 20 seconds, with 20 specimens made of Filtek Bulk-Fill composite resin (3M ESPE) and 20 specimens made with Filtek™ Z350 XT composite resin (3M ESPE). Each group was subdivided into 2 subgroups: G1 (Filtek™ Z350 XT-3M ESPE-immersed in Colgate PlaxWhitening®); G2 (Filtek™ Z350 XT-3M ESPE-immersed in PlaxFreshMint®); G3 (Filtek™ Bulk-Fill-3M ESPE-immersed in Colgate PlaxWhitening®) and G4 (Filtek™ Bulk-Fill-3M ESPE-immersed in Colgate PlaxFreshMint®). The surface roughness test was performed initially and after immersion in rinses by the Time Group Inc.-TR200® rugosimeter apparatus and the data were submitted to statistical analysis (two-way repeated measures ANOVA). Results: Surface roughness values of the Filtek™ Bulk-Fill composite resin (3M ESPE) were significantly higher than the Filtek™ Z350 XT composite resin (3M ESPE) (P &lt;0.0001). However, no differences were identified before and after immersion in rinses with or without alcohol. Conclusion: The use of mouthwashes does not interfere with the surface roughness of the tested resins, but the composite resin Filtek Z350 XT (3M ESPE) presents a surface with less roughness.

Fracture Resistance of Three Post Types in the Restoration of Anterior Primary Teeth

Background: Extensive restorative treatments of anterior primary teeth are challenging in pediatric dentistry. Objective: This study aimed to compare the fracture resistance of three post types for restoring the anterior primary teeth. Methods: This in-vitro study was carried out on 90 extracted maxillary anterior primary teeth with intact roots. They were randomly allocated into six groups to be restored with conventional composite resin post, X-tra fill composite resin post, Tetric N Ceram composite resin post, prefabricated glass fiber post with conventional composite build-up, prefabricated glass fiber post with X-tra fill composite build-up, and prefabricated glass fiber post with Tetric N Ceram composite build up. The samples were polished and placed in acrylic resin blocks with 1 mm of part of cervical root being out, thermocycled (×5000) and tested for fracture resistance. Intra-class correlation test, Kruskal-Wallis test and one-way ANOVA were used for statistical analyses (α=0.05). Results: The mean fracture resistance was significantly different among the six groups. It was the highest in prefabricated glass fiber post with conventional composite build-up (418.64 N), prefabricated glass fiber post with X-tra fill composite build-up (403.63 N) and prefabricated glass fiber post with Tetric N Ceram composite build up (361.63 N); and the lowest in Tetric N Ceram group (280.65 N). The groups were significantly different concerning the fracture strength and fracture state. Conclusion: Since the anterior teeth restored with prefabricated glass fiber posts were far more fracture resistant, and prefabricated glass fiber posts can be promisingly used for the restoration of anterior primary teeth.

Polymerization shrinkage, shrinkage stress, and mechanical evaluation of novel prototype dental composite resin.

A new photocurable composite resin for dental restorations was synthesized using a monovinyl acrylate diluent. Its polymerization shrinkage, shrinkage stress, degree of conversion, and mechanical properties were investigated and compared to those of a conventional composite resin synthesized using a triethyleneglycol dimethacrylate diluent as well as three commercial resins: Tetric N-Ceram, Neofil, and Gradia Direct. The polymerization shrinkage and shrinkage stress of the new composite resin were statistically lower than those of the conventional resin (p<0.05), but not those of the commercial resins (p>0.05). The degree of conversion of the new resin was statistically better than all other tested resins (p<0.05) except the Neofil resin (p>0.05). The mechanical properties of the resins were not statistically different (p>0.05). Overall, the new composite resin exhibited less polymerization shrinkage, lower shrinkage stress, a higher degree of conversion, and similar mechanical properties to the other resins, demonstrating its potential for clinical application.

The effect of rapid high-intensity light-curing on micromechanical properties of bulk-fill and conventional resin composites

Rapid high-intensity light-curing of dental resin composites is attractive from a clinical standpoint due to the prospect of time-savings. This study compared the effect of high-intensity (3 s with 3,440 mW/cm2) and conventional (10 s with 1,340 mW/cm2) light-curing on micromechanical properties of conventional and bulk-fill resin composites, including two composites specifically designed for high-intensity curing. Composite specimens were prepared in clinically realistic layer thicknesses. Microhardness (MH) was measured on the top and bottom surfaces of composite specimens 24 h after light-curing (initial MH), and after subsequent immersion for 24 h in absolute ethanol (ethanol MH). Bottom/top ratio for initial MH was calculated as a measure of depth-dependent curing effectiveness, whereas ethanol/initial MH ratio was calculated as a measure of crosslinking density. High-intensity light-curing showed a complex material-dependent effect on micromechanical properties. Most of the sculptable composites showed no effect of the curing protocol on initial MH, whereas flowable composites showed 11–48% lower initial MH for high-intensity curing. Ethanol/initial MH ratios were improved by high-intensity curing in flowable composites (up to 30%) but diminished in sculptable composites (up to 15%). Due to its mixed effect on MH and crosslinking density in flowable composites, high-intensity curing should be used with caution in clinical work.

Response of two gingival cell lines to CAD/CAM composite blocks

ObjectiveThis study aimed to investigate the influence of CAD/CAM composite materials on human gingival fibroblasts (HGF) and gingival keratinocytes (HGK). MethodsFour materials were investigated: two resin-composite blocks (RCB), Grandio Blocs (GR) and Block HC (HC); one polymer-infiltrated ceramic network (PICN) (Enamic, EN); and one conventional resin-composite, Grandioso (GND). HGF and HGK were cultured as per the supplier’s protocol (ATCC, UK). Cell proliferation and cytotoxicity were evaluated at 1, 3, 5 and 10 days using LDH and Alamar Blue assays. Indirect immunostaining was used to assess the Caspase-3 activity. Data were analysed via two-way ANOVA, one-way ANOVA and Tukey’s post hoc test (α = 0.05 for all tests). ResultsThere was significant difference in cell proliferation of the HGK and HGF cells in contact with different composite materials but no significant differences in their cytotoxicity. There was a significant effect on cell proliferation and cytotoxicity with different exposure times, for each type of resin-composite. HGF cell proliferation was higher than HGK with almost all investigated materials and at all time points. No Caspase-3 activity was detected in either cell lines. SignificanceHGK proliferation and cytotoxicity appeared to be more influenced by composite materials compared to HGF, demonstrating EN cytotoxic effects in HGK. Different manufacturing techniques of resin-composites (photo curing versus heat/pressure curing) had no significant effect on their biocompatibility.