Conventional Resin-based Composites Research Articles

Effect of a 3-second Off-label Exposure on the Depth of Cure of Eight Resin-based Composites.

This study evaluated the depth of cure (DoC) of eight resin-based composites (RBCs) photocured using one multipeak light-curing unit (LCU) on the standard output setting for the manufacturer's RBC recommended exposure time and at a higher irradiance for 3 seconds. Three conventional RBCs: Tetric EvoCeram (Evo), Tetric N-Ceram (Cer), Tetric Prime (Pri); and five bulk-fill: Tetric N-Ceram Bulk Fill (CerBF), Opus Bulk Fill APS (OpusBF), Opus Bulk Fill Flow APS (OpusF), Tetric PowerFill (PFill) and Tetric PowerFlow (PFlow) were examined. Only PFill and PFlow are formulated to be photocured in 3 seconds. The RBCs were packed into a metal mold and photocured using a Bluephase PowerCure LCU for the RBC manufacturer's recommended exposure time on the standard mode and using the 3-second high irradiance mode. After photocuring, the specimens were immersed in a solvent for 1 hour. The length of the remaining RBC was measured and divided by 2. Data were analyzed using two-way analysis of variance (ANOVA) followed by the Tukey post hoc multiple comparison test (α=0.05). There was no significant difference in the DoC values for PFill and PFlow when photocured using the 3-second high irradiance protocol compared to the lower irradiance standard mode protocol. All other RBCs had significantly lower DoC values (p<0.001) when photocured off-label using the 3-second high irradiance mode. Of the eight RBCs tested, only PFill and PFlow achieved the same DoC when the high irradiance 3-second curing method was used compared to when their longer lower irradiance protocol was used.

Investigation on the Biaxial Flexural Strength of Universal Shade Resin-Based Composites.

The biaxial flexural strength of universal shade and conventional dental resin-based composites before and after alkaline degradation was investigated. Disk samples were prepared from these resin-based composites, and some of the specimens were immersed in 0.1 M NaOH solution to create deteriorated samples. The biaxial flexural strength of the samples before and after the alkaline degradation test was measured and statistically tested. The fracture surfaces after the biaxial flexural test were observed using a scanning electron microscope. The results showed that the biaxial flexural strength of the paste-type universal shade resin-based composite before alkaline degradation was significantly (19%) higher than that of the conventional type, but no difference was observed between the materials after alkaline degradation. On the other hand, the biaxial flexural strength of the flowable universal shade resin-based composites was significantly (around 35%) lower than that of the conventional composite, with or without degradation. Although, for paste-type materials, the biaxial flexural strength of universal shade resin-based composites was higher than that of conventional resin-based composites before alkaline degradation, after degradation the two materials showed similar values. For flowable materials, the biaxial flexural strength of universal shade resin-based composites was lower than that of conventional resin-based composites regardless of the presence or absence of degradation processes. These results suggest that some caution should be used when deciding whether to use flowable universal shade resin-based composite to fill a cavity.

Mechanical and Optical Characterization of Single-shade Resin Composites Used in Posterior Teeth.

This study aimed to evaluate the optical and mechanical performance of two single-shade resin-based composites (RBCs) compared to those of a conventional RBC for restoring posterior teeth. Two single-shade RBCs, Omnichroma (Tukoyama) and Vittra Unique APS (FGM), and a conventional RBC, Filtek Z350XT shade A2 (3M Oral Care), were evaluated in this study. The optical shade-matching performance was measured using a spectrophotometer. The light emitted by VALO Grand (Ultradent) and transmitted through the 2.0-mm RBC specimens was evaluated using beam profiling. Knoop hardness (KH, N/mm2), degree of conversion (DC, %) at the top and bottom, flexural strength (FS, MPa), elastic modulus (E, GPa), postgel shrinkage (Shr, %), and shrinkage stress (MPa) were evaluated. Scanning electron microscopy (SEM) was used to characterize the filler. Data for FS, E, and Shr were analyzed by one-way analysis of variance (ANOVA) and KH and DC by repeated one-way ANOVA measurement followed by Tukey test (α=0.05). The modified von Mises stress values, light transmission, and SEM images were analyzed qualitatively. All single-shade RBCs exhibited higher chromatic adaptation than the Filtek Z350XT (p<0.001). Omnichroma exhibited less color difference than Vittra Unique APS, irrespective of the shade. The light transmitted through Omnichroma and Vittra Unique APS increased during polymerization. KH and DC values were significantly reduced from the top to the bottom of the specimens for all RBCs (p<0.001); however, the ratio values were always higher than 80%. In general, all RBCs demonstrated similar mechanical properties. All RBCs exhibited a similar FS (p=0.083) and Shr value (p=0.144). Filtek Z350XT exhibited significantly higher E (p<0.001) than both single-shade RBCs. All RBCs exhibited similar shrinkage stress during restoration and similar residual stress during occlusal loading. Single-shade Omnichroma and Vittra Unique APS increased light transmission during light-activation, demonstrating better chromatic adaptation than conventional Filtek Z350XT. In general, Omnichroma and Vittra Unique APS exhibited similar mechanical properties and shrinkage stress distributions as Filtek Z350XT during light-activation and occlusal loading.

A Laboratory Study of the Effect of pH on Solubility of Bulk-Fill and Conventional Composites

Aim: Factors such as the low pH of acidic foods and beverages can affect long-term clinical success of restorative materials in the oral cavity. The aim of this study was to compare the solubility of Bulk-fill and Conventional Nano-Hybrid Resin Based Composites (RBCs) in different solutions. Material and Methods: A total of 60 cylindrical specimens were prepared from two RBCs (Tetric N-Ceram, Tetric N-Ceram Bulk-fill) and their constant weight was measured. The specimens were divided into six groups ( N = 10) in accordance with RBC type and pH solution (solution 1, 2, 3 with pH = 2.5, 5, 7, respectively), and were immersed in desired solutions for 30 days. Then they were weighed again and solubility levels of the specimens were calculated according to ISO 4049. Data were analysed by two-way ANOVA. The test power was considered at 80%. Results: The type of RBC had no significant effect on solubility; while the effect of PH was significant. Solution 1 caused significantly the highest solubility. No statistically significant differences were found among other groups. Conclusions: Considering the limitations of the laboratory investigations, it was concluded that solubility rate of Bulk-fill and Conventional RBCs was higher in solutions with lower pH. There was no difference among the RBCs. However, the solubility rates of all groups are within the clinically normal range.

Influence of high-irradiance light curing on the marginal integrity of composite restorations in primary teeth

BackgroundReducing the necessary time to restore primary teeth improves the cooperation of paediatric patients. This study aimed to investigate the marginal integrity of restorations prepared with a bulk-fill resin-based composite (RBC) containing additional fragmentation chain transfer (AFCT) compared to a conventional RBC when light cured with a rapid high-irradiance (3 s) and a regular (10 s) curing mode.MethodsForty class-II cavities were prepared in 40 primary molars. The molars were randomly divided into four groups based on the applied light-curing modes (regular: 10 s @ 1200 mW/cm2 or high-irradiance: 3 s @ 3000 mW/cm2) and the used restorative material (AFCT-containing bulk-fill RBC “Power Fill” or AFCT-free conventional RBC “Prime”). After thermo-mechanical loading, the marginal integrity was analysed using scanning electron microscopy. A beta regression model and pairwise comparisons were used to statistically analyse the data.ResultsThe mean marginal integrity (% ± SD) of the restorations for each group was as follows: Power Fill (10 s: 79.7 ± 15.6) (3 s: 77.6 ± 11.3), Prime (10 s: 69.7 ± 11.1) (3 s: 75.0 ± 9.7). The difference between the RBCs for the same light-curing mode was statistically significant (p ≤ 0.05). The difference between the light-curing modes for the same RBC was not statistically significant (p ˃ 0.5).ConclusionsAFCT-containing bulk-fill RBC “Power Fill” achieves similar marginal integrity when light-cured with either high-irradiance or regular light-curing modes. “Power Fill” achieves better marginal integrity than the conventional RBC “Prime” regardless of the applied light-curing mode.

Polymerization shrinkage of light-cured conventional and bulk-fill composites -The effect of cavity depth and post-curing.

Volumetric shrinkage (VS) of conventional, bulk-fill, and core build-up resin-based composites (RBCs) of various thickness (1-5 mm) was measured using the modified bonded-disk method with confocal laser scanning microscopy. Additionally, the bottom-to-top ratio of Vickers hardness (%VH) was measured. Conventional RBCs exhibited significantly higher VS than bulk-fill and core build-up RBCs (p<0.05). As specimen thickness increased, VS relative to volume (%VS) and difference in VS at each depth (VSdepth) decreased. For conventional RBCs, there was a significant drop in VSdepth between 1 mm and 2 mm (p<0.05), and another drop was observed between 3 mm and 4 mm (p<0.05) where %VH decreased below 90%. For bulk-fill and core build-up RBCs, VSdepth decreased significantly between 2 mm and 3 mm (p<0.05), but %VH exceeded 90% even in 5 mm deep cavities. These results indicated that post-curing contributed to lower shrinkage in deeper layers, and that conventional RBCs were not adequately polymerized at the depth of over 3 mm.

Surface properties and Streptococcus mutans biofilm adhesion of ion-releasing resin-based composite materials

ObjectiveTo evaluate the adhesion of Streptococcus mutans (S. mutans) and related surface properties of ion-releasing resin-based composite (RBC) restorative materials. MethodsTwo ion-releasing RBCs, Activa (ACT) and Cention-N (CN), were compared to a conventional RBC (Z350) and a resin-modified glass ionomer cement (Fuji-II-LC). Ten disk-shaped specimens were fabricated for each material (n = 40). After standardized surface polishing procedure, the surface properties of the specimens were evaluated using surface roughness measurements by a profilometer and hydrophobicity using water contact angle measurements. To assess bacterial adhesion, the number of S. mutans bacteria was calculated from colony-forming units (CFU). Confocal laser scanning microscope analysis was done for qualitative & quantitative assessment. The data were analyzed using One-way ANOVA followed by Tukey's post-hoc test to compare the mean values of surface roughness, water contact angle and CFU values. To compare the mean dead cell percentage Kruskal-Wallis rank test and Conover test were used. A p-value of ≤ 0.05 was used to report the statistical significance. ResultsZ350 and ACT had the smoothest surfaces, followed by CN, and the roughest surface was seen in FUJI-II-LC. The lowest water contact angles were seen in CN, and Z350, and the highest were in ACT. S. mutans counts were the highest in ACT and the lowest in Z350 and CN. CN and Fuji-II-LC registered the highest percentage of dead bacterial cells, while the lowest were in ACT. SignificanceSurface properties did not significantly influence bacterial adhesion. More S. mutans bacteria accumulated on ACT than on the nanofilled composite and on CN. CN had antibacterial effects against Streptococcus mutans biofilms.

Effect of Using Manufacturer-recommended Exposure Times to Photo-activate Bulk-fill and Conventional Resin-based Composites.

To analyze the effect of using the resin-based composite manufacturer's recommended exposure time on the degree of conversion (DC), Knoop hardness (KH), and elastic modulus (E) of conventional and bulk-fill resin-based composites (RBCs). Three resin-based composites (RBCs) were tested: Tetric EvoCeram Bulk Fill (TET), Opus Bulk Fill APS (OPU), and RBC Vittra APS (VIT). They were photo-activated in 2 mm deep, 6 mm diameter molds for their recommended exposure times of 10 seconds, 20 seconds, or 40 seconds from four light-curing units (LCUs). Two delivered a single emission peak in the blue light region (Optilight Max and Radii-Cal) and two delivered multiple emission peaks in the violet and blue region (VALO Cordless and Bluephase G2). After 24 hours of dry storage at 37°C in the dark, the KH (Kgf/mm2), E (MPa) and DC (%) at the top and bottom surfaces of specimens (n=5) were measured and the results analyzed by 2-way analysis of variance (ANOVA) followed by a Tukey test (α=0.05). The irradiance (mW/cm2) and spectral irradiance (mW/cm2/nm) from the LCUs were reduced significantly (8-35%) after passing through 2.0 mm of RBC (p<0.001). The DC at the bottom of VIT and TET was less than at the top surface (p<0.001). OPU had the same DC at the top and bottom surface (p=0.341). The KH and E values at the top surface of VIT and TET were substantially higher than at the bottom (p<0.001). OPU exposed for 40 seconds achieved higher mechanical properties than TET that was photo-activated for 10 seconds (p<0.001). The opacity of different bulk-fill RBCs changed differently during the polymerization; OPU became more opaque, whereas TET became more transparent. When exposed for their recommended times, the 2 mm thick RBCs that used Ivocerin or the APS photoinitiator system were adequately photo-activated using either the single or multiple emission peak LCUs (p=0.341). After 24 hours' storage, all the 2 mm thick RBCs photo-cured in 6 mm diameter molds achieved a bottom-to-top hardness ratio of at least 80% when their recommended exposure times were used. TET, when photo-activated for 10 seconds, achieved lower mechanical properties than OPU that had been photo-activated for 40 seconds. The change in opacity of the RBCs was different during photo-activation.

Colour Stability Of Bulk Fill Composites: A Systematic Review

Background: The introduction of Bulk-Fill (BF) composite materials, among other new preparations, was one of the most recent innovations in operative dentistry. All bulk composites' colour stability is a source of concern. There has been a lot of research on the effects of different drinking solutions on the colour consistency of conventional resin-based composites, but little has been written about the colour changes of BF composite resins, which have been developed for the placement of somewhat thicker layers.&#x0D; Aim: Thus, the objective of this systematic review was to assess the colour consistency of various bulk-filled composites.&#x0D; Methods and Materials: A massive exploration of preexisting literature was done in order to locate all relevant research that addressed the sustainability of colour of BF composites under the effect of various. According to PRISMA standards, the current systematic evaluation was carried out. A thorough search for non-controversial existing literature on the websites like PubMed portal, MEDLINE portal, and Scopus portal was done in December 2022. There were no comparable articles in Cochrane online library. To make sure that all pertinent studies were found, search keywords were applied. Furthermore, all appropriate scientific papers from Jan 2010 to December 2022 on the effect of various beverages, polishing techniques, storage media, and oral fluids, bleaching protocols on the colour longevity of bulk-filled composite samples were included.&#x0D; Results: 18 studies were evaluated in this systematic review. 9 studies focused on the effect of different drinks and beverages like tea, coffee, wine, and acidic beverages over the changes in the colour of bulk-filled composites. There were 4 studies that evaluated the impact of different polishing mechanisms. There were 2 researches that described the influence of different bleaching techniques over the change in colour of bulk-filled composites. One study discussed the effect of reinforcement of glass fibers and polythene fibers in bulk-filled composites, the presence of different dentin substitutes and water solubility and water sorption impact over the change in colour. The number of specimens evaluated ranged from n=20 to n=800 across all the included studies. There was the use of two to ten composite materials across all the included studies.&#x0D; Conclusion: When there was an analysis of the effect of different beverages and drinks over the changes in colour then there were mixed results. Some studies found that colour changes in bulk-filled composites are lesser than in customary composites. While some studies revealed that alteration in colour is greater in bulk-filled composites when compared to customary composites. Some studies found no significant difference in colour change in conventional composite and bulk-filled composite. The polishing operations can have a serious influence on the staining impedance of bulk-fill composite resins.

Physico-Mechanical Characteristics of Ormocer and Bulk Fill Composite Resin Restorative Materials: An in-vitro Study

Introduction: Bulk Fill (BF) resins and Ormocers are recently introduced composite restorative materials in order to overcome the disadvantage of polymerisation shrinkage exhibited by most of the conventional resin-based composites. Aim: To evaluate the physical and mechanical properties of Organically Modified Ceramics (Ormocers) in comparison with BF composite resin restorative material. Materials and Methods: In this in-vitro study, 20 human extracted premolars were allocated into two groups of 10 each. ORM (Group-1 Admira fusion, n=10) and BF (Group-2 Filtek BF, n=10) composite materials were used to prepare and restore Class-V cavities. The teeth were subjected to thermocycling and immersed in 1% methylene blue dye solution. Along the lateral walls of each sectioned specimen, depth of dye penetration was measured under the stereo microscope. A total of 20 rectangular (25x2x2 mm) and 20 disc (10x2 mm) shaped specimens of the above-mentioned materials were fabricated. Specimens of Flexural Strength (FS) were tested with the universal testing machine and Vickers hardness tester used for Surface Hardness (SH) evaluation. The data was statistically analysed using an unpaired t-test. Results: Total of 20 extracted premolars were analysed. On inter-group comparison, it was observed that mean dye penetration was lowest for Group-1 (0.6±0.69) compared to Group-2 (2±0.81) and the difference observed was statistically significant (p=0.001). BF exhibited a lower FS of 211.69±43.9 compared to Ormocer 326.19±90.3, the difference is statistically significant (p=0.001). However, BF exhibited a higher SH of 38.3±0.15 compared to Ormocer 33.70±0.86, and the difference is statistically significant (p-value&lt;0.001). Conclusion: Ormocer exhibited improved marginal integrity and also higher FS compared to BF resin restorative materials. However, BF exhibited higher SH values compared to Ormocer.

A Blinded Comparative Study of Four Commercially Available LEDs and a Laser Light Curing Device.

This study determined the effectiveness of five light-curing units (LCUs; four light-emitting diode [LED] and one laser) used on different settings to photo-activate four conventional resin-based composites (RBCs). A total of 108 RBC specimens were photo-activated in a white Delrin mold representing a mesial-occlusal-distal (MOD) class II restoration in a molar tooth. The proximal boxes were 5 mm deep, and the mesial-distal length was 12 mm. Immediately after photo-curing, the RBC specimens were immersed in a solvent to remove the uncured materials, after which they were photographed and deidentified. A Research Electronic Data Capture survey was created using these images and sent to respondents who blindly assessed the ability of the various LCUs to photo-cure the MOD restorations. There were significant differences in how the five curing lights had cured RBCs. One-way analysis of variance (ANOVA), pairwise t-test, Welch's one-way ANOVA, and Kruskal-Wallis rank test in the blinded survey data showed significant differences between the LED curing lights used for two 10-second cures and the laser curing light used for 1 second, and LED lights at lower settings. There was a significant difference in how the curing lights could photo-cure the RBCs used in this study. The laser curing light used for 1 second produced the worst results in all four RBCs.

Effect of Pre-Heating on the Monomer Elution and Porosity of Conventional and Bulk-Fill Resin-Based Dental Composites.

The pre-heating of dental resin-based composites (RBCs) improves adaptability to cavity walls, reducing microleakages. However, the rapid cooling of the pre-heated RBC may change the polymerization kinetics, and thus the final network configuration of the RBC. It is well known that unreacted monomers remaining in the set RBC can leach into the oral cavity. However, it is still not clear how the pre-heating and cooling of RBCs alter monomer elution (ME). Thus, the purpose was to determine the ME from room-temperature and pre-heated RBCs, in addition to determining the closed porosity (CP) volume. Bulk-filled RBCs and layered conventional RBC samples were prepared. The pre-polymerization temperature was set at 24 °C and 55/65 °C. The ME from RBC samples was assessed with high-performance liquid chromatography using standard monomers. CP was measured with micro-computed tomography. ME decreased significantly from bulk fills and increased from layered samples as a result of pre-heating. Pre-heating was unfavorable in terms of CP in most RBCs. Based on the effect size analysis, ME and CP were greatly influenced by both material composition, pre-polymerization temperature, and their interaction. While the pre-heating of high-viscosity bulk-fill RBCs is advantageous from a clinical aspect regarding biocompatibility, it increases CP, which is undesirable from a mechanical point of view.

Are inert glasses really inert?

The aim of this study was to investigate the degradation of inert glass fillers which are commonly used in conventional resin-based composites to provide radiopacity, reduce the polymerization shrinkage and improve the mechanical properties. 75mg of five different glass powders (1µm) was immersed separately into 50mL of acetic acid (pH 4) and tris buffer (pH 7.4) for up to 4 weeks. At each time point the glass powder was filtered and dried for characterization using ATR-FTIR and XRD to assess the degradation behavior and crystallization. ICP-OES, ISE and pH measurements were performed on the supernatant solutions to monitor the pH and ion release. Although FTIR and XRD analysis showed no significant glass degradation or crystallization upon immersion, there was a substantial release of ions from the inert fillers, especially from BABFG and CDL. Barium release for these fillers were 270 and 165ppm respectively. G018-373 glass presented the lowest ion release followed by GM27884 and BABG. The ion release was more pronounced in acidic conditions compared to neutral conditions apart from the fluoride release. Inert glasses are not as inert as previously thought. This may result in leaching of ions, potentially causing toxicity, reduction in mechanical properties, increased wear and subsequent failure of the composite material. The ions released from the inert glass may interfere with other glass fillers such as bioactive glass fillers, inhibiting degradation of the bioactive glass, beneficial ion release from the bioactive glass, pH neutralization and apatite formation.

Quality of Cure in Depth of Commercially Available Bulk-fill Composites: A Layer-by-layer Mechanical and Biological Evaluation.

Despite their popularity, the use of bulk-fill composites remains controversial, both in terms of their properties and their in-depth development. The objectives of the present work were (1) to provide a more comprehensive evaluation of the quality of cure in depth of commercially available bulk-fill composites by combining various key mechanical and biological characterization methods, (2) to evaluate the inter-material differences when optimally cured, and (3) to evaluate the efficiency of an antioxidant-N-acetyl-cysteine (NAC)-to restrain the adverse effects of the leached components on cell viability. Nine bulk-fill composites (including flowable and high-viscosity materials) were investigated and compared to two conventional resin-based composites, one flowable and one high-viscosity restorative material. The materials were injected or packed into Teflon molds of various configurations, up to 6 mm material thickness. They were then light-cured from the top for 20 seconds with Bluephase G2 (Ivoclar Vivadent, irradiance = 1050 mW/cm2). The following physico-mechanical properties were measured for the upper (0-2 mm), intermediate (2-4 mm), and lower (4-6 mm) layers: degree of conversion using Raman Spectrometry (DC, in %), microhardness using a Vickers micro-indenter before (VHN dry) and after 24 hours of storage in ethanol (VHN EtOH), and flexural strength (in MPa) and flexural modulus (in GPa) using a three-point bend test. Each composite layer and an uncured layer were also stored for one week in a standard cell growth medium to generate conditioned media. Human dental pulp cells were then cultured for 24 hours with the latter and cell viability was measured using an MTS assay. A similar experiment was repeated with conditioned media produced in contact with uncured composites, with and without the addition of 4 mM NAC. The data were subjected to a Shapiro-Wilk test, then one-way ANOVA or Kruskal-Wallis test, followed either by Tukey's test (inter-material comparison) or by Dunnett's or Dunn's test (comparison between layers relative to the upper one). The level of statistical significance was set at 0.05. Some materials (EverX, X-traF, VenusBF, X-traB) did not show any significant differences (p>0.05) for any of the properties considered between the intermediate layers compared to the upper one (considered as reference). Others displayed significant differences, at least for some properties, highlighting the value of combining various key mechanical and biological characterization methods when investigating the quality of cure in depth. Significant inter-material differences (p<0.05) were observed when comparing the properties of their upper layer, considered as "optimally" polymerized. Hence, one needs to consider the absolute property values, not only their relative evolution concerning layer thickness. Finally, the use of NAC appeared as beneficial to reduce the risk of harmful effects to dental pulp cells, especially in case of excessive thickness use, and may therefore be of potential interest as an additive to composites in the future.

Characterization of universal chromatic resin-based composites in terms of cell toxicity and viscoelastic behavior

ObjectivesA current trend to simplify dental restorative procedures is toward using universal chromatic light-cured resin-based composites (RBCs) designed to adapt esthetically to various clinical situations. This study offers a comparative characterization of the mechanical and cytotoxic behavior of such materials that use different techniques to adjust their optical properties (e.g., structural color instead of pigment addition), have different filler systems but are based on a comparable organic matrix. MethodsThe structural appearance of the filler systems was assessed by scanning electron microscopy. Various quasi-static and viscoelastic parameters were evaluated at clinically relevant frequencies (0.5–5 Hz) using an instrumented indentation test with a Dynamic Mechanical Analysis (DMA) module. Cytotoxicity on human gingival fibroblasts (HGF-1), when exposed to eluates from tested RBCs specimens (up to one month), was assessed using a WST-1 colorimetric proliferation assay. Multifactor analysis of variance was applied to compare the parameters of interest (Martens, Vickers, and indentation hardness; elastic and total indentation work; creep, indentation depth; storage, loss, and indentation moduli; loss factor; cell viability) between analyzed RBCs, loading frequencies, and eluate age. ResultsStructural particularities of the filler systems are directly reflected in the mechanical behavior of the analyzed materials. Changes in the filler system, necessary to achieve structural color, generally resulted in lower mechanical properties but a better ability to absorb shock. In contrast, the cytotoxicity was comparable. SignificanceBased on the performed characterization, universal chromatic RBCs fits in the conventional RBCs class to expect comparable clinical behavior.

Marginal Adaptation of Different Bulk-fill Composites: A Microcomputed Tomography Evaluation.

ObjectivesIn the last decade, bulk-fill materials were introduced to allow resin-based composites (RBC) in one layer (up to 4-5 mm thick) with optimum polymerization. We sought to evaluate the adaptation ability of different bulk-fill composites resin (CRs)and restoration marginal integrity.MethodsA total of 28 caries-free and crack-free human molars underwent mesio-occlusal-distal cavity preparation. Each sample prepared the mesial margins on enamel, and the distal margins were extended into dentin. Teeth were then randomly distributed into four groups (n = 7 per group) according to the CR used to restore the cavity. Three bulk-fill CRs—Smart Dentin Replacement Flow+, 3M™ Filtek™ One Bulk Fill (FBF), and Tetric® N-Ceram Bulk Fill (TBF)—and one conventional CR (CC)—Filtek™ Z350—were used. The teeth were then subjected to aging via thermocycling, followed by cyclic loading. Finally, the volumetric width of the interfacial gap at the tooth-restoration interface was measured using a microcomputed tomography (µ-CT) analysis.ResultsSDR demonstrated the smallest gap volume among all tested CRs, followed by CC in enamel and TBF in dentin after aging. FBF showed the highest gap volume. There was no statistically significant three-way interaction between surface, aging, and material (p > 0.050).ConclusionsIt is safe to suggest using bulk-fill RBC in deep class II cavities instead of conventional layered RBC when dealing with dentin margins. However, further clinical investigation is required.

32 - A New 3D Volume-Based Method for Assessing Composites Curing Depth

Develop a new method to evaluate the curing depth of conventional and bulkfill composites based on the total volume of cure (VOC) and compare to the ISO 4049 depth of cure standard (DOC) with different mold diameters. A total of 100 samples were made from 2 bulkfill composites and 2 conventional resin-based composites, 25 samples for each material, with 5 samples per diameter of 10 mm, 8 mm, 6 mm, 4 mm, and 2 mm using stainless steel molds of 10 mm length. An individually designed 3D printed frame was attached to a metal plate using stainless steel screws in order to secure a fixed position of the molds in relation to the Valo cordless LED LCU which was clamped to the metal plate with an adjustable arm. ISO DOC was measured according to ISO 4049. Then the domed cylinders were scanned and the VOC% was measured in the Autodesk Meshmixer software using the STL files obtained from the scanned data using a E4D planmeca scanning device. Geomagic software was used for 3D comparison of curing profiles of 10 mm diameter samples. Two-way analysis of variance (ANOVA) and Tukeys test for pairwise comparison was used to analyze the data. A difference plot assembled in the geomagic software was used for 3D comparison of curing profiles ISO 4049 method that measures the center of the specimen does not represent the full potential of the LCU. With a 10 mm ∅ window of the LCU, 10 mm, 8 mm and 6 mm molds give identical results for DOC and VOC%. The difference between the bulkfill and regular composites was significant (p<0.05); bulkfill DOC was between 1.9x (Filtek) and 2.4x (Tetric) higher than for the regular composites. DOC and VOC% are both negatively influenced by smaller mold diameter (p<0.05). The non-homogenous nature of the LCU did not influence the VOC% and DOC. The non-homogenous nature beam profile of the LCU unit had an influence on the 3D curing profiles of the specimen, which can be explained with the higher absorption of the violet light from the composite Most of contemporary LCUs have diameters of the light exiting window >4 mm. since there were significant differences in DOC between ∅ 6 mm and ∅ 4 mm molds. ISO 4049 under-represents the DOC. The influence on the LCUs curing profile on ∅ 6 mm molds should be investigated in the future. The experiment should be repeated with other LCUs than the one used in this study. Results for the ISO DOC and volume of cure percent (VOC %) for different mold diameter samples for 4 materials Filtek Bulkfill one(FBO), Tetric Powerfill(TPF), Filtek Supreme (FS), and Tetric Prime(TP).

A comparative study of the 5 mm-layer Vickers hardness model with bulk-fill resin-based composites

Aim: The aim of this study was to compare the Vickers hardness numbers (VHNs) of two bulk-fill resin-based composites (BFRBC) and a conventional hybrid resin-based composite (RBC) through the layers of a 5mm thickness model with two different light-curing time intervals.&#x0D; Methodology: In the present study, a sonic-activated and dual-cure BFRBC, and a conventional hybrid RBC were used. Semi-cylindrical specimens 4 mm in radius and 5 mm in height were prepared using a two-piece stainless-steel mold (n=10). The BFRBCs allowed a single 5mm increment to be introduced into the molds, whereas hybrid RBC was incremented (2+2+1 mm). Two different time intervals were applied for the light-curing (irradiance of 1200 mW/cm2) of each material (hybrid-sonic-activated bulk-fill, 20 s and 40 s; dual-cure bulk-fill, 7 s and 15 s). VHN measurements were carried out from top to bottom at every 1 mm of the specimen thickness. Data were analyzed using three-way and two-way ANOVA for the VHN and bottom/top ratios and Bonferroni correction for multiple comparisons (p=0.05).&#x0D; Results: For each layer and time interval groups, there was a significant difference between the materials. The highest VHN was found within hybrid groups, whereas dual-cure bulk-fill groups showed the lowest results. Sonic-activated bulk-fill had the lowest bottom/top ratios, which were significantly different from those of the other materials. There was no significant difference between the different time intervals for bottom/top ratios within each material.&#x0D; Conclusion: Increased irradiation intervals positively affected the VHN of hybrid and dual-cure bulk-fill. BFRBCs showed clinically acceptable bottom/top hardness ratios.&#x0D; &#x0D; How to cite this article: Aytaç Bal F, Ağaccıoğlu M, Demir O. A comparative study of the 5 mm-layer Vickers hardness model with bulk-fill resin-based composites. Int Dent Res 2021;11(2):172-9. https://doi.org/10.5577/intdentres.2021.vol11.no3.6&#x0D; &#x0D; Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Mini-iFT Confirms Superior Adhesive Luting Performance using Light-curing Restorative Composites.

To validate the rationale of using a conventional light-curing resin-based composite (RBC) to lute thick indirect restorations by measuring mini-interfacial fracture toughness (mini-iFT). Freshly exposed dentin of extracted third molars (n = 64) was immediately sealed with a thin layer of an experimental RBC with a 50 wt% or 75 wt% (IDS) filler load. Two- or 6-mm-thick CAD/CAM composite blocks were luted onto IDS using either pre-heated light-cure or dual-cure luting RBC, with the latter having served as control. Samples were cut into sticks, upon which a notch was prepared at the interface between IDS and luting RBC, prior to being submitted to a 4-point bending test to determine mini-iFT. The results were analyzed using a mixed linear model (LME). Failure mode at the fractured interface was determined using scanning electron microscopy (SEM). LME revealed that mini-iFT was not significantly affected by the composite block thickness (p = 0.39), but by the luting RBC (p < 0.0001) and the IDS RBC filler load (p = 0.0011). Mini-iFT was higher with 50 wt% filler-loaded RBC IDS and when luted using the light-curing RBC. This work provides the proof of concept that 2- and 6-mm-thick indirect restorations can safely be adhesively luted with pre-heated conventional light-cure RBC under controlled light-irradiation conditions. This strategy even seems beneficial in terms of mini-iFT compared to using a dual-cure luting RBC. IDS with lower filler content also appeared more favorable.

Effect of extended light activation and increment thickness on physical properties of conventional and bulk-filled resin-based composites.

To evaluate the biaxial flexural strength (BFS), flexural modulus (BFM), and Knoop microhardness (KHN) of incremental and bulk-filled resin-based composites (RBCs) using extended curing exposure times. Disc specimens (n = 8; 6-mm diameter) were fabricated using three stacked molds (0.5-mm thick for the top and bottom molds, and a 1-mm-thick center mold for the conventional and 3-mm thick for the bulk-fill RBCs). Conventional (Tetric EvoCeram/TCE and Filtek Z250/FIZ) and bulk-fill RBCs (Tetric EvoCeram Bulk Fill/TBF and Filtek One Bulk Fill Restorative/FOB) were evaluated. The stacked RBC-filled molds were light-cured for (1) the manufacturer-recommended exposure (MRE) duration; (2) 50%, and (3) 100% extension of the MRE. The BFS, BFM, and KHN of the top and bottom discs were measured. BFS and BFM were analyzed by three-way ANOVA (material*curing time*depth) and Tukey's post hoc (α = 0.05). KHN was analyzed by two-way ANOVA (curing time*depth) and Tukey's post hoc (α = 0.05). Extending the exposure duration did not change the BFS and BFM on the top of the RBCs, but the BFS and KHN increased at the bottom of bulk-fill RBCs. For the conventional RBCs, TCE showed the highest increase on BFS at the bottom, going from 53.6MPa at T1 to 69.9 at T3. Among the bulk-fill RBCs, FOB presented the highest increase on the bottom BFS (T1: 101.0 ± 19.9MPa, T3: 147.6 ± 12.9MPa). For all RBCs and exposure times, BFS and KHN were lower at the bottom. Only FIZ and FOB reached a bottom-to-top hardness ratio of 80%, at T3 and T2. A significant increase on the BFS and KHN on the bottom of bulk-fill RBCs can be observed when the time of exposure to the curing light is double the MRE. However, extended exposure does not eliminate differences on the BFS and KHN between the shallow and deep regions of RBCs. TCE and TBF failed to reach an acceptable B/T hardness ratio at all evaluated exposure times. Mechanical properties of RBCs can be affected by insufficient polymerization, specially at deeper regions of the increment. Therefore, clinicians should consider applying twice the MRE to curing-light to polymerize the maximal increment thickness of bulk-fill RBCs.