Clinical performance and chemical-physical properties of bulk fill composites resin -a systematic review and meta-analysis

Comparative analysis of conversion and crosslinking degree in bulk-fill, monochromatic, and ORMOCER composites

Bulk-fill, monochromatic, and ORMOCER composites were introduced in restorative dentistry with the aim of reducing clinical time and/or alleviating contraction stresses at the interface between the tooth and restoration. While the conversion and immediate properties of these materials are comparable to conventional composites, studies evaluating their long-term properties and the structure of the polymer matrix are lacking. The objective of this study was to evaluate the degree of conversion and, indirectly, the crosslink density of conventional, bulk-fill, monochromatic, and ORMOCER resin composites. The degree of conversion was measured using Fourier-transform infrared spectroscopy (FTIR). Flexural strength, elastic modulus, and hardness were measured both dry (24 h) and after ethanol storage (24 h) using three-point bending and Knoop microhardness testing, respectively. Sorption and solubility were determined by changes in mass before and after immersion in water and drying. Data were analyzed using one-way or two-way ANOVA (material or material/storage conditions). The degree of conversion was statistically similar across all materials. For composites from the same manufacturer, no significant differences were observed in the reduction of mechanical properties after ethanol storage between bulk-fill and monochromatic composites, although differences were noted for the ORMOCER material. Sorption and solubility varied among most composites from the same manufacturer, suggesting subtle differences in composition. Therefore, it can be concluded that, for composites from the same manufacturer, the degree of crosslinking was similar between bulk-fill and monochromatic composites, indicating comparable polymeric structures. The same was not observed for the ORMOCER material, although it exhibits properties similar to other conventional composites.

Effect of using different materials and restorative techniques on cuspal deflection and microleakage in endodontically treated teeth

BACKGROUND

This study aimed to evaluate the effects of different restorative techniques and materials on cuspal deflection and microleakage in MOD restorations. Eight groups were tested using incremental and bulk-fill techniques, with or without fiber reinforcement. The restorative materials included Filtek Z250 and Filtek Bulk-fill Posterior, while reinforcement materials such as Interlig glass fiber, EverX Posterior, and Surefill SDR were incorporated to assess their impact.

METHODS

In total, 96 freshly extracted, sound human maxillary first premolars were selected and stored in 0.1% thymol solution at 37 °C. The teeth were randomly assigned into eight groups (n = 12). Standardized MOD cavities were prepared, followed by endodontic treatment and sealing with glass ionomer cement. The groups were as follows: Group 1-Filtek Z250 applied incrementally in 2-mm layers; Group 2-U-shaped Interlig glass fiber followed by incremental Filtek Z250; Group 3-Filtek Bulk-fill Posterior using the bulk technique; Group 4-U-shaped Interlig glass fiber followed by Filtek Bulk-fill Posterior; Group 5-EverX Posterior followed by incremental Filtek Z250; Group 6-EverX Posterior followed by Filtek Bulk-fill Posterior; Group 7-Surefill SDR followed by incremental Filtek Z250; and Group 8-Surefill SDR followed by Filtek Bulk-fill Posterior. Cuspal deflection was measured using a digital micrometer with 0.05 μm precision. Microleakage was assessed using a 0.5% basic fuchsin dye solution at 37 °C for 24 h, followed by sectioning and examination under magnification.

RESULTS

The lowest mean cuspal deflection was observed in Group 2 (15.8 μm), while the highest was in Group 5 (27.2 μm). Statistically significant differences were observed in cuspal deflection across the groups and over time (p < 0.05). Significant differences in microleakage scores were also found among the groups, indicating the impact of restorative materials and techniques on these outcomes (p < 0.05).

CONCLUSION

This study demonstrated that Filtek Z250 and Filtek Bulk-fill Posterior showed different effects on cuspal deflection and microleakage. The use of glass fiber and EverX Posterior improved restoration performance by reducing polymerization effects. Surefill SDR also reduced cuspal deflection due to its low polymerization shrinkage. Clinically, selecting the appropriate restorative materials and techniques based on the extent of tooth structure loss can improve long-term outcomes.

Design and Development of Infiltration Resins: From Base Monomer Structure to Resin Properties

The resin infiltration concept is one of the most widely used minimally invasive restorative techniques in restorative dentistry with the most outstanding therapeutic effect, and it is also one of the key research directions in restorative dentistry. "Infiltration resin" is the specialty restorative material for the technology, which is the key factor to success. The specialized restorative material is commonly known as "infiltrant/infiltration resins" "resins infiltrant" "infiltrant" or "resins," which will be consistently referred to as "infiltration resins" throughout the article. The paper aims to provide a comprehensive overview of infiltration resins by introducing the development of their therapeutic mechanisms, basic components, current challenges, and future trends, Based on existing literature, we analyze and compare how changes in the base monomer's structure and ratio affect the effectiveness of infiltration resins, from the material's structure-effective relationship. After compiling the information, the existing solution strategies have been listed to offer substantial support and guidance for future research endeavors.

Diversity of short-term DC outcomes in bulk-fill RBCs subjected to a 3 s high-irradiance protocol

OBJECTIVES

To determine the short-term (5 min) initial effects of a high-irradiance light-curing (LC) protocol on light transmission (LT%), radiant exposure (RE) and degree of conversion (DC%) of different bulk-fill resin-based composites (RBCs).

MATERIALS AND METHODS

Six bulk-fill composites with different viscosities were investigated: OBF (One Bulk Fill, 3 M), EB (Estelite bulkfill,Tokuyama), PFill, PFlow, ECeram and EFlow (PowerFill, Poweflow, Tetric EvoCeram bulkfill, Tetric Evoflow bulkfill, Ivoclar), subjected to different LC protocols: one ultra-high-intensity (3 W/cm2 -3 s via PowerCure LCU) and two conventional (1.2 W/cm2 -10 s and 20 s via PowerCure and Elipar S10 LCUs). Specimens (n = 5) were polymerized within their molds (ϕ5 mm × 4 mm depth) to determine LT% and RE at 4 mm using a MARC-LC spectrometer. For real-time DC% measurements by FTIR, similar molds were utilized. Data were analyzed by one-way ANOVA and Tukey post-hoc tests at 5 % significance.

RESULTS

Regardless of the applied LC protocols, OBF and low-viscosity RBCs (EB, PFlow and EFlow) had the lowest and highest LT%, RE, DC% and RPmax, respectively. RE results of all RBCs were in the same sequence: Elipar-20 s > PCure-10 s > PCure-3 s. DC% of PFill and PFlow displayed no significant difference between the applied LC protocols (p > 0.05). The polymerization kinetic in all materials was well described by an exponential sum function (r2 varied between 0.85 and 0.98), showing a faster polymerization with the PCure-3 s protocol.

SIGNIFICANCE

The measurement of LT% and DC% at 5 min gave an insight into the developing polymerization process. The initial response of these bulk-fill composite to a high-irradiation protocol varied depending on their composition and viscosity, being faster for low viscosity materials. Nevertheless, even though multiple resin composites are designed to be efficient during photopolymerization, care should be taken when selecting materials/curing protocol.

Characterization of experimental resin composites with cholesteryl methacrylate organic matrix - Part 2

OBJECTIVE

The aim of this study was to evaluate the degree of conversion (%), flexural strength (MPa), elastic modulus (GPa), compressive strength (MPa), Knoop microhardness (KHN), post-gel shrinkage (%) and prediction of ideal concentration of cholesteryl methacrylate (CM) in experimental resins.

METHODS

Four formulations were manipulated (F): F1, control group, (0 % CM); F2 (15 % CM); F3 (19.8 % CM) and F4 (30 % CM). Bis-GMA and CM percentages were determined using Statistica™ software. For the degree of conversion test, Raman spectroscopy was used. To testing flexural strength, elastic modulus and compressive strength, a universal testing machine was used. For the Knoop microhardness test five indentations were made in each sample. Post-gel shrinkage was determined using the strain gauge method. Statistica™ software processed all data obtained in this study. Results were submitted to one-way ANOVA and Tukey's post hoc tests (α = 0.05).

RESULTS

Better performance was observed for F2 (15 % CM) and F3 (19,8 % CM) for degree of conversion, elastic modulus and post-gel shrinkage. For Knoop microhardness F2 (15 % CM), F3 (19,8 % CM) and F4 (30 % CM) showed higher values than F1 (0 % CM). For flexural strength F1 (0 % CM) and F3 (19,8 %) were similar and F4 showed the lowest values and for compressive strength F1 (0 % CM) showed the highest values. For mixture designs analysis data, concentrations ≤ 25 % of CM would provide better results.

SIGNIFICANCE

Addition of CM at concentrations lower than 30 % contributed to a significant increase in the degree of conversion, microhardness values, elastic modulus and reduction of post-gel shrinkage.

Clinical Outcomes of Bulk-Fill Resin Composite Restorations: A 10-Year Mapping Review and Evidence Gap Map

OBJECTIVE

To map the evidence regarding the clinical performance of posterior restorations with bulk-fill resin composites and identify research gaps.

MATERIALS AND METHODS

This mapping review was conducted following PRISMA-ScR guidelines for scoping reviews, and its protocol was registered on the Open Science Framework platform. Systematic searches were conducted, considering studies published between 2013 and February 2024 in the PubMed, Embase, and Cochrane databases. Clinical studies investigating the performance of bulk-fill resin composite restorations in class I and/or class II preparations with increments of 4 to 5 mm were included.

RESULTS

A total of 147 articles were identified, and based on the eligibility criteria, 26 studies were selected for descriptive analysis. Of the reviewed studies, 73% (n = 19) investigated high-viscosity bulk-fill composites, while 30% (n = 8) focused on low-viscosity bulk-fill composites. Evaluation periods ranged from 1 week to 10 years. Reported annual failure rates varied from 0% to 3%, with survival rates between 78.9% and 100%.

CONCLUSIONS

Bulk-fill resin composites of high viscosity were the most analyzed in the published studies, with evaluation periods of up to 10 years. The review of available scientific evidence showed clinically acceptable performance for composite bulk-fill restorations, with high survival rates and minimal annual failure rates. There is a need for long-term clinical studies on bulk-fill resin composites.

CLINICAL SIGNIFICANCE

This review demonstrates that both high and low-viscosity bulk-fill resin composites exhibit satisfactory clinical performance, which can help clinicians optimize chairside time. However, it is important to highlight the need for further studies with longer follow-up periods.

The Effect of Inorganic Filler Content on the Properties of BPA-Free Bulk-Fill Dental Resin Composites

This study aimed to enhance the performance of dental resin composites (DRCs) by increasing the content of inorganic fillers while addressing potential health risks associated with Bisphenol A (BPA). To achieve this, the BPA-based resin monomer Bis-GMA was replaced with BPA-free Bis-EFMA. The study then explored the impact of varying inorganic filler contents on the physiochemical properties of Bis-EFMA-based bulk-fill dental resin composites (BF-DRCs). Four distinct Bis-EFMA-based BF-DRCs were formulated, each with different inorganic filler contents ranging from 70 wt% to 76 wt%. The study tested the depth of cure (DOC), double-bond conversion (DC), water sorption (WS), solubility (SL), and cytotoxicity of the system. It notably investigated the effects of increasing filler content on mechanical properties through flexural strength (FS), flexural modulus (FM), Vickers microhardness (VHN), and wear resistance, as well as the impact on polymerization shrinkage, including volumetric shrinkage (VS) and shrinkage stress (SS). To assess the commercial application potential of Bis-EFMA-based BF-DRC, the research used the commercially available BF-DRC Filtek Bulk-Fill Posterior (FBF) as a control. The results indicated that a higher filler content did not affect the DOC of Bis-EFMA-based BF-DRCs. Inorganic fillers at higher concentrations significantly enhanced overall mechanical properties while significantly reducing volumetric shrinkage (VS; p < 0.05). When the concentration of inorganic fillers in the resin system reached 76 wt%, most of the performance of the Bis-EFMA-based BF-DRC surpassed that of the commercial control FBF, except for FS, FM, and SS. These findings highlight the potential of Bis-EFMA-based BF-DRC as a long-term restorative material for dental applications.

Efficiency of bulk-fill versus conventional resin-based composite in class II restorations: A dental student perspective

Purpose/objectives

The aim of the study was to evaluate the effect of two distinct light-polymerization protocols, used by dental students, on the placement time and polymerization efficiency of bulk-fill (BF) and conventional (CRC) resin-based composites (RBCs).

Methods

Thirty dental students participated in this study. Each student was asked to complete four Class II RBC restorations using two different types of RBCs (BF and CRC) paired with two distinct light-polymerization protocols: one using 1200 mW/cm2 irradiance (P1200) and one using 800 mW/cm2 irradiance (P800). Manufacturer instructions for curing times relative to these irradiance levels were adhered to. The restorations were retrieved, sectioned and Vickers microhardness (VMH) was measured at specific reading points. The placement time was recorded for each procedure. Multivariate analysis of variance and Bonferroni post hoc test were used for data analysis.

Results

Bulk-fill RBCs were associated with significantly shortened placement times (P < 0.001). VMH values of CRC-P800 were significantly higher compared to all other groups (P < 0.02). Across all groups tested, the VMH values at the deepest reading points exceeded those at the occlusal surfaces by over 80 %.

Conclusions

The use of BF RBCs with a P1200 light-polymerization protocol reduced students' procedural times while maintaining effective polymerization of the restorations.

Clinical evaluation of a new chemically-cured bulk-fill composite in posterior restorations: 6-month multicenter double-blind randomized clinical trial

OBJECTIVE

To evaluate the postoperative sensitivity (POS), as well as the clinical performance of posterior restorations using a new chemically-cured bulk-fill composite (Stela Automix and Stela Capsule, SDI) comparing with a light-cured bulk-fill composite after 6 months.

METHODS

Fifty-five participants with at least three posterior teeth needing restoration were recruited. A total of 165 restorations were performed on Class I or Class II cavities. After the application of Stela primer, the chemically-cured composite (Stela Automix or Stela Capsule) was inserted. For the light-cured composite group, a universal adhesive (Scotchbond Universal) was applied with a bulk-fill composite (Filtek One). Participants were evaluated for spontaneous and stimulated POS in the baseline, after 48 h, 7 days, and 6 months. Additionally, each restoration was assessed using the updated version of FDI criteria after 6 months. The differences in the proportions of the groups were compared by Cochran test statistics (α = 0.05).

RESULTS

Both chemically-cured composites showed a lower risk of POS compared to the light-cured composite at baseline and up to 48 h (p < 0.04). A significantly lower surface luster and texture was observed for the Stela Capsule composite compared to the light-cured bulk-fill composite (baseline and 6 months; p = 0.03). A significant color mismatch was observed for the light-cured bulk-fill composite compared to the chemically-cured composites (baseline and 6 months; p = 0.03). No significant differences were observed in any other item evaluations (p > 0.05).

CONCLUSION

Chemically-cured composites exhibit lower postoperative sensitivity and less color mismatch compared to a light-cured bulk-fill composite after 6 months of clinical service.

CLINICAL SIGNIFICANCE

The chemically-cured composites appear to be an appealing option for restoring posterior teeth, as they exhibit lower postoperative sensitivity compared to a light-cured bulk-fill composite, both at baseline and up to 48 h, and less color mismatch.

Comparison of degree of conversion performance of bulk-fill resin composites: A systematic review and network meta-analysis of in vitro studies

OBJECTIVES

To systematically compile data on the degree of conversion (DC) for bulk-fill composites using a network meta-analysis.

METHODS

A systematic search for in vitro studies of DC of bulk-fill composites was performed in PubMed, Web of Science, Scopus, and Open Grey. Risk of bias within studies and due to missing evidence was assessed using the Joanna Briggs Institute scoring system and ROB-MEN tool, respectively. The primary outcome was the DC of bulk-fill composites. Surface Under the Cumulative Ranking curve (SUCRA) was used to rank relative performance. Inconsistencies in the model were investigated to ensure its validity and the level of confidence in the network meta-analysis (CINeMA) was assessed.

RESULTS

A total of 28 studies were included in the quantitative analysis. The average DC values (%) for 0-h/top, 0-h/bottom, 24-h/top, and 24-h/bottom were 59.09, 57.14, 66.73, and 63.87, respectively. According to their SUCRA ranking, the best-performing composites were: SonicFill, Venus Bulk Fill, and SDR (0-h/top), Reveal HD, i-Flow Bulk Fill, and Venus Bulk- Fill (0-h/bottom), Venus Bulk Fill, SDR, and QuiXfil (24-h/top), and Venus Bulk Fill, Aura Bulk Fill, and i-Flow Bulk Fill (24-h/bottom). Incoherence between direct and indirect evidence was identified as the most significant factor affecting confidence.

CONCLUSIONS

DC values of bulk-fill composites were within the range commonly reported for previous generations of "conventional" composites, with flowable composites tending to perform better than sculptable composites. High variability in DC data was observed, which may be attributed to incompletely understood methodological differences.

CLINICAL SIGNIFICANCE

DC is a fundamental parameter that influences multiple mechanical and biological properties of resin composites and is particularly relevant for the group of bulk-fill composites that are designed for use in thick layers.

Five-year survival of class II restorations with and without base bulk-fill composite: a retrospective cohort study

OBJECTIVE

This study aimed to determine the survival of class II composite restorations in premolars and molars with and without base bulk-fill composite in general dental practice.

MATERIALS AND METHODS

We collected data from the electronic patient files of the Public Dental Services in the City of Oulu, Finland. The timespan of data collection was from August 15th, 2002, to August 9th, 2018. The data consisted of class II composite restorations both with and without base bulk-fill composite. We compared the survival of these restorations using Kaplan-Meier survival curves, the log-rank test, survival rates, and the Wilcoxon signed ranks test.

RESULTS

We observed 297 restorations in 96 patients. The five-year survival rates for restorations with and without base bulk-fill composite were comparable in premolars (77.5% and 77.4%, respectively) but different in molars (69.9% and 57.8%, respectively, p = 0.069). In molars, the restorations with base bulk-fill composite exhibited a higher survival rate in 14 patients, whereas in 11 patients the restorations without base bulk-fill composites exhibited a higher survival rate. In 24 patients the survival rates were similar for restorations with and without the base bulk-fill composite (p = 0.246).

CONCLUSIONS

The restorations with and without base bulk-fill composite had similar longevity.

CLINICAL RELEVANCE

Base bulk-fill composites are safe to use in general practice due to their similar survival rates compared to conventional composites.

Influence of Different Application Modes of a Universal Adhesive System on the Bond Strength of Bulk-Fill Composite Resin to Enamel and Dentin in Primary Teeth

OBJECTIVES

The objective of this study was to assess how the application mode of a universal adhesive system affects the microshear bond strength (μSBS) of bulk-fill and conventional composite resins to enamel and dentin in primary teeth.

METHODS

A total of 80 caries-free primary second molars were randomly assigned to eight experimental groups (n = 10) based on the bonding substrate (enamel or dentin), the application mode of the universal adhesive system (etch and rinse [E&R], or self-etch [SE]), and the type of composite resin used (bulk-fill or conventional). After bonding the composite resin to enamel or dentin, the μSBS of the bonded composite resins was measured.

RESULTS

The mean μSBS value of bulk-fill composite resin was significantly higher than that of conventional composite resin for both enamel and dentin substrates, regardless of the application mode (p < 0.001). An interaction effect between the bonding substrate and the application mode of the adhesive system was observed, indicating a significant relationship (p < 0.001). The highest μSBS values for primary teeth enamel were achieved using the E&R mode with bulk-fill composite resin, while for dentin specimens, the SE mode with bulk-fill composite resin yielded the highest μSBS values. The μSBS of the E&R group was significantly higher than that of the SE group for enamel specimens (p < 0.001), whereas the μSBS of the SE group was significantly higher than that of the E&R group for dentin specimens (p < 0.001).

CONCLUSION

Bulk-fill composite resin demonstrated higher μSBS in comparison to conventional composite resin. The universal adhesive system exhibited superior performance in the SE mode compared to the E&R mode on primary dentin. Pre-etching the enamel before the application of the universal adhesive enhanced the μSBS to primary teeth enamel, highlighting the importance of selectively acid etching the enamel of primary teeth.

A Historical Perspective on Dental Composite Restorative Materials

This review article will discuss the origin of resin-based dental composite materials and their adoption as potentially useful adjuncts to the primary material used by most dentists for direct restorations. The evolution of the materials, largely driven by the industry's response to the needs of dentists, has produced materials that are esthetic, strong, and versatile enough to be used in most areas of the oral cavity to replace or restore missing tooth structures. Significant advancements, such as the transition from chemical to light-curing materials, refinements in reinforcing particles to produce optimum polishing and wear resistance, formulating pastes with altered viscosities to create highly flowable and highly stiff materials, and creating materials with enhanced depth of cure to facilitate placement, will be highlighted. Future advancements will likely reflect the movement away from simply being a biocompatible material to one that is designed to produce some type of beneficial effect upon interaction within the oral environment. These new materials have been called "bioactive" by virtue of their potential effects on bacterial biofilms and their ability to promote mineralization of adjacent tooth structures.

An evaluation of dental paste-like bulk-fill composite wear using intra-oral scanner

This study evaluates the wear resistance of dental paste-like bulk-fill composites compared to conventional paste-like composite resins using an intraoral scanner and 3-D analyzing software. Six different dental composite materials, including five bulk-fill composites and one conventional composite, were tested alongside natural human enamel as a control group. A computer-controlled chewing simulator for wear testing. A one-way ANOVA test was used to identify any significant differences between the means of the tested dental composite materials α=0.05. The results showed variability among bulk-fill composites, with some demonstrating wear resistance similar to conventional composites (p<0.05). Human enamel displayed the lowest wear values, but some bulk-fill composites matched this resistance(p>0.05). Significant variability was observed among bulk-fill composites but the results were comparable to those of conventional composites. The enamel control group demonstrated the lowest wear values, with some bulk-fill composites showing similar wear resistance. This study provides valuable information about the wear resistance of contemporary bulk-fill composite materials, commonly used in current clinical practice, contributing to enhancing clinical procedures.

Preheating and "snow-plow" composite application technique affect double bond conversion but not bond strength to dentine

OBJECTIVE

To measure degree of conversion (DC) of a flowable composite, microtensile bond strength (MTBS) to dentine in the snow-plow technique with/without preheating and temperature in the preheated composite.

MATERIALS AND METHODS

For DC, snow-plow specimens of Filtek Ultimate Flowable (Flow) and Filtek Bulk Fill (Bulk) (3M) were prepared by light-curing composites simultaneously in standardized molds while in control groups light-curing was separate. DC of Flow was measured using micro-Raman spectroscopy. For MTBS, specimens were prepared on dentine of human extracted molars by simultaneous (snow-plow) or separate (control) light-curing. MTBS was measured using a universal testing machine after 24 h and 6 months. Data were analyzed using ANOVA with Tukey's post hoc (α = 0.05).

RESULTS

Increased curing time significantly increased DC in snow-plow from 13.4% ± 11.6% (10 s) to 31.8% ± 4.4% (40 s) albeit significantly lower than controls (p < 0.05). Preheated Bulk improved conversion in snow-plow (44.3% ± 1.7%) and control (50.5% ± 2.6%) (p < 0.05). No significant differences occurred in MTBS between groups (p > 0.05). MTBS values ranged between 66.7 ± 8.4 MPa (snow-plow group_21°C_baseline) and 54.1 ± 15.8 MPa (control_21°C_long-term). Temperature in the preheated Bulk dropped to ~38°C after 30 s.

CONCLUSIONS

Snow-plow technique, irrespective of preheating, resulted in lower DC of Flow than separate light-curing of composite increments. Snow-plow, irrespective of preheating, resulted in similar initial and long-term MTBS to dentine.

CLINICAL SIGNIFICANCE

Clinicians with preference for flowable composite liners in Class II restorations should be aware that the snow-plow technique of simultaneous light-curing of flowable and bulk-fill composite increments affects monomer-to-polymer conversion, albeit no effect on immediate, and long-term bonding to dentine was detected. Preheating sculptable bulk-fill composite improves conversion of the flowable liner in the snow-plow technique but has no detectable effect on bond strength to dentine.

Short curing time bulk fill composite systems: volumetric shrinkage, degree of conversion and Vickers hardness

This study aimed to evaluate volumetric polymerization shrinkage, degree of conversion and Vickers hardness of four bulk-fill resin composites light-activated with their dedicated light curing units (LCUs). Four groups were evaluated, according to the type of composite and curing mode: Tetric EvoCeram Bulk-fill (TEBO) and Tetric EvoFlow Bulk-fill (TEBF) were light-activated with Bluephase Style 20i (20s, in high-mode), while Tetric Powerfill (TEPO) and Tetric Powerflow (TEPF) were light-activated with Bluephase PowerCure (3s). Volumetric polymerization shrinkage test (n = 6) was performed in standardized box-shaped class-I cavities of extracted third molars (4 x 4 x 4 mm). Teeth were scanned before and after resin composite application by micro-computed tomography, and acquired data were evaluated with Amira software. Degree of conversion (n = 5) was evaluated at the top and bottom surfaces of composite cylindric samples (4 mm diameter, 4 mm thickness) using an FT-IR spectrometer (spectra between 1,500 and 1,800 cm-1, 40 scans at a resolution of 4 cm-1). Three Vickers indentations (50 g / 15 s), spaced 500 μm apart, were performed on the top and bottom composite surfaces and averaged. One-way ANOVA was used for data evaluation. TEPF showed the lowest volumetric polymerization shrinkage (p < 0.05), while the other composites were not significantly different within each other (p > 0.05). All materials presented a significant decrease in degree of conversion and Vickers hardness when compared top to bottom surfaces (p < 0.05). Bottom to top surface ratios for degree of conversion ranged from 0.8 (TEBO and TEPO) to 0.9 (TEBF and TEPF), and from 0.4 (TEPO) to 0.7 (TEBF and TEPF) for hardness. In conclusion, resinous materials present a decrease in hardness and degree of conversion from top to bottom even when a higher power is used, while the flowable material TEPF showed the lowest volumetric shrinkage values compared to the other materials.

Clinical evaluation of posterior restorations over wet and dry dentin using an etch-and-rinse adhesive: A 36-month randomized clinical trial

OBJECTIVES

To evaluate the clinical performance of posterior restorations over wet and dry dentin with an etch-and-rinse adhesive after 36 months of clinical service.

METHODS

Forty-five participants were recruited, each one had at least two posterior teeth that needed restoration. Ninety restorations were placed on Class I or Class II cavities. For the restoration protocol, a simplified etch-and-rinse adhesive (Adper Single Bond 2) was applied over wet (WD) or dry dentin (DD) and later restored with a bulk-fill composite (Filtek Bulk Fill) under rubber dam isolation. Each restoration was evaluated using the World Dental Federation (FDI) criteria after 6, 12, and 36 months of clinical service, regarding the following principal restoration characteristics: postoperative sensitivity, marginal discoloration, marginal adaptation, fracture of material and retention, and recurrence of caries. Kruskal Wallis analysis of variance rank (α = 0.05) and Kaplan-Meier survival analysis were used for statistical analysis.

RESULTS

After 36 months of clinical evaluation, no significant difference between groups was observed in each FDI criterion (p > 0.05). Twenty restorations (WD=10, DD=10) showed minor marginal staining, and twenty-two restorations (WD=11, DD=11) presented small marginal adaptation defects (p > 0.05). Four restorations were lost (WD = 2, DD = 2) and the fracture rates (95% confidence interval) were 94.9% for each one, without significant difference between wet and dry dentin (p > 0.05).

SIGNIFICANCE

The degree of dentin moisture does not seem to affect the clinical performance of a simplified etch-and-rinse adhesive in posterior restorations when the adhesive is applied vigorously over the dentine surface.

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

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Does the universal adhesive's film thickness affect dentin-bonding effectiveness?

OBJECTIVES

To investigate the influence of adhesive resin application modalities on the film thickness of the adhesive resin and the effectiveness of a two-step universal adhesive (UA) bonded in self-etch (SE) bonding mode to high C-factor class-I cavity-bottom dentin.

MATERIALS AND METHODS

After application of the primer of G2-Bond Universal (G2B, GC), the adhesive resin was applied into standard class-I cavities (human molars) following four application modalities: (1) one layer, strongly air-blown; (2) one layer, gently air-blown; (3) two layers, each gently air-blown; (4) one layer, not air-blown. After being restored with composite, each tooth was sectioned to obtain one micro-specimen (n = 10), of which the adhesive resin film thickness was measured using optical microscopy. The micro-tensile bond strength (μTBS) was tested immediately or upon 100,000 thermocycles. Statistical analyses involved Kruskal-Wallis and Mann-Whitney U testing (p < 0.05).

RESULTS

G2B's μTBS was significantly affected by the adhesive resin application modality and aging. Gently air-blowing the adhesive resin resulted in significantly higher immediate μTBS than strong air-blowing or no air-blowing. No significant difference in μTBS was found between single or double gently air-blown adhesive resin applications. The adhesive resin film thickness significantly varied with the application modalities.

CONCLUSIONS

A too thin or too thick adhesive resin film thickness adversely affected bond strength of the two-step UA applied in SE mode and high C-factor condition.

CLINICAL RELEVANCE

The adhesive resin layer thickness can affect the bonding performance of two-step UAs in high C-factor cavities. Dental clinicians remain advised to avoid improper air-blowing of UAs and strictly follow the application instructions.

In Vitro Microleakage and Fracture Resistance of "Infinity Edge" and Cusp Reduction Preparation Designs for Moderate-sized Class II Composites

AIM

This study aimed to evaluate the marginal microleakage and maximum occlusal fracture loads and fracture modes of two novel class II preparation designs, "infinity edge" and the "2.5 mm cusp reduction" preparations as compared to a traditional class II preparation without cuspal involvement.

MATERIALS AND METHODS

Thirty extracted human mandibular molars were prepared for moderate-sized class II restorations with extensions into all occlusal grooves. Of these, ten class II preparations served as control. Ten were modified for a 2.5 mm even reduction of the cusps adjacent to the interproximal box. An additional 10 preparations were modified with an "infinity edge" bevel on the interproximal and occlusal portions. All teeth were restored utilizing a flowable bulk-fill composite in the apical portion of the interproximal box and 2-4 mm of heated bulk-fill composite in one increment for the remainder. All groups were cyclic loaded and thermocycled, then imaged with microcomputed tomography (µCT) before and after infiltration with a silver nitrate solution. Images were subtracted to obtain volumetric measurements of microleakage and reported as a percentage of the total volume from the apical extent of the proximal box. All groups were loaded to failure and fracture load and mode were recorded.

RESULTS

No significant differences were found in microleakage volume as a percentage of total tooth volume; however, the "infinity edge" group had significantly greater microleakage in the proximal box compared to the traditional class II group. No significant differences were found in fracture load or mode between the groups.

CONCLUSION

Traditional class II, 2.5 mm cuspal reduction, and "infinity edge" preparation designs have similar fracture loads as well as volumes of microleakage; however, an "infinity edge" preparation has a higher ratio of microleakage in the proximal box.

CLINICAL SIGNIFICANCE

Clinicians should carefully consider the use of "infinity edge" margins, particularly on dentin in the apical extent of the proximal box. How to cite this article: Watson JC, Lien W, Raimondi JC, et al. In Vitro Microleakage and Fracture Resistance of "Infinity Edge" and Cusp Reduction Preparation Designs for Moderate-sized Class II Composites. J Contemp Dent Pract 2024;25(1):3-9.

Fatigue and marginal adaptation of bulk fill restoratives: Effect of the layering technique and cavity dimension of extensively damaged teeth

OBJECTIVES

To evaluate the effect of layering technique and cavity dimension on the fatigue behavior and marginal adaptation of bulk fill (BF) restorations in extensively damaged teeth.

METHODS

Seventy-two premolars received class II cavities (MOD) followed by endodontic treatment. Half sample had 1/3 of their palatal cusp removed. Teeth were restored using three techniques: (I) incremental, with conventional resin composite (RC); (C) combined, using BF flow and RC, (B) bulk fill, with regular BF. Specimens were subjected to fatigue (80 N, 2 Hz, 37° C water) for 1 million cycles (n = 12). The test was interrupted every 250,000 cycles to evaluate tooth integrity, restoration fracture and adaptation using FDI criteria. Images of the proximal surfaces were obtained before and after the cycling to measure the gap. Restoration fatigue survival and success were analyzed using Weibull distribution and Maximum Likelihood Estimation. Gap thickness was analyzed with Kruskal-Wallis and Student-Newman-Keuls tests (α = 0.05).

RESULTS

For the survival analysis, Weibull modulus (β) and characteristic lifetime (η) were similar among groups. Yet, for the success analysis, in which only restorations that were free of technical complications were ranked as success, the bulk-fill technique resulted in higher β, while the combined technique produced restorations with higher η, for teeth that had their cusp removed. C-technique also resulted in smaller gaps than I and B.

SIGNIFICANCE

The effect of the layering technique on the success of restorations was dependent on the cavity extension. The combined technique favors the adaptation and the longevity of extensively damaged teeth.

Procedure time and filling quality for bulk-fill base and conventional incremental composite techniques-A randomised controlled in vitro trial

OBJECTIVES

The aims of this randomised controlled laboratory trial were to determine the procedure time and immediate quality (surface porosity and marginal gaps) of fillings placed using the bulk-fill base technique and the conventional incremental technique in simulated clinical settings.

METHODS

Forty-two dentists and dental students were randomly allocated to use either the bulk-fill base technique or the conventional incremental technique to fill an identical class II disto-occlusal cavity in a maxillary left first molar typodont tooth. We recorded the time the participants used to fill the cavity and evaluated the surface porosity and marginal gaps on the approximal surfaces of the fillings using a stereomicroscope and specific probes according to the FDI criteria for restoration evaluation. Data were analysed using the Mann-Whitney U, Kruskal-Wallis, and chi-square tests.

RESULTS

The median time ± interquartile range was 186 ± 80 s for the bulk-fill base technique and 463 ± 156 s for the conventional incremental technique (p < 0.001). The quality of the fillings was better for the bulk-fill base technique than for the conventional incremental technique (X2 = 9.5, p = 0.002). Neither operator experience nor the usual technique of choice were associated with the procedure time or the quality of the fillings.

CONCLUSIONS

Compared to the conventional incremental technique, the use of the bulk-fill base technique shortened the time to fill a cavity by 59.8 % or 4 min and 36 s, and it improved the immediate surface and marginal quality of the fillings, regardless of the operator's experience or technique preference.

CLINICAL SIGNIFICANCE

The use of the bulk-fill base technique instead of the conventional incremental technique leads to significant time-savings when placing large class II composite fillings. Additionally, the use of the bulk-fill base technique instead of the conventional incremental technique improves the immediate quality of large class II composite fillings.

Examining the Impact of Preheating on the Fracture Toughness and Microhardness of Composite Resin: A Systematic Review

The objective of this comprehensive study was to systematically evaluate the effects of preheating on two critical mechanical properties, microhardness and fracture toughness, in resin composite materials. The overarching goal was to provide valuable insights into the potential benefits and limitations of this technique for enhancing the overall mechanical performance of such materials. To achieve this, an extensive and systematic electronic search was conducted across multiple reputable databases, including MEDLINE/PubMed, SCOPUS, ProQuest, SpringerLink, Web of Science, ScienceDirect, and Google Scholar, with data collection extending until June 2023. This rigorous search process resulted in the identification of 29 pertinent articles, which were subjected to a thorough risk of bias assessment employing the Quality Assessment Tool For In Vitro Studies (QUIN). The findings of this comprehensive investigation revealed several noteworthy trends. First, concerning microhardness, all the studies consistently demonstrated a positive effect of preheating on this mechanical property. This uniformity in results corroborates the initial hypothesis that preheating indeed enhances microhardness in resin composite materials. Second, with respect to fracture toughness, a majority of the studies provided evidence supporting the notion that preheating has a favorable influence on this particular mechanical property. This alignment of outcomes suggests that preheating can be a beneficial technique for improving fracture toughness in resin composites. However, it is essential to note that there were a few exceptions within the collected data, where preheating appeared to lead to a decrease in fracture toughness. Additionally, one study reported no statistically significant effect on fracture toughness. These deviations from the general trend highlight the complexity of the relationship between preheating and fracture toughness, indicating that other factors or material-specific nuances may come into play. In conclusion, the results of this study indicate that preheating resin composites can improve microhardness and fracture toughness, offering potential benefits for dental restorations. Yet, conflicting data warrants further research to uncover the reasons behind these discrepancies. Future studies should also investigate preheating's broader impact on composite resin materials to gain a comprehensive understanding of its applications and limitations in the field.

Marginal Adaptation of In Vitro Class II Restorations Made Out of Bulk or Conventional Composite Using Single- or Multi-Layered Techniques

Objective: Testing the influence of various restorative materials (conventional or bulkfill composites) and filling techniques (single- or multi-layered techniques) on the in vitro marginal adaptation of large class II direct composites with supra and sub-gingival margins subjected to thermomechanical loading (TML). Methods: A total of 40 prepared teeth were attributed randomly to five experimental groups. In Group 1, restorations were made of multi-layered high-viscosity conventional composite (Tetric EvoCeram); in Groups 2 and 3, restorations were made of a high viscosity bulkfill composite (Tetric EvoCeram Bulk Fill) applied in one (Group 2) or three layers (Group 3); in Groups 4 and 5, restorations were made of a flowable bulkfill composite (SDR flow) applied in one (Group 4) or two layers (Group 5), covered with a layer of high-viscosity conventional composite (Ceram-X Universal). A single adhesive (OptiBond FL) was used in all groups. All specimens were submitted to a staged TML comprising three phases (2 × 500,000 and 1,000,000 cycles) at 50 N with 3350 thermal cycles (5 to 55 °C) every 500,000 cycles. The tooth-restoration interfaces on proximal surfaces were evaluated quantitatively by scanning electron microscopy, before and after each TML phase, hence at three timepoints (T0, T1, T2 and T3). The following segments were considered for evaluation: proximal, vertical enamel margins (assessed individually on both restoration sides), cervical enamel (restoration side above CEJ) and cervical dentin margin (restoration side below the CEJ). Results: TML induced a significant reduction in continuous adaptation at both enamel and dentin margins in all groups, with percentages of continuous margins ranging from 75.2 to 91.8% at T0, and decreasing to values ranging from 21.3 to 73.9% at T3. Both composite systems and layering protocols had a significant influence on marginal adaptation of the restorations, with statistical associations depending on the restoration group and the timepoint considered. Defective margins in enamel were all of a cohesive nature with micro-fractures, while in dentin, interfacial gaps were the main defect observed. Conclusions/Clinical significance: The present results highlighted significant degradation of marginal adaption after long-term in vitro fatigue test using materials even with high-viscosity conventional resin composites, applied with a proper layering approach in medium-large sub-gingival cavities. While no significant differences were observed at the dentin cervical margins, there was a tendency for better adaptation at the enamel margin when using a higher modulus material with a multi-layered technique.

The clinical performance of bulk-fill versus the incremental layered application of direct resin composite restorations: a systematic review

OBJECTIVES

To systematically review the scientific evidence comparing the clinical effectiveness of bulk-fill versus incrementally layered conventional resin composites and to evaluate if one method offers clear merits with specific clinical outcomes.

MATERIALS AND METHODS

Using relevant mesh terms and pre-established eligibility criteria in PubMed, Embase, Scopus and Web of Science, a thorough scientific search was conducted with an end-date of 30.04.2023. Randomized controlled clinical trials that involved the direct comparison of Class I and Class II resin composite restorations applied using incremental layering techniques versus bulk-filled in permanent teeth with an observation period of at least six months were considered. To evaluate the bias risk of the finalized records, a revised version of the Cochrane risk-of-bias tool for randomized trials was implemented.

RESULTS

Out of the 1445 records determined, 18 eligible reports were chosen for qualitative analysis. Data obtained was categorized as per, the cavity design, the intervention, the comparator(s), the methods of success/failure assessment, the outcomes, and follow-up. Two studies demonstrated an overall low-risk of bias, fourteen studies raised some concerns, and two studies exhibited high-risk.

CONCLUSION

Bulk filled resin composite restorations demonstrated clinical outcomes similar to those of incrementally layered resin composite restorations within a review interval of 6 months to 10 years.

Physical Properties and Clinical Performance of Short Fiber Reinforced Resin-based Composite in Posterior Dentition: Systematic Review and Meta-analysis

OBJECTIVE

This study compares the physical properties and clinical performance of short fiber reinforced composites (SFRC) to those of particulate-filled resin-based composites (PFRC) for class I and II direct restorations in permanent dentition.

METHODS

Systematic review and meta-analysis was conducted using PubMed, Embase (Elsevier), and Dentistry and Oral Sciences Source (EBSCO) databases. The outcomes evaluated were physical properties including flexural strength, flexural modulus, elastic modulus, microhardness, shrinkage, fracture toughness, degree of conversion, and depth of cure. Clinical performance was evaluated with a systematic review.

RESULTS

The meta-analyses favored SFRC for flexural strength and fracture toughness compared to every PFRC subgroup, with a high quality of evidence. For all other properties, the meta-analyses favored SFRC to overall PFRC, with some non-significant differences with certain PFRC subgroups. The most recent clinical trial showed SFRC performed similarly to PFRC, however older studies suggest inferior surface texture and discoloration of SFRC compared to PFRC.

CONCLUSION

This study can aid dental professionals in clinical decision making, supporting that SFRC offers improved physical properties, especially fracture resistance and flexural strength, compared to PFRC.

Bulk-Fill Resins versus Conventional Resins: An Umbrella Review

Currently, composite resins have become the material of choice for the restoration of posterior teeth. Although bulk-fill resins represent a tempting alternative due to their lower complexity and faster use, some dentists are reluctant to use this material. The objective is to compare the performance of bulk-fill resins and conventional resins in direct restorations of posterior teeth based on the literature. The databases that were used to carry out the research were PubMed/MEDLINE, Embase, the Cochrane Library and the WOS. This umbrella literature review complies with PRISMA standards and assesses the quality of studies using the AMSTAR 2 tool. With the application of the criteria of the AMSTAR 2 tool, the reviews were considered low to moderate. The overall meta-analysis, although without statistical significance, favours mostly the use of conventional resin, as it is about five times more likely to obtain a favourable result than bulk-fill resin. Bulk-fill resins result in a simplification of the clinical process of posterior direct restorations, which is an advantage. The performance in terms of several properties of bulk-fill resins and conventional resins showed that they present similar behaviour.

Assessment of Microhardness of Conventional and Bulk-Fill Resin Composites Using Different Light-Curing Intensity

(1) Background: This study evaluates the effect of a conventional/low-voltage light-curing protocol (LV protocol) (10 s with 1340 mW/cm²) and high-voltage light-curing protocol (HV protocol) (3 s with 3440 mW/cm²) on the microhardness (MH) of dental resin-based composites (RBCs). Five resin composites were tested: conventional Evetric (EVT), Tetric Prime (TP), Tetric Evo Flow (TEF), bulk-fill Tetric Power Fill (PFL), and Tetric Power Flow (PFW). (2) Materials and Methods: Two tested composites (PFW and PFL) were designed for high-intensity light curing. The samples were made in the laboratory in specially designed cylindrical molds; diameter = 6 mm and height = 2 or 4 mm, depending on the type of composite. Initial MH was measured on the top and bottom surfaces of composite specimens 24 h after light curing using a digital microhardness tester (QNESS 60 M EVO, ATM Qness GmbH, Mammelzen, Germany). The correlation between the filler content (wt%, vol%) and the MH of the RBCs was tested. For the calculation of depth-dependent curing effectiveness, the bottom/top ratio for initial MH was used. (3) Conclusions: MH of RBCs is more dependent on material composition than on light-curing protocol. Filler wt% has a greater influence on MH values compared to filler vol%. The bottom/top ratio showed values over 80% for bulk composites, while for conventional sculptable composites, borderline or suboptimal values were measured for both curing protocols.

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 (VS_depth) decreased. For conventional RBCs, there was a significant drop in VS_depth 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, VS_depth 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.

Conditional Mitigation of Dental-Composite Material-Induced Cytotoxicity by Increasing the Cure Time

Light-cured composite resins are widely used in dental restorations to fill cavities and fabricate temporary crowns. After curing, the residual monomer is a known to be cytotoxic, but increasing the curing time should improve biocompatibility. However, a biologically optimized cure time has not been determined through systematic experimentation. The objective of this study was to examine the behavior and function of human gingival fibroblasts cultured with flowable and bulk-fill composites cured for different periods of time, while considering the physical location of the cells with regard to the materials. Biological effects were separately evaluated for cells in direct contact with, and in close proximity to, the two composite materials. Curing time varied from the recommended 20 s to 40, 60, and 80 s. Pre-cured, milled-acrylic resin was used as a control. No cell survived and attached to or around the flowable composite, regardless of curing time. Some cells survived and attached close to (but not on) the bulk-fill composite, with survival increasing with a longer curing time, albeit to <20% of the numbers growing on milled acrylic even after 80 s of curing. A few cells (<5% of milled acrylic) survived and attached around the flowable composite after removal of the surface layer, but attachment was not cure-time dependent. Removing the surface layer increased cell survival and attachment around the bulk-fill composite after a 20-s cure, but survival was reduced after an 80-s cure. Dental-composite materials are lethal to contacting fibroblasts, regardless of curing time. However, longer curing times mitigated material cytotoxicity exclusively for bulk-fill composites when the cells were not in direct contact. Removing the surface layer slightly improved biocompatibility for cells in proximity to the materials, but not in proportion to cure time. In conclusion, mitigating the cytotoxicity of composite materials by increasing cure time is conditional on the physical location of cells, the type of material, and the finish of the surface layer. This study provides valuable information for clinical decision making and novel insights into the polymerization behavior of composite materials.

The influence of different placement techniques on the clinical success of bulk-fill resin composites placed in Class II cavities: a 4-year randomized controlled clinical study

OBJECTIVE

The purpose of this double-blind and split-mouth randomized controlled clinical trial was to evaluate the clinical success of the placement technique (bulk-filling and incremental techniques) of a bulk-fill resin composite in Class II carious lesions.

MATERIALS AND METHODS

Two different bulk-fill resin composites, X-tra fil (Voco) and Filtek Bulk Fill (3M ESPE), were used in the bulk-filling and incremental techniques for 20 patients. The study was carried out in 4 groups, with 20 restorations in each group. Restorations were appraised at baseline, 6-month, 2-year, and 4-year recall. World Dental Federation (FDI) and the US Public Health Service (USPHS) criteria were used in the evaluations. The Friedman, Kruskal-Wallis, and Mann-Whitney U tests were used for the statistical analysis.

RESULTS

At the end of year 4, there was no loss of restoration in any group. According to the USPHS and FDI criteria, there was a difference in the baseline and 4-year in marginal adaptation and marginal discoloration of the restorations (P < 0.05). When Filtek-Bulk was placed as an incremental technique, there was a minor fracture in four restorations (P > 0.05). In addition, Filtek-Bulk showed a color change according to the results based on both the USPHS and FDI criteria (P < 0.05). The difference between the two placement techniques of each resin composite was not significant at the year 4 recall when all criteria were evaluated (P ˃ 0.05).

CONCLUSIONS

The 4-year clinical success of the evaluated bulk-fill composites is not dependent on the placement technique used.

CLINICAL RELEVANCE

This study can help clinicians choose which technique (bulk fill and incremental techniques) bulk-fill composites can be used.

TRIAL REGISTRATION

US National Library of Medicine, www.

CLINICALTRIALS

gov , ID: NCT04565860 Registered on 10/09/2020. Clinical Evaluation of Bulk-fill resin Composites in Class II Restorations.

Cytotoxicity and reactive oxygen species production induced by different co-monomer eluted from nanohybrid dental composites

BACKGROUND

Safety issues for dental restorative composites are critical to material selection, but, limited information is available to dental practitioners. This study aimed to compare the chemical and biological characteristics of three nanohybrid dental composites by assessing filler particle analysis, monomer degree of conversion (DC), the composition of eluates, and cytotoxicity and reactive oxygen species (ROS) production in fibroblasts.

METHODS

Three nanohybrid composites (TN, Tetric N-Ceram; CX, Ceram X Sphere Tec One; and DN, DenFil NX) were used. The size distribution and morphology of the filler particles were analysed using scanning electron microscopy (n = 5). The DC was measured via micro-Raman spectroscopy (n = 5). For the component analysis, methanol eluates from the light-polymerised composites were evaluated by gas chromatography/mass spectrometry (n = 3). The eluates were prepared from the polymerised composites after 24 h in a cell culture medium. A live/dead assay (n = 9) and Water-Soluble Tetrazolium-1 assay (n = 9) were performed and compared with negative and positive controls. The ROS in composites were compared with NC. Statistical significance in differences was assessed using a t-test and ANOVA (α = 0.05).

RESULTS

Morphological variations in different-sized fillers were observed in the composites. The DC values were not significantly different among the composites. The amounts of 2-hydroxyethyl methacrylate (HEMA) were higher in TN than DN (p = 0.0022) and triethylene glycol dimethacrylate (TEGDMA) in CX was higher than in others (p < 0.0001). The lowest cell viability was shown in CX (p < 0.0001) and the highest ROS formation was detected in TN (p < 0.0001).

CONCLUSIONS

Three nanohybrid dental composites exhibited various compositions of filler sizes and resin components, resulting in different levels of cytotoxicity and ROS production. Chemical compositions of dental composites can be considered with their biological impact on safety issues in the intraoral use of dental restorative composites. CX with the highest TEGDMA showed the highest cytotoxicity induced by ROS accumulation. DN with lower TEGDMA and HEMA presented the highest cell viability.

Micro-computed tomography assesment of structural microporosity and marginal gaps in different flowable composites placed with different instruments

Objectives: The aim of this study was to evaluate the structural microporosity (MP) and marginal gap (MG) of different flowable composite resins placed with different instruments using micro-computed tomography (μCT). Materials and Methods: Standard Class II MOD cavities were prepared on 108 lower third molar teeth. Three different flowable composite resins; Filtek Bulk-fill, SDR Bulk-fill and I-Flow conventional flowable composite resin were applied to the cavities using a sharp explorer, a microbrush or an injector. After they were covered with a paste-like nanohybrid composite resin, μCT images were examined in terms of MP and MG. Statistical analysis of the data was performed using two-way ANOVA and Tukey’s post hoc tests. Results: MP was observed less in explorer group than microbrush and injector groups (p < 0.05). There was no significant difference between microbrush and injector groups (p > 0.05). i-FLOW flowable composite resin showed the highest MP rate compared to the other two groups (p < 0.05). There was no significant difference between SDR and Filtek Bulk-fill in MP (p > 0.05). In terms of MG, i-FLOW presented higher MG values than other two materials (p < 0.05), while the instruments showed similar results (p > 0.05). Conclusions: Additional occluso-gingivally vibration of flowable materials with an explorer may be useful in the placement. Bulk-fill composite resins are better than conventional flowable composite resin in terms of MP and MG.

Damping Behaviour and Mechanical Properties of Restorative Materials for Primary Teeth

The energy dissipation capacity and damping ability of restorative materials used to restore deciduous teeth were assessed compared to common mechanical properties. Mechanical properties (flexural strength, modulus of elasticity, modulus of toughness) for Compoglass F, Dyract eXtra, SDR flow, Tetric Evo Ceram, Tetric Evo Ceram Bulk Fill, and Venus Diamond were determined using a 4-point bending test. Vickers hardness and Martens hardness, together with its plastic index (η_ITdis), were recorded using instrumented indentation testing. Leeb hardness (HLD) and its deduced energy dissipation data (HLD_dis) were likewise determined. The reliability of materials was assessed using Weibull analysis. For common mechanical properties, Venus Diamond always exhibited the significantly highest results and SDR flow the lowest, except for flexural strength. Independently determined damping parameters (modulus of toughness, HLD_dis, η_ITdis) invariably disclosed the highest values for SDR flow. Composite materials, including SDR flow, showed markedly higher reliabilities (Weibull modulus) than Compoglass F and Dyract eXtra. SDR flow showed pronounced energy dissipation and damping characteristics, making it the most promising material for a biomimetic restoration of viscoelastic dentin structures in deciduous teeth. Future developments in composite technology should implement improved resin structures that facilitate damping effects in artificial restorative materials.

One-year clinical evaluation of class II bulk-fill restorations in primary molars: a randomized clinical trial

This double-blind, randomized clinical trial aimed to compare the clinical performance and clinical time to restore occluso-proximal cavities in primary molars withbulk-fillresin and conventional resin. A total of 140 class II restorations in primary molars of 65 participants (mean age of 6.7 + 1.5) were placed in two random groups:bulk-filland conventional resin. The restorations were evaluated using FDI criteria at the baseline, 6-month, and one year by a single calibrated examiner, and the clinical restorative time was measured with a digital timer. The success and survival of the restorations were evaluated with Kaplan-Meier graphs. The log-rank test compared the curves. Differences in restorative clinical time were compared using the Mann-Whitney U test. The level of significance was 5%. After one year, 115 restorations were evaluated. The success probability was 88.7% for Filtek Z350 XT and 85.9% for FiltekTM Bulk-fill, and for the survival probability, Filtek Z350 XT presented 90%, and FiltekTM Bulk-fill presented 93.7%. No significant difference was found between the success and survival curves (p=0.62), (p=0.51). The main reason for failure was marginal adaptation.Bulk-fillresin required 30% less time than the conventional resin (p<0.001).Bulk-fillresin presented similar clinical performance to the conventional resin and required less restorative clinical time. It is an option to restore class II lesions of primary molars.

Resin-Based Composites for Direct and Indirect Restorations: Clinical Applications, Recent Advances, and Future Trends

Continuous advancements in resin-based composites can make selection of the appropriate system a daunting task for the clinician. This review aims to simplify this process and clarify some new or controversial topics. Various types of composites for direct and indirect applications are discussed, including microfilled and microhybrid composites, nanocomposites, single shade, bulk fill, fiber-reinforced, high temperature/high pressure processed, CAD/CAM, and three-dimensional printable composites. Recent material advancements that lead to improved seal and toughness, degradation resistance, antimicrobial and self-healing capabilities are presented. Future directions are highlighted, such as the development of "smart" materials that are able to interact with the host environment.

Bulk-fill restorative composites under simulated carious and erosive conditions

Acidic conditions can cause hydrolysis and accelerate degradation of resin composites (RCs). Since there are limited and controversial data on the effect of acids on bulk-fill RCs, this study assessed the surface roughness (SR) and flexural strength (FS) of these RCs under simulated carious and erosion conditions. Bars of Filtek Bulk Fill (FBF, 3M/ESPE), X-tra fil (XTF, Voco), Tetric N-Ceram Bulk Fill (TBF, Ivoclar/Vivadent), and Aura Bulk Fill (ABF, SDI) and a conventional RC [Filtek Z350XT (FZ, 3M/ESPE)] were allocated (n=15) to undergo caries or erosion conditions. The control group was kept in artificial saliva (AS). The bars were evaluated for SR change (final-baseline) and for three-point FS. Data were analyzed using ANOVA and Tukey's test. At the baseline (p <0.001), the SR of RCs ranked as follows: (TBF = XTF) < FBF (none differed from FZ) < ABF. The interplay between RCs and conditions affected SR change (p = 0.025). While after storage in AS, there was no difference among RCs, following carious and erosive conditions, ABF showed higher SR change. For FS (p <0.001), XTF > (FBF = FZ) > (TBF = FZ) > ABF, with no difference among control, carious and erosive conditions (p = 0.148). Depending on the restorative bulk-fill RCs, carious and erosive conditions roughen the surface but do not affect the FS of these materials.

The stamp technique for direct restoration in a ICDAS 4 carious lesion: A 4-year follow-up

OBJECTIVE

This case report described the use of a stamping technique associated with a bulk fill composite to restore an ICDAS 4 carious lesion on a posterior tooth. The 4-year follow-up is also presented.

CLINICAL CONSIDERATIONS

A 32-year-old patient presented a carious lesion on tooth 36 with an underlying dark shadow at the dentin seen from the noncavitated enamel occlusal surface, which was compatible with an ICDAS 4 carious lesion. The lesion was radiographically detected and the caries disease was treated with dietary and hygiene habits orientations. Before accessing the lesion and selectively removing the carious tissue, an occlusal stamp was made by applying a flowable resin composite to copy the anatomy of the noncavitated enamel surface. The cavity was restored using a bulk fill resin composite (Opus Bulk Fill, FGM) with 4-mm-thick increments. Before curing the last increment, a Teflon band was adapted at the uncured bulk fill composite surface and the occlusal stamp made with the flowable composite was pressed against it to reproduce the natural characteristics and initial occlusal anatomy. The top surface was light-activated for 40 s. After 4 years, small wear could be seen in the restoration, but still within clinically acceptable levels.

CONCLUSION

The occlusal stamp technique allows reproduction of the natural anatomy of teeth affected by ICDAS 4 carious lesions with good clinical longevity over 4 years.

CLINICAL SIGNIFICANCE

This case report presents the use of the stamp technique to restore a tooth affected by an ICDAS 4 lesion, in which a carious process reached the dentin and the enamel anatomy was still preserved. The bulk fill resin composite associated with the occlusal stamp was chosen to quickly restore the cavity with clinical predictability. Bulk fill composites allow the insertion of up to 4-mm-thick increments and offer lower shrinkage stress, good clinical longevity and a less time-consuming procedure in cases of posterior teeth, especially if associated with the stamp technique.

Comparison of polymerization shrinkage of a new bulk-fill flowable composite with other composites: An in vitro study

OBJECTIVE

Since composites still face a critical problem called polymerization shrinkage and bulk-fill composites have reported acceptable results for this issue, this study aims to assess the polymerization shrinkage of a new bulk-fill flowable composite (G-aenial bulk injectable [GBI]) and compare it to other bulk-fill and conventional composites.

MATERIALS AND METHODS

In this in vitro study, 25 composite discs were fabricated using three bulk-fill and two conventional composites. They were bonded to a microscopic slide and were covered by a coverslip. This assembly was transferred to a linear variable differential transformer and composite samples were cured from underneath the slides. Dimensional changes formed in composite samples were recorded. Data were analyzed using analysis of variance followed by post hoc Tukey's and Dunnett's tests.

RESULTS

The groups were significantly different regarding polymerization shrinkage. G-aenial bulk injectable and G-aenial universal flo showed significantly higher polymerization shrinkage than other composites at 30, 60, and 1800 s after light irradiation, while X-tra fil and Filtek Z250 showed the lowest polymerization shrinkage at the aforementioned time points.

CONCLUSION

According to the results, the new composite had polymerization shrinkage similar to the conventional one. Bulk-fill composites reported similar or lower shrinkage to conventional composites.

A Systematic Review and Meta-Analysis of the Success of Resin Composite Restorations

Aim:

This review examines the studies on resin composites within the past decade and evaluates the materials’ application methods and success through Fédération Dentaire Internationale (FDI) scores.

Materials and Methods:

Search results from three databases (a total of 3295 studies) were transferred to Mendeley Desktop (Mendeley, London, UK) software and deduplicated (2638 studies). Eight studies were included in this meta-analysis after scanning the title, abstract, and full-text screening. Risk of bias analysis was performed using the Cochrane Handbook tool. Shapiro–Wilk, Kolmogorov–Smirnov, Kruskal–Wallis, and post hoc Tamhane’s T2 were used for statistical analysis.

Results:

Conventional composite’s surface staining FDI score was higher than flowable and silorane composites (no difference between these two). Also, conventional composite has the highest score in terms of staining. Conventional composite + two-step self-etch adhesive and bulk fill composite + two-step self-etch adhesive have lower FDI scores in marginal staining. In noncarious cervical lesions (NCCL), conventional composite + two-step total-etch adhesive has a higher score than flowable composite + two-step self-etch adhesive. Flowable composite + two-step self-etch adhesive and conventional composite + single-step self-etch adhesive have the highest FDI scores for marginal adaptation (no statistical difference between them). Conventional composite + two-step self-etch adhesive and bulk fill composite + two-step self-etch have the lowest scores (no statistical difference between them). For recurrence of caries, all groups have Score 1, the best score, and there is no significant difference between them.

Conclusions:

Each restorative material and adhesive system has different advantages, and the practitioner must choose the most appropriate.

Polymerization Kinetics and Development of Polymerization Shrinkage Stress in Rapid High-Intensity Light-Curing

This study investigated polymerization kinetics, linear shrinkage, and shrinkage stress development for six contemporary composite materials of different viscosities cured using radiant exitances of 1100–2850 mW/cm². Real-time measurements of degree of conversion, linear shrinkage, and shrinkage stress were performed over 5 min using Fourier-transform infrared spectrometry, a custom-made linometer, and a custom-made stress analyzer, respectively. For most tested variables, the factor “material” had a higher effect size than the factor “curing protocol”. Maximum polymerization rate and maximum shrinkage stress rate were the most affected by changes in curing conditions. In contrast, no significant effects of curing conditions were identified within each material for shrinkage stress values measured at the end of the 5 min observation period. Linear shrinkage and shrinkage stress values measured after 5 min were closely correlated (R = 0.905–0.982). The analysis of polymerization kinetics suggested that the two composites specifically designed for rapid light-curing responded to higher radiant exitances differently than other composites. Polymerization kinetics and shrinkage stress behavior of contemporary restorative composite materials of different viscosities were overall more affected by material type than differences in curing conditions. Subtle differences in polymerization kinetics behavior shown by the two composites specifically designed for rapid high-intensity light-curing did not translate into significant differences in the development of polymerization shrinkage stress.

Comparative Evaluation of Bulk-Fill Composite Resins: Knoop Microhardness, Diametral Tensile Strength and Degree of Conversion

Purpose

Bulk-fill composite resins were developed to reduce time and facilitate the restorative procedure. However, considering their recent introduction on the market and the new formulations, their performance still requires evaluation. This study aimed to evaluate Knoop microhardness (KHN), diametral tensile strength (DTS) and degree of conversion (DC) of three Bulk-Fill composite resins and a conventional one.

Materials and Methods

Sixty samples (n = 15; 8 mm ø x 4 mm height) were confectioned using a mold. Filtek Bulk-Fill (FBF), Tetric N-Ceram Bulk-Fill (TNC) and SonicFill 2 (SF2) were placed in 4 mm increments, and Filtek Z350 (FZ350) was placed in 2 mm increments. The KHN of top and bottom surfaces were tested using Knoop Hardness tester at 10 gf/10s. The DTS was tested under compressive load at 1.0 mm/min. The DC was measured by Fourier Transform Infrared (FTIR) spectroscopy. Differences in DTS and DC were analyzed by ANOVA and Tukey post hoc test. For KHN, Kruskal-Wallis and Wilcoxon tests were performed at α = 0.05.

Results

Top surfaces of all composite resins had higher KHN than bottom surfaces. At top and bottom surfaces, FZ350 showed higher KHN than TNC and SF2. The highest DTS was obtained by FBF, followed by FZ350 and SF2. The highest DC was obtained by SF2, the lowest one was obtained by FBF.

Conclusion

From Bulk-Fill composite resins, FBF presented the best KHN and DTS results. The SF2 showed the best DC. Further studies are required to ensure whether these differences can negatively influence the behavior of in vivo restorations.

Influence of the self-adhering strategy on microhardness, sorption, solubility, color stability, and cytotoxicity compared to bulk-fill and conventional resin composites

OBJECTIVES

To analyze and compare, in vitro, the microhardness, sorption, solubility, color stability, and cytotoxicity of three types of resin composites: self-adhesive (SARC) (Dyad Flow (DF)/Kerr), bulk-fill (Filtek Bulk Fill Flow (FBF)/3 M ESPE), and conventional (Filtek Z350XT Flow (Z350)/3 M ESPE).

MATERIALS AND METHODS

Thirty cylindrical specimens were prepared using a split metal mold (15 mm × 1 mm), divided into 3 groups (n = 10) according to the material used. Vickers hardness (VH) was calculated from three indentations (300gf/15 s) per specimen. The sorption and solubility were measured according to the ISO 4049:2009 specification after storing in distilled water for 7 days. The color of each resin composite was measured using a portable digital spectrophotometer according to the CIELAB system. After a 7-day immersion in coffee, the color variation (∆E) was calculated. Following the ISO 10993:2012, the cytotoxicity in Vero cells was evaluated through the MTT assay. The results were analyzed using the Kruskal-Wallis test to compare the studied groups. The Wilcoxon test was used to compare the assessments in each studied group. For cytotoxicity analysis, the data were compared by the ANOVA test (α = 0.05).

RESULTS

DF showed the lowest VH (28.67), highest sorption (0.543 µg/mm³) and solubility (1.700 µg/mm³), and higher ∆E after 7 days of coffee immersion (p = 0.008). The resin composites studied were considered non-cytotoxic.

CONCLUSIONS

The SARC presented inferior mechanical and physical-chemical properties than bulk-fill and conventional resin composites, with comparable cytotoxicity against Vero cells.

CLINICAL RELEVANCE

The simplification of the clinical protocol of SARC can minimize the number of possible failures during the restorative technique. However, considering their inferior physical and mechanical properties, their coverage with materials of higher mechanical properties and physical-chemical stability should be considered.

Influence of Practitioner-Related Placement Variables on the Compressive Properties of Bulk-Fill Composite Resins-An In Vitro Clinical Simulation Study

Aims: To determine if restoration location and/or execution behavior force parameters have an influence on the mechanical properties of bulk-fill composite dental restorations. Methods: Pressure transducers were placed within each quadrant of dental mannequin jaws. Cylindrical molds were placed above the transducers and filled with two bulk-fill composite materials, Filtek and Tetric, by four experienced dentists. Each dentist prepared five specimens per quadrant and material. The total placement time, mean force, number of peak forces (above 25 N), and mean peak(s) force during placement were measured. Then, the stiffness and maximal compressive strength of the specimens were determined while loading the specimens up to failure using a universal loading machine. Results: Placement time was affected by jaw (p < 0.004) and side (p < 0.029), with the shortest time demonstrated for the left side of the mandible. Force exerted during restoration placement was not normally distributed without differences in location (jaw) or material. A higher application force was found on the right side (p < 0.01). The number of peak forces was affected by side (p < 0.03), with less peaks on the left side. No significant differences were found in compressive strength when correlated to restoration location, participant, or material (p = 0.431). The stiffness values of Filtek (3729 ± 228 N/mm) were found to be 15% higher than Tetric (3248 ± 227 N/mm) (p < 0.005). No correlations were found between the compressive strength or stiffness and the amount of force applied during placement. Conclusions: The individual restoration material placement parameters did influence practitioner performance; however, these differences did not affect the mechanical properties of the final restoration.

The Effect of Two Different Light-Curing Units and Curing Times on Bulk-Fill Restorative Materials

This study aimed to evaluate the effect of two different light-curing units and curing times on the surface microhardness (SMH), compressive strength (CS), and volumetric shrinkage (VS) of four restorative materials (FiltekTM Z250, FiltekTM Bulk Fill Posterior, Beautifil® Bulk Restorative, ACTIVATM BioACTIVE). For all tests, each material was divided into two groups depending on the curing unit (Woodpecker LED-E and CarboLED), and each curing unit group was further divided into two subgroups according to curing time (10 s and 20 s). SMH was evaluated using a Vickers hardness tester, CS was tested using a universal testing machine, and VS was measured using video imaging. In all the restorative materials cured with Woodpecker LED-E, the 20 s subgroup demonstrated significantly higher SMH values than the 10 s subgroup. In both light-curing time subgroups, the CarboLED group showed significantly higher CS values than the Woodpecker LED-E group for all restorative materials except FiltekTM Bulk Fill Posterior cured for 20 s. ACTIVATM BioACTIVE showed significantly greater volumetric change than the other restorative materials. A higher curing light intensity and longer curing time had a positive effect on the SMH and CS of the restorative materials tested in this study. On the other hand, curing unit and time did not show a significant effect on the VS values of restorative materials.

Determination of microhardness of bulk-fill resins at different depths

The aim of this study was to determine Vickers microhardness (HV) in bulk fill resins at different depths. Test specimens were prepared with different bulk fill resins: Filtek Bulk-Fill (3M ESPE) [FBF], Surefill SDR flow (Dentsply) [SDR], Fill-UP (COLTENE) [FU] and Surefill (Dentsply) [SF]. Semi-cylindrical test specimens were prepared in a mold 6 mm in diameter and 4 mm thick (n=5). A 1000 mW/cm2 light curing unit was applied (Coltolux LED - Coltene) for 20 seconds. HV was determined with three indentations (Vickers Future Tech FM300, 300 g, 8 s) at four depths: 1, 2, 3 and 4 mm from the top surface to the interior. Data were recorded immediately (t0) and 24 hours later (t24). Results were analyzed with two-way ANOVA (p<0.05), and multiple comparisons were performed using Tukey's test. Mean and SD of HV at t0 for each mm were: [FBF] t0: 49.23(4.65) / 48.32(3.36) / 44.38(2.06) / 40.59(2.58); [FBF] t24: 61.37(3.47) / 62.63(3.03) / 57.27(5.22) / 56.37(5.88);[SDR]t0:27.81(3.13) / 28.07(2.4) / 27.24(2.94) / 25.71(3.0); [SDR] t24: 35.11(2.16) / 35.17(1.96) / 35.53(1.81) / 33.18(2.08); [FU] t0: 41.43(1.41) / 39.87(0.88) / 38.11(1.81) / 39.09(1.92); [FU] t24: 49.27(1.54) / 48.77(1.77) / 48.65(1.88) / 46.76(4.93); [SF] t0: 71.35(7.09) / 67.39(9.76) / 68.95(6.21) / 64.1(8.35); [SF] t24: 76.06(6.61) / 75.31(9.37) / 75.2(11.57) / 69.81(12.14). ANOVA showed significant effect of material, depth and recording time (p<0.05), and Tukey's test showed that recording sites (depths) differed significantly, giving four homogeneous groups. Under the conditions of this study, it can be concluded that microhardness of bulk-fill resins can be affected by depth and post-curing time.

Influence of Matrix Type on Marginal Gap Formation of Deep Class II Bulk-Fill Composite Restorations

Background: To test the hypothesis that transparent matrices result in more continuous margins of bulk-fill composite (BFC) restorations than metal matrices. Methods: Forty standardized MOD cavities in human molars with cervical margins in enamel and dentin were created and randomly assigned to four restorative treatment protocols: conventional nanohybrid composite (NANO) restoration (Tetric EvoCeram, Ivoclar Vivadent, Schaan, Liechtenstein) with a metal matrix (NANO-METAL) versus transparent matrix (NANO-TRANS), and bulk-fill composite restoration (Tetric EvoCeram Bulk Fill, Ivoclar Vivadent, Schaan, Liechtenstein) with a metal matrix (BFC-METAL) versus transparent matrix (BFC-TRANS). After artificial aging (2500 thermal cycles), marginal quality was evaluated by scanning electron microscopy using the replica technique. Statistical analyses were performed using the Mann−Whitney U-test and Wilcoxon test. The level of significance was p < 0.05. Results: Metal matrices yielded significantly (p = 0.0011) more continuous margins (46.211%) than transparent matrices (27.073%). Differences in continuous margins between NANO (34.482%) and BFC (38.802%) were not significant (p = 0.56). Matrix type did not influence marginal gap formation in BFC (p = 0.27) but did in NANO restorations (p = 0.001). Conclusion: Metal matrices positively influence the marginal quality of class II composite restorations, especially in deep cavity areas. The bulk-fill composite seems to be less sensitive to the influence of factors such as light polymerization and matrix type.

Bond strength of bulk-fill resin composites

 Aim: Evaluating the resin-dentin bond strength of Class II conventional and bulk-fill composite restorations, using different cavity sizes before and after aging. Methods: Seventy-five human molars were distributed into groups according to the buccolingual width of the cavities, conservative (n=25) and extended (n=50). They were divided according to the restorative material: conventional (Z100/control group) or bulk-fill resin composites (Filtek Bulk Fill/FBF; Tetric N Ceram Bulk Fill/TNCBF; Filtek Bulk Fill Flow/FBFF; Surefill SDR flow/SDR). The restored teeth were sectioned on sticks (n=50 per restorative materials + width cavities group), half were stored in Water/Ethanol 75% for 30 days and the other half were submitted to the immediate microtensile bond strength (μTBS) test. Data were analyzed applying the Three-Way Analysis of Variance (ANOVA), Bonferroni test, test t, and Weibull analyses (p<0.05). Results: SDR and FBF presented lower μTBS values for extended preparation when compared to the conservative preparation, before aging. After aging, only for the FBFF, a decrease in the μTBS values was observed. Comparing the μTBS values, before and after aging, the SDR demonstrated lower μTBS values after aging when the conservative cavity was used. A decrease in the μTBS values was observed for the Z100, the FBF and, the FBFF, after aging, when the extended cavity was used. Conclusion: The effect of cavity preparation and aging on the resin-dentin of Class II is material dependent. Most of the bulk-fill resin composites evaluated presented a similar performance to the conventional resin composites for all the conditions of this study.

Direct and semi-direct resin composite restoration in large cavity preparations: analysis of dentin bond strength stability and bottom/top microhardness ratio in a cavity model

To evaluate the influence of the restorative approach and aging time on dentin bond strength (BS), failure mode (FM), and bottom/top microhardness ratio (B/T) in a large dentin cavity model. A total of 102 bovine incisors were used to produce models of conical dentin cavities (4.0 mm thickness × 4.8 mm top diameter × 2.8 mm bottom diameter), which were restored using semi-direct filling (SDF) (Filtek™ Z250 XT + Scotchbond™ Universal/RelyX™ Ultimate luting system), direct bulk filling (DBF) (Filtek™ One Bulk Fill), and direct incremental filling (DIF) (Filtek™ Z250 XT) techniques. B/T, BS, and FM (n = 17) were analyzed in a microhardness tester, a universal testing machine, and a stereomicroscope, respectively, after 24 h and 6 months of water storage. BS and B/T data were analyzed using two-way ANOVA/Tukey post-hoc test (p < 0.05), while FM data were analyzed descriptively. There was a statistically significant difference in BS between the restorative techniques, and BS was influenced by aging time in the DBF and SDF groups. Mixed failure was predominant for the SDF technique in both aging times. There was no statistically significant difference in B/T among the restorative approaches regardless of the aging time (p > 0.05). Although all restorative approaches provided similar B/T, the semi-direct technique showed better performance on the material bond strength to dentine in large cavities.