CRITICAL APPRAISAL

Bulk-fill Composites, Part I Author and Associate Editor EDWARD J. SWIFT, JR., DMD, MS*

The Journal of Esthetic and Restorative Dentistry published a Critical Appraisal of bulk-fill flowable composite resins by Dr. Ricardo Walter in early 2013 (JERD 2013;25(1):72–6). Since then, new bulk-fill composite options have become available and have rapidly achieved great popularity.This two-part Critical Appraisal reviews some of the more recent information on the various bulk-fill options.

Bulk-fill Resin-based Composites: An In Vitro Assessment of Their Mechanical Performance N. ILIE, S. BUCUTA, M. DRAENERT Operative Dentistry 2013 (38:618–25)

ABSTRACT Objective: To assess the mechanical properties of bulk-fill composites, comparing their performance with a previously published database of other contemporary composites under identical conditions. Materials and Methods: Seven bulk-fill composites were evaluated in this study: Filtek Bulk Fill (3M ESPE, St. Paul, MN, USA), SonicFill (Kerr Corporation, Orange, CA, USA), SureFil SDR flow (Dentsply Caulk, Milford, DE, USA), Tetric EvoCeram Bulk Fill (Ivoclar Vivadent, Schaan, Liechtenstein), Venus Bulk Fill (Heraeus Kulzer, Hanau, Germany), x-tra base (VOCO GmbH, Cuxhaven, Germany), and x-tra fil (VOCO). Four of these materials (Filtek Bulk Fill, SureFil SDR Flow, x-tra base, and Venus Bulk Fill) require a capping layer of a standard composite, but the others are used to fill entire preparations. Twenty specimens of each material were made in 2 × 2 × 16 mm steel molds. The composite was light activated from both top and bottom using 20-second exposures with an LED curing device with an intensity of 1200 mW/cm2. After

grinding to remove any protruding edges or bulges, the specimens were stored in distilled water for 24 hours. They were subjected to a three-point bending test to determine flexural strength and flexural modulus. Fragments of the materials from the three-point bending test that were larger than 8 mm were used to determine the top-surface microhardness and indentation modulus of each material. The structural appearance of the filler particles (size and morphology) was examined using field emission scanning electron microscopy. Results: As a group, the bulk-fill materials had a lower filler load than microhybrid and nanohybrid composites. They had a higher filler load by weight than regular flowable composites, but a similar filler volume. On average, the filler content of the bulk fill materials was 73.1% by weight and 51.0% by volume, more similar to flowable composites than to microhybrid or nanohybrid composites. Filler volume and weight had strong influences on differences in mechanical properties of the various bulk-fill composites. Mean flexural strength values ranged from 120.8 MPa for

*Professor, Department of Operative Dentistry and Interim Associate Dean for Education, University of North Carolina School of Dentistry, Chapel Hill, NC, USA

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DOI 10.1111/jerd.12162

© 2015 Wiley Periodicals, Inc.

CRITICAL APPRAISAL Swift

Tetric EvoCeram Bulk Fill to 142.8 MPa for Sonic Fill. The statistical analysis placed the materials into two groups based on their Weibull modulus, an indicator of reliability. x-tra base, SureFil SDR, and Venus Bulk Fill had very high Weibull moduli and the rest of the materials had moderate Weibull moduli. Filtek Bulk Fill and Venus Bulk Fill had the lowest elastic moduli (i.e., were the least stiff materials). These two materials and SureFil SDR had the lowest microhardness. Conclusions: The measured mechanical properties of bulk-fill materials fall between those of regular and flowable composites, indicating a similar or possibly inferior clinical behavior of these materials relative to standard microhybrid or nanohybrid composites. However, there are wide differences in mechanical properties within the bulk-fill category. The results of this study verify manufacturer instructions for some materials to be capped with a regular composite

because these materials have low indentation moduli and hardness.

COMMENTARY The authors noted that the bulk-fill materials are more translucent than other composites, and that some of the translucency was achieved by decreasing the filler content and increasing the filler size. For example, they found that SureFil SDR contained some particles larger than 20 μm. As mentioned, the authors also stated that a “capping layer” of regular composite should be applied over some bulk-fill composites because they have some inferior mechanical properties. Of course, this is precisely what the manufacturers are recommending for products such as SureFil SDR or x-tra base. However, this recommendation does not apply to every case, with SonicFill being one example of a bulk-fill material intended to restore the entire preparation.

Post-cure Depth of Cure of Bulk Fill Dental Resin-composites A. ALRAHLAH, N. SILIKAS, D.C. WATTS Dental Materials 2014 (30:149–54)

VHN at 80% of maximum VHN, and depth at 80% of maximum VHN.

ABSTRACT Objective: To determine the post-cure depth of cure of bulk-fill composites by measuring Vickers hardness profiles (VHN). Materials and Methods: Five bulk-fill composites were evaluated in this study: Filtek Bulk Fill, SonicFill, Tetric EvoCeram Bulk Fill, Venus Bulk Fill, and x-tra base. Specimens of each material were made in stainless steel molds containing slots with dimensions of 15 × 4 × 2 mm. The composite was cured from the top using an LED device with a measured intensity of 1200 mW/cm2. After 24 hours in dry storage, the Vickers hardness of each specimen was measured at 0.3-mm intervals using a microhardness tester. The statistical analysis was used to determine significant differences between materials for maximum VHN,

© 2015 Wiley Periodicals, Inc.

DOI 10.1111/jerd.12162

Results: Maximum VHN values ranged from 37.8 for Venus Bulk Fill to 77.4 for SonicFill. Depths at 80% of maximum VHN were in a very tight range, from 4.14 mm for Filtek Bulk Fill to 5.03 mm for SonicFill. Conclusion: Bulk-fill composites can be cured to an acceptable depth as claimed by their manufacturers.

COMMENTARY Some methods for measuring composite depth of cure, such as the standard scraping test, might actually overestimate the depth of cure. As an alternative, hardness testing can provide an accurate estimate of cure depth. Composite material is typically considered

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to be well polymerized if its hardness is at least 80% of top surface hardness, which is why the authors used the 80% level in this study. Differences in hardness between

materials are related primarily to their filler content. Of the materials tested, Venus Bulk Fill has the lowest filler content and SonicFill the highest.

Effect of Bulk/Incremental Fill on Internal Gap Formation of Bulk-fill Composites A. FURNESS, M.Y. TADROS, S.W. LOONEY, F.A. RUEGGEBERG Journal of Dentistry 2014 (42:439–49)

ABSTRACT Objective: To examine the potential for maintaining gap-free interfacial bonds in Class I preparations restored using a variety of bulk-fill composite materials. Materials and Methods: The cuspal areas of 40 extracted molars were flattened to provide a level occlusal surface in which a standardized Class I preparation was made. The preparations were 4 mm in diameter and 4 mm deep, with all margins in enamel. A conventional composite (Filtek Supreme, 3M ESPE) was used as the control and was placed and light activated both in bulk and in 2-mm increments. In the experimental groups, the preparations were restored either in bulk or in 2-mm increments using SureFil SDR flow, Quixx (Dentsply Caulk), SonicFill, or Tetric EvoCeram Bulk Fill. In every case, the total light exposure time was the same for bulk or incremental filling. For example, when Filtek Supreme was placed in bulk, it was light activated for 40 seconds. When it was placed incrementally, each 2-mm increment was activated for 20 seconds. Each composite material was used in conjunction with a curing light and an etch-and-rinse adhesive from the respective manufacturer (e.g., SmartLite iQ2 and Prime & Bond NT for both SureFil SDR Flow and Quixx). Any excess composite was removed using a finishing diamond to expose the cavosurface margins and the specimens were then thermocycled between 5°C and 55°C 1000 times. The specimens were sectioned and stained with a caries disclosing solution (Sable Seek, Ultradent Products, South Jordan, UT, USA). High-resolution digital images were made and evaluated by calibrated examiners using image analysis software. The examiners evaluated gaps at three specific locations

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along the interface of composite and tooth structure – at the enamel, mid-dentin, and pulpal floor. At each location, the portion of the gap-free length (identified by absence of stain) was measured as a percentage of the total interfacial length. Results: For the primary outcome variable of interest – bulk vs. incremental placement – the proportion of gap-free interfaces was not significantly different. Differences between specific materials also were generally not significant. The proportion of gap-free interfaces tended to decrease with increasing depth in the preparation, but was largely unaffected by composite type or placement technique. Conclusion: Use of a bulk-fill composite restorative materials resulted in similar proportion of gap-free tooth-restoration interfaces as the use of a conventional composite.

COMMENTARY The materials evaluated in this study represented the three different types of bulk-fill composites that are currently available – low-viscosity (SureFil SDR Flow), higher viscosity (Quixx and Tetric EvoCeram Bulk Fill), and variable viscosity (SonicFill). It provides some positive news about the adaptation of these materials to preparations when used according to manufacturer directions. However, the study was confusing in some respects, especially because it generated a large amount of data with very few significant differences worthy of note. Also, it suffers from two potentially significant confounding factors. Each composite was used with a curing light and adhesive system from its own

DOI 10.1111/jerd.12162

© 2015 Wiley Periodicals, Inc.

CRITICAL APPRAISAL Swift

manufacturer – as opposed to using the same curing light and adhesive with every composite. Therefore, any gap formation could have been related not only to the

placement method and properties of the composite itself, but also to the intensity of the curing light or the efficacy of the adhesive.

Marginal Adaptation of Class II Cavities Restored with Bulk-fill Composites E.A. CAMPOS, S. ARDU, D. LEFEVER, E.F. JASSÉ, T. BARTOLOTTO, I. KREJCI Journal of Dentistry 2014 (42:571–81)

ABSTRACT Objective: To determine the marginal adaptation of contemporary bulk-fill composites in two-surface Class II preparations with beveled enamel margins. Materials and Methods: Large MO preparations (5 mm wide, 4 mm deep pulpally, and gingival margin 1 mm apical to the CEJ (cementoenamel junction)) were made in 40 extracted human molars. All enamel cavosurface margins were beveled using a fine diamond. Specimens were randomly assigned to five groups based on the filling technique. The same etch-and-rinse adhesive system (OptiBond FL, Kerr Corporation) was used in all groups. All preparations were restored in two increments (4 mm and 2 mm thick), light activating each increment for 40 seconds at 1100 mW/cm2. The experimental groups (first and second increments) were Venus Bulk Fill/Venus Diamond, Tetric EvoCeram Bulk Fill/Tetric EvoCeram, SonicFill/SonicFill (Kerr), and SureFil SDR Flow/Ceram-X (Dentsply DeTrey, Konstanz, Germany). A two-increment restoration of Ceram-X only was used as the control. Occlusal margins of the restorations were finished using fine diamonds and the proximal margins were finished using flexible discs (Sof-Lex, 3M ESPE). Impressions of the specimens were made using a vinyl polysiloxane material and were cast in epoxy resin. A new set of epoxy replicas was obtained following extensive thermomechanical loading of the specimens. Restoration margins before and after loading were examined with a scanning electron microscope at 200× magnification. Marginal adaptation results were expressed as percentage of continuous (gap-free) margin overall and at occlusal, proximal, and cervical locations.

© 2015 Wiley Periodicals, Inc.

DOI 10.1111/jerd.12162

Results: Overall, both before and after thermomechanical loading, the Venus group had a lower percentage of continuous margin than any of the other groups, all of which were similar to the control. Loading reduced the proportion of continuous margins in all groups at all three locations. As one example, SonicFill had an 78.1% continuous margin along the proximal enamel margins, and this decreased to 56.2% after loading. Marginal adaptation was generally, but not always worst at the cervical dentin margin. Conclusion: Bulk-fill composites exhibit adequate marginal adaptation similar to that of a standard composite.

COMMENTARY The authors’ conclusion actually states that “bulk-fill materials do not allow better marginal adaptation than a standard composite.” This is an odd way of summarizing the study’s results, because better marginal adaptation would not necessarily be expected. In the reviewer’s opinion, similar marginal adaptation obtained more quickly is the desired outcome of a bulk-fill composite. It is worth noting that all of the materials tested in this study were used with an incremental filling technique. This is the recommended method for some of the materials tested (e.g., SureFil SDR) but not necessarily so for others (e.g., SonicFill). The authors likely chose to use two increments for all because their preparation depth (6 mm in the proximal box) exceeded the curing depths typically claimed by manufacturers of the bulk-fill materials.

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Critical Appraisal: Bulk-fill Composites, Part I.

The Journal of Esthetic and Restorative Dentistry published a Critical Appraisal of bulk-fill flowable composite resins by Dr. Ricardo Walter in early...
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