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6CCVD Research

Depth of Cure, Hardness, Roughness and Filler Dimension of Bulk-Fill Flowable, Conventional Flowable and High-Strength Universal Injectable Composites - An In Vitro Study

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2022-06-07
JournalNanomaterials
AuthorsFrancesco Saverio Ludovichetti, Patrizia Lucchi, Giulia Zambon, Luca Pezzato, Rachele Bertolini
InstitutionsUniversity of Verona, University of Padua
Citations26
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study evaluated the physical and mechanical properties of five resin-based composites (RBCs)—two Bulk-Fill Flowable (BF), two Conventional Flowable (CF), and one High-Strength Universal Injectable (HSUI)—focusing on Depth of Cure (DOC), Hardness (HV), and Roughness (Ra).

  • Core Finding: Bulk-fill flowable composites demonstrated significantly superior Depth of Cure (DOC) compared to both conventional flowable and high-strength injectable materials under standard 20 s light curing (1000 mW/cm2).
  • DOC Performance: BF composites (G1, G2) achieved mean DOC values between 4.12 mm and 4.24 mm, meeting manufacturer specifications for bulk placement (4 mm).
  • Conventional Limitations: CF composites (G4, G5) showed significantly lower DOC (mean 2.58 mm to 2.84 mm), reinforcing the clinical requirement for 2 mm incremental layering.
  • Mechanical Properties: The Tetric EvoFlow Bulk Fill (G2) exhibited the highest mean Vickers Hardness (72 HV), statistically superior to the conventional flowables (G4, G5).
  • Surface Quality Trade-off: The highest roughness was observed in the Tetric EvoFlow Bulk Fill (G2, mean 2.015 ”m), while the G-ĂŠnial Flo X (G5, mean 0.130 ”m) showed the lowest roughness.
  • Material Homogeneity: No statistically significant difference in DOC was found between materials of the same type (i.e., G1 vs. G2, or G4 vs. G5).

Technical Specifications

Section titled “Technical Specifications”

The following table summarizes key material properties and experimental results for the five tested resin-based composites (RBCs).

ParameterValueUnitContext
Light Curing Irradiance1000mW/cm2VALO LED LCU
Light Curing Time20sStandardized for all materials
DOC (Bulk-Fill Flowable Range)3.91 to 4.53mmG1 (Filtek) and G2 (Tetric)
DOC (Conventional Flowable Range)2.47 to 2.90mmG4 (Filtek) and G5 (G-ĂŠnial Flo X)
DOC (Injectable Mean)3.02mmG3 (G-ĂŠnial Universal Injectable)
Filler Content (Highest)80/60wt%/vol%Tetric EvoFlow Bulk Fill (G2)
Filler Content (Lowest)64.5/42.5wt%/vol%Filtek Bulk Fill Flowable (G1)
Vickers Hardness (Highest Mean)72HVTetric EvoFlow Bulk Fill (G2)
Vickers Hardness (Lowest Mean)46HVFiltek Supreme XTE Flowable (G4)
Roughness (Highest Mean)2.015”mTetric EvoFlow Bulk Fill (G2)
Roughness (Lowest Mean)0.130”mG-Ênial Flo X (G5)
Microhardness Load10N30 s dwell time

Key Methodologies

Section titled “Key Methodologies”

The study employed standardized ISO and established material science techniques for characterization:

  1. Specimen Preparation:

    • A reusable cylindrical stainless-steel mold (4 mm diameter, 10 mm depth) was used.
    • The mold was filled, covered with Mylar strips, and excess material was pressed out.
    • 14 samples were prepared for each of the five materials (N=70 total).

  2. Light Curing Protocol:

    • A VALO LED light-curing unit (LCU) was used at 1000 mW/cm2 irradiance.
    • Curing time was standardized at 20 s, with the light tip centered and in contact with the material surface.

  3. Depth of Cure (DOC) Assessment:

    • The ISO 4049 scrape technique was applied.
    • Cured specimens were pushed out of the mold.
    • Uncured resin was gently scraped off with a plastic spatula.
    • The absolute length of the remaining cured composite was measured using a digital caliper (±0.1 mm accuracy).
    • DOC was calculated as half the absolute length (DOC = Length / 2).

  4. Roughness (Ra) Measurement:

    • A PLU-Neoxℱ 3D laser confocal microscope (Sensofar) with a 20× objective was used.
    • Measurements were taken over a 1.6 × 0.6 mm2 area.
    • Roughness was computed according to ISO 4288 (As filter 2.5 ”m, cut-off Ac 0.8 mm).

  5. Microhardness (HV) Measurement:

    • A Vickers microhardness tester (ShimadzuÂź) was used.
    • Five indentations were made per specimen.
    • Load: 10 N; Dwell Time: 30 s.
    • Hardness values (GPa) were calculated based on the average diagonal values.

  6. Filler Morphology Analysis:

    • Scanning Electron Microscope (SEM) imaging was performed (Leica Microsystems).
    • Samples were coated with a gold layer (approx. 20 nm) to ensure conductivity.
    • Images were collected at 3000× and 9000× magnification to study filler size and distribution.

Commercial Applications

Section titled “Commercial Applications”

The findings regarding the high Depth of Cure and mechanical stability of Bulk-Fill Flowable composites have direct implications for restorative dentistry, particularly in scenarios requiring simplified, time-efficient procedures.

  • Pediatric Dentistry: Bulk-fill flowables are highly advantageous for uncooperative or anxious pediatric patients, as they significantly reduce operative time by eliminating the need for multiple 2 mm incremental layers.
  • General Restorative Dentistry: Used for deep and wide posterior cavities where achieving adequate polymerization depth is critical for long-term restoration survival and reduced risk of secondary caries.
  • Material Formulation and Development: The study validates manufacturer strategies (e.g., modified photoinitiator systems like Ivocerin, increased translucency via filler size/content changes) aimed at enhancing light transmission and polymerization depth in bulk-fill materials.
  • Adhesive Restorations: Bulk-fill flowables offer an excellent combination of aesthetics, longevity, and operative simplicity, serving as dentine substitutes or bases in large restorations.
  • Quality Control and Standardization: The data provides benchmarks for DOC, hardness, and roughness, aiding manufacturers in meeting or exceeding ISO 4049 standards for new resin-based composite formulations.
View Original Abstract

(1) Objective: To evaluate and compare the depth of cure (DOC) of two bulk-fill flowable composites (Filtek Bulk Fill Flowable Restorative and Tetric EvoFlow Bulk Fill), two conventional flowable composites (Filtek Supreme XTE Flowable Restorative and G-énial Flo X) and one high-strength universal injectable composite (G-énial Universal Injectable). (2) Methods: specimens were placed in a stainless-steel mold with an orifice of 4 mm in diameter and 10 mm in depth and light-cured for 20 s using a light emitting diode (LED) light-curing unit (LCU) with an irradiance of 1000 mW/cm2; depth of cure was assessed using the ISO 4049 scrape technique, and the absolute length of the specimen of cured composite was measured in millimeters with a digital caliper. The same procedure was repeated with 14 samples for each material under investigation, for a total number of 70 test bodies. Material roughness and hardness results were also investigated using, respectively, a 3D laser confocal microscope (LEXT OLS 4100; Olympus) at ×5 magnification and a Vickers diamond indenter (Vickers microhardness tester, Shimadzu¼, Kyoto, Japan) under 10-N load and a 30 s dwell time. SEM images at 3000 and 9000 magnification were collected in order to study the materials’ filler content. Statistical analysis were performed by a commercial statistical software package (SPSS) and data were analyzed using multiple comparison Dunnett’s test. (3) Results: The average DOC of both bulk-fill composites was more than 4 mm, as a range of 3.91 and 4.53 mm with an average value of 4.24 and 4.12 mm, while that of the conventional flowable composites was much lower, as a range of 2.47 and 2.90 mm with an average value of 2.58 and 2.84 mm; DOC of the high-strength injectable composite was greater than the one of traditional composites, but not to the level of bulk-fill materials, as a range of 2.82 and 3.01 mm with an average value of 3.02 mm. Statistical analysis revealed significant differences (p-values < 0.05) in the depth of cure between bulk fill flowable composites and other composites, while there was no difference (p-values > 0.05) between the materials of the same type. (4) Conclusions: Bulk-fill flowable composites showed significantly higher depth of cure values than both traditional flowable composites and high-strength injectable composites.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2019 - Dental restorative composite materials: A review [Crossref]
  2. 2013 - Effects of two low-shrinkage composites on dental stem cells (viability, cell damaged or apoptosis and mesenchymal markers expression) [Crossref]
  3. 2006 - Curing-light attenuation in filled-resin restorative materials [Crossref]
  4. 2012 - Longevity of posterior composite restorations: Not only a matter of materials [Crossref]
  5. 2010 - Shrinkage Stresses Generated during Resin-Composite Applications: A Review
  6. 1995 - Influence of light intensity on polymerization shrinkage and integrity of restoration-cavity interface [Crossref]
  7. 2001 - Effect of liners on cusp deflection and gap formation in composite restorations
  8. 2008 - How should composite be layered to reduce shrinkage stress: Incremental or bulk filling? [Crossref]
  9. 2017 - Incremental techniques in direct composite restoration [Crossref]

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