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

Metadata	Details
Publication Date	2022-06-07
Journal	Nanomaterials
Authors	Francesco Saverio Ludovichetti, Patrizia Lucchi, Giulia Zambon, Luca Pezzato, Rachele Bertolini
Institutions	University of Padua, University of Verona
Citations	26
Analysis	Full AI Review Included

Technical Documentation & Analysis: Advanced Composite Characterization

Reference Paper: Ludovichetti et al. (2022). Depth of Cure, Hardness, Roughness and Filler Dimension of Bulk-Fill Flowable, Conventional Flowable and High-Strength Universal Injectable Composites: An In Vitro Study. Nanomaterials, 12, 1951.

Executive Summary

This documentation analyzes a study comparing the physical and mechanical properties of five dental resin-based composites (RBCs), focusing on the critical role of advanced material characterization techniques that necessitate ultra-hard, precision tooling.

Core Achievement: Bulk-fill flowable composites (G1, G2) demonstrated significantly superior Depth of Cure (DOC) values (mean 4.12-4.24 mm) compared to conventional flowable materials (mean 2.58-2.84 mm).
Mechanical Performance: Vickers Microhardness testing confirmed high mechanical stability, with the Tetric EvoFlow Bulk Fill (G2) achieving the highest average hardness of 72 GPa.
Methodological Rigor: The study relied on stringent ISO standards (ISO 4049 for DOC, ISO 4288 for Roughness) and high-precision metrology tools, including Vickers diamond indenters, optical profilers, and SEM.
Material Science Insight: SEM analysis confirmed that reduced filler percentage and increased filler size enhance translucency, facilitating deeper photopolymerization.
6CCVD Value Proposition: The precision required for Vickers indentation and high-resolution surface profiling mandates the use of high-purity, ultra-hard materials. 6CCVD specializes in providing the Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) necessary for manufacturing superior metrology tooling and wear-resistant components.
Customization: 6CCVD offers custom SCD for indenter tips and precision polished PCD substrates, ensuring reliable calibration and testing platforms for replicating or extending this research.

Technical Specifications

The following hard data points were extracted from the experimental methodology and results:

Parameter	Value	Unit	Context
Light Curing Irradiance	1000	mW/cm²	Intensity of LED LCU used for 20 s curing
DOC (Bulk-Fill Mean Range)	4.12 - 4.24	mm	Average Depth of Cure for G1 and G2 composites
DOC (Conventional Mean Range)	2.58 - 2.84	mm	Average Depth of Cure for G4 and G5 composites
Vickers Hardness (G2 Mean)	72	GPa	Highest average microhardness observed (Tetric EvoFlow)
Vickers Load	10	N	Applied load for microhardness testing
Vickers Dwell Time	30	s	Time under load during hardness measurement
Roughness Standard	ISO 4288	N/A	Standard used for surface roughness computation
Roughness Cut-off (Ac)	0.8	mm	Cut-off length for roughness profile analysis
SEM Magnification	3000, 9000	x	Magnification levels used for filler morphology study
Mold Dimensions	4 x 10	mm	Diameter x Depth of reusable stainless-steel mold

Key Methodologies

The study employed rigorous, standardized procedures for material preparation and characterization:

Specimen Preparation: Composites were placed in a reusable cylindrical stainless-steel mold (4 mm diameter, 10 mm depth) to ensure consistent geometry and volume.
Photopolymerization: Materials were light-cured for 20 s using an LED Light-Curing Unit (LCU) providing an irradiance of 1000 mW/cm², maintaining contact and centering the light tip.
Depth of Cure (DOC) Determination: DOC was assessed using the International Organization for Standardization (ISO) 4049 scrape technique. The uncured resin was gently scraped off, and the absolute length of the cured specimen was measured with a digital caliper (±0.1 mm accuracy). DOC was calculated as half the absolute length.
Surface Roughness (Ra) Measurement: A 3D laser confocal microscope (optical profiler) with a 20x objective was used. Roughness was computed according to ISO 4288, utilizing an As filter of 2.5 µm and a cut-off Ac of 0.8 mm.
Microhardness Testing: A Vickers diamond indenter was used under a 10 N load with a 30 s dwell time. Hardness values (GPa) were calculated based on the average diagonal length of the indentation.
Filler Morphology Analysis: Scanning Electron Microscope (SEM) images were collected at 3000x and 9000x magnification after coating the samples with a 20 nm gold layer to ensure conductivity.

6CCVD Solutions & Capabilities

The precise metrology and high-wear testing environment described in this research highlight the critical need for advanced diamond materials. 6CCVD is uniquely positioned to supply the necessary components for high-accuracy scientific and engineering applications.

Applicable Materials

Application Requirement	6CCVD Material Recommendation	Technical Justification
Vickers Indentation Tips	Single Crystal Diamond (SCD)	SCD provides the ultimate hardness and geometric stability required for precision indenters, ensuring accurate GPa measurements under 10 N loads.
High-Precision Molds/Tooling	Polycrystalline Diamond (PCD) Substrates	PCD offers superior wear resistance and thermal stability for reusable molds (like the 4 mm x 10 mm mold used) or high-throughput testing platforms up to 125 mm in size.
Optical Metrology Windows	Optical Grade SCD	Essential for calibration standards or protective windows in the LCU or optical profiler, offering exceptional transparency across the UV/Visible spectrum (380-500 nm curing range) and ultra-low roughness.
Electrochemical Analysis (Future Work)	Boron-Doped Diamond (BDD) Films	For extending research into real-time degree of conversion (DC) analysis via electrochemistry, BDD provides a stable, highly sensitive electrode material.

Customization Potential

6CCVD’s in-house capabilities directly address the precision and customization needs demonstrated by this study:

Precision Tooling Replication: The study utilized a custom stainless-steel mold. 6CCVD can manufacture custom diamond components (SCD or PCD) to replace or line such molds, drastically increasing longevity and reducing surface degradation, ensuring consistent testing conditions over thousands of cycles.
Dimensional Control: We offer PCD plates up to 125 mm and SCD/PCD thicknesses from 0.1 µm to 500 µm, allowing researchers to design custom testing platforms far exceeding the 4 mm diameter used in this study.
Ultra-Low Roughness Polishing: To meet the stringent requirements of ISO 4288 metrology, 6CCVD guarantees SCD polishing to Ra < 1 nm and inch-size PCD polishing to Ra < 5 nm, crucial for reliable surface texture analysis.
Custom Metalization: Should future studies require integrated sensors or heating elements on the diamond surface (e.g., for thermal stability testing), 6CCVD provides internal metalization services including Au, Pt, Pd, Ti, W, and Cu.

Engineering Support

6CCVD maintains an in-house team of PhD-level material scientists and engineers ready to assist researchers. We offer expert consultation on material selection, custom geometry design, and integration support for advanced dental and biomedical metrology projects, ensuring optimal performance for high-load Vickers testing and precision optical applications.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

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-ænial Flo X) and one high-strength universal injectable composite (G-ænial 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, Shimadzu®, 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

Original Source

DOI: https://doi.org/10.3390/nano12121951

References

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