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en: Effects of pre-polymerization temperature on the mechanical properties and viscosity of light-cure flowable composite resins for core build-up.

en: This study evaluated the effects of pre-polymerization temperature on the mechanical properties and viscosity of light-cure flowable composite resins for core build-up. Four materials (EverX Flow, BeautiCore LC Injectable, Filtek Fill and Core Flowable Restorative Plus, and iTFC Luminous Core LC Flow) were conditioned at 4, 23, or 60°C. Flexural strength, elastic modulus, fracture toughness, and viscosity were measured. Temperature significantly affected viscosity and, in BeautiCore, Filtek, and iTFC, also influenced flexural strength and fracture toughness. The short fiber-reinforced composite EverX Flow showed superior mechanical performance with consistent temperature stability, while BeautiCore and Filtek demonstrated improved flowability after pre-heating. iTFC exhibited a low modulus and minimal temperature sensitivity. These results indicate that temperature is a critical factor in the clinical performance of flowable composites, with pre-heating enhancing handling through viscosity reduction.

en: Dental Materials Journal

ja: Dental Materials Journal


en: Trueness and precision of composite injection technique: Roles of index design, composite flowabilities, and impression workflow.

en: This study evaluates the dimensional accuracy (trueness and precision) of direct composite veneer restorations fabricated using a composite injection technique by investigating the effects of clear index designs, composite flowabilities, impression modality used for master model fabrication. An in vitro 3 × 3 × 2 factorial design (N = 90; n = 5 per group) is used to assess three index configurations (monolayer-closed, MC; monolayer-open, MO; and bilayer-open, BO), three composite flowabilities (super-low, low, and high), and two impression modalities (conventional and digital). All specimens are digitized and superimposed onto a reference model to quantify trueness and precision using a root-mean square analysis. Data are analyzed using a generalized linear model (α = 0.05). Trueness is significantly affected by index design and impression technique (p < 0.05), and the BO index and digital impressions achieve the highest dimensional accuracy. The digital-BO combination yields a 48.1% improvement over the least accurate workflow. Precision is significantly affected by all three factors (p < 0.05). Conversely, conventional impression demonstrates superior overall precision (p < 0.001) driven by a significant three-way interaction (p < 0.001) in which the digital- and conventional-MO-high groups show poorest repeatability (111.1 µm) and highest precision (38.8 µm), respectively. Thus, index design and impression techniques are primary factors affecting dimensional accuracy. The rigid BO index consistently enhances both trueness and precision; digital impressions optimize trueness, and conventional impressions show superior precision. Clinicians should prioritize rigid bilayer indices to achieve predictable veneer accuracy.

en: Journal of Dentistry

ja: Journal of Dentistry


en: Urethane Tetramethacrylate Monomers and Nano-Fillers Enhance Dentin Bond Strength of a One-Step Universal Adhesive

en: This study evaluated the effects of incorporating urethane tetramethacrylate (UTMA) monomers and inorganic nano-fillers on the bonding performance and mechanical properties of a next-generation one-step universal adhesive, Clearfil Universal Bond Quick 2 (UBQ2), with a focus on clarifying its improvements over the previous formulation. Five adhesive systems were investigated: UBQ2, two experimental variants lacking either UTMA (UBQ2-U) or nano-fillers (UBQ2-F), the predecessor adhesive (Clearfil Universal Bond Quick, UBQ), and a gold-standard two-step self-etch adhesive (Clearfil SE Bond 2, SE2). Microtensile bond strength (μTBS), bond layer thickness (L), ultimate tensile strength (UTS), and water sorption (Wsp) were evaluated. UBQ2 demonstrated significantly higher UTS and lower Wsp than UBQ2-U (P 0.001 and P = 0.03, respectively), indicating enhanced mechanical resilience and hydrolytic stability due to the presence of UTMA. Compared to UBQ, UBQ2 showed improved mechanical properties while maintaining comparable μTBS. The absence of nano-fillers (UBQ2-F) significantly reduced μTBS (P 0.05), confirming their critical role in bonding performance. Despite forming a thinner adhesive layer, UBQ2 achieved dentin bond strength comparable to SE2. By combining UTMA and nano-fillers, UBQ2 has improved wettability compared to conventional products, while also providing high bonding performance and mechanical properties with a one-step application. These findings support the development of universal adhesives through simplified clinical protocols and improved material properties. This study demonstrates that incorporating nano-fillers and UTMA into a one-step universal adhesive (UBQ2) enhances mechanical strength, reduces water sorption, and maintains high dentin bond strength. Clinically, UBQ2 offers a simplified yet reliable bonding performance comparable to SE2.

en: The Journal of Adhesive Dentistry

ja: The Journal of Adhesive Dentistry


en: Sub-micrometer chemical imaging of dental adhesive/dentin interfaces via mid-infrared photothermal microscopy

en: Optics Communications

ja: Optics Communications


en: The effect of HEMA and 10-MDP in the bonding agent of a two-step self-etch system on water sorption, elastic modulus, and microtensile bond strength to dentin

en: This study evaluated the effects of HEMA and 10-MDP in the bonding agent in a 2-step self-etch adhesive system, Clearfil SE Bond 2, on water sorption (W) and elastic modulus (E) of the polymerized bonding agent. The microtensile bond strength (µTBS) to dentin was also evaluated initially and after 10,000 thermal cycles (TC10,000). Four bonding agents were tested: the original, H-free (excluding HEMA), M-free (excluding 10-MDP), and HM-free (excluding HEMA and 10-MDP). HEMA increased W and decreased E. Initial µTBS (TC0) was highest for the original and lowest for HM-free. After TC10,000, the original maintained the highest µTBS, indicating the importance of HEMA and 10-MDP. TC10,000 did not reduce µTBS for any groups. HEMA and 10-MDP compromised mechanical property and increased water sorption, suggesting these components could potentially compromise adhesive stability.


ja: Sub-micrometer chemical imaging of dental adhesive/dentin interfaces via mid-infrared photothermal microscopy


en: A Digitally Enhanced Transparent Silicone Index for the Direct Composite Resin Injection Technique in Premolar Replacement: A Case Report

en:
 Purpose: This case report describes the restoration of a missing lower second premolar using a direct resin-bonded fixed partial denture (RBFPD), employing the composite resin injection technique with a digital workflow and a transparent silicone index. While conventional direct composite RBFPD can be technique-sensitive, this approach simplifies and standardizes the process, making it less dependent on the operator's experience.

 Methods: A 50-year-old male patient sought restoration of a missing lower second premolar, preferring to avoid cutting intact teeth or surgical interventions such as dental implants. Thus, a direct composite RBFPD was chosen. The restoration was digitally designed, and a transparent silicone index was fabricated from a 3D-printed dental model, which featured mesial and distal, narrow bucco-lingual extensions to prevent overflow of the composite resin. After the adjacent abutment teeth were bonded with a two-step self-etching adhesive, a highly filled universal-shade flowable composite resin was injected through the opening of the occlusal surface of the silicone index.

 Results: The procedure proved to be straightforward, with the success of treatment being less dependent on clinical technique sensitivity. In the laboratory, the need for conventional free-hand wax-up with paraffin wax was eliminated in favor of digital wax-up. The design resulted in less overflow of the flowable composite resin in the cervical area, enhancing cleanability with interdental brushes. A functional and esthetic replacement of the missing premolar was achieved without tooth preparation.

 Conclusion: This technique provides a minimally invasive and cost-effective solution with predictable clinical outcomes, establishing it as a potential definitive restorative option.

en: Operative Dentistry, Endodontology and Periodontology


en: Effects of powder-to-liquid ratio on properties of β-tricalcium-phosphate cements modified using high-energy ball-milling

en: The authors have developed a β-tricalcium-phosphate (β-TCP) powder modified mechano-chemically through the application of a ball-milling process (mβ-TCP). The resulting powder can be used in a calcium-phosphate-cement (CPC). In this study, the effects of the powder-to-liquid ratio (P/L ratio) on the properties of the CPCs were investigated, and an appropriate P/L ratio that would simultaneously improve injectability and strength was clarified. The mβ-TCP cement mixed at a P/L ratio of 2.5 and set in air exhibited sufficient injectability until 20 min after mixing, and strength similar to or higher than that mixed at a P/L ratio of 2.0 and 2.78. Although the mβ-TCP cements set in vivo and in SBF were found to exhibit a lower strength than those set in air, it did have an appropriate setting time and strength for clinical applications. In conclusion, P/L ratio optimization successfully improved the strength of injectable mβ-TCP cement.


en: Effects of high-energy ball-milling on injectability and strength of β-tricalcium-phosphate cement

en: Calcium phosphate cement (CPC) offers many advantages as a bone-substitution material. The objective of this study is to develop a new CPC that simultaneously exhibits fine injectability, a short setting time, and high strength. β-tricalcium phosphate (β-TCP, control) powder was ball-milled for 24h to produce a new cement powder. The modified β-TCP after 24h milling (mβ-TCP-24h) exhibited excellent injectability even 1h after mixing. The mechanical properties of the set cement (compact) were evaluated using compressive strength (CS) and diametral tensile strength (DTS) testing. The CS and DTS values of the mβ-TCP-24h compacts were 8.02MPa and 2.62MPa, respectively, at 5h after mixing, and were 49.6MPa and 7.9MPa, respectively, at 2 weeks after mixing. All the CS and DTS values of the mβ-TCP-24h compacts were significantly higher than those of the control for the same duration after mixing. These results suggest that the mechano-chemically modified β-TCP powder dissolves rapidly and accelerates hydroxyapatite precipitation, which successfully shortens the cement setting time and enhances the strength. This study supports that mβ-TCP-24h is a promising candidate for use in injectable CPCs with improved strength.

en: Journal of the Mechanical Behavior of Biomedical Materials