Nakato Takagi, Yumika Ida, Tomoki Iuchi, Masaomi Ikeda, Kenichi Hamada, Kittisak Sanon, Afonso Celso Klein-Junior, Takashi Hatayama, Yasushi Shimada and Keiichi Hosaka : Effects of pre-polymerization temperature on the mechanical properties and viscosity of light-cure flowable composite resins for core build-up., Dental Materials Journal, 2026.
(要約)
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.
Fitri Diana Muslimah, Putra Adityakrisna Yoshi Wigianto, Kittisak Sanon, Kohei Kamoi, Yumika Ida, Tomoki Iuchi, Tetsuo Ichikawa and Keiichi Hosaka : Trueness and precision of composite injection technique: Roles of index design, composite flowabilities, and impression workflow., Journal of Dentistry, 2025.
(要約)
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.
Yusuke Matsuki, Yumika Ida, Tomoki Iuchi, Wakana Oki, Kazuhide Yonekura, Yuta Utsumi, Masaomi Ikeda, Lorenzo Breschi and Keiichi Hosaka : Urethane Tetramethacrylate Monomers and Nano-Fillers Enhance Dentin Bond Strength of a One-Step Universal Adhesive, The Journal of Adhesive Dentistry, 27, 287-295, 2025.
(要約)
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.
Tomoki Iuchi, Kazuhide Yonekura, Yumika Ida, Yutaro Motoyama, Masaomi Ikeda, Kenichi Hamada, Masatoshi Nakajima and Keiichi Hosaka : 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, Dental Materials Journal, 2025.
(要約)
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.