Dental Materials最新文献

Objectives: As artificial atoms, quantum dots are widely used in quantum information research since their individual energy levels may be precisely controlled using gate voltages. The purpose of the study was to modify carbon quantum dots (CQDs) and evaluate its effects on the structure, crystal orientation and mechanical properties of the enamel substrate along with antibacterial properties of CQDs.

Materials and methods: Enamel specimens of 4 mm × 4 mm × 3 mm were cut and CQD solution was dialyzed in deionized water mixed with urea solution and placed in microwave system (800 W) to obtain *CQD_0.1 %^-, **CQD_0.2 %^-, ***CQD_0.3 %^-, and *****CQD_0.5 % for enamel blocks to be immersed for 2 weeks. X-ray diffraction analysis and density-functional theory (DFT) calculations were performed to determine degree of phase purity. Transmission electron microscopy (TEM) was used for imaging of CQDs and treated enamel, with zeta potential measured with Zetasizer. Raman spectra was acquired with spectral range of 400-2000 cm^-1. Atomic force microscopy was performed with a peak force set at 200 nN. Lactobacillus biofilm was prepared on treated enamel substrates and analysed using confocal, scanning electron microscopy and TEM.

Results: DFT calculations summarised improved lattice parameters of HAp***CQD_0.3 %^- and HAp***CQD_0.5 %^-. Zeta potential is least for salineS and is maximum for *****CQD_0.5 %^- distributed system. The salineS, and *CQD_0.1 %^- groups had comparable v₁PO₄³⁻ value, indicating consistent phosphate intensities. TEM successfully verified carbon dots as spherical. Enamel crystals aligned their c-axis perpendicular to the electron beam within 1° with CQDs treated specimens exhibiting misoriented-crystals. *****CQD_0.5 %^- group had highest elastic modulus and nano hardness with maximum shear stress. Calculated bond length and angles using XRD show higher measures (p < 0.05) in all CQD groups. *****CQD_0.5 %^- exhibited a fibre texture pattern with an orientational distribution resembling an angle distortion. Most bacteria in the biofilms fluoresced red in CQD groups with no colony chain formations observed with *****CQD_0.5 %^- group. CQDs assemblies were observed to cause explosive lysis through loss of cell integrity.

Conclusion: *****CQD_0.5 %^- modified enamel substrate displayed significant crystallite changes providing a novel option for fabrication of diverse functional CQDs aimed at modification of enamel tissue while possessing optimum antimicrobial properties.

According to the principle of minimal invasiveness in modern dentistry, biomimetic remineralization therapy constitutes a significant strategy for the prevention and treatment of early enamel caries. Based on the three "key events" of amelogenesis in vivo, silk fibroin (SF) combined with carboxymethyl chitosan (CMC) successfully formed an SF/CMC composite, and amorphous calcium phosphate (ACP) was then used to form an SF/CMC-ACP nanocomposite with remineralization properties. In our study, SF was used as a template protein for biomimetic amelogenin, ACP was stabilized with CMC and the remineralization was guided using NaClO to simulate the action of proteolytic enzymes. The SF/CMC-ACP nanocomposite demonstrated excellent biocompatibility and enamel remineralization effects in both in vitro/in vivo experiments; thus, a theoretical basis for biomimetic enamel remineralization studies was provided.

Objective: To determine if the PinkWave (PW) light-curing unit (LCU) that emits red and infrared (IR) light as well as violet and blue light improves the depth of cure and degree of conversion (DC) of resin-based composites (RBCs).

Methods: The DC of RBCs at various distances was calculated from data collected at a rate of 13 Hz using attenuated total reflectance Fourier-transform infrared spectroscopy. To assess the contributions of the different wavelengths of light, optical filters were used to block the red and IR light from the PW. The depth of cure was also evaluated by photocuring RBC samples in both metal and plastic molds for 20 s at a 0 mm distance. The length of resin remaining was then measured and divided by 2. Starting from a baseline of 32 °C, the temperature rise during photocuring was measured in the plastic and metal rings reproducing the conditions used to measure the depth of cure and the DC respectively.

Results: In general, the PW produced greater depth of cure, however the use of metal molds greatly reduced this effect because the temperature increase was reduced. Increasing the distance by up to 4 mm from the light tip produced a significant increase in the DC for the RBCs photocured with the PW, but not for the G4. The wavelength of the blue peak (peaking at 473 nm) from the PW was longer compared to the control LCU (peaking at 448 nm). This 25 nm difference negatively affected the photocuring efficiency of some resins.

Significance: The internal optics and the additional red and IR wavelengths from the PW significantly increased the temperature in the RBCs and increased both depth of cure and the DC.

Objective: Functional phosphoric ester monomers containing primers have been widely used in dental adhesives. This study aims to analyze the atomic-level interaction between zirconia and phosphoric ester monomers under different pH conditions (acidic or neutral).

Methods: Solid-state ³¹P NMR spectroscopy was employed to investigate the binding interactions between two types of phosphoric ester monomers-glycerophosphate-dimethacrylate (GPDM) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-with zirconia under varying pH conditions. Contact angles were measured on the zirconia surfaces with and without the application of phosphoric ester monomers. Additionally, tensile bond strength (TBS) tests were conducted to determine the effects of different phosphoric ester monomer-containing primers under different pH conditions on zirconia.

Results: Solid-state ³¹P NMR spectroscopy revealed that both GPDM and MDP exhibited broadened peaks, positioned differently from their unreacted forms, indicating that the environment surrounding the phosphate groups in both GPDM and MDP changed upon adhesion to zirconia at the atomic level. Acidic MDP may form covalent bonds with zirconia through additional esterification on the zirconia surface. MDP-primed zirconia demonstrated a higher contact angle than GPDM-primed zirconia. The highest TBS was observed in the group of MDP reacted with zirconia under acidic conditions.

Significance: These findings suggest that phosphoric ester monomers, particularly MDP in acidic conditions, can chemically bind to zirconia, contributing to enhanced adhesion behavior.

Background: Generally, the bonding of one material to another is important for function, and especially in so-called 'adhesive dentistry'. However, there are concerns about the clinical relevance and the discriminatory power of currently employed tests of bond strength.

Objective: Develop and validate a test protocol based on 4-point bending that may be used to examine the bonding of various dental materials to a range of substrates. The bonding of a resin-based composite (RBC) to dentine is taken as an example.

Methods: Slices of dentine 'coupons' (5.0 × 2.0 × ∼4-6 mm³) from extracted molars were prepared using a diamond saw under running water. Pairs of RBC bars (5.0 × 2.0 × ∼24 mm³) (Z250) were bonded symmetrically either side of a dentine coupon using all combinations of the following treatments: E: acid-etched (Scotchbond Universal Etchant), P: primer (Adper Scotchbond Multipurpose Adhesive); A: adhesive (Adper Scotchbond Multipurpose Primer) (all 3 M) as well as N: no treatment. Following retrieval from the mould, test pieces were immediately subjected to 4-point bending at 23 °C, cross-head speed 0.5 mm/min, until fracture. Three-way analysis of variance on log(flexural strength): etch × primer × adhesive, was applied. Scanning electron microscopy (SEM) was used to examine fracture surfaces and identify failure origins.

Results: Flexural strengths in MPa: N: 1.38 ± 0.56; P: 9.82 ± 0.89; A: 5.12 ± 0.73; E: 9.39 ± 1.78; E + P: 21.03 ± 2.63; E + A: 12.80 ± 1.53; P + A: 17.16 ± 3.03; E + P + A: 20.84 ± 3.93. The treatment main effects (all, p < 10^-12) were not additive, there being significant two-way (p < 10^-5) and three-way (p = 0.037) interactions. There was no significant difference between E + P + A and E + P (p = 0.86).

Conclusion: With good reproducibility (low scatter), discriminatory power (clear treatment effects), economy with regard to substrates, the method has the potential to be adaptable to many systems.