Dental Materials最新文献

Objective: This study measured the beam divergence angle and light output from dental light curing units (LCUs). Twenty LCUs were assessed using a laboratory-grade wide beam imager to determine the relationship between the beam divergence on the irradiance as a function of distance from the light tip.

Methods: The irradiance (mW/cm²) and beam divergence angles (°) at 5, and 10 mm from the tips of 18 Light-Emitting Diode (LEDs), 1 Quartz-Tungsten-Halogen (QTH), and 1 Laser diode LCU.

Results: There were significant differences in the power, irradiance, and emission spectra from the 20 LCUs. At 10 mm from the LCU tip, the irradiance delivered by one LCU decreased by approximately 85.7 %, whereas this decrease was as low as 5.6 % for a different LCU. There was a positive correlation between the divergence angle reported by the wide beam imager and the reduction in irradiance. The laser diode LCU had the least beam divergence and the smallest decrease in irradiance as the distance increased. In contrast, the QTH LCU with the turbo light guide had the greatest beam divergence and the greatest reduction in irradiance as the distance increased. 50 % of the LCUs tested would require exposure times longer than 20 s to deliver 10 J/cm² at the 10 mm distance.

Significance: The wide beam imager is a useful tool for measuring the beam divergence from LCUs and predicting the effect of distance on their irradiance. At 10 mm, some LCUs may require a fivefold increase in the exposure time to deliver the same energy they deliver at 0 mm from the tip of the LCU.

Objectives: Previous studies reported various methods of measuring fracture toughness of dental ceramics. The objectives of this study were to compare different methods and to validate fractal analysis to estimate fracture toughness for a polycrystalline dental ceramic.

Methods: Bar-shaped specimens were prepared from 3 mol% yttria-stabilized tetragonal polycrystalline (3Y-TZP) ceramic. Each specimen was prepared with a series of indentations using a Vickers diamond at 150 N followed by loading in 4-point flexure until failure. Fracture toughness (K_c) was calculated using modified indentation (MI), quantitative fractography (QF), and surface crack in flexure with residual stresses (SCF-RS) techniques. We estimated fracture toughness using fractal analysis. Epoxy replicas of fracture surfaces were scanned using the atomic force microscope (AFM) followed by noise filtering. The FRACTALS software was used to determine fractal dimensional increment (D*) by the Minkowski cover algorithm. Fracture toughness was estimated using the relationship between K_c and square-root of D* for polycrystalline ceramics.

Results: Mean fracture toughness by MI, QF, and SCF-RS techniques were 4.56 ± 0.44 MPa·m^1/2, 4.14 ± 0.82 MPa·m^1/2, and 4.09 ± 0.93 MPa·m^1/2, respectively. Mean fracture toughness estimated from D* values was 2.80 ± 0.13 MPa·m^1/2.

Significance: The fracture toughness of 3Y-TZP ceramic was calculated using different methods. Fractal dimension can be used to estimate the baseline fracture toughness for this material and can be paired with other methods to estimate the amount of transformation toughening.

Objectives: To report up to 9-year results of a prospective and retrospective study on non-invasive full-mouth rehabilitation of worn dentition with PICN CAD-CAM restorations using the One-Step No-Prep technique. The secondary objective is to evaluate the influence of restoration thickness on fracture of restorations.

Methods: A total of 580 Vita Enamic restorations (218 anterior and 362 posterior; 260 monoblock (MO) and 320 multiColor (MC)) in 24 patients were clinically evaluated once a year (up 9 months to 9 years) according to FDI criteria. Patient data and prosthetic parameters were registered. The minimum thickness of restorations was measured in 15 patients.

Results: The Kaplan-Meier survival rate of restorations at 9 years was 98.4 % (100 % for anterior and 96.7 % for posterior) and the success rate was 79.7 %, while the success rate excluding minor chipping requiring only polishing as failure was 86.7 %. Actually, minor chipping was the leading cause of failure and significantly more fractures were observed in the posterior region (9.2 times higher risk), particularly in the first and second molars or when the restoration thickness was less than 0.56 mm. Except for fracture, FDI evaluation showed clinically acceptable results for all restorations, mostly rated as excellent. Results remained consistent over time, including material luster and color, with no staining. MC showed superior esthetics compared to MO. Patient satisfaction was high.

Significance: The One-Step No-Prep technique exhibits successful long-term outcomes, and PICN (hybrid ceramic) is an appropriate material for this non-invasive treatment of tooth wear. Nevertheless, the minimum thickness of posterior restorations should be 0.6 mm, particularly at occlusal contact points. MultiColor blocks are recommended for esthetics.

Objective: To synthesize bilayer zirconia systems based on commercial or recycled 3Y-TZP obtained from non-milled remnants and to compare their optical and mechanical properties before and after aging.

Methods: Bilayer zirconia samples were fabricated using either recycled 3Y-TZP (3Y-R/4Y and 3Y-R/5Y) or commercial powders (3Y/4Y and 3Y/5Y). Microstructure and phase composition were analyzed using ScanningElectronMicroscopy (SEM) and X-Ray Diffraction (XRD). Optical and mechanical properties were assessed via reflectance and biaxial flexural strength tests (BFS), followed by fractographic analysis. Optical properties and BFS data were analyzed using two-way ANOVA and Tukey test, and Weibull statistics, respectively.

Results: Recycled powder exhibited particle sizes < 2.07μm. SEM micrographs depicted dense surfaces with largest grains in the 5Y, followed by recycled-3Y, 4Y, and commercial-3Y. XRD analysis revealed tetragonal peaks in commercial and recycled 3Y-TZPs, and tetragonal and cubic phases in the 4Y and 5Y surfaces. Aging induced significant phase transformation in 4Y (∼40 %), commercial- (58 %) and recycled-3Y (53 %), with no effect in 5Y surfaces. Commercial bilayers exhibited higher translucency and strength (∼1130 MPa) compared to recycled bilayers (∼935 MPa), with no significant differences within commercial, nor within recycled groups. Aging decreased contrast ratio for recycled groups and increased the strength of all groups. While all groups presented high reliability up to 500MPa, commercial bilayers outperformed recycled systems at 800-MPa.

Significance: The synthesis of bilayered systems using recycled-3Y was successful, resulting in high reliability in missions up to 500MPa. Bilayers based on commercial powder demonstrated superior translucency, strength, and reliability at 800MPa compared to their recycled counterparts.

Objectives: To characterize two experimental zirconia bilayer materials compared to their monolithic controls, before and after hydrothermal aging.

Methods: Commercial zirconia powders were utilized to fabricate two bilayer materials: 3Y-TZP+ 5Y-PSZ (3Y+5Y/BI) and 4Y-PSZ+ 5Y-PSZ (4Y+5Y/BI), alongside control groups 3Y-TZP (3Y/C), 4Y-PSZ (4Y/C), and 5Y-PSZ (5Y/C). Compacted specimens were sintered (1550 °C- 2 h, 3 °C/min), and half of them underwent hydrothermal aging (134 °C-20h, 2.2 bar). Characterizations were performed through scanning-electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, reflectance tests and biaxial flexural strength test (ISO:6872). Weibull statistics were applied to determine the characteristic strength and Weibull modulus. Grain size and optical properties were analyzed using two-way ANOVA followed by the Tukey test.

Results: Degradation regions and monoclinic phase were observed at aged 3Y-TZP and 4Y-PSZ surfaces. Significant differences were observed in the evaluation of optical properties between the bilayer and control groups. The bilayer materials presented intermediate characteristic strength values compared to their controls and aging significantly increased the strength of some groups.

Significance: Experimental bilayer materials presented lower mechanical properties than monolithic controls, 3Y/C and 4Y/C. Hydrothermal aging increased the characteristic strength of bilayered and monolithic controls, except for 5Y-PSZ. Both experimental bilayer systems, as well as monolithic controls, met the ISO 6872:2015 requirements for single-unit crowns (100 MPa), 3-unit fixed dental prostheses (FDPs) up to premolars (300 MPa), and 3-unit FDPs involving molars (500 MPa). However, for FDPs with four or more units, only monolithic 3Y-TZP and 4Y-PSZ, and bilayered 3Y+5Y met the required minimum flexural strength (≥800 MPa).

Objective: To assess the impact of mechanical decontamination using rotary brushes on the surface topography, elemental composition, roughness, and wettability of titanium implant surfaces.

Methods: Four commercially available rotary brushes were used: Labrida BioClean Brush® (LB), i-Brush1 (IB), NiTiBrush Nano (NiTiB), and Peri-implantitis Brush (PIB). Seventy-five titanium discs with sandblasted, large-grit, acid-etched (SLA) surfaces were randomly assigned to five groups (n = 15): LB, IB, NiTiB, PIB, and a control group. Each disc was treated for 60 seconds with the respective rotary brush according to the manufacturer's instructions. Surface morphology was analysed using Scanning Electron Microscopy (SEM), surface elemental composition with Energy Dispersive X-ray (EDX), surface roughness via optical profilometry, and wettability with a droplet shape analyser.

Results: SEI analysis revealed morphological changes, including scratches, flattening, and loose titanium particles in the IB, PIB, and NiTiB groups, whereas the LB group preserved the original surface morphology. SEM-EDX analysis showed that LB, PIB, and NiTiB groups closely match the control elemental composition. However, IB groups showed significantly different composition. Surface roughness values in the IB, PIB, and NiTiB groups differed significantly from the control (p < 0.05), whereas the LB group had comparable roughness values (p > 0.05). Contact angle measurements indicated enhanced wettability in IB, PIB, and NiTiB groups (p < 0.05), while the LB group exhibited values comparable to the control (p > 0.05).

Significance: Mechanical decontamination of implant surfaces utilising rotary brushes can alter implant surface properties.