Purpose: To synthesize niobium silicate particles (SiNb) and incorporate into resin-based luting agents. Methods: SiNb particles were synthesized and characterized by x-ray diffraction, FTIR spectroscopy, particle size, and specific surface area. Luting agents were formulated with 50 wt% BisGMA, 30 wt% TEGDMA and 20 wt% UDMA. BAPO was used as a photoinitiator in 1mol%. The SiNb particles were incorporated into the agents at concentrations of 50 wt% (SiNb50%) or 65% wt% (SiNb65%). Barium glass particles at the same concentrations were used as controls (SiBa50% and SiBa65%). Refractive index, degree of conversion (DC), polymerization kinetics, softening in solvent, radiopacity, film thickness, color stability, flexural strength (FS) and micro shear bond strength (µSBS) were evaluated. Results: SiNb particles were successfully synthesized with an adequate structure to be applied as inorganic fillers. SiNb groups had higher DC, lower %ΔKHN, greater film thickness and greater radiopacity than the SiBa groups. Color stability was greater for SiNb50% and SiNb65% after six months of storage, as demonstrated by ΔE00. ΔWID values were lower for the SiBa groups. FS results decreased over time, and lower values were found for SiNb. In µSBS, the values of SiNb65% were higher at 24 h (45.22 MPa) and at six months (36.83 MPa), with statistically differences from values for the SiBa groups. Conclusions: SiNb particles were successfully synthesized using the sol-gel method, and their incorporation into luting agents at a concentration of up to 65% improved the physicomechanical characteristics and color stability of these agents.
Purpose This systematic review and meta‐analysis of in vitro studies compared the prepolymerized acrylic resin used for CAD/CAM complete denture manufacturing versus the heat‐polymerized acrylic resin for conventional complete dentures in terms of surface roughness, wettability, hardness and flexural strength. Materials and Methods An electronic search was performed in the PubMed, Embase, LILACS and Web of Science databases, without language or date restrictions. Gray literature and manual search tools were also used. The systematic review was carried out by two researchers independently, following the inclusion criteria: in vitro studies testing the CAD/CAM acrylic resin with a control group of heat‐polymerized acrylic resin which compared at least one of the four material properties above. The meta‐analysis was performed separately for each property, using a random effect model. Results Of the 914 studies found by means of search strategies, 698 were selected for the systematic review. After applying the eligibility criteria, only 17 articles were selected for the qualitative analysis in the systematic review; among these, 14 were included in the quantitative meta‐analysis. The CAD/CAM prepolymerized acrylic resin in blocks had similar properties when compared to heat‐polymerized acrylic resin in almost all outcome measures, with the exception of a statistically significant reduction in surface roughness. Conclusions Based on the findings of this systematic review and meta‐analysis, equally satisfactory results can be expected from dental prosthesis manufactured by the CAD/CAM system when compared to conventional ones, with the additional potential of reducing the pigmentation and attached microorganisms due to the reduced surface roughness of the prepolymerized resin.
The use of digital technology is increasing rapidly in modern dentistry. However, there is still not enough data in the literature regarding the manufacture of milled frameworks on implant-supported prosthesis. Purpose: To assess the stress caused on dental implants by milled frameworks of different sizes made through digital workflow and to compare two types of scanners. Methods: An edentulous model of a maxilla was created through 3D printing, where six equidistant implants were installed with a 50Ncm torque. Over each implant was installed a 5.5mm mini conical abutment with a 32Ncm torque. Over these abutments, two types of scanning were performed: intraoral scanners (IOS) and laboratory scanners (LS), from which each framework was designed and milled from titanium discs. These frameworks were made over two, four and six implants, simulating different clinical situations. To analyze the deformation, two strain gages were attached to the abutment surfaces, on the buccal and mesial surfaces. Results were analyzed using a paired Student’s t-test, with significance level of 0.005. The passivity was evaluated by an experienced operator. Results: LS scanners had the lowest deformation, when compared to the IOS. The greater the distance between the implants, the higher the deformation. In frameworks on 4 implants, the deformation was greater, as it was the distance between the implants. The groups on 2 implants showed the least strain (p < 0.005). All frameworks were considered passive, as they all fit the passivity criteria. Conclusions: All scanning techniques reported are reliable. The milled frameworks are passive and accurate, with very little deformation, and they can be safely supported by implants, without bone resorption.
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