Comparative Analysis of Fused Deposition Modeling and Digital Light Processing Techniques for Dimensional Accuracy in Clear Aligner Manufacturing.

BACKGROUND This study aimed to compare fused deposition modeling (FDM) and digital light processing (DLP) techniques in terms of dimensional accuracy for printing dental models used for the manufacture of clear dental aligners. MATERIAL AND METHODS Based on the intraoral scan of an adult patient, a sequence of 10 aligner models was created using BlueSkyPlan4. The test models (n=30) were fabricated with 2 desktop 3D printers: (DLP) and (FDM) printers. Two groups of samples were created (digitized using a desktop optical scanner). To calculate trueness (n=20) and precision (n=10), printed models were compared to the source files (REF). REF, DLP, and FDM files were superimposed and converted to point clouds. The cloud-to-cloud distances were calculated using CloudCompare software. Using the same algorithm, distortions of models were measured. Data were analyzed using one-way ANOVA and Tukey's post hoc test. RESULTS Significant differences were found between the trueness and precision of DLP and FDM groups. The average calculated trueness of DLP and FDM was 0.096 mm (0.021) (P<0.001) and 0.063 mm (0.024) (P<0.001), respectively. The average calculated precision of DLP and FDM was 0.027 mm (0.003) (P<0.001) and 0.036 mm (0.003) (P<0.001), respectively. A widening (0.158 mmfor DLP and 0.093 mmfor FDM, P=0.05) and twisting (0.03 mmfor DLP and 0.043 mmfor FDM, P=0.05) of the printed models was observed. CONCLUSIONS Both printers had sufficient precision for aligner models manufacturing. FDM showed a higher trueness and this device can be applied as an alternative to DLP. Polymerization shrinkage is a significant factor in decreasing the trueness of DLP printers.

Effect of Thermocycling on the Bond Strength of Self-Adhesive Resin Cements Used for Luting CAD/CAM Ceramics to Human Dentin.

The aim of the study was to evaluate the influence of thermocycling on the shear bond strength of self-adhesive, self-etching resin cements luted to human dentin and computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Three modern self-adhesive dental cements (Maxcem Elite, RelyX U200, Panavia SA) were used to lute three CAD/CAM ceramics (IPS Empress CAD, IPS e.max CAD, IPS e.max ZirCAD) onto the dentin. One conventional cement (Panavia V5) served as a control. After preparation, the samples were subjected to thermocycling as a method of artificial aging of dental materials applied to simulate long-term use in oral conditions. Shear bond strength was evaluated according to PN-EN ISO 29022:2013-10 and failure modes were observed under a light microscope. Statistical analysis was performed. The study demonstrated that a combination of ceramics and cements directly impacts the bond strength. The highest bond strength was observed in Panavia V5, lower in Panavia SA and Maxcem Elite and the lowest-in RelyX U200. Adhesive failure between human dentin and cements was the most common failure mode. Moreover, thermocycling highly decreased bond strength of self-adhesive, self-etching cements.

Self-assessment of Rationing and Quality of Nursing Care.

BACKGROUND: Nursing care rationing has been a widespread problem in everyday nursing practice for many years. PURPOSE: The aim of this research study was to assess the prevalence of care rationing among nurses working in Poland. METHODS: The study was conducted among a population of 1310 nurses. To examine the dependencies between the sociodemographics and unfinished nursing care, the Polish adaptation of the Perceived Implicit Rationing of Nursing Care questionnaire and an investigator-developed questionnaire were used. RESULTS: The mean level of missed care was 1.16 (SD = 0.7). The significant predictors of care rationing were associated with the quality of patient care (ßstd = -.43, P < .001) and general work satisfaction (ßstd = -.15, P < .001). CONCLUSIONS: Job satisfaction and the quality of nursing care should be constantly monitored as these factors are significantly associated with the levels of care rationing.

Brief Narrative Review on Commercial Dental Sealants-Comparison with Respect to Their Composition and Potential Modifications.

The scope of this paper is to compare different dental sealants and flow materials indicated for sealing pits and fissures considering their chemical formula. The narrative review aims to address the following questions: What is the essence of different dental sealants' activity, how does their chemical formula affect their mechanisms of caries prevention, and what makes a dental sealant efficient mean of caries prevention? Another vital issue is whether the sealants that contain fluoride, or any other additions, have potentially increased antimicrobial properties. An electronic search of the PubMed, Cochrane, Web of Science, and Scopus databases was performed. The following keywords were used: (dental sealants) AND (chemical composition). Additionally, information about composition and indications for clinical use provided by manufacturers were utilized. All of the considered materials are indicated for use both in permanent and primary dentition for sealing fissures, pits, and foramina caeca. The selection of suitable material should be made individually and adjusted to conditions of the sealing procedure and patient's needs. Cariostatic mechanisms increasing sealants' effectiveness such as fluoride release are desired in modern dentistry appreciating preventive approach. The review aims are to find crucial elements of sealants' composition which affect their cariostatic mechanisms.

Evaluation of Recovery Methods for Fragaria vesca L. Oil: Characteristics, Stability and Bioactive Potential.

Wild strawberry (Fragaria vesca L.) seed oil (WSO) recovered by two methods-cold pressing (CP) and extraction with supercritical carbon dioxide (SCO2E)-taking into account the different extraction times, was characterized for its composition and quality. The cytotoxicity assessment of WSOs was also carried out using the normal human dermal fibroblast (NHDF) cell line. Tocopherol and total polyphenol contents were significantly higher in WSO recovered by SCO2E, up to 1901.0 and 58.5 mg/kg, respectively, in comparison with CP oil. In CP oil, the highest content of carotenoids and squalene was determined (123.8 and 31.4 mg/kg, respectively). Phytosterol summed up to 5396 mg/kg in WSO collected in 30 min of SCO2E. Moreover, the highest oxidative stability was found for this oil. All studied WSOs were non-cytotoxic in lactate dehydrogenase (LDH) leaching and sulforhodamine B (SRB) assays; however, oils collected by SCO2E in 15 and 30 min were found to be cytotoxic in the tetrazolium salt (MTT) test, with the CC50 at a concentration of 3.4 and 5.5%, respectively. In conclusion, the composition of WSO indicates that, depending on the method of its recovery, seeds can have different bio-potencies and various applications.

Resin Composite Materials for Chairside CAD/CAM Restorations: A Comparison of Selected Mechanical Properties.

OBJECTIVE: The aim was to evaluate the flexural strength, flexural modulus, microhardness, Weibull modulus, and characteristic strength of six resin composite blocks (Grandio Blocs-GR, Tetric CAD-TE, Brilliant Crios-CR, Katana Avencia-AV, Cerasmart-CS, and Shofu Block HC-HC). METHODS: Flexural strength and flexural modulus were measured using a three-point bending test and microhardness using the Vickers method. Weibull analysis was also performed. RESULTS: The materials showed flexural strength ranging from 120.38 (HC) to 186.02 MPa (GR), flexural modulus from 8.26 (HC) to 16.95 GPa (GR), and microhardness from 70.85 (AV) to 140.43 (GR). Weibull modulus and characteristic strength ranged from 16.35 (CS) to 34.98 (TE) and from 123.45 MPa (HC) to 190.3 MPa (GR), respectively. CONCLUSIONS: GR, TE, and CR presented significantly higher flexural strength, modulus, Weibull modulus, and characteristic strength than the others.

Printable and Machinable Dental Restorative Composites for CAD/CAM Application-Comparison of Mechanical Properties, Fractographic, Texture and Fractal Dimension Analysis.

Thanks to the continuous development of light-curing resin composites it is now possible to print permanent single-tooth restorations. The purpose of this study was to compare resin composites for milling -Gandio Blocks (GR), Brilliant Crios (CR) and Enamic (EN) with resin composite for 3D printing-Varseo Smile Crown plus (VSC). Three-point bending was used to measure flexural strength (σf) and flexural modulus (Ef). The microhardness was measured using a Vickers method, while fractographic, microstructural, texture and fractal dimension (FD) analyses were performed using SEM, optical microscope and picture analysis methods. The values of σf ranged from 118.96 (±2.81) MPa for EN to 186.02 (±10.49) MPa for GR, and the values of Ef ranged from 4.37 (±0.8) GPa for VSC to 28.55 (±0.34) GPa for EN. HV01 ranged from 25.8 (±0.7) for VSC to 273.42 (±27.11) for EN. The filler content ranged from 19-24 vol. % for VSC to 70-80 vol. % for GR and EN. The observed fractures are typical for brittle materials. The correlation between FD of materials microstructure and Ef was observed. σf of the printed resin depends on layers orientation and is significantly lower than σf of GR and CR. Ef of the printed material is significantly lower than Ef of blocks for milling.

Does image file transfer, exposure time and optimization algorithm affect digital intraoral radiographs?

BACKGROUND: The transfer of digital radiographic images is widely practiced. Digital image processing can influence the perception of image quality. The question arises as to how exposure, internal image adjusting algorithms and image file transfer affect the optical density of digital radiographs. OBJECTIVES: To evaluate the influence of exposure time, optimization and file transfer on digital radiographs. MATERIAL AND METHODS: Calibration patterns were formed and a series of digital radiograms were recorded under standardized conditions. The radiographs were exported and then imported into the same software. Three groups of radiographs were analyzed: A - images originally performed and recorded in the software; B - images imported after exporting an optimized image; and C - images imported after exporting an image without optimization but with measurements of the density of the marked regions of interest. RESULTS: An increase of the exposure time decreases optical density. The optimization algorithm increases contrast and decreases differences between exposure times. Long exposures affect the visibility of objects with low optical density. After importing the images in Group B, there was a risk of using the optimization algorithm twice. When optimization was not performed, there were no differences between Groups B and A. In Group C, there was no risk of doubling the optimization algorithm. CONCLUSIONS: The transfer of digital radiographs can exert an influence on the optical density values. To avoid the risk of image distortion, files should be exported without image optimization.

Comparison of the Accuracy of 3D Images Obtained fromDifferent Types of Scanners: A Systematic Review.

Introduction: The purpose of this systematic review was to compare the accuracy of the three-dimensional images among different scanners, scanning techniques, and substrates. Materials and methods. Electronic databases (PubMed and Elsevier) were searched until March 2020. The systematic search was performed to identify the most precise method of obtaining a 3D image of the dentition. Results: Thirteen articles out of 221, considering the accuracy of 3D images, were selected. The main factors that are considered to have an influence on the precision are substrate type in the oral cavity, experience of the scanner's operator, direct vs. indirect scanning, and the reproducibility of the procedure. Conclusion: Substrate type does have an impact on the overall accuracy of intraoral scans where dentin has the most and enamel the least accurately recorded dental structure. Experience of the operator has an influence on the accuracy, where more experienced operators and smaller scan sizes are made for more accurate scans. A conventional impression technique in a full-arch image provided the lowest deviation. The reproducibility of direct scanning was comparable to indirect scanning although a slight difference was noticeable (0.02 mm).

The mechanical properties of human dentin for 3-D finite element modeling: Numerical and analytical evaluation.

BACKGROUND: The FEM is often used in investigations of dentin loading conditions; however, its anisotropy is mostly neglected. OBJECTIVES: The purpose of the study was to evaluate the anisotropy and the elastic properties of an equivalent homogenous material model of human dentin as well as to compare isotropic and anisotropic dentin FE-models. MATERIAL AND METHODS: Analytical and numerical dentin homogenization according to Luciano and Barbero was performed and E-modulus (E), Poisson's ratios (v) G-modulus (G) were calculated. The E-modulus of the dentin matrix was 28.0 GPa, Poisson's ratio (v) was 0.3; finite element models of orthotropic and isotropic dentin were created, loaded and compared using Ansys® 14.5 and CodeAster® 11.2 software. RESULTS: Anisotropy of the dentin ranged from 6.9 to 35.2%. E-modulus and G-modulus were as follows: E1 = 22.0-26.0 GPa, E2/E3 = 15.7-23.0 GPa; G12/G13 = 6.96-9.35 GPa and G23 = 6.08-8.09 GPa (highest values in the superficial layer). In FEM analysis of the displacement values were higher in the isotropic than in the orthotropic model, reaching up to 16% by shear load, 37% by compression and 23% in the case of shear with bending. Strain values were higher in the isotropic model, up to 35% for the shear load, 31% for compression and 35% in the case of shear with bending. The decrease in the volumetric fraction and diameter of tubules increased the G and E values. CONCLUSIONS: Anisotropy of the dentin applied during FEM analysis decreased the displacements and strain values. The numerical and analytical homogenization of dentin showed similar results.