Correction: Klimek et al. A Comparison of the Structure and Selected Mechanical Properties of Cr/Co Alloys Obtained by Casting and Selective Laser Melting. J. Funct. Biomater. 2024, 15, 61.

In the original publication [...].

A Comparison of the Structure and Selected Mechanical Properties of Cr/Co Alloys Obtained by Casting and Selective Laser Melting.

Selective laser melting (SLM) technologies are becoming increasingly popular. The aim of the work is to compare the metallographic structure, hardness, and selected strength properties of alloys obtained by casting and by SLM, with a particular emphasis on fatigue strength. Twenty Cr/Co alloy bars were made by casting or SLM, and samples of appropriate dimensions were prepared for individual tests. The microstructures of the samples were tested by metallography, and then tested for hardness, impact strength, tensile strength, bending strength, and fatigue strength; they were also subjected to fracture after bending, tensile, fatigue, and impact tests, with the resulting fractures examined by scanning electron microscopy (SEM). Primary dendrites and small amounts of gas bubbles were present in the cast samples ground lengthwise. The SEM samples were more finer grained and uniform. Compared to the casting samples, the SLM samples demonstrated higher hardness, lower mean impact strength and higher tensile strength. The casting samples also displayed lower mean elongation values. The casting samples demonstrated slightly higher fatigue strength. The fractures of the casting samples showed an interdendritic character with clearly visible dendrites at the fracture, while those of the SLM samples were also intergranular, but finer grained. SLM generally results in better strength properties, while casting obtains slightly greater fatigue strength.

An Evaluation of the Mechanical Properties of a Hybrid Composite Containing Hydroxyapatite.

There is currently a lack of scientific reports on the use of composites based on UDMA resin containing HAp in conservative dentistry. The aim of this study was therefore to determine the effect of hydroxyapatite content on the properties of a hybrid composite used in conservative dentistry. This paper compares a commercial hybrid composite with experimental composites treated with 2% by weight (b/w), 5% b/w, and 8% b/w hydroxyapatite. The composites were subjected to bending strength, compression, and diametrical compression tests, as well as those for impact strength, hardness, and tribological wear. The obtained results were subjected to statistical analysis. Increased hydroxyapatite was found to weaken the mechanical properties; however, 2% b/w and 5% b/w hydroxyapatite powder was found to achieve acceptable results. The statistical analysis showed no significant differences. HAp is an effective treatment for composites when applied at a low concentration. Further research is needed to identify an appropriate size of HAp particles that can be introduced into a composite to adequately activate the surface and modification its composition.

Effect of Sandblasting Parameters and the Type and Hardness of the Material on the Number of Embedded Al2O3 Grains.

BACKGROUND: Is abrasive blasting accompanied by the phenomenon of driving abrasive particles into the conditioned material? METHODS: Three hundred and fifteen cylindrical disks of three types of metal alloy (chromium/cobalt, chromium/nickel, titanium, and sintered zirconium dioxide) were divided into four groups (n = 35) and sandblasted at pressures of 0.2, 0.4, or 0.6 MPa with aluminum oxide (Al2O3), grain size 50, 110, or 250 µm. Then, the surface topography was examined using a scanning microscope, and the amount of embedded grain was measured using quantitative metallography. For each group, five samples were randomly selected and subjected to Vickers hardness testing. In the statistical analyses, a three-factor analysis of variance was carried out, considering the type of material, the size of gradation of the abrasive, and the amount of pressure. RESULTS: The smallest amounts of embedded abrasive (2.62) were observed in the ZrO2 treatment, and the largest (38.19) occurred in the treatment of the Ti alloy. An increase in the gradation and the pressure were a systematic increase in the amount of embedded grain. CONCLUSIONS: After abrasive blasting, abrasive particles were found on the surface of the materials. The amount of driven abrasive depends on the hardness of the processed material.

Evaluation of the Effect of the Addition of Hydroxyapatite on Selected Mechanical and Tribological Properties of a Flow-Type Composite.

(1) Background: The aim of the study was to determine the effect of modification with sintered hydroxyapatite (HAp) on selected mechanical and tribological properties of a flow-type composite. (2) Methods: Samples in the shapes of cuboidal beams (n = 120) and cylinders (n = 120) with the proper dimensions were prepared from a standard flow-type composite and others with the addition of 2% wt., 5% wt., and 8% wt. sintered hydroxyapatite. The bending strength, compression strength, diametral compression strength, impact resistance, hardness, and tribological properties were compared. (3) Results: In all cases, it was established that an increase in the amount of HAp caused a reduction in the bending, compression, and diametral compression strength. Increasing the amount of added HAp also reduced the impact strength, hardness, and wear resistance. However, the differences were statistically insignificant. (4) Conclusions: The addition of hydroxyapatite to a flow-type composite material worsened its mechanical and tribological properties; however, the obtained values were acceptable with 2% wt. and 5% wt. HAp.

Clinical longevity and trend analysis of 801 ultrathin ceramic veneers: A clinical cohort study.

STATEMENT OF PROBLEM: Whether ultrathin ceramic veneers are a suitable treatment alternative to conventional ceramic veneers is unclear. PURPOSE: The purpose of this prospective clinical cohort study was to evaluate the efficacy and longevity of nonpreparation and minimally invasive ceramic veneers and the influence of existing restorations and ceramic type and to define the relationship between the number of veneers placed on different teeth and in different locations, as well as age and sex correlations. MATERIAL AND METHODS: A total of 801 veneers were placed on incisors, canines, and premolars on maxillary and mandibular teeth between January 2011 and August 2019 (ABR number: RNN/92/19/KE). Feldspathic or feldspathic and lithium disilicate veneers were made, etched, silanated, and cemented. The restorations were evaluated 2 weeks after placement and then every 6 months by using the modified United States Public Health Service (USPHS) criteria. The relationship between participant age and number of veneers was analyzed by using the Spearman rank coefficient test and the Mann-Whitney U test. Changes in the number of participants and veneers in subsequent years were analyzed based on the Spearman rank correlation coefficient. The trend between the location of veneers and the sex of the participants was analyzed by using the chi-square test for trend. Longevity tables and a survival curve for the veneers were prepared based on the Kaplan-Meier method. The relationships between veneer longevity and the type of ceramic used and the presence of restorations were compared by using the Taron-Ware test (α=.05). RESULTS: The mean longevity of the intact veneers was 8.45 years. Clinical success was 99.7% after 1 year and 97.9% after 4 years; this value remained constant until the end of the study. Most participants were women (n=122; 84.1%), and the mean age was 41 years; median 40 years. The number of veneers placed on mandibular teeth each year increased over the subsequent years. CONCLUSIONS: The longevity of ultrathin veneers after 9 years of observation was not related to the ceramic used or to the presence of a composite resin restoration. Veneers were more commonly placed in middle-aged women and in mandibular anterior teeth.

The Influence of Material Type and Hardness on the Number of Embedded Abrasive Particles during Airborne-Particle Abrasion.

(1) Background: This paper aims to determine the influence of hardness on the number of abrasive material grains (SiC) embedded on the surface metal alloys and ZrO2 during abrasion. (2) Methods: Cylindrical samples were created: 315 made of Cr/Co, Ni/Cr or Ti, and 315 made of sintered ZrO2- 3TPZ-Y. These were divided into four groups (each n = 35 samples), and were treated with SiC grain sizes 50, 110, and 250 µm at pressures 0.2, 0.4, or 0.6 MPa. The samples were then observed in SEM to study SE and BSE. The surface coverage of abrasive material particles was determined by quantitative metallography. Five samples from each group were subjected to hardness measurements. The results were compared with three-factor variance analysis with using the post hoc Tukey test. (3) Results: The highest amount (40.06) of embedded abrasive was obtained for Ti alloy with a gradation of 250µm at a pressure of 0.6 MPa. The smallest amount of embedded grain (2.66) was obtained for ZrO2 for the same treatment parameters. (4) Conclusions: The amount of embedded abrasive particles depends on the type of treated material, gradation particles, and the amount of applied pressure. Harder treated materials are more resistant to grains of abrasive becoming embedded on surface.

A prospective comparative analysis of the survival rates of conventional vs no-prep/minimally invasive veneers over a mean period of 9 years.

OBJECTIVES: The present study compares the survival rates of 186 conventional and no-prep/minimally invasive porcelain veneers in 35 patients over a mean period of 9 years. MATERIALS AND METHODS: The veneers were placed on the incisors, canines, and premolars in 35 patients between January 2009 and December 2010. Fourteen patients received 84 conventional veneers, and 21 patients received 102 no-prep/minimally invasive veneers. The restorations were evaluated at baseline and after every 6 months until June 2019 based on modified United States Public Health Service criteria. The data was analyzed by using Wilcoxon-Breslow-Gehan and Taron-Ware tests. Kaplan-Meier survival and success curves were plotted for two groups of veneers. The results were compared by using the log rank test. A test probability of P < .05 was regarded as significant, while a test probability of P < .01 was considered to be statistically significant. RESULTS: The mean survival rate, according to the Kaplan-Meier estimator, was 9.67% for conventional veneers and 100% for the no-prep or minimal prep veneers. A total of ten absolute failures were observed in six patients: eight restoration chipping/fractures, one debonding, and one fracturing of the tooth. Mean success rate time for conventional veneers without absolute or relative failures was 9.32 years, and 10.28 years for no-prep/minimally invasive veneers. CONCLUSIONS: Over a mean observation period of 9 years, the survival rate of no-prep/minimally invasive veneers exceed that of conventional veneers. CLINICAL RELEVANCE: No-prep/minimally invasive veneers appear very effective and should always be considered in certain clinical situations.

Effect of zirconia surface treatment on its wettability by liquid ceramics.

STATEMENT OF PROBLEM: The wettability of the framework by liquid ceramics is important in ensuring a suitable bond between veneering ceramics and zirconia. PURPOSE: The purpose of this in vitro study was to examine the dependence of the wetting angle on temperature to determine the transition temperature from nonwettable to wettable states and to calculate the values of the relative wetting forces of the milled surfaces. MATERIAL AND METHODS: Fifty zirconia cylinders were divided into 5 groups (n=10) and subjected to the following treatments: milling, grinding, polishing, and airborne-particle abrasion with Al2O3 or SiC. After treatment, the specimens were rinsed, dried, and examined with respect to their wettability by liquid ceramics by using the automated Thermo-Wet test bench. The results were statistically analyzed by an ANOVA (α=.05). RESULTS: The most rapid wettability was obtained through airborne-particle abrasion with Al2O3 at 930 °C. Additionally, the highest relative bond strength (with respect to the machined surface) was obtained with Al2O3 abrasion. CONCLUSIONS: Because of variations in the wettability of the zirconia surface after different treatment methods, the firing temperature of the ceramic should also vary depending on the type of surface treatment applied. Thus, it is determined individually according to the chosen method.

The Use of the Finite Elements Method (FEM) to Determine the Optimal Angle of Force Application in Relation to Grooves Notched into a Zirconia Coping with the Aim of Reducing Load on a Connection with Veneering Ceramic.

OBJECTIVE OF STUDY: To investigate, using the FEM, the influence of different notching angles on a zirconium dioxide coping with the aim of establishing the optimal connection conditions with veneering ceramic. MATERIALS AND METHODS: To calculate the stresses in the connection between zirconia coping and veneering ceramic, a model comprising grooves cut perpendicular was adopted. Such a notch profile was used to design the shape and spacing of the grooves on an FEM model simulating a zirconium dioxide coping. For discretization purposes we used twenty-node solid BRICK elements featuring intermediate nodes with three degrees of freedom in each node. The model was divided into 117 745 finished elements and 439 131 nodes. The problem was solved with a GLU type contact. The same load F = 1N divided by the number of nodes on the external surface was applied to each node of the outer surface of the base. In subsequent computing variants the F load changed the orientation by angle α from 0° to 45° every 15°. RESULTS: The highest level of material strain occurs at angle α = 0° σred  max =309 MPa and the lowest at angle α = 45° σred  max =220 MPa. The highest positive stress pressure occurs at angle α = 0° pmax=251 MPa, pmin=-354 MPa and the lowest at angle α = 15°, pmax=171 MPa, pmin=-186 MPa. In the case of tangential stresses on the coping-veneering ceramic connection, the highest values were noted at angle α = 15° τmax=44,4 MPa and the lowest at angle α = 45° τmax=32,7 MPa. CONCLUSIONS: To reduce the load on the zirconia-veneering ceramic connection, the notches should be made at an angle of α = 45°.

The Use of the FEM to Identify the Optimal Groove Dimensions Ensuring the Least Stressed Connection between a Zirconia Coping and Veneering Ceramic.

Background: To examine the influence of coping notches with varying groove widths and depths on the quality of the connection with ceramic. Methods: Ten rectangular sintered zirconia (3Y-TZP) samples were etched with a neodymium-yag laser Nd:YAG. Then, a profilometer was used to test the depths and spacing of the grooves. A notch profile was used to design the shapes and spacing of the grooves based on a finite element method (FEM) simulating zirconia. The following situations were simulated: an increase in groove width from 100% to 180% and depth from 40% and 80%; and a 40% depth and width. Results: An increase of 10% in the baseline width caused an insignificant reduction of the strain in the connection. A further increase in this dimension led to a 50% increase in strain with a 40% increase in width. An increase in the groove depth by 40% reduced the strain level by 13%, while an increase in the groove depth by 80% reduced the strain level by 22%. Simultaneous deepening and widening of the groove by 40% had no significant impact on the strain level. Conclusion: Maintaining the width of the groove bottom while increasing the depth offers fewer advantages than deepening and narrowing the groove bottom.

Multistage implantology-orthodontic-prosthetic treatment: A case report.

BACKGROUND AND OVERVIEW: Patients increasingly expect esthetic and comfortable fixed restorations on implants, are aware how important it is to maintain healthy tooth tissue, and draw attention to the final result of treatment. CASE DESCRIPTION: In this case report, the authors describe implantology-orthodontic-prosthetic treatment provided on a patient who reported symptoms of head, back, and neck pain and had an impaired prosthetic plane, lack of space for prosthetic crowns after the introduction of the implants and no good treatment plan, and broken tooth roots of the mandibular anterior teeth. In addition, the patient wanted to correct the shape and color of the rest of her teeth. The authors present the different stages of the implantology-orthodontic-prosthetic treatment and the final result after treatment. The patient was satisfied with the achieved results of the treatment in terms of functionality and esthetics. She felt a significant reduction in pain in the temporal, masseter, and sternocleidomastoid muscles. The clenching of teeth at night decreased, and she began to sleep better. Her well-being improved. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Before the beginning of the treatment, dentists should make an accurate diagnosis and determine if patients qualify for the treatment and the appropriate materials are selected. Achieving the desired functional and esthetic effect often requires cooperation with physicians in various specialties and multistage treatment.

Effect of Air Abrasion on the Number of Particles Embedded in Zironia.

Background: Determination of the number of abrasive particles embedded in the zirconia surface after variable parameters of treatment. METHODS: One hundred thirty cylindrical disks made from zirconia were divided into 7 groups (n = 10): one control and six test groups treated by air abrasion using Al2O3 or SiC with grain sizes: 60, 110, 250 µm with a working pressure of 0.2 or 0.35 MPa. The SEM images were observed in BSE and BSE 3D. The chemical composition was determined by means of X-ray microanalysis with EDS. The surface was determined by quantitative metallography methods. Surfaces (%) depending on the particle type were compared using the Mann-Whitney test, depending on the pressure were compared using the Mann-Whitney test, and depending on the grain size were compared using the Kruskal-Wallis test as well as the Jonckheere-Terpstra trend test as well as the Dunn post-hoc testA probability. Value of p < 0.05 was deemed significant, while a p-value of p < 0.01 was regarded as highly significant. RESULTS: After blasting aluminium and silicon particles were embedded in zirconia surface. When blasted with Al2O3, the average amount of embedded grain was higher, while in the case of SiC. Highly significant differences were observed in the surface share of the abrasive depending on the grain size. At a pressure of 0.20 MPa the quantity of embedded abrasive amounted to 6.63, and at the pressure of 0.35 MPa rose to 7.17. Most particles of abrasive material became embedded when sandblasting with grain size 60 µm grain. No significant difference was observed in the surface share of the abrasive depending on the pressure. CONCLUSION: The quantity of embedded abrasive depends on its type and grain size, and the pressure applied.

Effect of hydrofluoric acid concentration and etching duration on select surface roughness parameters for zirconia.

STATEMENT OF PROBLEM: The surface of zirconia is resistant to chemical treatment. Roughening the surface of densely sintered zirconia still poses a challenge in dentistry. PURPOSE: The purpose of the study was to examine the effects of hydrofluoric acid on the quality of surface roughening of zirconia. MATERIAL AND METHODS: One hundred cylindrical disks made from zirconia (Ceramill Zi; Amann Girrbach AG) were divided into 4 groups. Three groups (n=30) were distinguished on the basis of hydrofluoric acid (HF) concentration: 40% HF, 9.5% HF, and 5% HF. The groups were then further divided into 3 groups of 10 specimens, each based on etch time (1, 5, or 15 minutes). The control group (n=10) consisted of specimens polished with SiC abrasive paper. The surface was examined with scanning electron microscopy, and the roughness was measured with a profilometer and confocal laser scanning microscope. The mean arithmetic profile deviation (Ra(mean)) and mean maximum height of profile (Rz(mean)) results for the etched surfaces in relationship to the baseline surfaces were compared with the Student t test for averaged data (α=.05). RESULTS: When etched with 40% HF concentration, the Ra(mean) and Rz(mean) results were statistically higher (P<.01) for the etched surfaces than for the baseline surfaces. When etched with 9.5% HF concentration, the higher Ra(mean) and Rz(mean) results were only statistically significant (P<.01) after 15 minutes. Etching with 5% HF concentration showed no significant differences (P>.05). CONCLUSIONS: Etching with a 5% HF solution should not be recommended as a method for roughening zirconia surfaces.