Hydroxyapatite (HA) from bovine bones has been used as a biomaterial in dentistry due to its biocompatibility and bioactivity. However, dense HA bioceramics still present inadequate properties for ...applications that require high mechanical performance, such as infrastructure. Microstructural reinforcements and control of ceramic processing steps are methods to improve these shortcomings. The present study assessed the effects of polyvinyl butyral (PVB) addition in combination with two sintering methodologies (2-step and conventional), on the mechanical properties of polycrystalline bovine HA bioceramics. The samples were divided into four groups (with 15 samples per group): conventional sintering with binder (HBC) and without binder (HWC) and 2-step sintering with (HB2) and without binder (HW2). HA was extracted from bovine bones, turned into nanoparticles in a ball mill, and subjected to uniaxial and isostatic pressing into discs, according to ISO 6872 standards. All groups were characterized by x-ray diffractometry (XRD), differential thermal analysis (DTA) and Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and relative density. Besides, mechanical analyses (biaxial flexural strength (BFS) and modulus of elasticity) were also performed. The characterization results demonstrated that adding agglutinants or the sintering method did not affect HA's chemical and structural characteristics. Even so, the HWC group showed the highest mechanical values for BFS and modulus of elasticity being 109.0 (98.0; 117.0) MPa and 105.17 ± 14.65 GPa, respectively. The HA ceramics submitted to conventional sintering and without the addition of binders achieved better mechanical properties than the other groups. The impacts of each variable were discussed and correlated to the final microstructures and mechanical properties.
Summary The aim of this study was to determine the prevalence of signs and symptoms of temporomandibular disorders (TMD) and otologic symptoms in patients with and without tinnitus. The influence of ...the level of depression was also addressed. The tinnitus group was comprised of 100 patients with tinnitus, and control group was comprised of 100 individuals without tinnitus. All subjects were evaluated using the research diagnostic criteria for temporomandibular disorders (RDC/TMD) to determine the presence of TMD and depression level. Chi‐square, Spearman Correlation and Mann‐Whitney tests were used in statistical analysis, with a 5% significance level. TMD signs and symptoms were detected in 85% of patients with tinnitus and in 55% of controls (P ≤ 0·001). The severity of pain and higher depression levels were positively associated with tinnitus (P ≤ 0·001). It was concluded that tinnitus is associated with TMD and with otalgia, dizziness/vertigo, stuffy sensations, hypoacusis sensation and hyperacusis, as well as with higher depression levels.
This study evaluated the five-year clinical performance of ceramic inlays and onlays made with two systems: sintered Duceram (Dentsply-Degussa) and pressable IPS Empress (Ivoclar Vivadent). ...Eighty-six restorations were placed by a single operator in 35 patients with a median age of 33 years. The restorations were cemented with dual-cured resin cement (Variolink II, Ivoclar Vivadent) and Syntac Classic adhesive under rubber dam. The evaluations were conducted by two independent investigators at baseline, and at one, two, three, and five years using the modified United States Public Health Service (USPHS) criteria. At the five-year recall, 26 patients were evaluated (74.28%), totalling 62 (72.09%) restorations. Four IPS restorations were fractured, two restorations presented secondary caries (one from IPS and one from Duceram), and two restorations showed unacceptable defects at the restoration margin and needed replacement (one restoration from each ceramic system). A general success rate of 87% was recorded. The Fisher exact test revealed no significant difference between Duceram and IPS Empress ceramic systems for all aspects evaluated at different recall appointments (p>0.05). The McNemar chi-square test showed significant differences in relation to marginal discoloration, marginal integrity, and surface texture between the baseline and five-year recall for both systems (p<0.001), with an increased percentage of Bravo scores. However, few Charlie or Delta scores were attributed to these restorations. In conclusion, these two types of ceramic materials demonstrated acceptable clinical performance after five years.
According to the literature, the occurrence of dysphagia is high in cases of stroke, and its severity can be enhanced by loss of teeth and the use of poorly fitting prostheses.
To verify that the ...status of oral health influences the level of oral intake and the degree of swallowing dysfunction in elderly patients with stroke in chronic phase.
Thirty elderly individuals affected by stroke in chronic phase participated. All subjects underwent assessment of their oral condition, with classification from the Functional Oral Intake Scale (FOIS) and nasoendoscopic swallowing assessment to classify the degree of dysphagia. The statistical analysis examined a heterogeneous group (HG, n=30) and two groups designated by the affected body part, right (RHG, n=8) and left (LHG, n=11), excluding totally dentate or edentulous individuals without rehabilitation with more than one episode of stroke.
There was a negative correlation between the need for replacement prostheses and the FOIS scale for the HG (P=0.02) and RHG (P=0.01). Differences in FOIS between types of prostheses of the upper dental arch in the LHG (P=0.01) and lower dental arch in the RHG (P=0.04). A negative correlation was found between the number of teeth present and the degree of dysfunction in swallowing liquid in the LHG (P=0.05). There were differences in the performance in swallowing solids between individuals without prosthesis and those with partial prosthesis in the inferior dental arch (P=0.04) for the HG.
The need for replacement prostheses, type of prostheses, and the number of teeth of elderly patients poststroke in chronic phase showed an association with the level of oral intake and the degree of oropharyngeal dysphagia.
This work aimed to analyze the micro shear bond strength of ceramic and dental substrates to Multilink® Speed self-adhesive/curing resin cement (Ivoclar Vivadent, Schaan, Liechtenstein).
The groups ...were composed of (1) ceramic/cement interfaces: LD - Lithium Disilicate (IPS e.max CAD®); ZLS - Zirconia-reinforced lithium silicate (Celtra Duo®); Y-TZP MO – Medium Opacity Yttria-stabilized tetragonal zirconia polycrystal (IPS ZirCAD MO®); Y-TZP T - Translucency yttria-stabilized tetragonal polycrystal (IPS ZirCAD MT®), and by (2) cement/dental interfaces (enamel or dentin): E + E – selective phosphoric acid etching enamel; E - unetched enamel; Dentin - middle dentin. Ceramic blocks were sectioned into 2mm thick slices in a cutting machine with a diamond disc under cooling, followed by standardized polishing, crystallization or sintering, PVC inclusion, final polishing, and surface treatments according to each ceramic composition (n=20). Teeth slices (2mm thick) were obtained from human third molars, PVC included, followed by polishing. The cement cylinders (Ø = 1.4; height = 1.0) were bonded to substrates, following the manufacturer's instructions. The specimens were stored in deionized water at 37°C for 24h and subjected to the micro shear bond strength test. Data were submitted to statistical analysis using the Kruskal-Wallis and Dunn tests. Failure types were classified as adhesive, cohesive, and mixed, with a representative specimen of each failure submitted to a scanning electron microscope (SEM). Weibull statistical analysis was performed to obtain the following metrics: the probability of failure, Weibull modulus (m) (reliability), and characteristic strength (σ0).
The E + E group showed the highest median value, lower probability of failure, higher reliability, and higher characteristic strength among all the evaluated groups, with significant similarity to the ZLS and LD groups and a statistically significant difference to the other dental substrates. E and Dentin showed the lowest medians among all substrate types. The Glass-ceramics the ZLS showed high characteristic strength and the LD showed greater reliability. The adhesive failure mode was predominant among the failure types.
Glass-ceramics showed higher characteristic strength, lower probability of failure, and greater reliability, being similar to selectively etched enamel.
We demonstrate that multiply coupled spinor polariton condensates can be optically tuned through a sequence of spin-ordered phases by changing the coupling strength between nearest neighbors. For ...closed four-condensate chains these phases span from ferromagnetic (FM) to antiferromagnetic (AFM), separated by an unexpected crossover phase. This crossover phase is composed of alternating FM-AFM bonds. For larger eight-condensate chains, we show the critical role of spatial inhomogeneities and demonstrate a scheme to overcome them and prepare any desired spin state. Our observations thus demonstrate a fully controllable nonequilibrium spin lattice.
Hydroxyapatite (HA) from bovine bone structure has high importance among biomaterials due to its biocompatibility, bioactivity and its sustainable renewable source. However, pure dense HA bioceramics ...still present poor mechanical properties when used in a dense form to be applied as an implant or restoration material. Thus, this study aimed to characterize the thermal behavior of pure bovine HA powder as well as evaluate its behavior when subjected to two sintering methodologies.
Therefore, HA was extracted from bovine bones, turned into nanoparticles in a ball mill and subjected to uniaxial and isostatic pressing into discs, according to the ISO 6872 standard. Two sintering methodologies were used: 1) conventional curve (HA/Conv), in a single curve with a maximum temperature peak of 1300 °C and slow cooling to room temperature; and 2) 2-step curve (HA/2step) with a maximum peak of 950 °C with rapid cooling to 880°C and subsequent slow cooling to room temperature. The nanoparticulate powder was subjected to differential thermal analysis (DTA), dilatometry and x-ray diffractometry (XRD). The sintered samples of both groups were characterized by XRD, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) relative density and biaxial flexural strength.
The dilatometric curve shows the beginning of the sintering process at 1050 °C. In the DTA analysis it was possible to observe a gain in mass in about 650 °C with subsequent loss of part of the acquired mass until reaching a temperature of 1000 °C. The XRD analysis demonstrates the classic crystallographic peaks both before and after the sintering process by the two groups, showing no change in the crystalline characteristic. The FTIR spectrum demonstrated the classical bands of HA-related bonds. The HA/Conv group obtained statistically higher values of relative density (2.92g/cm3) and in flexural strength (109MPa) (p<0.05). The results of the HA/2step group (2.08g/cm3; 25.7MPa) are justified by the SEM images that demonstrate greater porosity and less cohesion between the ceramic grains.
It was possible to conclude that the HA bioceramics submitted to temperatures above 1000 °C, can reach a higher degree of sintering and densification, thus optimizing its mechanical properties.
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