Comparative analysis of self-cure and dual cure-dental composites on their physico-mechanical behaviour.

BACKGROUND: Clinical practitioners may have become familiar with the rapid transformation of dental composites. However, they may not scientifically understand the factors influencing the mechanical and physical properties. Scientific knowledge of filler-resin interaction can significantly improve clinical understanding of resin composites. Several independent studies have examined the mechanical and physico-mechanical properties of dental resin composites; however, no comprehensive study has examined the influence of fillers and resin materials on the physico-mechanical properties of both self-cure and dual-cure composites. METHODS: This study performed investigations on the physico-mechanical behaviour of four commercially available dual-cure dental composites (Bioactive, Fill Up!, Surefil One, Cention N) and two commercially available self-cure dental composites (Stela Capsule and Stela Automix). Test specimens for flexural and compressive strength, microhardness, fracture toughness, and hydrolytic behaviour were prepared and tested as per respective standards. The data sets were statistically analysed using one-way ANOVA and Tukey's post-hoc comparison. RESULTS: There was a substantial variation in flexural strength and modulus values in this study, ranging from 32.0 to 113.4 MPa and 2.36 to 12.07 GPa, respectively. Similarly, there were significant differences in compressive strength between the materials in this study, ranging from 119.3 to 223.5 MPa. The highest fracture toughness value was found to be 1.41 MPa.m0.5, while the lowest value was 0.43 MPa.m0.5. Variations in surface microhardness were significant (24.11-68.0 N/mm2), which correlated with the filler content. Water sorption and solubility demonstrated high variations among materials, with Surefil One exceeding ISO 4049 thresholds significantly. CONCLUSIONS: A linear correlation can be established between surface microhardness (HV) and flexural and compressive moduli, as well as filler content (wt.%). However, both flexural and compressive strengths are impacted by the resin's constituent monomers and the resin-filler matrix's cross-linking capability. Additionally, factors such as filler size, shape, and the cross-linking ability of the resin-filler matrix play a crucial role in fracture toughness and the propagation of cracks within the restoration. Also, resin monomers and filler particle size affect the hydrolytic degradation characteristics of composites, which can also affect their mechanical properties. © 2023 Australian Dental Association.

Tissue distribution of three members of the murine protein disulfide isomerase (PDI) family.

The distribution of PDI, ERp61 and ERp72, members of the protein disulfide isomerase (PDI) family of endoplasmic reticulum (ER) proteins, was determined in various murine tissues. Relative amounts of mRNA were measured using a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. Protein levels were determined from Western blots. In most tissues, protein levels paralleled the amount of mRNA for each PDI family member. The tissue distribution of the PDI and ERp72 mRNAs was similar, although ERp72 was not as abundant as PDI in the tissues. The tissue distribution of the ERp61 mRNA was significantly different from the two other family members. To help define potential hormonal or maturational differences in the regulation of expression of PDI family members, mRNA was measured in the frontal cortex, liver, pituitary gland and uterus at timed intervals during postnatal maturation. Except in the pituitary gland, the mRNA levels at 10 days and 22 days after birth were essentially identical to those in the adult. The ERp61 and ERp72 mRNAs were present at 2- to 3-fold higher levels in the pituitary glands of the 10- and 22-day-old mice, than in the adult mice. In addition, the pituitary gland PDI mRNA was 2- to 3-fold higher in 10-day-old mice than in adults. In general, levels of PDI family members were higher in secretory tissues than in other tissues in both immature and adult mice.

Mousepox outbreak in a laboratory mouse colony.

Mousepox was diagnosed in and eradicated from a laboratory mouse colony at the Naval Medical Research Institute. The outbreak began with increased mortality in a single room; subsequently, small numbers of animals in separate cages in other rooms were involved. Signs of disease were often mild, and overall mortality was low; BALB/cByJ mice were more severely affected, and many of them died spontaneously. Conjunctivitis was the most common clinical sign of disease in addition to occasional small, crusty scabs on sparsely haired or hairless areas of skin. Necropsy findings included conjunctivitis, enlarged spleen, and pale liver. Hemorrhage into the pyloric region of the stomach and proximal portion of the small intestine was observed in experimentally infected animals. In immune competent and immune deficient mice, the most common histologic finding was multifocal to coalescing splenic necrosis; necrosis was seen less frequently in liver, lymph nodes, and Peyer's patches. Necrosis was rarely observed in ovary, vagina, uterus, colon, or lung. Splenic necrosis often involved over 50% of the examined tissue, including white and red pulp. Hepatic necrosis was evident as either large, well-demarcated areas of coagulative necrosis or as multiple, random, interlacing bands of necrosis. Intracytoplasmic eosinophilic inclusion bodies were seen in conjunctival mucosae and haired palpebra. Ectromelia virus was confirmed as the causative agent of the epizootic by electron microscopy, immunohistochemistry, animal inoculations, serologic testing, virus isolation, and polymerase chain reaction. Serologic testing was of little value in the initial stages of the outbreak, although 6 weeks later, orthopoxvirus-specific antibody was detected in colony mice by indirect fluorescent antibody and enzyme-linked immunosorbent assay procedures. The outbreak originated from injection of mice with a contaminated, commercially produced, pooled mouse serum. The most relevant concern may be the unknown location of the source of the virus and the presence of a reservoir for this virus within the United States.

Gastric invasion by Trypanosoma cruzi and induction of protective mucosal immune responses.

Trypanosoma cruzi is an intracellular parasite transmitted from a reduviid insect vector to humans by exposure of mucosal surfaces to infected insect excreta. We have used an oral challenge murine model that mimics vector-borne transmission to study T. cruzi mucosal infection. Although gastric secretions have microbicidal activity against most infectious pathogens, we demonstrate that T. cruzi can invade and replicate in the gastric mucosal epithelium. In addition, gastric mucosal invasion appears to be the unique portal of entry for systemic T. cruzi infection after oral challenge. The mucosal immune responses stimulated by T. cruzi gastric infection are protective against a secondary mucosal parasite challenge. This protective mucosal immunity is associated with increased numbers of lymphocytes that secrete parasite-specific immunoglobulin A. Our results document the first example of systemic microbial invasion through gastric mucosa and suggest the feasibility of a mucosal vaccine designed to prevent infection with this important human pathogen.

Experimental nasal dermatitis in the Mongolian gerbil: effect of bilateral harderian gland adenectomy on development of facial lesions.

Two groups of adult Mongolian gerbils (Meriones unguiculatus) of mixed ages and sex were used to study the effect of bilateral Harderian gland adenectomy on development of nasal dermatitis. One group of gerbils underwent bilateral Harderian gland adenectomies, while the other group underwent sham surgeries, leaving the Harderian gland intact. All animals in both groups were fitted with Elizabethian collars to prevent self-grooming, allowing a buildup of nasolacrimal or Harderian gland secretions near the medial canthus of the eye and at the external nares. Twenty-six of 27 animals with intact Harderian glands developed nasal and facial lesions within 20 days. None of the 27 Harderian gland adenectomized animals developed nasal or facial lesions. Apparently, accumulation of Harderian gland secretions is involved in the pathogenesis of nasal dermatitis in the Mongolian gerbil.

Husbandry and medicine of small rodents.

Biology, physiology, husbandry, and commonly occurring diseases of small rodent pets, including the Syrian hamster, Mongolian gerbil, rat, and mouse, are presented.

A computer based system for collection, storage, retrieval and reporting accession information in a veterinary medical diagnostic laboratory.

Substantial data collected from large numbers of accessions, the need for comprehensive reporting of negative as well as positive laboratory findings, and the necessity for obtaining rapid diagnostic correlations prompted the development of a computer based system of accession data management for collection, storage, rapid retrieval, reporting, concording, and administrative compiling in a state-university Veterinary Medical Diagnostic Laboratory.

Nonenzymatic glycosylation of low density lipoproteins in vitro. Effects on cell-interactive properties.

Atherosclerosis occurs at an accelerated rate in patients with diabetes mellitus. Since some proteins undergo nonenzymatic glycosylation in diabetic patients and because certain chemical modifications of low density lipoproteins produced alterations in their interactions with certain cultured cells, a fact that may be relevant to atherogenesis, we investigated the effect of in vitro glycosylation on cell-related properties of low density lipoproteins. Glycosylation was carried out by incubating LDL (1-10 mg LDL-protein/ml) with glucose (0-100 mM) in 0.5 M phosphate buffer, pH 8.0, at 37 degrees C. The amount of glucose incorporated into LDL after 1-2 wk of incubation was estimated to be in the range of 1-10 mol/mol LDL-protein. Amino acid analysis of glycosylated LDL showed that glucose was covalently bound to lysine residues. In studies with cultured human fibroblasts, glycosylated LDL was internalized and degraded significantly less than control LDL, in proportion to the estimated degree of glycosylation (12% of control for the most extensively glycosylated LDL). Glycosylation of LDL also impaired significantly its ability to stimulate cholesteryl ester synthesis by cultured fibroblasts. Glycosylated LDL did not stimulate cholesteryl ester synthesis in rat peritoneal macrophages. If glycosylation of LDL occurs in diabetic patients, some pathophysiologic consequences related to the increased incidence of atherosclerosis in these patients may result.

The visual world behind the head.

After a 5-minute inspection of 7 objects laid out on a shelf, subjects were seated with the objects behind them and answered questions about the locations and orientations of objects by throwing a switch left or right. The "visual image" subjects were told to imagine that the objects were still in front of them and to respond accordingly. The "real space" (RS) subjects were told to respond in terms of the positions of the objects in real space behind them. Thus correct responses (left vs. right) were completely opposite for the 2 groups. A control group responded while facing a curtain concealing the objects. The task was harder, by time and error criteria, for group RS than for the other 2 groups, but not dramatically so. All RS subjects denied using a response-reversal strategy. Some reported translating the objects from back to front and thus responding as to a mirror-image of the array. When this evasion was discouraged, RS subjects typically reported responding in terms of visual images located behind them and viewed as if by "eyes in the back of the head." The paradox of a visual image that corresponds to no possible visual input is discussed.