A clinically focused discussion of luting materials.

A luting agent's primary function is to fill the minute void between an indirect restoration (definitive or provisional) and tooth (or implant abutment) and mechanically lock the restoration in place to prevent dislodgement during function. The purpose of this paper is to provide a clinically focused discussion on the broad spectrum of luting materials currently available to help the general practitioner make appropriate choices. Resins are typically formulated for a specific function or restoration and offer strength, aesthetics, flexible working times, and very low solubility yet are technique sensitive, expensive and often hard to clean-up. Glass-ionomers offer good strength and optical properties plus the potential for fluoride release/recharge but may have short working times, are sensitive to moisture or dehydration early on, and take time to fully set. Resin-modified glass-ionomers are hybrid, dual-phase materials which are manipulated like glass-ionomer but set quicker and are stronger. Zinc phosphate cement, used successfully for over a century to lute well-fitting metal and metal-ceramic definitive restorations, is a very inexpensive, rigid material which displays very high early compressive strength yet acidity and solubility can be problems. Polycarboxylate cement (a hybrid of zinc phosphate) has lower compressive strength but high tensile strength and may be less injurious to the pulp. Zinc oxide eugenol and zinc oxide non-eugenol cements typically have good sealing abilities but their relatively low compressive and tensile strengths, inherent brittleness, and high solubility limit usage to provisional restorations or implant supported crowns. Claims for multi-purpose or universal use by manufacturers can be somewhat confusing and overwhelming. Even so, the busy general practitioner must have sufficient knowledge to help choose an appropriate luting agent for each unique clinical situation.

Differentiating dental pulp cells via RGD-dendrimer conjugates.

Traumatic dental injuries are often irreversible, underscoring the need for therapies that protect dental pulp cells and enhance their regeneration. We hypothesized that generation 5 poly amido amine (PAMAM) dendrimers (G5), functionalized with fluorescein isothiocyanate (FL) and αVß3-specific, cyclic arginine-glycine-aspartic acid (RGD) peptides, will bind to dental pulp cells (DPCs) and modulate their differentiation. Dental pulp cells and mouse odontoblast-like cells (MDPC-23) (±) treated with G5-FL-RGD were analyzed via Western blot, RT-PCR, and quantitative PCR. Transcription of dental differentiation markers was as follows: Dentin matrix protein (DMP-1), dentin sialoprotein (DSPP), and matrix extracellular phosphoglycoprotein (MEPE) as well as vascular endothelial growth factor (VEGF) all increased via the JNK pathway. Long-term G5-RGD treatment of dental pulp cells resulted in enhanced mineralization as examined via Von Kossa assay, suggesting that PAMAM dendrimers conjugated to cyclic RGD peptides can increase the odontogenic potential of these cells.

Exercise and circulating cortisol levels: the intensity threshold effect.

This study examined the influence of exercise intensity upon the cortisol response of the hypothalamic-pituitary-adrenal (HPA) axis. Specifically, we examined exercise at intensities of 40, 60, and 80% maximal oxygen uptake (VO2max) in an attempt to determine the intensity necessary to provoke an increase in circulating cortisol. Twelve active moderately trained men performed 30 min of exercise at intensities of 40, 60, and 80% of their VO2max, as well as a 30-min resting-control session involving no exercise on separate days. Confounding factors such as time of day--circadian rhythms, prior diet--activity patterns, psychological stress, and levels of exercise training were controlled. Cortisol and ACTH were assessed in blood collected immediately before (pre-) and after (post-) each experimental session. Statistical analysis involved repeated measures analysis of variance and Tukey post-hoc testing. The percent change in cortisol from pre- to post-sampling at each session was: resting-control, 40, 60, and 80% sessions (mean+/-SD) =-6.6+/-3.5%, +5.7+/-11.0%, +39.9+/-11.8%, and +83.1+/-18.5%, respectively. The 60% and 80% intensity magnitude of change was significantly greater than in the other sessions, as well as from one to another. The ACTH responses mirrored those of cortisol, but only the 80% exercise provoked a significant (p<0.05) increase pre- to post-exercise. The calculated changes in plasma volume for the resting-control, 40%, 60%, and 80% sessions were: +2.2+/-3.0%, -9.9+/-5.0%, -15.6+/-3.5%, and -17.2+/-3.3%, respectively. Collectively, the cortisol findings support the view that moderate to high intensity exercise provokes increases in circulating cortisol levels. These increases seem due to a combination of hemoconcentration and HPA axis stimulus (ACTH). In contrast, low intensity exercise (40%) does not result in significant increases in cortisol levels, but, once corrections for plasma volume reduction occurred and circadian factors were examined, low intensity exercise actually resulted in a reduction in circulating cortisol levels.

Nosocomial infective endocarditis: should the definition be extended to 6 months after discharge.

Because the microbiology and patient population of infective endocarditis (IE) have evolved, the traditional definition of nosocomial IE may require revision. The question of whether this definition should be extended to 6 months after discharge was explored, and a high rate of episodes with nosocomial pathogens (coagulase-negative staphylococci) and a low rate of episodes with community pathogens (streptococci) in the extended nosocomial group were found. Therefore, modification of the traditional definition is proposed, distinguishing between early (as traditionally described) and late nosocomial IE (IE in association with a significant invasive procedure performed during a hospitalization between 8 weeks and 6 months before the onset of symptoms).

Methicillin-resistant versus methicillin-sensitive Staphylococcus aureus infective endocarditis.

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infective endocarditis (IE) is increasing. This study compared clinical characteristics and mortality in patients with methicillin-sensitive S. aureus (MSSA) IE versus MRSA IE, based on a prospectively collected series of 72 consecutive patients with definite S. aureus IE according to the modified Duke criteria between June 2000 and December 2006. Sixteen of 72 IE patients (22%) were caused by MRSA. Nosocomial origin, surgical site infection, surgery in the previous 6 months, the presence of a catheter and persistent bacteremia were significantly associated with MRSA. MSSA patients had significantly more unknown origin of bacteremia and experienced a significantly higher rate of major embolism than MRSA patients. MSSA patients underwent more frequently combined surgical and antimicrobial therapy, and MRSA patients were treated more frequently with antimicrobial therapy due to a contraindication to surgery. The 6-month mortality was higher in patients with MRSA than MSSA. In the MSSA group treated with antimicrobial therapy without an indication to surgery, all patients survived, and in the combined surgical and antimicrobial group 29% died. The mortality in MRSA patients was lowest if combined surgical and antimicrobial therapy was performed. Both in MSSA and MRSA patients with antimicrobial therapy due to a contraindication to surgery, the mortality was extremely high. These data suggest that in S. aureus IE patients with a nosocomial origin, the presence of a catheter or recent surgery, initial therapy should include antimicrobial agents active against MRSA. Antimicrobial therapy alone with close monitoring of the therapeutic effect and signs of complicated course is an acceptable approach in selected patients with MSSA IE. Denial of surgery because of local or general factors in patients that meet criteria for surgical intervention in acute IE is prognostically ominous.

Evolving trends in infective endocarditis.

Infective endocarditis is a microbial infection of the endocardial surface and, despite improvements in diagnostic accuracy, medical therapy and surgical techniques, mortality remains high. This review focuses on changes in epidemiology, microbiology and diagnosis, as well as changes in medical and surgical management of infective endocarditis affecting native and prosthetic valves in adults, that have evolved during the past two decades. Significant changes have included an increasing involvement of prosthetic valves and nosocomially-acquired disease, an increased involvement of staphylococci as the causative agents, and a recognition that elderly individuals with degenerative valvular disease are the most vulnerable population. Topics still requiring study include whether and when valve replacement should be performed, and how to predict perivalvular complications or embolisation based on echocardiography findings. Optimisation of antimicrobial treatment schemes (choice of the antibiotic, dose and duration) also requires further investigation.

Craniofacial tissue engineering.

There is substantial need for the replacement of tissues in the craniofacial complex due to congenital defects, disease, and injury. The field of tissue engineering, through the application of engineering and biological principles, has the potential to create functional replacements for damaged or pathologic tissues. Three main approaches to tissue engineering have been pursued: conduction, induction by bioactive factors, and cell transplantation. These approaches will be reviewed as they have been applied to key tissues in the craniofacial region. While many obstacles must still be overcome prior to the successful clinical restoration of tissues such as skeletal muscle and the salivary glands, significant progress has been achieved in the development of several tissue equivalents, including skin, bone, and cartilage. The combined technologies of gene therapy and drug delivery with cell transplantation will continue to increase treatment options for craniofacial cosmetic and functional restoration.

Circadian immune measures in healthy volunteers: relationship to hypothalamic-pituitary-adrenal axis hormones and sympathetic neurotransmitters.

OBJECTIVE: The purpose of this study is to examine the circadian pattern of specific immunologic measures and to compare observed circadian rhythms of these measures with the well-established circadian rhythms of hypothalamic-pituitary-adrenal axis hormones and sympathetic neurotransmitters. METHODS: Blood samples were collected every 2 hours for a total of 24 hours from nine healthy volunteers. The blood samples were assayed for hormones and immune measures, including adrenocorticotropic hormone (ACTH), cortisol, norepinephrine, and epinephrine. The immune measures included percentage and absolute number of neutrophils, lymphocytes, the lymphocyte subsets CD3+ (T cells), CD4+ (T helper/inducer), CD8+ (T suppressor/cytotoxic), CD56+ (natural killer [NK] cells) and NK cell activity (NKCA). RESULTS: The following immune measures exhibited a significant circadian rhythm: the percentages of neutrophils, CD4+ cells, and CD56+ cells; the absolute numbers of total lymphocytes, CD3+ cells, CD4+ cells, and CD8+ cells; and NKCA. Cross-correlations between the circadian rhythms of selected hormones and immune measures indicated a strong inverse association between the circadian rhythms of cortisol and the different T cell subsets on the one hand, and a strong direct association between the rhythms of cortisol and the percentage of CD56+ and NKCA on the other. Cross-correlations involving the circadian rhythms of norepinephrine and the same immune measures were in general much weaker and statistically nonsignificant. CONCLUSION: In healthy individuals, both enumerative and functional immune measures exhibit circadian rhythms that seem to be associated most closely with the circadian rhythm of cortisol.

Kong toys for laboratory primates: are they really an enrichment or just fomites?

Simple toys as enrichment devices have been associated with a rapid decline in their use by nonhuman primates. Other facets of toy presentation have not been described previously. For example, a comparison of the effect(s) of an enrichment device between two facilities should be validated if enrichment recommendations are to be made that affect diverse research facilities across the country. Additionally, a comparison of two methods of presentation (one highly accessible to the animal and the other less accessible) of the same enrichment device for potential differences in efficacy could provide direction in implementing an enrichment program based on simple toys. The handling of enrichment devices by nonhuman primates can lead to the spread of microbial contamination. The typical enrichment program rotates enrichment devices among animals to maximize the variety of stimuli available to each primate in the most economic manner. An adequate sanitation program is therefore pivotal to minimizing the potential for enrichment devices to be fomites. We conducted three experiments that addressed these issues. The results confirmed that, although the presence of a simple toy reduced behavioral pathology, there was variability in behavioral effect for an enrichment technique between facilities. Two methods of presentation (on floor and suspended) of a simple toy did not produce any significant differences in use. Finally, we demonstrated that microbial growth can persist on enrichment devices after they have been sanitized in a commercial cagewasher.

The incorporation of(14)C-glycerol into different species of diglycerides and triglycerides in rat liver slices.

The relative rates of de novo synthesis of species of diglycerides and triglycerides from(14)C-glycerol were examined in rat liver slices. Diglycerides containing one or two double bonds per molecule and triglycerides containing four or more double bonds per molecule represented 70% and 60% respectively of the newly synthesized diglycerides and triglycerides. The newly synthesized triglycerides were more unsaturated than the endogenous triglycerides. Our results suggest that a nonrandom synthesis of species of diglycerides occurred followed by an almost random utilization of the various diglyceride species for the biosynthesis of triglycerides.