Dental luting agents: A review of the current literature

STATEMENT OF PROBLEM: The practice of fixed prosthodontic has changed dramatically with the introduction of innovative techniques and materials. Adhesive resin systems are examples of these changes that have led to the popularity of bonded ceramics and resin-retained fixed partial dentures. Today's dentist has the choice of a water-based luting agent (zinc phosphate, zinc polycarboxylate, glass ionomer, or reinforced zinc oxide-eugenol) or a resin system with or without an adhesive. Recent formulations of glass ionomer luting agents include resin components (resin-modified glass ionomers), which are increasingly popular in clinical practice. PURPOSE: This review summarizes the research on these systems with the goal of providing information that will help the reader choose the most suitable material. MATERIAL: The scientific studies have been evaluated in relation to the following categories: (1) biocompatibility, (2) caries or plaque inhibition, (3) microleakage, (4) strength and other mechanical properties, (5) solubility, (6) water sorption, (7) adhesion, (8) setting stresses, (9) wear resistance, (10) color stability, (11) radiopacity, (12) film thickness or viscosity, and (13) working and setting times. In addition, guidelines on luting-agent manipulation are related to available literature and include: (1) temporary cement removal, (2) smear layer removal, (3) powder/liquid ratio, (4) mixing temperature and speed, (5) seating force and vibration, and (6) moisture control. Tables of available products and their properties are also presented together with current recommendations by the authors with a rationale.     

Nucleus accumbens dopaminergic medication of fixed interval schedule-controlled behavior and its modulation by low-level lead exposure

To examine the assertion that changes in nucleus accumbens (NAC) dopamine (DA) activity serve as a mechanism of lead (Pb)-induced disruption of fixed interval (FI) schedule-controlled behavior, the effects of intra-NAC administration of the irreversible DA antagonist EEDQ (N-ethoxycarbonyl-2-ethoxy-1,2-dihyroquinoline) and of dopamine itself on FI performance were compared in rats that had been chronically exposed to 0, 50 or 500 ppm Pb acetate in drinking water from weaning. Pb exposure per se (500 ppm), as in past studies, increased FI response rates, primarily by shortening interresponse times. Although DA, which produced rate-dependent effects, increased FI rates at low doses in the 0 and 50 ppm groups, it did so by decreasing postreinforcement pause times. All DA doses decreased rates in the 500 ppm group. In contrast, the DA antagonist EEDQ suppressed FI response rates, effects that were not strongly rate dependent, by increasing both postreinforcement pause values and mean interresponse times. Pb exposure (500 ppm) delayed the recovery of response rates to control levels at the highest EEDQ dose, raising the possibility of a delay in receptor production rate. Collectively, these data suggest that NAC DA activity may be an important modulator of FI response rates. Enhanced NAC DA activity may contribute to Pb-associated increases in FI rates and may underlie the differential response of control and 500 ppm Pb-treated groups to intra-NAC DA administration. The different processes by which DA and Pb increase FI rates, however, suggests that additional mechanisms are operative in the case of Pb.     

Modeling semi-anechoic electromagnetic measurement chambers

Previous studies developed a model to predict theoretically the low-frequency plane-wave reflection coefficient of an array of pyramid cone absorbers such as those used to line anechoic electromagnetic measurement chambers. The present authors apply this model in a geometrical optics approach to predict the electromagnetic field in a chamber lined with cone absorbers in the frequency range of 30-300 MHz. The results are compared with site attenuation measurements for two actual semi-anechoic chambers     

The practice of science in the family.

Responds to comments by B. D. Forman (see record 1990-29006-001), S. A. Kirschner (see record 1990-29011-001), and M. Rohrbaugh (see record 1990-29019-001) on the present authors' (see record 1990-29009-001) work on the use of paradoxical interventions with couples. Focus is on (1) the subjectivist and objectivist research approach; (2) language, relationship, and content analysis; and (3) the relevancy of science to practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypertension in Haitians: results of a pilot survey of a public teaching hospital multispecialty clinic

Little is known about hypertension in Haitians. We performed a pilot survey of ambulatory Haitian patients in a multispecialty clinic at a large public teaching hospital. Approximately 10% of the clinic population was of Haitian origin. Clinical data were collected on 88 consecutive Haitian patients. Of these 88, 77 (87.5%) were hypertensive (SBP > or = 140 or DBP > or = 90 mm Hg or taking antihypertensive medication). The characteristics of the hypertensive patients were: age 54.1 +/- 13.0 (s.d.) years; 27 men, 50 women; 12/64 (19%) smoked; 7/63 (11%) used alcohol. Diabetes was present in 21/77 (27%). In patients for whom height and weight were available, obesity was present in 52%. Using JNC V criteria, 18 (23%) had Stage 1, 16 (21%) Stage 2, 18 (23%) Stage 3, and 25 (33%) Stage 4 hypertension. Despite 63/77 (82%) being treated for hypertension, only 20 (26%) were controlled (< 140/< 90 mm Hg). Of those under treatment, 29 were taking one drug; 18 (two drugs); 12 (three drugs); and four (four drugs). Target organ damage was evident in 37 (48%), including coronary artery disease (8), CHF (6), chronic renal failure (15), stroke (9), and LVH by ECG (19). There was evidence of severe noncompliance in 32 (42%). We conclude that in this clinic sample, hypertension was highly prevalent and unusually severe in terms of blood pressure (BP) level, refractoriness to treatment, and target organ consequences. Further studies are indicated.     

Attenuation of neomycin ototoxicity by iron chelation

Increasing evidence suggests that aminoglycoside ototoxicity is mediated by the formation of an aminoglycoside-iron complex and that the creation of this complex is a preliminary step in generation of free radical species and subsequent hair cell death. In this study we have assessed the ability of the iron chelator deferoxamine to attenuate the hearing loss induced by an ototoxic dose of the aminoglycoside neomycin (100 mg/kg per day for 14 days). Experiments were carried out on pigmented guinea pigs weighing 250 to 300 g. Changes in auditory sensitivity were characterized by monitoring shifts in compound action potential (CAP) thresholds, recorded through indwelling electrodes implanted at the round window, vertex, and contralateral mastoid. Results show that animals receiving neomycin alone suffered a mean threshold shift exceeding 35 dB at all test frequencies (2.0, 4.0, and 8.0 kHz) 30 days after initiation of treatment. In comparison, all animals receiving cotherapy of neomycin and deferoxamine (150 mg/kg twice daily for 14 days) maintained their CAP threshold, suggesting significant protection from neomycin ototoxicity. A statistical comparison of treatment groups showed that in the animals receiving cotherapy with neomycin and deferoxamine, deferoxamine produced a significant protective effect against neomycin-induced ototoxicity (P < 0.001). These results provide further evidence of the intrinsic role of iron in aminoglycoside ototoxicity and suggest that deferoxamine may have a therapeutic role in attenuating the cytotoxic action of aminoglycoside antibiotics.