Mechanical and electrothermal debonding: effect on ceramic veneers and dental pulp

This study compared the ability of three orthodontic debonding techniques for the removal of brackets from ceramic veneers without creating veneer damage. Three experimental groups included metal brackets debonded by either Howe pliers, lift off debonding instrument (LODI, 3M Unitek), or electrothermal debonder (ETD, "A" Company), as well as a group of electrothermally debonded ceramic brackets. It also evaluated and compared the intrapulpal temperature changes produced by electrothermal debonding metal and ceramic brackets. A sample of 95 extracted maxillary first premolars were prepared and restored with Mirage ceramic veneers (Chameleon Dental Products, Inc.). Veneer buccal surfaces were treated with 2.5% hydrofluoric acid, before silane application and bracket bonding with a no-mix resin. Specimens were thermocycled before debonding. All debonded specimens were examined under x20 magnification for veneer damage. A thermocouple was positioned at the pulp chamber buccal wall to record temperature increases (due to ETD activation) through a digital thermometer. Results suggest that ETD provides predictable debonding to ceramic brackets with no veneer damage and minimal risk to the pulp. Removal of metal brackets through electrothermal debonding produced ceramic damage in 13% of cases, and elevated temperatures beyond the threshold of irreversible pulpal damage (5.5 degrees C) in 46% of cases. Howe plier and LODI bracket removal are associated with ceramic damage incidence of 21% and 35%, respectively.

Randomised double-blind placebo-controlled study on adverse effects of rubella immunisation in seronegative women

BACKGROUND

The objective of our study was to investigate the association of adverse clinical musculoskeletal and neurological events in healthy postpartum women with live attenuated (RA27/3 strain) rubella-virus vaccine, and to assess the frequency of acute and recurrent arthralgia and arthritis and associations with acute and recurrent muscle pain (myalgia) and neurological manifestations (paraesthesias).

METHODS

We used a randomised placebo-controlled, double-blind design in a community setting. 636 women were enrolled and, after 90 women dropped out, 546 healthy women aged 18-41 years, who were rubella seronegative on routine screening were immunised parenterally with either monovalent live attenuated (RA27/3 strain) rubella vaccine (n = 270) or saline placebo (n = 276) in the postpartum period. Outcome measures were the occurrence of acute and persistent or recurrent joint manifestations (arthralgia or arthritis) at 1, 3, 6, 9, and 12 months after immunisation. Occurrence of muscle pain (myalgia), and neurological symptoms (paraesthesia) was also assessed at the same times.

FINDINGS

543 women completed 1-month follow-up. 456 women completed the 12-month assessment. There were no differences at the time of immunisation between rubella vaccine and placebo groups in distribution of age, ethnic origin, parity, time between delivery and immunisation, breastfeeding history, or histories of earlier rubella vaccination or joint complaints. Results indicated a significantly higher incidence (p = 0.006; odds ratio = 1.73 [95% CI = 1.17-2.57]) of acute joint manifestations in rubella-vaccine recipients (30%) than in placebo recipients (20%). Frequency of chronic (recurrent) arthralgia or arthritis was only marginally significant (p = 0.042; 1.58 [1.01-2.45]).

INTERPRETATION

RA27/3 rubella vaccine given to seronegative women during the postpartum period was significantly associated with development of acute arthralgia or arthritis. Although the numbers of women assessed and length of follow-up revealed only marginally significant differences in persistent or recurrent joint manifestations between rubella vaccine and placebo recipients, it is possible that susceptible women who are given rubella vaccination may experience this outcome.

A comparison of maximal bioenergetic enzyme activities obtained with commonly used homogenization techniques

Homogenization of tissue for analysis of bioenergetic enzyme activities is a common practice in studies examining metabolic properties of skeletal muscle adaptation to disease, aging, inactivity or exercise. While numerous homogenization techniques are in use today, limited information exists concerning the efficacy of specific homogenization protocols. Therefore, the purpose of this study was to compare the efficacy of four commonly used approaches to homogenizing skeletal muscle for analysis of bioenergetic enzyme activity. The maximal enzyme activity (Vmax) of citrate synthase (CS) and lactate dehydrogenase (LDH) were measured from homogenous muscle samples (N = 48 per homogenization technique) and used as indicators to determine which protocol had the highest efficacy. The homogenization techniques were: (1) glass-on-glass pestle; (2) a combination of a mechanical blender and a teflon pestle (Potter-Elvehjem); (3) a combination of the mechanical blender and a biological detergent; and (4) the combined use of a mechanical blender and a sonicator. The glass-on-glass pestle homogenization protocol produced significantly higher (P < 0.05) enzyme activities compared to all other protocols for both enzymes. Of the four protocols examined, the data demonstrate that the glass-on-glass pestle homogenization protocol is the technique of choice for studying bioenergetic enzyme activity in skeletal muscle.

Behavioral effects of naloxone on neuropeptide Y-induced feeding

We evaluated the effect of naloxone on neuropeptide Y (NPY)-induced feeding behavior using two methods; operant chambers and observational analysis. In the first study rats were trained on a FR 80 (first pellet) FR 3 (subsequent pellets) reinforcement schedule. Following training, rats were injected with NPY (intraventricular, 5 micrograms) and various doses of naloxone (subcutaneous, 0, 0.1, 0.3, 1, 3, and 10 mg/kg). NPY significantly increased the number of pellets consumed during the one hour session and naloxone (1, 3, and 10 mg/kg) blocked this effect. NPY failed to alter the time to the first response, but did decrease the time needed to complete the first ratio (FR 80). Naloxone (3 and 10 mg/kg) increased the latency to the first response and blocked NPY's effect on completion of the first ratio. In the second study, we observed rats continually following injection of saline. NPY (5 micrograms i.c.v.) and/or naloxone (1 mg/kg s.c.). NPY increased food intake during the 1-h session and naloxone blocked this effect. NPY decreased the latency to eat, but naloxone failed to significantly antagonize this effect. The amount of time spent eating was greater in the NPY group compared to the saline group and naloxone antagonized this effect. Lag sequential analysis indicated that NPY induced a move-eat-move behavioral sequence that disappeared following naloxone administration. These data lend support to the notion that opioids are involved in maintenance of NPY-induced feeding but affect meal initiation in a minor way. Only relatively high doses of naloxone (3 and 10 mg/kg) altered NPY-induced changes in meal initiation.

Potency of naloxone's anorectic effect in rats is dependent on diet preference

Modulation of feeding behavior by neuropeptide Y (NPY) and opioids is well established, but the possibility that these neural influences provoke specific appetites, NPY for carbohydrate and opioids for fat, has also been considered. In other studies, intake of standard chow after NPY stimulation can be blocked by naloxone, indicating an interaction between these systems in the regulation of feeding. The present experiments examined the nature of NPY-opioid interactions in diet selection. Rats were administered NPY and naloxone concurrently, then chose between high-fat and high-carbohydrate diets. Subcutaneous administration of naloxone (0.01-0.3 mg/kg) potently reduced intake of the preferred diet, but not the nonpreferred diet. A similar pattern of selection was seen in a separate experiment where the same doses of naloxone were administered after 24-h food deprivation. These data support the idea that the opioid system mediates the "rewarding" aspects of feeding.

Cost accounting of adult intensive care: methods and human and capital inputs

OBJECTIVE

To cost adult intensive care by determining inputs to production, resource consumption per patient, and total cost per intensive care unit (ICU) stay.

DESIGN

Prospective cost-accounting analysis of each patient stay in the ICU, over a 1-yr period.

SETTING

An 11-bed, medical/surgical adult ICU, in a 932-bad urban teaching hospital.

PATIENTS

All patients' admissions to an adult ICU over a 1-yr period, excluding those patients admitted solely for repeat hemodialysis.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Demographic information was collected, including age, gender, Acute Physiology and Chronic Health Evaluation (APACHE) II score, primary reason for ICU admission, operative (elective and emergency) and nonoperative status, ICU length of stay, and ICU outcome. Direct patient care costs were accounted to individual patients whose care generated those costs, and indirect patient care costs were averaged over all patients in the ICU on a daily basis. Costs were collected for human (nursing, medical, professional, and support staff) and capital (laboratory, diagnostic imaging, supplies, drugs, and equipment) resources. Cost information was available on 690 patients (43% female, 57% male). Cost/day/patient was $1,508 +/- 475 (1992 Canadian dollars) and the average cost per ICU stay was $7,520 +/- 11,606. Median cost/stay for all patients was $2,600. Cost per ICU stay was < $5,000 in 68% of patients, with an ICU survival rate of 85%. High cost was not a marker for poor survival. There was no relationship between age and cost categories. Across most diagnoses, cost/ day/patient was remarkably constant, approximating $1,500/day/ patient at existing labor rates.

CONCLUSIONS

In order to develop strategies aimed at cost containment, it is first necessary to undertake a thorough examination of cost drivers. This detailed cost-accounting study determined inputs to production, resources consumed by individual patients, and costs incurred during ICU stay.

Growth of microorganisms in propofol, thiopental, and a 1:1 mixture of propofol and thiopental

To assess and compare the growth of four microorganisms in solutions of intravenous anesthetics, known quanta of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were inoculated into propofol, thiopental, a 1:1 mixture of propofol and thiopental, and normal saline. All microorganisms were taken from standard stock cultures and incubated for 24 h (48 h for C. albicans). Growth of microorganism in each drug was compared by counting the number of colony forming units (CFUs) grown from a subculture of each inoculated anesthetic at 0, 3, 6, 12, and 24 h. The study shows that propofol strongly supports the growth of E. coli and C. albicans but is bacteriostatic toward S. aureus and weakly bactericidal toward P. aeruginosa. In contrast, both thiopental and the 1:1 mixture of propofol and thiopental behaved differently, exhibiting markedly bactericidal properties toward E. coli, S. aureus, and P. aeruginosa and a bacteriostatic effect on C. albicans. This finding supports recommendations that a strict aseptic technique should be used when handling propofol and that the contents of an ampoule should be used within 6 h of aspirating. The measured high pH of both thiopental and the 1:1 mixture of propofol and thiopental compared to propofol alone suggests pH to be a major factor in determining whether a given drug will support microbial growth.