Biomedical subjects
M Grace
Publications and source records attributed to M Grace.
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Shear/peel bond strength of repositioned ceramic brackets.
Improper orthodontic bracket position may necessitate bracket removal and rebonding to establish correct bracket position. This procedure is necessary to use efficient orthodontic mechanics. The purpose of the study was to investigate (1) the amount of bonding resin remaining on single crystal bracket bases following electrothermal debonding, and (2) the bond strength of rebonded single crystal ceramic brackets under different treatment conditions. The bases of debonded, single crystal ceramic brackets (n = 100) were inspected for resin, classified with an adaptation of the adhesive remnant index (ARI), and evenly assigned to four experimental groups (n = 25). Groups were (1) silane coupling agent, (2) heat plus silane coupling agent, (3) hydrofluoric acid plus silane coupling agent, and (4) heat plus hydrofluoric acid plus silane coupling agent. An additional group of brackets not previously bonded was used as the control (n = 25). The brackets were bonded to 125 fresh bovine teeth. A force was applied 1 mm from the bracket-resin interface by a testing machine. The force measured in this experiment was shear/peel and the ratio of shear to peel was 0.53. The AI index showed 79% of the brackets had no resin on their bases. The shear/peel bond strnegth was significantly greater for the control group than all other groups (P < 0.01). Treatment of electrothermally debonded ceramic brackets with silane or heat plus silane resulted in bond strength greater than 9 MPa. The use of hydrofluoric acid significantly reduced the bond strength below 2 MPa.
Quality of life measures before and one year after admission to an intensive care unit.
OBJECTIVE: To assess outcome of patients admitted to an intensive care unit (ICU), using a prospective 1-yr follow-up, with special emphasis on various quality of life measures before and after admission to the ICU. DESIGN: Prospective comparison of quality of life before and 1 yr after admission to the ICU. SETTING: Eleven-bed adult medical/surgical ICU. PATIENTS: All patients admitted to the ICU over a 1-yr period were eligible for inclusion in this study. Repeat admissions were enrolled only on first admission. Patients < 17 yrs of age and those patients who died within 24 hrs of admission were excluded. INTERVENTIONS: Quality of life measures were collected before and 6 and 12 months after ICU admission. MEASUREMENTS AND MAIN RESULTS: The following data were collected: duration of ICU and hospital stay; ICU, hospital, 6- and 12-month mortality; quality of life (level of activity, activities of daily living, perceived health, support, and outlook on life) and place of residence at baseline and 12 months after ICU admission. There were 504 patients who met the study criteria; age 55 +/- 20 yrs (median 59), 229 female and 275 male. Mean ICU length of stay was 4.3 +/- 7.4 days. Hospital length of stay was 31 +/- 41 days. Acute Physiology and Chronic Health Evaluation II (APACHE II) score was 14 +/- 7. Cumulative mortality: ICU 5.4%, hospital 13.5%, 6 month 20.6%, and 12 month 25%. One year quality of life questionnaires were completed for 293 patients. Relative to baseline, there was a decrease in the level of activity and activities of daily living at 12 months (p < .01). Perceived health status increased over the year for patients > or = 75 yrs of age (p < .01). There was no difference in the level of support from family or friends, or outlook on life, at 12 months. At 1 yr, 262 (89%) patients were living at home. CONCLUSION: Patients admitted to intensive care tend to have a decrease in the level of activity and activities of daily living 1 yr after their ICU stay, although in the very elderly, perceived health status increases. As well, the majority (89%) of patients return home.
Naloxone blocks that portion of feeding driven by sweet taste in food-restricted rats.
We evaluated the potency of naloxone on intake of normal and sweet chow in food-deprived and schedule-fed rats. We found that naloxone's anorectic potency was dependent on the type of chow presented to the rats and the deprivation schedule utilized to stimulate food intake. In 24-h and 48-h deprived rats, naloxone decreased intake of normal rat chow at doses ranging from 0.3 to 3 mg/kg. In chronically deprived rats (80% of normal body wt), these doses of naloxone failed to decrease intake of normal chow. Rats eating sweet chow ate more when energy deprived and were more sensitive than rats eating normal chow to naloxone-induced limitations in food intake, both in acute and chronic food-deprived groups. Thus naloxone decreased intake of sweet chow much more effectively than normal chow even when rats were chronically food deprived. We also found that an extremely low dose of naloxone (0.03 mg/kg) decreased intake of sweet chow by almost 50% in satiated rats.
Pharmacological and morphological effects of in vitro transluminal balloon angioplasty on normal and vasospastic canine basilar arteries.
Despite growing clinical use of transluminal balloon angioplasty (TBA) to treat cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH), the precise mechanism of action of balloon dilation on the cerebral arterial wall is unknown. In this experiment the authors examined the pharmacological and morphological changes in 10 normal and 12 vasospastic canine basilar arteries following in vitro silicone microballoon TBA. For the SAH group in which the double-hemorrhage model was used, vasospasm was confirmed by angiography and the animals were killed on Day 7 after the first SAH. In vitro TBA was performed on basilar arteries from normal and SAH dogs immediately after sacrifice and removal of the brain. The procedure was performed while the arteries were maintained in oxygenated Krebs buffer. In the pharmacological studies, potassium chloride, prostaglandin F2 alpha, serotonin, and noradrenaline were used as vasoconstrictors, and bradykinin and calcium ionophore A23187 were used to produce an endothelium-dependent dilation. In both normal and vasospastic groups, the pharmacological responses of dilated segments of basilar arteries were compared to those of nondilated segments of the same arteries. Vessels from all groups were examined using scanning electron microscopy (EM) and transmission EM. Scanning EM was used to study the intact vessel wall, the smooth-muscle cell layer obtained after digestion with hydrochloric acid, and the extracellular matrix obtained after digestion with bleach. Cross-sections of the vessel wall were examined using transmission EM. The most striking finding was that immediately after in vitro TBA of both normal and vasospastic canine basilar arteries, there was a significant reduction (p < 0.05) of responses to both vasoconstrictors and vasorelaxants. As revealed by scanning EM and transmission EM, both normal and vasospastic vessels dilated with TBA showed flattening and patchy denudation of the endothelium, and straightening and occasional rupturing of the internal elastic lamina. In addition, vasospastic vessels dilated with TBA showed decreased surface rippling and mild stretching and straightening of smooth-muscle cells, and mild thinning of the tunica media. There was no gross vascular disruption or obvious change in the extracellular matrix of the vessel walls of either normal or vasospastic arteries after TBA. These results suggest that functional impairment of vasoreactivity in the vessel wall as a result of mechanical stretching of the smooth-muscle layer plays a more important role than structural alteration, at least in the immediate dilation produced in vasospastic arteries by TBA.
Why the European Parliament rejected the patenting of human genes.
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The Management Research Initiative.
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Mike Grace talks to Stephen Noar.
Denplan as a company has been at the forefront of facing up to the uncertain future for the profession and creating an alternative choice for both patients and dentists. Despite initial scepticism from many people the company has survived, prospered and grown. Recently, Denplan took another major step in its development by combining with Private Patients Plan. It seemed like an opportune time to talk to Stephen Noar, Managing Director of Denplan since its beginning.