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At least 613 records · Page 34Linked to original sources
PubMed2003

[The measurement of retentive force of laser-melted and cast post-keepers of Magfit magnetic attachments].

OBJECTIVE: In order to compare the influence of casting and laser welding on magnetic retentive force, the magnetic retentive forces of laser-melted and cast post-keepers of the magnetic attachments were measured in vitro. METHODS: 5 cast and 6 laser-melted post-keeper specimens (Magfit MD800) were formed, respectively. Using untreated keeper as control group, the vertical magnetic retentive forces were measured by a universal testing machine. RESULTS: The average vertical magnetic retentive force of the laser-melted post-keeper group and the cast post-keeper group in vitro were (4.223 +/- 0.217,0)N, (3.792,9 +/- 0.296,4)N, respectively. Compared with the cast post-keeper group, the average vertical magnetic retentive force of the laser-melted post-keeper groups was much higher in vitro (P < 0.05). CONCLUSION: Laser welding had less influence on the magnetic retentive force of the magnetic attachments than casting.

Dental Alloys↗
PubMed2003

[The relationship between clasp retention and the depth of undercut].

OBJECTIVE: To study the relationship between the depth of undercut and the retention of clasp, as a basic information in clinic designing of clasp. METHODS: The Chatillon force measuring instrument was used to record the retention of 18 Co-Cr alloy casting Akers clasps when they were dislodging from undercuts of different depths (0.25 mm, 0.50 mm, 0.75 mm) on bicuspid and molar. All the data was analyzed by ANOVA. RESULTS: It is showed that the deeper the undercuts the greater the retention is. The retention of the clasp on molar is greater than premolar in the same condition of undercut. The effect of the types of the abutment and the depths of the undercut are both obvious on the retention of clasp. CONCLUSIONS: Within the elastic limit of the material, the retention of clasp and the depth of abutment undercut show a positive correlation.

Dental Clasps↗
PubMed2004

[Measurements of the flux densities of static magnetic fields generated by two types of dental magnetic attachments and their retentive forces].

OBJECTIVE: To measure and analyze the flux densities of static magnetic fields generated by two types of commonly used dental magnetic attachments and their retentive forces, and to provide guidance for the clinical application of magnetic attachments. METHODS: A digital Gaussmeter was used to measure the flux densities of static magnetic fields generated by two types of magnetic attachments, under four circumstances: open-field circuit; closed-field circuit; keeper and magnet slid laterally for a certain distance; and existence of air gap between keeper and magnet. The retentive forces of the magnetic attachments in standard closed-field circuit, with the keeper and magnet sliding laterally for a certain distance or with a certain air gap between keeper and magnet were measured by a tensile testing machine. RESULTS: There were flux leakages under both the open-field circuit and closed-field circuit of the two types of magnetic attachments. The flux densities on the surfaces of MAGNEDISC 800 (MD800) and MAGFIT EX600W (EX600) magnetic attachments under open-field circuit were 275.0 mT and 147.0 mT respectively. The flux leakages under closed-field circuit were smaller than those under open-field circuit. The respective flux densities on the surfaces of MD800 and EX600 magnetic attachments decreased to 11.4 mT and 4.5 mT under closed-field circuit. The flux density around the magnetic attachment decreased as the distance from the surface of the attachment increased. When keeper and magnet slid laterally for a certain distance or when air gap existed between keeper and magnet, the flux leakage increased in comparison with that under closed-field circuit. Under the standard closed-field circuit, the two types of magnetic attachments achieved the largest retentive forces. The retentive forces of MD800 and EX600 magnetic attachments under the standard closed-field circuit were 6.20 N and 4.80 N respectively. The retentive forces decreased with the sliding distance or with the increase of air gap between keeper and magnet. CONCLUSION: The magnetic attachments have flux leakages. When they are used in patients' oral cavities, if keeper and magnet are not attached accurately, the flux leakage will increase, and at the same time the retentive force will decrease. Therefore the keeper and magnet should be attached accurately in clinical application.

Denture Precision Attachment↗
PubMed2004

[The experimental study of the relationship between preparation height and retention of complete crowns].

PURPOSE: This study was to discuss the influence of preparation height on retention of complete crown. METHODS: In this study we measured the retention of complete crown with the preparation height 2 mm, 3 mm, 4 mm and 5 mm. All crowns had no preparation taper and no bonding agent was used. The retention of crowns was measured and the data was statistically analyzed by t test. RESULTS: The preparation height was directly proportional to the retention of complete crown. And the crown with the height of 2 mm had enough retention when the crown had no preparation taper. CONCLUSION: In order to get enough retention of short height molar, we should induce the preparation taper.

Crowns↗
PubMed1994

Patient-controlled analgesia and postoperative urinary retention after hysterectomy for benign disease.

BACKGROUND: Because postoperative urinary retention can result in considerable morbidity and the rate of retention after hysterectomy has recently increased at our institutions, we conducted a study to determine risk factors for the disorder. STUDY DESIGN: A cohort of 366 consecutive patients who had undergone uncomplicated abdominal or vaginal hysterectomy for benign disease and who met strict inclusion criteria were studied retrospectively by means of a review of their medical records. Student's t test and multivariate logistic regression analysis were used to assess the effects of operative time, amount of fluid given perioperatively, type and amount of analgesic agent administered postoperatively, age of the patient, performance of a vaginal versus an abdominal hysterectomy, and the postoperative use of patient-controlled analgesia on the rate of postoperative urinary retention in these patients. RESULTS: After adjustment for confounding factors, only the use of patient-controlled analgesia (p = 0.0001) and vaginal hysterectomy (p = 0.0003) were significantly related to postoperative urinary retention. Patients who used patient-controlled analgesia were 5.7 times (95 percent confidence interval, 2.6 to 12.4) more likely to have urinary retention than those given an intramuscular agent. CONCLUSIONS: Urinary retention after hysterectomy might be avoided by administering analgesic agents intramuscularly or inserting a suprapubic cystostomy catheter postoperatively, especially in patients who have undergone a vaginal procedure.

Adult↗
PubMed1994

Effect of gestational undernutrition and chlordiazepoxide treatment on black/white discrimination learning and retention in young rats.

Effects of prenatal undernutrition and chlordiazepoxide treatment on learning acquisition, and subsequent retention, of a black/white discrimination task, was assessed in the offspring. Undernutrition of the dams was induced by restricting food intake to half, throughout the period of gestation, whereas chlordiazepoxide (2.5 mg/kg, ip) treatment was given from day 13 to 20 of gestation, this being the critical period for neural development in this species. The pups born were subjected to brightness discrimination learning, and retention of the learning acquisition after an interval of one week, in a single unit black/white T-maze, at 8-9 weeks of age. The results indicate that prenatal undernutrition induces significant learning and retention deficits in the offspring. Prenatally administered chlordiazepoxide induced significant deficits in learning acquisition and subsequent retention of the discrimination problem. Chlordiazepoxide induced similar learning and retention deficits in the normal and undernourished rats, and exaggerated the learning and retention deficits induced by undernutrition. The results indicated that the prenatal insults in the form of undernourishment and anxiolytic benzodiazepine compounds, leave a lasting imprint on cognitive behaviour of the offspring.

Animals↗
PubMed1993

Patient-controlled analgesia and postoperative urinary retention after open appendectomy.

We retrospectively studied 279 patients who had undergone uncomplicated open appendectomy for acute appendicitis to determine risk factors for postoperative urinary retention. The gender of the patients, the operating time and the amount of fluid given perioperatively had no influence on the occurrence of retention. The amount of analgesic agent administered postoperatively and the age of the patient were significantly associated with urinary retention (p = 0.01 and p < 0.0001, respectively, after adjustment for potential confounding factors). The use of meperidine hydrochloride as compared with morphine and of patient-controlled analgesia as compared with intramuscular delivery were initially found to be significantly related to retention (p = 0.014 and p < 0.0001, respectively). After the effects of the age of the patient, the drug type and the amount of fluid and analgesic agent administered were controlled for, patient-controlled analgesia remained significantly associated with retention (p < 0.0001), whereas the type of drug given was no longer significant after controlling for potential confounding factors. Because we found that urinary retention was 13 times more likely to occur in the patients who had patient-controlled analgesia, we recommend that the use of this form of analgesia delivery be avoided after open appendectomy.

Adolescent↗
PubMed1993

Fracture resistance of amalgam and composite resin cores retained by various intradentinal retentive features.

The fracture strengths of amalgam and composite resin cores retained by three types of intradentinal retentive features were compared with the fracture strength of cores retained by four self-threaded retentive pins. Composite resin cores had significantly greater resistance to fracture than amalgam cores with any of the retentive features. The fracture strength of amalgam cores retained by retentive pins was comparable to that of amalgam cores retained by a post with a countersink, but significantly higher than the strength of those retained by slots or channels. The fracture strength of composite resin cores retained by retentive pins was significantly higher than that of composite resin cores retained by any of the alternative intradentinal retentive features.

Analysis of Variance↗
PubMed2004

The two faces of enhancing utilization of health-care services: determinants of patient initiation and retention in rural Burkina Faso.

OBJECTIVE: To explore the factors that determine whether a patient will initiate treatment within a system of health-care services, and the factors that determine whether the patient will be retained in the chosen system, in Nouna, rural Burkina Faso. METHODS: The data used were pooled from four rounds of a household survey conducted in Nouna, rural Burkina Faso. The ongoing demographic surveillance system provided a sampling framework for this survey in which 800 households were sampled using a two-stage cluster sampling procedure. More than one treatment episode was observed for a single episode of illness per patient. The multinomial logit model was used to explore the determinants of patient initiation to systems of modern, traditional and home treatment, and a binary logit model was used to explore the determinants of patient retention within the chosen health-care provider system. FINDINGS: The results suggest that the determinants of patient initiation and their subsequent retention are different. Household income, education, urban residence and expected competency of the provider are positive predictors of initiation, but not of retention, for modern health-care services. Only perceived quality of care positively predicted retention in modern health-care services. CONCLUSION: Interventions focusing on patient initiation and patient retention are likely to be different. Policies directed at enhancing initiation for modern health-care services would primarily focus on reducing financial barriers, while those directed at increasing retention would primarily focus on attributes that improve the perceived quality of care.

Adult↗
PubMedDate not supplied

Quantitative structure-retention relationship study of tetrazolium salts on alumina support.

The retention of 7 monotetrazolium and 9 ditetrazolium salts was determined on alumina and reversed-phase (RP) alumina layers using n-hexane-2-propanol and water-2-propanol mixtures as eluents. The retention capacity and the specific surface area of solutes in contact with the stationary phases were calculated. Quantitative structure-retention relationship calculations indicated that the retention capacity of solutes on RP alumina layers depended not only on the molecular hydrophobicity but also on the hydrogen-donor and acceptor properties. Specific surface areas were related to the electronic and steric parameters of the solutes. Calculations suggested that the retention on both alumina and RP alumina layers is of mixed character, hydrophobic, electronic and steric parameters are equally involved in the retention.

Aluminum Oxide↗
PubMed2004

Retention procedures for stabilising tooth position after treatment with orthodontic braces.

BACKGROUND: Retention is the phase of orthodontic treatment that attempts to keep teeth in the corrected positions after orthodontic (dental) braces. Without a phase of retention there is a tendency for the teeth to return to their initial position (relapse). To prevent relapse almost every patient who has orthodontic treatment will require some type of retention. OBJECTIVES: To evaluate the effectiveness of different retention strategies used to stabilise tooth position after orthodontic braces. SEARCH STRATEGY: The Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE and EMBASE were searched. Several journals were handsearched. No language restrictions were applied. Authors of randomised controlled trials (RCTs) were identified and contacted to identify unpublished trials. Most recent search: December 2002. SELECTION CRITERIA: RCTs on children and adults, who have had retainers fitted or adjunctive procedures undertaken, following orthodontic treatment with braces to prevent relapse. The outcomes are: how well the teeth are stabilised, survival of retainers, adverse effects on oral health and quality of life. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted in duplicate and independently by two reviewers. As no two studies compared the same retention strategies (interventions) it was not possible to combine the results of any studies. MAIN RESULTS: Four trials satisfied the inclusion criteria. These trials all compared different interventions: circumferential supracrestal fiberotomy (CSF) combined with full-time removable retainer versus a full-time removable retainer alone; circumferential supracrestal fiberotomy (CSF) combined with a nights-only removable retainer versus a nights-only removable retainer alone; removable Hawley retainer versus a clear overlay retainer; and three types of fixed retainers versus a removable retainer. There was weak unreliable evidence, based on data from one trial, that there was a statistically significant increase in stability in both the mandibular (p < 0.001) and maxillary anterior segments (p < 0.001) when the CSF was used, compared with when it was not used. There was also weak, unreliable evidence that teeth settle quicker with a Hawley retainer than with a clear overlay retainer after 3 months. The quality of the trial reports was generally poor. REVIEWER'S CONCLUSIONS: There are insufficient research data on which to base our clinical practice on retention at present. There is an urgent need for high quality randomised controlled trials in this crucial area of orthodontic practice.

Humans↗
PubMed2006

Retention procedures for stabilising tooth position after treatment with orthodontic braces.

BACKGROUND: Retention is the phase of orthodontic treatment that attempts to keep teeth in the corrected positions after treatment with orthodontic (dental) braces. Without a phase of retention there is a tendency for the teeth to return to their initial position (relapse). To prevent relapse almost every patient who has orthodontic treatment will require some type of retention. OBJECTIVES: To evaluate the effectiveness of different retention strategies used to stabilise tooth position after orthodontic braces. SEARCH STRATEGY: The Cochrane Oral Health Group's (OHG) Trials Register, CENTRAL, MEDLINE and EMBASE were searched. Handsearching of orthodontic journals was undertaken in keeping with the Cochrane OHG search programme. No language restrictions were applied. Authors of randomised controlled trials (RCTs) were identified and contacted to identify unpublished trials. Most recent search: May 2005. SELECTION CRITERIA: RCTs on children and adults, who have had retainers fitted or adjunctive procedures undertaken, following orthodontic treatment with braces to prevent relapse. The outcomes were: how well the teeth were stabilised, survival of retainers, adverse effects on oral health and quality of life. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted in duplicate and independently by two review authors. As no two studies compared the same retention strategies (interventions) it was not possible to combine the results of any studies. MAIN RESULTS: Five trials satisfied the inclusion criteria. These trials all compared different interventions: circumferential supracrestal fiberotomy (CSF) combined with full-time removable retainer versus a full-time removable retainer alone; CSF combined with a nights-only removable retainer versus a nights-only removable retainer alone; removable Hawley retainer versus a clear overlay retainer; multistrand wire retainer versus a ribbon-reinforced resin bonded retainer; and three types of fixed retainers versus a removable retainer. There was weak unreliable evidence, based on data from one trial, that there was a statistically significant increase in stability in both the mandibular (lower) (P < 0.001) and maxillary (upper) anterior segments (P < 0.001) when the CSF was used, compared with when it was not used. There was also weak, unreliable evidence that teeth settle quicker with a Hawley retainer than with a clear overlay retainer after 3 months. The quality of the trial reports was generally poor. AUTHORS' CONCLUSIONS: There are insufficient research data on which to base our clinical practice on retention at present. There is an urgent need for high quality randomised controlled trials in this crucial area of orthodontic practice.

Humans↗
PubMed1994

Retention of asbestos bodies in the lungs of welders.

Examination of asbestos bodies (AB) retained in the lungs is a useful way of assessing past occupational exposure to this material. AB retention has been extensively studied in workers directly exposed to asbestos, but less so in those end users, such as welders, who use asbestos-containing products. We therefore retrospectively studied AB retention in 211 welders, for whom biological testing procedures had been requested by a chest physician, between 1988 and 1991. Optical microscopy of AB was performed on samples of sputum (40 subjects), bronchoalveolar lavage fluid (BAL) (147 subjects), and lung tissue obtained after thoracotomy (38 subjects). Information on previous jobs and exposure was obtained using a questionnaire (the mean duration of welding activities was 16.6 years). Eighty-two subjects (38.9%) had elevated lung retention of AB in all the samples studied. Significant AB retention occurred in only 30% of sputum samples, but in 40.1% of BAL samples and 39.5% of lung tissue samples. The duration of welding activities correlated with the density of AB in BAL or lung tissue (r = 0.31, p < 0.01 and r = 0.49, p < 0.05, respectively). On the basis of the questionnaire, only two of the welders with significant AB retention had other occupational exposure to asbestos. Our findings suggest that welding activities may increase lung retention of AB, and consequently might produce higher risks of fibrotic and/or malignant pulmonary diseases. These potential risks need to be brought to the attention of doctors; a longitudinal follow-up may also be warranted in such populations, even after individuals have ceased their welding jobs.

Asbestos↗
PubMedDate not supplied

Quantitative relationships between the structure of beta-adrenolytic and antihistamine drugs and their retention on an alpha 1-acid glycoprotein HPLC column.

Chromatographic retention parameters of a series of 7 beta-adrenolytics and of 12 antihistamine drugs were determined employing an alpha 1-acid glycoprotein (AGP) high-performance liquid chromatographic (HPLC) column. For the group of antihistamines capillary electrophoretic (CE) retention was additionally measured in the presence of either AGP or human serum albumin (HSA). Two series of solutes hydrophobicity parameters were obtained by reversed-phase HPLC on an immobilized artificial membrane (IAM) column. The solutes studied were subjected to molecular modelling and the structural descriptors obtained were applied in studies of quantitative structure-retention (protein binding) relationships (QSRR). It was found that retention on AGP correlates well with the literature on physiological protein binding data. This retention was demonstrated to depend on hydrophobicity: to a lesser extent in the case of beta-adrenolytics and strongly in the case of antihistamines. Hydrophobicity, along with molecular width and electron excess charge on aliphatic nitrogen was demonstrated to describe retention of antihistamines on AGP. The AGP column is recommended as a convenient reactor for studies of drug-protein interactions. Preliminary CE data do not correlate with the HPLC data.

Adrenergic beta-Antagonists↗
PubMed2002

Incomplete retention after direct myocardial injection.

Direct intramyocardial injection may permit local delivery of protein and gene therapy agents for myocardial and coronary artery disease. Little is known about the immediate fate of materials administered via percutaneous endomyocardial catheters or via surgical epicardial injection. In this study, we use a novel method to evaluate the acute retention of agents injected directly into the myocardium, compare epicardial with the percutaneous endocardial and postmortem delivery, and evaluate the influence of injectate volume on myocardial retention. Fifteen 40-50 kg pigs underwent overlapping myocardial injections using a percutaneous endomyocardial catheter, an epicardial needle via an open chest, and epicardial needle postmortem. Multiple distinct 15 micro neutron-activated microsphere species were used as tracers. Two or three myocardial walls were injected in each animal using 3.5 mm, 27-28 gauge needles at varying injectate volumes. Animals were sacrificed immediately. Myocardial walls were divided and multiple microsphere species were quantified. In an additional study, nine 70 kg pigs underwent percutaneous endomyocardial injections with replication-deficient adenovirus encoding for the production of lac-Z. The injectate volume was varied, while the viral particle number remained constant. The animals were sacrificed 5 days after the percutaneous injections; the heart, liver, and spleen were collected for beta-galactosidase activity. Endomyocardial injection was associated with 43% +/- 15% microsphere retention, compared with 15% +/- 21% (P < 0.01) retention of open chest epicardial injection and 89% +/- 60% (P < 0.01) for postmortem injection. Reducing the injectate volume from 100 to 10 microL improved microsphere retention (P = 0.01). There was a trend toward improved viral transfection associated with smaller injection volumes. Despite direct intramyocardial administration, a significant fraction of injectate is not retained locally. Catheter-based needle endomyocardial injection is associated with equivalent or superior injectate retention compared with open chest epicardial injection. Proportionately, more injectate may be retained at lower volumes. Loss may involve a combination of channel leakage, venous, and lymphatic return.

Adenoviridae↗
PubMed1987

Patterns of anthracycline retention modulation in human tumor cells.

Laser excitation of cellular doxorubicin and daunomycin content (with or without incubation in the presence of efflux blockers such as phenothiazines or verapamil) was studied in cells from leukemic peripheral blood, bone marrow aspirates, and ascites and pleural fluid of solid tumor patients. Selected examples are presented to show that heterogeneity in cellular anthracycline retention as well as sensitivity to efflux modulators is seen in human tumor cells. Several tumor subpopulations differing in their cellular retention of anthracyclines or sensitivity to modulators were seen. In serial tumor samples from patients (pre- and post-treatment with anthracycline-containing protocols), initial drug retention and sensitivity to efflux modulators was followed by lack of drug retention and insensitivity to modulators. The present study shows that in view of the variables encountered in drug-retention characteristics and sensitivity to efflux modulators, one needs to screen tumor samples before recommending use of any particular transport modulator to enhance drug retention and sensitivity of drug-resistant cells.

Bone Marrow↗
PubMed1997

Stringent thiol-mediated retention in B lymphocytes and Xenopus oocytes correlates with inefficient IgM polymerization.

Thiol-dependent retention mechanisms involving the microsecond chain Cys575 ensure that only polymeric IgM are secreted. B lymphocytes are unable to polymerize IgM and degrade unpolymerized precursors intracellularly. Since several non-lymphoid transfectants secrete hexameric IgM, specific mechanism(s) inhibiting IgM polymerization/secretion may be active in B cells. Here, we show that Xenopus laevis oocytes are also unable to polymerize IgM and retain this isotype via Cys575 as efficiently as B cells. The mechanisms and the hierarchy of the thiol-dependent pre-Golgi retention are conserved in amphibian oocytes, as indicated by the efficient retention of secretory IgA and the slow secretion of unassembled J558 lambda chains. We also show that B cells do not lack any structural component necessary to polymerize IgM: after retention has been weakened by 2-mercaptoethanol, polymerization can occur if oxidizing conditions are restored. Since release from retention can result in polymerization, stringent retention in B cells and oocytes might be at the basis of their common inability to polymerize secretory IgM. Our findings suggest that disulfide interchange reactions in the exocytic compartment can be modulated during B cell differentiation to control IgM secretion.

Animals↗
PubMed1996

Adenosine does not mediate renal sodium retention and peripheral vasodilation elicited by partial portal vein ligation in rats.

This study was conducted to assess the role of adenosine in the peripheral vasodilation and sodium retention that occurs after partial portal vein ligation (PVL) in the rat. The experiment was performed on day 1 after surgery when transient maximal sodium retention developed and day 7 when rats returned to sodium balance. Hemodynamic studies were conducted under anesthesia in portal hypertensive rats with sodium retention and in sham-operated controls. Measurements were obtained before and after administration of a nonselective A1 and A2 adenosine receptor antagonist 1,3-dipropyl-8-p-sulfophenylxanthine (DPSPX) (10 mg/kg intravenously followed by 150 micrograms/min). Under baseline conditions, portal hypertensive rats with sodium retention were hypotensive, with decreases in total peripheral resistance and filtration fraction on day 1 in comparison with the control group. Although hyperdynamic circulation was still maintained by day 7, there was a return to sodium balance. The adenosine receptor antagonist had a modest vasoconstrictor effect on systemic and renal vasculature in both groups, but less in portal hypertensive rats. However, no change in glomerular filtration rate was observed. DPSPX induced a natriuresis in control rats (from 0.40 +/- 0.11 to 5.97 +/- 0.61 mEq/min on day 1, from 0.48 +/- 0.20 to 6.34 +/- 0.45 mEq/min on day 7). This response was attenuated in portal hypertensive rats on day 1 (from 0.14 +/- 0.04 to 1.67 +/- 0.57 mEq/min). but not on day 7 (from 0.20 +/- 0.06 to 5.11 +/- 0.55 mEq/min). These results suggest that in portal hypertensive rats (1) adenosine is not responsible for vasodilation and sodium retention, (2) a sodium-retaining factor acting directly on the renal tubule is responsible for sodium retention.

Adenosine↗