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Biomedical subjects

C Main

Publications and source records attributed to C Main.

At least 19 recordsLinked to original sources
PubMed2006

Topotecan, pegylated liposomal doxorubicin hydrochloride and paclitaxel for second-line or subsequent treatment of advanced ovarian cancer: a systematic review and economic evaluation.

OBJECTIVES: To examine the clinical effectiveness and cost-effectiveness of intravenous formulations of topotecan monotherapy, pegylated liposomal doxorubicin hydorocholoride (PLDH) monotherapy and paclitaxel used alone or in combination with a platinum-based compound for the second-line or subsequent treatment of advanced ovarian cancer. DATA SOURCES: Electronic databases covering publication years 2000-4. Company submissions. REVIEW METHODS: Seventeen databases were searched for randomised controlled trials (RCTs) and systematic reviews for the clinical effectiveness of PLDH, topotecan and paclitaxel and economic evaluations of the cost-effectiveness of PLDH, topotecan and paclitaxel. Selected studies were quality assessed and data extracted, as were the three company submissions. A new model was developed to assess the costs of the alternative treatments, the differential mean survival duration and the impact of health-related quality of life. Monte-Carlo simulation was used to reflect uncertainty in the cost-effectiveness results. RESULTS: Nine RCTs were identified. In five of these trials, both the comparators were used within their licensed indications. Of these five, three included participants with both platinum-resistant and platinum-sensitive advanced ovarian cancer, and a further two only included participants with platinum-sensitive disease. The comparators that were assessed in the three trials that included both subtypes of participants were PLDH versus topotecan, topotecan versus paclitaxel and PLDH versus paclitaxel. In the further two trials that included participants with the subtype of platinum-sensitive disease, the comparators that were assessed were single-agent paclitaxel versus a combination of cyclophosphamide, doxorubicin and cisplatin (CAP) and paclitaxel plus platinum-based chemotherapy versus conventional platinum-based therapy alone. A further four trials were identified and included in the review in which one of the comparators in the trial was used outside its licensed indication. The comparators assessed in these trials were oxaliplatin versus paclitaxel, paclitaxel given weekly versus every 3 weeks, paclitaxel at two different dose levels and oral versus intravenous topotecan. Four studies met the inclusion criteria for the cost-effectiveness review. The review of the economic evidence from the literature and industry submissions identified a number of significant limitations in existing studies assessing the cost-effectiveness of PLDH, topotecan and paclitaxel. Analysis 1 assessed the cost-effectiveness of PLDH, topotecan and paclitaxel administered as monotherapies. Sensitivity analysis was undertaken to explore the impact of patient heterogeneity (e.g. platinum-sensitive and platinum-resistant/refractory patients), the inclusion of additional trial data and alternative assumptions regarding treatment and monitoring costs. In the base-case results for Analysis 1, paclitaxel monotherapy emerged as the cheapest treatment. When the incremental cost-effectiveness ratios (ICERs) were estimated, topotecan was dominated by PLDH. Hence the options considered in the estimation of the ICERs were paclitaxel and PLDH. The ICER for PLDH compared with paclitaxel was pound 7033 per quality-adjusted life-year (QALY) in the overall patient population (comprising platinum-sensitive, -refractory and -resistant patients). The ICER was more favourable in the platinum-sensitive group ( pound 5777 per QALY) and less favourable in the platinum-refractory/resistant group ( pound 9555 per QALY). The cost-effectiveness results for the base-case analysis were sensitive to the inclusion of additional trial data. Incorporating the results of the additional trial data resulted in less favourable estimates for the ICER for PLDH versus paclitaxel compared with the base-case results. The ICER of PLDH compared with paclitaxel was pound 20,620 per QALY in the overall patient population, pound 16,183 per QALY in the platinum-sensitive population and pound 26,867 per QALY in the platinum-resistant and -refractory population. The results from Analysis 2 explored the cost-effectiveness of the full range of treatment comparators for platinum-sensitive patients. The treatment options considered in this model comprised PLDH, topotecan, paclitaxel-monotherapy, CAP, paclitaxel/platinum combination therapy and platinum monotherapy. Owing to the less robust approaches that were employed to synthesise the available evidence and the heterogeneity between the different trials, the reliability of these results should be interpreted with some caution. Topotecan, paclitaxel monotherapy and PLDH were all dominated by platinum monotherapy (i.e. higher costs and lower QALYs). After excluding these alternatives, the treatments that remained under consideration were platinum monotherapy, CAP and paclitaxel-platinum combination therapy. Of these three alternatives, platinum monotherapy was the least costly and least effective. The ICER for CAP compared with platinum monotherapy was pound 16,421 per QALY. The ICER for paclitaxel-platinum combination therapy compared with CAP was pound 20,950 per QALY. CONCLUSIONS: For participants with platinum-resistant disease there was a low probability of response to treatment with PLDH, topotecan or paclitaxel. Furthermore, there was little difference between the three comparators in relation to overall survival. The comparators did, however, differ considerably in their toxicity profiles. Given the low survival times and response rates, it appears that the maintenance of quality of life and the control of symptoms and toxicity are paramount in this patient group. As the three comparators differed significantly in terms of their toxicity profiles, patient and physician choice is also an important element that should be addressed when decisions are made regarding second-line therapy. It can also be suggested that this group of patients may benefit from being included in further clinical trials of new drugs. For participants with platinum-sensitive disease there was a considerable range of median survival times observed across the trials. The most favourable survival times and response rates were observed for paclitaxel and platinum combination therapy. This suggests that treatment with combination therapy may be more beneficial than treatment with a single-agent chemotherapeutic regimen. In terms of single-agent compounds, the evidence suggests that PLDH is more effective than topotecan. Evidence from a further trial that compared PLDH and paclitaxel suggests that there is no significant difference between these two comparators in this trial. The three comparators did, however, differ significantly in terms of their toxicity profiles across the trials. Although treatment with PLDH may therefore be more beneficial than that with topotecan, patient and physician choice as to the potential toxicities associated with each of the comparators and the patient's ability and willingness to tolerate these are of importance. Assuming the NHS is willing to pay up to pound 20,000-40,000 per additional QALY, PLDH appears to be cost-effective compared with topotecan and paclitaxel monotherapy, in terms of the overall patient population and the main subgroups considered. The cost-effectiveness results for the base-case analysis were sensitive to the inclusion of additional trial data. Incorporating the results of additional trial data gave less favourable estimates for the ICER for PLDH versus paclitaxel monotherapy, compared with the base-case results. Although the ICER of PLDH compared with paclitaxel monotherapy was less favourable, PLDH was still cost-effective compared with topotecan and paclitaxel monotherapy. For platinum-sensitive patients, the combination of paclitaxel and platinum appears to be cost-effective. On the strength of the evidence reviewed here, it can be suggested that participants with platinum-resistant disease may benefit from being included in further clinical trials of new drugs. To assess the effectiveness of combination therapy against a single-agent non-platinum-based compound, it can be suggested that a trial that compared paclitaxel in combination with a platinum-based therapy versus single-agent PLDH would be a reasonable option.

Antibiotics, Antineoplastic↗
PubMed2004

Clinical effectiveness and cost-effectiveness of clopidogrel and modified-release dipyridamole in the secondary prevention of occlusive vascular events: a systematic review and economic evaluation.

OBJECTIVES: To examine the clinical effectiveness and cost-effectiveness of two alternative antiplatelet agents, clopidogrel and modified-release (MR)-dipyridamole, relative to prophylactic doses of aspirin for the secondary prevention of occlusive vascular events. DATA SOURCES: Electronic databases. REVIEW METHODS: A total of 2906 titles and abstracts were rigorously screened and 441 studies were assessed in detail. Two RCTs were identified. For the assessment of cost-effectiveness, eight reviews were identified. The results were presented in structured tables and as a narrative summary. No additional clinical effectiveness data were presented in either of two company submissions. All economic evaluations (including accompanying models) included in the company submissions were assessed. Following this analysis, if the existing models (company or published) were not sufficient, a de novo model or modified versions of the models were developed. RESULTS: In the CAPRIE trial the point estimate for the primary outcome, i.e. ischaemic stroke, myocardial infarction (MI) or vascular death, favoured clopidogrel over aspirin, but the boundaries of the confidence intervals raise the possibility that clopidogrel is not more beneficial than aspirin. In terms of the secondary outcomes reported, there was a non-significant trend in favour of clopidogrel over aspirin but the boundaries of the confidence intervals on the relative risks all crossed unity. There was no difference in the number of patients ever reporting any bleeding disorder in the clopidogrel group compared with the aspirin group. The incidences of rash and diarrhoea were statistically significantly higher in the clopidogrel group than the aspirin group. Patients in the aspirin group had a higher incidence of indigestion/nausea/vomiting than patients in the clopidogrel group. Haematological adverse events were rare in both the clopidogrel and aspirin groups. No cases of thrombotic thrombocytopenic purpura were reported in either group. Treatment with MR-dipyridamole alone did not significantly reduce the risk of any of the primary outcomes reported in ESPS-2 compared with treatment with aspirin. ASA-MR-dipyridamole was significantly more effective than aspirin alone in patients with stroke or transient ischaemic attacks (TIAs) at reducing the outcome of stroke and marginally more effective at reducing stroke and/or death. Treatment with ASA-MR-dipyridamole did not statistically significantly reduce the risk of death compared to treatment with aspirin. The number of strokes was statistically significantly reduced in the ASA-MR-dipyridamole group compared with the MR-dipyridamole group. In terms of the other primary outcomes, stroke and/or death and death, the results favoured treatment with ASA-MR-dipyridamole but the findings were not statistically significant. There was no difference in the number of bleeding complications between the ASA-MR-dipyridamole and aspirin groups. The incidence of bleeding complications was significantly lower in the MR-dipyridamole treatment group. More patients in the MR-dipyridamole treatment groups experienced headaches compared to patients receiving treatment with aspirin alone. The York model assessed the cost-effectiveness of differing combinations of treatment strategies in four patient subgroups, under a number of different scenarios. The results of the model were sensitive to the assumptions made in the alternative scenarios, in particular the impact of therapy on non-vascular deaths. CONCLUSIONS: Clopidogrel was marginally more effective than aspirin at reducing the risk of ischaemic stroke, MI or vascular death in patients with atherosclerotic vascular disease, however, it did not statistically significantly reduce the risk of vascular death or death from any cause compared with aspirin. There was no statistically significant difference in the number of bleeding complications experienced in the clopidogrel and aspirin groups. MR-dipyridamole in combination with aspirin was superior to aspirin alone at reducing the risk of stroke and marginally more effective at reducing the risk of stroke and/or death. Compared with treatment with MR-dipyridamole alone, MR-dipyridamole in combination with aspirin significantly reduced the risk of stroke. Treatment with MR-dipyridamole in combination with aspirin did not statistically significantly reduce the risk of death compared with aspirin. Compared with treatment with MR-dipyridamole alone, bleeding complications were statistically significantly higher in patients treated with aspirin and MR-dipyridamole in combination with aspirin. Due to the assumptions that have to be made, no conclusions could be drawn about the relative effectiveness of MR-dipyridamole, alone or in combination with aspirin, and clopidogrel from the adjusted indirect comparison. The following would apply for a cost of up to GBP20,000-40,000 per additional quality-adjusted life-year. For the stroke and TIA subgroups, ASA-MR-dipyridamole would be the most cost-effective therapy given a 2-year treatment duration as long as all patients were not left disabled by their initial (qualifying) stroke. For a lifetime treatment duration, ASA-MR-dipyridamole would be considered more cost-effective than aspirin as long as treatment effects on non-vascular deaths are not considered and all patients were not left disabled by their initial stroke. In patients left disabled by their initial stroke, aspirin is the most cost-effective therapy. Clopidogrel and MR-dipyridamole alone would not be considered cost-effective under any scenario. For the MI and peripheral arterial disease subgroups, clopidogrel would be considered cost-effective for a treatment duration of 2 years. For a lifetime treatment duration, clopidogrel would be considered more cost-effective than aspirin as long as treatment effects on non-vascular deaths are not considered. It is suggested that the combination of clopidogrel and aspirin should be evaluated for the secondary prevention of occlusive vascular events. Also randomised, direct comparisons of clopidogrel and MR-dipyridamole in combination with aspirin are required to inform the treatment of patients with a history of stroke and TIA, plus trials that compare treatment with clopidogrel and MR-dipyridamole for the secondary prevention of vascular events in patients who demonstrate a genuine intolerance to aspirin.

Aspirin↗
PubMed2004

Clopidogrel used in combination with aspirin compared with aspirin alone in the treatment of non-ST-segment-elevation acute coronary syndromes: a systematic review and economic evaluation.

OBJECTIVES: To review systematically the clinical effectiveness and the cost-effectiveness of clopidogrel used in combination with standard therapy including aspirin, compared with standard therapy alone for the treatment of non-ST-segment elevation acute coronary syndromes (ACS). DATA SOURCES: Electronic databases. Manufacturers' submissions. REVIEW METHODS: Studies were selected using rigorous criteria. The quality of randomised controlled trials (RCTs) was assessed according to criteria based on NHS CRD Report No. 4, and the quality of systematic reviews was assessed according to the guidelines for the Database of Reviews of Effect (DARE) criteria. The quality of economic evaluations was assessed according to a specifically tailored checklist. The clinical effectiveness and cost-effectiveness of clopidogrel in combination with standard therapy compared with standard therapy alone were synthesised through a narrative review with full tabulation of the results of the included studies. In the economic evaluations, a cost-effectiveness model was constructed using the best available evidence to determine cost-effectiveness in a UK setting. RESULTS: One RCT (the CURE trial) was a randomised, double-blind, placebo-controlled trial of high quality and showed that clopidogrel in addition to aspirin was significantly more effective than placebo plus aspirin in patients with non-ST-segment elevation ACS for the composite outcome of death from cardiovascular causes, non-fatal myocardial infarction or stroke over the 9-month treatment period. However, clopidogrel was associated with a significantly higher number of episodes of both major and minor bleeding. The results from the five systematic reviews that assessed the adverse events associated with long-term aspirin use showed that aspirin was associated with a significantly higher incidence of haemorrhagic stroke, extracranial haemorrhage and gastrointestinal haemorrhage compared with placebo. Of the cost-effectiveness evidence reviewed, only the manufacturer's submission was considered relevant from the perspective of the NHS. The review of this evidence highlighted potential limitations within the submission in its use of data and in the model structure used. These limitations led to the development of a new model with the aim of providing a more reliable estimate of the cost-effectiveness from the perspective of the UK NHS. This model indicated that clopidogrel appears cost-effective compared with standard care alone in patients with non-ST-elevation ACS as long as the NHS is willing to pay GBP6078 per quality of life year (QALY). The results were most sensitive to the inclusion of additional strategies that assessed alternative treatment durations with clopidogrel. Although treatment with clopidogrel for 12 months remained cost-effective for the overall cohort, provisional findings indicate that the shorter treatment durations may be more cost-effective in patients at low risk. CONCLUSIONS: The results of the CURE trial indicate that clopidogrel in combination with aspirin was significantly more effective than placebo combined with aspirin in a wide range of patients with ACS. This benefit was largely related to a reduction in Q-wave myocardial infarction. There was no statistically significant benefit in relation to mortality. The trial data suggested that a substantial part of the benefit derived from clopidogrel is achieved by 3 months, with a further small benefit over the remaining 9 months of chronic treatment. The results from the base-case model suggest that treatment with clopidogrel as an adjunct to standard therapy (including aspirin) for 12 months, compared with standard therapy alone, is cost-effective in non-ST elevation ACS patients as long as the health service is willing to pay GBP6078 per additional QALY. However, although treatment with clopidogrel for 12 months remained cost-effective for the overall cohort, provisional findings indicate that the shorter treatment durations may be more cost-effective in patients at low risk. To estimate the exact length of time that clopidogrel in addition to standard therapy should be prescribed for patients with non-ST-segment ACS would require a prospective trial that randomised patients to various durations of therapy. This would accurately assess whether a 'rebound' phenomenon occurs in patients if clopidogrel were stopped after 3 months of treatment.

Acute Disease↗
PubMed2002

Size-dependent absorption and defect states in CdSe nanocrystals in various multilayer structures.

GeS2-CdSe superlattices and composite films are prepared by consecutive thermal evaporation of CdSe and GeS2 in vacuum. CdSe layer thickness varies between 1 and 10 nm, while the thickness of GeS2 layers is either equal (in superlattices) to or 20 times greater (in composite films) than that of CdSe layers. Standard spectral photocurrent measurements and various constant photocurrent methods are used to study optical absorption of all samples. An overall blueshift is observed with decreasing CdSe layer thickness of superlattices. This shift is related to a size-induced increase of the optical band gap of CdSe due to one-dimensional carrier confinement in the continuous nanocrystalline CdSe layers. A number of features are observed in the absorption spectra of composite films containing CdSe nanocrystals with average radii of approximately 2.5 and approximately 3.3 nm. They are discussed in terms of three-dimensional carrier confinement and are considered a manifestation of excited electron states in CdSe nanocrystals embedded in GeS2 thin film matrix. In addition to these discrete features, the exponential dependence of the optical absorption (Urbach) edge indicates a distribution of "valence band" tail states associated with disorder. Transient photoconductivity measurements made on similarly prepared SiOx-CdSe superlattices exhibit a rapid fall in photocurrent by a power law decay over several orders of magnitude of time, which is consistent with multi-pletrapping transport via an extensive distribution of deep defects.

Cadmium Compounds↗
PubMed1997

The behavioural response to whiplash injury.

We studied 50 consecutive patients presenting at an accident department after rear-end vehicle collisions and recorded symptoms and psychological test scores within one week of injury, at three months and at two years. The range of neck movement was noted at three months. Within one week of injury, psychological test scores were normal in 82% of the group but became abnormal in 81% of the patients with intrusive or disabling symptoms at over three months (p < 0.001) and remained abnormal in 69% at two years. The clinical outcome after two years could be predicted at three months with 76% accuracy by neck stiffness, 74% by psychological score and 82% by a combination of these variables. The severity of symptoms after a whiplash injury is related both to the physical restriction of neck movement and to psychological disorder. The latter becomes established within three months of the injury.

Accidents, Traffic↗
PubMed1993

Human recombinant interleukin 1 beta suppresses acetylcholine release from rat myenteric plexus.

BACKGROUND: A marked suppression of acetylcholine (ACh) release from myenteric nerves in the inflamed intestine of rats infected by Trichinella spiralis has been shown. In this model, there is increased expression of interleukin 1 beta (IL-1 beta) in the myenteric plexus. Therefore, the ability of IL-1 beta to alter ACh release in longitudinal muscle-myenteric plexus (LMMP) preparations from noninfected rats was examined. METHODS: LMMP preparations were loaded with [3H]choline before stimulation by KCl or electrical field stimulation. ACh release was recorded by measuring 3H in the superfusate. Experiments were performed in the presence or absence of human recombinant IL-1 beta. RESULTS: IL-1 beta had no immediate effect on the basal or stimulated release of ACh. A marked suppression of ACh release was observed in tissues that had been preincubated with IL-1 beta for 60 minutes or more. The effect of IL-1 beta was concentration and time dependent with maximum suppression occurring with 10 ng/mL of the cytokine after a 90-minute incubation. The action of human recombinant (hr) IL-1 beta was abolished by boiling the cytokine for 20 minutes and was prevented by preincubating the cytokine with neutralizing antibody. The IL-1 beta effect was also blocked by cycloheximide and was spontaneously reversible after 60 minutes. CONCLUSION: It was concluded that IL-1 beta suppresses ACh release via the formation and release of a protein mediator that could be another cytokine, including IL-1. Based on these findings, we consider IL-1 beta a putative mediator of the changes in cholinergic nerve function observed in the inflamed rat intestine.

Acetylcholine↗
PubMed1993

Immunomodulatory effects of interferon-gamma in patients with metastatic malignant melanoma.

Interferon-gamma (IFN-gamma) is a potent monocyte/macrophage activating agent that in animal models exhibits a bell-shaped dose-response curve of immunomodulatory activity and antitumor efficacy. Previous clinical trials of IFN-gamma conducted at the maximal tolerated dose (MTD) have been associated with low response rates that may have been due to failure to treat at an optimal immunomodulatory dose (OID). The objective of this study was to test the hypothesis that optimal immunomodulatory activity of IFN-gamma in patients with metastatic melanoma would be obtained at a dose below the MTD. Groups of five patients each were given daily subcutaneous injections of IFN-gamma at doses of 0.01, 0.1, or 0.25 mg/m2. In vivo immunomodulation was assessed by serial measurement of serum neopterin and by flow cytometry. IFN-gamma doses of 0.1 or 0.25 mg/m2 induced significantly greater immunomodulation of monocyte-associated immune parameters than 0.01 mg/m2. Changes in immunologic parameters included marked elevation of serum neopterin levels, significant increases in monocyte expression of CD64, beta 2-microglobulin, and HLA-ABC, and decreased monocyte expression of CD14. The most dramatic decreases in CD14 expression were observed on monocytes obtained from patients treated at 0.25 mg/m2. The 0.25-mg/m2 dose group had significantly lower white blood cell counts on day 14. No bell-shaped curve of immunologic response was observed over the dosage range tested. Based on the similarity of the immunologic effects at 0.1 and 0.25 mg/m2, treatment at the MTD of IFN-gamma (0.25 mg/m2) represents treatment at the OID for patients with metastatic malignant melanoma.

Adjuvants, Immunologic↗
PubMed1992

Effect of inflammation of enteric nerves. Cytokine-induced changes in neurotransmitter content and release.

The results of our previously published work provide evidence of inflammation-induced functional disturbances in the enteric nervous system. Data presented in this paper describe our preliminary results indicating that the altered function in enteric nerves in the nematode-infected rat model of intestinal inflammation is mediated by interleukin-1. This is based on the ability of the exogenous cytokine to mimic changes observed in the model, and on the ability of a specific IL-1 antagonist to attenuate these changes. In addition, we have identified mechanisms underlying the actions of IL-1 in the myenteric plexus. Our data are consistent with a direct interaction between the cytokine and neural membranes. In addition, the delayed effect of IL-1 beta on neurotransmitter release appears to be due to the release of endogenous IL-1, most likely from macrophage-like cells in the myenteric plexus (Fig. 3). If such cells possess receptors for neuropeptides, as has been found with macrophages elsewhere in the gut, a neuroimmune axis would exist in the myenteric plexus. Thus, the finding of a source of IL-1 in the plexus of the noninflamed intestine invites speculation on a neuromodulatory role of the cytokine within the enteric nervous system.

Animals↗
PubMed1991

[Optimizing the learning process in short-term autogenic training by practice protocols].

The results of two studies are presented, in which the question was investigated, whether the learning process of autogenic training (AT) in short group programs can be improved by the use of a self-control technique (records for the AT-exercises realized without the group at home). Study I refers to 24 university students, who learned AT within their psychology education; Study II refers to 28 adults, who learned AT within a psychosocial community service for adults. Within control-group designs evaluative and follow-up data were gathered before, during, at the end, and 4 months after the AT-treatment. The data refer to psychosomatic complaints (SSP, ATSYM), depression (BDI), relaxation capacity and wellbeing (VFE) as well as subjective valuations of AT and the frequency of AT-exercising. The results of both studies show that the basal AT-exercises can be learned in short group programs (6 meetings within 6 weeks). The self-control technique promotes the learning process at short as well as at longer sight. Implications of the results for the realization of introductions to AT in out- and in-patient group treatment are discussed.

Adult↗
PubMed1990

Antioxidant therapy for recurrent pancreatitis: placebo-controlled trial.

Oxidant stress has been proposed as the initiating pathogenetic mechanism in pancreatitis, hence micronutrient antioxidant therapy has been assessed in patients with recurrent attacks and/or constant pancreatic pain. In a 20-week double-blind double-dummy crossover trial active treatment was given as two types of tablets providing daily doses of 600 micrograms organic selenium, 9000 IU beta carotene, 0.54 g vitamin C, 270 IU vitamin E and 2 g methionine. Of 28 patients enrolled, 20 adhered to the full protocol (idiopathic chronic 8, alcoholic chronic 7, idiopathic acute 5). Six patients had an attack whilst on placebo but none whilst on active treatment (P = 0.032). Analysis of visual analogue scoresheets to compare background pain in the 10-week period before entry and during each phase of the trial, using a 10-cm scale for each of 11 best descriptors, endorsed the beneficial effect of active treatment (placebo v baseline, P = 0.073; active v baseline, P less than 0.001; active v placebo, P = 0.049). The same trend emerged from analysis of pain-score diaries by conventional and time series methods. Micronutrient antioxidant therapy thus offers a new approach to the treatment of recurrent (non-gallstone) pancreatitis and/or pancreatic pain.

Adolescent↗
PubMed1984

Instrumentation for measurement of dental plaque thickness in situ.

A commercial digital micrometer has been modified mechanically and electronically to allow the measurement, in situ, of the thickness of dental plaque. The device detects initial contact between a moving probe and the plaque, and measures subsequent probe displacement through to the tooth surface. Instrument accuracy is +/- 5 micron over a displacement range of 0-5 mm, with 1 micron resolution. In practice, after a short 'learning' phase, reliable clinical results can be obtained.

Biomedical Engineering↗
PubMed1983

An assessment of new dental ultraviolet sources and u.v.-polymerized fissure sealants.

The performance of six dental ultraviolet (u.v.) sources was assessed to establish minimum output requirements and possible u.v. hazards. Exposure criteria for u.v.-cured materials (Nuva-seal P.A., Nuva-cote P.A., Nuva-fil P.A., Lee-seal, u.v.-Dentoseal, Uviobond, Visiobond) were assessed by determining setting time-intensity characteristics, u.v. transmission and microhardness as a function of u.v. intensity and depth. A minimum intensity of 10 mW cm-2 was required for adequate curing and both Nuva-seal P.A. and Nuva-cote P.A. set well in depth with realistic exposures. Total u.v. outputs, average intensities and spatial distributions were assessed for the u.v. sources, most of which were well above minimum requirements. Ultraviolet spectra and maximum permissible exposure measurements indicated that all of the sources were safe in normal use.

Chemical Phenomena↗
PubMed1983

Surface treatment studies aimed at streamlining fissure sealant application.

Three laboratory studies were carried out with the aim of improving or streamlining enamel surface treatment procedures in fissure sealing. In Study 1, the effect of reducing acid etch time from 60 s to 10 s was assessed by SEM and tensile bond strength measurements. Reduction in etch time produced a finer etch pattern, gave a reduced but still high, bond-strength, albeit with slightly poorer long-term adhesion. Study 2 showed that a conventional acid etch treatment could completely remove acquired pellicle, without prior prophylaxis. SEM studies and bond-strength measurements corroborated this view. In Study 3, compressed air and chemical drying agents were compared for drying speed and efficiency. Compressed air gave more rapid, thorough drying, and greater resultant bond strengths.

Acid Etching, Dental↗