Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Statistics as Topic”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMed2003

The compliance score as a regressor in randomized trials.

The compliance score in randomized trials is a measure of the effect of randomization on treatment received. It is in principle a group-level pretreatment variable and so can be used where individual-level measures of treatment received can produce misleading inferences. The interpretation of models with the compliance score as a regressor of interest depends on the link function. Using the identity link can lead to valid inference about the effects of treatment received even in the presence of nonrandom noncompliance; such inference is more problematic for nonlinear links. We illustrate these points with data from two randomized trials.

Bias↗
PubMed2001

The effect of zigzag elastics in the treatment of Class II division 1 malocclusion subjects with hypo- and hyperdivergent growth patterns. A pilot study.

The aim of this study was to investigate the effect of zigzag elastics in the treatment of Class II division 1 malocclusion subjects with hypo- or hyperdivergent growth patterns. Two groups were established, each consisting of 10 subjects classified as hypo- or hyperdivergent according to their pre-treatment SN-GoGn angle. The cephalometric radiographs taken before and after an elastic application period of approximately 4 months were used to generate 22 variables. In both groups, there were no statistically significant differences in the vertical position of the lower molars, the SN-GoGn angle or the inclination of the lower incisors, whereas the sagittal skeletal relationship was improved as a result of an increase in the SNB angle and the mandibular length (P < 0.01). Upper incisor extrusion was statistically significant in both groups (P < 0.05). The downward rotation of the occlusal plane and the increase in overbite were found to be significant in the hypodivergent group (P < 0.05). Significant differences were observed between the groups in the extrusion of the upper incisor, the inclination of the occlusal plane, and the amount of overbite (P < 0.05). The results show that the zigzag elastic system is preferable, especially in hyperdivergent Class II division 1 subjects, as the use of such elastics does not cause an unfavourable effect on vertical jaw base relationship.

Adolescent↗
PubMed2001

An ex vivo investigation into the fluoride release and absorption profiles of three orthodontic adhesives.

Prevention of peri-bracket decalcification is essentially mediated by effective oral hygiene, which is patient dependent. The potential to compensate for poor oral hygiene may be through the release of free fluoride ions from direct bonding agents. It is well established that glass ionomer cements (GICs) release free fluoride ions which may be replenished by exposure to fluoride containing solutions. The aim of this ex vivo study was to compare the fluoride release and absorption profiles of a recently developed low fusion, monophase GIC, Limerick glass, with two materials in common clinical use, namely, Fuji-Ortho L.C. and Concise. Ten test specimens of each material were fabricated and stored in deionized water at 37 degrees C. The concentration of fluoride release was measured daily for the first 7 days after immersion and then weekly for 5 weeks. On day 42 the test specimens were recharged in 2 per cent sodium fluoride solution and fluoride release was measured initially after 24 hours and then every 48 hours. The recharge regimen was repeated for 3 weeks. Both Limerick glass and Fuji-Ortho L.C. demonstrated the characteristic fluoride release pattern of GIC with a rapid elution of fluoride after the first 24 hours followed by a more gradual release profile over the following 2 weeks. Fuji-Ortho L.C. released the greatest quantity of fluoride but the release profile of Limerick glass was more sustained. Concise released negligible amounts of fluoride. Limerick glass and Fuji-Ortho L.C. showed an increase (P < 0.01) in fluoride release following exposure to 2 per cent sodium fluoride that decreased both with time and subsequent exposures to fluoride supplement.

Absorption↗
PubMed2001

Functional regulator treatment of Class II division 1 malocclusions.

This controlled retrospective study aimed to identify the contribution of skeletal and dental changes in the correction of Class II division 1 malocclusions using Fränkel's functional regulator II (FRII), with reference to a concurrently recruited control group. One hundred and thirty-eight patients with Class II division 1 malocclusions were identified, those accepting treatment forming the study group and those declining treatment the control group. The study group (n = 70) were treated with a Fränkel appliance. Pre- and post-treatment observation cephalometric radiographs were analysed and compared. Mean values for both skeletal and dental variables in the control group were remarkably consistent throughout the study period; however, this masked individual variations in this group. The skeletal variables in the study group that showed statistically significant differences from the control group were SNB, ANB, BaNA and ANS-Me, but none of these was sufficiently large to be regarded as clinically significant. Dental variables showed clinically and statistically significant differences, including a 10 degree reduction in UI-Max and 3.1 degree increase in LI-Mand. The Fränkel appliance was thus found to be effective in producing desirable occlusal and dental changes in the majority of patients treated.

Adolescent↗
PubMed2002

Cephalometric soft tissue profile in unilateral cleft lip and palate patients.

Soft tissue profile analysis from cephalometric radiographs is recognized as an important part of the assessment of treatment outcome in cleft lip and palate (CLP), and has previously been found to discriminate between groups better than conventional hard tissue cephalometric analysis. Cephalometric radiographs of 182 12-14-year-old children from the UK with complete unilateral cleft lip and palate (UCLP) were available for this investigation, which aimed to describe the cephalometric soft tissue findings for this group of UK children. Seven soft tissue profile angular variables were measured using Dentofacial Planner Plus (DFP). Thirty films were re-measured two weeks later to assess the reliability of the method, which was acceptable for most of the variables, although use of landmarks related to the lips increased error. Mean nasolabial angle (97.44 degrees), facial convexity (138.02 degrees), and soft tissue ANB (2.99 degrees) compared unfavourably with previously reported data. These findings support the data given in the Clinical Standards Advisory Group study. Soft tissue profile assessment from cephalometric radiographs has acceptable reliability. The results of treatment show poor outcome in the UK compared with published data.

Adolescent↗
PubMed2005

Guest editorial: what do prospective randomized clinical trials tell us about the treatment of class II malocclusions? A personal viewpoint.

The prospective randomized clinical trial (RCT) is seen by many to be the 'gold standard' for analysing treatment outcome and the only valid source of clinical data. In orthodontics, most RCTs have been designed to resolve the controversy surrounding the ability of functional appliances to significantly modify dentofacial growth. Given the variability in the timing, magnitude and duration of pubertal dentofacial growth, differing levels of motivation and patient compliance, the inherent inaccuracy of cephalometry and the questionable validity of the measurements themselves used to quantitate change, it is not surprising that the conclusions have not been as clear-cut as anticipated. Unlike a laboratory experiment, in which it is possible to limit the differences between experimental and control groups to the single factor being investigated, in a clinical trial an orthodontic appliance is just one of several variables affecting the outcome. Furthermore, RCTs are expensive and time-consuming; by the time the end-point of the study has been reached, the appliance may no longer be in widespread use, the fate of more than one recent well-publicized RCT. What RCTs have shown is that functional appliances such as the Herbst and twin block, based on the principle of 'jumping the bite', are more effective at modifying dentofacial growth and reducing overjets than headgear and more passive appliances such as the Andresen activator and its variants. However, if one asks whether RCTs have achieved their objective, or provided knowledge not previously available from retrospective studies or animal experimentation, then the answer would have to be no; it is also hard to justify the cost. What is particularly interesting is that knowledge based on years of clinical experience has been disregarded and then announced as if it was something completely new.

Cephalometry↗
PubMed1996

The comparative efficacy and safety of teicoplanin and vancomycin.

Glycopeptide antibiotics, such as teicoplanin and vancomycin, are active against staphylococci (including methicillin resistant strains), streptococci, enterococci and Clostridium spp. Vancomycin and teicoplanin are both widely used in the treatment of infections caused by Gram-positive organisms. Vancomycin can, however, provoke a number of side-effects, and serum concentrations should be monitored during treatment. Teicoplanin has a longer half-life than vancomycin, it can be given as an intravenous bolus or by intramuscular injection, and nephrotoxicity and ototoxicity are relatively uncommon. Treatment with teicoplanin might, therefore, offer advantages over treatment with vancomycin-provided that similar clinical efficacy can be shown. At least 11 clinical trials comparing the efficacy and safety of teicoplanin and vancomycin have been carried out worldwide. Meta-analysis of the combined results from these studies indicates that more than three-quarters of the patients in each of the treatment groups had a clinical response to therapy. Meta-analysis of the numbers of adverse events occurring in each treatment group shows significantly fewer reports of adverse events in patients receiving teicoplanin (13.9%) than in those receiving vancomycin (21.9%). Direct comparisons are difficult because of inherent differences between studies, but available data suggest that teicoplanin is as effective as vancomycin and that its superior tolerability together with advantages such as once-daily bolus administration, intramuscular use and lack of requirement for routine serum monitoring, give it considerable potential for use in clinical practice.

Anti-Bacterial Agents↗
PubMed2002

Effectiveness of community-based salaried orthodontic services provided in England and Wales.

OBJECTIVES: To assess the effectiveness of the salaried Community Orthodontic Services in England and Wales, using occlusal indices, and to determine the predictors of treatment outcome. DESIGN: A retrospective investigation. A random stratified sample of districts where Community Orthodontic Services are provided was selected and visited during 1997. METHOD: All community orthodontists in England and Wales, and CDS managers who could be identified were asked to take part in this study. A stratified random sample of 15 per cent of the districts where community orthodontic services were provided was selected and a sample of the records of treated patients was examined. RESULTS: The orthodontists in the sample were providing treatment for patients clearly in need of treatment. There were, however, some variations between districts. Similarly, when the effectiveness of treatment in terms of dento-alveolar change was evaluated, the mean change in PAR and percentage PAR reduction was high. Again, there were variations between the districts. CONCLUSIONS: The Community Orthodontic Service provides effective orthodontic treatment to many individuals clearly in need of that treatment. The most significant predictor of treatment outcome was the use of two-arch fixed appliances, which produced the best treatment outcome

Bias↗
PubMed2002

Experimental tooth movement under light orthodontic forces: rates of tooth movement and changes of the periodontium.

AIM: To investigate light forces for experimental tooth movement. METHOD: Light orthodontic forces of 1.2, 3.6, 6.5, and 10 g force (gf) were applied for 14 days to move rat molars, and the effects of the forces on the rate of tooth movement and changes of the periodontium were examined. RESULTS: In the early period, despite the different levels of force used in each group, there were no significant differences in tooth displacement. From hour 56 to day 14, the tooth displacement in the 1.2 gf group was significantly smaller than that in the other groups and the rate was nearly constant. The rates of tooth displacement in the 3.6, 6.5, and 10 gf groups fluctuated repeatedly, while the orthodontic forces gradually decreased. CONCLUSION: Experimental tooth movement in rats, tipping without friction under light forces, were either constant or fluctuated in cycles of several days' duration. This is in contradiction to the three-phases-theory of tooth movement described in previous investigations using heavy forces.

Alveolar Process↗
PubMed2002

Recent trends in National Institutes of Health funding of surgical research.

OBJECTIVE: To compare the amount of National Institutes of Health (NIH) funding provided to departments of surgery with that provided to other major clinical departments, to examine the relationship between peer-review activity and funding success, and to compare trends in participation in the peer-review process between surgeons and representatives from other clinical departments. SUMMARY BACKGROUND DATA: Surgical research has made enormous contributions to human health. This work is fundamentally dependent on fair and unbiased distribution of extramural research funds from the NIH. To date, no published report has examined the relative distribution of extramural support between departments of surgery and other major clinical departments. METHODS: Data regarding funding trends and peer-review activity were obtained from the NIH and compared between departments of surgery and four nonsurgical departments (medicine, psychiatry, pediatrics, neurology). Award data were examined during 1996 to 2001. Participation trends were examined during 1998 to 2000. RESULTS: Success rates of surgical proposals were significantly lower than nonsurgical proposals. Differentials in success rates were greatest for proposals assigned to the National Cancer Institute, although relative underfunding for surgical research spanned all major institutes. Awards for surgical grants averaged 5% to 27% less than nonsurgical grants). Surgeons exhibited 35% to 65% less peer-review activity relative to nonsurgeons when normalized to grant submission activity. Overall, surgeons participated on sections where they made up a relatively smaller proportion of total review members compared to nonsurgeons. CONCLUSIONS: Surgical grant proposals are less likely to be funded and carry significantly smaller awards compared to nonsurgical proposals. Relatively fewer surgeons participate in the review process, and those who do are more likely to be in the minority within study sections. Multiple strategies are needed to address these trends and level the playing field for surgical research.

General Surgery↗
PubMed2000

The reliability and variability of SN and PFH reference planes in cephalometric diagnosis and therapeutic planning of dentomaxillofacial malformations.

Various interpretations of clinical and cephalometric data lead to different diagnostic and surgical planning in the study of dentoskeletal malformations. Many authors have identified this discrepancy as an incorrect positioning between the skeletal structures and the Frankfurt plane (PFH)--a plane that is used routinely for the sagittal measurement of the upper and lower jaw. The aim of this study was to establish a control method to verify the correct positioning of the sella-nasion point plane (SN) and the PFH. To find a reference plane, the authors concentrated their attention on measuring the intersecting angles between these two planes and the vertical posterior maxillary (PM) plane. Fifty patients (33 women and 17 men), all of whom were aesthetically and structurally harmonious class I dentoskeletal types, were analyzed using this method. Student's t-test, the Kolmogorov-Smirnov test, and Fisher's F-test were used for statistical analysis. The results were compared with those proposed by the University of Michigan. To achieve a correct diagnosis and to obtain good functional and cosmetic results in the treatment of these kinds of malformations, it is necessary to make use of the PM vertical plane during cephalometric analysis.

Adolescent↗