[ accuracy of linear tomography in mandibular width determination in superior border of mandibular canal]

Finding an accurate and inexpensive method in measurement of bone width for determination of implant size is critical. Linear tomography is a cost effective method and there is no accurate finding about accuracy of linear tomography in evaluation of mandibular wide. The purpose of this study was to determine the accuracy of linear tomography in estimation of mandibular width. In this diagnostic study [estimation of one method], 23 sites of four dry mandibles were selected and marked at the crest with a metal ball markers. After linear tomography in these sites, the width of mandible in the superior border of inferior alveolar canal was measured. The mandibles were then sectioned. The Pearson's rank order correlation coefficient between linear tomography and real values was determined. Then with estimation of mean absolute differences by magnification factor, the percentages of errors in +/- 1mm error limits were determined. The regression equation was written for better determination of agreement rate between radiographic and real values. The percentages of errors in +/- 1 mm error limits were determined. The Pearson's rank order correlation coefficient between the linear tomography and real values was 0.813 [P<0.0001]. The mean absolute differences between the mandibular width in tomographic sections and real values was 0.3 mm [SD=1.13] and 56.5% of width measurements were within the +/- 1mm error limits. By the resulting linear regression equation 51.8% of tomographic values were located within the +/- 1mm error limits. Linear tomography in evaluation of mandibular width should be used more cautiously

[Accuracy and validity of spiral conventional tomography in assessment of mandibular implant recipient sites: an in-vitro study]

Conventional tomography is a cross sectional imaging modality that provides information about the width of the alveolar bone and the position of the critical anatomical structures such as mandibular canal in the lower jaw. In comparison with conventional CT, it is less expensive, more accessible and patients are exposed to much less radiation. The purpose of this study was to compare the accuracy and validity of spiral computed tomography and spiral conventional tomography. Ten fully or partially edentulous cadaver mandibles were selected. The specific points in anterior, canine, premolar, and molar regions were selected and imagings were performed with both radiographic systems. The distance between alveolar crest to superior border of mandibular canal, as well as mandibular height and width were measured by one oral and maxillofacial radiologist in two successive sessions. The tomography and CT scan [as gold standard] measurements were compared. This evaluation revealed that the absolute mean differences in measuring the vertical dimension in the anterior, canine, premolar, and molar regions were 1.43, 0.74, 0.87, and 0.81 millimeters respectively. The horizontal dimension measurements were 1.21, 0.92, 0.76, and 0.82 millimeters respectively. The absolute mean differences in measuring the vertical and horizontal dimensions were 0.65 and 0.91 millimeters respectively. All these measurements were with in limits of +/- 1 mm error except in the anterior region. Both measurements of vertical and horizontal dimensions had the tendency to be underestimated in anterior region. In measuring the vertical and horizontal dimensions, the validity of spiral conventional tomography were 90.49% and 73.02% respectively, and both were statistically significant [P < 0.001]. From the results of present study it can be concluded that the spiral conventional tomography is an accurate and reliable technique for measuring the vertical and horizontal dimensions in mandible

[Qualitative assessment of dimensions and degree of autonomy granting to university hospitals]

The aim of this study was to determine the key organizational dimensions that influence the autonomy of university hospitals and the level of granted autonomy in each dimension. Six hospitals were randomly selected from those affiliated with three medical universities of Tehran, Iran and Shahid Beheshti. In this qualitative study, we interviewed 27 hospital managers [response rate of 82%]. The semi-structured interview guide was developed based on the results of four initial in-depth interviews and the organizational reform model of the World Bank. We used the framework method for the analysis of qualitative data. Nine themes were identified as the key factors influencing hospital autonomy: decision right in strategic management, decision right in human resources management, decision right in financial management, decision right in physical resources management, product market exposure, procurement market exposure, financial residual claim, governance arrangements and accountability mechanisms, and social functions of the hospitals. Limited decision rights in strategic, human resources, and physical resources management were granted to hospitals. Hospitals were not the financial residual claimant, but were exposed to competitive product market. Autonomy was limited regarding the procurement market. Governance systems were hierarchical and accountability mechanisms were supervisor-supervisee oriented. Some of the social functions of the hospitals were defined, but the expenses of these functions were not totally reimbursed by the government and the insurance industry. The autonomy granted to the hospitals is unbalanced and paradoxical. More decision rights should be granted for management of strategic, human resources and physical resources as well as hospitals entry to the procurement market. Hospitals need to be the financial residual claimant. The hierarchical administrative systems should be transformed to cooperative ones. Instead of supervisor-supervisee oriented control measures, Ministry of Health and Medical Education needs more regulatory mechanisms for controlling hospitals' performance and social functions

Direct estimation of life expectancy for population of Iran in year 2003

Life expectancy is one of the summary measures of population health, whose values and trend of changes over time show the main outcome of health system performance. Estimation of life expectancy is performed with direct or model-based methods. In this study direct estimation of life expectancy for Iran's population in year 2003 is performed. In an ecologic study, for calculation of abridged period life table for 23 out of 28 provinces of Iran in year 2003, numbers of registered deaths for age and sex specific groups in these 23 provinces by death registration system of Ministry of Health [MOH] were used. Undernumeration of over-four year's deaths was estimated and corrected with Brass Growth-Balance method. For mortality rates of under-one and 1-4 years, similar rates from Demographic and Health Survey [DHS] 2000 with live births denominators were substituted. For total number of population of 23 provinces, information from MOH was used. Distribution of population by age and sex was taken similar to that from DHS 2003 results, and also taken as result of graduation of whole country population from 1375 census. Population of these 23 provinces was equal to 73% of total population of country in year 2003. Life expectancy was estimated by age and sex with the obtained population and death numbers. It was assumed that distributions of population and death in 23 provinces were similar to those for the whole 28 provinces of Iran in year 2003 and hence, the estimated life expectancy for 23 provinces is equal to that for all 28 provinces in 2003. Sensitivity of the results to assumptions was analyzed. Confidence intervals were calculated with Monte Carlo method. Life expectancy at birth was estimated as 71.56 years for total population [95% CI: 71.52 - 71.62], 70.09 years for males [70.02 - 70.16], and 73.17 [73.10 - 73.24] for females of Iran in year 2003. Sensitivity of results to assumptions was less than 0.5%. Values of life expectancy estimates for year 2003 with direct method are higher than those based on statistical modeling approaches performed by Statistical Center of Iran and by different United Nations agencies, due to difference in estimation methods for age and sex specific mortality rates

[Ischemic and reperfusion injury of adult rat sciatic nerve]

Ischemia plays a major role in development of pathological changes in various neuropathies. Reperfusion amplifies physiological and pathological abnormalities in ischemic nerves. In this research, we studied ischemic-reperfusion [IR] injury of sciatic nerve up to 14 days of reperfusion. IR was produced by ligation and release of nooses around supplying vessels to the sciatic nerve. 30 rats were assigned into 5 groups of 6. Group 1 [control] did not undergo IR while the 4 remaining groups after three hours of complete hind leg ischemia underwent reperfusion within 0hr, 3hrs, 7 days and 14 days. Pathologically, two phases were identifiable. During phase 1 [0-3 hrs] fiber degeneration and endoneurial edema were observed. During phase 2 [7 days and, 14 days] prominent fiber degeneration and prominent endoneurial edema were observed. Loss of function occurred in more than 75% of the rats with ischemia alone, in comparison with the control group the maximum reduction in activities was observed amongst the group of rats reperfused within 3 hours. IR injury depends on duration of reperfusion. Microvascular events during reperfusion may enhance the nerve fiber damage following the ischemia period

Effectiveness of adolescents' immunization against hepatitis B on burden of the disease in Iran

Hepatitis B is a common problem in many countries. Due to high efficacy, safety and low cost of vaccine, mass immunization has become a favorite strategy to improve population health. In this study, we tried to estimate marginal effectiveness of adolescents' immunization program in Iran. Epidemiologic data about of hepatitis B in Iran was gathered through literature review, expert opinion, existing resources of data and synthesis by modeling of other data. In a state transition model, different stages of disease were simulated in 15 to 100 year old individuals. Comparing the results of burden of hepatitis B with and without immunization revealed an estimate of avoidable burden of disease with intervention. Monte Carlo simulation and sensitivity analyses were done for uncertainty analysis of results. Immunization of around one million 15-year, old males and females prevents 2071 of male and 581 of female premature deaths due to acute hepatitis B, cirrhosis and hepatocellular carcinoma annually. Moreover, it prevents loss of about 52 and 36 percent of YLL [years of life lost] due to hepatitis B complications in males and females respectively. On average, it avoids loss of Disability Adjusted Life Years [DALY] of 0.012 and 0.006 years, according to present value of life. Monte Carlo simulation of populations showed that effectiveness of the intervention is quite significant and about half of males and one third of females with disability, equal to at least one year of full health, will be free. With sensitivity analyses, results were standing in acceptable limit of values in both bivariate and probabilistic calculations. Our study showed that effectiveness of adolescents' immunization against hepatitis B is quite significant. Calculation using basic estimates of cost of intervention program implies that this intervention is possibly very cost effective. For final judgment, results should be combined with cost effectiveness analysis, and compared to other interventions