Global fertility in 204 countries and territories, 1950-2021, with forecasts to 2100: a comprehensive demographic analysis for the Global Burden of Disease Study 2021

BACKGROUND

Accurate assessments of current and future fertility-including overall trends and changing population age structures across countries and regions-are essential to help plan for the profound social, economic, environmental, and geopolitical challenges that these changes will bring. Estimates and projections of fertility are necessary to inform policies involving resource and health-care needs, labour supply, education, gender equality, and family planning and support. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 produced up-to-date and comprehensive demographic assessments of key fertility indicators at global, regional, and national levels from 1950 to 2021 and forecast fertility metrics to 2100 based on a reference scenario and key policy-dependent alternative scenarios.

METHODS

To estimate fertility indicators from 1950 to 2021, mixed-effects regression models and spatiotemporal Gaussian process regression were used to synthesise data from 8709 country-years of vital and sample registrations, 1455 surveys and censuses, and 150 other sources, and to generate age-specific fertility rates (ASFRs) for 5-year age groups from age 10 years to 54 years. ASFRs were summed across age groups to produce estimates of total fertility rate (TFR). Livebirths were calculated by multiplying ASFR and age-specific female population, then summing across ages 10-54 years. To forecast future fertility up to 2100, our Institute for Health Metrics and Evaluation (IHME) forecasting model was based on projections of completed cohort fertility at age 50 years (CCF50; the average number of children born over time to females from a specified birth cohort), which yields more stable and accurate measures of fertility than directly modelling TFR. CCF50 was modelled using an ensemble approach in which three sub-models (with two, three, and four covariates variously consisting of female educational attainment, contraceptive met need, population density in habitable areas, and under-5 mortality) were given equal weights, and analyses were conducted utilising the MR-BRT (meta-regression-Bayesian, regularised, trimmed) tool. To capture time-series trends in CCF50 not explained by these covariates, we used a first-order autoregressive model on the residual term. CCF50 as a proportion of each 5-year ASFR was predicted using a linear mixed-effects model with fixed-effects covariates (female educational attainment and contraceptive met need) and random intercepts for geographical regions. Projected TFRs were then computed for each calendar year as the sum of single-year ASFRs across age groups. The reference forecast is our estimate of the most likely fertility future given the model, past fertility, forecasts of covariates, and historical relationships between covariates and fertility. We additionally produced forecasts for multiple alternative scenarios in each location: the UN Sustainable Development Goal (SDG) for education is achieved by 2030; the contraceptive met need SDG is achieved by 2030; pro-natal policies are enacted to create supportive environments for those who give birth; and the previous three scenarios combined. Uncertainty from past data inputs and model estimation was propagated throughout analyses by taking 1000 draws for past and present fertility estimates and 500 draws for future forecasts from the estimated distribution for each metric, with 95% uncertainty intervals (UIs) given as the 2·5 and 97·5 percentiles of the draws. To evaluate the forecasting performance of our model and others, we computed skill values-a metric assessing gain in forecasting accuracy-by comparing predicted versus observed ASFRs from the past 15 years (2007-21). A positive skill metric indicates that the model being evaluated performs better than the baseline model (here, a simplified model holding 2007 values constant in the future), and a negative metric indicates that the evaluated model performs worse than baseline.

FINDINGS

During the period from 1950 to 2021, global TFR more than halved, from 4·84 (95% UI 4·63-5·06) to 2·23 (2·09-2·38). Global annual livebirths peaked in 2016 at 142 million (95% UI 137-147), declining to 129 million (121-138) in 2021. Fertility rates declined in all countries and territories since 1950, with TFR remaining above 2·1-canonically considered replacement-level fertility-in 94 (46·1%) countries and territories in 2021. This included 44 of 46 countries in sub-Saharan Africa, which was the super-region with the largest share of livebirths in 2021 (29·2% [28·7-29·6]). 47 countries and territories in which lowest estimated fertility between 1950 and 2021 was below replacement experienced one or more subsequent years with higher fertility; only three of these locations rebounded above replacement levels. Future fertility rates were projected to continue to decline worldwide, reaching a global TFR of 1·83 (1·59-2·08) in 2050 and 1·59 (1·25-1·96) in 2100 under the reference scenario. The number of countries and territories with fertility rates remaining above replacement was forecast to be 49 (24·0%) in 2050 and only six (2·9%) in 2100, with three of these six countries included in the 2021 World Bank-defined low-income group, all located in the GBD super-region of sub-Saharan Africa. The proportion of livebirths occurring in sub-Saharan Africa was forecast to increase to more than half of the world's livebirths in 2100, to 41·3% (39·6-43·1) in 2050 and 54·3% (47·1-59·5) in 2100. The share of livebirths was projected to decline between 2021 and 2100 in most of the six other super-regions-decreasing, for example, in south Asia from 24·8% (23·7-25·8) in 2021 to 16·7% (14·3-19·1) in 2050 and 7·1% (4·4-10·1) in 2100-but was forecast to increase modestly in the north Africa and Middle East and high-income super-regions. Forecast estimates for the alternative combined scenario suggest that meeting SDG targets for education and contraceptive met need, as well as implementing pro-natal policies, would result in global TFRs of 1·65 (1·40-1·92) in 2050 and 1·62 (1·35-1·95) in 2100. The forecasting skill metric values for the IHME model were positive across all age groups, indicating that the model is better than the constant prediction.

INTERPRETATION

Fertility is declining globally, with rates in more than half of all countries and territories in 2021 below replacement level. Trends since 2000 show considerable heterogeneity in the steepness of declines, and only a small number of countries experienced even a slight fertility rebound after their lowest observed rate, with none reaching replacement level. Additionally, the distribution of livebirths across the globe is shifting, with a greater proportion occurring in the lowest-income countries. Future fertility rates will continue to decline worldwide and will remain low even under successful implementation of pro-natal policies. These changes will have far-reaching economic and societal consequences due to ageing populations and declining workforces in higher-income countries, combined with an increasing share of livebirths among the already poorest regions of the world.

FUNDING

Bill & Melinda Gates Foundation.

Global, regional, and national incidence and mortality burden of non-COVID-19 lower respiratory infections and aetiologies, 1990-2021: a systematic analysis from the Global Burden of Disease Study 2021

BACKGROUND

Lower respiratory infections (LRIs) are a major global contributor to morbidity and mortality. In 2020-21, non-pharmaceutical interventions associated with the COVID-19 pandemic reduced not only the transmission of SARS-CoV-2, but also the transmission of other LRI pathogens. Tracking LRI incidence and mortality, as well as the pathogens responsible, can guide health-system responses and funding priorities to reduce future burden. We present estimates from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 of the burden of non-COVID-19 LRIs and corresponding aetiologies from 1990 to 2021, inclusive of pandemic effects on the incidence and mortality of select respiratory viruses, globally, regionally, and for 204 countries and territories.

METHODS

We estimated mortality, incidence, and aetiology attribution for LRI, defined by the GBD as pneumonia or bronchiolitis, not inclusive of COVID-19. We analysed 26 259 site-years of mortality data using the Cause of Death Ensemble model to estimate LRI mortality rates. We analysed all available age-specific and sex-specific data sources, including published literature identified by a systematic review, as well as household surveys, hospital admissions, health insurance claims, and LRI mortality estimates, to generate internally consistent estimates of incidence and prevalence using DisMod-MR 2.1. For aetiology estimation, we analysed multiple causes of death, vital registration, hospital discharge, microbial laboratory, and literature data using a network analysis model to produce the proportion of LRI deaths and episodes attributable to the following pathogens: Acinetobacter baumannii, Chlamydia spp, Enterobacter spp, Escherichia coli, fungi, group B streptococcus, Haemophilus influenzae, influenza viruses, Klebsiella pneumoniae, Legionella spp, Mycoplasma spp, polymicrobial infections, Pseudomonas aeruginosa, respiratory syncytial virus (RSV), Staphylococcus aureus, Streptococcus pneumoniae, and other viruses (ie, the aggregate of all viruses studied except influenza and RSV), as well as a residual category of other bacterial pathogens.

FINDINGS

Globally, in 2021, we estimated 344 million (95% uncertainty interval [UI] 325-364) incident episodes of LRI, or 4350 episodes (4120-4610) per 100 000 population, and 2·18 million deaths (1·98-2·36), or 27·7 deaths (25·1-29·9) per 100 000. 502 000 deaths (406 000-611 000) were in children younger than 5 years, among which 254 000 deaths (197 000-320 000) occurred in countries with a low Socio-demographic Index. Of the 18 modelled pathogen categories in 2021, S pneumoniae was responsible for the highest proportions of LRI episodes and deaths, with an estimated 97·9 million (92·1-104·0) episodes and 505 000 deaths (454 000-555 000) globally. The pathogens responsible for the second and third highest episode counts globally were other viral aetiologies (46·4 million [43·6-49·3] episodes) and Mycoplasma spp (25·3 million [23·5-27·2]), while those responsible for the second and third highest death counts were S aureus (424 000 [380 000-459 000]) and K pneumoniae (176 000 [158 000-194 000]). From 1990 to 2019, the global all-age non-COVID-19 LRI mortality rate declined by 41·7% (35·9-46·9), from 56·5 deaths (51·3-61·9) to 32·9 deaths (29·9-35·4) per 100 000. From 2019 to 2021, during the COVID-19 pandemic and implementation of associated non-pharmaceutical interventions, we estimated a 16·0% (13·1-18·6) decline in the global all-age non-COVID-19 LRI mortality rate, largely accounted for by a 71·8% (63·8-78·9) decline in the number of influenza deaths and a 66·7% (56·6-75·3) decline in the number of RSV deaths.

INTERPRETATION

Substantial progress has been made in reducing LRI mortality, but the burden remains high, especially in low-income and middle-income countries. During the COVID-19 pandemic, with its associated non-pharmaceutical interventions, global incident LRI cases and mortality attributable to influenza and RSV declined substantially. Expanding access to health-care services and vaccines, including S pneumoniae, H influenzae type B, and novel RSV vaccines, along with new low-cost interventions against S aureus, could mitigate the LRI burden and prevent transmission of LRI-causing pathogens.

FUNDING

Bill & Melinda Gates Foundation, Wellcome Trust, and Department of Health and Social Care (UK).

Global, regional, and national burden of disorders affecting the nervous system, 1990-2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND

Disorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.

METHODS

We estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.

FINDINGS

Globally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378-521), affecting 3·40 billion (3·20-3·62) individuals (43·1%, 40·5-45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7-26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6-38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5-32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7-2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.

INTERPRETATION

As the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed.

FUNDING

Bill & Melinda Gates Foundation.

Success rates of single-thread and double-thread orthodontic miniscrews in the maxillary arch

AIM

There is limited research on the clinical performance of double-thread orthodontic miniscrews. This study aimed to compare the stability of double-thread and single-thread orthodontic miniscrews and identify the potential associations between patient-related and location-related factors with miniscrew stability.

METHODS

This retrospective cohort study involved 90 orthodontic miniscrews (45 single-thread, 45 double-thread) with identical dimensions (8 mm length, 1.6 mm diameter). The screws were inserted in various locations within the upper jaw of 83 patients (54 females, 29 males; mean age = 15.1 ± 2.4 years). Failure was defined as excessive mobility or loss of miniscrew after placement. The data recorded were patient age, gender, insertion site, side of insertion (buccal or lingual), duration of force application, and failure occurrence.

RESULTS

The overall success rate within the sample was 92.2%. Double-thread miniscrews exhibited a significantly higher success rate than single-thread miniscrews (P = 0.049), with 97.8% and 86.7% success rates, respectively. Gender, age, insertion location, and side of insertion did not show significant associations with failure (P > 0.05). Log-rank analysis revealed a significant difference between the two groups (P = 0.046), indicating a higher probability of survival for the double-thread design.

CONCLUSIONS

The overall success rate of orthodontic miniscrews was high in the present sample. Double-thread miniscrews placed in various locations within the maxillary arch demonstrated superior stability and survival rates compared to their single-thread counterparts. Therefore, double-thread miniscrews may be preferred when bone quality is inadequate, such as in young patients.

Comparison of epidemiologic features between upper and lower limb injuries and risk factors for intensive care unit admission in a university hospital affiliated with the National Trauma Registry of Iran

PURPOSE

Upper extremity injuries (UEIs) and lower extremity injuries (LEIs) constitute a considerable component of traumas. However, their epidemiologic differences and short-term in-hospital outcomes are not fully elucidated. This study aims to compare such discrepancies in a large-scale study.

METHODS

In this retrospective study, all patients with UEIs and/or LEIs hospitalized from 24th July 2016 to 16th May 2020 in Sina Hospital, Tehran, Iran, and registered at the National Trauma Registry of Iran were enrolled in the study. Relevant demographic and clinical characteristics were extracted from the National Trauma Registry of Iran database. Patients were grouped into either UEI or LEI. For those with concomitant UEIs and LEIs, the more severe one based on the abbreviated injury scale was defined as the principal diagnosis. In addition, cases with the abbreviated injury scale > 3 for both UEI and LEI or concomitant injuries to body areas other than the limbs were excluded. Independent samples t-test, Mann-Whitney U test, Chi-square test, quintile regression models, and logistic regression models with "margins" command were used for statistical analyses, as indicated.

RESULTS

In this research, 3170 eligible cases were identified. For the LEI group, there was a much higher proportion of male patients (86.7% vs. 82.0%) and higher mean age (years, 42.9 vs. 35.3) compared to the UEI group (both p < 0.001). Patients with an injury severity score (ISS) of 9 - 15 were outnumbered in the LEI group (22.9% vs. 1.6%, p < 0.001), while the proportion of those with an ISS < 9 was higher in the UEI group (98.1% vs. 76.8%, p < 0.001). The multiple logistic regression model showed a statistically significant association between intensive care unit (ICU) admission and ISS (odds ratio (OR) = 4.01 for ISS 9 - 15 vs. ISS <9, 95% confidence interval (CI)|: 3.01 - 5.35; OR = 17.65 for ISS ≥16 vs. ISS < 9, 95% CI: 4.03 - 77.27), age (OR = 1.02, 95% CI: 1.01 - 1.03), cause of injury (OR = 0.27 for blunt trauma vs. road traffic crash, 95% CI: 0.08 - 0.90; OR = 0.49 for cut/stab injuries vs. road traffic crash, 95% CI: 0.28 - 0.84) and body region (OR = 1.65 for lower extremity, 95% CI: 1.19 - 2.29). Having adjusted for other covariates, the odds of ICU admission in patients with LEIs was 1.65 times the odds in patients with UEIs.

CONCLUSIONS

Patients with LEIs were older and suffered from more severe injuries. In addition, the age- and ISS-adjusted ICU admission and length of hospital stay were significantly higher in LEI patients. The chance of ICU admission was associated with age, cause of injury, ISS, and body region. The findings of this study can aid in the meticulous selection of ICU-candidate patients. In addition, the role of factors other than ISS and age in ICU admission and prolongation of hospitalization should be addressed by prospective studies.

Introducing a User-Friendly Technique for Treatment of Palatally-Impacted Canines with the Aid of Temporary Anchorage Devices

Treatment of impacted canine teeth is a challenge for most clinicians, especially in adult patients with high risk of ankylosis. Conventionally, leveling and alignment of the teeth are first performed and after heavy arch wire placement in slot of brackets, de-impaction force is applied. However, this method has some disadvantages, such as inability to detect ankylosis of the impacted tooth until load application, risk of root resorption of incisors or necrosis of them, distortion of dental arch form, the need for early extraction of primary canines, which is esthetically unfavorable for patients, and long-term presence of fixed orthodontic appliances in the oral cavity. This study aims to introduce approach that can be easily used by busy clinicians to guide palatally impacted canines into the dental arch using a cantilever spring supported by two palatal miniscrews prior to the initiation of fixed orthodontic treatment, and report some cases treated with this technique. This technique does not have the shortcomings of the conventional technique. In addition, the total duration of treatment, and duration of presence of orthodontic appliances in the oral cavity are shorter than the conventional technique. In addition, is less technique sensitive and do not need time complex and time consuming wire bending.

Design of an effective piezoelectric microcantilever biosensor for rapid detection of COVID-19

Acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also called COVID-19, is one of the most contagious viruses resulting in a progressive pandemic. Since specific antiviral treatments have not been developed yet and its fatal rate is almost high, early and fast detection is critical for controlling the outbreak. In this study, a piezoelectric microcantilever biosensor has been designed for detecting COVID-19 samples directly without requiring preparation steps. The biosensor acts as a transducer and is coated with the related antibody. When the SARS-CoV-2 antigens adsorbed on the microcantilever top surface through their spike proteins, a surface stress due to the mass change would be prompted leading to the measurable tip deflection and floating voltage. To obtain a biosensor with optimum parameters, different shapes and piezoelectric materials have been assessed and it was concluded that a Poly (vinylidene fluoride) (PVDF) biosensor in a shape of a holed punched form triangle, represented the best result. Therefore, the highly sensitive microcantilever biosensor can detect COVID-19 in clinical samples with various viral loads, rapidly. Also, it is selective enough to differentiate SARS-CoV-2 from other viruses with similar symptoms.

Radiologic evaluation of the mastoid segment of the facial nerve tract in the intact temporal bone

PURPOSE

To localize the facial nerve course in the mastoid segment and to measure its distances relative to the tympanic membrane.

METHODS

This is a cross-sectional descriptive study. During 2019 in a tertiary hospital, 129 non-contrast and non-pathologic temporal CT images were studied in a tertiary hospital. Facial nerve distances were measured from the planes passing through the annulus in the axial cross-sections at superior, umbo, and inferior levels of the tympanic membrane. It was done in two different dimensions which are anteroposterior (toward the plane of the ear canal wall) and mediolateral (toward the plane of the tympanic membrane).

RESULTS

The least mean anteroposterior distance between the facial nerve and the posterior ear canal wall was at the level of umbo (3.66 ± 0.76 mm). The nearest point of the nerve toward the tympanic membrane was the inferior level (- 0.03 ± 0.81 mm). Overall external ear canal lengths were statistically significantly lower in women rather than men. There was a reverse correlation between the age and the ear canal length.

CONCLUSION

Posterior canalplasty seems to be safe unless dissection does not cross the plane of annulus. In this study, the safe margin was 1.4 mm in posterior canal wall drilling. It also should be performed carefully if it extends to the inferior side of the canal. Measuring the mediolateral dimension of the nerve toward the annulus in the axial CT images seems to be practically beneficial, especially in the inferior where the ear canal wall turns and might not act as a good landmark. Paying attention to this plane may reduce the risks of nerve injury in any procedures with transcanal approaches, particularly in inferior canaloplasty.

The effect of canine disimpaction performed with temporary anchorage devices (TADs) before comprehensive orthodontic treatment to avoid root resorption of adjacent teeth

Objective:

The aim of this study was to evaluate the movement of impacted canines away from the roots of neighboring teeth before full-mouth bracket placement, performed by means of TADs to decrease undesired side effects on adjacent teeth.

Methods:

The study sample consisted of 34 palatally impacted canines, being 19 in the experimental group and 15 in the control group. In the experimental group, before placement of brackets, the impacted canine was erupted by means of miniscrews. In the control group, after initiation of comprehensive orthodontics, canine disimpaction was performed by means of a cantilever spring soldered to a palatal bar. At the end of treatment, volume of lateral incisors and canine root resorption were measured and compared by means of a CBCT-derived tridimensional model. Visual Analogue Scale (VAS) score, bleeding on probing (BOP) and gingival index (GI) were recorded. Clinical success rate was also calculated.

Results:

The volume of root resorption of lateral teeth in the control group was significantly greater than in the experimental group (p < 0.001). At the end of treatment, VAS score, GI and BOP were not significantly different between the two groups.

Conclusion:

Based on our results, it seems that disimpaction of canines and moving them to the arch can be done successfully carried out with minimal side effects by means of skeletal anchorage.

Validation of Histologic Bone Analysis Following Microfil Vessel Perfusion

The ability to examine bone vascularity using Micro-Computed Tomography (μCT) following vessel perfusion with Microfil^® and to subsequently perform histologic bone analysis in the same specimen would provide an efficient method by which the vascular and cellular environment of bone can be examined simultaneously. The purpose of this report is to determine if the administration of Microfil^® precludes accurate histologic assessment of bone quality via osteocyte count and empty lacunae count. Sprague-Dawley rats (n=6) underwent perfusion with Microfil^®. Left hemi-mandibles were harvested, decalcified and underwent vascular analysis via μCT prior to sectioning and staining with Gomori's Trichrome. Quantitative Histomorphometric evaluation was performed. Ninety-five percent confidence intervals were used to determine statistical differences from an established set of controls (n=12). Histologic analyses were successfully performed on specimens that had undergone previous perfusion. Quantitative measures of bone cellularity of perfused versus control specimens revealed no statistical difference in osteocyte count per high-power field (95.33 versus 94.66; 95 percent CI,-7.64 to 6.30) or empty lacunae per high-power field (2.73 versus 1.89, 95 percent CI, -1.81 to 0.13). Here we report a statistical validation allowing for histological analysis of cell counts in specimens in which Microfil^® perfusion has previously been performed.

DNA damage in oral mucosa cells of patients with fixed orthodontic appliances

OBJECTIVE

The release of toxic metal ions from orthodontic alloys has induced concerns regarding the biocompatibility of fixed appliances. This study investigated the genotoxic effect of metal appliances in a sample of patients undergoing fixed orthodontic treatment.

MATERIALS AND METHODS

The study included twenty-five healthy individuals requiring orthodontic therapy in both jaws. The patients were treated by stainless steel orthodontic brackets and nickel-titanium or stainless steel arch wires. The oral mucosa cells were gathered just before the appliance placement and 9 months later. The cells were centrifuged, fixed and dropped onto slides. After staining, the micronucleus (MN) assay was used to determine genome alteration. The data were analyzed by paired sample t-test.

RESULTS

The mean micronuclei frequency in the buccal mucosa was 10.6 ± 5.7 per 1000 cells before the appliance placement and 9.2 ± 6.37 per 1000 cells 9 months later. No significant difference was found in the MN count before and 9 months after therapy (p=0.336).

CONCLUSION

Under the conditions used in this study, application of fixed orthodontic appliances did not expose healthy individuals to increased risk of DNA damage in oral mucosa cells.

In-vitro evaluation of an experimental method for bonding of orthodontic brackets with self-adhesive resin cements

BACKGROUND

Self-adhesive resin cements do not require the surface treatment of teeth and are said to release fluoride, which makes them suitable candidates for bonding of orthodontic brackets. The objectives of this study was to investigate the shear bond strength (SBS) of self-adhesive resin cements on etched on non-etched surfaces in vitro and to assess their fluoride release features.

MATERIALS AND METHODS

Four fluoride-releasing dual-cure self-adhesive resin cements were investigated. For SBS experiment, 135 freshly extracted human maxillary premolars were used and divided into nine groups of 15 teeth. In the control group, brackets were cemented by Transbond XT (3M Unitek, USA), in four groups self-adhesive resin cements were used without acid-etching and in four groups self-adhesive cements were applied on acid-etched surfaces and the brackets were then deboned in shear with a testing machine. Adhesive remnant index (ARI) scores were also calculated. For fluoride release investigation, 6 discs were prepared for each self-adhesive cement. Transbond XT and Fuji Ortho LC (GC, Japan) served as negative and positive control groups, respectively. The fluoride release of each disc into 5 ml of deionized water was measured at days 1, 2, 3, 7, 14, 28, and 56 using a fluoride ion-selective electrode connected to an ion analyzer. To prevent cumulative measurements, the storage solutions were changed daily.

RESULTS

The SBS of brackets cemented with Transbond XT were significantly higher compared to self-adhesives applied on non-etched surfaces (P<0.001). However, when the self-adhesive resin cements were used with enamel etching, no significant differences was found in the SBS compared to Transbond XT, except for Breeze. The comparisons of the ARI scores indicated that bracket failure modes were significantly different between the etched and non-etched groups. All self-adhesive cements released clinically sufficient amounts of fluoride for an extended period of time.

CONCLUSION

For the tested cements, the strongest bonds were obtained by enamel acid-etching prior to bracket bonding. All the self-adhesive resin cements had significant long-term fluoride release and could be recommended as suitable fluoride-releasing orthodontic bonding materials.

Mast cells density in fibrotic capsule of enchondroma and well-differentiated chondrosarcoma: a method for histopathologic differentiation

BACKGROUND

An enchondroma is a benign and a well-differentiated chondrosarcoma is an invasive chondroid tumor with high recurrence potential. In spite of biologic differences, these two tumors have very similar histopathologic appearance. It has been shown that the biologic nature of the connective tissue around benign and malignant tumors varies in the number of mast cells. The aim of this study was to study the histopathologic distinction of enchondroma and well-differentiated chondrosarcoma using the density of the mast cells in fibrotic capsule.

METHODS

Twelve enchondroma and 15 well-differentiated chondrosarcoma were collected from Pathology department of Cancer Institute and Central Pathology department of Imam Khomeini Hospital in Tehran. 3 micron paraffin embedded tissue sections were stained by toluidine blue for mast cells counting. Mast cells were counted in fibrous capsule of all cases. Mast cells counts were accomplished in 10 high power fields. The average number of mast cells in 10HPF was determined as an index for each lesion. Mann-Whitney U test was used for statistical analysis.

RESULTS

Mean index in enchondroma and well-differentiated chondrosarcoma groups were 0.1±0.12 and 0.31±0.33 respectively, showing a significant difference between number of mast cells in the fibrotic capsule in these two lesions (p = 0.028). Comparison of the corresponding points in ROC curve, showed a cut-off point = 0.15, with positive predictive value of 61%, negative predictive value 71%, specificity of 33.3% and sensitivity of 66.7%, (p = 0.025).

CONCLUSION

Average density of the mast cells in the surrounding fibrotic capsules of enchondroma and well-differentiated chondrosarcoma along with other criterions, could be a beneficial factor for histologically differentiation between these two lesions.

Accuracy of Fine Needle Aspiration (FNA) in Diagnosis of Major Salivary Gland Tumors

Salivary glands tumors consist a major part of human tumors which their differentiation and treatment are very different. In addition to clinical experiments, biopsy is helpful method to obtain an accurate diagnosis. The biopsy of oral lesions is provided in different ways and one of them is Fine Needle Aspiration (FNA) which is a non-invasive, easy, quick and low cost experiment. The aim of this study was to define the accuracy of FNA in identifying major salivary glands tumors. The study was descriptive, retrospective. The medical records of Department of Pathology, Amir Alam Hospital were reviewed from 1994-2004. Data including age, gender, lesion site and FNA reports of all cases were registered. Histopathologic results of FNA samples and surgical gross reports were matched. Descriptive data was used for registered data analyzing. The SPSS 11.5 software was used for statistical analysis. From 656 specimen of FNA, there were 235 cases with both results of FNA and excisional biopsy. About 55 cases in gross experiment had not been shown tumor like lesion and 11 cases in FNA had not a definite diagnosis because of non sufficient of specimen; all these cases were rejected from study. Next study was for other 169 specimen. Considering negative for benign and positive for malignant, 37, 104, 10 and 18 cases were true positive, true negative, false positive and false negative, respectively. Sensitivity, specificity and accuracy were obtained about 67, 91 and 83%, respectively. Positive Predictive Value (PPV) and Negative Predictive Value (NPV) also were computed 78 and 85%, respectively. FNA is a safe, useful and quick method for identifying tumors of major salivary glands.

[Acute respiratory failure in obesity]

Obstructive sleep apnea, obesity-related hypoventilation - a hypoventilation which is independent of apneas and increased by sleep -, and hypoxemia related to local ventilation-perfusion disorders are the main mechanisms of respiratory failure occurring during acute respiratory decompensation following an often minimal triggering event. Non-invasive ventilation has been found to be an effective treatment, particularly with a ventilator capable of maintaining positive expiratory and pressure. The level of the expiratory positive airway pressure must be adapted to cure episodes of obstructive apnea or hypopnea. The level of the inspiratory positive airway pressure (pressure support ventilator), or the tidal volume (volume-controlled ventilator) must be adapted to correct the residual hypoventilation. These adaptations can be made by proper assessment of nocturnal SaO(2) recordings. In particularly severe cases, use of endotracheal ventilation may be necessary to control a state of shock or consciousness disorders incompatible with the patient cooperation necessary for non-invasive ventilation.

[Fat embolism with lung hemorrhage]

Post-traumatic fat embolism was disclosed by a picture of alveolar hemorrhage. Acute hypoxemia associated with dense bilateral pulmonary infiltrates was observed in a 21 year-old woman, 4 days after an accident with closed tibial fracture. Cruoric pulmonary thromboembolism was ruled out, as was an acute pulmonary edema. Neither infectious nor immunologic etiology was found. The diagnosis of alveolar hemorrhage was based on bronchoalveolar lavage. Lipid droplets in macrophages stained by "Oil Red O" established the relationship with fat embolism. The outcome was favorable. The association of fat embolism and alveolar hemorrhage has already been reported, but remains rare.

Central sleep apnoea in Arnold-Chiari malformation: evidence of pathophysiological heterogeneity

We report on the case of two young patients with type I Arnold-Chiari malformation (ACM), as revealed by a central sleep apnoea (CSA) syndrome without any other neurological defect. Case 1 was a 14-yr-old male patient, who developed severe alveolar hypoventilation and needed long-term mechanical ventilation via a tracheostomy. Case 2 was a 39-yr-old male patient, who developed features suggestive of sleep apnoea and responded to nasal continuous positive airway pressure ventilation despite the central type of apnoeas. These two cases illustrate the different pathophysiological mechanisms involved in CSA, namely a blunted chemical drive (in hypercapnic patients) and an increased chemical drive, which destabilizes the breathing pattern during sleep (in normo/hypocapnic patients). Central sleep apnoea can be the initial manifestation of Arnold-Chiari malformation and can lead to a life-threatening condition.

Relative survival analysis of 252 patients with COPD receiving long-term oxygen therapy

OBJECTIVES

A survival analysis was conducted on patients with COPD receiving long-term oxygen therapy (LTOT) to compare two different statistical methods.

METHODS

We used a multivariate crude (observed) survival model (Cox) and a multivariate relative survival model (Hakulinen). Only the latter is able to correct the survival by adjusting it to the normal life expectancy of the studied patients.

PATIENTS

Two hundred fifty-two hypoxemic COPD patients (207 male) requiring LTOT were included. Mean PaO2 was <50 mm Hg before oxygen therapy. Mean age was >69 years (SE: 9.9). They had severe bronchial obstruction: mean FEV1 was <33% (10.6) of predicted values, with some CO2 retention: mean PaCO2 was 45.6 (7.1) mm Hg. By December 31, 1995, 189 patients had died (75%) and 13 (5%) were unavailable for follow-up.

RESULTS

The overall crude survival was poor: 80.9% after 1 year, 67.1% after 2 years, 34.7% after 5 years, and 7.1% after 10 years. In the crude multivariate analysis (Cox), the negative prognostic factors were age and hypercapnia. The overall relative survival (Hakulinen), corrected for life expectancy, was 82.8% after 1 year, 70.8% after 2 years, 41.5% after 5 years, and 10.25% after 10 years. In the final multivariate relative model, age was no longer significant and the only bad prognostic factor was hypercapnia with a relative risk of 1.97 (1.16 to 3.34).

CONCLUSION

This work shows the inadequacy of the Cox observed survival model when it comes to appreciating the real prognostic impact of age, because of the confusing factor associated with a normal life expectancy.

[Management of obesity and respiratory insufficiency. The value of dual-level pressure nasal ventilation]

Obstructive Sleep Apnea (OSA), Obesity-Linked Hypoventilation (OLH)--a hypoventilation which is independent of apneas and increased by sleep--, and COPD are mechanisms for respiratory failure in obese patients. We thought nasal bi-level positive airway pressure to be a suitable treatment: EPAP is useful to maintain upper airway patency and IPAP-EPAP difference to correct OLH and COPD hypoventilation. Our purpose is to report the results of such a therapeutic approach. We included 41 patients that we first treated by nasal bi-level positive airway pressure for a respiratory failure with an uncompensated respiratory acidosis. The initial setting was about 4 cm H2O for EPAP and 16 for IPAP. Under supervision of a real-time printed oximetry tracing, we furthermore increased EPAP until disappearance of repetitive dips in oxygen saturation (that we assimilated to obstructive events) and IPAP until obtaining an acceptable level of steady saturation (we assimilated a low level to a steady hypoventilation). Age (mean +/- SD) was 63 +/- 11 years, BMI 42 +/- 9 kg/m2, pH 7.32 +/- 0.04, PaCO2 71 +/- 13 mmHg, PaO2 45 +/- 7 mmHg. Thirty-nine out of 41 patients returned home without need for tracheal intubation. At 7 days of treatment, PaCO2 was 50 +/- 6 mmHg. Thus, nasal bi-level position airway pressure appears to be an efficient treatment in these patients.

Fatal ball-valve airway obstruction by an extensive blood clot during mechanical ventilation

A ball-valve airway obstruction by a blood clot cast of almost the whole bronchial tree occurred in a small-cell lung cancer patient, who had been on mechanical ventilation for 9 days. Chest radiographs revealed overinflated lungs. Attempts to remove the cast via fibreoptic bronchoscopy were unsuccessful and the patient died. A postmortem extraction of the clot was performed with a rigid tube. This case is rare because of absence of severe haemoptysis and lung volume reduction.