Chemical kinetics of silver diammine fluoride in demineralization and remineralization solutions-an in vitro study

Introduction

Silver Diammine Fluoride (SDF) is a clinical minimal intervention to manage dentin caries. Its chemistry in demineralization conditions has been investigated widely, but far less in remineralization conditions. The aim was to investigate and compare the chemical reactions when SDF is added to remineralization and demineralization solutions.

Methods

0.01 ml SDF (Riva Star) was added to deionized water (DW); demineralization (DS = pH4) and remineralization (RS = pH7.0) solutions. The time sequence of concentrations of NH4+, F-, and Ag+ were measured using ion selective electrodes (ISEs) every 2 min. The pH was also measured. Precipitates were characterized using x-ray Diffraction (XRD) and, 31P and 19F nuclear magnetic resonance spectroscopy (NMR).

Results

The concentrations of NH4+ and Ag+ showed decreasing trends in DW (-0.12 and -0.08 mM/h respectively), and in DS (-1.06 and -0.5 mM/h respectively); with corresponding increase in F- concentration (0.04 and 0.7 mM/h respectively). However, in RS, NH4+ concentration showed little change (0.001 mM/h), and Ag+ and F- concentrations were negligible. XRD results showed that precipitates (in RS only) contained AgCl, and metallic Ag. NMR showed that fluorapatite/carbonated fluorapatite (FAP/CFAP) were formed. The pH increased after SDF addition in all three solutions.

Discussion

SDF dissolved to release NH4+, F- and Ag + . In DW and DS, NH4+ combined with Ag+ to form diamminesilver, causing an increase of F- and pH. In RS, F- reacted with Ca2+ and (PO)43- to form FAP/CFAP, and Ag+ reacted with Cl- to form AgCl/Ag. These suggests why SDF is effective in managing dentin caries.

Characterization of chemical reactions of silver diammine fluoride and hydroxyapatite under remineralization conditions

Introduction

Silver Diammine Fluoride (SDF) is a clinically used topical agent to arrest dental caries. However, the kinetics of its chemical interactions with hydroxyapatite (HA), the principal inorganic component of dental enamel, are not known. The aim was to characterize the step-wise chemical interactions between SDF and HA powder during the clinically important process of remineralization.

Methods

Two grams of HA powder were immersed in 10 ml acetic acid pH = 4.0 for 2 h to mimic carious demineralization. The powder was then washed and dried for 24 h and mixed with 1.5 ml SDF (Riva Star) for 1 min. The treated powder was then air-dried for 3 min, and 0.2 g was removed and stored in individual tubes each containing 10 ml remineralizing solution. Powder was taken from each tube at various times of exposure to remineralization solution (0 min, 10 min, 2 h, 4 h, 8 h, 24 h, and 10 days), and characterized using Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) spectroscopy.

Results and discussion

19F MAS-NMR spectra showed that calcium fluoride (CaF2) started to form almost immediately after HA was in contact with SDF. After 24 h, the peak shifted to -104.5 ppm suggesting that fluoride substituted hydroxyapatite (FSHA) was formed with time at the expense of CaF2. The 31P MAS-NMR spectra showed a single peak at 2.7 ppm at all time points showing that the only phosphate species present was crystalline apatite. The 35Cl MAS-NMR spectra showed formation of silver chloride (AgCl) at 24 h. It was observed that after the scan, the whitish HA powder changed to black color. In conclusion, this time sequence study showed that under remineralization conditions, SDF initially reacted with HA to form CaF2 which is then transformed to FSHA over time. In the presence of chloride, AgCl is formed which is subsequently photo-reduced to black metallic silver.

401 Squamous Cell Carcinoma Surgery During a Global Pandemic – a Single UK Tertiary Centre Experience

Aim

Method

Results

Conclusions

632 Analysing Laser Doppler Images - A Modified Approach to the Assessment of Burn Depth

Aim

To establish a method of quantifiably determining burn depth from Laser Doppler (LD) images of burns.

Method

NICE advises for LD scanning to be utilised for the assessment of intermediate depth burns, where there is doubt about burn depth following experienced clinician examination. However, these scan images do not provide a quantifiable measure of burn depth. LD determines burn perfusion, with deeper burns appear blue, and superficial burns appearing red. We retrospectively studied LD images from 110 patients over the course of 2019. Using Adobe Photoshop, Histogram software, we highlighted the burns using the selection tool, and determined the proportion of the burn that was deep/poorly perfused. We then correlated these results with time till recovery.

Results

Burns with a poorly perfused region of larger than 20%, had a proportional increase in time till full recovery. This proportional increase was also reflected in burns with a 30% and 40% poor perfusion. Burns with less than 20% of poor perfusion were found to recover at the same rate as superficial burns. This novel method for the measurement of burn depth will allow for the examining plastic surgeon to make a decision on treatment based on concrete and quantifiable burn depth data.

Conclusions

We have demonstrated the initial validity of a novel method for the quantifiable measurement of burn depth. Further study is required, to establish the validity of this novel approach to the quantifiable detection of burn depth.

636 Optimising Operative Capacity for Hand Trauma - An audit

Aim

Assess compliance with departmental and BSSH guidelines for hand trauma. Optimise operative capacity within the department. Promote minor ops experience among the junior doctors.

Method

Retrospective review of the overbooked patients seen in the Hand trauma Unit (HTU) in August 2020 using the eTrauma system and time to operation using the Lorenzo patient record system.

Results

Overall Local Compliance rates

Overall BSSH Compliance rates

Main area of non-compliance was waiting time for tendon operations, with a 30% breech rate (>5 days waiting time).

Conclusions

Interventions before re-audit: On call junior doctor to be based in HTU for the whole day- will allow for minor procedures (nail beds and skin lacerations) to be done at bedside. The above will free up capacity in the minor ops theatre for tendons.

Histopathological alterations in gills, liver, kidney and muscles of Ictalurus punctatus collected from pollutes areas of River

Abstract Untreated sewage and industrial wastes from Faisalabad city are disposed to River Chenab through Chakbandi Main Drain (CMD). The present project is planned to investigate the effects of this freshwater pollution on the body of fish Ictalurus punctatus. The specimens of this fish species were collected upstream and downstream of the entrance of CMD into River Chenab. Fish gills, liver, kidney and muscles from dorsolateral regions of fish were subjected to histopathology. Farmed fish and fish from upstream areas were used as control. Fish collected from polluted experimental sites showed significant damage in selected organs. Gill tissues showed an abnormality in the form of an uplifting of the primary epithelium, fusion, vacuolation, hypertrophy, and necrosis. While liver tissues subjected to hepatocytes degeneration, necrosis, mitochondrial granular hepatocyte, and sinusoids dilation. Kidney tissues indicated increased bowmen space and constricted glomerulus and degenerated nephrons. Edema, necrosis, and atrophy were observed in muscle tissues of fish from polluted areas. Fish from the upstream area showed fused gill lamellae, inflammatory cell infiltration, hypertrophy and vacuolation in hepatocytes. Kidney tissues indicated the presence of nuclear tubular cells, destructive renal tubules, hemorrhage, and necrosis at tubular epithelium. Intra myofibril spaces were also observed in muscles. Specimens of control fish indicated no variation in gills, liver, kidney, and muscles. The present study revealed a strong correlation between the degree of tissue damage and environmental contamination. Present findings also compel global warnings to protect our water bodies and fish to rescue the human population.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Superior septal approach versus left atrial approach for mitral valve replacement: A retrospective cohort study

OBJECTIVE

To compare the outcomes of superior septal approach and left atrial approach for mitral valve replacement.

METHODS

This retrospective cohort study was conducted at the Aga Khan University Hospital, Karachi, and comprised records of patients who had undergone isolated mitral valve replacement from May 2003 to April 2012. Cases were reviewed for the outcomes [primary: loss of normal sinus rhythm; secondary: complications, residual defect and mortality]. Patients with prior history of dysrhythmia, low ejection fraction (<30%), emergency/redo mitral valve replacement and concomitant coronary artery bypass grafting were excluded. SPSS 19 was used for data analysis.

RESULTS

Of the 78 patients, 52(66.67%) were of superior septal approach and 26(33.33%) of left atrial approach. Both groups were comparable for baseline variables except cardiopulmonary bypass and cross-clamp times, which were significantly shorter in the superior septal approach group than the left septal approach group (p<0.05). No residual atrial septal defect was found in any approach. Although loss of normal sinus rhythm was observed more frequent in superior septal approach 25(48%) compared to left septal approach 10(38.4%), but the difference was statistically insignificant (p=0.28). Age was the only significant variable affecting loss of normal sinus rhythm after adjusting for approaches. The difference of post-operative complications was also statistically insignificant between superior 9(17.3%) and left septal approach 4(15.38%) (p=1.0)].

CONCLUSIONS

The operative durations were significantly higher in left atrial approach compared to superior septal approach.

Modeling of wastewater quality in an urban area during festival and rainy days

Water pollution during festival periods is a major problem in all festival cities across the world. Reliable prediction of water pollution is essential in festival cities for sewer and wastewater management in order to ensure public health and a clean environment. This article aims to model the biological oxygen demand (BOD(5)), and total suspended solids (TSS) parameters in wastewater in the sewer networks of Karbala city center during festival and rainy days using structural equation modeling and multiple linear regression analysis methods. For this purpose, 34 years (1980-2014) of rainfall, temperature and sewer flow data during festival periods in the study area were collected, processed, and employed. The results show that the TSS concentration increases by 26-46 mg/l while BOD(5) concentration rises by 9-19 mg/l for an increase of rainfall by 1 mm during festival periods. It was also found that BOD(5) concentration rises by 4-17 mg/l for each increase of 10,000 population.

Glass ionomer cements: effect of strontium substitution on esthetics, radiopacity and fluoride release

OBJECTIVE

SrO and SrF2 are widely used to replace CaO and CaF2 in ionomer glasses to produce radiopaque glass ionomer cements (GIC). The purpose of this study was to evaluate the effects of this substitution on release of ions from GIC as well as its effect on esthetics (translucency) and radiopacity.

MATERIALS AND METHODS

Cements were produced from ionomer glasses with varying content of Sr, Ca and F. The cements were stored in dilute acetic acid (pH 4.0) for up to 7 days at 37°C. Thereafter, the cements were removed and the solution was tested for F(-), Sr(2+), Ca(2+), and Al(3+) release. Radiopacity and translucency were measured according to BS EN ISO 9917-1:2003.

RESULTS

Ion release was linear to t(1/2) suggesting that this is a diffusion controlled mechanism rather than dissolution. The fluoride release from the cements is enhanced where some or all calcium is replaced by strontium. Radiopacity shows a strong linear correlation with Sr content. All cements were more opaque than the C0.70 0.55 standard but less opaque than the C0.70 0.90 standard which is the limit for the ISO requirement for acceptance.

SIGNIFICANCE

This study shows that the replacement of calcium by strontium in a glass ionomer glass produces the expected increase in radiopacity of the cement without adverse effects on visual properties of the cement. The fluoride release from the cements is enhanced where some or all calcium is replaced by strontium.

Biochemical Parameters in Women with Polycystic Ovary Syndrome in Ajman, UAE

Aims: Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting 5 -10% of women and is a major cause of anovulatory infertility. Prevalence varies among population based on genetic and environmental factors. Etiology of PCOS remains unknown but hyperandrogenism and insulin resistance have both been associated with PCOS. The aim of this study was to measure levels of Homocysteine and other biochemical parameters in women diagnosed with PCOS attending Gulf Medical College Hospital & Research Centre (GMCHRC), Ajman, UAE. Methods: Young women, aged between 18 and 35 years of age, diagnosed with PCOS (N =37), not on any treatment, attending GMCHRC were included in the study. Biochemical parameters were measured using standard procedures. Laboratory normal reference ranges were used for comparison. Results: 54 % of the women with PCOS were overweight or obese according to the Body mass index (BMI) and 51% had a waist circumference >88cm. Fasting and postprandial Glucose and Insulin levels and HOMA-IR were within the normal reference range indicating that no Insulin resistance was seen in these women. 40% of the women had a serum total Cholesterol level above 200 mg/dL, while Low Density Lipoprotein (LDL) Cholesterol was above and High Density Lipoprotein (HDL) cholesterol was lower than the desirable value. Serum Triacylglycerol was within the normal reference range. Serum Testosterone, Estradiol, Prolactin Thyroid Stimulating Hormone (TSH) and Plasma Homocysteine level were found to be within the normal reference ranges. Homocysteine levels correlated with Testosterone, total Cholesterol and LDL cholesterol levels. Conclusions: BMI was high in 54% of the women. No Insulin resistance was seen in these patients. Hormone levels and Homocysteine were within normal reference ranges. Dyslipidermia was observed. These findings differ from reports in literature where Insulin resistance, Hyperandrogenism and high Homocysteine levels have been associated with PCOS. NJOG 2011 Nov-Dec; 6 (2): 7-10 DOI: http://dx.doi.org/10.3126/njog.v6i2.6748  

The effect of ultrasound on the uptake of fluoride by glass ionomer cements

Ultrasound has been shown to improve the set of glass ionomer cements (GICs) and also other cement properties. In particular, the release of fluoride is enhanced. These cements also can take up fluoride ion from liquids. The aim of this study is to investigate the effect of ultrasound on this cement property. Two commercial dental restorative GICs were used together with a modified commercial material and an experimental material based on a F-free glass. All three commercial materials came in capsules which were mixed as makers directed, the experimental material was mixed as in previous papers. Mixed cement was placed polyethylene moulds to create 3 × 2 mm thick discs. These were either allowed to standard set for 6 min or set with ultrasound for 55 s. 18 samples were made for each material/set. Three samples were placed in 4 ml of 0.2% NaF solution for 24 h at 37°C. The cylinders were removed and the F concentration of the solutions measured by ISE using TISAB decomplexant. F uptake was determined by difference from the original NaF concentration. The two conventional GICs showed reductions of 17.4 and 8.5% for ultrasound compared to standard set whereas the modified material increased by 32.3% and the experimental one by 20.6%. It is suggested that the effect of ultrasound may increase the surface area of the residual glass particles in the GIC which would increase F uptake. In GICs where considerable F ion is released into the cement matrix by the enhanced reaction caused by ultrasound this may be sufficient to reverse the former effect producing the reduced uptake observed.

The effect of ultrasound on the setting reaction of zinc polycarboxylate cements

The set of glass ionomer cement (GIC) is accelerated by application of ultrasound. Although GIC has somewhat displaced zinc polycarboxylate cement (ZPC) in dental applications the latter is still extensively used. Like GIC, it provides direct adhesion to tooth and can provide F release, but is more radiopaque and biocompatible than GIC. The aim of this study is to examine the effect of ultrasound on the setting of ZPC using Fourier transform infra red spectroscopy and any interaction with SnF(2) addition. ZPC with and without SnF(2) addition (+/-S) at luting (L) 2:1 P/L ratio and restorative (R) 4:1 P/L ratio consistencies. Ultrasound is applied to the cement using Piezon-Master 400, EMS, Switzerland at 60 s from start of mixing for 15 s. The ratios of absorbance peak height at 1,400 cm(-1) -COO(-) to that at 1,630 cm(-1) -COOH were measured and compared those obtained for the cement not treated with US. These values were taken at the elapsed time at which no further change in spectrum [ratio] was observed at room temperature [10-20 min]. The US results are taken at 2 or 3 min. No US: R/+S (1.09), R/-S (1.2), L/+S (1.07), L/-S (1.04); US: R/+S (1.50), R/-S (1.64), L/+S (1.38), L/-S (1.05). The results show all four ZPC formulations are very sensitive to ultrasound whether with or without SnF(2). Reducing US to 10 s produces lower initial ratios but these increase up to 10 min when very high ratios (>2) are obtained. Previous studies with restorative GICs found that 40-55 s US was needed to produce the effect found with 15 s on ZPCs. ZPC powder is more basic than GIC glass; this may account for ZPC's greater sensitivity to US. Ultrasound may provide a useful adjunct to the clinical use of ZPC both as luting agent and temporary restorative.

Kinetics of fluoride ion release from dental restorative glass ionomer cements: the influence of ultrasound, radiant heat and glass composition

To compare the effect of ultrasonic setting with self curing on fluoride release from conventional and experimental dental glass ionomer cements. To compare hand mixed and capsule mixing and the effect of replacing some of the reactive glass with zirconia. In a novel material which advocated using radiant heat to cure it, to compare the effect of this with ultrasound. To evaluate the effect of ultrasound on a glass ionomer with fluoride in the water but not in the glass. 10 samples of each cement were ultrasonically set for 55 s; 10 controls self cured for 6 min. Each was placed in 10 ml of deionised water which was changed at 1, 3, 7, 14, 21, 28 days. The solution fluoride content was measured using a selective ion electrode. All ultrasound samples released more fluoride than the controls. Release patterns were similar; after a few days, cumulative fluoride was linear with respect to t(1/2). Slope and intercept of linear regression plots increased with ultrasound. With radiant heat the cement released less fluoride than controls. The effect of ultrasound on cement with F in water increased only slope not intercept. Zirconia addition enhances fluoride release although the cement fluorine content is reduced. Comparison of capsule and hand mixing showed no consistent effect on fluoride release. Ultrasound enhances fluoride release from GICs. As heat has an opposite effect the heat from ultrasound is not its only action. The lesser effect on cement with fluoride only in the water indicates that of ultrasound enhances fluoride release from glass.

Capecitabine therapy in advanced gall bladder cancer: A phase II study

14153

Background: Thymidine phosphorylase (TP) activity is found at higher levels in gall bladder cancer (GBC) tissues than in adjacent healthy tissues. GBC is relatively sensitive to 5-FU. TP activated capecitabine (CAP) mimics the continuous infusion of 5-FU. In view of drug potentiality this present study was initiated. Our aim was to evaluate the therapeutic efficacy and safety of CAP in previously untreated GBC patients (Pts). Methods: It was an open-labelled, single-centred, non-randomised and prospective study. Outcome measures were response rate and type of response for efficacy measurement and safety was measured by adverse events & laboratory blood values (LBV). All LBV were within reference range at baseline. The patients had no prior chemo/ radio therapy or a family history of malignancy; adenocarcinoma (stage III–IV); age 40–70 yrs; male/female: 16/ 30; KPS ≥ 70%. 46 pts were treated with 306 cycles (min 3–max 12) of CAP at a dose of 2500 mg/day in two divided doses from day 1–14 followed by 1-week rest. Results: Median age was 50 yrs. Hand foot syndrome occurred in 17.39% pts, diarrhoea (grade 3 & 4) 21.75% and both 15.21%, all toxicities were manageable. Mean LBV before and after CAP therapy were hemoglobin: 11.38–0.35 g/dl (95% CI, 10.66–2.10); total count of WBC: 9,260–580/mm3 (95% CI, 8,680–9,840); platelet count: 251,000–2,000/mm3 (95% CI, 227,000–275,000) and serum bilirubin: 1.17–0.33 mg/dl (95% CI, 0.5–1.84). The LBV between baseline and after CAP therapy were not statistically significant. Partial response was found in 12 pts (26.08%), stable disease in 26 pts (56.21%), and progressive disease in 8 pts (17.39%). Mean KPS value after therapy was 76% (95% CI, 69–84). Conclusion: This clinical experience indicates that CAP is a convenient choice in phase II chemo naïve GBC pts not adversely affecting haematological values.

No significant financial relationships to disclose.

CD4+ Th1 and CD8+ type 1 cytotoxic T cells both play a crucial role in the full development of contact hypersensitivity

The role of CD4(+) vs CD8(+) T cells in contact hypersensitivity (CHS) remains controversial. In this study, we used gene knockout (KO) mice deficient in CD4(+) or CD8(+) T cells to directly address this issue. Mice lacking either CD4(+) or CD8(+) T cells demonstrated depressed CHS responses to dinitrofluorobenzene and oxazolone compared with wild-type C57BL/6 mice. The depression of CHS was more significant in CD8 KO mice than in CD4 KO mice. Furthermore, in vivo depletion of either CD8(+) T cells from CD4 KO mice or CD4(+) T cells from CD8 KO mice virtually abolished CHS responses. Lymph node cells (LNCs) from hapten-sensitized CD4 and CD8 KO mice showed a decreased capacity for transferring CHS. In vitro depletion of either CD4(+) T cells from CD8 KO LNCs or CD8(+) T cells from CD4 KO LNCs resulted in a complete loss of CHS transfer. LNCs from CD4 and CD8 KO mice produced significant amounts of IFN-gamma, indicating that both CD4(+) and CD8(+) T cells are able to secrete IFN-gamma. LNCs from CD8, but not CD4, KO mice were able to produce IL-4 and IL-10, suggesting that IL-4 and IL-10 are mainly derived from CD4(+) T cells. Intracellular cytokine staining of LNCs confirmed that IFN-gamma-positive cells consisted of CD4(+) (Th1) and CD8(+) (type 1 cytotoxic T) T cells, whereas IL-10-positive cells were exclusively CD4(+) (Th2) T cells. Collectively, these results suggest that both CD4(+) Th1 and CD8(+) type 1 cytotoxic T cells are crucial effector cells in CHS responses to dinitrofluorobenzene and oxazolone in C57BL/6 mice.

Effects of acute and subchronic administration of typical and atypical antipsychotic drugs on the neurotensin system of the rat brain

The acute and subchronic effects of a variety of doses of a prototype typical (haloperidol) or one of several atypical antipsychotic drugs (clozapine, olanzapine, risperidone, quetiapine, or sertindole) on regional brain neurotensin (NT) tissue concentrations, and NT receptor binding were examined. Acute administration of haloperidol, clozapine, olanzapine, and risperidone dose-dependently increased NT tissue concentrations in the nucleus accumbens. Haloperidol, olanzapine, risperidone, and sertindole also increased NT tissue concentrations in the caudate nucleus. NT tissue concentrations in the nucleus accumbens and caudate remained elevated after 14-day administration of haloperidol, olanzapine, sertindole, and risperidone. In contrast, at the doses studied, quetiapine decreased NT tissue concentrations in the nucleus accumbens; clozapine had no effect. Haloperidol significantly increased NT receptor binding in the substantia nigra after 14-day administration. All of the atypical antipsychotic drugs decreased NT receptor binding in the nucleus accumbens and in the substantia nigra. Although these studies do not conclusively support the hypothesis that increased NT neurotransmission is involved in the clinically relevant effects of all antipsychotic drugs, the extant evidence clearly suggests that further study is warranted. Inconsistencies in the data suggest that differential effects of antipsychotic drug administration on subpopulations of NT neurons must be scrutinized further.

Tetanus antibody levels among adolescent girls in developing countries

Neonatal and maternal tetanus infections remain an important cause of death in many countries. Few studies have reported tetanus toxoid antibody levels of adolescent girls. As part of the Expanded Programme on Immunization most girls receive up to 3 injections in early childhood, and many subsequently do not receive booster vaccinations until pregnant. We determined (by ELISA) tetanus antibody seropositivity in adolescent girls from Malawi (in 1996), Nigeria (in 1993) and Pakistan (in 1996), and response to tetanus vaccination in adolescent girls from Pakistan. Geometric mean titres (GMT, IU/mL) were 0.94 in 117 Malawian, 0.32 in 154 Nigerian and 1.08 in 162 Pakistani girls. In Nigeria, 54.7% of adolescents were seronegative, of whom 26.8% had a history of unsafe abortion. In Malawi and Pakistan all girls were seropositive and in Pakistan, following a booster vaccination, titres increased 3-fold, with a lower response in older girls. The results indicated that adequate childhood immunization is likely to provide protective levels through adolescence. Booster vaccination in late childhood/early adolescence should protect the majority of women throughout their reproductive lives. This practice would reduce the risks of girls exposed to infection through unsafe abortions, and may be the best option for countries seeking to improve their vaccination schedule, especially where tetanus vaccine coverage in pregnant women is unacceptably low.