The complete nucleotide sequence of chromosome 3 of Plasmodium falciparum

Analysis of Plasmodium falciparum chromosome 3, and comparison with chromosome 2, highlights novel features of chromosome organization and gene structure. The sub-telomeric regions of chromosome 3 show a conserved order of features, including repetitive DNA sequences, members of multigene families involved in pathogenesis and antigenic variation, a number of conserved pseudogenes, and several genes of unknown function. A putative centromere has been identified that has a core region of about 2 kilobases with an extremely high (adenine + thymidine) composition and arrays of tandem repeats. We have predicted 215 protein-coding genes and two transfer RNA genes in the 1,060,106-base-pair chromosome sequence. The predicted protein-coding genes can be divided into three main classes: 52.6% are not spliced, 45.1% have a large exon with short additional 5' or 3' exons, and 2.3% have a multiple exon structure more typical of higher eukaryotes.

Fluoride ingestion from toothpaste by young children

OBJECTIVE

To investigate the reported and observed brushing habits of young children and their ingestion of fluoride from toothpaste.

DESIGN

In 1997, a random sample of 50 children, aged 30 months, from three districts in the North West region of England, were visited at home.

METHODS

The reported and observed toothbrushing behaviour was determined and the weight of toothpaste applied to the toothbrush was measured. The amount of fluoride retained in the mouth after brushing with either a 400 ppm F or 1,450 ppm F toothpaste was determined.

RESULTS

All parents claimed that their children's teeth were being brushed with a fluoride toothpaste at least once daily. The mean amount of toothpaste applied on the brush was 0.36 g of which 0.27 g (72%) was retained in the mouth. The mean amount of fluoride ingested per brushing was 0.42 mg when using the 1,450 ppm F toothpaste and 0.10 mg when using the 400 ppm F toothpaste. Although most parents applied a small amount of toothpaste a small minority applied a large amount. If using the 400 ppm F toothpaste twice daily no children of average weight would have exceeded ingestion of 0.05 mgF/kg body weight whereas 14 average weight children would have exceeded this value if using the 1450 ppm F toothpaste.

CONCLUSIONS

It is essential that parents of children aged less than 7 years apply a small (pea-sized) amount of fluoride toothpaste on the toothbrush and discourage swallowing.

An in-vitro evaluation of a dental subtraction radiography system using bone chips on dried human mandibles

The aim of this in vitro study was to evaluate the ability of digital subtraction radiography to detect small differences in bone density between 2 dental images captured with the Digora radiographic imaging system. 5 dried human mandibles were held in a fixed position and cortical bone chips were superimposed on the alveolar bone between the 1st molar and 2nd premolar teeth. For each mandible, a reference image was obtained without bone chip placement. Subsequently, another image without a bone chip and a series of 10 images with bone chips ranging from 1.2 to 35.3 mg, were recorded. Each of the initial images of the 5 mandibles was then compared to the 11 subsequent images using digital subtraction radiography. The difference in density between the 2 images, at the site between the 1st molar and 2nd premolar, was calculated and represented as a volume equivalent of aluminium. Regression analysis demonstrated a close relationship between the weight of the bone chips and the aluminium equivalent density difference between the 2 radiographs (r2 = 0.96). Good results were obtained with the smaller bone chips that more closely resembled the dimensions of bone changes likely to be of clinical interest (1-8 mg). It is concluded that this subtraction radiography system is suitable for clinical investigations of localised small changes in alveolar bone and for the diagnosis and monitoring of destructive forms of periodontal diseases.

Fluoride: how to maximize the benefits and minimize the risks

This article reviews current thinking on the rational use of fluoride for the safe and effective prevention of dental caries, so that benefits may be maximized and risks minimized.

Evidence for phosphoprotein microspheres in bone

Bone sialoprotein and osteopontin are 'bone-specific' phosphoproteins, but their function is uncertain and their ultrastructural associations remain unclear. Insight into their role was sought by special attention to their general distribution and specific morphology under the high-power optical microscope. Their extracellular staining characteristics were examined in cryosections of adult rat skeletal tissues using two immunohistochemical methods. The two proteins were clearly evident in immature woven bone of endochondral and intramembranous origin (although cartilage was negative, even when calcified). In mature lamellar bone, bone sialoprotein remained ubiquitous, while osteopontin was confined to cement lines and other relatively discrete sites of past and present resorption activity, particularly near blood vessels. In neither case was the distribution of the stain structureless and diffuse. Invariably (except when non-specific), it was sharply defined and had the form of microspheres measuring approximately 1 microm in diameter. In both immature and mature regions, these objects appeared in sheets, chains or groups in a pattern that was evidently coincident with a similar structural arrangement found within the inorganic phase of bone. It was concluded that phosphoproteins are not randomly located throughout the collagenous matrix but are apparently integral to calcified microsphere populations, and it is suggested that these structures are well placed to control the chemical state of the mineral over their surfaces and influence remodelling.

Effect of a triclosan/copolymer dentifrice on the incidence of periodontal attachment loss in adolescents

The aim of this study was to assess the effectiveness of a dentifrice containing 0.3% triclosan, 2.0% copolymer and 0.243% sodium fluoride (Colgate Total) in the prevention of periodontal attachment loss in adolescents. A 3-year, double-blind, randomised, controlled, clinical trial was conducted on 641 adolescents, initially aged 11-13 years. The participants were enrolled from schools in economically deprived areas of Manchester, England, which had a high % of Asian pupils originating from India, Pakistan and Bangladesh. After the baseline examination, which included assessments of pocket depth, attachment loss and subgingival calculus, the adolescents were randomly allocated to use either a triclosan/copolymer or control dentifrice. The control was identical to the test dentifrice with the exception that it did not contain triclosan/copolymer. Participants were re-examined after 18 and 36 months. After 3 years, a total of 239 adolescents remained in the test and 241 in the control group. The prevalence of attachment loss increased from 2% at baseline to 24% after 3 years. The mean increment of attachment loss during the study was 0.025 mm per site in the control group and 0.018 mm per site in the test group. A linear regression model showed a statistically significant difference in attachment loss between the test and control group, in adolescents with high mean pocket depths at baseline. No adverse effects attributable to the test or control dentifrices were observed during the study. This study has demonstrated that unsupervised use of a triclosan/copolymer dentifrice can significantly reduce periodontal attachment loss, particularly in adolescents with high mean pocket depths.

Occlusal caries diagnosis: an in vitro histological validation of the Electronic Caries Monitor (ECM) and other methods

OBJECTIVES

The aim of this in vitro study was to validate the use of the Electronic Caries Monitor (ECM) for the detection of enamel and dentinal caries on the occlusal surfaces of posterior teeth, and to compare it with visual examination, fibre-optic transillumination, conventional and digital bitewing radiography.

METHODS

One-hundred and three extracted posterior permanent teeth with no apparent occlusal cavitation were selected and examined using each system. Thirty teeth were re-examined with each system to assess repeatability. Each tooth was then serially sectioned and examined histologically for occlusal caries.

RESULTS

The occlusal surfaces of 25 teeth had caries in enamel and 37 had dentinal carious lesions. The sensitivity and specificity of the ECM were 0.78 and 0.80 for the diagnosis of occlusal dentinal lesions (cut-off = 0.391) and 0.65 and 0.73 for enamel lesions (cut-off = 0.501). The weighted kappa value for repeatability of the ECM was 0.68. Of the other diagnostic systems, visual examination provided the best combination of sensitivity and specificity, 0.24 and 0.97 for dentinal caries and 0.60 and 0.73 for enamel caries, respectively.

CONCLUSION

The ECM was the most accurate diagnostic tool for the in vitro diagnosis of early, non-cavitated occlusal lesions on posterior teeth.

Factors influencing the amount of fluoride toothpaste applied by the mothers of young children

OBJECTIVE

To determine the weight of dentifrice and consequent amount of fluoride placed on a toothbrush by the mothers of young children when instructed to apply a pea-sized quantity or smear of two dentifrices containing different fluoride concentrations from tubes with round or star-shaped nozzles.

SUBJECTS AND METHODS

53 mothers participated in the study and each applied the eight possible combinations of dentifrice in a random order.

RESULTS

The mean weight of dentifrice, and therefore fluoride, applied was statistically less for the smear instruction than the pea but the difference was small. Significantly less weight of Colgate 0-6 gel was applied when compared with Colgate Great Regular Flavour (GRF) but the nozzle shape had no significant effect on the weight of dentifrice applied.

CONCLUSIONS

The difference in fluoride concentration between GRF (1450 ppm F) and Colgate 0-6 gel (400 ppm F) was the most important determinant of the amount of fluoride applied.

The reasons for tooth extractions in adults and their validation

OBJECTIVES

To investigate the primary reasons for the extraction of permanent teeth in adults and to validate the dentists' reasons for extraction.

METHODS

Twenty-one dentists in the Greater Manchester area took part in the study. These dentists provided extracted teeth stored in 10% buffered formal saline together with details of the patient's age, sex, dental attendance pattern and the reason for extraction. In order to validate the reasons for extraction, teeth were examined for the presence or absence of coronal and root caries. A subgroup of 80 teeth, half of which were extracted primarily for caries and half for periodontal reasons were selected, stained and attachment loss measured at six sites per tooth to validate periodontal reasons for extraction.

RESULTS

Three hundred and eighty-nine teeth were collected of which 37% were extracted primarily due to caries and 29% due to periodontal disease. Caries was the main reason for extraction in patients under 50 years, whereas periodontal disease was the commonest reason in the over-50 age group. Irregular attenders had more extractions for caries than regular attenders but attendance pattern did not affect the proportion of teeth extracted for periodontal reasons. The mean greatest loss of attachment on teeth extracted for periodontal reasons was 12 mm compared with 6.5 mm for caries.

CONCLUSION

In this group of patients caries was the most common reason for extraction of teeth but periodontal disease became a more important reason for extraction after 50 years of age. The study validated the dentists' given reason for extraction.

Dental health status associated with documented dental attendance patterns in adolescents

OBJECTIVE

To investigate the dental health of adolescents who exhibited four different patterns of documented dental attendance in regard to caries experience and types of treatment they received.

DESIGN

The adolescents were categorised according to whether they had been asymptomatic or symptomatic attenders in childhood and whether this had changed in early adolescence. Asymptomatic attenders were those who attended for examinations at least twice in any three year period. Symptomatic attenders were those who attended for examinations less frequently than this.

SUBJECTS

Treatment notes of 254, 13-15-year-old subjects who reported they were patients at one of 12 general dental practices or two community clinics were used to document attendance during the previous six years.

RESULTS

Those who attended asymptomatically throughout the study period of six years had fewer teeth extracted and more sealed teeth than those who attended symptomatically.

CONCLUSIONS

Among adolescents dental attendance in the absence of symptoms is associated with fewer missing teeth and wider provision of fissure sealants.

Evaluation of a dental subtraction radiography system

The aim of this in vitro study was to evaluate the ability of a dental subtraction radiography system to quantitatively detect differences in density between radiographic image pairs. Four periapical radiographs were taken of the upper first permanent molars on five human skulls using the Digora radiographic imaging system. The 4 images were a "baseline" image and 3 containing test objects consisting of either 0.5, 1 or 2 mm thick aluminium cylinders, 2.5 mm in diameter. Semi-automated image processing software was used to "warp" the 3 images with test objects into the same geometric/density registration as the corresponding baseline image using a process called patch minimization. "Difference" images were than produced and their contrast stretched. For regions of interest, with and without test objects present, the difference in density between the baseline and "test object" images was calculated using a reference aluminium step wedge. The test objects were clearly visible in all the "difference" images. The mean difference between the actual and estimated volume of the test object was 0.31 (95% CI [-0.55, 1.17]) mm3 Al. There was a strong association (r = 0.83) between the actual and estimated aluminium volumes. It is concluded that this system provides adequate precision for clinical evaluation.

Dental caries, fluorosis and the cosmetic implications of different TF scores in 14-year-old adolescents

The aims of this study were to determine the opinions of a group of adolescents about the cosmetic acceptability of a range of fluorosis, investigate the prevalence and severity of fluorosis in the sample and consider the extent to which fluorosis levels were related to their dental caries experience. A random sample of 534 14-year-old pupils from the non-fluoridated industrial city of Manchester were examined for caries and fluorosis. Each subject then examined six photographs of upper anterior teeth showing a range of TF scores 0-4 and were asked to rate the appearance of each as either very poor, poor, acceptable, good or very good and to indicate whether they would request treatment if their teeth were so affected. Four hundred and seventy-six subjects (89 per cent) had TF scores of 0. Of the 58 subjects (11 per cent) with fluorosis, 27 (5 per cent) scored TF = 1; 22 (4 per cent) TF = 2; 7 (1 per cent) TF = 3 and one subject scored TF = 4. The subjects who had no fluorosis had a mean DMFT of 3.0 which was significantly higher than the mean of 2.2 among those with any fluorosis. The proportion of subjects who rated the photographs as poor or very poor fell from 29 per cent for TF score 0 to 15 per cent for TF score 2 and then increased to 92 per cent for TF score 3. The responses of the subjects regarding their desire for treatment matched closely with their opinions on appearance; the majority of subjects expressed concern over the appearance of teeth with TF scores of 3 and higher. It is concluded that the prevalence of aesthetically objectionable dental fluorosis was low and that mild fluorosis was associated with a lower risk of dental caries and a more acceptable appearance. It is essential that a balanced view of the relative benefits and risks of the use of fluorides is maintained and proven benefits are not overwhelmed by largely unfounded aesthetic concerns.

The relationship between restorative treatment provided and a one year increment of the F component in the DMF index

There is considerable debate over the estimate of true increment of caries in an adult population derived from a conventional epidemiological study. The purpose of this investigation was to compare the increment of restorative treatment provided by dentists for caries with an estimate of what would have been recorded in a conventional epidemiological study as FT(S). The two types of increment were calculated from data collected for 3,920 regularly attending adults over the age of 25 years receiving dental treatment from 24 general dental practitioners. The adults were treated by their dentists prior to baseline so that, in the dentists' opinions, there were no caries lesions requiring restoration. All treatment carried out over the next 12 months together with the reasons for this, were recorded by the dentists. The increments for all restorative treatments and those considered by the dentist to be related to caries were calculated and compared with the conventional epidemiological FT and FS increments, calculated as changes from sound at baseline to restored for both teeth and surfaces. The results showed that the epidemiological FT and FS increments under-estimated both the total restorative treatment and that provided for caries by the dentists.

Caries prevention. A continued need worldwide

This paper provides a global perspective of the changing prevalence, severity, distribution and pattern of dental caries. The prevalence of caries in children and adolescents has declined in most developed countries and it is now a minority of young people who experience most of the disease. All forms of caries have reduced in prevalence but pits and fissures are the surfaces most frequently involved. The caries experience and levels of edentulousness in the adult populations of developed countries have also declined. The prevalence of caries in adults is remarkably constant with age but in older subjects root caries is becoming more prevalent. However, in many developing countries the prevalence of caries in young children is high and is increasing in those populations who are adopting a cariogenic diet. In countries such as Kenya and China, caries is the major cause of tooth loss but levels of edentulousness are low. There are considerable variations in disease levels between and within countries and it is evident that lower socio-economic and certain racial groups exhibit high levels of dental caries. It is essential to sustain the benefit of fluoride to those already receiving it and encourage the use of appropriate and effective strategies and products by those who are not. Water and salt fluoridation should be implemented where deemed feasible and the use of a clinically proven and affordable fluoride toothpaste should be encouraged.

The imaging performance of a storage phosphor system for dental radiography

Direct digital imaging systems are becoming increasingly common in dental radiography. The majority of these systems are based on charge coupled device (CCD) technology. A relatively new system, based on photo-stimulable phosphor luminescence (PSPL), is now commercially available. This system appears to overcome some of the restrictions of CCD systems including those associated with the bulky detector, connecting wire, limited image size and limited exposure latitude. A physical evaluation of the PSPL system was conducted including measurements of sensitometric response, modulation transfer function (MTF), noise power spectrum (NPS), noise equivalent quanta (NEQ) and detective quantum efficiency (DQE). These measurements were compared with results obtained previously for Kodak Ektaspeed (E-speed) film. The results of the evaluation indicate that the PSPL system may be capable of operating at exposures up to 80% lower than for film with comparable image quality.

Documented dental attendance patterns during childhood and adolescence

This 6-year retrospective study investigated the dental visiting habits of 263 working class adolescents in Greater Manchester. The aims of the study were to determine when young people were most likely to change their attendance patterns and to identify which subjects were most likely to stop seeking routine care. The frequency and reasons for all dental attendances made over a 6-year period were documented using clinical notes from general practices and community clinics. At the end of the study period, when the subjects were 13-15 years old, 62% were found to be maintaining an asymptomatic pattern of attendance, that is attending for examinations in the absence of symptoms. Sixteen per cent had stopped attending for check-ups and throughout the 6 years 10% attended only when they had symptoms or very rarely for check-ups. The number of subjects seeking routine care declined from the age of 9 years and those who continued to attend for examinations did so with a reduced frequency than when they were younger. It is concluded that encouragement to continue asymptomatic attendance should commence during the last years at primary school (10-11 years of age), a strategy which could result in up to 90% of the population of young adults retaining an asymptomatic dental attendance pattern.

Industry-university collaborations: a necessity for the future

OBJECTIVES

The aim of this discussion document is to consider the potential benefits of collaborations between universities and industry. Universities and industry now exist in a harsh and competitive economic climate. Indeed, their very survival depends increasingly on their ability and willingness to adapt to an unprecedented pace of change. There are a number of compelling reasons for universities and industry to undertake collaborative research. The costs of research have escalated. Universities, of necessity, are increasingly seeking financial support from industry as conventional sources of funding have been systematically reduced. Companies can no longer be self sufficient in terms of the science and technology needed for success. The strength of universities is their science base, and industry recognizes that the rapid exploitation of scientific advances is the key to its survival. Both organizations can benefit from collaborative research programmes. Universities are able to make additional staff appointments which add to their intellectual resource and reputation. In addition the purchase of equipment enhances their infrastructure.

CONCLUSIONS

Industry has the opportunity to recognize the potential relevance and value of funded research and must harness and commercially exploit new knowledge as rapidly as possible. Ultimately such collaboration will give rise to new approaches to the prevention, diagnosis and treatment of dental diseases with benefits to all concerned.

The role of fluoride dentifrices in a national strategy for the oral health of children

The Department of Health's recent publication 'An Oral Health Strategy for England' proposes a number of targets for improving the oral health of children by the year 2003. It recognises that the prevalence and severity of dental caries have decreased considerably in England over the last 25 years but, water fluoridation apart, it suggests no specific measures to ensure that this improvement continues. There is evidence to suggest that in many regions this will not be sufficient, and that in the medium term a more coordinated approach involving government, the profession and commerce is required.

A new large-scale process for taxol and related taxanes from Taxus brevifolia

PURPOSE

In view of the demonstrated antitumor activity of taxol, ready availability of the drug is important. The current isolation methods starting from the bark of Taxus brevifolia involve multiple manipulations, leading to only taxol and in a yield of 0.01%. A new process consisting of a single reverse phase column is introduced here, and the present purpose is to determine its large scale applicability.

METHODS

The chloroform extractable fraction of the bark of T. brevifolia is applied directly on to a C-18 bonded silica column in 25% acetonitrile/water, with elution using a step gradient: 30-50% acetonitrile/water. On standing, eight different taxanes, including taxol, crystallize out directly from different fractions. The crystals are filtered and purified further by recrystallization. Taxol and four other taxanes are purified this way. The other three require a short silica column. Taxol is freed from cephalomannine by selective ozonolysis.

RESULTS

The large scale process gave taxol (0.04%), 10-deacetylbaccatin III (0.02%), 10-deacetyl taxol-7-xyloside (0.1%), 10-deacetyl taxol-C-7-xyloside (0.04%), 10-deacetyl cephalomannine-7-xyloside (0.006%), taxol-7-xyloside (0.008%), 10-deacetyl taxol (0.008%) and cephalomannine (0.004%). Processing of the needles of T. brevifolia gave brevifoliol (0.17%), and that of the wood, 10-deacetyl taxol-C-7-xyloside (0.01%) and 10-deacetyl taxol-C.

CONCLUSIONS

The reverse phase column process is simpler (one column, direct crystallization), more efficient (eight taxanes obtained simultaneously) and also gives higher yields.

A 30-month study investigating the effect of adding triclosan/copolymer to a fluoride dentifrice

The aims of the study were (1) to compare the anticaries efficacy of a silica abrasive dentifrice containing 0.24% NaF and 0.3% triclosan/2.0% copolymer with a similar dentifrice without the triclosan/copolymer and (2) to study any disturbance of the oral mucosa associated with the test formulation. A double-blind, random, unsupervised, 30-month longitudinal clinical trial was conducted on 3,462 children who were initially 11-13 years of age. Two trained and calibrated dentists each examined approximately half the children. Examinations were undertaken at baseline, 15 months and 30 months. No significant differences were found between the DFS or DFT mean increments for the two dentifrice groups after 15 or 30 months. At 30 months the 90% confidence interval for the ratio of the mean increments satisfied the ADA criteria for equivalence. It is concluded that a 0.24% NaF/silica abrasive dentifrice containing 0.3% triclosan/2.0% copolymer is equivalent in its anticaries efficacy to a similar dentifrice without the addition of triclosan/copolymer. No side effects attributable to the test or control dentifrices were observed at any time during the study.

Age-cohort differences in treating symptoms of mental illness: a process approach

This study examines age-cohort differences in conceptually organizing, observing, and responding to unclustered symptoms of mental illness. Older (M = 70.8) and younger (M = 19.9) adults sorted symptoms of depression, schizophrenia, and age-associated changes into similarity groupings. Hierarchical cluster analysis showed that both older and younger adults sorted the statements similarly, although labels given for depressive symptoms differed across groups. Participants then reported which symptoms they had observed within their families and listed what actions were taken. Age groups showed significant differences in symptom reporting, with older individuals observing depressive symptoms less frequently. There were small differences in the kinds of actions reported. These results suggest that differences in help-seeking behavior for mental illness may be explained by differences in the way symptoms are observed by younger and older cohorts.

Age-cohort differences in treating symptoms of mental illness: a process approach

This study examines age-cohort differences in conceptually organizing, observing, and responding to unclustered symptoms of mental illness. Older (M = 70.8) and younger (M = 19.9) adults sorted symptoms of depression, schizophrenia, and age-associated changes into similarity groupings. Hierarchical cluster analysis showed that both older and younger adults sorted the statements similarly, although labels given for depressive symptoms differed across groups. Participants then reported which symptoms they had observed within their families and listed what actions were taken. Age groups showed significant differences in symptom reporting, with older individuals observing depressive symptoms less frequently. There were small differences in the kinds of actions reported. These results suggest that differences in help-seeking behavior for mental illness may be explained by differences in the way symptoms are observed by younger and older cohorts.