Systematic review of hearing loss in dental professionals

BACKGROUND

Hearing loss leads to increased irritability and disengagement in social activities and conversations, which may impact quality of life. Dental professionals are at risk of developing hearing loss through daily exposure to noise from a wide range of equipment that produces significantly high decibels and noise frequencies.

AIMS

The aim of this systematic review was to investigate the risk of hearing loss in dental professionals, including dentists, dental specialists, dental hygienists and dental assistants.

METHODS

This review was conducted following the Cochrane Handbook for Systematic Reviews. PubMed, Scopus, Embase, Cochrane, Science Direct, Google Scholar and ProQuest were searched up to March 2023. Seventeen of 416 studies met the inclusion criteria. Quality assessment was performed according to the Newcastle-Ottawa Scale for cohort and case-control studies, and a modified version of this tool for cross-sectional studies.

RESULTS

The majority of included studies (82%) found a positive association with hearing loss for dentists and dental specialists, with years of clinical experience identified as a prominent risk factor. Dental hygienists and dental assistants were less commonly reported in the literature. Difference between the left and right ears was found in 71% of studies, with the left ear more affected in both dentists and dental assistants due to proximity to the noise-inducing equipment.

CONCLUSIONS

Dental professionals are at risk of hearing loss in their workplace, especially linked to years of clinical experience, which highlights the need for prevention and appropriate ear-protective devices.

Salivary characteristics and dental caries experience in remote Indigenous children in Australia: a cross-sectional study

Background

While associations between salivary characteristics and dental caries have been well studied, we are not aware of this being assessed in a remote Indigenous child population, where lifestyles may be different from urban children. Our aim was to assess associations between caries experience and putative biomarkers in saliva, accounting for oral hygiene and dietary habits.

Methods

Children attending schools in an Indigenous community in remote north Queensland, Australia were invited to an oral examination by qualified and calibrated examiners. Salivary flow rate, pH, buffering capacity and loads of mutans streptococci (MS), lactobacilli (LB) and yeasts were determined. Also, data on tooth brushing frequency and soft drinks consumption were obtained via a questionnaire. Caries experience was recorded by the International Caries Detection and Assessment System (ICDAS-II), and quantified as decayed, missing and filled surfaces. Relationships between the salivary variables and the cumulative caries experience (dmfs+DMFS) in the deciduous and permanent dentitions were examined by multivariate analyses to control the effect of confounders.

Results

The mean cumulative decayed (DS + ds), missing (MS + ms) and filled (FS + fs) surfaces were 3.64 (SD: 4.97), 1.08 (4.38) and 0.79 (1.84) respectively. Higher salivary MS and LB counts, low tooth brushing frequency and daily soft drink consumption were significantly related to greater caries experience. Caries experience was about twice in those with ≥10^5 CFU/ml saliva counts of MS (mean = 6.33, SD: 8.40 vs 3.11, 5.77) and LB (7.03, 7.49 vs 4.41, 8.00). In the fully-adjusted multivariate model, caries experience in those with higher counts of MS and LB were 51 and 52% more than those with lower counts.

Conclusions

As with studies in other populations, childhood salivary counts of MS and LB were significantly associated with greater caries experience in this remote Indigenous community. To address the serious burden of oral disease, we are researching ways to promote a healthy oral environment by encouraging good dietary habits, and emphasising the importance of daily tooth brushing with a fluoridated toothpaste. Our ongoing longitudinal studies will indicate the success of measures employed to reduce the counts of bacteria closely associated with cariogenesis and their impact on caries increment.

Trial registration

Australian New Zealand Clinical Trials Registry (ANZCTR), No: ACTRN12615000693527; date of registration: 3rd July 2015.

Effectiveness of water fluoridation in caries reduction in a remote Indigenous community in Far North Queensland

BACKGROUND

Children in remote Indigenous communities in Australia have levels of dental caries much greater than the national average. One such, the Northern Peninsula Area of Far North Queensland (NPA), had an oral health survey conducted in 2004, shortly before the introduction of fluoridated, reticular water. Children were again surveyed in 2012, following five years exposure.

METHODS

An oral examination was conducted on all consenting children enrolled in schools across the community, using WHO Basic Oral Health Survey methodology.

RESULTS

Few teeth had restorations in both surveys. Age-weighted overall caries prevalence and severity declined from 2005 to 2012 by 37.3%. The effect was most marked in younger children, dmft decreasing by approximately 50% for ages 4-9 years; at age 6, mean decayed score decreased from 5.20 to 3.43. DMFT levels also decreased by almost half in 6-9 year olds. However, significant unmet treatment needs exist at all ages.

CONCLUSIONS

There has been considerable improvement in child dental health in the NPA over the past 6-7 years. In light of continued poor diet and oral hygiene, water fluoridation is the most likely explanation. The cost-effectiveness for this small community remains an issue which, in the current climate of political antagonism to water fluoridation in many quarters, requires continued study.

Bortezomib and TRAIL: a perfect match for apoptotic elimination of tumour cells?

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine that selectively eradicates tumour cells via specific cell surface receptors and is intensively explored for use as a novel anticancer approach. To enhance the efficacy of TRAIL receptor agonists the proteasome inhibitor bortezomib is one of the most potent sensitizers. Here we review the main mechanisms underlying bortezomib-dependent TRAIL sensitization, including stimulation of apoptosis by increasing expression of TRAIL receptors, reduction of cFLIP and enhancement of caspase 8 activation, and modulation of Bcl-2 family proteins and inhibitor of apoptosis proteins (IAPs). Concomitantly, pro-survival signals are suppressed such as elicited by NF-κB and Akt. The different preclinical tumour models explored with this combination, including primary tumour (stem) cells, stroma co-culture and mice models, are discussed, as well as possible hurdles for clinical activity. Collectively, anticipating a solid rationale for bortezomib-TRAIL combination and very promising preclinical results, its clinical activity remains to be demonstrated.

Vertical and horizontal integration of knowledge and skills - a working model

The new integrated outcomes-based curriculum for dentistry was introduced at the University of Pretoria in 1997. The first participants graduated at the end of 2001. Educational principles that underpin the new innovative dental curriculum include vertical and horizontal integration, problem-oriented learning, student-centred learning, a holistic attitude to patient care and the promotion of oral health. The aim of this research project was to develop and assay a model to facilitate vertical integration of knowledge and skills thereby justifying the above mentioned action. The learning methodology proposed for the specific outcome of the Odontology module, namely the diagnosis of dental caries and the design of a primary preventive programme, included problem-solving as the driving force for the facilitation of vertical and horizontal integration, and an instructional design for the integration of the basic knowledge and clinical skills into a single learning programme. The paper describes the methodology of problem-oriented learning as applied in this study together with the detail of the programme. The consensus of those teachers who represent the basic and clinical sciences and who participate in this learning programme is that this model is practical and can assist vertical as well as horizontal integration of knowledge.

The impact of a school dental service on the periodontal health and oral hygiene status of 6-year-old Sowetan learners

The public oral health sector offers essentially two types of services to learners viz, (i) clinical services, where curative and restorative treatment, and prophylactic care is provided, and (ii) school-based services which focus on a primary preventive approach to oral health that consists of health promotion and specific protection initiatives e.g. brushing programmes. Learners may be exposed to a combination of clinical and school-based services or to school-based services only. The objective of this study was to compare the impact of services delivered by the public oral health sector on periodontal health and oral hygiene status of 6-year-old Sowetan learners to a control group who were not exposed to any organised oral health programme. Follow-up visits were conducted every 6 months from baseline for a period of 18 months. A significant decrease in the percentage of learners with healthy periodontal tissues and a significant increase in the percentage of learners with gingival bleeding was observed for all three cohorts. Oral hygiene performance, assessed according to the Patient Hygiene Performance (PHP) index, demonstrated no improvement after 18 months, although the mean scores remained within the 'fair' interval. No significant benefit could be demonstrated in providing a clinical services component in combination with school-based services. No significant positive impact of the brushing programme on oral hygiene and periodontal health status of learners was observed after 18 months when compared to a control group.

Conformational comparison of five follicular fluid meiosis-activating sterol-related active and inactive compounds

The crystal structures of five follicular fluid meiosis-activating sterol-related Delta(8,14)-sterol compounds are presented. These are 4,4-dimethyl-23-phenyl-24-nor-5alpha-chola-8,14-dien-3beta-ol, C(31)H(44)O, 4,4-dimethyl-22-phenyl-23,24-dinor-5alpha-chola-8,14-dien-3beta-ol, C(30)H(42)O, (20R)-4,4-dimethyl-22-oxa-5alpha,20-cholesta-8,14,24-trien-3beta-ol, C(28)H(44)O(2), 4,4-dimethyl-23-phenyl-22-oxa-24-nor-5alpha-chola-8,14-dien-3beta-ol-water (4/1), 4C(30)H(42)O(2).H(2)O, and 4,4-dimethyl-5alpha-cholesta-8,14-dien-3-one, C(29)H(46)O. Two of the derivatives are inactive and three are active as agonists. Preliminary structure-activity relationship studies showed that the positions of the double bonds in the skeleton and the structures of the side chains are important determinants for activity. The conformations of the skeletons were compared with double-bond isomers retrieved from the Cambridge Structural Database [Allen & Kennard (1993). Chem. Des. Autom. News, 8, 1, 31-37]; no significant differences were found. Thus, conformational changes induced by the double bonds are not discriminative with respect to the activity of the compounds. Comparisons of the side-chain conformations of active and inactive structures revealed that the crystal structures were not conclusive as far as correlation of conformation and activity of the side chains were concerned.

Trends in treatment performed in the Phelophepa Dental Clinic: 1995-2000

Mobile clinics are a cost-effective method of meeting the dental needs of rural communities in South Africa. Phelophepa, the first primary health care train of its kind world-wide, provides eye care, education, medicine, basic health care and since June 1995 dental treatment to rural communities. All services are rendered by students under supervision of qualified staff. The aim of this study was to analyse and report the data for treatment performed in the dental clinic from June 1995 to May 2000. During its first five years of operation, dental services were provided at 183 towns in all provinces except Gauteng. Of the 42,073 patients treated during this time (an average of 229.9 per town), 67.4% were adults. 71.3% of the 103,283 procedures performed were extractions, 15.7% could be classified as preventive with the remaining 13% as restorative procedures. The average value of the service provided to each patient was R218.53. The exposure of dental, dental therapy and oral hygiene students to rural areas of South Africa serves the important purpose of sensitising students to the realities of oral diseases in these communities.

Relation between the molecular electrostatic potential and activity of some FF-MAS related sterol compounds

Follicular Fluid-Meiosis Activating Sterol (FF-MAS) is a compound important for maturation of gametes in mammals. Therefore, it may serve as a lead compound for a novel method of contraception. We studied the Molecular Electrostatic Potential of a series of active and inactive analogues of FF-MAS. We find that double bond configurations required for activity result in a local negative electrostatic potential which is larger as well as more dense compared to those of inactive molecules. We therefore hypothesize that the interaction energy of the double bond system of the MAS compounds with its receptor substantially contributes to the overall interaction energy. This notion is supported by interaction studies of the electrostatic potential originating from the double bonds in crystal structures of cholesterol and four MAS-derived Delta(8,14) structures synthesized and crystallized by us. In addition, we were able to derive a pharmacophore model that relates the local average ESP and its distance to the 3beta-OH oxygen atom to the activity of the molecules.

Specific protein dynamics near the solvent glass transition assayed by radiation-induced structural changes

The nature of the dynamical coupling between a protein and its surrounding solvent is an important, yet open issue. Here we used temperature-dependent protein crystallography to study structural alterations that arise in the enzyme acetylcholinesterase upon X-ray irradiation at two temperatures: below and above the glass transition of the crystal solvent. A buried disulfide bond, a buried cysteine, and solvent exposed methionine residues show drastically increased radiation damage at 155 K, in comparison to 100 K. Additionally, the irradiation-induced unit cell volume increase is linear at 100 K, but not at 155 K, which is attributed to the increased solvent mobility at 155 K. Most importantly, we observed conformational changes in the catalytic triad at the active site at 155 K but not at 100 K. These changes lead to an inactive catalytic triad conformation and represent, therefore, the observation of radiation-inactivation of an enzyme at the atomic level. Our results show that at 155 K, the protein has acquired--at least locally--sufficient conformational flexibility to adapt to irradiation-induced alterations in the conformational energy landscape. The increased protein flexibility may be a direct consequence of the solvent glass transition, which expresses as dynamical changes in the enzyme's environment. Our results reveal the importance of protein and solvent dynamics in specific radiation damage to biological macromolecules, which in turn can serve as a tool to study protein flexibility and its relation to changes in a protein's environment.

SuperStar: comparison of CSD and PDB-based interaction fields as a basis for the prediction of protein-ligand interactions

SuperStar is an empirical method for identifying interaction sites in proteins, based entirely on the experimental information about non-bonded interactions, present in the IsoStar database. The interaction information in IsoStar is contained in scatterplots, which show the distribution of a chosen probe around structure fragments. SuperStar breaks a template molecule (e.g. a protein binding site) into structural fragments which correspond to those in the scatterplots. The scatterplots are then superimposed on the corresponding parts of the template and converted into a composite propensity map. The original version of SuperStar was based entirely on scatterplots from the CSD. Here, scatterplots based on protein-ligand interactions are implemented in SuperStar, and validated on a test set of 122 X-ray structures of protein-ligand complexes. In this validation, propensity maps are compared with the experimentally observed positions of ligand atoms of comparable types. Although non-bonded interaction geometries in small molecule structures are similar to those found in protein-ligand complexes, their relative frequencies of occurrence are different. Polar interactions are more common in the first class of structures, while interactions between hydrophobic groups are more common in protein crystals. In general, PDB and CSD-based SuperStar maps appear equally successful in the prediction of protein-ligand interactions. PDB-based maps are more suitable to identify hydrophobic pockets, and inherently take into account the experimental uncertainties of protein atomic positions. If the protonation state of a histidine, aspartate or glutamate protein side-chain is known, specific CSD-based maps for that protonation state are preferred over PDB-based maps which represent an ensemble of protonation states.

Caries prediction factors in children with primary dentition

Previous studies have indicated an association between the dmft and the lactobacilli counts in small children. This study evaluated and compared a number of salivary factors that could have an effect on caries progression in two groups of children with primary dentition (group 1 = 3-6 years; group II = 9 years). The average dmft score was higher for group II. The dmft score of group I consisted mainly of a large dt component, while in group II a large ft component was found. Lactobacilli were present in 44.83% of group I and in 77.27% of group II. Significant positive correlations were found for group I between the dt component of the dmft and lactobacilli count (P < 0.05, r = 0.48) as well as the total dmft and lactobacilli count (P < 0.05, r = 0.45). Significant positive correlations were found for group II between the dmft and lactobacilli count (P < 0.05, r = 0.39) and the plaque index and lactobacilli count (P < 0.05, r = 0.31). Significant correlations between the dmft and the prevalence of lactobacilli in the oral cavity were also indicated (group I: P < 0.05, r = 0.45; group II: P < 0.05, r = 0.36). Significant correlations confirmed the association of lactobacilli with the caries process and indicated the reliability of lactobacilli counts to determine caries activity. Correlations between the dmft and the prevalence of lactobacilli in the oral cavity indicated the possibility of an excellent but simple test for the prediction of caries susceptibility in children.

The structure of leech anti-platelet protein, an inhibitor of haemostasis

Leech anti-platelet protein (LAPP) from the leech Haementeria officinalis is a collagen-binding protein that inhibits the collagen-mediated adhesion of blood platelets. The crystal structure of recombinant LAPP has been determined using single isomorphous replacement with anomalous scattering combined with solvent flattening and threefold molecular averaging. The model of LAPP has been refined to 2.2 A resolution (R factor 21.5%; free R factor 24.0%). LAPP contains an 89-residue C-terminal domain consisting of a central six-stranded antiparallel beta-sheet flanked on one side by an alpha-helix and on the other side by two extended loops with little secondary structure. A 36-residue N-terminal region is not visible in the electron-density map. This region is rich in glycine and lacks hydrophobic residues. It probably does not have a compact globular fold, but instead has an extended conformation and is flexible. The crystal packing suggests that LAPP may form tightly interacting dimers. The fold of the C-terminal domain of LAPP closely resembles that of the N-domain of hepatocyte growth factor (HGF), which classifies LAPP as a PAN domain. However, no significant sequence homology exists between LAPP and other PAN domains. Common structural features between LAPP and the HGF N-domain include two disulfide bonds that link the alpha-helix to the central region of the protein and five residues with a conserved hydrophobic nature that are located in the core of the domain. These conserved structural features may be an important determinant of the PAN-domain type of fold.

Evaluation of Atraumatic Restorative Treatment restorations and sealants under field conditions

Conventional restorative procedures require the use of dental materials, expensive equipment, instruments and electricity. This makes dental restorations costly and limits the availability and accessibility of the service to areas where these facilities are available. The new philosophy of restorative care requires minimal intervention and advocates early interception of the caries process through the use of glass-ionomers as sealants and as restorations. This new approach makes dental care accessible to all members of society in developing countries. The aim of this study was to evaluate the use of Atraumatic Restorative Treatment (ART) restorations and sealants under field conditions. Both were assessed for their retentive properties and the development of secondary caries adjacent to the procedures. A longitudinal study design was followed. ART restorations and sealants were assessed at intervals of 6 and 12 months. After 12 months 56.5% of ART restorations were still present in the primary dentition and 84% in the permanent dentition. Of these 85.1% had no defects in the primary and 78.6% no defects in the permanent teeth. 72.3% of primary and 92% of permanent teeth on which ART restorations were placed had no caries after 1 year. Even though most of the sealants were absent due to poor retention after 12 months (89.6%), 98.9% of the teeth where the sealant was initially placed had no caries. Only 6.3% of sealants present had marginal defects. The ART technique is strongly recommended for the management of small, occlusal carious lesions in primary and permanent teeth.

Biophysical characterization of the influence of salt on tetrameric SecB

SecB is a tetrameric chaperone, with a monomeric molecular mass of 17 kDa, that is involved in protein translocation in Escherichia coli. It has been hypothesized that SecB undergoes a conformational change as a function of the salt concentration. To gain more insight into the salt-dependent behavior of SecB, we studied the protein in solution by dynamic light scattering, size exclusion chromatography, analytical ultracentrifugation, and small angle neutron scattering. The results clearly demonstrate the large influence of the salt concentration on the behavior of SecB. At high salt concentration, SecB is a non-spherical protein with a radius of gyration of 3.4 nm. At low salt concentration the hydrodynamic radius of the protein is apparently decreased, whereas the ratio of the frictional coefficients is increased. The protein solution behaves in a non-ideal way at low salt concentrations, as was shown by the analytical ultracentrifugation data and a pronounced interparticle effect observed by small angle neutron scattering. A possible explanation is a change in surface charge distribution dependent on the salt concentration in the solvent. We summarize our data in a model for the salt-dependent conformation of tetrameric SecB.

Fluoride concentration of bottled drinking waters

The use of bottled water and beverages may be a significant source of systemic fluoride and can therefore be considered as a risk factor for dental fluorosis in young children. The aim of this study was to determine the fluoride content of commercially available bottled drinking waters and to report on the accuracy of the labelling of fluoride concentration. Thirty brands of bottled water, classified as either spring (N = 19) or mineral (N = 11) water were evaluated. A fluoride ions-elective and a fluoride reference electrode were used to measure the fluoride concentrations. The average reading for each brand was compared with the fluoride content printed on the label. Only 56.7% (N = 17) of brands tested mention the fluoride concentration on the label, but 73.3% (N = 22) had a tested fluoride concentration of less than 0.3 ppm. Of the 8 brands testing higher than 0.3 ppm fluoride, 1 did not have the fluoride concentration labelled, while for another the tested fluoride concentration was much higher than the concentration printed on the label. When prescribing fluoride supplements, dentists should be aware of the fluoride content of bottled waters used by child patients, especially brands with a concentration higher than 0.3 ppm.

Solvent behaviour in flash-cooled protein crystals at cryogenic temperatures

The solvent behaviour of flash-cooled protein crystals was studied in the range 100--180 K by X-ray diffraction. If the solvent is within large channels it crystallizes at 155 K, as identified by a sharp change in the increase of unit-cell volume upon temperature increase. In contrast, if a similar amount of solvent is confined to narrow channels and/or individual cavities it does not crystallize in the studied temperature range. It is concluded that the solvent in large channels behaves similarly to bulk water, whereas when confined to narrow channels it is mainly protein-associated. The analogy with the behaviour of pure bulk water provides circumstantial evidence that only solvent in large channels undergoes a glass transition in the 100--180 K temperature range. These studies reveal that flash-cooled protein crystals are arrested in a metastable state up to at least 155 K, thus providing an upper temperature limit for their storage and handling. The results are pertinent to the development of rational crystal annealing procedures and to the study of temperature-dependent radiation damage to proteins. Furthermore, they suggest an experimental paradigm for studying the correlation between solvent behaviour, protein dynamics and protein function.

Identification of the collagen-binding site of the von Willebrand factor A3-domain

Von Willebrand factor (vWF) is a multimeric glycoprotein that mediates platelet adhesion and thrombus formation at sites of vascular injury. vWF functions as a molecular bridge between collagen and platelet receptor glycoprotein Ib. The major collagen-binding site of vWF is contained within the A3 domain, but its precise location is unknown. To localize the collagen-binding site, we determined the crystal structure of A3 in complex with an Fab fragment of antibody RU5 that inhibits collagen binding. The structure shows that RU5 recognizes a nonlinear epitope consisting of residues 962-966, 981-997, and 1022-1026. Alanine mutants were constructed of residues Arg(963), Glu(987), His(990), Arg(1016), and His(1023), located in or close to the epitope. Mutants were expressed as fully processed multimeric vWF. Mutation of His(1023) abolished collagen binding, whereas mutation of Arg(963) and Arg(1016) reduced collagen binding by 25-35%. These residues are part of loops alpha3beta4 and alpha1beta2 and alpha-helix 3, respectively, and lie near the bottom face of the domain. His(1023) and flanking residues display multiple conformations in available A3-crystal structures, suggesting that binding of A3 to collagen involves an induced-fit mechanism. The collagen-binding site of A3 is located distant from the top face of the domain where collagen-binding sites are found in homologous integrin I domains.

Cost evaluation for the implementation of water fluoridation in Gauteng

Regulations to implement water fluoridation in South Africa were promulgated in September 2000. Water providers are now compelled to fluoridate public water sources. In terms of Regulation 5(c) of the regulations, certain information regarding the cost of water fluoridation must be submitted to the Director General of Health. The purpose of this survey was to evaluate the cost of water fluoridation in Gauteng and to provide a model for similar calculations in other provinces. The following criteria were used to evaluate the cost of water fluoridation in Gauteng--per capita cost per year, cost-effectiveness analysis (CEA) and cost-benefit analysis (CBA). The calculated cost per capita per year was R0.73 while CEA showed that R3.95 will be spent to save 1 DMFT. The cost-benefit ratio based on the scale of benefits cost of a 2 surface plastic restoration was 0.04. Evaluation of cost for the implementation of water fluoridation in Gauteng was extremely favourable and a model to estimate the per capita figure is provided.

The relation between toothpaste usage and fluorosis: a cause for concern?

Fluoride-containing toothpaste is by far the most widespread source of fluoride in the world and after fluoridated water the most cost-effective at reducing dental caries. Of the seven current issues in the development of fluoride-containing toothpaste described by Holt & Murray (1997), five are either directly or indirectly related to the risk of developing fluorosis, a phenomenon which is on the increase in the industrialised world. The purpose of this study was to evaluate fluoride-containing toothpaste available to the South African public regarding the issues described by Holt & Murray (1997) and to relate the results to the possible development of fluorosis. The amount of fluoride ingested from toothpaste was calculated using the total fluoride concentration present in toothpaste, quantity of toothpaste used per brushing, mean percentage of toothpaste ingested and the 90th percentile of body weight. Results indicate that the "threshold" level of fluoride intake of 0.05 to 0.07 mg F/kg body weight/day beyond which dental fluorosis might occur (Burt, 1992), is exceeded when a ribbon of toothpaste was placed on a child's toothbrush at ages 2-3 years. 'Threshold' levels were ingested when placing a ribbon of toothpaste on the brush at ages 4 and 5 for all toothpaste as well as for a children's formulation containing 1000 microg F/g. Of all pastes studied, 41.9% of the packaging has information for the prevention of swallowing of paste and/or the supervision of children by adults when brushing. The dental profession, manufacturers of toothpaste and government all have a role to play in the prevention of fluorosis in the toothbrushing population of South Africa.

Laboratory analysis of fluoride containing toothpaste available in South Africa

Since the introduction of fluoridated toothpaste more than 30 years ago, it has become by far the most widespread source of fluoride in the world and after fluoridated water the most effective at reducing dental caries. Both the total soluble and the soluble ionic fluoride present in toothpaste are important in determining the effectiveness of the paste as it is important in remineralising demineralised lesions, a characteristic of fluoride which has proven to be the most important in preventing dental caries. The purpose of this study was to evaluate toothpaste currently available to the South African public regarding total soluble and soluble ionic fluoride. A variation of the method used by Grobler et al. (1983) and Du Preez et al. (1993) in previous studies conducted in South Africa was used in preparing the samples for fluoride analysis. Measurements of fluoride concentrations were done using an ionselective electrode. For all toothpaste studied (n=62), large variations occurred for the soluble ionic fluoride (mean = 318.44 microg F/g toothpaste; median = 139.69; standard deviation = 398.77). Correspondingly a mean total soluble fluoride of 848.84 microg F/g toothpaste was found (standard deviation = 189.35; median = 857.38). From this study it can be concluded that fluoride concentrations in toothpaste available to the South African public are in line with those found in the two previous South African studies. In the absence of artificially fluoridated water, toothpaste remains the most cost-effective strategy in the prevention of dental caries in South Africa.

Plant glycerol-3-phosphate-1-acyltransferase (GPAT): structure selectivity studies

Squash glycerol-3-phosphate-1-acyltransferase has been crystallized and the structure of the enzyme determined, at 1.9-A resolution, using multiple isomorphous replacement of the wild type and a series of individual cysteine mutants. Competitive in vitro substrate selectivity assays have been established that differentiate between selective and non-selective forms of the enzyme. Particular care was taken to use near-physiological concentrations of both substrates. Clear substrate selectivity can be demonstrated with the natural substrate acyl-acyl carrier protein but not with the substrate analogue acyl-CoA. The use of site-directed mutagenesis, coupled to three-dimensional structural determinations, should provide a rational basis for elucidating structural components important in determining the substrate selectivity of this enzyme.

Bis(4-propargyloxy-3-quinolylthio)methane

The molecular structure of the title compound, C(25)H(18)N(2)O(2)S(2), in the crystal is characterized by almost parallel quinoline and propargyl groups that point in opposite directions out of the quinoline planes. Intermolecular C[triple-bond]C-H...N hydrogen bonding is observed, but the hydrogen-bond geometry is poor.