W.K. Seow

Oral Colonization of Streptococcus mutans in Six-month-old Predentate Infants

We hypothesize that S. mutans colonization occurs more frequently in pre-term children due to their relative immaturity. In this study of 172 predentate, six-month-old infants, we found that 50% of pre-term and 60% of full-term children harbored S. mutans. The colonization was confirmed by repeat sampling. Although there were minor differences, factors associated with S. mutans infection in pre-term and full-term infants were generally similar. In both groups, increased frequency of sugar was ranked the most important factor (p < 0.001), followed by breast-feeding (p < 0.001), and habits which allowed saliva transfer from mother to infant (p < 0.01). By contrast, non-colonization of S. mutans was associated with multiple courses of antibiotics (p < 0.001). Compared with pre-term children, there were higher percentages of full-term who had night feedings and consumed sugar during sleep times. Mothers with infected infants had S. mutans levels > 5 x 105 CFU/mL saliva (p < 0.001), poorer oral hygiene, more periodontal disease, and lower socio-economic status (p < 0.02) and snacked frequently (p < 0.001), compared with mothers with non-infected infants.

A Longitudinal Study of Streptococcus mutans Colonization in Infants after Tooth Eruption

We previously reported that, before tooth eruption, over one-half of infants aged 6 mos were already infected with Streptococcus mutans. The aim of this investigation was to determine the colonization of S. mutans after tooth eruption in the same cohort of 111 infants (35 pre-term, 76 full-term). Our results showed that S. mutans colonization increased with increasing age, so that by 24 mos of age, 84% harbored the bacteria (p < 0.01). The mean and median ages of S. mutans colonization in dentate infants were 15.7 mos and 16.0 mos, respectively. Factors associated with S. mutans colonization were sweetened fluids taken to bed (p < 0.01), frequent sugar exposure (p < 0.03) and snacking (p < 0.03), sharing of foods with adults (p < 0.03), and maternal S. mutans levels of > 105 CFU/mL (p < 0.02). In contrast, non-colonization of S. mutans was associated with toothbrushing (p < 0.03) and multiple courses of antibiotics (p < 0.001). Analysis of our data establishes the timing of S. mutans colonization in children from birth to 24 mos of age.

Dental erosion in children: a literature review.

Dental erosion is increasingly recognized as a common condition in paediatric dentistry with complications of tooth sensitivity, altered aesthetics and loss of occlusal vertical dimension. The prevalence of erosion in children has been reported to range from 10% to over 80%. The primary dentition is thought to be more susceptible to erosion compared to the permanent dentition due to the thinner and less mineralized enamel. The aim of this paper was to critically review dental erosion in children with regards to its prevalence, aetiology, diagnosis and prevention. The associations between erosion and other common conditions in children such as caries and enamel hypoplasia are also discussed.

Case-Control Study of Early Childhood Caries in Australia

The aim of this case-control study of 617 children was to investigate early childhood caries (ECC) risk indicators in a non-fluoridated region in Australia. ECC cases were recruited from childcare facilities, public hospitals and private specialist clinics to source children from different socioeconomic backgrounds. Non-ECC controls were recruited from the same childcare facilities. A multinomial logistic modelling approach was used for statistical analysis. The results showed that a large percentage of children tested positive for Streptococcus mutans if their mothers also tested positive. A common risk indicator found in ECC children from childcare facilities and public hospitals was visible plaque (OR 4.1, 95% CI 1.0–15.9, and OR 8.7, 95% CI 2.3–32.9, respectively). Compared to ECC-free controls, the risk indicators specific to childcare cases were enamel hypoplasia (OR 4.2, 95% CI 1.0–18.3), difficulty in cleaning child’s teeth (OR 6.6, 95% CI 2.2–19.8), presence of S. mutans (OR 4.8, 95% CI 0.7–32.6), sweetened drinks (OR 4.0, 95% CI 1.2–13.6) and maternal anxiety (OR 5.1, 95% CI 1.1–25.0). Risk indicators specific to public hospital cases were S. mutans presence in child (OR 7.7, 95% CI 1.3–44.6) or mother (OR 8.1, 95% CI 0.9–72.4), ethnicity (OR 5.6, 95% CI 1.4–22.1), and access of mother to pension or health care card (OR 20.5, 95% CI 3.5–119.9). By contrast, a history of chronic ear infections was found to be protective for ECC in childcare children (OR 0.28, 95% CI 0.09–0.82). The biological, socioeconomic and maternal risk indicators demonstrated in the present study can be employed in models of ECC that can be usefully applied for future longitudinal studies.

Identification of cathepsin C mutations in ethnically diverse Papillon-Lefèvre syndrome patients

INTRODUCTION Papillon-Lefèvre syndrome (PLS) is an autosomal recessive disorder characterised by palmoplantar keratoderma and severe, early onset periodontitis, which results from deficiency of cathepsin C activity secondary to mutations in the cathepsin C gene. To date, 13 different cathepsin C mutations have been reported in PLS patients, all of which are homozygous for a given mutation, reflecting consanguinity. AIM To evaluate the generality of cathepsin C mutations in PLS, we studied an ethnically diverse group of 20 unrelated families. METHODS Mutations were identified by direct automated sequencing of genomic DNA amplified for exonic regions and associated splice site junctions of the cathepsin C gene. Long range PCR was performed to determine the genomic structure of the cathepsin C gene. RESULTS The cathepsin C gene spans over 46 kb, with six introns ranging in size from 1.6 to 22.4 kb. Eleven novel mutations and four previously reported mutations were identified in affected subjects from 14 families. Missense mutations were most common (9/15), followed by nonsense mutations (3/15), insertions (2/15), and deletions (1/15). Among these 14 probands, two were compound heterozygotes. Affected subjects with transgressions of the dermal lesions onto the knees or elbows or both had mutations in both the pro- and mature regions of the enzyme, although most were in the mature region. CONCLUSION Mutations in the mature region of cathepsin C were more likely to be associated with the transgressions of the dermatological lesions, although the results were not statistically significant. A comprehensive list of all cathepsin C mutations described to date, representing 25 mutations from 32 families with PLS and related conditions, is also presented.

Identification of the enamelin (g.8344delG) mutation in a new kindred and presentation of a standardized ENAM nomenclature

The amelogenesis imperfectas (AI) are a genetically heterogeneous group of diseases that result in defective development of tooth enamel. Although X-linked, autosomal dominant and autosomal recessive forms of AI have been clinically characterized, only two genes (AMELX and ENAM) have been associated with AI. To date, three enamelin (ENAM) mutations have been identified. These mutations cause phenotypically diverse forms of autosomal dominant AI. Detailed phenotype-genotype correlations have not been performed for autosomal dominant AI due to ENAM mutations. We identified a previously unreported kindred segregating for the ENAM mutation, g.8344delG. Light and electron microscopy analyses of unerupted permanent teeth show the enamel is markedly reduced in thickness, lacks a prismatic structure and has a laminated appearance. Taken together these histological features support the enamelin protein as being critical for the development of a normal enamel thickness and that it likely has a role in regulating c-axis crystallite growth. Because there is growing molecular and phenotypic diversity in the enamelin defects, it is critical to have a nomenclature and numbering system for characterizing these conditions. We present a standardized nomenclature for ENAM mutations that will allow consistent reporting and communication.

Association of Streptococcus mutans Infection and Oral Developmental Nodules in Pre-dentate Infants

Since dental caries may present soon after tooth eruption, we hypothesized that colonization of Streptococcus mutans can occur in the predentate stages. In this study, we examined S. mutans colonization and its association with oral developmental nodules (Bohns nodules) in 60 pre-term and 128 full-term, three-month-old infants. Overall, S. mutans was cultured from 30% (56/188) of the infants, and oral developmental nodules were noted in 55% (103/188). Compared with the pre-term, full-term infants showed a higher prevalence of S. mutans (34% vs. 20%, p < 0.02) as well as developmental nodules (61% vs. 42%, p < 0.05). In both groups, S. mutans was positively associated with numbers of developmental nodules in a dose-response relationship (p < 0.001), and with maternal salivary levels of the bacteria (p = 0.03). The permanence of S. mutans infection was confirmed by repeat saliva sampling at 6 months of age. Our results thus showed that many infants have already acquired S. mutans at 3 months of age, prior to tooth eruption.

A literature review of dental erosion in children.

Dental erosion is increasingly recognized as a common condition in paediatric dentistry with complications of tooth sensitivity, altered aesthetics and loss of occlusal vertical dimension. The prevalence of erosion in children has been reported to range from 10% to over 80%. The primary dentition is thought to be more susceptible to erosion compared to the permanent dentition due to the thinner and less mineralized enamel. The aim of this paper was to critically review dental erosion in children with regards to its prevalence, aetiology, diagnosis and prevention. The associations between erosion and other common conditions in children such as caries and enamel hypoplasia are also discussed.

Inhibition of prostaglandin and leukotriene generation by the plant alkaloids tetrandrine and berbamine

We compared the effects of two bisbenzylisoquinoline compounds on leukotriene and prostaglandin generation by human monocytes and neutrophils. The results show that tetrandrine had a much greater effect than berbamine on leukotriene generation. However, both compounds were equally potent in suppression of prostaglandin generation. This inhibitory effect on prostaglandin generation can be overcome by exogenous arachidonic acid (AA), suggesting that the site of inhibition is not on the cyclooxygenase enzyme complex, but more proximally on the phospholipase-mediated release of AA from the cell membrane, similar to the action of corticosteroids. These results, together with previous findings of inhibitory effects on other inflammatory mediators such as histamine, platelet-activating-factor (PAF) and interleukin 1 (IL-1) indicate that these plant alkaloids may be useful lead compounds for the development of a new class of anti-inflammatory drugs.

Anti-inflammatory and immunosuppressive properties of the bis-benzylisoquinolines: in vitro comparisons of tetrandrine and berbamine

Tetrandrine and berbamine are two naturally occurring analogues with a bis-benzylisoquinoline structure. Comparative in vitro studies show that tetrandrine has significantly greater suppressive effects on adherence, locomotion and 3H-deoxyglucose uptake of neutrophils, as well as the mitogen-induced lymphocyte responses and mixed lymphocyte reactions. Also, tetrandrine displayed anti-oxidant activity while berbamine did not. By contrast, berbamine demonstrated a significantly greater capacity for inhibition of NK cell cytotoxicity. These results show that tetrandrine is superior to berbamine in most aspects of anti-inflammatory and immunosuppressive activity. Since these two alkaloids differ by only one substitution in the side chain of one of the benzene rings, these findings may provide further insight into structure-activity relationships and clues to the synthesis and development of active analogues of this promising class of drugs for the treatment of chronic inflammatory diseases.