Biomedical subjects

W K Seow

Publications and source records attributed to W K Seow.

At least 19 recordsLinked to original sources

PubMed2005

Spatial and temporal coordination of expression of immune response genes during Pseudomonas infection of horseshoe crab, Carcinoscorpius rotundicauda.

Knowledge on how genes are turned on/off during infection and immunity is lacking. Here, we report the co-regulation of diverse clusters of functionally related immune response genes in a horseshoe crab, Carcinoscorpius rotundicauda. Expressed sequence tag (EST) clusters for frontline immune defense, cell signalling, apoptosis and stress response genes were expressed or repressed spatio-temporally during the acute phase of Pseudomonas infection. An infection time course monitored by virtual Northern evaluation indicates upregulation of genes in blood cells (amebocytes) at 3-h postinfection, whereas most of the hepatopancreas genes remained down regulated over 72 h of infection. Thus, the two tissues orchestrate a coordinated and timely response to infection. The hepatopancreas probably immuno-modulates the expression of other genes and serves as a reservoir for later response, if/when chronic infection ensues. On the other hand, being the first to encounter pathogens, we reasoned that amebocytes would respond acutely to infection. Besides acute transactivation of the immune genes, the amebocytes maintained morphological integrity, indicating their ability to synthesise and store/secrete the immune proteins and effectors to sustain the frontline innate immune defense, while simultaneously elicit complement-mediated phagocytosis of the invading pathogen. Our results show that the immune response against Pseudomonas infection is spatially and temporally coordinated.

Animals↗

PubMed2005

Erosive effects of common beverages on extracted premolar teeth.

BACKGROUND: Dental erosion is highly prevalent today, and acidic drinks are thought to be an important cause. The aim of the present investigation was to determine the erosive potential of a range of common beverages on extracted human teeth. METHODS: The beverages were tested for their individual pHs using a pH meter. The clinical effects of the most erosive beverages were determined by the degree of etching and Vickers microhardness of enamel. RESULTS: The results showed that many common beverages have pHs sufficiently low to cause enamel erosion. Lime juice concentrate (pH 2.1) had the lowest pH, followed by Coca-cola and Pepsi (both with pH 2.3) and Lucozade (pH 2.5). The erosive potential of these beverages was demonstrated by the deep etching of the enamel after five minutes. The Vickers Hardness of enamel was reduced by about 50 per cent in the case of lime juice (p < 0.001) and 24 per cent in the case of Coca-cola (p < 0.004). Addition of saliva to 50 per cent (v/v) of Coca-cola completely reversed the erosive effects on the enamel. CONCLUSIONS: Although only a few of the beverages with the lowest pHs were tested, the present study showed that the most acidic drinks had the greatest erosive effects on enamel. While saliva was protective against erosion, relatively large volumes were required to neutralize the acidity.

Acids↗

PubMed2003

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.

Adult↗

PubMed2003

Immunoglobulins in saliva of preterm and full-term infants.

The aim of this longitudinal study was to determine salivary levels of total IgA, IgG and IgM in 84 preterm and 214 full-term infants, from birth to 18 months of age. Unstimulated whole saliva was collected from each infant at birth, and subsequently at 3-monthly intervals. Immunoglobulin levels were estimated using an ELISA technique. At birth, IgA was detected in 147/214 (69%) full-term infants but only 47/84 (56%) preterm infants (P < 0.01). In the case of IgG, 61% of full-term and 56% of preterm infants showed detectable levels, whereas IgM was found in 71% and 73%, respectively. Levels of IgA and IgG rose from birth to 18 months, whereas IgM levels did not change significantly. Increases in salivary levels of IgA were associated with introduction of solid foods (P < 0.001), as well as tooth eruption (P < 0.001). Our results indicate that the majority of full-term and preterm infants are orally immunocompetent at birth.

Chi-Square Distribution↗

PubMed2003

Diagnosis and management of unusual dental abscesses in children.

Although the majority of dental abscesses in children originate from dental caries or trauma, a few are associated with unusual conditions which challenge diagnosis and management. Recent research findings have shed light on these unusual entities and greatly improved understanding of their clinical implications. These conditions include developmental abnormalities such as dens invaginatus in which there is an invagination of dental tissues into the pulp chamber and dens evaginatus in which a tubercle containing pulp is found on the external surface of a tooth crown. In addition, inherited conditions which show abnormal dentine such as dentine dysplasia, dentinogenesis imperfecta, and osteogenesis imperfecta predispose the dentition to abscess formation. Furthermore, 'spontaneous' dental abscesses are frequently encountered in familial hypophosphataemia, also known as vitamin D-resistant rickets, in which there is hypomineralization of dentine and enlargement of the pulp. In addition to developmental conditions, there are also acquired conditions which may cause unusual dental abscesses. These include pre-eruptive intracoronal resorption which was previously known as 'pre-eruptive caries' or the 'fluoride bomb'. In addition, some undiagnosed infections associated with developing teeth are now thought to be the mandibular infected buccal cysts which originate from infection of the developing dental follicles. In the present paper, these relatively unknown entities which cause unusual abscesses in children are reviewed with the aim of updating the general practitioner in their diagnosis and management.

Abscess↗

PubMed2003

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 > 10(5) 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.

Age Factors↗

PubMed2002

Comparison of five selective media for the growth and enumeration of Streptococcus mutans.

BACKGROUND: Although a few growth media are available for selective isolation of the cariogenic bacteria, Streptococcus mutans (S. mutans), it is still unclear as to which is the most efficacious. This study compared the selectivity and sensitivity of five different media for growing a laboratory strain of S. mutans (NCTC 10449), and for enumerating S. mutans from teeth of a group of young children, aged 2-10 years. METHODS: The media tested in this study were mitis salivarius with bacitracin (MSB), mitis salivariuskanamycin-bacitracin (MSKB), glucose-sucrose-tellurite-bacitracin (GSTB), trypticase soy-sucrose-bacitracin (TYS20B) and tryptone-yeast-cysteine-sucrose-bacitracin (TYCSB) agars. These were prepared according to the respective manufacturer's instructions. RESULTS: The results showed that at concentrations of bacteria 1 x 10(3) to 1 x 10(10)/mL, the recovery of the laboratory S. mutans strain was highest in TYCSB agar, followed by in descending order by TYS20B, MSB, GSTB, and MSKB (p<0.01). Similar results were obtained using dental plaque samples collected from swabs of the teeth of a group of children. In the clinical samples, TYCSB again showed the highest recovery rates of S. mutans compared to the other four media. Results were reproduced at dilutions of the samples at 1:20 x 10(6) to 1:2 x 10(6), and S. mutans concentrations of 1.6 to 7.7 Log 10 CFU/mL. In addition, there were highest ratios of mutans to non-mutans bacteria in TYCSB compared to the other media, suggesting high selectivity of this media for mutans species. CONCLUSION: The results of our study suggest that TYCSB is the most sensitive and selective media for culture of S. mutans for laboratory and clinical studies.

Agar↗

PubMed2002

Oral health of children with gastro-esophageal reflux disease: a controlled study.

BACKGROUND: The aim of this study was to compare the dental health of children with gastro-esophageal reflux disease (GERD) with a healthy control group. METHODS: Dental examinations were conducted for 52 children (31 boys and 21 girls) with a definitive history of GERD. For every subject enrolled in the study, a healthy control sibling without the condition was recruited. Medical histories were obtained from medical records, and dental and dietary histories were obtained from parents. The teeth were examined for erosion, dental caries, and enamel hypoplasia, and sampled for Streptococcus mutans. RESULTS: The prevalence of erosion by teeth was found to be statistically significant between GERD patients (14 per cent) and controls (10 per cent) (p<0.05). GERD patients had erosion in more permanent teeth compared to controls (4 per cent vs 0.8 per cent, p<0.05), and more severe erosion (p<0.05). Caries experience was also higher in GERD patients compared to controls (p<0.05). Although there were more subjects with Streptococcus mutans in the GERD group compared to the control group (42 per cent vs 25 per cent), the difference was not statistically significant. CONCLUSIONS: Children with GERD have more erosion and dental caries compared to healthy controls and should be targeted for increased preventive and restorative care.

Case-Control Studies↗

PubMed2001

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 (Bohn's 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.

Alveolar Process↗

PubMed2001

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 10(5) 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.

Anti-Bacterial Agents↗

PubMed2000

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.

Cathepsin C↗

PubMed2000

A controlled study of the morphometric changes in the primary dentition of pre-term, very-low-birthweight children.

The aim of the present investigation was to compare the dimensions of the primary incisors from pre-term children and full-term controls. One hundred and eleven pre-term children, consisting of 86 very-low-birthweight (< 1,500 g), 25 low-birthweight (from 1,500 to 2,500 g), and 169 full-term, normal-birthweight (> 2,500 g) children, donated a total of 572 maxillary and mandibular primary central and lateral incisors for study. The teeth were measured by means of a digital micrometer. The results showed that there was a dose-response effect of birthweight on tooth size. The very-low-birthweight teeth showed the smallest dimensions, the normal-birthweight controls the largest, and the low-birthweight teeth intermediate dimensions (p < 0.001). In the maxillary primary central and lateral incisors, and the mandibular primary central incisors, very-low-birthweight teeth were from 6 to 11% smaller in both mesiodistal and faciolingual dimensions compared with normal-birthweight teeth (p < 0.001). The largest differences were observed in the maxillary lateral incisors, where mean decreases of 0.58 +/- 0.45 mm in mesiodistal and 0.50 +/- 0.40 mm in faciolingual dimensions (11% reduction in both measurements) were observed. In addition, in the mandibular and maxillary lateral incisors of very-low-birthweight children, the left-sided teeth were significantly smaller than those on the right side in both mesiodistal and faciolingual dimensions (p < 0.03).

Analysis of Variance↗

PubMed1998

Biological mechanisms of early childhood caries.

The present paper reviews biological issues in early childhood caries (ECC) in light of the current understanding of the field. Despite the general global decline in dental caries in the past decades, ECC has become a significant problem in many developing countries and some minority communities in western industrialized nations. Like other types of caries, ECC is caused by mutans streptococci that ferment dietary carbohydrates to produce acid attacks on susceptible teeth over a period of time. However, while the general etiology of ECC appears similar to that of other types of caries, the predisposing factors are still unclear. The biology of ECC may be modified by several factors unique to young children, related to the implantation of cariogenic bacteria, immaturity of the host defense systems, as well as behavioral patterns associated with feeding and oral hygiene in early childhood.

Acids↗

PubMed1998

Morphometric analysis of the primary and permanent dentitions in hemifacial microsomia: a controlled study.

Hemifacial microsomia (HFM), a developmental abnormality involving the first and second branchial arches, is one of the most common craniofacial abnormalities. Although the general presentations of hemifacial microsomia--such as unilateral microtia, macrostomia, and hypoplasia of the mandibular ramus and condyle--are wellknown, the effects on the teeth are not well-documented. This study examined the primary and permanent tooth dimensions of dental casts of 50 hemifacial microsomia patients compared with those of 50 normal control patients matched for sex and dental status. The results showed that the mesiodistal dimensions of the mandibular second primary molar and the mandibular permanent first molar teeth on the affected side in hemifacial microsomia were significantly smaller compared with those of control teeth (p < 0.001). Furthermore, in the maxillary and mandibular first permanent molars and the maxillary and mandibular first and second primary molars, the teeth in the apparently "normal" side of hemifacial microsomia were also significantly reduced in the mesiodistal dimensions. Comparison of overall dimensions revealed that all primary and permanent molars in hemifacial microsomia were significantly smaller in the mesiodistal dimensions compared with control teeth. A general gradient effect was observed, with the most posterior tooth in each arch being the most severely affected and no effect being seen in the canines and the incisors. These findings suggest that the dental lamina in hemifacial microsomia is affected, and support the hypothesis that its pathogenesis involves an abnormality of the neural crest. Furthermore, these results also support the concept that hemifacial microsomia is a bilateral rather than a unilateral condition.

Branchial Region↗

PubMed1997

Clinical diagnosis of enamel defects: pitfalls and practical guidelines.

Changes in enamel during its development are permanently recorded, and commonly present as either demarcated opacity, diffuse opacity, or enamel hypoplasia. Developmental enamel defects may provide clues regarding their aetiology, and this may have application in clinical dentistry, dental epidemiology and anthropology. However, the usefulness of these applications may be hampered by many pitfalls encountered in the detection and diagnosis of developmental enamel defects. The defects may be masked by saliva, dental plaque, and incorrect lighting. In addition, confounding effects of post-eruptive changes such as dental caries, attrition, and traumatic loss of tooth structure may impair the detection of developmental enamel defects. The non-specificity of appearance of enamel defects may make aetiologic diagnosis of enamel hypoplasia difficult. Furthermore, difficulty is often encountered in the relative timing of events in enamel hypoplasia, due to limited data on the chronology of development of the human dentition. In this review, pitfalls in the clinical assessment of enamel defects are discussed, and guidelines to overcome some of these difficulties are presented.

Amelogenesis↗

PubMed1997

Effects of preterm birth on oral growth and development.

Preterm and low birthweight children comprise approximately 6 per cent of all live births. They are prone to many serious medical problems during the neonatal period which may affect the development of oral tissues. The present paper reviews the results of this author's own decade of research into the oral development of preterm children in the light of current understanding of the field. Studies have shown a high prevalence of generalized enamel hypoplasia in the primary dentition of around 40-70 per cent in preterm children which is likely to be associated with low bone mineral stores. The clinical significance of enamel defects is poor aesthetics, and predisposition of the lesions to dental caries. Other dental defects observed in preterm children are localized enamel hypoplasia, crown dilacerations, and palatal distortions which are usually associated with traumatic laryngoscopy and prolonged endotracheal intubation. Furthermore, recent studies have demonstrated that the rate of dental development, and dental eruption may be affected by preterm birth. Children with the lowest birthweight and shortest gestational ages have the lowest rates of dental development, particularly before six years of age. The results of these clinical studies may have significant implications in the dental management of preterm children.

Bone and Bones↗

PubMed1996

Dental health of aboriginal pre-school children in Brisbane, Australia.

This investigation studied the dental health status of a group of 184 Australian Aboriginal children with a mean age of 4.4 +/- 0.8 years, who were attending pre-schools in metropolitan Brisbane, a non-fluoridated state capital city. The DDE (Developmental Defects of Enamel) Index was used to chart enamel hypoplasia and enamel opacities. WHO criteria was used to diagnose dental caries. The results showed that 98% of children had at least one tooth showing developmental enamel defects. Each child had a mean of 3.8 +/- 1.7 teeth affected by enamel hypoplasia and another 1.1 +/- 0.8 teeth affected by enamel opacity. Seventy-eight percent of the children had dental caries. The mean number of decayed, missing, filled teeth (dmft) per child was 3.8 +/- 3.7. The decayed component constituted 3.5 (95%) of the mean dmft, indicating a high unmet restorative need in this group. The mean dmfs (decayed, missing, filled, surfaces) was 5.9 +/- 7.3. Maxillary anterior labial decay of at least one tooth affected 43 (23%) of the children. In this sub-group, the dmft and dmfs was 9.1 +/- 2.8 and 15.4 +/- 7.7 respectively. Oral debris was found in 98% of the children. It is hypothesized that the high levels of underlying developmental enamel defects, compounded by low fluoride exposure, poor oral hygiene and a diet high in refined sugars pose an important caries risk factor in this group of children.

Child, Preschool↗

PubMed1995

Enamel hypoplasia, bilateral cataracts, and aqueductal stenosis: a new syndrome?

We report on a 12-year-old girl who presented with generalized enamel hypoplasia, cataracts, and enlargement of the cerebral ventricles secondary to aqueductal stenosis. Previously described syndromes of enamel defects with or without cataracts were excluded on the basis of clinical criteria and appearance of the dentition. Metabolic conditions which could have caused cataracts were excluded clinically and by biochemical tests. The combination of signs in this patient may represent a new syndrome.

Abnormalities, Multiple↗