Biomedical subjects

W K Seow

Publications and source records attributed to W K Seow.

At least 109 records · Page 6Linked to original sources

PubMedDate not supplied

Sensitivity in vitro of Giardia intestinalis to dyadic combinations of azithromycin, doxycycline, mefloquine, tinidazole and furazolidone.

The new macrolide antibiotic, azithromycin, produced significant growth inhibition of Giardia intestinalis at 100 micrograms/ml, but adherence inhibition was significant at concentrations as low as 1 microgram/ml for the two strains used in these experiments. The dyadic combinations of azithromycin-furazolidone, doxycycline-mefloquine, doxycycline-tinidazole and mefloquine-tinidazole were synergistic for inhibition of adherence. These results suggest that these dyadic combinations may be worthy of consideration for chemotherapy of recalcitrant giardiasis.

Animals↗

PubMedDate not supplied

Inhibition of adherence of Giardia intestinalis by human neutrophils and monocytes.

Human neutrophils and monocytes were found to be capable of interfering with the in vitro adherence of Giardia intestinalis. Significantly greater inhibition of adherence was shown by stimulated phagocytic cells than by unstimulated cells. Both azurophil and specific granules extracted from the cytoplasm of neutrophils were equally potent in their adherence inhibitory activity. Dose-dependent effects on adherence were observed with granular enzymes and reactive oxygen species. Lower concentrations of reactive oxygen species were required for adherence inhibition that for growth inhibition. These results suggest that the adherence mechanism of G. intestinalis may be a feasible target for immunological attack by phagocytic cells.

Animals↗

PubMedDate not supplied

Effect of human milk and infant milk formulae on adherence of Giardia intestinalis.

Human milk was shown to inhibit adherence of Giardia at concentrations as low as 0.5%. Unsaturated fatty acids were also found to cause significant inhibitory effects on adherence, with ED50 values less than 1 microM for arachidonic, linoleic and palmitic acids. A variety of infant feeding formulae derived from cow's milk and soy bean had suppressive effects on adherence. These observations may explain in part the low prevalence of giardiasis in young infants.

Animals↗

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1-Methyl-3-phenyl-1,2,4-triazinium-5-olate: a new zwitterion with cytotoxic activity against human cancer cell-lines.

One of 6 newly synthesized triazinium zwitterions (JR-1--JR-6) was shown to induce 51Cr-release from leukemic (HL60 and CEM) and solid tumor (MM170 and HeLa) cell-lines. Leukemic cells were more sensitive to this compound than solid tumors as demonstrated by dose-response and time-course studies. Other experiments showed that JR-6 (1-methyl-3-phenyl-1,2,4-triazinium-5-olate) significantly suppressed protein, RNA and DNA synthesis at tumoricidal concentrations.

Antineoplastic Agents↗

PubMedDate not supplied

The prevalence of pre-eruptive dentin radiolucencies in the permanent dentition.

PURPOSE: Although intracoronal radiolucencies in radiographs of unerupted teeth have been reported for several decades, the prevalence of this condition remains unknown. This study determined the prevalence and associated dental conditions of permanent teeth showing pre-eruptive dentin radiolucencies in bite-wing radiographs of school children attending two school dental therapy training centers. METHODS: There were 1959 subjects (934 males and 1025 females), each providing a set of bite-wing radiographs which showed the crowns of unerupted permanent teeth. The mean age of the children at radiographic exposure was 7.8 +/- 1.79 years of age. RESULTS: 126 (6%) of subjects had radiolucencies in the crowns of pre-eruptive permanent teeth. Of the 9919 teeth viewed on the radiographs, 163 (2%) were affected. There were no significant racial and gender differences in the prevalence of the defects. Of the 126 subjects with dentin radiolucencies, 93 (74%) had only 1 affected tooth compared with 31 (25%) who had two teeth affected, and 2 (2%) who had 3 affected teeth. CONCLUSIONS: Within each tooth type, the highest tooth prevalence was found in the mandibular first molar (4%), followed by the mandibular first premolar (2%), the mandibular second molar (1%), mandibular second premolar (1%), maxillary first molar (1%), maxillary first premolar (1%), and maxillary second premolar (0.2%). In addition, the group with dentin radiolucencies had a high prevalence of ectopically-positioned teeth of 14% compared with only 2% in the group without the defect, suggesting that ectopic position may predispose a tooth to pre-eruptive radiolucent defects. Other common developmental and acquired dental conditions were also examined, but no significant differences were noted between groups with and without the pre-eruptive dentin radiolucencies.

Adolescent↗

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Prevalence of caries in urban Australian aborigines aged 1-3.5 years.

PURPOSE: This study investigated the prevalence and etiological factors associated with caries in a group of young Australian aboriginal children from 1 to 3.5 years of age. METHODS: One hundred and forty-seven healthy infants, aged from 1 to 3.5 years, attending a community health center in Brisbane, a nonfluoridated state capital city, were randomly selected for the study. RESULTS: The caries prevalence was 39% by subjects and 32% by the total number of teeth present. The mean number of decayed, filled teeth (dtf) was 2.5 +/- 0.4, which is more than twice the figure for 3-year-old children in Australia. Furthermore, the filled (f) component represented only 1% of the total dft, suggesting very low treatment levels. Increased caries experience of the infants was strongly associated with high dental plaque scores, high levels of Streptococcus mutans infection, and sleep-time consumption of milk containing added sugar. CONCLUSION: The results suggest that urban Australian aboriginal infants are at high risk for caries, and that preventive strategies are urgently required.

Chi-Square Distribution↗

PubMedDate not supplied

Prevalence of pre-eruptive intracoronal dentin defects from panoramic radiographs.

PURPOSE: This investigation stemmed from preliminary clinical observations from a school dental clinic, which suggested that a proportion of clinically undetected, radiolucent lesions on radiographs may originate as pre-eruptive intracoronal dentin defects. This study investigated the prevalence of such defects in orthopantomograms from a group of children and young adults. METHODS: A total of 1281 orthopantomograms with 11,767 unerupted permanent teeth were examined. RESULTS: The prevalence of intracoronal dentin defects was 3% by subjects, and 0.5% by teeth; the highest prevalence being noted in the maxillary and mandibular first permanent molars. Most of the lesions occurred singly, and nearly half had extended to greater than two-thirds the width of dentin thickness. Ectopic positioning was significantly associated with this lesion. CONCLUSIONS: Pre-eruptive intracoronal dentin defects occur at a significant prevalence rate. Increased awareness of this entity may improve diagnosis and allow early treatment.

Chi-Square Distribution↗

PubMedDate not supplied

Pre-eruptive intracoronal resorption as an entity of occult caries.

"Occult" or "hidden" caries refers to occlusal caries which is not diagnosed clinically because the occlusal surface appears ostensibly intact, and radiographs show radiolucencies in dentin. The prevalence of occult caries has been reported to range from 2.2% to over 50% of permanent molars. In spite of its relatively high prevalence, the etiology and pathogenesis of occult caries remain unclear. The author hypothesizes that occult lesions could have resulted from processes which are pre-eruptive or post-eruptive. Pre-eruptive processes include intracoronal resorption of unerupted teeth, and the post-eruptive process is occlusal fissure caries. Although the prevalence of intracoronal resorption has been shown to be around 3-6% by subject and 0.5-2% by teeth, the percentage contribution of this process to the overall prevalence of occult caries is unclear. When affected teeth are fully erupted, it is difficult to determine if pre-eruptive resorption had been present previously. The prevalence of occult lesions does not appear to be affected by fluoride exposure. Radiographs are useful adjuncts to aid in the diagnosis of occult lesions. Bitewing radiographs are useful for detecting early occlusal fissure caries while panorex radiographs of unerupted developing teeth aid in the diagnosis of pre-eruptive intracoronal lesions. It is suggested that all unerupted, developing teeth on radiographs be examined for pre-eruptive resorptive lesions.

Adolescent↗

PubMedDate not supplied

Dental erosion in children: a literature review.

Epidemiological studies have shown that the prevalence of dental erosion in children varies widely between 2 and 57%. Changes seen in dental erosion range from removal of surface characteristics to extensive loss of tooth tissue with pulp exposure and abscess formation. Symptoms of dental erosion range from sensitivity to severe pain associated with pulp exposure. The etiology of dental erosion is dependent on the presence of extrinsic or intrinsic acid in the oral environment. Extrinsic sources of acids in children include frequent consumption of acidic foods and drinks, and acidic medications. Regurgitation of gastric contents into the mouth, as occurs in gastroesophageal reflux, is the most common source of intrinsic acid in children. A multitude of factors may modify the erosion process, such as saliva, oral hygiene practices, and presence or absence of fluoride. When dental erosion is diagnosed, it is important to investigate and identify the acid source, and to determine if the process is ongoing. The aim of treatment is to eliminate the cause of acid exposure, and to minimize the effects of acid exposure where it is not possible to remove the acid source. Restoration of the dentition involves stainless steel crowns to restore lost vertical dimension, and composite resin for esthetics.

Acids↗

PubMedDate not supplied

The sensitivity and specificity of clinical assessment compared with bitewing radiography for detection of occlusal dentin caries.

PURPOSE: This prospective, cross-sectional study examined the sensitivity and specificity of clinical assessment compared to bitewing radiographs in the detection of occlusal dentin caries in permanent molars. METHODS: Subjects were 481 children aged 5-12 years from a school-based dental clinic. Occlusal surfaces of 1929, sealed and unsealed first and second permanent molars were examined clinically and scored using specific criteria. Teeth with any type of restorations or proximal caries, including preventive resin restorations, were excluded from the study. Bitewing radiographs were exposed within 4 weeks of clinical examination and were assessed for dentin radiolucencies beneath the occlusal surface. The results of the clinical examinations were correlated with those of bitewing radiographs. Information provided by the parents on history forms, including systemic fluoride exposure, was also noted. RESULTS: Of the 1833 teeth scored as clinically sound in the study, only 72 (4%) demonstrated a dentin radiolucency on bitewings, and 1761 (96%) were scored as sound. The sensitivity of the clinical examination was determined to be 0.96. In the teeth clinically scored as showing dentin caries, only 56/96 (58%) were found to have dentin radiolucencies on the radiographs. The specificity of the technique was determined to be 0.58. A positive history of a medical condition, or fluoride exposure, in the forms of toothpaste use, or water fluoridation did not affect the examination results. CONCLUSIONS: Clinical examination of cleaned and dried, sealed, and unsealed teeth has a sensitivity of 0.96 and a specificity of 0.58 in the detection of dentin radiolucencies in bitewing radiographs. Dentin radiolucencies beneath clinically sound occlusal surfaces are not significantly associated with gender, medical conditions or fluoride.

Cariostatic Agents↗

PubMedDate not supplied

Oral health of children with congenital cardiac diseases: a controlled study.

Congenital cardiac disease (CCD) is one of the most common developmental anomalies in children. Affected children require special care in dentistry because of their susceptibility to infective endocarditis from oral infections, yet little information is available on the oral health of children with CCD. The present study, which investigated 39 children with CCD and 33 healthy control siblings, showed that CCD children generally suffered poorer oral health. In patients with primary dentitions, 52% of CCD children had enamel hypoplasia, compared with only 23% in the control group. In addition, CCD children had significantly more teeth with untreated dental decay (mean dmft 4.2 vs. 2.3), and more endodontically treated teeth. Children with CCD also had less than optimal professional and home dental care. Only 31% had professional advice regarding increased preventive dental health behavior, and only 15% used fluoride supplements, although the children resided in a nonfluoridated area. Furthermore, significantly fewer CCD children had parental help with tooth brushing compared to control children. This study shows that children with CCD should be targeted for vigorous preventive dental care.

Adolescent↗

PubMedDate not supplied

The effect of medical therapy on dentin formation in vitamin D-resistant rickets.

Vitamin D-resistant rickets (VDRR) is one of the most common forms of rickets in developed countries today. Widely practiced medical treatment regimens usually include replacing phosphorus and calcium lost through urination. In this study, 20 teeth from five patients with varying grades of dental manifestation of VDRR were examined to relate the institution of medical therapy with any observed improvement of dentin calcification. In all the teeth examined, there was no correlation between the time of appearance of dentin changes and the commencement of medical therapy. Furthermore, in several teeth from the patients with Grade III severity, there were no signs of improvement in dentin calcification even after prolonged medical therapy. This study suggests that current medical treatment of VDRR has no beneficial effect on the dental structures and dentists should not rely on medical treatment to correct dental calcification problems.

Calcitriol↗

PubMedDate not supplied

Scanning electron microscopic analysis of dentin in vitamin D-resistant rickets--assessment of mineralization and correlation with clinical findings.

In vitamin D-resistant rickets, the basic dental defect is manifested in dentin. Structural investigations of rachitic dentin by light and scanning electron microscopy have revealed the presence of calcospherites separated by interglobular dentin. This occurs when calcospherites do not fuse. This study investigated the morphology and ultrastructure of rachitic dentin with three different clinical and histologic grades of severity to determine if dentin mineralization can be quantified by calcospherite size and degree of calcospherite fusion. The results showed that a correlation existed between calcospherite size, calcospherite fusion, and the degree of dentin mineralization. The present findings indicate that calcospherite size and calcospherite fusion are valid parameters for assessing and quantifying dentin mineralization. In addition, an SEM grading of severity was established based on these two parameters. The SEM grades correlated directly with the clinical and histologic grades, suggesting that the dental clinical manifestations are a reflection of the underlying morphology of the dentin and the extent of abnormal dentin mineralization.

Dentin↗

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Enamel hypoplasia in the primary dentition: a review.

Clinical significance of enamel hypoplasia includes poor esthetics, tooth sensitivity, malocclusion and predisposition to dental caries. It may provide diagnostic clues as to genetic influences and systemic diseases, as well as to any trauma during the span of dental development. These systemic factors include birth trauma, infections, nutritional disorders, metabolic diseases, and exposures to chemicals such as tetracycline, lead, and fluoride. Inherited types form a relatively small component overall, including genetic abnormalities of enamel formation, or dental features of many inherited diseases or dysmorphic syndromes. Developmental enamel defects range in prevalence from 4 percent to 60 percent, depending on the criteria and the population studied. It is likely that many of these individual factors may in fact act through a central mechanism: mineral deficiency.

Dental Enamel Hypoplasia↗

PubMedDate not supplied

Oral changes associated with end-stage liver disease and liver transplantation: implications for dental management.

In children, chronic liver disease has a variety of causes; its effects include malnutrition, bleeding tendencies, osteopenia, and rachitic changes in the skeleton. Chronic liver disease in children may have many oral manifestations, such as green staining of the teeth and gingiva, as well as enamel hypoplasia. Dental management may be complicated by many factors, like bleeding tendencies and inability to metabolize routine anesthetics. Patients who undergo increasingly successful liver transplantation require life-long immunosuppressive therapy, which has side-effects. Results of this study of nine patients, seven females and two males, show that the effects of end-stage liver disease are permanently recorded on the teeth. Six were examined both before and after liver transplantation; the other three, only afterwards. This study confirms and extends the findings of three previous reports describing the oral manifestations of congenital biliary atresia in childhood.

Biliary Atresia↗

PubMedDate not supplied

Comparison of ultrasonic and mechanical cleaning of primary root canals using a novel radiometric method.

Although ultrasound is employed increasingly as an adjunct to biomechanical preparation in clinical endodontics for adult teeth, there have been no previous investigation of this technique for primary teeth. This investigation studied the efficacy of ultrasonication compared with mechanical cleaning in primary root canals using a novel radiometric method. The results indicated that in multiple-rooted teeth, ultrasonication with an endosonic file for 3 min was able to remove 81.1% of inoculated bacteria, compared with only 65.2% using conventional filing. A combination of mechanical filing followed by ultrasonication produced the best results, with greater than 95% bacteria removed. The results show that ultrasonication may be useful for primary teeth endodontics.

Dental Pulp Cavity↗

PubMedDate not supplied

Dilaceration of a primary maxillary incisor associated with neonatal laryngoscopy.

Neonatal laryngoscopy and endotracheal intubation often are required for prematurely born, low birthweight children. Previous studies have shown that these procedures are associated with a high prevalence of enamel hypoplasia of the maxillary anterior teeth. The present case report, which describes dilaceration of a left maxillary primary central incisor probably resulting from laryngoscopy, strongly supports the hypothesis that irreversible trauma to the dentition may result from endotracheal intubation.

Dental Enamel Hypoplasia↗

PubMedDate not supplied

The effects of dyadic combinations of endodontic medicaments on microbial growth inhibition.

In recent years dyadic combinations of endodontic medicaments have been used increasingly in clinical pediatric dentistry with little regard to the possibility of pharmacological antagonism of the components. In this investigation, a microbial growth inhibition assay was used to determine changes in antimicrobial activity in dyadic mixtures of endodontic medicaments. The combinations assayed were Ledermix (corticosteroid-antibiotic) and Calyxl (calcium hydroxide), Ledermix and Kri (iodoform), Kri and Calyxl, and formocresol and eugenol. All these compounds have antibacterial activity when used individually. In the dyadic combinations assayed, results showed that adding calcium hydroxide to another antibiotic preparation has deleterious effects on growth inhibition, and combining any two antimicrobial medicaments produces no additive or synergistic effects. It is concluded that it may be clinically advantageous to use endodontic medicaments in the dyadic combinations shown in this investigation.

Analysis of Variance↗