Introduction: Early childhood caries (ECC) is common among Hong Kong preschool children. It is a disease caused by dental plaque bacteria and may be controlled by good toothbrushing habits. However, preschool children are often too young to perform effective tothbrushing, and therefore parental toothbrushing is recommended for them. The oral hygiene status of Hong Kong preschool children is usually not good and parental toothbrushing is not common. Fluoride varnish is effective in preventing dental caries in school children and adolescents but its effectiveness in preventing dental caries in preschool children is still inconclusive. Objective: To investigate the effectiveness of hands-on training in parental toothbrushing, with or without semi-annual applications of a 5% sodium fluoride varnish in preventing ECC. Methods: Children aged 8-23 months were recruited and randomly allocated to one of three groups: Group 1 - positive control, a brief oral health education to parents; Group 2 - oral health education to parents, hands-on training in parental toothbrushing, and home visits every six months to reinforce parental toothbrushing; Group 3 - application of a 5% sodium fluoride varnish onto the child’s teeth during home visits in addition to the intervention provided to Group 2. Clinical examination of the children and a questionnaire survey of the parents were conducted at baseline. Interventions for the children and parents were delivered according to their group assignment. Evaluation of the main outcome, development of new dental caries, was conducted after 24 months through clinical examination. Information on children’s oral health-related behaviors and parents’ knowledge of and attitude towards their child’s oral health was collected using a questionnaire at the 24-month follow-up. Results: Out of the 450 children recruited at baseline, 415 (92%) children were examined after 24 months and all examined children’s parents completed the questionnaire. Including both noncavitated and cavitated carious lesions, the incidences of ECC in Gp1 to Gp3 were 11.9%, 11.8%, and 17.5%, respectively (p > 0.05) and; the mean dmfs scores in Gp1 to Gp3 were 0.3, 0.2, and 0.4, respectively (p > 0.05). Proportions of parents who practiced parental toothbrushing twice a day were 62.7%, 60.4%, and 65.7% in Gp1, Gp2, and Gp3, respectively (p > 0.05). Results from a logistic regression analysis showed that children who were older, who had poorer oral hygiene, who had high frequency of sugary snack intake, who had visited a dentist during the study, and whose parents had lower education level would have a higher chance to develop new dental caries during the 24-month study period. Conclusion: Hands-on training in parental toothbrushing, reinforced by face-to-face interview every 6 months, with or without a semi-annual application of 5% sodium fluoride varnish, may not have any additional effect on preventing development of dental caries in young children compared to the standard oral health education provided to parents in Hong Kong. The child’s socio-demographic background, oral hygiene status, and frequency of sugary snack intake are related to ECC. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Dentistry / Master / Master of Dental Surgery

Early childhood caries (ECC) is the most prevalent oral disease of children worldwide. Epidemiological studies reported that most of the ECC are left untreated. While young children may not be co-operative enough for conventional restorative treatments, silver diamine fluoride (SDF) can be topically applied on tooth surfaces as a cariostatic agent. Previous clinical trials have confirmed that annual application of 38% SDF is effective in arresting dentin caries in preschool children. However, information about the effectiveness of SDF with different combinations of concentration and frequency is still lacking. This information is important for the optimal application of SDF in the future public health programs for caries control. This prospective randomized controlled trial aimed to investigate and compare the effectiveness of 12% and 38% SDF when applied annually or biannually in arresting dentin caries of primary teeth of preschool children for 30 months. The two null hypotheses tested were firstly, there is no difference in effectiveness when SDF is applied at 12% or 38% in arresting dentin caries of preschool children; and secondly, there is no difference in effectiveness when SDF is applied annually or biannually in arresting dentin caries of preschool children. A total of 888 healthy and cooperative K1 children aged 3-4 years with at least one dentin caries surface were recruited and randomized into four treatment groups: Group 1 received annual applications of 12% SDF, Group 2 received biannual applications of 12% SDF, Group 3 received annual applications of 38% SDF, and Group 4 received biannual applications of 38% SDF. Group 3 was assigned as the positive control group. Primary outcome was soft dentin caries surface at baseline that became arrested at the follow-up examinations. Clinical examinations were conducted at the kindergartens every 6 months by the same trained examiner. Parental questionnaires were used to collect the children’s demographic information, oral hygiene related habits, parental satisfaction with children’s dental appearance and dental health at baseline, 18- and 30-month examinations. Adverse effects after treatments including increment of non-vital teeth, complaint about tooth or gingival discomfort, gingival discoloration, and black staining over arrested surfaces were also recorded. A total of 798 children with 3,268 caries surfaces were examined at 30-month follow-up. The dropout rates of the four groups were similar. The respective proportions of arrested surfaces in Group 1 to Group 4 were 48.7%, 54.0%, 60.6%, and 66.9%, respectively (p < 0.001). The two null hypotheses were rejected. Both concentration and frequency were significantly related to treatment effectiveness, but no significant interaction between these two factors was found. The effect size of concentration was much greater than frequency. Other than a higher proportion of black staining in groups receiving 38% SDF treatments, there were no significant differences in adverse effects among the children in the four treatment groups. To conclude, SDF is more effective in arresting dentin caries in primary teeth of preschool children at 38% than 12%, and when applied biannually than annually. Clinical significant improvement in effectiveness can be achieved by increasing its concentration. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

OBJECTIVES: The primary objective of this study was to evaluate the efficacy of fluoride varnish in caries prevention and arrest on coronal and root surfaces of teeth over a 24-month period in Chinese Sjögren’s syndrome (SS) patients. Secondary objective was to investigate the effect of fluoride varnish on oral microorganism (Candida and lactobacilli). METHODS: This study was a randomized, double-blind, placebo-controlled clinical trial. A total of 85 SS patients participated in this study. They were randomly assigned to two groups to receive either fluoride varnish or placebo gel quarterly. Dental examination, and assessment of the sicca symptoms, oral hygiene, salivary flow / pH / buffering capacity and oral microbiological profiles were carried out at the baseline, 12-month and 24-month visits. RESULTS: Seventy-eight patients (92%) completed the 24-month trial. At the 24-month visit, no statistically significant differences (Mann-Whitney test, P > 0.05) were found between the fluoride and the placebo groups regarding their mean numbers of coronal surfaces with new enamel caries lesions (fluoride: 1.6; placebo: 1.6), arrested caries lesions (fluoride: 0.6; placebo: 0.7), and also root surface caries lesions (fluoride: 0.3; placebo: 0.1). SS patients who had received application of fluoride varnish were significantly less likely to develop dentin caries in coronal surfaces over the 24-month study period (P = 0.035). The mean numbers of coronal surfaces with new dentin caries lesions found at the 24-month visit in the fluoride and placebo groups were 1.4 and 2.7, respectively (Mann-Whitney test, P > 0.05). The caries prevented fraction of fluoride varnish for coronal dentin caries was 33.3%. No significant differences in the mean counts of Candida and lactobacilli between fluoride and placebo groups were detected (Mann-Whitney test, P > 0.05). Results of the logistic regression analysis showed that SS patients who had high baseline DMFS scores (P = 0.050), harbored more species of Candida in the dental plaque samples (P = 0.019), or had low pH of unstimulated whole saliva (P = 0.005) were significantly more likely to develop dentin caries in coronal surfaces over the 24-month study period. CONCLUSIONS: Fluoride varnish may be efficacious in preventing coronal dentin caries in Chinese patients with SS. However, it may not be efficacious in preventing root caries and has no effect on oral microorganism. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Dentistry / Doctoral / Doctor of Philosophy

Two factorial experiments were conducted to determine if high dietary fluoride would inhibit selenite toxicity in rats. In each study, two levels of selenite (0.05 and 5 mg/kg diet) were matched against two levels of fluoride (1 and 150 mg/kg diet) for either 6 or 8 weeks. Fluoride failed to prevent the depressive effect of selenite on food intake and body weight gain in either study. Although liver selenium concentration was slightly (15%) but significantly (P < 0.005) reduced when the highest fluoride and selenium level were combined in the first study, this effect could not be repeated. These three measures therefore failed to provide evidence for a fluoride and selenium interaction. Fluoride, however, prevented hepatic necrosis seen in most of the selenite-toxic rats. Hepatic lesions seen histologically in selenite-toxic rats were not observed for either kidney or heart. With regard to a possible mechanism for the fluoride effect upon selenite liver pathology, fluoride partially (26%) but significantly (P < 0.025) reduced thiobarbituricreactive substances (an indicator of peroxidative cell membrane damage) in selenite-toxic rats, but there was no fluoride effect on an enzyme system (liver xanthine oxidase) that potentially could generate an initiator of lipid peroxidation. In agreement with results of others, fluoride deposition into bone was inconsistently affected by selenite, Overall, the protective effect of fluoride on selenite toxicity appears to be confined to liver pathology. The exact mechanism for this effect, however, remains unclear. / Graduation date: 1992

Indiana University-Purdue University Indianapolis (IUPUI) / Hypothesis: The interaction between the abrasive level and fluoride concentration of dentifrice slurries modulates the surface loss (SL) and remineralization of incipient enamel caries (IEC). Methods: Three types of IEC were created and six experimental slurries with different combinations of fluoride content and abrasive level were tested. In experiment 1, the three IEC were subjected to brushing (with experimental slurries) and remineralization cycles for 5 days. Fluoride concentrations (0 and 275 ppm as NaF) and abrasive levels (Low and High) were tested. SL was determined by optical profilometry at baseline and after 1, 3, and 5 days. In experiment 2, changes in IEC mineral content (Δ(ΔZ)C) and depth (ΔLC) were investigated at baseline and after the 5-day cycling with transverse microradiography. In experiments 3 and 4, SL of MeC and CMC lesions were further studied, respectively; testing not only fluoride concentration (275 and 1250 ppm as NaF) and abrasivity (low and high) of the slurry, but also the brushing frequency (1x, 2x, and 3x/day). Brushing-remineralization cycles were performed for 7 days. Statistical analyses were performed at 5% significance level. Results: Experiment 1: overall, brushing with the high-abrasive slurry caused more SL than with the low-abrasive. For CMC and MeC lesions, 0 ppm F had more SL than 275 ppm F only after day 3. Fluoride had no effect on the SL of HEC lesions. Experiment 2: fluoride and abrasives did not have a significant effect on IEC. HEC had significantly lower Δ(ΔZ)C than CMC and MeC, with CMC and MeC not differing from each other. Lesion type had no effect on ΔLC. Experiment 3: brushing CMC lesions 3x/day with 1250 ppm F increased SL compared to 1x/day, after 5 and 7 days. Study 4: brushing MeC lesions with high abrasive slurry containing 1250 ppm F increased SL after 5 and 7 days. Conclusions: The IEC tested showed different SL and remineralization behaviors. The fluoride content and abrasive level of the toothpaste showed to be relevant modulating the SL of enamel caries lesions as well as their remineralization behavior.