Caries arresting effect of silver diamine fluoride on dentine carious lesion with S. mutans and L. acidophilus dual-species cariogenic biofilm

Objectives: This in vitro study investigated the effects of silver diamine fluoride (SDF) on dentine carious lesion with cariogenic biofilm. Study Design: Thirty human dentine blocks were inoculated with Streptococcus mutans and Lactobacillus acidophilus dual-species biofilm to create carious lesion. They were equally divided into test and control group to receive topical application of SDF and water. After incubation anaerobically using micro-well plate at 37oC for 7 days, the biofilms were evaluated for kinetics, morphology and viability by colony forming units (CFU), scanning electron microscopy (SEM), and confocal microscopy (CLSM), respectively. The carious lesion underwent crystal characteristics analysis, evaluation of the changes in chemical structure and density of collagen fibrils using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and immune-labeling. Results: The log CFU of S. mutans and L. acidophilus in the test group was significantly lower than control group. SEM and CLSM showed confluent biofilm in control group, but not in test group. XRD showed the loss of crystallinity of dentine due to the dissolution of hydroxyapatite crystal structure in test group was less than control group. FTIR showed that log [Amide I: HPO4 2-] for test vs. control group was 0.31±0.10 vs. 0.57±0.13 (p<0.05). The goldlabeling density in test vs. control group was 8.54±2.44/ìm2 vs. 12.91±4.24/ìm2 (p=0.04). Conclusions: SDF had antimicrobial activity against the cariogenic biofilms and reduced demineralization of dentine

A bilingual advantage in 54-month-olds’ use of referential cues in fast mapping

Research has demonstrated a bilingual advantage in how young children use referential cues such as eye gaze and pointing gesture to locate an object or to categorize objects. This study investigated the use of referential cues (i.e., eye gaze) in fast mapping in three groups of children that differed in their language exposure. One hundred and seven 54-month-old children who were English monolinguals (n=29), English-Mandarin bilinguals (n=48), and English-Mandarin bilinguals with exposure to a third language (i.e., trilinguals, n=31) were assessed with a wordlearning task using two types of tests – a referent test and a mutual exclusivity test. During the task, following the gaze of an adult speaker was needed to be able to indicate the correct referent of a novel word at test. All three groups of children demonstrated successful word learning in explicit selection of and implicit looking time toward the target object during testing. However, bilingual and trilingual children outperformed their monolingual peers in both types of tests when they were asked to explicitly select the correct objects. These findings suggest positive effects of bilingualism on children’s use of referential cues in fast mapping