Effect of maternal use of chewing gums containing xylitol on transmission of mutans streptococci in children: a meta-analysis of randomized controlled trials.

BACKGROUND: Mutans streptococci (MS) are the major causative bacteria involved in human dental decay. Habitual consumption of xylitol has been proved to reduce MS levels in saliva and plaque. AIM: To evaluate the effect of the maternal use of xylitol gum on MS reduction in infants. DESIGN: A structured literature review and meta-analysis. A random effects model was used to assess the relative risks of the incidence of MS in the saliva or plaque of children who were 6, 9, 12, 18, and 24 months old. RESULTS: We reviewed 11 RCTs derived from 5 research teams that included 601 mothers. Our results indicated that the incidence of MS in the saliva or plaque of the infants was significantly reduced in the xylitol group (risk ratio: 0.54; 95% confidence interval: 0.39-0.73, at 12-18 months) and (risk ratio: 0.56; 95% confidence interval: 0.40-0.79, at 36 months) compared with the control groups. The long-term effect of maternal xylitol gum exposure on their children's dental caries was controversial. CONCLUSION: Habitual xylitol consumption by mothers with high MS levels was associated with a significant reduction in the mother-child transmission of salivary MS.

Characterizing the conservation effect of clear coatings on photodegradation of wood.

Photodiscoloration of clear-coated wood may be caused by the yellowing of both clear coating film and underlying wood, or either of them. Wood specimens covered with two types of free polyurethane films with/without light stabilizer were used to simulate the photodiscoloration of clear-coated wood. Percent UV transmission of aromatic polyurethane (PU) films decreased after irradiation, whereas aliphatic polyurethane (PUA) films significantly increased with irradiation time resulting in further photoyellowing of wood beneath the PUA film. A light reflection model was used to elucidate discoloration caused separately by the clear coating film and the underlying wood. After 24 days of light irradiation, clear coating and the underlying wood contributed respectively, 40.70% and 59.30% discoloration of PU-coated specimens, and the corresponding values for PUA-coated specimens were 5.15% and 94.85%. PU film with light stabilizer reduced lignin degradation and generation of carbonyl derivatives in the underlying wood.

Modification of wood with isopropyl glycidyl ether and its effects on decay resistance and light stability.

China fir (Cunninghamia lanceolata var. lanceolata) and maple (Acer sp.) wood were etherified with isopropyl glycidyl ether and the decay resistance and light stability of the modified wood were assessed. CP/MAS (13)C NMR and FT-IR analyses indicated that new ether bonds containing isopropyl groups formed after reacting wood with isopropyl glycidyl ether. Modified wood samples were very resistant to decay when exposed to brown-rot fungus Laetiporus sulphureus or white-rot fungus Lenzites betulina for 60 days in the soil-block test. The isopropyl glycidyl ether treatment of wood was effective in decreasing formation of phenoxyl radicals upon UV irradiation and thus protecting wood from photodiscoloration.