Genotypic diversity of Streptococcus mutans in 3- to 4-year-old Chinese nursery children suggests horizontal transmission

OBJECTIVE: The aims of this study were to investigate the colonisation of Streptococcus mutans and to determine the possibility of horizontal transmission in Chinese nursery children. DESIGN: Fifty-six children aged between 3 and 4 years old from a nursery were included in this study. Twenty-four children were from the day and night nursery class, the others were from the day nursery class. Dental plaque samples were collected with sterile toothpicks and cultured on S. mutans-selective tryptone-yeast-cystine agar supplemented with 0.2U/ml bacitracin and 15% sucrose. The typical isolates of S. mutans were identified by classical microbiological methods and genotyped by arbitrarily primed PCR (AP-PCR) and restriction fragment length polymorphism analysis. RESULTS: S. mutans was isolated from 41 of the 56 children. The prevalence of S. mutans was higher in the children from day nursery class, compared with the children from day and night nursery class (P<0.05). A total of 140 S. mutans isolates from 41 children were analysed by AP-PCR, and 88 different amplitypes were identified. Of 41 children with S. mutans isolates, 82.9% carried two or more genotypes. Two genotypes of S. mutans were repeatedly isolated among 13 children in the day and night nursery class, and one genotype was isolated from two children in the day nursery class. CONCLUSION: The presence of matching genotypes of S. mutans among children attending the same nursery suggests the possibility of horizontal transmission.     

Clinical evaluation of a flowable resin composite and flowable compomer for preventive resin restorations

This clinical study evaluated the retention and caries protection of a flowable resin composite (Flow Line) and a flowable compomer (Dyract Flow) used in preventive resin restorations as compared to the conventional preventive resin technique which uses a resin composite (Brilliant) and a sealant (Concise). This study observed 205 permanent molars with small carious cavities less than 1.5 mm in width, which were obtained from 165 children aged 7 to 15 years. Flowable resin composite was used to treat 75 teeth, and 71 teeth were treated with flowable compomer in both cavities and caries-free fissures. For the control group, 59 teeth were treated with resin composite in cavities and sealant in caries-free fissures. The teeth were evaluated at 3, 6, 12, 18 and 24-month intervals. After three months, all 205 treated teeth were completely intact. After six months, 66 of the 71 teeth treated with flowable resin composite and 65 of the 70 teeth treated with flowable compomer were complete, compared to 57 of the 58 teeth treated with the conventional preventive resin technique. After 12 months, 60 of the 67 teeth treated with flowable resin composite and 61 of the 67 teeth treated with flowable compomer were complete, compared to 51 of the 55 teeth treated with the conventional preventive resin technique. After 18 months, 53 of the 61 teeth treated with flowable resin composite and 54 of the 62 teeth treated with flowable compomer were complete, compared to 47 of the 53 teeth treated with the conventional preventive resin technique. After 24 months, 49 of the 58 teeth treated with flowable resin composite and 45 of the 57 teeth treated with flowable compomer were complete, compared to 42 of the 52 teeth treated with the conventional preventive resin technique. There were no statistically significant differences in retention rates among all groups after 3, 6, 12, 18 or 24-months (p>0.05). One tooth treated with flowable resin composite and one tooth treated with flowable compomer developed caries after 18 and 24 months, respectively, resulting from partial loss at "caries-free fissures." Five teeth developed caries in the conventional preventive resin group; one after 12 months, two after 18 months and one after 24 months, due to loss at cavities. The final caries occurred after 24 months, resulting from partial loss at "caries-free fissures." The differences in caries development among the three groups were not statistically significant (p>0.05). This study suggested that flowable resin composite and flowable compomer could be used for preventive resin restorations. Meanwhile, a vigilant recall should be followed-up due to the risk of failure for flowable materials in "caries-free" fissures. The repair should be performed immediately, in case the preventive resin restoration develops a fracture or loss.     

健康成人刺激性全唾液流速及一氧化氮含量的增龄性变化

目的:研究不同年龄阶段健康成人的刺激性全唾液流速及唾液一氧化氮含量的变化。方法:将97例健康成人分成4个年龄组,分别为青龄组(20~39岁)、中龄组(40~59岁)、老龄组(60~79岁)、长寿组(80岁以上)。在上午8:00~10:00空腹,以2.5ml/L洗必太漱口,以20ml/L柠檬酸刺激舌背前1/3,以双蒸水漱口后采集全唾液5min,记录样本容量,并计算其流速。用硝酸还原酶法检测唾液中NO浓度,并计算其唾液中NO的单位时间含量。结果:(1)青龄组刺激性全唾液流速高于中龄组、老龄组、长寿组(P<0.05);中龄组、老龄组、长寿组之间唾液流速无显著性差异(P>0.05);(2)不同年龄组间两两比较,刺激性全唾液NO浓度无显著性差异(P>0.05);青龄组NO单位时间含量显著高于中龄组、老龄组和长寿组(P<0.05),中龄组、老龄组、长寿组之间的NO单位时间含量无显著性差异(P>0.05)。结论:(1)中老年人群的刺激性全唾液流速显著低于青年人群;(2)随年龄增长,健康成人刺激性全唾液中的NO浓度未发生明显变化,但其单位时间含量呈降低趋势。     

螺旋CT分析颧颊翼种植体义颌颧区种植方向和部位

目的为上颌骨大型缺损后行颧颊翼种植体义颌修复时,颧区种植的植入部位及方向提供客观依据。方法通过50例有牙列的单侧正常颧骨的螺旋CT影像三维重建,在矢状位截面影像上测量颧骨的前后倾斜角度;在冠状位截面影像上观察颧骨的形态并测量上颌牙槽嵴最颊侧点到上颌窦最外侧点的水平距离。结果颧骨的前后倾斜角度平均为80.03°,即颧骨前倾9.97°;48例颧骨冠状位影像形态较直,2例明显弯曲;上颌牙槽嵴最颊侧点到上颌窦最外侧点的水平距离为6.77mm。结论一般情况下,种植体前倾10°左右植入能最充分地利用颧骨的上部骨量。但由于个体差异,建议修复前先行螺旋CT影像学检查,评估颧骨的形态和骨量,以提高种植的安全性和有效性。     

Dendritic-NK cell interactions in P. gingivalis-specific responses

Patients with localized aggressive periodontitis have type-1 cytokines in gingival crevicular fluid and high titers of IFN-gamma-dependent IgG2 reactive with P. gingivalis in gingival crevicular fluid and serum. Localized aggressive periodontitis monocytes spontaneously differentiate into dendritic cells that can stimulate IFN-gamma production by NK cells. These relationships prompted the hypothesis that P. gingivalis-dendritic cell-NK cell interactions might promote type-1 cytokine responses. Although P. gingivalis is not a potent inducer of Th1 responses, it stimulated strong IL-12 responses by monocyte-derived dendritic cells in the presence of IFN-gamma, and IFN-gamma was produced by NK cells within 24 hrs in the presence of dendritic cells. Anti-P. gingivalis IgG2 responses were enhanced by dendritic cells, and removal of NK cells reduced IFN-gamma- and P. gingivalis-specific IgG2. Thus, P. gingivalis-dendritic cell-NK cell interactions apparently resulted in reciprocal stimulation and increased type-1 cytokine production by both dendritic cells and NK cells, and increased P. gingivalis-specific IgG2.