纳米羟磷灰石/聚酰胺66作为盖髓材料的体外抗菌作用

目的研究新型纳米羟磷灰石/聚酰胺66（nHA- PA66）对龋性牙本质中常见致病菌的体外抗菌作用。方法采用变形链球菌、粘性放线菌和干酪乳杆菌的标准株,通过琼脂扩散法比较nHA- PA66固化膜片、nHA- PA66糊剂、nHA- PA66碘仿糊剂、羟磷灰石糊剂及氢氧化钙糊剂对3种实验菌的抑菌环直径大小。结果nHA- PA66固化膜片与nHA- PA66糊剂对变形链球菌无抗菌作用,对粘性放线菌和干酪乳杆菌有极轻微抗菌作用,nHA- PA66固化膜片与nHA- PA66糊剂之间抑菌环直径差异无统计学意义（P>0.05）;nHA- PA66碘仿糊剂的抗菌能力增强,但与氢氧化钙糊剂相比,二者间差异无统计学意义（P>0.05）;羟磷灰石糊剂对3种实验菌均无抗菌作用。结论nHA- PA66作为一种新型纳米生物材料,单独使用时对变形链球菌、粘性放线菌和干酪乳杆菌几乎不具有抗菌性能,但可通过与碘仿的联合应用来提高nHA- PA66用作盖髓材料时的抗菌能力。     

Microbial caries induction in the roots of human teeth in vitro

Streptococcus mutans GS5, Lactobacillus casei DSM20011 and Actinomyces viscosus T14 produce artificial caries in the roots of extracted teeth. Roots were coated with wax leaving an 8 mm2 window exposed on the buccal surfaces, and then incubated for 8 days in the presence of the test organism, the synthetic medium being changed each day. Samples were then examined by SEM, or microradiographs were obtained from 120 microns sections. The pH at the root surface at the end of the induction averaged 4.43, 5.00 and 5.20, and the lesion depths measured on the microradiographs averaged 121, 83 and 34 microns, for Strep. mutans, L. casei and A. viscosus respectively. This relationship between pH and lesion depth confirms earlier findings. As all of these organisms can produce lesions in tooth structure, elimination of one type would probably not eliminate caries.     

Humoral IgG antibodies to oral microbiota in a population at risk for root-surface caries.

Mutans streptococci have been strongly implicated in the initiation of dental caries on coronal surfaces. Their role in development of root-surface caries is less clear. The etiologic agents of both types of dental caries are likely to elicit systemic immune responses. The objective of the present study, therefore, was to study the association of clinical variables of disease with humoral IgG antibodies to nine oral micro-organisms in 314 adult subjects, aged 45-65 years, who were at risk for root-surface caries. Antibody activity to Streptococcus mutans strain Ingbritt, S. mutans/S. sobrinus GTFs, S. faecalis strain 19433, Actinomyces viscosus strain WVU 626, Actinomyces naeslundii strain 12, Lactobacillus casei, Actinobacillus actinomycetemcomitans strain Y4, Porphyromonas gingivalis strain 381, Eikenella corrodens strain 1073, and Wolinella recta strain 371 was measured by ELISA. Pearson correlation coefficients among log10 antibody levels within subjects revealed marked positive correlations among subgingival bacteria, generally weak positive correlations among supragingival micro-organisms, and no correlations between elements of the supragingival battery with the subgingival battery. IgG antibody levels to mutans streptococcal antigens were significantly correlated with subject DMF scores (r = 0.23; p less than 0.0001). No significant correlation was seen between DMF scores and antibody to any other supragingival micro-organism tested. Further relationships between levels of S. mutans antibody and individual clinical variables were analyzed by step-wise multiple linear regression, resulting in a model that was highly significant (p = 0.0001), with an r2 = 0.14. Numbers of missing teeth, coronal caries, root-surface caries, and root-surface restorations were each positively associated with antibody levels to mutans streptococci.(ABSTRACT TRUNCATED AT 250 WORDS)     

根周细菌对胶原包被羟磷灰石粘附的体外实验研究

目的：细菌对牙面的粘附能力与其致龋性密切相关，本研究旨在比较对牙面具有粘附能力的变形链球菌ATCC25175、粘性放线菌ATCC15987、乳杆菌ATCC4546、牙龋卟啉菌ATCC33277及中间普氏菌ATCC25611对胶原包被羟磷灰石实验膜（C－HA）的粘附能力，探讨口腔细菌在根周疾病中的作用。方法：采用同位素闪烁计数法测定上述五种细菌对胶原处理的羟基磷灰石（C－HA）的粘附能力，以[^3H]胸腺嘧啶核苷为标记对细菌的粘附进行定量观察，用每分钟的同位素放射量CPM表示（counts per mintue）。结果：所有细菌对C－HA表面的粘附率均有统计学意义（P＜0．01），粘性放线菌对C－HA表面的粘附率显著高于其它细菌组，牙龋卟啉菌及乳杆菌对C－HA表面的粘附率次之，变形链球菌及中间普氏菌对C－HA表面的粘附能力最弱。结论：不同的根周细菌对胶原包被的羟磷灰石的选择性粘附作用不同，粘性放线菌、乳杆菌及牙龋卟啉菌对胶原具较强的亲和作用，在细菌的局部定植过程及疾病的进展中发挥重要作用。     

The ability of selected oral microorganisms to emit red fluorescence

Some novel caries detection and excavation devices rely on the ability of bacteria to produce red fluorescing compounds. The aim of this study was to examine the ability of selected oral microorganisms to emit red fluorescence. Streptococcus mutans, S. oralis, S. salivarius, S. sobrinus, Lactobacillus fermentans, L. casei, L. rhamnosus, Actinomyces naeslundi, A. israelii, Prevotella intermedia, and Fusobacterium nucleatum were inoculated onto Columbia agar with haemin and vitamin K and incubated anaerobically for up to 7 days in the dark. The resulting bacterial colonies were excited using filtered xenon light (405 +/- 20 nm) and digitally photographed through a 530-nm high-pass filter. The red and green portions of the colony fluorescence were analyzed using a computer program and the red/green ratio was calculated. All colonies emitted both red and green fluorescence. The green outweighed the red portion for the following species (in descending order) S. oralis, S. salivarius, S. mutans, F. nucleatum and S. sobrinus. The red portion was higher for the following species (in descending order) P. intermedia, A. naeslundi, A. israelii, L. fermentans, L. rhamnosus and L. casei. With all the bacteria examined, one color portion generally outweighed the other, giving the visual impression of either red or green fluorescence. We conclude that red fluorescence is well suited to detection of the bacteria which cause dentin caries but it is not suitable as an indicator of the presence and activity of the streptococci involved in initial caries.     

Caries on root surfaces exposed following gingivectomy in conventional rats infected with Streptococcus sobrinus and Actinomyces viscosus

To study the ability of bacteria associated with coronal caries to initiate root surface caries, a rat model was used. Root surfaces were exposed by gingivectomy in rats fed a caries-promoting diet and orally inoculated with either Actinomyces viscosus M-100, Streptococcus sobrinus (mutans) 6715, or both. A fourth group received a diet containing antibiotics. The animals were sacrificed 64 days following the gingivectomy performed on the right molar quadrants. Gingivectomy significantly increased exposed lingual root length and root caries incidence. There were no caries on non-gingivectomy root surfaces. Root surface caries incidence in the groups inoculated with A. viscosus and A. viscosus plus S. sobrinus did not differ. For both these groups, root caries incidence was significantly greater than that for the group inoculated with S. sobrinus alone. Root caries incidence in this latter group did not differ from that in the control group.     

Growth and acid tolerance of human dental plaque bacteria

Pure cultures of representative strains of cariogenic and non-cariogenic plaque bacteria were assessed for their ability to initiate and maintain growth in broths, adjusted to initial pH levels of 7.0, 5.5 or 5.0, and to produce lactic acid from sucrose or glucose in resting-cell suspensions at pH 6.5, 5.0, 4.5 and 4.0. Streptococcus mutans, Lactobacillus casei and Streptococcus faecalis showed greater acid tolerance than strains of Streptococcus sanguis, Streptococcus salivarius, Streptococcus mitis and Actinomyces viscosus. For all species, growth initiation in broth was more acid sensitive than lactic-acid production in resting-cell suspensions. These data confirm and extend previous observations that the species of plaque bacteria most closely associated with the initiation or progression of dental caries are more aciduric than non-cariogenic species.     

Human T-cell responses to oral streptococci in human PBMC-NOD/SCID mice

We investigated cellular and humoral immune responses to oral biofilm bacteria, including Streptococcus mutans, Streptococcus anginosus, Streptococcus sobrinus, and Streptococcus sanguinis, in NOD/SCID mice immunized with human peripheral blood mononuclear cells (hu-PBMC-NOD/SCID mice) to explore the pathogenicity of each of those organisms in dental and oral inflammatory diseases. hu-PBMC-NOD/SCID mice were immunized by intraperitoneal injections with the whole cells of the streptococci once a week for 3 weeks. FACS analyses were used to determine the percentages of various hu-T cell types, as well as intracellular cytokine production of interleukin-4 and interferon-gamma. Serum IgG and IgM antibody levels in response to the streptococci were also determined by enzyme-linked immunosorbent assay. S. anginosus induced a significant amount of the proinflammatory cytokine interferon-gamma in CD4(+) and CD8(+) T cells in comparison with the other streptococci. However, there was no significant differences between the streptococci in interleukin-4 production by CD4(+) and CD8(+) T cells after inoculation. Further, S. mutans significantly induced human anti-S. mutans IgG, IgG(1), IgG(2), and IgM antibodies in comparison with the other organisms. In conclusion, S. anginosus up-regulated Th1 and Tc1 cells, and S. mutans led to increasing levels of their antibodies, which was associated with the induction of Th2 cells. These results may contribute to a better understanding of human lymphocyte interactions to biofilm bacteria, along with their impact on dental and mucosal inflammatory diseases, as well as endocarditis.     

乳牙深龋时冠部牙髓的病理变化和细菌分布

目的 从临床和实验研究两方面探讨深龋乳牙冠髓病理学状况及导致冠髓病变的原因。方法 随机选择Ｈｅ面深龋乳磨牙４５颗,行活髓切断术,光镜下观察其冠髓病理改变;用需氧、厌氧培养技术研究其髓腔内细胞;用扫描电镜观察窝洞底部牙本质小管中细菌的种类和分布特征。结果 ７７．８％的冠髓有不同程度的慢性炎症或慢性牙髓炎急性发作;９４．９％的髓腔中有需、厌氧菌混合感染;洞底牙本质小管中有球菌和杆菌侵入,球菌均位于小管     

Effects of extracts of miswak and derum on proliferation of Balb/C 3T3 fibroblasts and viability of cariogenic bacteria

Abstract:  Objectives:  This study examined the effects of extracts of two chewing sticks on proliferation of fibroblasts and viability of cariogenic bacteria. Methods:  Aqueous extracts of miswak ( Salvadora persica ; Arak tree) and derum ( Juglans regia ; walnut tree) were prepared and their effects investigated on growth of Balb/C 3T3 mouse fibroblasts by measuring the mitochondrial succinic dehydrogenase activity. Furthermore, the effects on the viability of various cariogenic bacteria ( Streptococcus mutans , Streptococcus salivarius , Lactobacillus casei and Actinomyces viscosus) was also determined. Results:  The data revealed that Balb/C 3T3 fibroblasts exposed to aqueous extracts of miswak or derum showed an increase in cell proliferation by 156% and 255%, respectively, in comparison with controls (p<0.0001). Furthermore, extracts from both miswak and derum had adverse effects on the growth of the cariogenic microorganisms, with derum having significantly greater antimicrobial effects than miswak and at much lower concentrations against all the bacteria tested. The most sensitive organisms were A. viscosus , followed by S. mutans , S. salivarius , with L. casei being the most resistant. Conclusion:  The results show that aqueous extracts of miswak and derum enhance the growth of fibroblasts and inhibit the growth of cariogenic bacteria, with the derum extract showing greater activity than miswak.     

口腔常见致病菌的表面疏水性分析

目的：分析测试几种口腔常见致病菌的细胞表面疏水性，为研究细菌非特异性黏附机制提供科学理论参数。方法：采用碳氢化合物黏着法测试细菌表面疏水性。结果：不同种类的细菌、同种细菌的不同菌株间疏水性均存在差异。每株细菌表面具有其相对稳定的参考值范围。结论：口腔细菌具有强弱不同的疏水作用。     

人工合成抗菌肽对口腔细菌抗菌性能的初步研究

目的 评价人工合成抗菌肽（十肽）对口腔常见感染性疾病主要致病菌的抑菌活性。方法 采用琼脂扩散法及液体稀释法体外评价十肽对变异链球菌、表兄链球菌、嗜酸乳杆菌、血链球菌、格氏链球菌、黏性放线菌、内氏放线菌、牙龈卟啉单胞菌、中间普雷沃菌、具核梭杆菌、伴放线嗜血杆菌及白色假丝酵母菌的抑菌性能,并测定十肽对变异链球菌的时间-杀菌曲线。结果 十肽对所选实验菌株均表现出不同的抑菌性能,对主要致龋菌的最小抑菌浓度MIC值为62.5~125 μg·mL^-1,而对主要牙周致病菌的MIC值为250~1 000 μg·mL^-1,其中,十肽对龋病主要致病菌变异链球菌有较强抑菌作用。时间-杀菌曲线结果显示,十肽作用20 min后开始杀菌,30 min之后可完全杀灭细菌,且在24 h之内无细菌生长。结论 新型人工合成抗菌肽十肽对口腔常见感染性疾病主要致病菌具有抑菌性能,其中对致龋变异链球菌的抑菌效果最为明显。     

Distribution of three cariogenic bacteria in secondary carious lesions around amalgam restorations.

Secondary dental caries remains an unresolved problem in dentistry and little is known of its microbial etiology. The purpose of this study was to compare the distribution of the three most suspected cariogenic groups of bacteria, mutans streptococci. Actinomyces naeslundii genospecies 2 and lactobacilli, in natural secondary caries around amalgam restorations. Extracted teeth with secondary caries were sectioned to obtain three samples that were randomly distributed to three different groups. Each group was immunolabeled with antibodies to either Streptococcus mutans, A. naeslundii genospecies 2 or Lactobacillus casei and subsequently labeled with secondary fluorescent antibodies. All samples were analyzed three-dimensionally using confocal microscopy. The results indicated that the three different bacteria were widely present and could have an important role in the development of secondary caries around amalgam restorations.     

Zoocin A and lauricidin in combination reduce Streptococcus mutans growth in a multispecies biofilm

Dental caries is the most prevalent human infection. It is a multifactorial disease in which the microbial composition of dental plaque plays a major role in the development of clinical symptoms. The bacteria most often implicated in the development of caries are that group of streptococci referred to as the mutans streptococci, in particular Streptococcus mutans and Streptococcus sobrinus. One approach to the prevention of caries is to reduce the numbers of mutans streptococci in plaque to a level insufficient to support demineralization of the tooth. In this study, zoocin A, a peptidoglycan hydrolase, combined with lauricidin, a cell membrane active lipid, was shown over a 72 h period to selectively suppress the growth of S. mutans in a triple species biofilm. Growth of the non-target species Streptococcus oralis and Actinomyces viscosus was not inhibited. In treated systems the amount of extracellular polysaccharide matrix produced was much reduced as determined by use of fluorescein isothiocyanate conjugated wheat germ agglutinin. The pH of treated biofilms remained above neutral as opposed to a value of 4.3 in untreated controls. We conclude that use of antimicrobial compounds that specifically target cariogenic bacteria should be further explored.     

The association of selected bacteria with the lesions of root surface caries

Plaque from the root surfaces of 165 subjects (mean age 65.5 years, 22-26 teeth/subject) was analysed for specific bacteria. Five subject groups were defined: A (DMFS 16.4), B (DMFS 55.9), C1 (DMFS 55.6), C2 (DMFS 57.0) and C3 (DMFS 48.1). Groups C1 and C2 had unrestored root surface lesions; Group A, B and C3 were free of unrestored root caries and differed in their coronal caries experience. Streptococcus mutans was isolated more frequently from the root lesions in Groups C1 and C2 than from intact root surfaces in Group A. Streptococcus oralis, Streptococcus mitis 1 and Streptococcus sanguis were isolated more frequently from Group A. The percentage contribution that S. mutans made to plaque from lesions in Groups C1 and C2 was higher than that from plaque in Group A and Actinomyces viscosus serovar 2 contributed more to plaque in Group C1 than in samples from Group A. The percentage counts of Lactobacillus in plaque from lesions in Groups C1 and C2 were higher than those from intact roots in Groups A, B, and C3. Subjects were also grouped on the presence of Lactobacillus and S. mutans in plaque samples. Samples with both organisms (n = 17) showed significantly higher isolation frequencies of specific strains of S. mitis 1 and also A. viscosus serovar 2 compared with samples of plaque containing S. mutans or Lactobacillus. Actinomyces naeslundii serovar 1 was not isolated from samples containing both S. mutans and Lactobacillus. The results confirm an association of S. mutans and Lactobacillus with root surface lesions and suggest a relationship between lesions and A. viscosus serovar 2.     

Effect of monoclonal antibodies against lipoteichoic acid from the oral bacterium Streptococcus mutans on its adhesion and plaque-accumulation in vitro

Five monoclonal antibodies directed against Streptococcus mutans strain JBP lipoteichoic acid (LTA) were characterized. They were all similarly reactive with the immunizing LTA-containing extract, with intact Strep. mutans JBP cells and with LTA purified from Lactobacillus casei. Immobilized anti-LTA antibodies removes LTA from LTA-containing extracts. The binding of antibodies to LTA was inhibited by the aqueous extract but not by the organic extract of de-acylated LTA, indicating reactivity with the polyglycerol-phosphate portion of the molecule. Antibodies were reactive with all serotypes of Strep. mutans, as well as with strains of Streptococcus salivarius, Streptococcus sanguis and L. casei, but not with LTA-negative species Streptococcus mitis or Actinomyces viscosus. Anti-LTA antibodies at doses of 0.3 or 3.0 micrograms/ml, had no effect on the adherence of Strep. mutans JBP to experimental salivary pellicles formed on hydroxyapatite, but enhanced adherence 150-300 per cent at 30 micrograms/ml. There was no effect of anti-LTA antibodies in a chemostat model which measured sucrose-dependent plaque accumulation by Strep. mutans. The results argue against a major role for LTA in Strep. mutans adherence or plaque accumulation in vitro.     

An optimal host response to a bacterium may require the interaction of leukocytes and resident host cells

Bacterial infection results in inflammatory responses that may lead to soft-tissue damage and bone resorption. However, the mechanisms by which different bacteria contribute to lesions of endodontic origin are not fully understood. This study examined the response to Streptococcus mutans and Porphyromonas endodontalis in two cell types that are involved in periapical pathology, mononuclear and osteoblastic cells. This was accomplished by measuring the induction of chemokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-2) and proinflammatory cytokines (interleukin-1beta, tumor necrosis factor-alpha, interleukin-6, interferon-gamma). The results demonstrated that S. mutans more efficiently stimulate inflammatory cytokine production by mononuclear cells, whereas P. endodontalis is relatively more potent in activating osteoblastic cells. Moreover, optimal activation of osteoblastic cells by S. mutans requires soluble mediators produced by mononuclear cells, whereas P. endodontalis does not. These results suggest that the association of different bacteria with specific pathologic processes may be partially explained by their capacities to activate specific host cells.     

Degradation of starch and its hydrolytic products by oral bacteria

Selected strains of oral bacteria were analyzed for their ability to degrade wheat starch, maltose, maltotriose, and maltoheptaose. S. sanguis IUOM-11M and JC804, S. mutans 6715, S. salivarius IUOM-8, A. viscosus IUOM-62, and A. naeslundii ATCC 12104 degraded all four substrates. S. mutans NCTC 10449 degraded starch, maltose, and maltotriose, while A. viscosus ATCC 15987 degraded starch and maltose, and S. sanguis SS34 degraded only maltose. L. casei IUOM-14 did not degrade any of the substrates. Analysis of starch degradation products from S. sanguis IUOM-11M and A. viscosus IUOM-62 demonstrated oligosaccharides, maltose, and trace amounts of glucose for the former and oligosaccharides, maltotriose, and maltose for the latter. S. sanguis IUOM-11M alpha-glucosidase (EC 3.2.1.20) demonstrated a pH optimum of 6.5 and greatly enhanced activity from maltose-cultured cells as compared with cells cultured in glucose or fructose. The presence of fructose in the growth medium prevented this enhancement of activity by maltose. Maltose inhibited sucrose-dependent synthesis of S. sanguis IUOM-11M insoluble polysaccharide and both primer-dependent and primer-independent synthesis of soluble polysaccharide. Maltoheptaose inhibited primer-dependent but not primer-independent soluble polysaccharide synthesis. Several oral bacteria have the ability to hydrolyze starch and to degrade further the products to acidogenic substrates. These products may also inhibit sucrose-dependent synthesis of polysaccharides, which enhances the production of the acidogenic substrate fructose. The results add further support to the growing body of evidence suggesting that caries-promoting properties of starch may be expressed only when starch is present in diets containing sucrose.     

Effect of sustained-release chlorhexidine varnish on Streptococcus mutans and Actinomyces viscosus in orthodontic patients.

This study evaluated the effect of sustained-release chlorhexidine varnish on orthodontic patients. Ten children, ages 10 to 16 years, participated. Bacterial levels of Streptococcus mutans and Actinomyces viscosus and total counts were evaluated in sputum samples. These counts were evaluated at 4 stages: before orthodontic treatment, at least 2 weeks after bonding of the brackets, 1 week after application of chlorhexidine varnish, and 3 weeks after application of chlorhexidine varnish. Increases in bacterial levels of S mutans and in the total bacterial count were detected after the brackets were bonded. One week after the sustained-release chlorhexidine varnish was applied, a significant decrease of total bacterial levels and S mutans was observed. This decrease persisted for 3 weeks after the first application. No significant change in A viscosus levels occurred during that period. The results provide additional evidence that sustained-release chlorhexidine varnish decreases S mutans levels in orthodontic patients with fixed appliances and therefore might be useful in preventing caries lesions.     

Antibacterial effects of three experimental quaternary ammonium salt (QAS) monomers on bacteria associated with oral infections

The aim of this study was to test the antibacterial effects of three experimental quaternary ammonium salt monomers in order to evaluate their potential applications as dental materials. In vitro susceptibility testing of the monomers was performed by the broth dilution method on bacteria associated with oral infections: Streptococcus mutans ATCC 25175, Actinomyces viscosus ATCC 15987, Staphylococcus aureus ATCC 29213 and Lactobacillus casei ATCC 393. The time-kill kinetics of the monomer with relatively higher antibacterial activity against S. mutans were also investigated. It was found that all the tested bacteria strains were susceptible to the three monomers, among which methacryloxylethyl cetyl ammonium chloride (DMAE-CB) exhibited the lowest minimal inhibitory concentrations, ranging from 1.2 to 4.8 microg/ml. The time-kill curve showed that DMAE-CB achieved 99.44% killing at 19.2 microg/ml (4 times the minimal bactericidal concentration) against S. mutans after 1 min and 100% killing within 10 min of contact. This result indicates that the quaternary ammonium salt monomer DMAE-CB may be a candidate antibacterial agent for incorporation into dental restorative materials.