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Concept: Dental plaque

168

BACKGROUND: Dental caries among young children are a global problem. Scant attention is paid towards primary teeth, leading to high prevalence of dental caries. There are only few studies done in Sri Lanka, addressing oral hygiene among preschool children. Scientific evidence is in need to persuade authorities to establish a programme promoting oral hygiene among preschool children. METHODS: A descriptive cross sectional study was conducted in Ragama Medical officer of Health area. Consecutive children between 2 – 5 years of age, attending child welfare clinics were recruited for the study. Practices related to dental hygiene and socio-economic characteristics were obtained using an interviewer administered questionnaire. Mouth was examined for evidence of dental caries. Data collection and examination were done by two doctors who were trained for this purpose. The data were analysed using SSPS version 16. RESULTS: Total of 410 children were included. None had a routine visits to a dentist. Practices related to tooth brushing were satisfactory. Prevalence of dental caries gradually increased with age to reach 68.8% by 5 years. Mean total decayed-extracted-filled (deft) score for the whole sample was 1.41 and Significant caries index (SIC) was 4.09. Decayed tooth were the main contributor for the deft score and Care index was only 1.55. Girls had a significantly higher prevalence of caries than boys. CONCLUSIONS: Dental care provided for Sri Lankan preschool children appears to be unsatisfactory as prevalence of dental caries among this cohort of preschool children was very high. There is an urgent need to improve dental care facilities for Sri Lankan preschool children.

Concepts: Teeth, Dental caries, Sri Lanka, Dental plaque, Oral hygiene, Dental floss, Halitosis, Toothbrush

162

Protein drugs (PD) are minimally utilized in dental medicine due to high cost and invasive surgical delivery. There is limited clinical advancement in disrupting virulent oral biofilms, despite their high prevalence in causing dental caries. Poor efficacy of antimicrobials following topical treatments or to penetrate and disrupt formed biofilms is a major challenge. We report an exciting low-cost approach using plant-made antimicrobial peptides (PMAMPs) retrocyclin or protegrin with complex secondary structures (cyclic/hairpin) for topical use to control biofilms. The PMAMPs rapidly killed the pathogen Streptococcus mutans and impaired biofilm formation following a single topical application of tooth-mimetic surface. Furthermore, we developed a synergistic approach using PMAMPs combined with matrix-degrading enzymes to facilitate their access into biofilms and kill the embedded bacteria. In addition, we identified a novel role for PMAMPs in delivering drugs to periodontal and gingival cells, 13-48 folds more efficiently than any other tested cell penetrating peptides. Therefore, PDs fused with protegrin expressed in plant cells could potentially play a dual role in delivering therapeutic proteins to gum tissues while killing pathogenic bacteria when delivered as topical oral formulations or in chewing gums. Recent FDA approval of plant-produced PDs augurs well for clinical advancement of this novel concept.

Concepts: Protein, Bacteria, Microbiology, Biofilm, Dental caries, Dental plaque, Oral hygiene, Streptococcus mutans

108

Recent genomic data have revealed multiple interactions between Neanderthals and modern humans, but there is currently little genetic evidence regarding Neanderthal behaviour, diet, or disease. Here we describe the shotgun-sequencing of ancient DNA from five specimens of Neanderthal calcified dental plaque (calculus) and the characterization of regional differences in Neanderthal ecology. At Spy cave, Belgium, Neanderthal diet was heavily meat based and included woolly rhinoceros and wild sheep (mouflon), characteristic of a steppe environment. In contrast, no meat was detected in the diet of Neanderthals from El Sidrón cave, Spain, and dietary components of mushrooms, pine nuts, and moss reflected forest gathering. Differences in diet were also linked to an overall shift in the oral bacterial community (microbiota) and suggested that meat consumption contributed to substantial variation within Neanderthal microbiota. Evidence for self-medication was detected in an El Sidrón Neanderthal with a dental abscess and a chronic gastrointestinal pathogen (Enterocytozoon bieneusi). Metagenomic data from this individual also contained a nearly complete genome of the archaeal commensal Methanobrevibacter oralis (10.2× depth of coverage)-the oldest draft microbial genome generated to date, at around 48,000 years old. DNA preserved within dental calculus represents a notable source of information about the behaviour and health of ancient hominin specimens, as well as a unique system that is useful for the study of long-term microbial evolution.

Concepts: DNA, Genetics, Archaea, Human, Bacteria, Genome, Dental plaque, Neanderthal

58

Our ability of screening broad communities for clinically asymptomatic diseases critically drives population health. Sensory chewing gums are presented targeting the tongue as 24/7 detector allowing diagnosis by “anyone, anywhere, anytime”. The chewing gum contains peptide sensors consisting of a protease cleavable linker in between a bitter substance and a microparticle. Matrix metalloproteinases in the oral cavity, as upregulated in peri-implant disease, specifically target the protease cleavable linker while chewing the gum, thereby generating bitterness for detection by the tongue. The peptide sensors prove significant success in discriminating saliva collected from patients with peri-implant disease versus clinically asymptomatic volunteers. Superior outcome is demonstrated over commercially available protease-based tests in saliva. “Anyone, anywhere, anytime” diagnostics are within reach for oral inflammation. Expanding this platform technology to other diseases in the future features this diagnostic as a massive screening tool potentially maximizing impact on population health.Early detection of gum inflammation caused by dental implants helps prevent tissue damage. Here, the authors present a peptide sensor that generates a bitter taste when cleaved by proteases present in peri-implant disease, embed it in a chewing gum, and compare the probe to existing sensors using patient saliva.

Concepts: Enzyme, Medical terms, Diagnosis, Taste, Dental plaque, Metalloproteinase, Sensor, Oral hygiene

40

Accessing information on plant consumption before the adoption of agriculture is challenging. However, there is growing evidence for use of locally available wild plants from an increasing number of pre-agrarian sites, suggesting broad ecological knowledge. The extraction of chemical compounds and microfossils from dental calculus removed from ancient teeth offers an entirely new perspective on dietary reconstruction, as it provides empirical results on material that is already in the mouth. Here we present a suite of results from the multi-period Central Sudanese site of Al Khiday. We demonstrate the ingestion in both pre-agricultural and agricultural periods of Cyperus rotundus tubers. This plant is a good source of carbohydrates and has many useful medicinal and aromatic qualities, though today it is considered to be the world’s most costly weed. Its ability to inhibit Streptococcus mutans may have contributed to the unexpectedly low level of caries found in the agricultural population. Other evidence extracted from the dental calculus includes smoke inhalation, dry (roasting) and wet (heating in water) cooking, a second plant possibly from the Triticaceae tribe and plant fibres suggestive of raw material preparation through chewing.

Concepts: Food, Starch, Chemical compound, Dental caries, Dental plaque, Cyperus rotundus, Dentistry, Streptococcus mutans

36

Candida albicans is frequently detected with heavy infection by Streptococcus mutans in plaque-biofilms from children with early-childhood caries (ECC). This cross-kingdom biofilm contains an extensive matrix of extracellular α-glucans that is produced by an exoenzyme (GtfB) secreted by S. mutans. Here, we report that mannans located on the outer surface of C. albicans cell-wall mediates GtfB binding, enhancing glucan-matrix production and modulating bacterial-fungal association within biofilms formed in vivo. Using single-molecule atomic force microscopy, we determined that GtfB binds with remarkable affinity to mannans and to the C. albicans surface, forming a highly stable and strong bond (1-2 nN). However, GtfB binding properties to C. albicans was compromised in strains defective in O-mannan (pmt4ΔΔ) or N-mannan outer chain (och1ΔΔ). In particular, the binding strength of GtfB on och1ΔΔ strain was severely disrupted (>3-fold reduction vs. parental strain). In turn, the GtfB amount on the fungal surface was significantly reduced, and the ability of C. albicans mutant strains to develop mixed-species biofilms with S. mutans was impaired. This phenotype was independent of hyphae or established fungal-biofilm regulators (EFG1, BCR1). Notably, the mechanical stability of the defective biofilms was weakened, resulting in near complete biomass removal by shear forces. In addition, these in vitro findings were confirmed in vivo using a rodent biofilm model. Specifically, we observed that C. albicans och1ΔΔ was unable to form cross-kingdom biofilms on the tooth surface of rats co-infected with S. mutans. Likewise, co-infection with S. mutans defective in GtfB was also incapable of forming mixed-species biofilms. Taken together, the data support a mechanism whereby S. mutans-secreted GtfB binds to the mannan layer of C. albicans to promote extracellular matrix formation and their co-existence within biofilms. Enhanced understanding of GtfB-Candida interactions may provide new perspectives for devising effective therapies to disrupt this cross-kingdom relationship associated with an important childhood oral disease.

Concepts: Microbiology, Fungus, Streptococcus, Yeast, In vivo, Candida albicans, Dental plaque, Streptococcus mutans

32

Dental biofilms (known as plaque) are notoriously difficult to remove or treat because the bacteria can be enmeshed in a protective extracellular matrix. It can also create highly acidic microenvironments that cause acid-dissolution of enamel-apatite on teeth, leading to the onset of dental caries. Current antimicrobial agents are incapable of disrupting the matrix and thereby fail to efficiently kill the microbes within plaque-biofilms. Here, we report a novel strategy to control plaque-biofilms using catalytic nanoparticles (CAT-NP) with peroxidase-like activity that trigger extracellular matrix degradation and cause bacterial death within acidic niches of caries-causing biofilm. CAT-NP containing biocompatible Fe3O4 were developed to catalyze H2O2 to generate free-radicals in situ that simultaneously degrade the biofilm matrix and rapidly kill the embedded bacteria with exceptional efficacy (>5-log reduction of cell-viability). Moreover, it displays an additional property of reducing apatite demineralization in acidic conditions. Using 1-min topical daily treatments akin to a clinical situation, we demonstrate that CAT-NP in combination with H2O2 effectively suppress the onset and severity of dental caries while sparing normal tissues in vivo. Our results reveal the potential to exploit nanocatalysts with enzyme-like activity as a potent alternative approach for treatment of a prevalent biofilm-associated oral disease.

Concepts: Archaea, Bacteria, Microbiology, Biofilm, Lactic acid, Dental caries, Dental plaque, Streptococcus mutans

29

Cavitation occurs around dental ultrasonic scalers, which are used clinically for removing dental biofilm and calculus. However it is not known if this contributes to the cleaning process. Characterisation of the cavitation around ultrasonic scalers will assist in assessing its contribution and in developing new clinical devices for removing biofilm with cavitation. The aim is to use high speed camera imaging to quantify cavitation patterns around an ultrasonic scaler. A Satelec ultrasonic scaler operating at 29 kHz with three different shaped tips has been studied at medium and high operating power using high speed imaging at 15,000, 90,000 and 250,000 frames per second. The tip displacement has been recorded using scanning laser vibrometry. Cavitation occurs at the free end of the tip and increases with power while the area and width of the cavitation cloud varies for different shaped tips. The cavitation starts at the antinodes, with little or no cavitation at the node. High speed image sequences combined with scanning laser vibrometry show individual microbubbles imploding and bubble clouds lifting and moving away from the ultrasonic scaler tip, with larger tip displacement causing more cavitation.

Concepts: Biofilm, Dental plaque, The Tip

28

OBJECTIVE: The aim of this study was to systematically review the current literature on the clinical effects of sugar-free chewing gum on plaque indices and parameters of gingival inflammation. MATERIAL AND METHODS: The MEDLINE-PubMed, Cochrane-CENTRAL and EMBASE databases were searched up to 20 April 2012 to identify any appropriate studies. Plaque indices and parameters of gingival inflammation were selected as outcome variables. RESULTS: An independent screening of the 594 unique titles and abstracts identified six non-brushing and four brushing studies that met the eligibility criteria. In the non-brushing studies, the use of chewing gum did not significantly affect the parameters of interest. In the descriptive analysis of the brushing studies, four of five comparisons showed a statistically significant effect in favour of the sugar-free chewing gum with respect to plaque scores. The meta-analysis for the Quigley & Hein (J Am Dent Assoc 1962; 65: 26) plaque index scores in the brushing studies also showed a significant difference (DiffM -0.24, 95% CI [-0.41; -0.08]). For bleeding tendency, the descriptive analysis showed that one of the two comparisons identified a significant difference in favour of chewing gum. The meta-analysis, however, did not substantiate this difference. CONCLUSION: Within the limitations of this systematic review, it may be concluded that the use of sugar-free chewing gum as an adjunct to toothbrushing provides a small but significant reduction in plaque scores. Chewing sugar-free gum showed no significant effect on gingivitis scores. In the absence of brushing, no effect on plaque and gingivitis scores could be established.

Concepts: Statistical significance, Effect size, Meta-analysis, Multiple comparisons, Dental plaque, Oral hygiene, Gingivitis, Chewing gum

27

Periodontal disease ranges from gingival inflammation (gingivitis) to the inflammation and loss of tooth-supporting tissues (periodontitis). The bacterial composition of supragingival plaque across a range of periodontal severities has not previously been explored with high-throughput sequencing. Furthermore, quantitative modelling of bacterial abundances in supragingival plaque as a function of both gingivitis and periodontitis has not previously been attempted.We assessed a cross-sectional cohort of 962 Malawian women for periodontal disease and used 16S rRNA gene amplicon sequencing (V5-V7 region) to characterise the bacterial composition of supragingival plaque samples. Associations between bacterial relative abundances and gingivitis/periodontitis were investigated by using negative binomial models, adjusting for epidemiological factors. We also examined bacterial co-occurrence networks to assess community structure.The main differences in supragingival plaque composition were associated more with gingivitis than periodontitis, including higher bacterial diversity and greater abundance of particular species. However, even after controlling for gingivitis, the presence of subgingival periodontitis was associated with an altered supragingival plaque. A small number of species were associated with periodontitis but not gingivitis, including members of Prevotella, Treponema, and Selemonas, supporting a more complex disease model than linear progression following on from gingivitis. Co-occurrence networks of periodontitis-associated taxa clustered according to periodontitis across all gingivitis severities. Species including Filifactor alocis and Fusobacterium nucleatum were central to this network, supporting their role in co-aggregation of periodontal biofilms during disease progression.Our findings confirm that periodontitis cannot be considered simply an advanced stage of gingivitis, even when only considering supragingival plaque.

Concepts: Ribosomal RNA, 16S ribosomal RNA, Periodontology, Gingiva, Periodontitis, Periodontal disease, Dental plaque, Gingivitis