Exposure of Streptococcus mutans and Streptococcus sanguinis to blue light in an oral biofilm model.

The potential anti-cariogenic effect of blue light was evaluated using an oral biofilm model. Two species, Streptococcus mutans and Streptococcus sanguinis, were cultivated ex vivo on bovine enamel blocks for 24 h, either separately or mixed together, then exposed to blue light (wavelengths 400-500 nm) using 112 J/cm2. Twenty four or 48 h after exposure to light the biofilm structure and biomass were characterized and quantified using SEM and qPCR, respectively. Bacterial viability was analyzed by CLSM using live/dead bacterial staining. Gene expression was examined by RT-qPCR. After exposure to light, S. mutans biomass in mono-species biofilm was increased mainly by dead bacteria, relative to control. However, the bacterial biomass of S. mutans when grown in mixed biofilm and of S. sanguinis in mono-species biofilm was reduced after light exposure, with no significant change in viability when compared to control. Furthermore, when grown separately, an upregulation of gene expression related to biofilm formation of S. mutans, and downregulation of similar genes of S. sanguinis, were measured 24 h after exposure to blue light. However, in mixed biofilm, a downregulation of those genes in both species was observed, although not significant in S. mutans. In conclusion, blue light seems to effectively alter the bacterial biomass by reducing the viability and virulence characteristics in both bacterial species and may promote the anti-cariogenic balance between them, when grown in a mixed biofilm. Therefore, exposure of oral biofilm to blue light has the potential to serve as a complementary approach in preventive dentistry.

High-resolution novel method for tracking bacteria in a multi-species biofilm.

The aim of this study is to establish a novel high resolution tracking ability of a specific bacterium in multispecies biofilm. A periodontal multispecies biofilm was constructed with Streptococcus sanguis, Actinomyces naeslundii, Porphyromonas gingivalis and Fusobacterium nucleatum. A single species was stained with fluorescein isothiocyanate (FITC). The mature biofilm was stained for viability (propidium iodide) and analysis was performed with flow cytometry. The sensitivity of the assay was compared with colony forming units (CFU) counts. A single cell suspension of P. gingivalis was grown in broth and biofilm to identify the location of these events on side scatter and forward scatter. The sensitivity of the assay was comparable to that of the CFU counts. The assay allows quantification of the ratio of a single bacterium within the biofilm, and its viable proportion. The described method is reproducible and of high resolution, and allows the examination of microbes' composition and viability within a biofilm structure.

Combined antioxidant effects of Neem extract, bacteria, red blood cells and Lysozyme: possible relation to periodontal disease.

BACKGROUND: The common usage of chewing sticks prepared from Neem tree (Azadirachta indica) in India suggests its potential efficacy in periodontal diseases. The objective of this study is to explore the antibacterial effects of Neem leaf extract on the periodontophatic bacteria Porphyromonas gingivalis and Fusobacterium nucleatum, and its antioxidant capacities alone and in combination with bacteria and polycationic peptides that may be at the site of inflammation. METHODS: Neem leaf extract was prepared by ethanol extraction. The growth kinetics of P. gingivalis and F. nucleatum under anaerobic conditions in the presence of Neem leaf extract were measured. Broth microdilution test was used to determine the Minimal Inhibitory Concentration (MIC) of Neem leaf extract against each bacterial strain. The effect of Neem leaf extract on the coaggregation of the bacteria was assessed by a visual semi-quantitative assay. The antioxidant capacities of Neem leaf extract alone and in combination with bacteria, with the addition of red blood cells or the polycationic peptides chlorhexidine and lisozyme, were determined using a chemiluminescence assay. RESULTS: Neem leaf extract showed prominent dose-dependent antibacterial activity against P. gingivalis, however, had no effect on the growth of F. nucleatum nor on the coaggregation of the two bacteria. Yet, it showed intense antioxidant activity, which was amplified following adherence to bacteria and with the addition of red blood cells or the polycationic peptides. CONCLUSIONS: Neem leaf extract, containing polyphenols that adhere to oral surfaces, have the potential to provide long-lasting antibacterial as well as synergic antioxidant activities when in complex with bacteria, red blood cells and lisozyme. Thus, it might be especially effective in periodontal diseases.

Sustained effects of blue light on Streptococcus mutans in regrown biofilm.

In prior studies, exposure of Streptococcus mutans in biofilm to blue light using high fluences of up to 680 J/cm(2) did not interfere with bacterial capability to reform an initial biofilm; however, a delayed antibacterial effect was observed. Our aim was to determine the sustained effecttts of blue light-emitting diode (LED) curing light on the pathogenicity of the newly formed biofilm. S. mutans were grown to form biofilm that was exposed to blue light (wavelengths, 460-480 nm) for 1, 3, and 7 min (equivalent to 37, 112, and 262 J/cm(2), respectively). Then, bacteria were suspended and allowed to regrow into new biofilms. The regrown biofilms were assessed for bacterial quantification by optical density (OD) measurement and quantitative polymerase chain reaction (qPCR), bacterial viability and extracellular polysaccharide production by fluorescent staining using confocal scanning laser microscopy, acid production by bacteria (acidogenicity), and bacterial survival at low pH (aciduricity) using qPCR. Bacterial growth in the regrown biofilms was increased when samples were previously exposed to light; however, under the confocal microscopy, a higher proportion of dead bacteria and a reduction in polysaccharide production were observed. The acidogenicity from the regrown biofilm was lowered as fluences of light increased. The aciduricity of the regrown biofilm was decreased, meaning less growth of bacteria into biofilm in low pH with increasing fluences. Blue light has sustained effects on S. mutans bacteria grown into new biofilm. Although bacterial growth in biofilm increased, bacterial viability and virulence characteristics were impaired. The cariogenic potential over time of S. mutans previously exposed to blue light when grown on tooth surfaces is yet to be determined.

Effects of CO2 laser irradiation on tooth enamel coated with biofilm.

BACKGROUND AND OBJECTIVES: CO2 laser irradiation of tooth enamel can inhibit demineralization of tooth enamel, by changing enamel composition and resistance to acid attack. The aim of this work was to examine these effects of CO2 laser irradiation on enamel covered by biofilm. MATERIALS AND METHODS: Streptococcus mutans was grown on bovine enamel surfaces for 48 hours to form a mature biofilm. Samples were irradiated by CO2 laser (wavelength of 10.6 µm) at a power of 0.08 W in a super-pulse mode for 1 second and 24 pulses/second, with an energy density of 0.77 J/cm(2) per pulse. Untreated controls and laser treated samples with and without biofilm were examined for the morphology of the biofilm and the enamel surface by scanning electron microscopy (SEM). Structural biofilm viability was assessed using confocal laser scanning microscopy with live/dead staining. The biofilm was removed in a sonication water bath and the non-treated and irradiated enamel samples were chemically analyzed using energy dispersive X-ray spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR). RESULTS: Irradiated samples showed a melt zone with micro-cracks in the center of the irradiating beam position, which was smaller when irradiated enamel was covered by biofilm. Confocal microscopy images demonstrated higher proportion of dead bacteria at the margins of the irradiated spot area, while at the spot center the bacteria were evaporated exposing the enamel surface to direct laser irradiation. EDS analysis showed an increase in Ca/P ratio after irradiation of enamel covered with biofilm. FTIR analysis showed an approximately 40% carbonate loss in the irradiated enamel samples, including those with biofilms. CONCLUSION: Biofilms protect enamel surfaces from possible morphological irradiation damage without interfering with the resultant chemical changes that may increase the enamel resistance to acid attack. Therefore, under certain exposure regimens that are thermally and mechanically safe for enamel, CO2 laser irradiation of biofilms on dental hard tissues is suggested as a potential novel preventive treatment for controlling dental caries.

Cannabigerol Effect on Streptococcus mutans Biofilms-A Computational Approach to Confocal Image Analysis.

Biofilms are complex bacterial structures in which bacterial cells thrive as a community. Many bacterial species, including pathogens, form biofilms of high complexity and adaptability to a wide range of environmental conditions. One example of these is Streptococcus mutans, a gram-positive bacterium that has been associated with caries. Cannabigerol, a non-psychoactive cannabinoid, has been shown to affect S. mutans biofilms. In order to better characterize the effect of cannabigerol on biofilms of S. mutans, this paper provides a series of computational assays for biofilm analysis, applied on confocal images of S. mutans biofilms treated with cannabigerol. Confocal images are ubiquitous in biofilm analysis-they are often used to visualize the complex structure and molecular composition of biofilm macrocolonies. In this article, we demonstrate how confocal imaging data can be used to reveal more comprehensive insights into biofilm structure and measure specific anti-biofilm effects. This is accomplished by a series of computational assays, each focusing on a different aspect of biofilm structure.

Effects of a ZnCuO-Nanocoated Ti-6Al-4V Surface on Bacterial and Host Cells.

This study aims to investigate the effects of a novel ZnCuO nanoparticle coating for dental implants-versus those of conventional titanium surfaces-on bacteria and host cells. A multispecies biofilm composed of Streptococcus sanguinis, Actinomyces naeslundii, Porphyromonas gingivalis, and Fusobacterium nucleatum was grown for 14 days on various titanium discs: machined, sandblasted, sandblasted and acid-etched (SLA), ZnCuO-coated, and hydroxyapatite discs. Bacterial species were quantified with qPCR, and their viability was examined via confocal microscopy. Osteoblast-like and macrophage-like cells grown on the various discs for 48 h were examined for proliferation using an XTT assay, and for activity using ALP and TNF-α assays. The CSLM revealed more dead bacteria in biofilms grown on titanium than on hydroxyapatite, and less on sandblasted than on machined and ZnCuO-coated surfaces, with the latter showing a significant decrease in all four biofilm species. The osteoblast-like cells showed increased proliferation on all of the titanium surfaces, with higher activity on the ZnCuO-coated and sandblasted discs. The macrophage-like cells showed higher proliferation on the hydroxyapatite and sandblasted discs, and lower activity on the SLA and ZnCuO-coated discs. The ZnCuO-coated titanium has anti-biofilm characteristics with desired effects on host cells, thus representing a promising candidate in the complex battle against peri-implantitis.

An open-source computational tool for measuring bacterial biofilm morphology and growth kinetics upon one-sided exposure to an antimicrobial source.

Bacillus subtilis biofilms are well known for their complex and highly adaptive morphology. Indeed, their phenotypical diversity and intra-biofilm heterogeneity make this gram-positive bacterium the subject of many scientific papers on the structure of biofilms. The "robustness" of biofilms is a term often used to describe their level of susceptibility to antimicrobial agents and various mechanical and molecular inhibition/eradication methods. In this paper, we use computational analytics to quantify Bacillus subtilis morphological response to proximity to an antimicrobial source, in the form of the antiseptic chlorhexidine. Chlorhexidine droplets, placed in proximity to Bacillus subtilis macrocolonies at different distances result in morphological changes, quantified using Python-based code, which we have made publicly available. Our results quantify peripheral and inner core deformation as well as differences in cellular viability of the two regions. The results reveal that the inner core, which is often characterized by the presence of wrinkled formations in the macrocolony, is more preserved than the periphery. Furthermore, the paper describes a crescent-shaped colony morphology which occurs when the distance from the chlorhexidine source is 0.5 cm, as well as changes observed in the growth substrate of macrocolonies exposed to chlorhexidine.

Topography and Expansion Patterns at the Biofilm-Agar Interface in Bacillus subtilis Biofilms.

Bacterial biofilms are complex microbial communities that are formed on various natural and synthetic surfaces. In contrast to bacteria in their planktonic form, biofilms are characterized by their relatively low susceptibility to anti-microbial treatments, in part due to limited diffusion throughout the biofilm and the complex distribution of bacterial cells within. The virulence of biofilms is therefore a combination of the structural properties and patterns of adhesion that anchor them to their host surface. In this paper, we analyze the topographical properties of Bacillus subtilis' biofilm-agar interface across different growth conditions. B. subtilis colonies were grown to maturity on biofilm-promoting agar-based media (LBGM), under standard and stress-inducing growth conditions. The biofilm-agar interface of the colony-type biofilms was modeled using confocal microscopy and computational analysis. Profilometry data were obtained from the macrocolonies and used for the analysis of the surface topography as it relates to the adhesion modes present at the biofilm-agar interface. Fluorescent microspheres were utilized to monitor the expansion patterns present at the interface between the macrocolonies and the solid growth medium. Contact surface analysis revealed topographical changes that could have a direct effect on the adhesion strength of the biofilm to its host surface, thus affecting its potential susceptibility to anti-microbial agents. The topographical characteristics of the biofilm-agar interface partially define the macrocolony structure and may have significant effects on bacterial survival and virulence.

In vivo changes in dental implant temperatures during hot beverage intake: a pilot study.

PURPOSE: The aim of this study was to measure the increase in temperature in dental implants during the intake of hot beverages in vivo. MATERIALS AND METHODS: Eight successfully osseointegrated implants in 7 subjects were examined. Each subject was asked to drink the same volume of hot beverage. While drinking, temperature changes were recorded via 3 embedded thermocouples placed (i) in the implant's internal space, (ii) at the implant-abutment interface, and (iii) at the abutment. All thermocouples were linked to a computer and analyzed with appropriate software. RESULTS: The maximum temperatures were 47.3 degrees C at the abutment, 45.6 degrees C at the implant's internal space, and 44.6 degrees C at the implant-abutment interface. A linear correlation was found between the temperatures measured (i) at the implant abutment and in the implant's internal space, and (ii) at the abutment and at the abutment-implant interface. CONCLUSIONS: Further clinical studies are required to determine whether the habitual consumption of hot food and beverages may be considered a risk factor in the success of implant-supported prostheses.

Killing mechanism of bacteria within multi-species biofilm by blue light.

Objectives: The aim of the study was to characterize the immediate and delayed effects of non-coherent blue-light treatment on the composition and viability of an in vitro biofilm composed of anaerobic multispecies, as well as the mechanisms involved. Methods: A multispecies biofilm was constructed of Streptococcus sanguinis, Actinomyces naeslundii, Porphyromonas gingivalis and Fusobacterium nucleatum, test groups were exposed to blue light. The multispecies biofilm was explored with a newly developed method based on flow cytometry and confocal microscopy. The involvement of the paracrine pathway in the phototoxic mechanism was investigated by a crossover of the supernatants between mono-species P. gingivalis and F. nucleatum biofilms. Results: Blue light led to a reduction of about 50% in the viable pathogenic bacteria P. gingivalis and F. nucleatum, vs that in the non-exposed biofilm. Biofilm thickness was also reduced by 50%. The phototoxic effect of blue light on mono-species biofilm was observed in P. gingivalis, whereas F. nucleatum biofilm was unaffected. A lethal effect was obtained when the supernatant of P. gingivalis biofilm previously exposed to blue light was added to the F. nucleatum biofilm. The effect was circumvented by the addition of reactive oxygen species (ROS) scavengers to the supernatant. Conclusion: Blue-light has an impact on the bacterial composition and viability of the multispecies biofilm. The phototoxic effect of blue light on P. gingivalis in biofilm was induced directly and on F. nucleatum via ROS mediators of the paracrine pathway. This phenomenon may lead to a novel approach for 'replacement therapy,' resulting in a less periodonto-pathogenic biofilm.

The Adaptive Morphology of Bacillus subtilis Biofilms: A Defense Mechanism against Bacterial Starvation.

Biofilms are commonly defined as accumulations of microbes, embedded in a self-secreted, polysaccharide-rich extra-cellular matrix. This study aimed to characterize specific morphological changes that occur in Bacillus subtilis biofilms under nutrient-limiting growth conditions. Under varying levels of nutrient depletion, colony-type biofilms were found to exhibit different rates of spatial expansion and green fluorescent protein production. Specifically, colony-type biofilms grown on media with decreased lysogeny broth content exhibited increased spatial expansion and more stable GFP production over the entire growth period. By modeling the surface morphology of colony-type biofilms using confocal and multiphoton microscopy, we analyzed the appearance of distinctive folds or "wrinkles" that form as a result of lysogeny broth content reduction in the solid agar growth media. When subjected to varying nutritional conditions, the channel-like folds were shown to alter their morphology; growth on nutrient-depleted media was found to trigger the formation of large and straight wrinkles connecting the colony core to its periphery. To test a possible functional role of the formed channels, a fluorescent analogue of glucose was used to demonstrate preferential native uptake of the molecules into the channels' interiors which supports their possible role in the transport of molecules throughout biofilm structures.

Genetic and physiological effects of noncoherent visible light combined with hydrogen peroxide on Streptococcus mutans in biofilm.

Oral biofilms are associated with the most common infections of the oral cavity. Bacteria embedded in the biofilms are less sensitive to antibacterial agents than planktonic bacteria are. Recently, an antibacterial synergic effect of noncoherent blue light and hydrogen peroxide (H(2)O(2)) on planktonic Streptococcus mutans was demonstrated. In this study, we tested the effect of a combination of light and H(2)O(2) on the vitality and gene expression of S. mutans embedded in biofilm. Biofilms of S. mutans were exposed to visible light (wavelengths, 400 to 500 nm) for 30 or 60 s (equivalent to 34 or 68 J/cm(2)) in the presence of 3 to 300 mM H(2)O(2). The antibacterial effect was assessed by microbial counts of each treated sample compared with that of the control. The effect of light combined with H(2)O(2) on the different layers of the biofilm was evaluated by confocal laser scanning microscopy. Gene expression was determined by real-time reverse transcription-PCR. Our results show that noncoherent light, in combination with H(2)O(2), has a synergistic antibacterial effect through all of the layers of the biofilm. Furthermore, this treatment was more effective against bacteria in biofilm than against planktonic bacteria. The combined light and H(2)O(2) treatment up-regulated the expression of several genes such as gtfB, brp, smu630, and comDE but did not affect relA and ftf. The ability of noncoherent visible light in combination with H(2)O(2) to affect bacteria in deep layers of the biofilm suggests that this treatment may be applied in biofilm-related diseases as a minimally invasive antibacterial procedure.

Temperature changes in dental implants following exposure to hot substances in an ex vivo model.

OBJECTIVES: The habitual consumption of extremely hot foods and beverages may affect implant treatment modality. Our objectives were to: (i) establish the maximum temperature produced intra-orally while consuming very hot substances and (ii) use these values in an ex vivo model to assess the temperature changes along the implant-bone interface. MATERIALS AND METHODS: Temperatures were measured using thermocouples linked to a computer. The thermocouple electrodes were attached to the tooth-gum interface of the interproximal areas in 14 volunteers during consumption of extremely hot foods and beverages. The in vivo measured temperature values obtained were used in an ex vivo model of a bovine mandible block with an implant and with an assembled abutment. Temperatures were measured by thermocouple electrodes attached to five locations, three of them along the implant-bone interface. RESULTS: During consumption of a hot beverage, a maximum temperature of up to 76.3 degrees C was recorded, and a calculated extreme intra-oral temperature of 61.4 degrees C was established. The ex vivo model showed a high correlation between the temperature measured at the abutment and that measured at the abutment-implant interface and inside the implant, reaching maximum temperatures close to 60 degrees C. At the mid-implant-bone and apical implant-bone interfaces, the maximum temperatures measured were 43.3 and 42 degrees C, respectively. CONCLUSIONS: The maximum temperatures measured at the implant-bone interfaces reached the temperature threshold of transient changes in bone (42 degrees C). The results of this study support the notion that intra-oral temperatures, developed during the consumption of very hot substances, may be capable of damaging peri-implant tissues.

Antibacterial properties of self-etching dental adhesive systems.

BACKGROUND: Dental adhesives with antibacterial properties may reduce recurrent or secondary caries. The authors conducted a study to examine the immediate and long-lasting antibacterial properties of four self-etching adhesive systems. METHODS: The authors used the agar diffusion test (ADT) and direct contact test (DCT) to measure the antibacterial properties of AdheSe (Ivoclar Vivadent, Schaan, Liechtenstein), Adper Prompt L-Pop (3M ESPE, Seefeld, Germany), Clearfil Protect Bond (Kuraray, Kurashiki, Okayama, Japan) and Xeno III (Dentsply, Konstanz, Germany) on Streptoccocus mutans after aging samples in phosphate-buffered saline for one, two, seven and 14 days. RESULTS: Only Clearfil Protect Bond showed an inhibition halo in the ADT. In the DCT, fresh samples of all of the tested materials exhibited potent antibacterial properties, which were maintained by AdheSe for one day and Clearfil Protect Bond for seven days. None of the adhesive systems exhibited any antibacterial properties after 14 days. CONCLUSIONS: All of the tested adhesives had an immediate bactericidal effect on S. mutans. None, however, had long-lasting antibacterial properties. CLINICAL IMPLICATIONS: The application of self-etching adhesive materials could contribute to the immediate elimination of residual bacteria. The likelihood of developing secondary caries as a consequence of bacterial microleakage may not be affected by the use of the adhesive systems tested in this study.

Bacillus subtilis Biofilm Development - A Computerized Study of Morphology and Kinetics.

Biofilm is commonly defined as accumulation of microbes, embedded in a self-secreted extra-cellular matrix, on solid surfaces or liquid interfaces. In this study, we analyze several aspects of Bacillus subtilis biofilm formation using tools from the field of image processing. Specifically, we characterize the growth kinetics and morphological features of B. subtilis colony type biofilm formation and compare these in colonies grown on two different types of solid media. Additionally, we propose a model for assessing B. subtilis biofilm complexity across different growth conditions. GFP-labeled B. subtilis cells were cultured on agar surfaces over a 4-day period during which microscopic images of developing colonies were taken at equal time intervals. The images were used to perform a computerized analysis of few aspects of biofilm development, based on features that characterize the different phenotypes of B. subtilis colonies. Specifically, the analysis focused on the segmented structure of the colonies, consisting of two different regions of sub-populations that comprise the biofilm - a central "core" region and an "expanding" region surrounding it. Our results demonstrate that complex biofilm of B. subtillis grown on biofilm-promoting medium [standard lysogeny broth (LB) supplemented with manganese and glycerol] is characterized by rapidly developing three-dimensional complex structure observed at its core compared to biofilm grown on standard LB. As the biofilm develops, the core size remains largely unchanged during development and colony expansion is mostly attributed to the expansion in area of outer cell sub-populations. Moreover, when comparing the bacterial growth on biofilm-promoting agar to that of colonies grown on LB, we found a significant decrease in the GFP production of colonies that formed a more complex biofilm. This suggests that complex biofilm formation has a diminishing effect on cell populations at the biofilm core, likely due to a combination of reduced metabolic rate and increased levels of cell death within this region.

Effect of visible light on malodour production by mixed oral microflora.

Oral malodour is considered to be caused by the proteolytic activity of anaerobic Gram-negative oral bacteria. In a previous study, it was shown that these bacteria were susceptible to blue light (wavelengths of 400-500 nm). In this study, the effect of blue light on malodour production by mixed oral microflora was tested in a salivary incubation assay. Whole saliva samples were exposed to a xenon light source for 30, 60, 120 and 240 s, equivalent to fluences of 34, 68, 137 and 274 J cm(-2), respectively. Malodour was scored by two judges. The levels of volatile sulfide compounds (VSC) were measured using a sulfide monitor (Halimeter), the microbial population was assessed using viable counts and microscopy, salivary protein degradation was followed by SDS-PAGE densitometry and VSC-producing bacteria were demonstrated using a differential agar. The results showed that the exposure of mixed salivary microflora to blue light caused a reduction in malodour production concomitant with a selective inhibitory effect on the population of Gram-negative oral bacteria. These results suggest that light exposure might have clinical applications for the treatment of oral malodour.

Mechanism of visible light phototoxicity on Porphyromonas gingivalis and Fusobacterium nucleatum.

Phototoxicity of visible light laser on the porphyrin-producing bacteria, Porphyromonas gingivalis, in the absence of photosensitizers and under aerobic conditions was shown in previous studies. Recently, we found that the noncoherent visible light sources at wavelengths of 400-500 nm, commonly used in restorative dentistry, induced a phototoxic effect on P. gingivalis, as well as on Fusobacterium nucleatum, and to a lesser extent on the Streptococci sp. To elucidate the mechanism of this phototoxic effect, P. gingivalis and F. nucleatum were exposed to light (1) under aerobic and anaerobic environments and (2) in the presence of scavengers of reactive oxygen species (ROS). Phototoxic effect was not observed when the bacteria were exposed to light under anaerobic conditions. Dimethyl thiourea, a hydroxyl radical scavenger, was effective in reducing phototoxicity (P

Phototoxic effect of visible light on Porphyromonas gingivalis and Fusobacterium nucleatum: an in vitro study.

The antibacterial effect of visible light irradiation combined with photosensitizers has been reported. The objective of this was to test the effect of visible light irradiation without photosensitizers on the viability of oral microorganisms. Strains of Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus mutans and Streptococcus faecalis in suspension or grown on agar were exposed to visible light at wavelengths of 400-500 nm. These wavelengths are used to photopolymerize composite resins widely used for dental restoration. Three photocuring light sources, quartz-tungsten-halogen lamp, light-emitting diode and plasma-arc, at power densities between 260 and 1300 mW/cm2 were used for up to 3 min. Bacterial samples were also exposed to a near-infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. The results show that blue light sources exert a phototoxic effect on P. gingivalis and F. nucleatum. The minimal inhibitory dose for P. gingivalis and F. nucleatum was 16-62 J/cm2, a value significantly lower than that for S. mutans and S. faecalis (159-212 J/cm2). Near-infrared diode laser irradiation did not affect any of the bacteria tested. Our results suggest that visible light sources without exogenous photosensitizers have a phototoxic effect mainly on Gram-negative periodontal pathogens.

Diagnosis of approximal caries: bite-wing radiology versus the Ultrasound Caries Detector. An in vitro study.

OBJECTIVE: We sought to examine the validity, sensitivity, and specificity of bite-wing radiographs and a high-frequency sound wave device (the Ultrasound Caries Detector) used to detect caries on contacting approximal surfaces. METHODS: A total of 36 extracted premolars and molars were first visually examined for the presence of caries; then a probe was used. Twelve models were prepared, each containing 3 teeth with 2 approximal surfaces and 2 contacted surfaces (of adjacent teeth). Bite-wing radiographs were taken and evaluated for proximal caries lesions. A high-frequency sound wave (ultrasound) device called the Ultrasound Caries Detector was also used to detect caries. Examinations were repeated after 1 week. Teeth were then sectioned and viewed under a stereomicroscope at 20x magnification, with which the true interproximal caries diagnosis was validated. The receiver operating characteristic curves were computed to establish the accuracy of the observer data. RESULTS: The efficacy of the ultrasound diagnostic device for cavitated carious lesion detection was assessed by determining its specificity and sensitivity, 1.0 for each, in comparison with those of bite-wing radiography, 0.92 and 0.90, respectively (P <.001). The mean receiver operating characteristic value for the area under the curve was 0.934 with bite-wing radiography and 1 with the ultrasound diagnostic device. CONCLUSIONS: Under in vitro conditions, the ultrasound diagnostic device had a higher sensitivity and specificity, in terms of the detection of approximal carious lesions, than bite-wing radiographs.