Effects of Bleaching Associated with Er:YAG and Nd:YAG Laser on Enamel Structure and Bacterial Biofilm Formation

OBJECTIVE

To compare the effects of bleaching associated with Er:YAG and Nd:YAG laser on enamel structure and mixed biofilm formation on teeth surfaces.

MATERIALS AND METHODS

Sixty-eight enamel samples were randomly divided into four groups (n = 17), control, Opalescence Boost only, Opalescence Boost plus Er: YAG laser, and Opalescence Boost plus Nd:YAG laser. The structure was observed using SEM after bleaching. Subsequently, the treated enamel samples were also cultured in suspensions of Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, and Fusobacterium nucleatum (Fn) for 24 and 48 h. Biofilm formation was quantified by crystal violet staining, and the structure was visualized by confocal laser scanning microscopy. The data were analyzed using the Kruskal-Wallis method.

RESULTS

The enamel structure significantly changed after bleaching. There was no obvious difference in the biofilm formation after 24 h; however, after 48 hours, the amount of biofilm increased significantly. Remarkably, the amount was significantly higher on enamel bleached only, however, there was no significant difference between samples bleached with Er:YAG or Nd:YAG laser compared to the control.

CONCLUSIONS

Bleaching only appeared to markedly promote biofilm formation after 48 h, and the biofilms on samples bleached with Er:YAG or Nd:YAG laser did not change significantly, showing that bleaching with Er:YAG or Nd:YAG laser can be safely applied in clinical practice.

The cariogenic effect of starch on oral microcosm grown within the dual constant depth film fermenter

Evidence on the link between starch intake and caries incidence is conflicting, therefore the cariogenicity of starch compared with sucrose was explored using a dual Constant Depth Film Fermenter (dCDFF) biotic model system. Bovine enamel discs were used as a substrate and the dCDFF was inoculated using human saliva. CDFF units were supplemented with artificial saliva growth media at a constant rate to mimic resting salivary flow rate over 14 days. The CDFF units were exposed to different conditions, 2% sucrose or 2% starch 8 times daily and either no additional fluoride or 1450 ppm F- twice daily. Bovine enamel discs were removed at intervals (days 3, 7, 10 and 14) for bacterial enumeration and enamel analysis using Quantitative Light Induced Fluorescence (QLF) and Transverse Microradiography (TMR). Results showed that in the absence of fluoride there was generally no difference in mineral loss between enamel exposed to either sucrose or starch when analysed using TMR and QLF (P > 0.05). In the presence of fluoride by day 14 there was significantly more mineral loss under starch than sucrose when analysed with TMR (P < 0.05). It was confirmed that starch and sucrose are similarly cariogenic within the dCDFF in the absence of fluoride. With the aid of salivary amylase, the bacteria utilise starch to produce an acidic environment similar to that of bacteria exposed to sucrose only. In the presence of fluoride, starch was more cariogenic which may be due to the bacteria producing a more hydrophobic intercellular matrix lowering the penetration of fluoride through the biofilm. This is significant as it indicates that the focus on sugars being the primary cause of caries may need re-evaluating and an increase in focus on carbohydrates is needed as they may be similarly cariogenic as sugars if not more so.

Effects of Experimental Agents Containing Tannic Acid or Chitosan on the Bacterial Biofilm Formation in Situ

Chitosan and tannic acid are known for their antibacterial properties. In the present in-situ study, their antibacterial and anti-adherent effects on biofilm formation on enamel were investigated. Six subjects carried upper jaw splints with bovine enamel specimens, allowing in-situ biofilm formation. During the two-day trial, subjects rinsed with experimental solutions that contained either chitosan, tannic acid (pH = 2.5), tannic acid (pH = 7) or hydrochloric acid. Water served as the negative and chlorhexidine as the positive control. Rinsing occurred four or five times following two different rinsing protocols to investigate both the immediate and long-lasting effects. After 48 h of intraoral exposure, the dental plaque was stained with LIVE/DEAD^® BacLight, and fluorescence micrographs were evaluated by using the software ImageJ. The results were verified by scanning electron microscopy. Rinsing with chitosan resulted in little immediate antibacterial and anti-adherent effects but failed to show any long-lasting effect, while rinsing with tannic acid resulted in strong immediate and long-lasting effects. Except for a slightly lower antibacterial effect, the neutral solution of tannic acid was as good as the acidic solution. Hydrochloric acid showed neither an antibacterial nor an anti-adherent effect on dental biofilm formation. Experimental solutions containing tannic acid are promising anti-biofilm agents, irrespective of the pH values of the solutions. Chitosan, on the other hand, was not able to prevent biofilm formation.

Novel Nanocomposite Inhibiting Caries at the Enamel Restoration Margins in an In Vitro Saliva-Derived Biofilm Secondary Caries Model

Secondary caries often occurs at the tooth-composite margins. This study developed a novel bioactive composite containing DMAHDM (dimethylaminohexadecyl methacrylate) and NACP (nanoparticles of amorphous calcium phosphate), inhibiting caries at the enamel restoration margins in an in vitro saliva-derived biofilm secondary caries model for the first time. Four composites were tested: (1) Heliomolar nanocomposite, (2) 0% DMAHDM + 0% NACP, (3) 3% DMAHDM + 0% NACP, (D) 3% DMAHDM + 30% NACP. Saliva-derived biofilms were tested for antibacterial effects of the composites. Bovine enamel restorations were cultured with biofilms, Ca and P ion release of nanocomposite and enamel hardness at the enamel restoration margins was measured. Incorporation of DMAHDM and NACP into composite did not affect the mechanical properties (p > 0.05). The biofilms’ CFU (colony-forming units) were reduced by 2 logs via DMAHDM (p < 0.05). Ca and P ion release of the nanocomposite was increased at cariogenic low pH. Enamel hardness at the margins for DMAHDM group was 25% higher than control (p < 0.05). With DMAHDM + NACP, the enamel hardness was the greatest and about 50% higher than control (p < 0.05). Therefore, the novel composite containing DMAHDM and NACP was strongly antibacterial and inhibited enamel demineralization, resulting in enamel hardness at the margins under biofilms that approached the hardness of healthy enamel.

In Vitro Caries Models for the Assessment of Novel Restorative Materials

Due to the high failure rates of traditional dental restorations, there is an ongoing effort to develop modified and new restorative biomaterials in dentistry. Being the most commonly used restorative material, most of these efforts primarily aim to improve dental composite. Generally, the main objective of such modifications is to enhance the restorative physical and antimicrobial properties in order to limit micro-leakage and inhibit bacterial biofilm cultivation. Herein, we describe the process of designing a simple in vitro model to assess the physical and antimicrobial properties of novel restorative materials in addition to evaluating their effect on the fragile balance between enamel de- and remineralization.

Protocols to Study Dental Caries In Vitro: Microbial Caries Models

Caries lesions result from the interaction between dental biofilm and sugars. Since the biofilm is an important component in the etiology of the disease, biofilm models have been developed to study the cariogenicity of dietary sugars, as well as the anticaries effect of substances. Two of such models, termed as "static" or "continuous flow," are described in details here together with their advantages, limitations, and applications.

Cariogenic potential of sweet flavors in electronic-cigarette liquids

Background

Most electronic-cigarette liquids contain propylene glycol, glycerin, nicotine and a wide variety of flavors of which many are sweet. Sweet flavors are classified as saccharides, esters, acids or aldehydes. This study investigates changes in cariogenic potential when tooth surfaces are exposed to e-cigarette aerosols generated from well-characterized reference e-liquids with sweet flavors.

Methods

Reference e-liquids were prepared by combining 20/80 propylene glycol/glycerin (by volume fraction), 10 mg/mL nicotine, and flavors. Aerosols were generated by a Universal Electronic-Cigarette Testing Device (49.2 W, 0.2 Ω). Streptococcus mutans (UA159) were exposed to aerosols on tooth enamel and the biological and physiochemical parameters were measured.

Results

E-cigarette aerosols produced four-fold increase in microbial adhesion to enamel. Exposure to flavored aerosols led to two-fold increase in biofilm formation and up to a 27% decrease in enamel hardness compared to unflavored controls. Esters (ethyl butyrate, hexyl acetate, and triacetin) in e-liquids were associated with consistent bacteria-initiated enamel demineralization, whereas sugar alcohol (ethyl maltol) inhibited S. mutans growth and adhesion. The viscosity of the e-liquid allowed S. mutans to adhere to pits and fissures. Aerosols contained five metals (mean ± standard deviation): calcium (0.409 ± 0.002) mg/L, copper (0.011 ± 0.001) mg/L, iron (0.0051 ± 0.0003) mg/L, magnesium (0.017 ± 0.002) mg/L, and silicon (0.166 ± 0.005) mg/L.

Conclusions

This study systematically evaluated e-cigarette aerosols and found that the aerosols have similar physio-chemical properties as high-sucrose, gelatinous candies and acidic drinks. Our data suggest that the combination of the viscosity of e-liquids and some classes of chemicals in sweet flavors may increase the risk of cariogenic potential. Clinical investigation is warranted to confirm the data shown here.

Laser microtextured titanium implant surfaces reduce in vitro and in situ oral biofilm formation

INTRODUCTION

Micro- or nano-topography can both provide antimicrobial properties and improve osseointegration of dental implant titanium surfaces. Laser treatment is one of the best surface microtexturing techniques. The aim of this study was to evaluate in vitro and in situ biofilm formation on a laser-treated titanium surface, comparing it with two conventional surfaces, machined and grit-blasted.

METHODS

For the in vitro experiment, an oral microcosm biofilm model was developed on the surface of titanium disks and reference human enamel using a bioreactor for 48 h. For the in situ experiment, titanium implants with laser-treated, machined and grit-blasted surfaces were mounted on intraoral trays and worn by ten volunteers for 48 h. Biofilm formation was quantitatively evaluated, and surfaces were analyzed using confocal laser scanning microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy.

RESULTS–IN VITRO STUDY

Biofilm structures with a prevalence of viable cells covered most of the machined, grit-blasted and human enamel surfaces, whereas less dense biofilm structures with non-confluent microcolonies were observed on the laser-treated titanium. Laser-treated titanium showed the lowest biofilm formation, where microorganisms colonized the edges of the laser-created pits, with very few or no biofilm formation observed inside the pits.

RESULTS–IN SITU STUDY

The biofilm formation pattern observed was similar to that in the in vitro experiment. Confocal laser scanning microscopy showed complete coverage of the implant threads, with mostly viable cells in grit-blasted and machined specimens. Unexpectedly, laser-treated specimens showed few dead microbial cells colonizing the bottom of the threads, while an intense colonization was found on the threading sides.

CONCLUSION

This data suggests that laser-created microtopography can reduce biofilm formation, with a maximum effect when the surface is blasted orthogonally by the laser beam. In this sense the orientation of the laser beam seems to be relevant for the biological interaction with biofilms.

Effect of a mouthrinse containing Malva sylvestris on the viability and activity of microcosm biofilm and on enamel demineralization compared to known antimicrobials mouthrinses

The purpose of this study was to evaluate the antimicrobial (anti-biofilm) and anti-caries (enamel demineralization prevention) effects of Malva sylvestris (Malvatricin^® Plus) compared with known antimicrobial mouthrinses. Microcosm biofilm was produced on enamel, using inoculum from pooled human saliva mixed with McBain saliva (0.2% sucrose) for 14 days. The biofilm was treated with mouthrinses for 1 min day^-1. Oral-B^® Complete, Listerine^® Zero and Malvatricin^® Plus had the greatest effect on the reduction of biofilm viability (p < 0.0001). On the other hand, lactic acid production was reduced significantly with PerioGard^®, Noplak^® Max and Listerine^® Zero compared with the control (p < 0.0001). No significant differences were found among the mouthrinses with respect to the colony-forming unit counting (total microorganisms, total streptococci, mutans streptococci and lactobacilli) and extracellular polysaccharide production. Enamel demineralization was reduced significantly with PerioGard^®, Noplak^® Max and Malvatricin^® Plus compared with the control (p < 0.0001). Malva sylvestris has a comparable anti-caries effect to chlorhexidine mouthrinses.

Red fluorescence of dental biofilm as an indicator for assessing the efficacy of antimicrobials

The study aimed to determine whether the red fluorescence (RF) of a dental microcosm biofilm as measured with quantitative light-induced fluorescence (QLF) technology is useful for assessing the efficacy of antimicrobials. Dental microcosm biofilms were formed on bovine enamel discs and grown under 0.3% sucrose challenge and treated with chlorhexidine (CHX) solutions at different concentrations (0.05%, 0.1%, and 0.5%) plus a negative control [sterile distilled water (DW)] twice daily for 7 days. The biofilms were photographed using a QLF-digital system to evaluate the RF by calculating the red/green ratio, and pH values of the medium were measured daily. After 7 days, the bacterial viability of the biofilm was assessed by measuring the counts of viable total bacteria and aciduric bacteria, and the percentage surface microhardness changes (%SHC) was evaluated. The RF and cariogenic properties were compared for the different concentrations of CHX, and their correlations were examined. The RF and its increase rate were much lower for CHX-treated biofilms than for DW-treated biofilms. The RF after 7 days of maturation decreased significantly with increasing CHX concentrations (p<0.001) and was from 31% (for 0.05% CHX) to 46% (for 0.5% CHX) lower than that of the DW group. Strong correlations were reported between the RF of the 7-day-maturation biofilms and cariogenic properties, such as the number of total bacteria (r=0.93), number of aciduric bacteria (r=0.97), supernatant pH (r=0.43), and %SHC (r=0.98). In conclusion, the RF of dental biofilms as measured with QLF technology can be used to nondestructively assess and monitor the effect of antimicrobials against biofilm.

Initial microbial colonization of enamel in children with different levels of caries activity: An in situ study

PURPOSE

To investigate patterns of overnight in situ microbial colonization of enamel in children.

METHODS

Overall, 29 children (aged 5-9 years) participated in the study. Nine were caries-free with no decayed, missing, or filled teeth (DMFT), 11 were caries-rehabilitated (DMFT ≥ 2, no active carious lesions), and nine were caries-active (DMFT ≥ 2, at least two carious lesions). Bovine enamel samples were fixed on individual upper jaw splints stored overnight in situ. 4',6-diamidino-2-phenylindole (DAPI) combined with Concanavalin A staining was applied for fluorescence microscopic visualization of total adherent bacteria and glucans. Fluorescence in situ hybridization (FISH) was used for distinction of eubacteria, streptococci, and Candida albicans. Salivary samples were investigated for Streptococcus mutans (S. mutans) by using CRT bacteria test and yeasts with Calcofluor white (CFW) staining.

RESULTS

With all fluorescence methods, bacteria but not Candida albicans were detected on enamel samples. No statistically significant differences were observed in distribution patterns of the adherent bacteria between the groups. CFW staining indicated fungal structures in saliva samples of all participants. Based on CRT test results, the lowest amount of S. mutans were observed in caries-free children. Thus, initial microbial colonization patterns of enamel in children are not influenced by caries activity.

CLINICAL SIGNIFICANCE

Caries activity in children may influence the process of initial bioadhesion and thus distribution patterns of bacterial attachment to the enamel surface. Investigation of in situ biofilm formation might provide valuable insights regarding the varying caries susceptibility in children.

Influence of Biosurfactant on Interactive Forces between Mutans Streptococci and Enamel Measured by Atomic Force Microscopy

Although interactive forces, influenced by environmental conditions, between oral bacteria and tooth surfaces are important for the development of plaque, they have never been estimated. It is hypothesized that interactive forces, as measured by atomic force microscopy, between enamel with or without a pellicle and two strains of mutans streptococci become less attractive by the application of a Streptococcus mitis BMS biosurfactant coating. Upon approach of each of the strains toward bare and pellicle-coated enamel, adsorbed biosurfactant increased the range of the repulsive forces. Upon retraction of the enamel surface, small adhesion forces (0.8–0.9 nN) were measured for bare enamel that almost disappeared after biosurfactant coating. The prevalence and magnitude of the adhesion forces also decreased upon pellicle-coating of the enamel, with a minor effect of adsorbed biosurfactant. These findings indicate that adsorbed S. mitis BMS biosurfactant changes the interactive forces between the mutans streptococci studied and enamel, explaining the effects of biosurfactant on adhesion.

Association of Candida Species Isolated From the Dental Plaque of HIV-infected Children and Prevalence of Early Carious Lesions

PURPOSE

The purposes of this study were to: (1) quantify and identify Candida species (spp.) in the dental plaque of children infected with the human immunodeficiency virus (HIV) and compare with noninfected children; and (2) determine the association of Candida spp. with the presence of caries.

METHODS

Seventy HIV-infected and 55 non-HIV-infected three- to 12-year-old children were examined to determine caries prevalence. After a visual inspection, supragingival plaque was collected from the cervical region using standard dental curettes. The material was transferred to microtubes and submitted for analysis to identify and quantify the presence of Candida spp.

RESULTS

Candida spp. were more prevalent in the HIV-infected group (72.9 percent) than in the control group (20 percent), and the most prevalent specie was Candida albicans. Caries was found in 72.9 percent of the HIV-infected group and in 58.2 percent of the control group, but a significant difference was only found in the presence of active white spot lesions between the groups.

CONCLUSIONS

The dental plaque of HIV-infected children was colonized by Candida species to a much greater extent than that of non-HIV-infected children, and this colonization was significantly associated with the prevalence of early carious lesions in enamel.

Understanding Caries From the Oral Microbiome Perspective

Dental caries is a major disease of the oral cavity with profound clinical significance. Caries results from a transition of a healthy oral microbiome into an acidogenic community of decreased microbial diversity in response to excessive dietary sugar intake. Microbiological cultivation, molecular identification, gene expression and metabolomic analyses show the importance of the entire microbial community in understanding the role of the microbiome in the pathology of caries.

Effect of silver nanoparticles on the physicochemical and antimicrobial properties of an orthodontic adhesive

OBJECTIVE

This study aimed to incorporate silver nanoparticle solutions (AgNP) in an orthodontic adhesive and evaluate its physicochemical and antimicrobial properties.

MATERIAL AND METHODS

Silver nanoparticle solutions were added to a commercial adhesive in different concentrations (w/w): 0%, 0.11%, 0.18%, and 0.33%. Shear bond strength (SBS) test was performed after bonding metal brackets to enamel. Raman spectroscopy was used to analyze in situ the degree of conversion (DC) of the adhesive layer. The surface free energy (SFE) was evaluated after the measurement of contact angles. Growth inhibition of Streptococcus mutans in liquid and solid media was determined by colony-forming unit count and inhibition halo, respectively. One-way ANOVA was performed for SBS, DC, SFE, and growth inhibition.

RESULTS

The incorporation of AgNP solution decreased the SBS (p<0.001) and DC in situ (p<0.001) values. SFE decreased after addition of 0.18% and 0.33% AgNP. Growth inhibition of S. mutans in liquid media was obtained after silver addition (p<0.05).

CONCLUSIONS

The addition of AgNP solutions to Transbond™ XT adhesive primer inhibited S. mutans growth. SBS, DC, and SFE values decreased after incorporation up to 0.33% AgNP solution without compromising the chemical and physical properties of the adhesive.

Validation of a Cariogenic Biofilm Model to Evaluate the Effect of Fluoride on Enamel and Root Dentine Demineralization

Due to gingival recession both enamel and root dentine are at risk of developing caries. Both tissues are exposed to a similar environment, however there is not a validated model to evaluate the effect of fluoride on these dental substrates simultaneously. Hence, this study aimed to validate a caries model to evaluate the effect of fluoride to prevent demineralization on enamel and root-dentine. Streptococcus mutans UA159 biofilms were formed on saliva-coated bovine enamel and root dentine slabs (n = 12 per group) mounted in the same well of culture plates. The biofilms were exposed 8×/day to 10% sucrose and treated 2×/day with fluoridated solutions containing 0, 150, 450, or 1,350 ppm F; thus, simulating the use of low to high fluoride concentration toothpastes. The pH values of the culture medium was monitored 2×/day as a biofilm acidogenicity indicator. After 96 h, biofilms were collected for fluoride concentration analysis. The percentage of surface hardness loss (%SHL) was calculated for slabs. The fluoride uptake by the enamel and dentine was also determined. The model showed a dose-response because the biofilm and fluoride uptake increased and %SHL decreased at increasing fluoride concentrations (p < 0.05). Fluoride in the biofilm formed on dentine and fluoride uptake by dentine were higher than those for enamel. With the same fluoride concentration treatment, the percentage of reduction of demineralization was lower for dentine than for enamel. In conclusion, the model was validated in terms of a dose-response effect of fluoride on enamel and root dentine. Furthermore, the findings support the clinical data, suggesting that higher fluoride concentrations are necessary to control caries of root dentine than of enamel.

The Polyphenolic Composition of Cistus incanus Herbal Tea and Its Antibacterial and Anti-adherent Activity against Streptococcus mutans

The Mediterranean plant Cistus incanus is rich in polyphenols and has shown several pharmacological activities, mainly antibacterial effects. Furthermore, in situ studies revealed that a C. incanus infusion reduces the initial bacterial adhesion in the oral cavity due to the polyphenols, an indication that C. incanus might reduce the risk of caries disease. In the present study, the polyphenols from four different commercial C. incanus herbal teas were extracted by standardized accelerated solvent extraction for in vitro tests and by an infusion for in situ tests. Both extracts were characterized qualitatively and quantitatively by high-performance liquid chromatography and only the polyphenol content differed slightly. By means of diode array detection and mass spectrometry, 29 polyphenols, including ellagitannins, flavanols, and glycosylated flavonols, were identified. Thereby, only quantitative but no qualitative differences between the four samples were detected. Furthermore, the in vitro antibacterial activity of the C. incanus accelerated solvent extracts against Streptococcus mutans, one of the primary cariogenic bacterial species, was examined using a live/dead assay (BacLight®). With this approach, C. incanus yielded antibacterial properties. Additional in situ experiments indicated that rinses with a C. incanus infusion reduced the initial bacterial colonization of enamel samples exposed to oral fluids for over eight hours. Furthermore, it was shown by transmission electron microscopy that the application of a C. incanus infusion modifies the ultrastructure of the acquired enamel pellicle, yielding a more electron-dense morphology. It can be assumed that the polyphenols are responsible for the observed effects.

Effect of sonic vibration of an ultrasonic toothbrush on the removal of Streptococcus mutans biofilm from enamel surface

PURPOSE

To evaluate in vitro the effect of sonic vibration of an ultrasonic toothbrush in the removal of Streptococcus mutans (S. mutans) biofilm from human enamel.

METHODS

S. mutans dental biofilm was formed in vitro on human enamel blocks coated by salivary pellicle. The blocks were incubated with a suspension of S. mutans at 37°C for 24 or 72 hours. The blocks were divided to one of three conditions according to the different toothbrush action modes: ultrasound plus sonic vibration (U+SV), ultrasound-only (U) and no ultrasound and no sonic vibration (control). Samples were exposed to each mode for 3 minutes with the toothbrush bristles placed 5 mm away from the enamel block surface. The samples were observed by scanning electron microscopy (SEM) and quantification of S. mutans was performed.

RESULTS

U+SV showed lower bacterial counts compared to U and control on the 72 hour-biofilm (P < 0.05). The SEM analysis revealed that U+SV and U disrupted the S. mutans chains in the 24- and 72-hour biofilm.

Natural and Controlled Demineralization for Study Purposes in Minimally Invasive Dentistry

Artificially induced demineralization of enamel is frequently used during laboratory tests, particularly in minimally invasive dentistry. The aim of this study was to analyze demineralization techniques of hard tooth tissue applicable in the research of materials in minimally invasive dentistry. The most important factor taken into consideration when designing a method is to make a model as closely similar to the natural environment of the human oral cavity as it is possible. In vitro models allow us to maintain stability and control over the environment and guarantee repeatability of the results. There are main models to produce dental caries outside of the body. The first model is chemical and it uses acids. It is simplified and reflects the actual environment of the oral cavity to a lesser degree. The second model is biological and it is more accurate as it uses microorganisms which build the dental plaque. Among in vitro protocols are also used pH-cycling models. Based on the available literature, it was found that bovine teeth and human teeth with demineralization diagnosed while still inside the oral cavity are the most frequently used kind of specimens in research conducted with use of the chemical model. Not a single case of use of the biological and pH-cycling models were found in the available literature related to the research of infiltrants in minimally invasive dentistry.

Streptococcus mutans biofilm formation and release of fluoride from experimental resin-based composites depending on surface treatment and S-PRG filler particle fraction

PURPOSE

To evaluate fluoride release and biofilm formation on resin-based composites (RBCs) including surface pre-reacted glass ionomer (S-PRG) filler particles.

MATERIALS AND METHODS

Specimens were prepared from experimental RBCs including different fractions of S-PRG fillers (0/10/30/50/70% w/v). RBCs were light cured against mylar strips (MYL), and 50% of the specimens were additionally polished to a high gloss (POL). Surface roughness (SR), surface free energy (SFE) and fluoride release were determined. Streptococcus mutans biofilm formation (SMBF) was simulated for 48 h and 120 h; adherent viable biomass was assessed using an MTT-based assay.

RESULTS

The highest SR was identified for POL specimens manufactured from the RBC with a filler fraction of 70%. For all specimens and surface treatments, polishing caused an increase in surface free energy. For both MYL and POL specimens, increasing the filler fraction coincided with an increased release of fluoride; a higher release of fluoride was identified for POL specimens with filler fractions of 50% and 70% in comparison to their MYL counterparts. Release of fluoride was lower after 120 h than after 48 h. No differences in SMBF were identified between MYL and POL specimens with identical filler fractions after 48 h of biofilm formation; with increasing filler fractions, a tendency towards decreasing SMBF was observed. After 120 h, less SMBF was identified for POL specimens with filler fractions of 30%, 50% and 70% in comparison to corresponding MYL specimens.

CONCLUSION

The inclusion of S-PRG fillers and an effective surface treatment may reduce biofilm formation on RBCs.

Early canine plaque biofilms: characterization of key bacterial interactions involved in initial colonization of enamel

Periodontal disease (PD) is a significant problem in dogs affecting between 44% and 63.6% of the population. The main etiological agent for PD is plaque, a microbial biofilm that colonizes teeth and causes inflammation of the gingiva. Understanding how this biofilm initiates on the tooth surface is of central importance in developing interventions against PD. Although the stages of plaque development on human teeth have been well characterized little is known about how canine plaque develops. Recent studies of the canine oral microbiome have revealed distinct differences between the canine and human oral environments and the bacterial communities they support, particularly with respect to healthy plaque. These differences mean knowledge about the nature of plaque formation in humans may not be directly translatable to dogs. The aim of this study was to identify the bacterial species important in the early stages of canine plaque formation in vivo and then use isolates of these species in a laboratory biofilm model to develop an understanding of the sequential processes which take place during the initial colonization of enamel. Supra-gingival plaque samples were collected from 12 dogs at 24 and 48 hour time points following a full mouth descale and polish. Pyrosequencing of the 16S rDNA identified 134 operational taxonomic units after statistical analysis. The species with the highest relative abundance were Bergeyella zoohelcum, Neisseria shayeganii and a Moraxella species. Streptococcal species, which tend to dominate early human plaque biofilms, had very low relative abundance. In vitro testing of biofilm formation identified five primary colonizer species, three of which belonged to the genus Neisseria. Using these pioneer bacteria as a starting point, viable two and three species communities were developed. Combining in vivo and in vitro data has led us to construct novel models of how the early canine plaque biofilm develops.

Correlation between the cariogenic response in biofilms generated from saliva of mother/child pairs

This study aimed to correlate the cariogenic responsiveness of biofilms generated from the saliva of mothers and children. The mother-child pairs were classified according to the children's caries levels: caries-free, early childhood caries (ECC) or severe ECC. Microcosm biofilms were grown on enamel discs for 10 days. Factors under evaluation were caries experience levels, inoculum source (mothers and children) and growth conditions including cariogenic challenge (growth medium provided with and without sucrose) and no cariogenic challenge (growth medium sucrose-free). Statistical analysis was performed with ANOVA and Tukey's test, and the Spearman correlation test. Regular sucrose exposure resulted in a higher surface hardness change (%SHC). The correlation between biofilms formed from saliva of mother-child pairs was significant regarding pH, total aciduric microorganisms and lactobacilli counts under cariogenic challenge. Biofilm growth originating from mother-child pairs under regular sucrose exposure promoted the same cariogenic response independently of caries experience and the microbiological profile of the donors.

Influence of the number of adhesive layers on adhesive interface properties under cariogenic challenge using streptococcus mutans

PURPOSE

To test the hypothesis that the number of adhesive layers influences the adhesive interface properties under cariogenic challenge conditions using a Streptococcus mutans model.

MATERIALS AND METHODS

Bovine teeth (n = 90) were sectioned into blocks of 5 mm and divided into two groups for microleakage testing (n = 60) and tensile bond strength testing (n = 30). In each group, the samples were subdivided into subgroups according to the number of adhesive layers applied on the dentin: one (SB1), two (SB2), and three adhesive layers (SB3). The samples of the control groups were placed in BHI broth medium supplemented with 2% sucrose without microorganisms, and the experimental groups were submitted to Streptococcus mutans American Type Culture Collection (ATCC) for 5 days. For the tensile strength test, samples were sectioned into 1-mm-thick slices and submitted to a constant load of 0.5 mm/min in a universal testing machine. Fractured surfaces were analyzed and characterized as adhesive, cohesive, or mixed. The microleakage test was performed with silver nitrate solution.

RESULTS

In experimental groups, the tensile test revealed a statistically significant difference between the one- (18.59 ± 5.3) and three-layer (11.28 ± 5.0) groups (p < 0.001; ANOVA and Tukey's test). The adhesive failure mode was slightly more frequent in the one- (60%) and three-layer (80%) adhesive application groups. On the other hand, the microleakage levels of all experimental groups were statistically similar (Kruskal-Wallis; p > 0.05).

CONCLUSION

The experimental conditions influenced tensile properties and failure modes of different adhesive interfaces; however, they did not influence microleakage.

A three-species biofilm model for the evaluation of enamel and dentin demineralization

Although Streptococcus mutans biofilms have been useful for evaluating the cariogenic potential of dietary carbohydrates and the effects of fluoride on dental demineralization, a more appropriate biofilm should be developed to demonstrate the influence of other oral bacteria on cariogenic biofilms. This study describes the development and validation of a three-species biofilm model comprising Streptococcus mutans, Actinomyces naeslundii, and Streptococcus gordonii for the evaluation of enamel and dentin demineralization after cariogenic challenges and fluoride exposure. Single- or three-species biofilms were developed on dental substrata for 96 h, and biofilms were exposed to feast and famine episodes. The three-species biofilm model produced a large biomass, mostly comprising S. mutans (41%) and S. gordonii (44%), and produced significant demineralization in the dental substrata, although enamel demineralization was decreased by fluoride treatment. The findings indicate that the three-species biofilm model may be useful for evaluating the cariogenic potential of dietary carbohydrates other than sucrose and determining the effects of fluoride on dental substrata.

Plasma deactivation of oral bacteria seeded on hydroxyapatite disks as tooth enamel analogue

PURPOSE

To study the plasma treatment effects on deactivation of oral bacteria seeded on a tooth enamel analogue.

METHODS

A non-thermal atmospheric pressure argon plasma brush was used to treat two different Gram-positive oral bacteria including Lactobacillus acidophilus (L. acidophilus) and Streptococcus mutans (S. mutans). The bacteria were seeded on hydroxyapatite (HA) disks used as tooth enamel analogue with three initial bacterial seeding concentrations: a low inoculum concentration between 2.1 x 10(8) and 2.4 x 10(8) cfu/mL, a medium inoculum concentration between 9.8x10(8) and 2.4 x 10(9) cfu/mL, and a high inoculum concentration between 1.7 x 10(10) and 3.5 x 10(10) cfu/mL. The bacterial survivability upon plasma exposure was examined in terms of plasma exposure time and oxygen addition into the plasmas. SEM was performed to examine bacterial morphological changes after plasma exposure.

RESULTS

The experimental data indicated that a 13-second plasma exposure time completely killed all the bacteria when initial bacterial seeding density on HA surfaces was less than 6.9 x 10(6) cfu/cm2 for L. acidophilus and 1.7 x 10(7) cfu/cm2 for S. mutans, which resulted from low initial seeding inoculum concentration between 2.1 x 10(8) and 2.4 x 10(8) cfu/mL. Plasma exposure of the bacteria at higher initial bacterial seeding density obtained with high initial seeding inoculum concentration, however, only resulted in approximately 1.5 to 2 log reduction and approximately 2 to 2.5 log reduction for L. acidophilus and S. mutans, respectively. It was also noted that oxygen addition into the argon plasma brush did not affect the plasma deactivation effectiveness. SEM images showed that plasma deactivation mainly occurred with the top layer bacteria, while shadowing effects from the resulting bacterial debris reduced the plasma deactivation of the underlying bacteria.

In situ assessment of effects of the bromide- and fluoride-incorporating adhesive systems on biofilm and secondary caries

AIM

This in situ study assessed the effects of adhesive systems containing or not fluoride and/or the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on the microbiological composition of dental biofilm and enamel demineralization.

MATERIALS AND METHODS

During two phases of 14 days, ten volunteers wore intraoral palatal appliances containing two slabs of human enamel according to a double-blind, crossover design. The slabs were randomly restored using a composite resin and one of the following adhesive systems: All-Bond SE(TM) (self-etch, fluoride/MDPB free adhesive, AB) and Clearfl Protect Bond (self-etch containing fluoride and MDPB adhesive, CB). The biofilm formed on the slabs was analyzed with regard to total and mutans streptococci and lactobacilli counts. Demineralization represented by integrated area of hardness × lesion depth Delta S ( ΔS) was determined on enamel by analysis of cross-sectional microhardness, at 20 and 70 μm from the restoration margin. Data were analyzed by ANOVA.

RESULTS

No statistically significant difference was found either in enamel demineralization or in the microbiological composition of dental biofilm.

CONCLUSION

All adhesive systems containing or not fluoride and/or MDPB tested were unable to inhibit secondary caries in the in situ model used in the present research.

[Effects of hydrogen peroxide-containing bleaching on the growth of Streptococcus mutans biofilm on enamel disc surface]

OBJECTIVE

To evaluate the effects of a commercial bleaching agent containing 35% (mass fraction) hydrogen peroxide on the growth of Streptococcus mutans biofilm on enamel disc surface.

METHODS

A total of 20 enamel disks were made from human extracted teeth and the enamel surfaces were kept intact. The discs were autocalved and randomly divided into two groups: bleaching group and control group. Each group contained 10 discs. For bleaching group, the enamel discs were whitened by commercial 35% hydrogen peroxide according to the instruction (Beyond(TM) Professional Dental Whitening Kit, Beyond Technology, TX,USA ); no treatment for control group. All the discs were kept in sterile human saliva for 3.5 hours, and then the mixture of brain heart infusion broth (BHI) medium and Streptococcus mutans were added. The discs and Streptococcus mutans were incubated together in BHI medium with 5% CO(2) (volume fraction), at 37 °C. After 3, 7, 14, 21 and 28 d's incubation, two discs of each group were taken out and the biofilms on the enamel surfaces were evaluated by using conventional bacteria counts and confocal laser scanning microscope (CLSM). The bacteria in the biofilm on one disc enamel surface were analyzed by plating on BHIS agar and the colony-forming units were counted. The biofilm on the other disc surface was stained using a two-colour fluorescent dye kit (Bacerial Viability Kit L-7012) for CLSM.

RESULTS

The vital bacteria counts of vital cells in the 3, 7, and 14 d's biofilms of the bleaching group were significantly fewer than those of the control group. Especially in the 3 days' biofilm on the whitened surface, the vital bacteria counts [(3 595 ± 2 903) μm(2) vs. (89 155 ± 65 963) μm(2),t = 8.71,P = 0.00] and proportion of vital bacteria [(26.0% ± 16.4%) vs.(92.2% ± 10.9%), t = 19.93, P = 0.00] were significantly fewer than those of the control. While, for the 21d's biofilm, the vital bacteria counts and the percentage of the vital cells of the bleaching group were more than those of the control group significantly [(66 262 ± 23 772) μm(2) vs. (51 184 ± 20 502) μm(2), t = 2.59, P = 0.012].

CONCLUSION

The hydrogen peroxide-containing bleaching agent may inhibit the growth of Streptococcus mutans biofilm for about 3 weeks; but after 3 weeks, it seems that the bleached surface will increase the growth of biofilm. Whether the whitening therapy will increase caries susceptibility of the bleached surface needs further research.

Influence of MDPB-containing primer on Streptococcus mutans biofilm formation in simulated Class I restorations

PURPOSE

To evaluate the activity of a methacryloyloxydodecylpyridinium bromide (MDPB)-containing self-etching primer (Clearfil Protect Bond) against Streptococcus mutans and its ability to reduce biofilm formation on standardized experimental Class I restorations in vitro.

MATERIALS AND METHODS

Forty experimental Class I round restorations were prepared on enamel-dentin slabs using different adhesive strategies: group 1 = MDPB-containing adhesive system (Clearfil Protect Bond); group 2 = MDPB-free self-etching adhesive system (Clearfil SE Bond); group 3: MDPB-containing self-etching primer in combination with a fluoride-free bonding agent; group 4: MDPB-free self-etching primer in combination with a fluoride-containing bonding agent; group 5: a three-step etch-and-rinse adhesive system (Adper Scotchbond Multi Purpose). A Streptococcus mutans biofilm was grown for 48 h on the restoration surfaces and subsequently evaluated using scanning electron microscopy on three different areas: enamel, composite, and interface surfaces. Statistical analysis was performed by multiple ANOVA after data transformation.

RESULTS

Specimens in groups 2, 4 and 5 showed greater biofilm formation than those in groups 1 and 3 (p < 0.001) on all investigated substrates (enamel, composite, and interface areas).

CONCLUSIONS

Specimens prepared with an MDPB-containing primer exhibited significant decreases in biofilm formation on Class I restorations in vitro. Further in vitro and in vivo studies are required to clarify the role of quaternary ammonium compounds in reducing bacterial biofilm formation on restoration surfaces.

Cariogenicity of different commercially available bovine milk types in a biofilm caries model

PURPOSE

This study's purpose was to assess the cariogenicity of commercial bovine milk types in an experimental biofilm/caries model.

METHODS

Enamel and dentin slabs were used to grow biofilms of Streptococcus mutans UA159. Slabs/biofilms were exposed three times per day to commercial skim, semi-skim, whole, whole lactose-free, and whole with 10 percent sucrose-added bovine milk and to 10 percent sucrose and 0.9 percent sodium chloride as positive and negative caries-control, respectively. Biofilms were analyzed for bacterial counts, biomass, proteins, and polysaccharide production. Slab's demineralization was assessed by loss of surface microhardness and the biofilm acidogenicity by medium pH.

RESULTS

Only whole and whole lactose-free milk kept pH above the demineralization threshold, inducing the lowest demineralization in both enamel and dentin (P<.05). Skim and semi-skim milk induced similar demineralization to the sucrose control, albeit slightly lower for semi-skim milk (P<.05). Whole and whole lactose-free milk produced lower biomass and less insoluble polysaccharides than the other treatments in enamel and dentin (P<.05). Adding 10 percent sucrose to whole milk turned it as cariogenic as 10 percent sucrose solution.

CONCLUSION

Bovine whole milk seemed less cariogenic than sucrose and the other commercial milk types, but not anticariogenic. Fat content in milk seemed to reduce cariogenicity of the fluid.

Biochemical and microbiological characteristics of in situ biofilm formed on materials containing fluoride or amorphous calcium phosphate

PURPOSE

To evaluate the biochemical and microbiological characteristics of in situ biofilm formed on materials that release fluoride (F-) or calcium (Ca++) and phosphate (Pi).

METHODS

This study comprised an in situ and in vitro experiment, utilizing three materials [Auralay XF and Fuji IX GP, containing fluoride, and Aegis containing amorphous calcium phosphate (ACP)] and bovine dental enamel slabs. For the in situ: 10 volunteers wore palatal devices, each containing four material specimens or enamel slabs that were treated with 20% sucrose solution. The biofilm had pH measurements on Day 7 and the composition was analyzed on Day 8 by assessing the following: F-, Ca++, Pi and insoluble extracellular polysaccharides (EPS) concentrations, and then identification of the microbiota. For the in vitro: materials/enamel were subjected to a 7-day pH-cycling regimen to determine F, Ca++ and Pi release.

RESULTS

The biofilm formed on F(-)-releasing materials was richer in F, Ca++ and Pi and had lower mutans streptococci counts than enamel biofilm. The biofilm on the ACP-containing material exhibited similar Ca++ and Pi concentrations to biofilm on F(-)-releasing materials. The materials showed buffering action compared with enamel. Biochemical and microbiological characteristics showed a less cariogenic biofilm on materials containing fluoride or amorphous calcium phosphate.

[The effects of topical fluoridation of enamel on the growth of cariogenic bacteria contained in the dental plaque]

INTRODUCTION

Dental caries is a bacterial disease. The most important element used in caries prevention is fluoride, which is derived from the air, diet or fluoride-containing preparations and materials, e.g. glass-ionomer restorations. Fluoride can inhibit metabolism and bacterial growth in the dental plaque. The aim of the study was to evaluate the effect of topical fluoridation of the enamel on the growth of Lactobacillus spp. in the dental plaque.

METHODS

The study was carried out in 15 patients with good oral hygiene, in whom three-day dental plaque from the enamel was examined. Next, fluoride was rubbed on the same surface and the examination of three-day dental plaque was repeated.

RESULTS

No statistically significant differences (p = 0.475) in the amounts of Lactobacillus spp. in the plaque collected prior to and after the topical fluoridation were revealed.

CONCLUSIONS

Fluoride rubbed in the enamel, did not affect the amount of Lactobacillus spp. in the dental plaque growing on this material.

Effect of bovine milk on Streptococcus mutans biofilm cariogenic properties and enamel and dentin demineralization

PURPOSE

The purpose of this study was to evaluate the effect of whole bovine milk on Streptococcus mutans biofilms and on demineralization of enamel and root dentin.

METHODS

S mutans UA159 biofilms were cultured on enamel and dentin bovine slabs of known surface hardness (SH) and exposed (8x/day) to 10% sucrose (positive control), whole bovine milk, and 4.5% lactose. Biofilm acidogenicity was estimated by medium pH (2x/day). After 4 days for dentin and 5 days for enamel, biofilms were collected to obtain biomass, viable bacteria, total protein, and intra- and extracellular polysaccharides. Final SH was measured on the slabs. Demineralization was calculated as percentage of SH loss (%SHL). Differences were determined by analysis of variance and Tukey's test (P<.05).

RESULTS

Biofilms formed on both substrates under 10% sucrose showed higher acidogenicity, biomass, protein concentration, insoluble polysaccharides, and %SHL than those treated with milk or lactose (P<.05), which did not differ in any parameter (P>.05). Higher bacterial counts were obtained from biofilms treated with milk on enamel, but not on dentin. Dentin was significantly more demineralized by milk than enamel (P<.05).

CONCLUSIONS

Although bovine milk appears to be less cariogenic than sucrose, this dairy product should not be considered caries-safe.

Molecular approaches for viable bacterial population and transcriptional analyses in a rodent model of dental caries

Culturing methods are the primary approach for microbiological analysis of plaque biofilms in rodent models of dental caries. In this study, we developed strategies for the isolation of DNA and RNA from plaque biofilms formed in vivo to analyse the viable bacterial population and gene expression. Plaque biofilm samples from rats were treated with propidium monoazide to isolate DNA from viable cells, and the purified DNA was used to quantify total bacteria and the Streptococcus mutans population via quantitative polymerase chain reaction (qPCR) and specific primers; the same samples were also analysed by counting colony-forming units (CFU). In parallel, RNA was isolated from plaque-biofilm samples (from the same animals) and used for transcriptional analyses via reverse transcription-qPCR. The viable populations of both S. mutans and total bacteria assessed by qPCR were positively correlated with the CFU data (P < 0.001; r > 0.8). However, the qPCR data showed higher bacterial cell counts, particularly for total bacteria (vs. CFU). Moreover, S. mutans proportion in the plaque biofilm determined by qPCR analysis showed strong correlation with incidence of smooth-surface caries (P = 0.0022, r = 0.71). The purified RNAs presented high RNA integrity numbers (> 7), which allowed measurement of the expression of genes that are critical for S. mutans virulence (e.g. gtfB and gtfC). Our data show that the viable microbial population and the gene expression can be analysed simultaneously, providing a global assessment of the infectious aspect of dental caries. Our approach could enhance the value of the current rodent model in further understanding the pathophysiology of this disease and facilitating the exploration of novel anti-caries therapies.

Laboratory evaluation of extrinsic stain removal by a specially engineered sonic powered toothbrush with unique sensing and control technologies

OBJECTIVE

The purpose of this laboratory study was to evaluate extrinsic stain removal from teeth by a specially engineered sonic powered toothbrush with unique sensing and control technologies, using the Triple Clean and the Sensitive refill brush heads, in comparison to a manual flat-trim toothbrush.

METHODS

Twelve (12) artificially stained bovine teeth were tested with each product. The percentage of stain removed by each product was calculated by taking the ratio of the amount of stain removed by brushing for 800 strokes to the total amount of stain removed by subsequent application of a dental prophylaxis. The stain was quantified by measuring the light reflected by the stained teeth with a spectrophotometer. Data were reported as L*, lightness of the stain, and as W*, a whiteness index comprising the lightness, hue, and chroma of reflected light. Statistical analyses were performed separately for the AL* and AW* scores. Comparisons of the toothbrushes with respect to baseline-adjusted deltaL* and deltaW* scores were performed using an analysis of covariance (ANCOVA). Post-ANCOVA pair-wise comparisons of the study toothbrushes were performed using Tukey's test for multiple comparisons. All statistical tests of hypotheses were two-sided, and employed a minimum level of significance of 0.05.

RESULTS

The percentage of stain removed by the sonic powered toothbrush, using either the Triple Clean brush head or the Sensitive brush head under laboratory test conditions, is superior (p < 0.05) to the percentage of stain removed by the manual flat-trim toothbrush when analyzed for both the deltaL* and deltaW* scores. The mean percentage of stain removed was 62.10 for the power toothbrush with the Triple Clean brush head, 49.01 for the power toothbrush with the Sensitive brush head, and 30.56 for the manual flat-trim toothbrush when calculated using deltaL* scores. The mean percentage of stain removed was 59.89 for the power toothbrush with the Triple Clean brush head, 46.83 for the power toothbrush with the Sensitive brush head, and 29.25 for the manual flat-trim toothbrush when calculated using deltaW* scores.

CONCLUSIONS

This new specially engineered sonic powered toothbrush with unique sensing and control technologies effectively removes extrinsic stains from the surface of teeth under laboratory test conditions with both the Triple Clean and the Sensitive brush heads. The effectiveness of stain removal with either brush head is significantly greater than the effectiveness of stain removal of a manual flat-trim toothbrush under these conditions.

[The effects of Ketac Molar Aplicap glass-ionomer material on growth of cariogenic bacteria contained in the dental plaque]

INTRODUCTION

In the aging population, the prevalence of root caries has been observed, which is a characteristic feature of the elderly people. The most important element used in caries prevention is fluoride, which is derived from the air, diet or fluoride-containing preparations and materials, e.g. glass-ionomer restorations. The aim of the study was to evaluate the effect of Ketac Molar Aplicap glass-ionomer on the growth of Lactobacillus sp. bacteria, one of the species most frequently found in the carietic focus of the tooth root.

METHODS

The study was carried out in 15 patients with good oral hygiene, in whom 35 fillings from Ketac Molar Aplicap conventional glass-ionomer material were performed. After 6 months, three-day dental plaque from these fillings and from the tooth enamel of the control group was examined.

RESULTS

No statistically significant differences (p = 0.554) in the amounts of Lactobacillus sp. between the study and control group were revealed.

CONCLUSIONS

Lack of inhibiting effect of glass-ionomer material on the growth of the dental plaque with Lactobacillus sp. after the time of observation is implied.

Determinants of enamel decalcification during simulated orthodontic treatment

OBJECTIVE

To determine the relative effects that phosphoric acid etching, metal brackets, composite resin adhesives, and filled resin sealants have on enamel decalcification.

MATERIALS AND METHODS

One hundred and fifty teeth were randomly divided into six groups to test the effects of acid etching, brackets, and a composite resin adhesive. The right side of each tooth was sealed. The teeth were submitted to a simulated carious challenge by Streptococcus mutans in a nutritive media for 42 days. Scanning electron photomicrographs (SEMs) were used to qualitatively evaluate the tooth surfaces. DIAGNOdent laser fluorescence was used to quantify the decalcification changes that occurred.

RESULTS

SEMs showed normal enamel on the control teeth, etching patterns on the acid-etched teeth, surface degradation on the teeth that had resin, and sealant tags on the sealed side. The untreated control group showed significantly less decalcification (P ≤ .05) than did all groups except the no etch+bracket group. The no etch+bracket group showed significantly less decalcification than did the etch+bracket, no etch+resin, and the etch+resin groups. Acid-etched teeth demonstrated significantly more decalcification (34%) than did those that were not etched. The teeth with resin showed significantly more decalcification (24%) than did those without resin. There was no significant difference between teeth that did and did not have brackets. The unsealed side of the teeth showed small amounts of--but significantly more--decalcification (5%) compared to the sealed side.

CONCLUSIONS

Acid etching and composite resin adhesives increase enamel decalcification in vitro, while brackets do not. Filled resin sealants protect the teeth from decalcification.

In-vitro evaluation and comparison of the anti-microbial potency of commercially available oral hygiene products against Streptococcus mutans

BACKGROUND

Dental caries is the destruction of enamel, dentin, or cementum of teeth due to bacterial activities, which if left untreated can cause considerable pain, discomfort, and treatment costs are very high. Of the oral bacteria, Streptococcus mutans is considered to be causative agent of dental caries in humans.

AIM

This study aims at screening the antibacterial potential of available oral hygiene products against S. mutans, the primary etiological agent.

MATERIALS AND METHODS

A selective number of toothpaste and mouth rinse available in the nearby local market was subjected to the study. The experiments were designed in a way to determine which one of these products had the greatest anti-S.mutans activity. Antibiotic sensitivity tests against the pathogenic strains were also conducted.

RESULTS AND DISCUSSION

Pathogenic strains of S.mutans were isolated from clinical dental specimen and identified using MTCC standard strain No. 890. Of the 86.66% samples which showed positive for S.mutans growth, almost 96% conferred sensitivity to 0.08 mg/ml of penicillin. Among the toothpastes used, A showed the maximum inhibitory activity against S.mutans inhibiting its growth even at a very low concentration of 0.0156 g/ml. Similar results were seen in the case of the mouth rinses used for the study, which showed that N had the most effective activity against S.mutans even at 1:8 dilution.

CONCLUSION

The oral hygiene products containing triclosan proved to be the most effective followed by those containing fluoride. Herbal products showed comparatively lesser activity in inhibiting the growth of S. mutans. Even though there are so many products available to curb the progression of dental caries in the population targeted, there is still an undoubted prevalence and incidence of caries among the general public. The need for a better alternative to help control dental caries is on the rise even today.

The CEJ: a biofilm and calculus trap

There is a direct correlation between increasing periodontal probing depth and increasing presence of residual biofilms and calculus. One of the more common areas to find postscaling and root-planing residual biofilm and calculus is the cemento-enamel junction (CEJ)--an area that in most cases is easily accessible. Yet few studies have addressed the question of why the CEJ is a potential biofilm and calculus trap. This article discusses the various anatomical relationships of enamel, dentin, and cementum at the CEJ, the role of CEJ anatomy in the retention of biofilm (with SEM photographs as supporting evidence), and the biological and clinical implications of subgingival residual biofilm and calculus.

Molar incisor hypomineralization. Morphological and chemical aspects, onset and possible etiological factors

OVERALL AIM: The general objective of this thesis was to enhance the understanding of Molar Incisor Hypomineralization (MIH) in areas of the histological, chemical and mechanical properties of the hypomineralized enamel, objective and subjective clinical symptoms in relation to bacteria findings. Further, to estimate a time for onset of the disturbance and investigate possible etiological factors.

MATERIAL & METHODS

22 teeth diagnosed with MIH were used in the histological and chemical studies. A number of analytical methods were used; Light microscopy, Polarized light microscopy, Scanning electron microscopy, X-ray microanalysis, Vickers hardness test and X-ray Micro Computed Tomography. Decalcified sections were stained with bacterial staining. An ozone device was tested for the ability to kill strains of oral bacteria. In collaboration with the prospective ABIS study, 17.000 individuals were examined and possible etiological causes of severe demarcated opacities were tested.

RESULTS & CONCLUSIONS

The hypomineralized enamel was mainly located in the buccal enamel of the teeth and had a high degree of porosity extending from enamel-dentin-junction with a distinct border to the normal cervical enamel. Teeth diagnosed MIH had lower hardness values in hypomineralized enamel and differences in the chemical composition. Bacteria were observed in the enamel and deep into the dentin. Ozone treatment for 20 seconds or more was effective to kill oral microorganisms. Significant relations were found between MIH in first molars and breast feeding more than 6 months, late introduction to gruel and infant formula (later than 6 months). The onset for the hypomineralized enamel was estimated to around 200 days from start of the enamel mineralization.

DIAGNOdent measurements of cultures of selected oral bacteria and demineralized enamel

OBJECTIVE

Carious tissue fluoresces with a wavelength different from sound tissue when stimulated by light with a wavelength of 655 nm. This difference is thought to have a bacterial origin rather than indicating demineralization. This study aimed to measure fluorescence emitted by normal cultivable caries-associated bacterial flora and typical porphyrin-producing bacteria with DIAGNOdent, and to verify earlier findings that demineralization of the dental hard tissue does not affect DIAGNOdent readings.

MATERIAL AND METHODS

Bacterial samples were collected from five occlusal caries lesions in three subjects. From these, mixed anaerobic flora, Lactobacilli and mutans Streptococci were cultured in up to three different kinds of culture medium. Colonies of Lactobacilli and mutans Streptococci were also measured after transferring them to glass slides. Laboratory teaching strains of Prevotella spp., Porphyromonas gingivalis and Actinomyces odontolyticus were cultured anaerobically and fluorescence measured directly after an appropriate incubation period. Sound enamel surfaces of 15 extracted premolars were demineralized and changes in fluorescence measured.

RESULTS

DIAGNOdent readings > 20 were only obtained from young colonies of Prevotella and from colonies of mutans Streptococci cultured on mitis-salivarius-bacitracin agar. Higher measurements were obtained as the bacterial colonies aged. Lower measurements were obtained after transferring colonies to glass slides. Demineralization of enamel did not affect the DIAGNOdent measurements.

CONCLUSIONS

The change in fluorescence measured with DIAGNOdent has a bacterial origin rather than occurring as a result of demineralization. The measurements are presumably dependent on bacterial metabolites rather than bacteria themselves, and probably record synergistic effects during the carious process rather than the quantity or species of bacteria involved.

[The antimicrobial efficacy of an erbium laser on Streptococcus mutans. In vivo study]

This study was conducted in order to demonstrate the bactericidal effect of an erbium laser (Er,Cr:YSGG) on Streptococcus mutans, in vivo, at different laser power settings, obtaining sterile enamel surfaces with minimal tissue ablation. The practicians use the laser for the cutting effect on hard tissue to eliminate all the infected and affected enamel and dentine, without collateral damage on the pulp and for its bactericidal effect on cariogenic bacteria.

MATERIAL AND METHOD

The study group included 132 superficial carious lesions, on 66 patients with ages between 6 and 20; a two-year study (January 2006 - November 2008) performed in a private practice. The carious lesions were ablated with an erbium laser with two types of tips. A sample of occlusal plaque was taken using a sterile swab, soaked in normal saline solution (before and after the preparation).

RESULTS

Before the laser treatment, the percentage with high counts of Streptococcus mutans was 70% and low counts 30% (chi2 = 26.16 ; p < 0.01). At the laser power of 4,5 watts, the zirconium tip (Z6) had a higher number of sterile culture (96,3%). The numbers of sterile cultures were higher at the laser power of 5 watts, with both tips: zirconium and sapphire, the percentage being equal: 91-92%.

Unique functions of hydroxyapatite with mutans streptococci adherence

OBJECTIVE

Hydroxyapatite (HA) is used as a construction material for artificial supplementation of enamel tooth surfaces to improve oral hygiene. This study examined in vitro HA interactions with mutans streptococci (MS) and bacterial adherence to small (nanosize) crystal form of HA beads having a protean hexagonal structure. The adsorption and physical effects of HA employed in vivo is also described.

METHOD AND MATERIALS

[3H-thymidine]-labeled streptococci were incubated with HA noncoated or coated with salivary components or salivary agglutinin peptide (SRCRP2), a receptor for streptococcal surface proteins. Bacterial adhesion activities on HA were measured by uptake of [3H-thymidine]. Application of HA paste in an individual tray was tried on the tooth surface, and its effects on the colony ratio of MS/total streptococci (TS) in saliva were analyzed by culture technique.

RESULTS

The adhesion assay showed that the binding of streptococci to HA was inhibited by coating with salivary components, whereas coating with SRCRP2 had nearly no influence on binding with or without Ca+. Further, treatment with HA decreased the adherence of Streptococci mutans to roughened enamel surfaces by one-third. In vivo application of a HA dentifrice to individual teeth demonstrated that the colony number ratio of MS/TS slowly decreased.

CONCLUSION

MS adhesion to HA was restricted by both salivary components, except for SRCRP2, and the physical effects of HA; in addition, the material itself has a unique effect for removing MS from the oral cavity.

[Helicobacter pylori in the development of dental caries]

It is shown, that in patients with erosive and ulcer defects of gastroduodenal zone at settling Helicobacter pylori (Hp) in an oral cavity in 100% of cases caries develops at intensity 13.6 +/- 1.4 teeth. Produced Hp protease and ammonia cause disintegration connected to protein silica acids and reduce activity lysocim, worsening, thus, fluid and protective properties of a saliva. In the subsequent infringement of autopurification of a teeth results in accumulation of a dental strike where protease activity conditionally pathogenic microflora conducts to depolymerization and demineralization enamels of a teeth.

Polyphenolic beverages reduce initial bacterial adherence to enamel in situ

OBJECTIVES

Polyphenols are antibacterial and anti-oxidative natural agents. The present in situ study aimed to investigate the effect of different polyphenolic beverages on initial bacterial adherence to enamel in the oral cavity.

METHODS

Initial biofilm formation was performed on bovine enamel specimens mounted buccally on individual upper jaw splints and carried by six subjects. After 1 min of pellicle formation, oral rinses with black tea, green tea, grape juice, Cistus tea or red wine were performed for 10 min. Afterwards the slabs were carried for another 19 or 109 min, respectively. Samples exposed to the oral fluids for 30 and 120 min served as controls. Following intraoral exposure, the slabs were rinsed with saline solution. The amount of adherent bacteria was determined with DAPI-staining (4',6-diamidino-2-phenylindole) and with fluorescence-in situ hybridization (FISH) of eubacteria and streptococci.

RESULTS

Rinses with all beverages reduced the amount of detectable bacteria. Lowest number of adherent bacteria was found following rinses with red wine, Cistus tea and black tea as measured with DAPI (up to 66% reduction of adherent bacteria vs. controls). Also FISH revealed significant impact of most tested beverages.

CONCLUSIONS

Rinses with certain polyphenolic beverages as well as consumption of these foodstuffs may contribute to prevention of biofilm induced diseases in the oral cavity.

In vitro antibacterial activity of adhesive systems on Streptococcus mutans

PURPOSE

To evaluate the antibacterial activity of three adhesive systems -- Prime & Bond 2.1 (PB), Clearfil SE Bond (CS) and One Up Bond F (OU) -- on Streptococcus mutans in vitro.

MATERIALS AND METHODS

Adherence and agar disk-diffusion tests were performed. For the adherence testing, 40 human enamel specimens (4 mm2) were sterilized and the adhesive sytems were applied (n = 10). The control group did not receive the application of any adhesive system. Specimens were immersed in brain heart infusion broth (BHI) inoculated with S. mutans standardized suspension (10(6) cells/ml) for 48 h at 37 degrees C and 5% CO2. The number of S. mutans cells adhered to each specimen was evaluated by the plating method on BHI agar. For agar disk-diffusion testing, adhesive disks and disks soaked in distilled water (negative control) or 0.2% chlorexidine (positive control) were incubated with S. mutans for 48 h. The diameters of the zones of bacterial inhibition were measured. Adherence data were transformed in logarithms of base 10 (log10). Data were submitted to Kruskal-Wallis and Student-Neuman-Keuls tests at the 5% level of significance.

RESULTS

The results of the adherence test showed that One Up Bond F (OU) and Clearfil SE Bond (CS) did not differ significantly from one another, but allowed significantly less adherence than Prime & Bond 2.1 (PB) and control [mean log10 (standard deviation) values: PB 6.10 (0.19); CS primer 4.55 (0.98); OU 4.65 (0.54); control group 6.34 (0.27)]. The disk-diffusion test showed no significant difference between OU (diameter in mm: 3.02 +/- 0.13) and CS (3.0 +/- 0.12), but both were significantly more effective in inhibiting bacterial growth than PB (1.0 +/- 0.10).

CONCLUSION

The self-etching systems Clearfil SE Bond and One Up Bond F presented a greater inhibitory effect against S. mutans, also in terms of adherence, than did the conventional system, Prime & Bond 2.1.

Multi-species biofilm formation on dental materials and an adhesive patch

PURPOSE

This laboratory study assessed the influence of surface roughness and contact time on the formation of a multi-species biofilm on dental materials (adhesive patch, composite, amalgam and enamel).

MATERIALS AND METHODS

Rough and smooth specimens of each material were prepared and the mean surface roughness was assessed profilometrically. The biofilms were then allowed to grow either for 15 min or 15 h respectively on saliva-preconditioned specimens of each material, and colony-forming units on blood agar were counted (N = 9/group) Surface morphology was assessed using a scanning electron microscope.

RESULTS

No difference was found in the biofilm formation rate among all the materials that were tested. After a short incubation period, a statistical significant difference between smooth and rough samples could be detected on amalgam and on the resin composite material (P < or = 0.001).

CONCLUSIONS

Surface roughness may influence the initial biofilm adherence, but differences vanish following growth and maturation. The multi-species biofilm offers a reliable laboratory model for studying plaque formation.

Adherence of Streptococcus mutans to uncoated and saliva-coated glass-ceramics and composites

This study sought to investigate the surface roughness and the S ence of Streptococcus mutans (in the presence and absence of saliva) to ceramics and composites. The early dental biofilms formed in situ on the materials were illustrated, using scanning electron ascopy (SEM). Feldspathic and leucite/feldspathic ceramics and microhybrid and microfilled composites were evaluated. Human dental enamel was used as the control. Standardized specimens of the miaterials were produced and surface roughness was analyzed. The dhesion tests were carried out in 24-well plates and colony forming units (CFU/mL) were evaluated. Values of roughness (microm) ,adherence (CFU/mL) were analyzed statistically. Of all the surfaces tested, enamel was the roughest. Leucite/feldspathic ceramics were rougher than the feldspathic ceramic, while composites were similar statistically. Enamel offered the highest level of adherence to uncoated and saliva-coated specimens, while the leucite/feldspathic ceramic demonstrated greater adherence than the feldspathic ceramic and the composites were similar statically. The rougher restorative materials increased the adherence of S. mutans on the material surfaces.

Short-term evaluation of resin sealing and rebonding on amalgam microleakage: an SEM observation

AIMS

The aim of this study was to evaluate the effect of two different sealing agents on the microleakage of Class V amalgam restorations with and without resin rebonding.

METHODS AND MATERIALS

Sixty extracted premolars were divided into six groups with ten teeth in each group. Class V cavity preparations were prepared on the facial surfaces of each tooth with the coronal margins placed in enamel and apical margins in cementum (dentin). The preparations in three groups were treated with Copalite, Scotchbond Multi-Purpose (SBMP), and no sealing agent, respectively. The other three groups received the same sealing agents in conjunction with a rebonding process. This arrangement of specimens provided for a comparison of the groups with and without a rebonding procedure. Amalgam was used as the restorative material. Specimens were thermocycled, stained, and sectioned. Microleakage was graded (0-3) using a stereomicroscope at 40x magnification. A scanning electron microscope (SEM) was used along with a high resolution elemental analysis. Data were analyzed with Kruskal-Wallis, Mann-Withney, and Wilcoxon pair wise statistical tests (alpha=.05).

RESULTS

The bonded amalgam groups demonstrated significantly less microleakage, whereas the unsealed groups showed the highest microleakage (P=0.001). A significant difference between the mean rank of the microleakage of enamel and dentin margins was observed (P=0.037). Insignificant, lower microleakage was observed in groups receiving a rebonding procedure (P=0.085).

CONCLUSION

Copalite and a multi-step adhesive system had a significant effect on microleakage of Class V amalgam restorations. The influence of the multi-step adhesive system was significantly greater than Copalite. The rebonding of the amalgam restorations did not have a significant effect on microleakage.