The effect of dental restorative materials on dental biofilm

Adhesion of oral streptococci to all-ceramics dental restorative materials in vitro

In recent years, patients have benefited from the development of better and more esthetic materials, including all-ceramics dental restorative materials. Dental plaque formation on teeth and restorative materials plays an important role in the pathogenesis of oral diseases. This study investigates initial adhesion of stationary phase streptococcal species to different all-ceramics dental restorative materials. The saliva-coated materials were incubated with the bacteria for 1 h in an in vitro flow chamber which mimics environmental conditions in the oral cavity. Number and vitality of adhering bacteria were determined microscopically after staining. Surface roughness and the composition of the materials had no distinctive influence on bacterial adhesion. However, S. mutans and S. sobrinus adhered about tenfold less numerous to all materials than the other streptococcal species. Further, there was a correlation between bacterial vitality and materials' glass content. The results showed that early plaque formation was influenced predominantly by the presence of the salivary pellicle rather than by material dependent parameters whereas the composition of the all-ceramics appeared to have influenced the percentage of viable cells during the adhesion process. This presented in vitro technique may provide a useful model to study the influence of different parameters on adherence of oral streptococcal species.

Fluoride release for restorative materials and its effect on biofilm formation in natural saliva

This study investigated the influence of natural saliva of varying pH on surface biofilm formation of restorative materials and how this influenced fluoride release. Columnar specimens of glass ionomer cement (GIC), resin modified glass ionomer cement (RMGIC), compomer, giomer and composite, were prepared, matured for 24 h at 37 degrees C and 100% humidity, lapped and then placed in natural stimulated saliva with a pH of 3.8 or 7.1. Fluoride release was determined daily using an ion-selective electrode. The surfaces of selected specimens were observed using Confocal Laser Scanning Microscopy in conjunction with a fluorescent dye. The surface biofilm formation and bacterial growth was most dominant under neutral conditions and on the surfaces of GICs compared with other materials. GICs released significantly higher amounts of fluoride than other materials. The results suggest that the increased fluoride release of GICs did not reduce the amount of bacterial growth and biofilm formation on the surfaces of these materials when stored in natural saliva.

Adhesion of Streptococcus sanguinis to Dental Implant and Restorative Materials in vitro

Bacterial adhesion to tooth surfaces or dental materials starts immediately upon exposure to the oral environment. The aim of this study, therefore, was to compare the adhesion of Streptococcus sanguinis to saliva-coated human enamel and dental materials - during a one-hour period - using an in vitro flow chamber system which mimicked the oral cavity. After fluorescent staining, the number of adhered cells and their vitality were recorded. The dental materials used were: titanium (Rematitan M), gold (Neocast 3), ceramic (Vita Omega 900), and composite (Tetric Ceram). The number of adherent bacterial cells was higher on titanium, gold, and ceramic surfaces and lower on composite as compared to enamel. As for the percentage of adherent vital cells, it was higher on enamel than on the restorative materials tested. These results suggested that variations in the number and vitality of the adherent pioneer oral bacteria, S. sanguinis, in the in vitro system depended on the surface characteristics of the substratum and the acquired salivary pellicle. The in vitro adhesion model used herein provided a simple and reproducible approach to investigate the impact of surface-modified dental materials on bacterial adhesion and vitality.

In vitro biofilm formation on the surface of resin-based dentine adhesives

Prevention of root caries on exposed root surfaces in the aging population is a significant challenge. Bonding resins can be applied to exposed root surfaces as sealants; however, minimal data exists regarding biofilm formation on the surface of these resins. We hypothesized that an antibacterial dentine-bonding resin containing methacryloxydodecyl-pyridiniumbromide (MDPB) may reduce biofilm formation. Biofilms were produced in pooled stimulated natural whole saliva, supplemented with 1% sucrose, on the surface of 5 dentine-bonding resins (Clearfil SE, OptiBond Solo, Protect Bond, Protect Bond Primer, and Xeno III) using untreated root surfaces as controls. Biofilms were stained using the Live:Dead Baclight bacterial viability stain, viewed with confocal microscopy, and analyzed using ImageJ image-analysis software. Resin surfaces encouraged attachment of live bacteria compared with root surfaces. All resins showed similar bacterial colonization in sections adjacent to the resin surface, but in the central and outer portions of biofilms, Xeno III and Protect Bond Primer showed a viable bacterial load similar to that of the root surface. Fluoride-releasing resins (OptiBond Solo/Protect Bond) did not show reduced biofilm formation. Thus, antibacterial agents within the resins have a minimal effect on biofilm formation, particularly when directly adjacent to the root surface.

Early biofilm formation and the effects of antimicrobial agents on orthodontic bonding materials in a parallel plate flow chamber

Decalcification is a commonly recognized complication of orthodontic treatment with fixed appliances. A technology, based on a parallel plate flow chamber, was developed to investigate early biofilm formation of a strain of Streptococcus sanguis on the surface of four orthodontic bonding materials: glass ionomer cement (Ketac Cem), resin-modified glass ionomer cement (Fuji Ortho LC), chemically-cured composite resin (Concise) and light-cured composite resin (Transbond XT). S. sanguis was used as it is one of the primary colonizers of dental hard surfaces. Artificial saliva was supplied as a source of nutrients for the biofilms. The effects of two commercially available mouthrinses (i.e. a fluoride containing rinse and chlorhexidine) were evaluated. Initial colonization of the bacterium was assessed after 6 hours of growth by the percentage surface coverage (PSC) of the biofilm on the disc surfaces. There were statistically significant differences in bacterial accumulation between different bonding materials (P < 0.05), Concise being the least colonized and Transbond XT being the most colonized by S. sanguis biofilms. All materials pre-treated with 0.05 per cent sodium fluoride mouthrinse showed more than 50 per cent reduction in biofilm formation. The 0.2 per cent chlorhexidine gluconate mouthrinse caused significant reduction of biofilm formation on all materials except Ketac Cem. This in vitro study showed that the use of a chemically-cured composite resin (Concise) reduced early S. sanguis biofilm formation. Also, fluoride had a greater effect in reducing the PSC by S. sanguis biofilms than chlorhexidine. Rinsing with 0.05 per cent sodium fluoride prior to placement of orthodontic appliances is effective in reducing early biofilm formation.

Discoloration of dental resin composites after immersion in a series of organic and chemical solutions

The objective of this study was to evaluate the color change of dental resin composites following a series of immersion treatments, especially in organic substances. The color of four resin composites was measured according to the CIELAB color scale relative to the standard illuminant D65. Color was measured at baseline, and after sequential immersion in the following substances: Step 1, porcine-liver esterase (a substitute for a salivary esterase); Step 2, organic substances (mucin and serum) and phosphate-buffered saline (PBS) as a control; Step 3, chemical alteration agents [chlorhexidine (CH) and carbamide peroxide (CP)]; and Step 4, 2% methylene blue. Porcine-liver esterase caused color changes (DeltaE(ab) (*)) of 0.7-1.1 from the baseline. Organic substances caused color changes of 0.4-1.8 from the baseline, and color changes in organic substances were not significantly higher than those in PBS (p > 0.05), except for one composite. Combined treatment with mucin (or serum) with CH (or CP) did not produce significantly higher color changes compared to controls (p > 0.05). Mucin-treated composites showed generally lower methylene blue staining compared to serum and PBS groups. Although combined treatment of organic substances and chemical agents resulted in various discolorations of resin composites, chemical alteration of organic substances did not produce higher color change compared to PBS controls.

Effect of two antimicrobial agents on early in situ biofilm formation

OBJECTIVES

The aim of this observer-blind, controlled, three-cell cross-over study was to evaluate the influence of an amine fluoride/stannous fluoride (Meridol, 250 ppm; ASF) and a chlorhexidine mouthrinse (CHX; Chlorhexamed forte, 0.2%) compared with water on in situ biofilm growth.

MATERIAL AND METHODS

After a professional toothcleaning seven volunteers had to wear a special acrylic appliance, in which six specimens each were inserted to allow the build-up of intra-oral biofilms. The volunteers had to rinse twice daily for 1 min. with 10 ml of the allocated mouthrinse. After 48 h of wearing, the specimens with the adhering biofilms were removed from the splints and stained with two fluorescent dyes, which selectively stain vital bacteria green and dead bacteria red. Under the confocal laser scanning microscope biofilm thickness (BT) was evaluated. To examine bacterial vitality (BV%) the biofilms were scanned (1 microm sections) and digital images were made. An image analysis program was used to calculate the mean BV as well as the BV of the single sections. After a wash-out period of 14 days a new test cycle was started.

RESULTS

The use of CHX and ASF resulted in a BT of 8.4+/-4.4 mum and 15.7+/-9.9 compared with 76.7+/-29.4 mum using water. The mean vitality (in %) was reduced from 66.1+/-20.4 to 23.3+/-11.6 and 23.9+/-12.4 using CHX and ASF, respectively. Both active solutions reduced BT and BV significantly compared with water (p<0.001). Differences between the two active solutions were not significant (p>0.05).

CONCLUSION

Both mouthrinses showed antibacterial and plaque-reducing properties against the in situ biofilm. The study design enables the examination of an undisturbed oral biofilm and for the first time shows the influence of antibacterial components applied under clinical conditions regarding biofilm formation.

Evaluation of bacterial adhesion of Streptococcus mutans on dental restorative materials

Bacterial adhesion to the surface of composite resins and other dental restorative materials is an important parameter in the aetiology of secondary caries formation. The aim of the present study was to investigate the adhesion of a Streptococcus mutans strain (ATCC 25175) on the surface of different restorative materials. The test materials examined included three flowable composites (Filtek Flow, Tetric Flow, and Arabesk Flow), three microhybrid composites (Clearfil APX, Solitaire 2, and Z250), two glass-ionomers (Fuji IX, Fuji IX fast), a compomer (F2000), an ormocer (Admira), and a control reference material (tissue culture grade, surface treated polystyrene). The adhesion tests were carried out in 24-well plates. Quantitative turbidimetric measurements were finally performed in order to indirectly evaluate the amount of bacteria retained on the material surface after in vitro exposure to the bacteria suspension. Under these conditions, with the exception of the Admira ormocer and the Fuji IX fast glass ionomer, which were found to be more adhesive, all the other material surfaces showed a similar susceptibility to bacterial adhesion, exhibiting values not significantly different than the reference polystyrene control. Furthermore, the release of fluoride from some of the test surfaces did not appear capable to reduce early bacterial adhesion.

Individual vitality pattern of in situ dental biofilms at different locations in the oral cavity

The aim of the study was to examine the three-dimensional vitality structure of dental biofilms grown simultaneously at different locations in the oral cavity over a 48-hour period. Eight healthy volunteers wore special acrylic appliances. On each buccal side of the upper and the lower jaw three glass slabs were inserted, allowing for growth of a biofilm mimicking approximal plaque. After 48 h, the specimens were removed and biofilms were stained using two fluorescent dyes which selectively stain vital bacteria green and dead bacteria red. Under the confocal laser scanning microscope optical sections of 1 microm throughout the biofilm were made. To assess the vitality values (proportion of vital bacteria) of the whole biofilm as well as the vitality distribution in the different plaque sections an image analysis program was used. Plaque from the different locations revealed mean vitality values between 64.4 and 75.7% in the upper jaw and between 64.3 and 76.8% in the lower jaw, which were not statistically different. However, a great variation of the vitality values for the different layers and among the 8 subjects was found. Nevertheless, the analysis of the data of each single volunteer revealed a very similar vitality pattern in all twelve locations.