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.

Effects of sonic energy on monospecific biofilms of cariogenic microorganisms.

PURPOSE: To evaluate the in vitro differential effect of sonic energy, delivered by Sonicare Advance, on cariogenic and non-cariogenic bacteria biofilms. METHODS: A wild strain of Streptococcus mutans, Lactobacillus acidophilus, Streptococcus salivarius and Veillonella alcalescens was isolated from human dental plaque. For each of the four microorganisms a biofilm adherent to bovine enamel disks, coated with artificial saliva, was obtained. Biofilms were divided into four groups and were exposed to acoustic energy delivered by Sonicare for 0 (control group), 5, 15 and 30 seconds. The distance between the end of the bristles and the disk surface was set to 7 mm, to ensure that the biofilm removal was simply due to fluid forces and not to the contact with the bristle tips during the brushing cycle. A colorimetric technique (MTT assay), based on the reduction of a yellow tetrazolium salt to a purple formazan, was used to evaluate the reduction of the adherent biomass after the exposure to the sonic energy. RESULTS: ANOVA results showed that sonic energy exposure significantly reduced the biomass of S. mutans and S. salivarius adherent to the disks, while L. acidophilus and V. alcalescens seemed to remain basically unaffected. In the two streptococcal groups, the increase of the exposure time led to different reduction trends; while S. salivarius exhibited a progressive decrease over time, S. mutans showed a rapid reduction of the adherent biomass after a 15-second exposure to Sonicare.

Influence of different adhesive restorative materials on mutans streptococci colonization.

PURPOSE: To evaluate the effect of some restorative materials on mutans streptococci colonization. METHODS: Awild strain of mutans streptococci was isolated from human dental plaque and a monospecific biofilm adherent to the surfaces of 12 adhesive restorative materials (F2000, Dyract AP, Compoglass F, Z100 MP, Filtek Z250, Clearfil, Ketac-Bond, Ketac-Fil Plus, Ketac-Molar, Fuji Cap II, Fuji Bond LC and Fuji II LC) were tested. A colorimetric technique (MTT assay), based on the reduction of a yellow tetrazolium salt to a purple formazan, was used to evaluate the biomass adherent to the disk surfaces after a 24-hour growth. RESULTS: One-way ANOVA showed that glass-ionomer cements (Fuji Cap II, Ketac-Bond, Ketac-Fil and Ketac-Molar) had similar antibacterial effects on mutans streptococci and were significantly more effective (P < 0.001) than all other products tested in reducing the biofilm development on their surfaces. The compomers (Dyract, Compoglass F and F 2000) showed a significantly higher value of bacterial colonization than all the other materials (P < 0.001).

Depth of cure efficacy of high-power curing devices vs traditional halogen lamps.

PURPOSE: To determine the depth of cure resulting from three different curing devices in a photoactivated microhybrid composite through high-performance liquid chromatography (HPLC) analysis of leachable monomers. MATERIALS AND METHODS: Three different curing units, a halogen lamp (Heliolux, Vivadent), a xenon lamp (Kreative Kuring, Allyn Welch), and a plasma-arc lamp (Apollo 95, DMDS) were investigated using a universal microhybrid composite (P 60, 3M) as the test material. To assess the effect of curing device variation, a flexural strength test was performed. In addition, samples of composite were prepared and cured "in contact" (0 mm between the sample surface and light-guide tip) and through a specific thickness of composite (1, 2, or 3 mm). The monomers (bis-GMA and UDMA) eluted from the samples were detected by HPLC. RESULTS: No significant differences were found in the mechanical properties of composite cured with different light sources. In contrast, the concentration of eluted monomers (bis-GMA, UDMA) at a depth of 2 mm and more was significantly higher for the specimens cured with the high-power curing devices than those cured with the traditional halogen lamp. CONCLUSION: Under these experimental conditions, high-power curing devices were shown to be inferior in the deep polymerization of resin composite when compared to a traditional halogen lamp.

Chlorhexidine concentration in saliva after topical treatment with an antibacterial dental varnish.

PURPOSE: To evaluate the salivary levels of chlorhexidine (CHX) after a single professional treatment with an antibacterial dental varnish (Cervitec) containing 1% CHX and 1% thymol. METHODS: Unstimulated whole saliva from 21 healthy young adults was collected at baseline and up to 24 hours after treatment at designated time intervals and the CHX levels in saliva were quantified with high-performance liquid chromatography. Post-treatment saliva samples were added to suspensions of mutans streptococci and supragingival dental plaque for a growth inhibition. RESULTS: CHX concentration in saliva showed a peak value (76.5 microg/ml) after 5 minutes followed by a slow decrease with time. The elevation was statistically significant (P < 0.05) up to 4 hours after the application of the varnish and the recorded values were back to baseline levels after 24 hours. The 2- and 4-hour post-treatment saliva samples inhibited growth of mutans streptococci by 46% and 33%, respectively.

The influence of light-curing time on the bacterial colonization of resin composite surfaces.

OBJECTIVES: Bacterial colonization of composite surfaces represents the main factor in the etiology of secondary caries around adhesive restorations. The authors' aim was to evaluate the influence of light-curing time on mutans streptococci colonization (MS) of a resin composite material. METHODS: Specimens obtained from a dental resin composite were divided into 12 groups and light-cured with the same light source respectively for 10, 20, 30, 40, 60 or 80 s using two different curing-power levels: 400 and 800 mW/cm2. A wild strain of MS was isolated and a 24-h-monospecific biofilm, adherent to the surfaces of the samples, was obtained. A colorimetric technique (MTT assay), based on the reduction of a yellow tetrazolium salt to a purple formazan, was used to evaluate the biomass adherent to the specimen surfaces. ANOVA and Scheffé's tests were used to statistically analyze the results. RESULTS: Two-way ANOVA demonstrated there was no interaction between curing-time factor and curing-power factor (p=0.970); one-way ANOVA was used to analyze separately the data obtained from each curing-power level. Both levels showed highly significant differences (p<0.0001) among the different curing time groups. The non-parametric test for trend showed in both levels the existence of a highly significant trend (p<0.0001) for bacterial colonization reduction as curing time increases. SIGNIFICANCE: A reduced curing time seems to be responsible for increased in vitro colonization of composite surfaces by MS; this phenomenon is likely to be related to the presence of unpolymerized monomers on the material surface.