Inhibition of root caries progression by an antibacterial adhesive

A dentin primer containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) has been shown to penetrate and kill the bacteria in artificially demineralized dentin. We hypothesized that an experimental adhesive system, which incorporates the MDPB-containing primer, would be effective in inhibiting the progression of root caries in vitro. Artificial caries lesions were prepared by either an acid-gel or a Streptococcus mutans culture technique on the roots of extracted human teeth. The progression of these lesions after the application of the experimental or proprietary adhesive system was examined. Further demineralization was completely prevented by the experimental adhesive system, while lesions managed with the proprietary materials showed limited ability to inhibit further demineralization. We conclude that the experimental adhesive system can inhibit the progression of root-surface caries in vitro, through a combination of its antimicrobial activity and sealing of the demineralized dentin.     

In vitro antibacterial effects of the dentin primer of Clearfil Protect Bond.

OBJECTIVES: This study aimed to investigate the antibacterial effects of the dentin primer of a commercially available self-etching adhesive system, Clearfil Protect Bond, which contains antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB). METHODS: Inhibitory effects against Streptococcus mutans, Lactobacillus casei, or Actinomyces naeslundii were examined by an agar-disc diffusion method using the Clearfil Protect Bond primer containing 5% MDPB and an acidic adhesion-promoting monomer MDP, the primer only with MDP, and the primer with 1% cetylpyridinium chloride. The minimum inhibitory/bactericidal concentrations (MIC/MBC) of each primer for the three bacterial species were determined by serial microdilution assays. For testing the bactericidal effects seen in dentin, the primer was applied to demineralized dentin blocks in which S. mutans had been impregnated, and numbers of viable bacteria were counted. RESULTS: For all three bacteria, the sizes of the inhibition zones produced by Clearfil Protect Bond primer were significantly greater than for the other primers (p<0.05, ANOVA and Scheffe's F-test). The MIC/MBC values of Clearfil Protect Bond primer were less than those of the primer without MDPB, and comparable to those of the primer containing cetylpyridinium chloride. No bacterial recovery was obtained after application of Clearfil Protect Bond primer to the bacteria-impregnated dentin, although the primer without MDPB showed some bactericidal effect. SIGNIFICANCE: Clearfil Protect Bond primer has strong antibacterial activity based upon MDPB against S. mutans, L. casei and A. naeslundii, and the capability to disinfect cavities containing residual bacteria.     

A randomised trial comparing the antibacterial effects of dentine primers against bacteria in natural root caries

As people are living longer and retaining their teeth into old age, root caries is an increasingly significant problem. A minimally invasive treatment strategy, involving sealing the root caries lesion with an antibacterial resin sealant, could be highly beneficial. The aim of this study was to compare the antibacterial properties of the primers of two proprietary dentine bonding agents, Clearfil SE Bond (SE; Kuraray Medical, Japan) and Clearfil Protect Bond (PB; Kuraray Medical), which contains the antibacterial monomer methacryloyloxydodecylpyridinium bromide. Fifty-two root caries lesions were identified and randomly assigned to a primer. The lesion was cleaned, isolated, sampled with a sharp spoon excavator, a primer applied and a second sample taken. Samples were transported in fastidious anaerobe broth, vortex-dispersed and serial dilutions inoculated onto selective agars. Reduction in colony-forming units (CFU, %) after primer application was calculated for both primers for bacterial growth on each selective agar and compared to a hypothesised mean of 100% (one-sample t test, p < 0.05). No significant differences between primers were seen, indicating efficient bacterial elimination by both materials. Comparing percent reduction between SE and PB for each agar (Mann-Whitney test, p < 0.05), a significantly greater CFU reduction by PB was seen for streptococci but not other bacteria. More lesions exhibited bacterial growth and several lesions demonstrated marked bacterial growth after treatment with SE compared with PB. Therefore, PB appears to exhibit superior antimicrobial properties, particularly against streptococci. Both primers are highly antibacterial towards root caries bacteria and may therefore be suitable for minimally invasive treatment.     

Antibacterial activity and bonding characteristics of an adhesive resin containing antibacterial monomer MDPB.

OBJECTIVES: The aims of this study were to investigate the antibacterial activity of an adhesive resin incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) as well as its bonding characteristics in terms of bond strength into dentin and curing ability. METHODS: An experimental adhesive resin was prepared by incorporation of 2.5% MDPB into proprietary adhesive (LB Bond), and the inhibitory effect of cured specimen against the growth of Streptococcus mutans on its surface was determined. Bond strength to human dentin and degree of conversion of the experimental adhesive in combination with 1, 2, or 5% MDPB-containing primers, which were previously reported to possess bactericidal effect, were evaluated by conventional tensile bond strength test and Fourier transformation infrared spectroscopy. RESULTS: The cured experimental adhesive exhibited an inhibitory effect on S. mutans growth, reducing the number of bacteria to approximately 3% of control adhesive without MDPB. Tensile bond strength of experimental adhesive was not significantly different from that of the control (p>0.05), and use in combination with MDPB-containing primer did not show any adverse influence on bond strength. The degree of conversion of the bonding system was not different (p>0.05) between control and experimental adhesive irrespective of addition of MDPB into primer. SIGNIFICANCE: These results indicate that an adhesive resin with antibacterial activity after curing could be produced by incorporation of MDPB without influencing bond strength or curing performance, suggesting that the comprehensive bonding system including MDPB-containing primer and adhesive should be highly effective in its antibacterial effect before and after curing.     

In vivo antibacterial effects of dentin primer incorporating MDPB

This study examined the hypothesis that experimental primer containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB), which was previously reported to show bactericidal effects in vitro, inhibits bacteria in cavities under in vivo conditions. The number of bacteria resulting from applying primer solution to cavities in dog teeth infected with Streptococcus mutans was determined. The infected cavities were also restored using primer and the pulp response was histopathologically examined after 7, 30 and 75 days. No bacteria were recovered after applying the experimental primer, although the bactericidal effects of the proprietary primer were insignificant. Restoration with the experimental primer resulted in little or no pulpal inflammation for all periods; whereas, mild to moderate inflammatory response was observed when using proprietary primer. These results indicate that the experimental primer containing MDPB could exhibit in vivo antibacterial effects, suggesting its possible clinical benefit.     

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.     

Bactericidal effect of dentin primer containing antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human carious dentin

The aim of this study was to investigate the bactericidal effect of a dentin primer incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human dentinal carious lesions. To evaluate the antibacterial activity of MDPB against anaerobes, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) against obligate anaerobes and facultative anaerobic strains of lactobacilli were determined. Bacteria were recovered from carious dentin samples obtained from the teeth of patients, and the bactericidal activities of the experimental primer containing 5% MDPB and three commercially available primers were compared by counting the number of viable cells after contact with diluted solutions of each primer for 30 s. MDPB showed strong antibacterial activity against anaerobes, the MIC and MBC values ranging from 3.9 to 31.3 micrograms/ mL-1 and 15.6-125 micrograms/ mL-1, respectively. Experimental primer containing MDPB was the most bactericidal among the materials tested (ANOVA, Fisher's PLSD test, P < 0.05) and was able to kill the bacteria completely even when diluted 40 times, while the three commercial products exhibited little activity at 40 times dilution. These results indicate that incorporation of MDPB into dentin primer could be beneficial for eliminating the residual bacteria in cavities.     

An in vivo evaluation of bonding ability of comprehensive antibacterial adhesive system incorporating MDPB.

OBJECTIVES: This study examined the in vivo bonding ability to sound dentin of antibacterial adhesive systems incorporating an antibacterial monomer MDPB based on morphological evaluation of the resin-dentin interface. METHODS: Class V cavities were prepared on the buccal surfaces of the teeth of a beagle dog and a composite filling performed using (1) commercial self-etching system Liner Bond 2 (LB primer+LB bond), (2) experimental primer containing 5% MDPB and LB bond, (3) LB primer and experimental bonding-resin containing 2.5% MDPB, or (4) combination of experimental primer and bonding-resin. After 7 days, the tooth crown was cut and fixed in half-Karnovsky's solution, and the sectioned surface observed under scanning electron microscopy (SEM) after treatment with phosphoric acid and NaOCl. The ultrastructure of the bonding interface was also examined by transmission electron microscopy (TEM). Microtensile bond strengths (microTBS) of each group were measured using extracted teeth. RESULTS: SEM demonstrated that all groups produced a 1-2microm thick hybrid layer with funnel shaped resin tags, although the length of tags was shorter for the group in which MDPB-containing bonding-resin was used. TEM examination supported good adhesion of the comprehensive adhesive system employing MDPB-containing primer/bonding-resin, showing integrity between resin and dentin. There were no significant differences in microTBS among the four groups tested (p>0.05, ANOVA). SIGNIFICANCE: This study confirmed that the experimental antibacterial adhesive systems employing MDPB-containing primer or/and bonding-resin could produce an effective bond under in vivo conditions.     

Cytotoxic effects of composite restorations employing self-etching primers or experimental antibacterial primers

OBJECTIVE: The aim of this study was to investigate the cytotoxic effects of composites which employ proprietary self-etching primers or experimental primers containing an antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on human pulpal cells by in vitro dentine barrier tests. METHODS: Experimental primers were prepared by the addition of MDPB to each of two control proprietary primers at 1, 2 and 5%. Direct and indirect composite specimens were placed using each primer on one side of a dentine disk assembled in a simple pulp chamber device. Human pulp cells were incubated on the other side of the disk. After 48 h of incubation, the uptake of [3H]-thymidine by the cells was compared with that for negative controls using wax. Tests were repeated four times for each material. The diffusion of monomers from each specimen was determined using the same device. RESULTS: The specimens with control primers showed 26-35% reduction in cell activity. There were no significant differences in cytotoxicity between the control and experimental primers-specimens (Kruskal-Wallis test, p > 0.05). 2-Hydroxyethyl methacrylate at more than 1 mg ml-1 diffused from all specimens and was considered to be the cause of cytotoxic effects. The concentrations of MDPB diffused from the experimental primers-specimens were less than the toxic level, even for 5% MDPB-containing specimens. CONCLUSIONS: The results demonstrate that composites employing proprietary self-etching primers produced cytotoxic effects on human pulpal cells in vitro, although the toxicity was not severe. Incorporation of MDPB into a proprietary primer of up to 5% had no significant influence on the cytotoxicity observed.     

Influence of human dentine on the antibacterial activity of self-etching adhesive systems against cariogenic bacteria

OBJECTIVES: The incorporation of antibacterial agents into adhesive systems has been proposed to eliminate residual bacteria from dentine. This study used the agar diffusion method to evaluate the antibacterial activity of Clearfil Protect Bond (CPB), Clearfil SE Bond (CSEB), Clearfil Tri-S Bond (C3SB) and Xeno-III (XIII) self-etching adhesive systems, with or without light-activation, against cariogenic bacteria, and to assess the influence of human dentine on the antibacterial activity of these materials. METHODS: An aliquot of 10 microl per material (and individual components) were pipetted onto paper and dentine discs distributed in Petri dishes containing bacterial culture in BHI agar. Positive control was 0.2% chlorhexidine digluconate (CHX). RESULTS: After incubation, the adhesive components of CPB and CSEB, liquid A of XIII and C3SB did not present antibacterial activity when applied to paper discs. The non-light-activated CPB primer+adhesive promoted the greatest inhibition of Streptococcus mutans (p<0.05), whereas with light-activation, there was no significant difference between primer+adhesive and primer alone. For Lactobacillus acidophilus, CPB primer presented the greatest antibacterial activity in both light-activation conditions (p<0.05). Regarding the dentine discs, only CHX promoted an inhibitory effect, though less intense than on paper discs (p<0.05). CHX presented greater antibacterial activity against S. mutans than against L. acidophilus (p<0.05). CONCLUSIONS: Light-activation significantly reduced the antibacterial activity of the self-etching adhesive systems; MDPB incorporation contributed to the effect of adhesive systems against cariogenic bacteria; the components eluted from the adhesive systems were not capable to diffuse through 400 microm-thick dentine disc to exert their antibacterial activity against cariogenic bacteria.     

Antibacterial activities of MDPB and fluoride in dentin bonding agents

The aim of this study was to compare in vitro antibacterial activity of MDPB containing bonding system ABF with activities of three Fluoride containing bonding systems (Fuji Bond LC (FBLC), Prime&Bond NT (PBNT), and FluoroBond (FLB). Two bacterial strains were tested: Streptococcus mutans and Lactobacillus acidophilus. The study was performed on Muller Hinton Agar by Agar Well Technique. The bacterial agar was evenly distributed over the surface of petri dishes. Standard wells were punched into the agar. The test materials were placed in the wells of Muller Hinton agar plates, inoculated with Streptococcus mutans NCTC10449 and Lactobacillus acidophilus. The diameters of inhibition zones produced around the materials were measured after 24 h of incubation at 37 +/- 1 degrees C. For statistical analysis, Duncan's multiple range test was used. The primers of bonding agents were highly effective against to Streptococcus mutans. The MDPB containing primer of ABF Bond produced the greatest inhibition zones against to Lactobacillus acidophilus. It was followed by FLB primer. Lactobacillus acidophilus was resistant to FBLC primer and bonding, ABF, PBNT and FLB bonding agents. The results of this study indicated that, incorporation of MDPB in primer of self-etch system increased its antibacterial activity especially against to Lactobacillus acidophilus. However, all bonding systems except for bonding agent of ABF showed some antibacterial activity against to Streptococcus mutans.     

Analysis by confocal laser scanning microscopy of the MDPB bactericidal effect on S. mutans biofilm CLSM analysis of MDPB bactericidal effect on biofilm

Since bacteria remain in the dentin following caries removal, restorative materials with antibacterial properties are desirable to help maintaining the residual microorganisms inactive. The adhesive system Clearfil Protect Bond (PB) contains the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) in its primer, which has shown antimicrobial activity. However, its bactericidal effect against biofilm on the dentin has been little investigated.

Objective

The aim of this study was to analyze by confocal laser scanning microscopy (CLSM) and viable bacteria counting (CFU) the MDPB bactericidal effect against S. mutans biofilm on the dentin surface.

Material and Methods

Bovine dentin surfaces were obtained and subjected to S. mutans biofilm formation in BHI broth supplemented with 1% (w/v) sucrose for 18 h. Samples were divided into three groups, according to the primer application (n=3): Clearfil Protect Bond (PB), Clearfil SE Bond, which does not contain MDPB, (SE) and saline (control group). After the biofilm formation, Live/Dead stain was applied directly to the surface of each sample. Next, 10 µL of each primer were applied on the samples during 590 s for the real-time CLSM analysis. The experiment was conducted in triplicate. The primers and saline were also applied on the other dentin samples during 20, 90, 300 and 590 s (n=9 for each group and period evaluated) and the CFU were assessed by colonies counting.

Results

The results of the CLSM showed that with the SE application, although non-viable bacteria were detected at 20 s, there was no increase in their count during 590 s. In contrast, after the PB application there was a gradual increase of non-viable bacteria over 590 s.

Conclusions

The quantitative analysis demonstrated a significant decrease of S. mutans CFU at 90 s PB exposure and only after 300 s of SE application. Protect Bond showed an earlier antibacterial effect than SE Bond.     

An in vitro investigation of penetration depth of dentine bonding agents into carious dentine

The aim of the present in vitro study was to determine the penetration depth of dentine bonding agents into carious dentine as a possible strategy in caries treatment of deep lesions. Forty-eight extracted carious teeth were used for the experiments and divided in four groups. In a split-tooth design, one half of each tooth was treated without caries excavation, and the second half after caries excavation. In group 1 the teeth were treated with Prime & Bond 2.0 without phosphoric acid etching, and in group 2 with phosphoric acid etching. In group 3, the teeth were treated with All-Bond 2 without phosphoric acid etching, and in group 4 with phosphoric acid etching. Bonding agents were marked with an orange dye prior to application. The composition of the bonding agents had no significant influence on penetration depths. The mean thickness of the outer, necrotic caries zone in unexcavated specimens was 117 microm (+/-126). Bonding agents penetrated significantly deeper into unexcavated carious dentine (mean 124 +/- 76 microm) compared with excavated dentine (11 +/- 14 microm) and sound dentine (3 +/- 4 microm). Acid etching significantly reduced the thickness of the outer caries zone, and the penetration depth of the bonding agents into unexcavated carious specimens by approximately 50%, and increased it into sound dentine. The results indicate that dentine bonding agents could completely penetrate the unexcavated outer carious dentine in 90% of specimens. Further studies are required to determine whether further caries activity is arrested after treatment with dentine bonding procedures.     

Regional bond strengths of resins to human root dentine

Objectives: The demand for restoration of root dentine defects such as cervical erosion and root caries has significantly increased recently, but there is limited information on the performance of the adhesive resins to radicular dentine. The purpose of this study was to measure the regional tensile bond strength (TBS) of composite bonded to human root and coronal dentine, and to observe the interface between resin and root dentine by SEM.

Methods: Human extracted cuspid teeth were used to measure TBS with a new microtensile bond test. Enamel and cementum were removed from the labial tooth surfaces to form a long cavity preparation into dentine from the mid-crown to the apex of the root within the same tooth. All Bond 2 (all etch technique) or Imperva Bond (no etch) was bonded to dentine surfaces and covered with Protect Liner resin composite. The resin-bonded teeth were serially sliced into 16 sections at right angles to the long axis of the tooth, and the bonded surfaces were trimmed to give a bonded surface area of 1 mm² for TBS testing.

Results: All Bond 2 bond strengths to coronal and apical dentine showed high values (23.5 MPa) but the bond strength was significantly lower on cervical root dentine. Imperva Bond produced a relatively high tensile bond strength to all regional areas. SEM showed that the thickness of the resin-infiltrated layer formed by All Bond 2 in root dentine was less than coronal areas. Resin infiltration with Imperva Bond was always less than 0.5 μm. The results suggest that high TBS values can be obtained with minimal resin infiltration in root dentine.     

Determination of bactericidal activity of antibacterial monomer MDPB by a viability staining method

In this study, the bactericidal activity of antibacterial monomer MDPB (12-methacryloyloxydodecylpyridinium bromide) against Streptococcus mutans was tested by a rapid method for monitoring viability. To S. mutans culture containing fluorescence staining solution that distinguishes live from dead cells, MDPB was added at a concentration of 250, 100, 50, or 10 microg/ml. Bacterial cells were observed by fluorescence microscopy and the percentage of dead cells was calculated. After 10, 20, or 30 minutes' contact with MDPB, the live/dead ratio was measured by fluorometry and viable counts (CFU) determined by the conventional plating method. Viability staining revealed that MDPB exhibited significant bactericidal effects at 50 microg/ml or greater (ANOVA, Fisher's PLSD test), and complete killing of the cells at 250 microg/ml of MDPB was demonstrated in conjunction with a plating method. The staining method thus provided a sensitive means to determine loss of viability, and indicated the strong killing effects of MDPB on S. mutans.     

新型牙本质黏结剂体外细胞毒性研究

目的：评价一种新型牙本质黏结剂的细胞毒性，并与商品化的两种黏结剂细胞毒性进行比较。方法：采用琼脂覆盖法和四甲基偶氮唑盐(MTT)比色法，评价新型牙本质黏结剂优邦(UB)和商品化黏结剂Adper Prompt自酸蚀黏结剂(AP)与Prime＆Bond NT(PB)在人牙本质片上使用后，对L929小鼠成纤维细胞的毒性作用。结果：MTT实验中三种牙本质黏结剂细胞毒性均为1级；琼脂覆盖实验中，三种材料两种厚度牙本质片均出现脱色区和部分细胞溶解，细胞毒性评价均为1级。结论：新型牙本质黏结剂具有轻做的细胞毒性，UB对牙髓组织的影响还有待进一步研究。     

Regional bond strength of four self-etching primer/adhesive systems to root canal dentin

The purpose of this study was to evaluate the regional bond strength of a dual-cure resin core material to root canal dentin using four self-etching primer/adhesive systems. Post spaces were prepared in extracted premolars, and their root canal dentin was treated with one of the following self-etching primer/adhesive systems: ED Primer II and Clearfil Photobond, photo-cure/dual-cure systems of Clearfil Liner Bond 2V, or Clearfil SE Bond. Post spaces were filled with the dual-cure resin core material, and microtensile bond strength (microTBS) at the coronal and apical regions was measured after 24-hour storage. There were no regional differences in microTBS of the photo-cure and dual-cure systems of Clearfil Liner Bond 2V, while microTBS at the coronal region of Photobond and SE Bond groups were higher than those at the apical region. At the apical region, photo-cured Clearfil Liner Bond 2V exhibited significantly higher bond strength than those of the other systems.     

In vitro analysis of inhibitory effects of the antibacterial monomer MDPB-containing restorations on the progression of secondary root caries

Objective

This study aimed to analyze in vitro inhibitory effects of restorative materials containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on the formation of artificial secondary root caries lesions.

Methods

Class V cavities (2 mm × 2 mm) were prepared in 75 human root fragments. Specimens were randomly divided into five groups (n = 15 fragments per group) and restored as follows: (I) MDPB-free adhesive system + MDPB-free composite (negative control); (II) resin modified glass ionomer (RM-GIC; positive control); (III) MDPB-free adhesive system + MDPB-containing composite (2.83% MDPB); (IV) MDPB-containing adhesive system + MDPB-free composite; (V) MDPB-containing adhesive system + MDPB-containing composite. Artificial secondary root caries lesions were produced by a biological artificial caries challenge. The restored specimens were immersed into a culture medium containing Streptococcus mutans and sucrose for 15 days. Histological slices (80 ± 20 μm) of the specimens were used for measuring the mean depths of the artificial lesions produced in both margins of the restorations using polarized light microscopy. Results were expressed in percentage related to the mean depth of the negative control, considered 100%. Data were compared by ANOVA followed by the Tukey's test (p ≤ 0.05).

Results

The depths of lesions adjacent to cavities filled with RM-GIC (GII; 85.17 ± 15.2%) were significantly (p < 0.01) shallower than those adjacent to restorations with MDPB-free composite (GI; 100.00 ± 10.04%), despite the presence of MDPB in the adhesive system (GIV; 101.95 ± 21.32%). The depths of lesions adjacent to cavities restored with MDPB-containing composite (GIII; 82.68 ± 12.81% and GV; 85.65 ± 15.42%), despite the adhesive system used, were similar to those of RM-GIC (GII). Mean lesions depths in these groups decreased from 13% (GV) to 17% (GIII) in relation to the negative control (GI).

Conclusions

MDPB-containing composite inhibits the progression of artificial secondary root caries lesions regardless of adhesive systems.     

Effects of dual antibacterial agents MDPB and nano-silver in primer on microcosm biofilm,cytotoxicity and dentine bond properties

ObjectivesThe objective of this study was to investigate the effects of dentine primer containing dual antibacterial agents, namely, 12-methacryloyloxydodecylpyridinium bromide (MDPB) and nanoparticles of silver (NAg), on dentine bond strength, dental plaque microcosm biofilm response, and fibroblast cytotoxicity for the first time.MethodsScotchbond Multi-Purpose (SBMP) was used as the parent bonding agent. Four primers were tested: SBMP primer control (referred to as “P”), P + 5% MDPB, P + 0.05% NAg, and P + 5% MDPB + 0.05% NAg. Dentine shear bond strengths were measured using extracted human teeth. Biofilms from the mixed saliva of 10 donors were cultured to investigate metabolic activity, colony-forming units (CFU), and lactic acid production. Human fibroblast cytotoxicity of the four primers was tested in vitro.ResultsIncorporating MDPB and NAg into primer did not reduce dentine bond strength compared to control (p > 0.1). SEM revealed well-bonded adhesive–dentine interfaces with numerous resin tags. MDPB or NAg each greatly reduced biofilm viability and acid production, compared to control. Dual agents MDPB + NAg had a much stronger effect than either agent alone (p < 0.05), increasing inhibition zone size and reducing metabolic activity, CFU and lactic acid by an order of magnitude, compared to control. There was no difference in cytotoxicity between commercial control and antibacterial primers (p > 0.1).ConclusionsThe method of using dual agents MDPB + NAg in the primer yielded potent antibacterial properties. Hence, this method may be promising to combat residual bacteria in tooth cavity and invading bacteria at the margins. The dual agents MDPB + NAg may have wide applicability to other adhesives, composites, sealants and cements to inhibit biofilms and caries.     

Effect of 2-hydroxyethyl methacrylate pre-treatment on micro-tensile bond strength of resin composite to demineralized dentin

The purpose of this study was to evaluate the effect of 2-hydroxyethyl methacrylate (HEMA) application on the micro-tensile bond strength of resin composite to demineralized dentin. Artificially demineralized lesions were formed on bovine dentin surfaces and treated with 10, 30, 50, 70 and 100 wt% HEMA aqueous solution. The surfaces were then applied and covered with SE Bond and AP-X according to the manufacturer's instruction. After immersion in 37 degrees C water for 24 h, bond strength were measured using a universal testing machine. Bond strengths to both demineralized dentin and normal dentin, without HEMA application, were also measured. Scanning electron microscopic (SEM) observation and confocal laser scanning microscopy (CLSM) analysis at the resin-dentin interface were also performed. The bond strength data were statistically compared with anova and Scheffe's test (P < 0.05). Bond strength to demineralized dentin treated with over 30 wt% HEMA aqueous solution were significantly higher than that to demineralized dentin without HEMA application, but significantly lower than that to normal dentin. SEM observation revealed that the hybrid layer and resin-tags thickened and lengthened with HEMA application. In CLSM, the diffusion of adhesive primer into demineralized dentin increased with HEMA application. These results indicated that HEMA application might increase the bond strength to demineralized dentin by the enhancement of resin monomer penetration of HEMA.