A novel antibacterial resin composite for improved dental restoratives

Effect of water-ageing on dentine bond strength and anti-biofilm activity of bonding agent containing new monomer dimethylaminododecyl methacrylate

OBJECTIVES

The objectives of this study were to develop bonding agent containing a new antibacterial monomer dimethylaminododecyl methacrylate (DMADDM) as well as nanoparticles of silver (NAg) and nanoparticles of amorphous calcium phosphate (NACP), and to investigate the effects of water-ageing for 6 months on dentine bond strength and anti-biofilm properties for the first time.

METHODS

Four bonding agents were tested: Scotchbond Multi-Purpose (SBMP) Primer and Adhesive control; SBMP+5% DMADDM; SBMP+5% DMADDM+0.1% NAg; and SBMP+5% DMADDM+0.1% NAg with 20% NACP in adhesive. Specimens were water-aged for 1d and 6 months at 37°C. Then the dentine shear bond strengths were measured. A dental plaque microcosm biofilm model was used to inoculate bacteria on water-aged specimens and to measure metabolic activity, colony-forming units (CFUs), and lactic acid production.

RESULTS

Dentine bond strength showed a 35% loss in 6 months of water-ageing for SBMP control (mean±sd; n=10); in contrast, the new antibacterial bonding agents showed no strength loss. The DMADDM-NAg-NACP containing bonding agent imparted a strong antibacterial effect by greatly reducing biofilm viability, metabolic activity and acid production. The biofilm CFU was reduced by more than two orders of magnitude, compared to SBMP control. Furthermore, the DMADDM-NAg-NACP bonding agent exhibited a long-term antibacterial performance, with no significant difference between 1d and 6 months (p>0.1).

CONCLUSIONS

Incorporating DMADDM-NAg-NACP in bonding agent yielded potent and long-lasting antibacterial properties, and much stronger bond strength after 6 months of water-ageing than a commercial control. The new antibacterial bonding agent is promising to inhibit biofilms and caries at the margins. The method of DMADDM-NAg-NACP incorporation may have a wide applicability to other adhesives, cements and composites.

Dual antibacterial agents of nano-silver and 12-methacryloyloxydodecylpyridinium bromide in dental adhesive to inhibit caries

Dental resins containing 12-methacryloyloxydodecylpyridinium bromide (MDPB) showed potent antibacterial functions. Recent studies developed antibacterial resins containing nanoparticles of silver (NAg). The objectives of this study were to develop an adhesive containing dual agents of MDPB and NAg for the first time and to investigate the combined effects of antibacterial adhesive and primer on biofilm viability, metabolic activity, lactic acid, dentin bond strength, and fibroblast cytotoxicity. MDPB and NAg were incorporated into Scotchbond Multi-Purpose (SBMP) adhesive "A" and primer "P". Five systems were tested: SBMP adhesive A; A + MDPB; A+NAg; A + MDPB + NAg; P + MDPB + NAg together with A + MDPB + NAg. Dental plaque microcosm biofilms were cultured using mixed saliva from 10 donors. Metabolic activity, colony-forming units, and lactic acid production of biofilms were investigated. Human fibroblast cytotoxicity of bonding agents was determined. MDPB + NAg in adhesive/primer did not compromise dentin bond strength (p > 0.1). MDPB or NAg alone in adhesive substantially reduced the biofilm activities. Dual agents MDPB + NAg in adhesive significantly reduced the biofilm viability compared with each agent alone (p < 0.05). The greatest inhibition of biofilms was achieved when both adhesive and primer contained MDPB + NAg. Fibroblast viability of groups with dual antibacterial agents was similar to control using culture medium without resin eluents (p > 0.1). In conclusion, this study showed for the first time that the antibacterial potency of MDPB adhesive could be substantially enhanced via NAg. Adding MDPB + NAg into both primer and adhesive achieved the strongest antibiofilm efficacy. The dual agent (MDPB + NAg) method could have wide applicability to other adhesives, sealants, cements, and composites to inhibit biofilms and caries.

Preparation and evaluation of dental resin with antibacterial and radio-opaque functions

In order to prepare antibacterial and radio-opaque dental resin, a methacrylate monomer named 2-Dimethyl-2-dodecyl-1-methacryloxyethyl ammonium iodine (DDMAI) with both antibacterial and radio-opaque activities was added into a 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropyl)-phenyl]propane (Bis-GMA)/methyl methacrylate (MMA) dental resin system. Degree of conversion (DC), flexural strength (FS) and modulus (FM), water sorption (WS) and solubility (WSL), antibacterial activity, and radio-opacity (ROX) of the obtained dental resin system were investigated. Bis-GMA/MMA resin system without DDMAI was used as a control. The results showed that DDMAI could endow BIS-GMA/MMA resin system with good antibacterial (p < 0.05) and radio-opaque function without influencing the DC (p > 0.05). However, incorporating DDMAI into Bis-GMA/MMA resin could reduce mechanical properties (p < 0.05) and increase WS and WSL (p < 0.05), thus further work is needed in order to optimize the resin formulation.

Comparison of quaternary ammonium-containing with nano-silver-containing adhesive in antibacterial properties and cytotoxicity

OBJECTIVE

Antibacterial primer and adhesive are promising to help combat biofilms and recurrent caries. The objectives of this study were to compare novel bonding agent containing quaternary ammonium dimethacrylate (QADM) with bonding agent containing nanoparticles of silver (NAg) in antibacterial activity, contact-inhibition vs. long-distance inhibition, glucosyltransferases (gtf) gene expressions, and cytotoxicity for the first time.

METHODS

QADM and NAg were incorporated into Scotchbond Multi-Purpose adhesive and primer. Microtensile dentin bond strength was measured. Streptococcus mutans (S. mutans) biofilm on resin surface (contact-inhibition) as well as S. mutans in culture medium away from the resin surface (long-distance inhibition) were tested for metabolic activity, colony-forming units (CFUs), lactic acid production, and gtf gene expressions. Eluents from cured primer/adhesive samples were used to examine cytotoxicity against human gingival fibroblasts.

RESULTS

Bonding agent with QADM greatly reduced CFU and lactic acid of biofilms on the resin surface (p<0.05), while having no effect on S. mutans in culture medium away from the resin surface. In contrast, bonding agent with NAg inhibited not only S. mutans on the resin surface, but also S. mutans in culture medium away from the resin surface. Bonding agent with QADM suppressed gtfB, gtfC and gtfD gene expressions of S. mutans on its surface, but not away from its surface. Bonding agent with NAg suppressed S. mutans gene expressions both on its surface and away from its surface. Bonding agents with QADM and NAg did not adversely affect microtensile bond strength or fibroblast cytotoxicity, compared to control (p>0.1).

SIGNIFICANCE

QADM-containing adhesive had contact-inhibition and inhibited bacteria on its surface, but not away from its surface. NAg-containing adhesive had long-distance killing capability and inhibited bacteria on its surface and away from its surface. The novel antibacterial adhesives are promising for caries-inhibition restorations, and QADM and NAg could be complimentary agents in inhibiting bacteria on resin surface as well as away from resin surface.

Effects of antibacterial primers with quaternary ammonium and nano-silver on Streptococcus mutans impregnated in human dentin blocks

OBJECTIVE

Recent studies developed antibacterial bonding agents and composites containing a quaternary ammonium dimethacrylate (QADM) and nanoparticles of silver (NAg). The objectives of this study were to investigate: (1) the effect of antibacterial primers containing QADM and NAg on the inhibition of Streptococcus mutans impregnated into dentin blocks for the first time, and (2) the effect of QADM or NAg alone or in combination, and the effect of NAg mass fraction, on S. mutans viability in dentin.

METHODS

Scotchbond Multi-Purpose (SBMP) bonding agent was used. QADM and NAg were incorporated into SBMP primer. Six primers were tested: SBMP primer control, control+10% QADM (mass%), control+0.05% NAg, control+10% QADM+0.05% NAg, control+0.1% NAg, and control+10% QADM+0.1% NAg. S. mutans were impregnated into dentin blocks, then a primer was applied. The viable colony-forming units (CFU) were then measured by harvesting the bacteria in dentin using a sonication method.

RESULTS

Control+10% QADM+0.1% NAg had bacteria inhibition zone 8-fold that of control (p<0.05). The sonication method successfully harvested bacteria from dentin blocks. Control+10% QADM+0.1% NAg inhibited S. mutans in dentin blocks, reducing the viable CFU in dentin by three orders of magnitude, compared to control dentin without primer. Using QADM+NAg was more effective than QADM alone. Higher NAg content increased the potency. Dentin shear bond strength was similar for all groups (p>0.1).

SIGNIFICANCE

Antibacterial primer with QADM and NAg were shown to inhibit the S. mutans impregnated into dentin blocks for the first time. Bonding agent containing QADM and NAg is promising to eradicate bacteria in tooth cavity and inhibit caries. The QADM and NAg may have applicability to other adhesives, cements, sealants and composites.

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

OBJECTIVES

The 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.

METHODS

Scotchbond 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.

RESULTS

Incorporating 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).

CONCLUSIONS

The 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.

Dental primer and adhesive containing a new antibacterial quaternary ammonium monomer dimethylaminododecyl methacrylate

OBJECTIVES

The main reason for restoration failure is secondary caries caused by biofilm acids. Replacing the failed restorations accounts for 50-70% of all operative work. The objectives of this study were to incorporate a new quaternary ammonium monomer (dimethylaminododecyl methacrylate, DMADDM) and nanoparticles of silver (NAg) into a primer and an adhesive, and to investigate their effects on antibacterial and dentin bonding properties.

METHODS

Scotchbond Multi-Purpose (SBMP) served as control. DMADDM was synthesized and incorporated with NAg into primer/adhesive. A dental plaque microcosm biofilm model with human saliva was used to investigate metabolic activity, colony-forming units (CFU), and lactic acid. Dentin shear bond strengths were measured.

RESULTS

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the new DMADDM were orders of magnitude lower than those of a previous quaternary ammonium dimethacrylate (QADM). Uncured primer with DMADDM had much larger inhibition zones than QADM (p<0.05). Cured primer/adhesive with DMADDM-NAg greatly reduced biofilm metabolic activity (p<0.05). Combining DMADDM with NAg in primer/adhesive resulted in less CFU than DMADDM alone (p<0.05). Lactic acid production by biofilms was reduced by 20-fold via DMADDM-NAg, compared to control. Incorporation of DMADDM and NAg into primer/adhesive did not adversely affect dentin bond strength.

CONCLUSIONS

A new antibacterial monomer DMADDM was synthesized and incorporated into primer/adhesive for the first time. The bonding agents are promising to combat residual bacteria in tooth cavity and invading bacteria at tooth-restoration margins to inhibit caries. DMADDM and NAg are promising for use into a wide range of dental adhesive systems and restoratives.

Novel dental adhesive containing antibacterial agents and calcium phosphate nanoparticles

Secondary caries remains the main reason for dental restoration failure. Replacement of failed restorations accounts for 50%-70% of all restorations performed. Antibacterial adhesives could inhibit biofilm acids at tooth-restoration margins, and calcium phosphate (CaP) ions could remineralize tooth lesions. The objectives of this study were to: (1) incorporate nanoparticles of silver (NAg), quaternary ammonium dimethacrylate (QADM), and nanoparticles of amorphous calcium phosphate (NACP) into bonding agent; and (2) investigate their effects on dentin bonding and microcosm biofilms. An experimental primer was made with pyromellitic glycerol dimethacrylate (PMGDM) and 2-hydroxyethyl methacrylate (HEMA). An adhesive was made with bisphenol-A-glycerolate dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA). NAg was incorporated into primer at 0.1 wt %. The adhesive contained 0.1% NAg and 10% QADM, and 0%-40% NACP. Incorporating NAg into primer and NAg-QADM-NACP into adhesive did not adversely affect dentin bond strength (p > 0.1). Scanning electron microscopy showed numerous resin tags, and transmission electron microscopy revealed NAg and NACP in dentinal tubules. Viability of human saliva microcosm biofilms on primer/adhesive/composite disks was substantially reduced via NAg and QADM. Metabolic activity, lactic acid, and colony-forming units of biofilms were much lower on the new bonding agents than control (p < 0.05). In conclusion, novel dental bonding agents containing NAg, QADM, and NACP were developed with the potential to kill residual bacteria in the tooth cavity and inhibit the invading bacteria along tooth-restoration margins, with NACP to remineralize tooth lesions. The novel method of combining antibacterial agents (NAg and QADM) with remineralizing agent (NACP) may have wide applicability to other adhesives for caries inhibition.