Effects of thermal cycling on bonding properties of novel low-shrinkage resin adhesive / 华西口腔医学杂志

OBJECTIVES@#The current study aimed to investigate the bonding properties of a novel low-shrinkage resin adhesive containing expanding monomer and epoxy resin monomer after thermal cycling aging treatment.@*METHODS@#Expanding monomer of 3,9-diethyl-3,9-dimethylol-1,5,7,11-tetraoxaspiro-[5,5] undecane (DDTU) as an anti-shrinkage additive and unsaturated epoxy monomer of diallyl bisphenol A diglycidyl ether (DBDE) as a coupling agent were synthesized. A blend of DDTU and DBDE at a mass ratio of 1∶1, referred to as "UE", was added into the resin matrix at the mass fraction of 20% to prepare a novel low-shrinkage resin adhesive.Then, the methacrylate resin adhesive without UE was used as the blank control group, and a commercial resin adhesive system was selected as the commercial control group. Moreover, the resin-dentin bonding and micro-leakage testing specimens were prepared for the thermal cycling aging treatment. The bonding strength was tested, the fracture modes were calculated, the bonding fracture surface was observed by scanning electron microscope (SEM), and the dye penetration was used to evaluate the tooth-restoration marginal interface micro-leakage. All the data were analyzed statistically.@*RESULTS@#After aging, the dentin bonding strength of the experimental group was (19.20±1.03) MPa without a significant decrease (P>0.05), that of the blank control group was (11.22±1.48) MPa with a significant decrease (P<0.05) and that of the commercial control group was (19.16±1.68) MPa without a significant decrease (P>0.05). The interface fracture was observed as the main fracture mode in each group after thermal cycling by SEM. The fractured bonding surfaces of the experimental group often occurred on the top of the hybrid layer, whereas those of the blank and commercial control groups mostly occurred on the bottom of the hybrid layer. Micro-leakage rating counts of specimens before and after thermal cycling were as follows: the experimental group was primarily 0 grade, thereby indicating that a relatively ideal marginal sealing effect could be achieved (P>0.05); meanwhile, the blank control group was primarily 1 grade, and the penetration depth of dye significantly increased after thermal cycling (P<0.05); the commercial control group was primarily 0 grade without statistical difference before and after thermal cycling (P>0.05), while a significant difference was observed between the commercial control group and experimental group after thermal cycling (P<0.05).@*CONCLUSIONS@#The novel low-shrinkage resin adhesive containing 20%UE exhibited excellent bonding properties even after thermal cycling aging treatment, thereby showing a promising prospect for dental application.

Dental plaque microcosm biofilm behavior on a resin composite incorporated with nano-antibacterial inorganic filler containing long-chain alkyl quaternary ammonium salt / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To develop a resin composite incorporated with nano-antibacterial inorganic filler containing long-chain alkyl quaternary ammonium salt, and to measure its effect on human dental plaque microcosm biofilm.</p><p><b>METHODS</b>A novel nano-antibacterial inorganic filler containing long-chain alkyl quaternary ammonium salt was synthesized according to methods introduced in previous research. Samples of the novel nano-antibacterial inorganic fillers were modified by a coupling agent and then added into resin composite at 0%, 5%, 10%, 15% or 20% mass fractions; 0% composite was used as control. A flexural test was used to measure resin composite mechanical properties. Results showed that a dental plaque microcosm biofilm model with human saliva as inoculum was formed. Colony-forming unit (CFU) counts, lactic acid production, and live/dead assay of biofilm on the resin composite were calculated to test the effect of the resin composite on human dental plaque microcosm biofilm.</p><p><b>RESULTS</b>The incorporation of nano-antibacterial inorganic fillers with as much as 15% concentration into the resin composite showed no adverse effect on the mechanical properties of the resin composite (P > 0.05). Resin composite containing 5% or more nano-antibacterial inorganic fillers significantly inhibited the metabolic activity of dental plaque microcosm biofilm, suggesting its strong antibacterial potency (P < 0.05).</p><p><b>CONCLUSION</b>This novel resin composite exhibited a strong antibacterial property upon the addition of up to 5% nano-antibacterial inorganic fillers, thereby leading to effective caries inhibition in dental application.</p>

Development of novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To develop novel self- healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer, and to measure its properties for further clinical application.</p><p><b>METHODS</b>Microcapsules filled with healing monomer of triethylene glycol dimethacrylate were synthesized according to methods introduced in the previous research. Microcapsules were added into novel resin composite containing nano-antibacterial silica fillers grafted with long chain alkyl quaternary ammonium at mass fractions of 0, 2.5%, 5.0%, 7.5% or 10.0%. A commercial resin composite (Tetric N-Ceram) was used as control. Flexural test was used to measure resin composite flexural strength and elastic modulus. The single edge V-notched beam method was used to measure fracture toughness and self-healing efficiency. Scanning electron microscope (SEM) was used to examine the fractured surface of selected specimen for investigation of fracture mechanisms.</p><p><b>RESULTS</b>The flexural strength and elastic modulus of the resin composite were (96.4 ± 14.3) MPa and (6.2 ± 1.1) GPa respectively after incorporation of microcapsules up to 7.5%, and no significant difference was found between the experimental group and the control group [(99.1 ± 11.9) MPa and (6.1 ± 1.1) GPa] (P>0.05). The self-healing efficiency of (66.8 ± 7.0)% and (79.3 ± 9.7)% were achieved for resin composite with microcapsule mass fractions at 7.5% and 10.0%. SEM image showed that irregular films covered the fractured surface. Conclusions This novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer exhibited a promising self- healing ability, which enabled itself well up for combating bulk fracture and secondary caries in clinical application.</p>

Synthesis of a nano-antibacterial inorganic filler containing a quaternary ammonium salt with long chain alkyl and its effect on dental resin composites / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aimed to synthesize a novel nano-antibacterial inorganic filler that contains a quaternary ammonium salt with long chain alkyl and to report the antibacterial property of dental resin composites.</p><p><b>METHODS</b>A novel nano-antibacterial inorganic filler that contains a quaternary ammonium salt with long chain alkyl was synthesized based on previous research. The antibacterial property of the filler was measured. The surface of the novel nano-antibacterial inorganic filler was modified by a coupling agent to achieve a good interfacial bonding between the filler and the resin matrix. Infrared spectrum analysis was carried out. The modified novel nano-antibacterial inorganic fillers were then incorporated into the dental resin matrix. The dispersion of the fillers was observed and compared with those incorporated into Tetric N-Ceram, a commercial resin composite, under a scanning electron microscope. Streptococcus mutans was used in testing the antibacterial property of the dental resin composites.</p><p><b>RESULTS</b>A quaternary ammonium salt with a long chain alkyl was successfully grafted onto the surface of nano-silica particles. The novel nano-antibacterial inorganic filler that contains quaternary ammonium salt with a long chain alkyl showed stronger antibacterial efficacy than the antibacterial inorganic filler that contains quaternary ammonium salt with a short chain alkyl. The modified novel antibacterial inorganic fillers displayed a homogeneous dispersion in the resin composite bulk and combined closely with the resin matrix, similar to the Tetric N-Ceram. The resin composites that contain novel antibacterial inorganic fillers showed stronger antibacterial effect on Streptococcus mutans compared with the control group.</p><p><b>CONCLUSION</b>The novel nano-antibacterial inorganic filler that contains a quaternary ammonium salt with long chain alkyl showed a strong antibacterial property. It also exhibited good compatibility with the dental resin matrix after undergoing coupling treatment.</p>

Study on synthesis on a novel nano-antibacterial inorganic filler and its antibacterial property / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To synthesize a novel nano-antibacterial inorganic filler and provide a new way to give dental composite resin antibacterial property.</p><p><b>METHODS</b>Quaternary ammonium iodide N,N,N-trimethyl-3-(trimethoxysilyl) propan-1-aminium iodide were organically synthesized firstly and then the N,N,N-trimethyl-3-(trimethoxysilyl) propan-1-aminium iodide was grafted to the nano-silica particle to synthesize the antihacterial inorganic fillers nano-silica particle grafted with quaternary ammonium salt. All the products were analyzed and identified by infrared spectrum analysis. Then Streptococcus mutans were chosen as experimental object to analysis the antibacterial property of nanoantibacterial inorganic filler.</p><p><b>RESULTS</b>Quaternary ammonium salt was grafted to the surface of nano-silica particles successfully by infrared spectrum analysis. Compared with the control group, the nano-silica particle grafted with quaternary ammonium salt had a strong bactericidal effect on Streptococcus mutons (P < 0.01).</p><p><b>CONCLUSION</b>The nano-silica particle grafted with quaternary ammonium salt has a strong antibacterial property and could be used to improve dental composite resin antibacterial property.</p>