In Vitro Study On The Antibacterial Properties Of Porous ZnO Photoresponse-enhanced Composite Resin

Dental resin composites have become the main filling or bonding materials for the treatment of dental defects due to their remarkable aesthetic properties,excellent mechanical properties,bonding strength and ease of operation.However,the polymerization shrinkage of composite resin material is easy to cause micro-leakage,and the accumulation of bacterial plaque,resulting in the secondary dental caries.One of the important approaches to solve the problem of secondary dental caries is endow filling and repairing materials with antibacterial properties.In recent years,the antibacterial composite resin has adverse effects on the long-term antibacterial effect due to the release of antibacterial agents.Therefore,to find an effective way to maintain the long-term antibacterial effect of composite resin is an urgent problem in the field of dental materialsObjective:This research aims to synthesize a new type of dental light-curing composite resin containing porous ZnO.In order to improve the overall antibacterial effect of the composite resin,porous zinc oxide has the characteristics of enhanced photoresponsive antibacterial effect after blue light irradiation.Method:In this experiment,Bis-GMA was used as the matrix monomer to synthesize composite resin materials containing different proportions of porous ZnO.It can be divided into the following parts:（1）Firstly,porous ZnO was synthesized by hydrothermal method,and its morphology,composition and structure were analyzed by field emission scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and X-ray diffraction（XRD）.（2）Take Bis-GMA as the matrix monomer and add appropriate amount of diluent,photoinitiator and co-initiator to mix to form a resin matrix.Mixed particles of micron Si O₂ and nano Si O₂ are used as reinforcing fillers.Porous ZnO accounts for different proportions of fillers.It is added into the resin matrix to prepare a new type of composite resin system with antibacterial activity.First,according to the different illumination time,it was recorded as 0 min,15 min and 30 min illumination,and it was recorded as group A,B and C.Group A was divided into A-0%,a-2.5%,a-5%and a-7.5%groups according to the different mass percentage of porous ZnO in the filler.The A-0%group was the blank control group.The polymerization shrinkage,mechanical properties,antibacterial properties and biocompatibility of different concentrations of porous ZnO composite resin in group A were tested.According to the proportion of porous ZnO in the filling,the two groups of B and C were named B-0%,B-2.5%,B-5%,B-7.5%,C-0%C-2.5%,C-5%and C-7.5%respectively.The antibacterial properties and biocompatibility of composite resins containing different concentrations of porous ZnO were tested.Results:（1）Analyze the morphology,composition and structure of the synthesized porous ZnO by field emission scanning electron microscope（SEM）,transmission electron microscope（TEM）and X-ray diffraction（XRD）.These results prove the successful synthesis of porous ZnO with a diameter of about 2.5μm-3.0μm.（2）Polymerization shrinkage result:With the increase of the proportion of porous ZnO,the polymerization shrinkage of the composite resin first increased and then decreased.When the proportion of porous ZnO was 5%,there was no significant difference in the polymerization shrinkage between the composite resin and other groups（P>0.05）.（3）Mechanical properties result:With the increase of the proportion of porous ZnO,the flexural strength,elastic modulus and vickers hardness of the composite resin increased first and then decreased.The mechanical properties of the composite resin material are the best when the proportion of porous ZnO is 2.5%.There was no significant difference in flexural strength among the groups（P>0.05）;There was no significant difference in elastic modulus between 5%group and other groups（P>0.05）;The results of Vickers hardness showed that there were significant differences between 2.5%group and other groups（P<0.05）.Although the mechanical properties gradually decreased with the increase of the proportion of porous ZnO,the flexural strength can reach 80 MPa of ISO 4049 standard.（4）Antibacterialial activity:For group A without illumination,the antibacterial properties of the composite resin increased with the increase of the proportion of porous ZnO.For B and C samples illuminated by blue light,when the proportion of ZnO is the same,the antibacterial performance is significantly enhanced with the extension of illumination time.When the illumination time is the same,the higher the proportion of porous ZnO,the more obvious the antibacterial effect of light response.（5）Cytotoxicity:Low concentration of Zn²⁺could promote the growth of cells.With the increase of the proportion of porous ZnO,the relative increment rate of cells cultured in the composite resin extract first increased and then decreased.When the proportion of porous ZnO was 5%,the cell proliferation rate was the highest.After 15 minutes and 30 minutes of light,the cell proliferation rate of 5%of the experimental group was lower than that of 2.5%group.However,the cell proliferation rate of all the experimental groups after 30 minutes of light exposure was higher than that of the experimental group after 15 minutes of light exposure.All experimental groups promoted cell proliferation.ConclusionsComprehensive analysis of the above experimental results,it can be concluded that the addition of porous ZnO can endow the composite resin with antibacterial properties.When the content of porous ZnO was 5%,it had good antibacterial property and cell proliferation promoting property under 30 min illumination,and had no significant effect on the polymerization shrinkage and mechanical properties of the composite resin.Therefore,the composite resin containing 5%porous ZnO has a certain application prospect.