| Objective: To study the effect of Streptococcus mutans and its fluoride resistant strain on the bonding interface between three kinds of CAD / CAM ceramics(one is glass ceramics,the other two are resin ceramic composites)and tooth tissue,and the bonding strength of three kinds of ceramic blocks,so as to provide theoretical basis for paying attention to the influence of bacterial factors on the bonding of CAD / CAM ceramic restorations.Method: 1.Detection of S.mutans UA159 and induction of its fluoride-resistant strains: S.mutans UA159 was resuscitated,amplified by 16 S r DNA PCR and sequenced.After it was determined as the target strain,the fluoride-resistant strain was induced by step-by-step induction method and determined as pure culture.2.Production of testing specimen:(1)Specimens for observing the bonding interface: the selected CAD / CAM ceramics are IPS Empress(IPS),Lava Ultimate(LU)and Vita Enamic(EN).The crowns of the molars were removed and the pulp cavity was filled with fluid resin.The cross section near the crowns was concentric circle of fluid resin,dentin and enamel.The specimens were bonded with three kinds of ceramics,and the bonding interface was exposed by longitudinal grinding.(2)Specimens for micro tensile test: Three kinds of ceramic blocks were bonded to the fluid resin by the double curing resin adhesive.3.The test pieces were immersed in the anaerobic culture of Streptococcus mutans UA159(UA),its fluoride resistant strain liquid(FR)and liquid medium(BHI)for 14 days.4.The results showed that(1)the interface between ceramic and adhesive(2)the interface between adhesive and enamel / dentin / fluid resin,and the percentage of fracture length to the length of each interface was calculated.5.Scanning electron microscope was used to observe whether the ceramic and the adhesive had the filler coming out and cracks.6.Test the micro tensile strength.Result:(1)UA and FR can make the cracks between ceramic and resin adhesive more obvious,and the cracks between resin ceramic composite and adhesive are higher than that of glass ceramic IPS,in which nano ceramic LU has the most cracks,EN is the second,IPS is the least.(2)The cracks in the interface between the adhesive and enamel / dentin / fluid resin of the specimens immersed in the bacterial solution(UA and FR)were significantly increased,among which the cracks in the interface between the adhesive and fluid resin were the least,the cracks in the interface between the adhesive and dentin were the most,and the percentage of the cracks in the interface between the adhesive and enamel was in the middle.(3)Under the electron microscope,no cracks were observed in the glass ceramic matrix of IPS,but a small amount of cracks were observed in the matrix of LU soaked in bacterial solution for 14 days,and almost no cracks were observed in EN.A large crack can be observed between the resin adhesives,and the filler can come out.(4)The micro tensile strength of all ceramics in UA and FR was lower than that in the control group.The micro tensile strength of IPS in IPS was significantly higher than that of LU and EN.There was no significant difference in micro tensile strength between UA group and FR group.Conclusion:1.Streptococcus mutans and its fluoride resistant strains can make the bonding interface between ceramic and tooth crack,and weaken the micro tensile strength between ceramic and resin.2.The influence of Streptococcus mutans and its fluoride resistant strain on glass ceramics is less than that of resin ceramics,and the bonding strength of the former is higher than that of the latter.3.The effect of Streptococcus mutans and its fluoride resistant strain on the micro tensile strength between ceramic and resin has no significant difference. |
PDF Full Text Request