Laboratory Observation Of S.mutans Adhesion On Two Non-noble Metal Materials

The occurrence of lots of oral diseases is bound up with excessive accumulation of plaque in oral cavity, the bad prosthesis (such as surface rough prosthesis) is one of the important factors to promote accumulation. Recent studies have shown that the surface roughness of prosthesis is one of the factors that determine the capacity of bacterial adhesion. Co-Cr alloy and Ni-Cr alloy often are used, but because of the bad chemical stability, so influence the grow and propagate of oral microbiology. S.mutans is important to the plaque formation, we will research the adherence of S.mutans in the two prosthetic materials of different surface roughness, in order to provide certain reference for clinic.Objective:1 To evaluate the effect on adherence of S.mutans of different surface roughness, in order to put forward the suitable scope of surface roughness.2 To evaluate the correlation between Co-Cr alloy and Ni-Cr alloy crown restoration materials and S.mutans adherence, in order to make further comparison Co-Cr alloy with Ni-Cr alloy.Methods:1 Specimen preparation:(1) Forty standard specimens(8mmx8mmxlmm) of Co-Cr alloy were fabricated according to the conventional method of Metal casting, divided into 8 groups and every group 5 specimens, according to:A:sand blast+coarse grinding (2 min)+fine grinding(2 min)+hard rubber wheel polishing (2 min)+felt wheel and polishing paste (2 min), B:sand blast+coarse grinding (2 min)+fine grinding (2 min)+hard rubber wheel polishing (2 min), C:sand blast+ coarse grinding (2 min)+fine grinding (2 min), D:sand blast+coarse grinding (2 min),E: sand blast, (A group is the conventional processing method), processing and burnishing every group specimens, the whole procedure were completed by one, using TR200 hand-held roughness instrument to determine their Ra value.(2) Twenty standard specimens(8mm×8mm×1mm) of Co-Cr alloy and Ni-Cr alloy were fabricated according to the conventional method of Metal casting, according to the conventional processing method:sand blast,coarse grinding (2 min),fine grinding (2 min),hard rubber wheel polishing (2min),felt wheel and polishing paste (2min), processing and burnishing every specimen, the whole procedure were completed by one, using TR200 hand-held roughness instrument to determine their Ra value.2 The specimens were adhered to the tip of special plates using polycarboxylate cement and were sterilized.3 the adhesive test of S.mutans, colony count.4 Statistical analysis.Result:1 the relationship of surface roughness and S.mutans adhesion:(1) the average of surface roughness Ra of different processing methods(χ±s): RaA=0.296±0.051μm, RaB=0.376±0.021μm, Rac=0.746±0.101μm, RaD=1.420±0.131μm, RaE=2.300±0.141μm. RaA was the data that was processed by conventional processing method. According to the above data, we could know that surface roughness gradually increased, these data formed certainly spaced surface Ra.(2) the adhesive capacity of S.mutans of different surface roughness (χ±s,CFU/ml,×106): A:0.155±0.018, B:0.199±0.024, C:0.412±0.031, D:0.908±0.056, E:1.858±0.054. According to the above data, we could know that Bacterial adhesive capacity gradually increased.①The outcome of correlation test was the correlativity between adhesive capacity and surface roughness of the sample had statistical significance(p＜0.01).②The outcome of ANOVA was that the difference between all adhesive capacity had statistical significance(p＜0.01). The outcome of LSD-t were that except the difference between A and B had not statistical significance(p>0.05), the difference between others had statistical significance (p<0.01).2 the relationship of two alloys and bacterial adhesion:(1) the average of surface roughness Ra of conventional processing method (χ±s):Ra镍铬= 0.287±0.045μm, Ra钴铬=0.276±0.038μm, The outcome of Independent-Samples T Test was that the difference between them had not statistical significance(p＞0.05). We could exclude the effect of surface roughness.(2) The adhesive capacity of S.mutans of two materials (χ±s, CFU/ml,×106):Ni-Cr alloy: 3.128±1.020, Co-Cr alloy:4.704±1.502, the adhesive capacity of Co-Cr alloy was more than Ni-Cr alloy. The outcome of Independent-Samples t Test was that the difference between them had statistical significance(p＜0.05). Conclusion:In the experimental conditions, we knew:1 The surface roughness and the adhesive capacity of bacteria had certain relativity, with the increase of surface roughness, bacterial adhesion also increased. So the technician should decrease the surface roughness throught some metheds, to reduce the adhesive capacity of bacteria, to maintain the health of oral organization and increase the life span of false tooth.2 Surface roughness should equal or lesser than 0.376μm to satisfy the clinical request, and the surface roughness of clinical request could be attained according to the logically conventional processing method.3 the adhesive capacity of Co-Cr alloy was more than Ni-Cr alloy, but according to the reasons, we did not suggest to use Ni-Cr alloy. Prosthetic materials could affect grow,propagate and adherence of oral microbiology, but the bacteriostasis of Prosthetic materials could destory the balance of Oral microbiology, so we should carry out Further study to resolve the infectious of restoration and plant.