| Objective: To investigate the relationship between the levels of tumor necrosis factor-α(TNF-α) and matrix metal- oproteinases-8(MMP-8)and the health status of peri implant tissue and the effect of porcelain-fused-to-metal(PFM)crown materials on the peri-implant tissue by detecting the levels of TNF and MMP-8 in the affected peri-implant sulcular fluid (PISF)in different periods of different materials of PFM crowns so as to provide the experiment basis for selecting PFM crown materials and evaluating the influence of prosthesis.Methods:1 Sample selecting and grouping for experiment:20 samples(male 12 and female 8) whose posterior implant were restored with Ni-Cr PFM crown,Ni-Cr-Ti PFM crown or pure titanium PFM crown were selected. They had healthy periodontal tissues and they neither took antibiotics nor received periodontal treatment for at least 3 months; they had not systematic diseasesand female patients were nonpregnant.Under the conditions of strictly defining the periodontal status, the position of crown margin, the adaptation of margin and crown contour, 30 standardized PFM crowns(10 for each group) were divided into 3 groups, i.e. Ni-Cr PFM crown group(Group A),Ni-Cr-Ti PFM crown group(Group B)and pure titanium PFM crown group(Group C);patients'health natrue theeh which were adjacent to implants were taken as control group.Observed indices: Before and after 6 months being restored crowns,the volume of tested PISF,the levels of TNF-αand MMP-8 in PISF were recorded and their clinical indices were detected,including plaque index(PLI)(refer to Silness-Loe standard),sulcus bleeding index(SBI)(refer to Mühleman-Son standard)and gingival crevicular depth(GCD),i.e.the distance measured with millimeter(rounded off) is from the bottom of gingival sulcus to gingival margin.3 Preparation of filter paper strip:Model Wharman III filter paper was cut up into filter paper strips of 1.5×10mm and after sterilizing them,every 4 strips were placed into a EP tube and numbered,then they were weighed(with the accuracy of 0.01mg)for use. 4 Collection and preservation of PISF:In order to ensure the volume of PISF is not influenced by clinical examination,sampling should be performed after clinical examination.Bacterial plaques on each dental face were eliminated with a dental scaler and cotton rolls were used for wet insulation;the M-D convergence angles (4sites/tooth)were chosen as the fluid-taking areas.A filter paperstrip was gently inserted into the gingival sulcus along the dental face until it encountered a resistance;the filter paper strip was taken out after standing for 30 seconds.Paperstrip polluted with blood stain or saliva should be abandoned.The taken-out paperstrip was rapidly replaced into the original EP tube,sealed and weighed;after subtracting the original weight,the weight was converted into volume with volume mass(about1mg/μL), getting the volume of PISF.Subsequently, 300ml of BSA-PBS buffer solution was added to each sample, and each sample was oscillated for 1 hour at ordinary temperature in a constant temperature shaker, centrifuged at low temperature (4℃,10000r/min)for 10 minutes; the supernatant fluid was taken, sub-packaged and numbered, being frozen at-70℃. 5 In this experiment, double antibodies sandwich ELISA was used for detecting the level of MMP-8 and TNF-αin PISF.Results: 1 Before restoring ,there is no difference in plaque index (PLI) gingival crevice depth(GCD), sulcular bleeding index(SBI), peri-implant sulcular fluid (PISF), TNF and MMP-8 in PISF between the A B C treated implants and the control group (P>0.05).2 Six months after restoring,the gingival crevice depth(GCD), sulcular bleeding index(SBI)and peri-implant sulcular fluid (PISF)of the treated implants in Ni-Cr PFM crown group were markedly higher than those in the control group(P<0.05); There was no difference in plaque index(PLI) between the treated teeth and the control group in different periods.(P>0.05) 3 Six months after restoring,GCD,PISF volume,TNF-αand MMP-8 of the treated implants in Ni-Cr-Ti PFM crown were markedly higher than those in the control group(P<0.05),but there is no difference in SBI between the treated implants and the control group(P>0.05); There is no difference in plaque index (PLI)between the treated teeth and the control group in different periods(P>0.05).4 Six months after restoring, there were no differences in SBI,TNF-α,MMP-8,GCD,PISF volume and PLI between the treated implants in pure titanium PFM crown group and the control group(P>0.05).5Before restoring, there were no differences in SBI,TNF -α,MMP-8,GCD,PISF volume and PLI in Ni-Cr PFM crown group Ni-Cr-Ti PFM crown and pure titanium PFM crown group. 6 Six months after restoring,horizontal comparison showed that the levels of TNF-αand MMP-8 in Ni-Cr PFM crown group were markedly higher than those in pure titanium PFM crown group (P<0.05),and there was no difference between Ni-Cr PFM crown group and Ni-Cr-Ti PFM crown group(P>0.05). 7 TNF-αand MMP-8 of the treated implant in Ni-Cr-Ti PFM crown and Ni-Cr-Ti PFM crown 6 months after restoring were markedly higher than those before restoring(P<0.05).There is no difference in pure titanium PFM crown group before restoring and after(P>0.05).Conclusions:1 Ni-Cr PFM crown and Ni-Cr-Ti PFM crown can influence the levels of TNF-αand MMP-8 in PISF.2 Six months after PFM restoration,the levels of TNF and MMP-8 in PISF in Ni-Cr PFM crown group and Ni-Cr-Ti PFM group were higher than those in nature teeth and there was no difference in Ni-Cr PFM crown group and Ni-Cr-Ti PFM ; however,there was no significant difference in the pure titanium PFM crown group.3 Six months after PFM restoration,the levels of TNF-αand MMP-8 in GCF in Ni-Cr PFM crown group and Ni-Cr-Ti PFM crown group were higher than those before PFM restoration,and there was statistical difference;however, there was no difference in the pure titanium PFM crown group .4 Ni-Cr PFM crown group and Ni-Cr-Ti PFM crown group had significant effect on peri implant tissues (however,there was no difference between No-Cr PFM crown group and Ni-Cr-Ti PFM crown group).5 Pure titanium PFM crown probably has no influence on peri-implant tissue as compared with Ni-Cr PFM crown and Ni-Cr-Ti PFM crown.
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