| Objective: To investigate the relationship between the levels of tumor necrosis factor (TNF) and matrix metal- oproteinases-8 (MMP-8) and the health status of periodontal tissue and the influence of porcelain-fused-to-metal (PFM) crown materials on the periodontal tissue by detecting the levels of TNF and MMP-8 in the affected gingival crevicular fluid (GCF) in the 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 Case selecting and grouping for experiment:22 cases (male 10 and female 12) of restoring premaxillary teeth with Ni-Cr PFM crown, Ni-Cr-Ti PFM crown or Au-Pt PFM crown were selected, and they had health periodontal tissues in counterparts on the opposite side and neither took antibiotics and nor received periodontal treatment for at least 3 months; they had not systematic diseases and female patients were non-pregnant. Under the conditions of strictly defining the periodontal status, crown margin position, marginal adaptation and crown contour, 30 standardized PFM crowns (10 for each) were divided in 3 group, i.e. Ni-Cr PFM crown group (Group A), Ni-Cr-Ti PFM crown group (Group B) and Au-Pt PFM crown group (Group C); patients' health counterparts on the opposite side were taken as the control group.2 Observed indices: At 6 months and 12 months after being crowned, the volume of tested GCF, the levels of TNF and MMP-8 in GCF were recorded and their clinical indices were detected, including plaque index (PLI) (refer to Silness-L?e standard), sulcus bleeding index(SBI) (refer to Mühleman-Son standard) and gingival crevicular depth (GCD), i.e. the distance from the bottom of gingival sulcus to gingival margin that is expressed with millimeter (rounded off).3 Preparation of filter paper strip: Model Wharman III filter paper was cut up into filter paper strips of 2×10mm 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 GCF:In order to ensure the volume of GCF 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 (4 sites/tooth) were chosen as the fluid-taking area. A filter paper strip 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. Sample polluted with blood stain or saliva should be abandoned. The taken-out sample 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 ( about 1mg /μL), getting the volume of GCF. Subsequently, 250ml 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 in GCF, and radioimmunoassay was used for detecting the content of TNF.Results: 1 At 6 months after restoring, the gingival crevice depth (GCD), sulcular bleeding index (SBI)and Gingival Crevicular Fluid (GCF) of the treated teeth in Ni-Cr PFM crown group were markedly higher than those in the control group (P<0.05); at 12 months after restoring, the above-mentioned indices in the Ni-Cr PFM crown group remained higher levels, being evidently 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)2 At 6 months after restoring, GCD, GCF volume, TNF and MMP-8 of the treated teeth in Ni-Cr-Ti PFM crown were markedly higher than those in the control group(P<0.05), but there is not difference in SBI between the treated teeth and the control group(P>0.05); at 12 months after restoring, the above- mentioned indices were evidently higher than those in 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).3 At 6 months after restoring, GCD, GCF volume and TNF of the treated teeth in Au-Pt PFM crown group were markedly higher than those in the control group(P<0.05), but there is not difference in SBI and MMP-8 between the treated teeth and the control group(P>0.05); at 12 months after restoring, GCD, GCF volume, MMP-8 and TNF were evidently higher than those in 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 At 6 months and at 12 months after restoring, horizontal comparison showed that the levels of TNF and MMP-8 in Ni-Cr PFM crown group was markedly higher than those in Au-Pt 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).Conclusions: 1 All 3 kinds of PFM restoration can influence the levels of TNF and MMP-8 in GCF. 2 At 6 months after PFM restoration, the levels of TNF and MMP-8 in GCF in Ni-Cr PFM crown group and Ni-Cr-Ti PFM crown rose, and there was statistical difference; the level of TNF in GCF in NI-Cr-Ti PFM crown group rose, and there was statistical difference; however, there was no change in the level MMP- 8. 3 At 12 months after PFM restoration, there was no difference in the levels of TNF and MMP-8 in GCF in Ni-Cr PFM crown group and Ni-Cr-Ti PFM crown group as compared with those at 6 months after PFM restoration; at 12 months after PFM restoration, the level of MMP-8 was higher than that at 6 months after PFM restoration, and there was statistical difference; however, there was no change in the level TNF. 4 Comparing the levels of TNF and MMP-8 in GCF at 12 months after the 3 kinds of PFM restoration showed that Ni-Cr PFM crown group is the highest, Ni-Cr-Ti PFM crown group took second place (however, there was no difference between No-Cr PFM crown group and Ni-Cr-Ti PFM crown group),and Au-Pt PFM crown group was the lowest.5 Au-Pt PFM crown has smaller influence on periodontal tissue as compared with Ni-Cr PFM crown and Ni-Cr-Ti PFM crown.
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