Study Of Full Crown With Two Different Margin Designs On Periodontal Tissue

Objective: The effect of two types of full crown margin designs on periodontal tissue are studied in this paper, SBI,GI,AST,ALP and probing depth as our tentative indexes.Serious destruction and unpleasing color of tooth, caused by caries , injury, and some other reasons would made the tooth lost its function and contour, usually need full crown for restoring.The advantage of supergingival crown is that it could avoiding injuries during cutting the tooth and be easy to exam the fitness of crown margin with tooth, although it has unaesthetic outlook and higher risk of caries. Subgingival crown can avoid such shortcomings, but might result in inflammation and recession of gingival, and it is not as easy as the supergingival crown to be examined if the margin of crown is fit well with the tooth. As a result, many dentists choose gingival crest crown. But many other scholars consider that there is no difference effect within the three kinds of crown on periodontal tissue as long as the margin fitness is very well.There are lots of kinds of full crown material. In order to collecting cases, we choose nichrome or the alloy containing titananium. It is said that the two materials has the similar effection to periodontal tissue. We choose ceramic crown with metal neck ring and metal crown for the same reason.Up to now, more than ten kinds of materials have already been used in manufacturing crown. We choose nichrome and its alloy with titananium as our experimental materials, for these are the most common types of crown made in our hospital now. It is said that the two materials has the similar effect on periodontal tissue in some studies. Experimental crowns are either mental crown or porcelain-fused-mental crown with mental ring.As the most important biochemistry component in periodontal tissue, AST and ALP are very sensitive indexes in reflecting the destruction and recovery of periodontal tissue. AST can be a stand-alone biochemical marker for the active state of periodontopathy, and also be used to monitor in early therapy. ALP can reflect the occurring of inflammation and injury in periodontal tissue in earlier period, and predict the active state of periodontopathy in future.Method: The experiments were performed on 20 adult axleteeth. They were divided into two groups randomly, ten teeth were designed to be restored by supergingival crown, and others by gingival crest crown. We cut teeth, obtained their model, made temporary crowns with self curing plastic, and displaced them with formal crown two weeks later.Clinical indexes were recorded and gingival cervical fluid as the test specimen of AST and ALP were collected in four times: before cutting teeth, after cutting teeth, two weeks after cutting teeth and one month after formal crown put on. All specimen were kept in -70℃freezer carefully and be tested by biochemistry analysis method, all data were then analyzed by SAS 6.12 statistics software.Result: AST and ALP in supergingival crown group increase significantly in the second week after cutting teeth, but no positive observation be found just after cutting teeth and one month after formal crown put on. In gingival crest crown group, significant higher level of AST and ALP was detected on the three times, While analysis of clinical indexes results shows that the two kinds crown had no obvious difference on periodontal tissue.Conclusion: According to our experimental results, supergingival crown had significant influence two weeks after cutting teeth, than that just after cutting teeth and one month after formal crown put on. Gingival crest crown had significant difference on all the three time. So we think temporary crown could be a influencing factor to periodontal tissue; and chemistry examination could be an early and sensitive marker indicating the changes of periodontal tissues.