Do subgingival crown margins adversely affect the periodontium?

With the increasing demand for cast restorations, the effect and influence of crown margins on the periodontium brought about many researches. These researches on crown margins were categorized by Gardner (1982) into three (3) broad categories namely: location, configuration and fit. Researchers on the influence of location of crown margins in the preparation of restorations, whether they be 1) supragingival 2) at the crest of the gingival margin or 3) subgingival, on the adjacent periodontal tissues had led to results which either supported the placement of cast restorations at one location level, that is, supragingivally, or those that support the view that the location of crown margins do not seem to significantly affect the periodontium.