Abstract
The higher the margin of the restoration is above the gingival margin, the better for the periodontal tissues. However, when such factors as retention and contour are taken into consideration, it cannot always be said that supragingival margins are best. In particular, since the axis of the mandibular molars is often inclined to the lingual, undercuts tend to occur at the margin in the lingual cervical region when it is supragingival, thus making brushing difficult. Consequently, unless there is severe gingival recession, the lingual margins in the mandibular molar region are often placed near the gingival margin.
Subgingival mrgins are unavoidable in the anterior teeth where esthetic demands are very important. However, in these cases probing should be carried out and even though the margin is subgingival, care must be taken to place it as far as possible from the bottom of the gingival sulcus. Furthermore, whenever possible the margin should be placed in the enamel when treating teeth where the root has been exposed, since a gap will often appear between the margin and the root during maintenance in case where the margin has been placed on the root surface.
