This case by Clint Taura, DDS is a wonderful example of how a sectional matrix secured inside a Greater Curve band can provide an excellent subgingival seal and isolation.
Endodontically treated 2nd molar has a very deep subgingival prep at the mesial.
Greater Curve Standard band surrounds the molar. A sectional matrix is slipped within the Greater Curve matrix at the mesial. This not only provides an excellent seal, it also shapes the composite into a more ideal configuration.
Build up composite bonded within the cavity prep.