The shield associated with the closed technique is exposed nearly 2 months postop (Fig.7), while the one associated with the open technique is not (Fig.8).  The upper portion of the gingiva is concave with the open technique, since the hard tissue support is absent. 切开虽然可能减少术后感染，但是软硬组织萎缩多。

Open & Closed Last Next Shield  Xin Wei, DDS, PhD, MS 1st edition 11/30/2019, last revision 02/21/2021