Subcrestal Placement or Not

Fig.1 is a diagrammatic illustration of a coronal section of an upper 1st molar, in which B and P represent buccal and palatal sockets, while S septal bone.  * represents the corresponding crest.  It is safe to place an implant (green cylinder) subcrestal in the septal bone (no bone graft necessary, Fig.2), but the implant/crown ratio is unfavorable.  In contrast equicrestal or slightly supracrestal placement is acceptable whether the buccal plate is present (Fig.3) or not (Fig.4 (red outline: buccal gingiva)) as long as the implant plateau is ~3 mm subgingival.  The apical portion of the buccal and palatal sockets is filled with alloplastic/collagen plug (purple oval), while the coronal portion of the sockets with mixture of autogenous bone (harvested from osteotomy) and allograft (blue circles).  The space between the implant plateau and the gingival margin is occupied and closed with an immediate abutment and provisional.  The buccal gap (horizontally, between the soft tissue and implant) should be 2-3 mm or more for the bone graft.

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2Xin Wei, DDS, PhD, MS 1st edition 12/29/2018, last revision 12/30/2018