The placement depth of the implant at #13 has to be adjusted multiple times until satisfaction (Fig.2-5). <: exposed thread.  The mesial crestal bone is trimmed with bone profile drill at #13 before placement of a 5.5x6 mm healing abutment.   The implant at #14 is infected and loosened 1.5 months postop; after its removal, the sinus floor is absent without membrane perforation; the large defect with basically intact buccal and palatal walls is grafted (Fig.6 *).  Four to five months later, use the same guide and drill sequence until 3.5x7.3 mm drill.  Insert a 4x10 mm dummy implant to the 2nd line of 12 mm offset and take 5x5 cm CT to determine the diameter and depth of a final implant. Use healing screw.  Depth Last Next Xin Wei, DDS, PhD, MS 1st edition 09/20/2019, last revision 09/21/2019