There are two reasons for failure of the surgical guide: failure to trim the tooth #9 distal (minor palatal guide displacement, Fig.5) and deflection of pointed drill and 2.2 mm drills over the hard palatal plate slope (Fig.6).  To avoid this complication, the pointed drill should be done free hand initially, after incision and obliquely (Fig.7).  The guide is placed to finish the rest of osteotomy if deem to be appropriate.  With Lindamann bur to adjust the position of the new osteotomy twice, the last drill (2.0 mm) apparently starts to perforate the apical portion of the buccal plate.  The perforation seems to enlarge when the mini implant is re-placed (Fig.8 (green area) <30 Ncm).  With Vanilla graft (Fig.8 pink circles) and abutment height adjustment (Fig.4), a provisional is fabricated with occlusal clearance.

From Guide to Free-hand Last Next Guided Surgery Xin Wei, DDS, PhD, MS 1st edition 09/24/2018, last revision 10/18/2018