Change in Trajectory

Immediately preop reanalysis of CT shows that there may be palatal thread exposure at #14 when a 4.5x14 mm tissue-level implant is placed equigingival (Fig.1,2).  After sinus lift with IS 4x10 mm dummy implant with guide, the tissue-level tap and implant placed free hand look deep (Fig.3,3').  CT reveals possible 3 palatal threads exposed (Fig.4,5 arrowheads), which is associated with change in trajectory due to the palatal shift of the apex of the implant (arrow), as compared to the design of the bone-level implant (Fig.6).  When there is a slope in the ridge and/or sinus floor, do not shift implants and use the guide for implant placement.  If switching is necessary, use a final drill without underprep (Fig.7 red) through the sinus floor after sinus lift to avoid apical implant deviation. To fix the palatal thread exposure, palatal flap is raised.  In fact the implant has to be removed for the incision.  When the implant is re-placed deeper by ~ 1mm, there is a thread exposed.  Bone graft is placed with collagen membrane.  As a 4.5x3 mm abutment is placed, the implant is found to be unstable.  Periodontal dressing is applied.  In fact the implant exfoliates with the abutment 4.5 months postop (Fig.8).  Bone graft seems to be necessary (sticky bone).  Tissue level implant should be avoided for patient with poor oral hygiene.  Return to Upper Molar Immediate Implant, Trajectory II 3 Xin Wei, DDS, PhD, MS 1st edition 08/30/2019, last revision 05/18/2020