Place 9 mm Long Implant with Much Bone Graft

Extraction shows the large distal socket (Fig.1 D) and the thin and low septum (*) of the tooth #30.  After Magic Split test confirms hard bone, osteotomy is initiated with 1.6 mm pilot drill with 11 mm stopper (Fig.2); there is 2.7 mm distance to the Inferior Alveolar Canal.  Following Marking Bur, a 4.8 mm Magic Drill is used to finish the osteotomy with difficulty because of hard bone and ineffective local anesthesia due to infection.  A 5x9 mm "dummy" implant is placed to determine the placement level relative to the distal crest (Fig.3 *).  After removal of the dummy implant, an authentic one with the same dimension is placed with packing abundant allograft (.5-1.5 mm) and Osteogen (Fig.4 *); it appears that 4 to 5 threads (fins) of the implant (arrowheads) are engaged to the native bone for primary stability (>40 Ncm).  Later more bone graft is placed distally (Fig.5 arrow).  With the short implant placed not so deep, there is 6-7 mm clearance from the underlying canal (Fig.6).  The patient is doing well 7 days postop (Fig.7).  He feels that the provisional is too bulky buccally for the first 2 days postop.  The buccal margin will be trimmed in another 2 weeks (dashed line).  The patient in fact masticates on the right side postop.  By the time he returns for provisional revision 1 months 10 days postop, he has mild pain.  There is food entrapment.  The provisional and the abutment are slightly loose, whereas the implant is stable with healing socket (Fig.8).  A healing abutment is placed.  The implant appears unstable nearly 5.5 months postop.  The gap between the bone and implant seems to be large (Fig.9).  The implant should have been larger and longer for fast healing.  A healing screw is used instead.  The site heals 10 months postop with an increase in bone density around the implant (Fig.10.)  Prior to cementation of the final crown, the abutment is minimally exposed (Fig.11 (6.5x5.7(3) mm)).  In fact the abutment screw becomes loose 2 months post cementation (1 year postop); it appears that crown/implant ratio is unfavorable (Fig.12).  The implant is slightly placed mesially (cantilever).  The patient cannot chew on the left.  The tooth #19 is periodontally affected and the tooth #18 is missing.  When bone loss is severe, the implant should be as large as possible and preferably tissue-level. The abutment screw is re-loosening 1.5 years post cementation (4 months post #19 socket preservation, Fig.13).  The crown/implant ratio at #31 is more favorable than that at #30 (compare black lines).  The crown at #31 has large contact area with the tissue-level implant (external), whereas the contact between the abutment and the bone-level implant is much less (internal).  To prevent the abutment screw re-loosening (turning) in function, a screw driver (Fig.14 D) will be buried inside the crown/abutment after the screw is retightened.  Make sure that the driver is in the middle of the access hole.  Section the driver in situ obliquely (Fig.15); flat sectioning allows the driver to turn with the abutment screw in function.  After insertion of plumber tape around the sectioned screw driver, use composite to fix the driver in place and seal the access hole (Fig.16).  Occlusal check suggests weak link between the abutment and bone-level implant at #30.

Return to Lower Molar Immediate Implant, Prevent Molar Periimplantitis (Protocols, Table), IBS, #7, 14,18,19

Xin Wei, DDS, PhD, MS 1st edition 10/04/2016, last revision 03/03/2019