Systemic Approach to Detect Inferior Alveolar Nerve Injury Intraoperatively

The nervous patient requests Nitrous Oxide inhalation when she returns for #18 extraction and immediate implant.  There is no bony defect involving buccal or lingual plates.  Osteotomes and Lindamann bur are used to section the thin septum mesiodistally.  Osteotomy is established in the septum, slightly deeper than the apex of the socket.  While increasing the diameter of the osteotomy, the patient feels pain.  Xylocaine 34 mg, Marcaine 9 mg, Epinephrine 26 mcg is added in an infiltration manner.  In fact this is a potential mistake.  From that moment on, it is possible that the anesthesia is so deep that the patient may not tell when the Inferior Alveolar Canal (IAC) is violated.  The only comfort is that there is excessive hemorrhage intraop.  The most important step to miss is to use explorer to detect the integrity of the osteotomy.

The 1st intraop PA is taken with a 4.5x14 mm tap in place (Fig.1 T) .  It appears that the osteotomy is ~ 2 mm apical to the apex of the socket (^; apical diameter of the tap is ~ 3 mm).  It is difficult to distinguish the superior border of the IAC.  The tap is unstable and the osteotomy is lingual.  After the bone is removed from buccal aspect of the osteotomy, taps are not stable until 7x14 mm at the depth of 11 mm.  A 7x11 mm implant (Fig.2 I) is placed with stability.  It is about 2 mm apical to the apex of the socket (^) and seems to be on the top of the IAC.  Radiolucency apical to the implant (*) is probably due to osteotomy by drill or reamers.  Immediately postop panaramic X-ray does not reveal the relationship of the implant at #18 to the IAC (Fig.3).  Clinically, compared to the bone level at the septum, the implant should not touch the IAC.

In summary, if there is 3 mm between the apex of the socket and the IAC, immediate implant should be aborted or approached cautiously and systemically.  When the patient feels pain during osteotomy, administer a half carpule of 2% Xylo: 1:100,000 Epinephrine or nothing and proceed carefully, paying attention to the level of drill against a reliable landmark.  After each step of osteotomy, check the apical end of the osteotomy with a long-shanked explorer whether there is perforation or not.  Measure the depth carefully, particularly immediately prior to implant placement.  Use bone-level implants more often, using the crestal bone as the most reliable landmark.

Apparently new bone forms 2 months postop (Fig.4 *, or bone graft).  A Ziroconia crown is cemented nearly 6 months postop.  A thick dense layer of bone forms distally around the first 1-3 implant threads 13 months post cementation (Fig.5 *).  Note there is no occlusal function.

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Xin Wei, DDS, PhD, MS 1st edition 10/30/2015, last revision 05/04/2017