Change Trajectory As Early As Possible

The tooth #20 of a 55-year-old lady has endo-perio disease, associated with pain on mastication with the opposing implant supported bridge (Fig.1).  The canal proves to be obliterated after 1st trial of retreat (Fig.2).  It remains obliterated on 2nd trial.  After discussion, she agrees with extraction and immediate implant.  It appears that osteotomy should be distal to the socket (Fig.3 red).  When the tooth is extracted, the socket is found to be curved distal (Fig.4).  It seems necessary to be corrected by starting osteotomy on the mesial slope (Fig.5 red, Fig.6).  Effort is exerted on changing the upper portion of drill/reamers (Fig.7: 3x17 mm) and tap (Fig.8: 4.5x17 mm).  New osteotomy is created distally until 4.5x17 mm tap (Fig.9).  In fact there is communication between the old and new osteotomy.  When a 4.5x17 mm implant is placed, it enters the old osteotomy (Fig.10).  After using a 4x17 mm drill in the new osteotomy a little deeper, the implant is placed in a more ideal position (Fig.11). 

In fact the osteotomy should be corrected as early as possible.  After withdrawing the pilot drill (Fig.12 black), remove distal crestal bone (Fig.13 green area) and initiate a new osteotomy (Fig.13 red).

If osteotomy follows the original socket, the depth could be less to reduce the chance of neuropathy.

Examination of the extracted tooth reveals subgingival calculus (Fig.14, guarded or poor prognosis unless perio surgery is performed) and blocked or bifurcated apical canal (Fig.15, 16 lateral projections; B: buccal).

CBCT Study of the tooth #20 of a 48-year-old man shows sudden narrowing of the canal apically (Fig.17, 18 (sagittal and coronal sections, respectively), the basis of difficult RCT.  The root and canal also curve distally, the pass that RCT and osteotomy should follow (Fig.17).   The Inferior Alveolar Canal/Mental Foramen is buccal to the apex of the tooth with 8 mm clearance (Fig.19).  If the osteotomy is placed lingually, a 4.5x20 mm implant may not violate the nerve, but may perforate the lingual plate (Fig.20 <).  A shorter implant (4.5x17 mm) would be safer.  There is no sign & symptom of postop paresthesia of this case.

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Xin Wei, DDS, PhD, MS 1st edition 06/29/2016, last revision 07/10/2016