Short Implant for Lower 2nd Molar

A 52-year-old lady has lost 5 lower posterior teeth (Fig.1 CBCT 3D image), which are restored by quadrant (LL).

Fig.2 (sagitttal section) shows that the bone height at the site of #31 is shorter than that of #30.  There is a 1 mm separation from the Inferior Alveolar Nerve (brown) if a 8 mm implant is placed at #31 (Fig.2,3 (coronal section)), whereas 3 mm separation for a 6 mm implant (Fig.4).  Since the tooth #2 is supraerupted, the shorter implant at #31 is more appropriate.  It is placed a little deeper (Fig.4' arrow) so that the abutment or the opposing tooth does not need to be trimmed too much.  In addition, choose a widest abutment (purple, e.g., 7.8 mm) with the shortest cuff (pink, 1 mm).   A splinted immediate provisional will be fabricated to prevent the gingiva from growing into the abutment margin.  At restorative phase, a smaller abutment will be used (e.g., 5.8 mm) so that the gingiva is clear from the margin.  It will be easy for impression.  Then the provisional will be relined to keep the gingiva from growing into the space just created by changing abutments.  Bone graft will be needed buccal to the implant at #31 (Fig.3,4 red circle; L: lingual).

A coronal section at the site of #30 confirms that a 12 mm implant is safe (Fig.5).

Initial height at #30 and 31 will be 12 and 8 mm after infiltration anesthesia.  Osteotomy at #31 is proceeded cautiously.  If the 1st intraop PA confirms depth safety margin, depth will be 2 mm more than implant length so that the implant will be placed lower.

Impression has been taken for diagnostic wax up and surgical stent.

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Xin Wei, DDS, PhD, MS 1st edition 08/16/2015, last revision 06/16/2016