A Limiting Factor for a Large Immediate Implant

To achieve primary stability and reduce bone graft, immediate implant for a molar should be as large as possible.  There are 2 limiting factors: sex and implant position.  Female molar socket is relatively smaller.  When an implant is placed or leaned too buccally or lingually, a smaller one has to be used.  It requires the operator to know local anatomy (e.g., bony undercut) and pathology (buccal plate defects) prior to osteotomy and make appropriate intraop adjustment.  Today's case shows failure to determine mesiodistal trajectory of osteotomy early can also lead to placing a smaller implant than the site indicates.

A 42-year-old lady has chronic periodontitis.  There is bone loss around the tooth #3 (Fig.1,2).  CT shows that an implant to be placed can be as large as 8x17 mm (Fig.3,4).  After extraction, sequential osteotomy is carried out free hand.  The first intraop PA is taken quite late in osteotomy (no PA is taken with a parallel pin).  When a 4.5x17 mm tap is inserted 14 mm deep; it shows that the apical end of the tap is close to the roots of the tooth #2 (Fig.5), although its coronal end is in the middle of the edentulous area (red lines).  The position and trajectory of the osteotomy is changed without effect (Fig.6: 6x17 mm tap). Osteotomy cannot be enlarged further.  A 6x14 mm implant is placed with large peri-implant gap (Fig.7 *).  A fair amount of bone graft is placed in the gap (Fig.8,9 *).  The margin of the immediate provisional has to be wide (extra portion between Fig.10 black and white arrowheads) to hold the graft in place (Fig.11,12).  The patient is doing well postop, although she reports discomfort when she bites with the provisional.  The latter disappears gradually.  By 5.5 months postop, there has been apparently bone growth in the mesial gap (Fig.13 arrowheads).  The provisional is relined and acrylic being added to the occlusal surface so that there is enough clearance to correct the cross bite between #2 and 31 (Fig.14).  In fact the teeth #1 and 32 are also in cross bite and treated by limited ortho.

Cross bite between #2 and 31 is corrected in 3.5 months (Fig.15); the provisional is trimmed short so that the teeth #2 and 31 are going to intruded against each other as well as occlusal equilibrium.  Fig.16 is taken immediately before #3 implant crown impression to show that cross bite is corrected with normal vertical height (4.5 months post banding).  Panoramic X-ray is taken 4 months post cementation of #3 crown (Fig.17, 14.5 months postop).

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Xin Wei, DDS, PhD, MS 1st edition 02/15/2015, last revision 04/29/2017