Lingual Osteotomy vs. Mental Loop
Immediately preop PA shows that the length of the residual root of the lower left 2nd bicuspid is ~13 mm (Fig.1). The corresponding immediate implant can be 12 or 14 mm in length. There is ~ 5 mm to the Inferior Alveolar Canal (IAC: red dashed line). Osteotomy (Fig.3: O) is initiated in the lingual wall of the socket (S) after extraction. The 1st intraop PA is taken with a parallel pin (Fig.2). A 4.1 mm tap placed at the depth of 14 mm appears to be safe (Fig.4). When a 4.5x14 mm implant is placed, IAC is hardly identifiable (Fig.5). Careful examination reveals that the tip of the mental loop overlap the apex of the implant (Fig.6 blue dashed line). Worry increases recalling Inferior Alveolar Nerve Block is administered before fully placing the implant to the depth. In fact no paresthesia is reported by the patient the following morning. It is possible that lingual implant placement (Fig.7 green area) avoids violation of the mental loop (Fig.3 L). The overlapping mentioned above may be caused by angulation of X-ray projection (Fig.7 arrow).
In contrast, straight placement is more likely associated with mental loop injury (Fig.8). The corresponding overlapping shown by panoramic X-ray is really worrisome (Fig.9).
It would be the safest to place an implant shorter than the original root length and lingually.
The patient returns for immediate provisional reline and recementation 9 days postop. The socket has healed.
The patient returns with the loose provisional 1 month postop (Fig.10). The easy dislodgement appears due to multiple missing teeth and short vertical height (Fig.11). Early final restoration is necessary. The cemented abutment is re-torqued to 35 Ncm. The distobuccal margin is extended apically (Fig.10 <) and impression is taken. Next project is in the lower right sextant. Ortho starts 15 months post cementation of #20 crown.
Return to Lower Bicuspid
Xin Wei, DDS, PhD, MS 1st edition 03/20/2015, last revision 08/11/2016