Submandibular Gland Fossa

The submandibular (gland) fossa, or lingual (L) concavity (Fig.1 <), is more pronounced in the lower 2nd molar (7) that that of the first (6) (Fig.1 vs.2, 4 vs.3, the same patient).  The lingual concavity may be mild (Type I, <2 mm depth, Fig.9-11), moderate (Type II, 2-3 mm,  Fig.1,4, 12) and severe (Type III, >3 mm, Fig.13,14 (same patient)).

Fig.5 is an illustration, showing the socket after extraction (from Fig.1).  The red circle in Fig.5 represents the lingual artery, which is the 2nd branch from the external carotid artery.  When the lingual artery is severed by an overdrilling bur, it shrinks toward the external carotid artery.  Hemostasis is difficult to achieve without emergency surgery.  Failure to recognize the proximity of the lingual concavity may lead to perforation of the lingual plate while osteotomy is forming (Fig.6 red arrow) and potentially damage the lingual artery in the submandibular fossa.  Although CBCT is essential for recognition of this special anatomy, a surgical technique is the most critical step to avoid the injury.  That is to use two fingers (Fig.7 blue circles) to hold the buccal and lingual plates as low as possible and let the tactile sense guide you and keep the osteotomy in the middle of the ridge (pink arrow).  One of the fingers may sense the vibration before perforation of the lingual plate.  Use a long explorer to probe the osteotomy site after each bur.  A surgical stent is also helpful.  If an immediate implant is placed, the osteotomy should be initiated in the buccal wall of the socket of the 2nd molar (Fig.7). For the 1st molar of this case, the osteotomy is to be placed slightly lingual (Fig.8 (an illustration from Fig.2) pink arrow), since the buccal bone is lower than the lingual (Fig.2 <) and especially on the affected side (root fracture) (Fig.3).

In addition, it is important to control the depth of the osteotomy.  For freshly healed socket and immediately post-extraction socket, it should be safe to place a 11 mm long bone-level (Fig.15,16) or 14 mm gingival level (Fig.13,18) implant or less.  For the same length, it appears safer to use a tapered implant (Fig.9,13,18) than cylindrical one (Fig.15,16).

http://www.osseonews.com/perforated-the-lingual-cortical-plate-expect-complications/

http://www.osseonews.com/radiolucency-just-drilling/

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Xin Wei, DDS, PhD, MS 1st edition 04/13/2014, last revision 04/15/2014