Dr. Eddie Scher offers a protocol for operating more safely in the posterior mandible



In 1992, Gunne and colleagues published their paper on implants in partially edentulous patients (Gunne J et al, 1992). This important article compared bridges solely supported by implants with bridges supported by implants and natural teeth. This longitudinal study used mandibular bilateral free-end saddle cases with implants being placed in the posterior mandible. The study report admitted that 39% of the implants placed caused some form of nerve damage.

This article forced me to consider developing a protocol for operating safely in the posterior mandible (Scher E, 2002). The first step of the protocol must be to diagnose and treatment plan the case carefully, using normal two-dimensional radiography (accurate panoramic x-ray and long-cone x-ray) to decide on the length of the implant (Larheim T, Eggen S, 1979).
The width of the ridge can be determined by ridge mapping (Wilson DJ, 1989). It can also be determined by direct view, if one has to enter the area for the extraction of the root, the removal of pathology, or a bone-grafting procedure.
If there is any doubt whatsoever, then a computed tomography (CT) view should be taken to determine the exact position of the inferior dental (ID) nerve (Figures 1 and 2).

Finally, study models are, of course, essential to make sure it is possible to restore the implants placed in the ridge (Figure 3).

Protocol to place implants safely in the posterior mandible
1. The most important decision: know when to say “no,” after careful diagnosis and treatment planning.

2. Use a crestal incision. This allows the clinician to make a transmucosal connection, as well as give the incision line the best blood supply (Cranin AN, 1992). Being transmucosal, we also have the option of backing the implant out during the first week after surgery, if the patient develops a nerve problem.

3. Use local infiltration anesthesia only (on a sensible patient!)—this allows the operator to make an incision without pain. There will also be no pain when drilling the osteotomy site. If, however, one comes to within approximately 2 mm of the ID nerve, then the patient will perceive a sensation and can warn the operator immediately. This is a safety mechanism that occurs in only 5% of cases, provided that the diagnosis and treatment planning are accurate.

4. Take an x-ray after you have prepared two-thirds of the osteotomy site’s depth (Figure 4). The operator can then double-check that the site is being prepared as planned. This x-ray can be taken in totally sterile conditions by using a long-cone x-ray technique, and by placing the digital sensor in a sterile plastic tube.

5. There must be enough vertical room to drill the site; can the patient open wide enough? Careful measurements must be taken to ensure that the operator has enough room for the handpiece, the spade drill, and the use of a surgical template.

6. Finally, an anti-inflammatory like dexamethasone (6.6 mg in 2 mL IM or IV) is useful to dissipate blood that might cause hydraulic pressure, formed by the compression of an accurately placed implant into a bleeding osteotomy site (Hag M et al, 1985; Misch CE, Moore P, 1989).

New techniques in guided surgery enable us to place implants accurately and safely in the posterior mandible to the nearest 0.5 mm to 1 mm, but the patient must be able to open even wider than is needed for the techniques described earlier.
Operating in the posterior mandible always carries risks, about which we must fully inform our patients. However, by following a protocol such as the one outlined here, we can minimize the risks involved, and help ensure a predictable and satisfactory outcome for the patient.

Bio
Eddie Scher, BDS, LDS RCS, MFGDP, is a specialist in oral surgery and prosthodontics. He is a visiting professor of implantology at the Temple University School of Dentistry, Philadelphia.

References

Cranin AN, Klein M, Sirakian A, et al (1991) Comparison of incisions made for the placement of dental implants. J Dent Res 70:279 [Abstract 109].

Gunne J, Âstrand P, Ahlén K, et al (1992) Implants in partially edentulous patients. A longitudinal study of bridges supported by both implants and natural teeth. Clin Oral Implants Res 3(2):49-56.

Elhag M, Coghlan K, Christmas P, et al (1985) The anti-inflammatory effects of dexamethasone and therapeutic ultrasound in oral surgery. British J Oral Maxillofac Surg 23(1):17-23.

Larheim TA, Eggen S (1979) Determination of tooth length with a standardized paralleling technique and calibrated radiographic measuring film. Oral Surg 48:374-378.

Misch CE, Moore P (1989) Steroids and the reduction of pain, edema and dysfunction in implant dentistry. Int J Oral Implantol 6(1):27-31.

Scher EL (2002) Risk management when operating in the posterior mandible. Implant Dent 11(1):67-72.

Wilson DJ (1989) Ridge mapping for determination of alveolar ridge width. Int J Oral Maxill Implants 4(1):41-43.