From September 2013 to December 2015, ten patients with posterior edentulous areas in the mandible underwent lateralization of the inferior alveolar neurovascular bundle and subsequent implant placement at the Department of Oral and Maxillofacial Surgery, Bharati Vidyapeeth University, Dental College and Hospital, Pune. All patients were assessed for incidence, magnitude and duration required for recovery from NDs using Semmes–Weinstein monofilaments (SWM).

In addition to routine investigations required for surgical intervention, orthopantomogram (OPG) and cone beam computerized tomography scan (CBCT) were carried out for diagnosis and treatment planning (Fig. 3).

This study was approved by the Research Academy and Ethical Committee of the Institute.

This prospective study included ten patients above the age of 18 years with an edentulous span in mandibular posterior region. It was necessary for the distance from alveolar crest to inferior alveolar nerve ≤ 8 mm (CBCT) to be included in the study. Only patients opting to place dental implant for prosthetic restoration were included. None of the patients had systemic conditions precluding minor oral surgical procedures (Fig. 4).

Semmes–Weinstein monofilaments are calibrated nylon monofilaments used to measure the patient’s ability to sense a point of pressure. A set of 5 Baseline Tactile SWM Set filaments were used (2.86, 3.61, 4.31, 4.56, and 6.65) for the evaluation. They generate a precise amount of stress over the area of application. The higher the value of the monofilament, the stiffer and more difficult it is to bend. In our study, we used monofilament to evaluate incidence, magnitude and duration of NDs (Fig. 5).

In the preoperative evaluation procedure, the patient was seated comfortably with his eyes closed to eliminate visual input. The filaments were applied perpendicular to the skin with enough force to cause the monofilament to buckle for approximately 1 s. The evaluation was carried out at predetermined 3 points based on the running course of mental nerve for obtaining standardized and comparable results. Readings were obtained for the proposed surgical side as well as the contralateral side which would serve as a control (Fig. 6).

The surgical procedure was done under local anesthesia (IAN, Lingual and Long buccal nerve blocks). The incision began from the retromolar region and was carried forward to the mesial portion of the cuspid tooth area, where a vertical relaxing incision was made. A full thickness mucoperiosteal flap was reflected. Mental nerve bundle was located and secured using a specially fabricated instrument (nerve retractor).

For the purpose of IAN lateralization, the corticotomy marking was done. The corticotomy started 3–4 mm distal to the mental foramen and extended in a distal direction, 1.5–2 cm distal to the provisional implant position. A small round bur in a straight hand piece with high torque and copious amount of sterile isotonic saline irrigation was used to prepare the corticotomy site. Only hand instruments such as small curettes and spoon excavators were used to remove the trabecular bone and gain access to the neurovascular bundle. The IAN was mobilized from its position and released from the canal using a specially fabricated instrument. After the complete release from the canal, the inferior alveolar nerve was lateralized completely and held in position till accomplishment of immediate implant placement.

Pilot drill was used to determine desired location of the implant placement using a prefabricated stent. After completion of the osteotomy with last implant drill, the implant was inserted while protecting the nerve bundle. Implant of longer length (11.5–13 mm) was inserted ensuring that the apical ends of the implants were positioned inferior to the canal. Once the implant was in its final position, the nerve was left back over the lateral aspect of the implant. The autogenous bone-graft obtained from the corticotomy was mixed with Tricalcium phosphate hydroxyapatite (TCP-HA) crystals and placed at the osteotomy site to fill the defect. Suturing was done to achieve primary closure.

The suitable medications were prescribed to the patient. Methylcobalamin was prescribed to the patient for 4 weeks, although its usefulness in nerve recovery is debatable. Patient was recalled on the first postoperative day, and radiographs were made.

The postoperative analysis of NDs was done using SWM filaments as described earlier. Readings were made on the 1st and 7th postoperative day and every month thereafter until the neural sensations were restored.