A New Classification of Inferior Alveolar Nerve Repositioning Procedures for Dental Implant Placement

Abstract

Background: Tooth loss significantly impacts the quality of life for adults. Inferior alveolar nerve (IAN) repositioning has garnered interest as a treatment for facilitating dental implant placement in the severely atrophic posterior mandible. However, there remains a need for standardization and classification of these techniques to improve outcomes. This study aims to propose a new clinical classification system for IAN repositioning procedures based on anatomical and procedural parameters. Methods: This study retrospectively analyzed preoperative radiographic records and surgical procedure documents over a 15-year period (2008-2023) for patients who underwent implant placement combined with IAN repositioning in the posterior atrophic mandible. Cases were classified into four categories according to bone availability, nerve location, and type of surgical intervention. Results: The study analyzed 142 edentulous posterior mandibles in 105 patients (77 women, 28 men; age range: 20-75). The cases were divided into four categories: Category 1 (58 patients, 78 sites), treated with one surgery; Category 2 (15 patients, 15 sites), treated in two stages; Category 3 (20 patients, 25 sites); and Category 4 (12 patients, 24 sites), with Categories 3 and 4 treated in a single surgery. Across all 132 sites, 411 dental implants were placed and restored with implant-supported fixed prostheses. Conclusions: This proposed classification provides a structured systematic framework for assessing and planning IAN repositioning procedures. It facilitates better diagnosis, treatment planning, and prediction of surgical stages in patients needing IAN repositioning for dental implant placement.

Keywords: atrophic mandible; bone grafts; dental implants; inferior alveolar nerve.

Figure 1

The residual ridge bone dimensions that should be evaluated when planning treatment for patients undergoing IAN repositioning procedures. Patient categorization was based on these dimensions.

Figure 2

Illustrative case for Category 1. (a,b) Radiographic views showing a partially edentulous left posterior mandible with a straight ridge contour at the crest, good mandibular height, width and angulation (c) An intraoperative view of IAN transposition via a buccal window and placement of three implants. (d) An intraoperative view showing the repositioning of the IAN within the mandible. (e) The particulate bone substitute and resorbable membrane covering the surgical site. (f) The BFFG for primary closure. (g) Postoperative radiographic view. (h) Rehabilitation with a fixed prosthesis over the implants.

Figure 2

Illustrative case for Category 1. (a,b) Radiographic views showing a partially edentulous left posterior mandible with a straight ridge contour at the crest, good mandibular height, width and angulation (c) An intraoperative view of IAN transposition via a buccal window and placement of three implants. (d) An intraoperative view showing the repositioning of the IAN within the mandible. (e) The particulate bone substitute and resorbable membrane covering the surgical site. (f) The BFFG for primary closure. (g) Postoperative radiographic view. (h) Rehabilitation with a fixed prosthesis over the implants.

Figure 3

Illustrative case for Category 2. (a) A radiographic view of a partially edentulous right posterior mandible. (b) A CBCT view showing a narrow mandibular ridge with horizontal deficiency. (c,d) Radiographic views after bone grafting, demonstrating significant bone gain (e) An intraoperative view showing the bone graft before removing the fixation screws, alongside IAN transposition. (f) Intraoperative views depicting the placement of three implants and the repositioning of the nerve. (g,h) BFFG was used to enhance primary soft tissue closure. (i,j) Rehabilitation with a fixed prosthesis over the implants. (k) Cross-sectional CBCT views showing the implants and the new bone volume. (b, marked in yellow, indicates the buccal side).

Figure 3

Illustrative case for Category 2. (a) A radiographic view of a partially edentulous right posterior mandible. (b) A CBCT view showing a narrow mandibular ridge with horizontal deficiency. (c,d) Radiographic views after bone grafting, demonstrating significant bone gain (e) An intraoperative view showing the bone graft before removing the fixation screws, alongside IAN transposition. (f) Intraoperative views depicting the placement of three implants and the repositioning of the nerve. (g,h) BFFG was used to enhance primary soft tissue closure. (i,j) Rehabilitation with a fixed prosthesis over the implants. (k) Cross-sectional CBCT views showing the implants and the new bone volume. (b, marked in yellow, indicates the buccal side).

Figure 4

Illustrative case for category 3. (a,b) Radiographic views showing moderate mandibular bone dimensions. (c) IAN transposition via buccal window access. (d) Placement of two implants combined with an onlay bone block. (e,f); The use of a buccal fat free graft (BFFG) for primary closure of the grafted site. (g) Postoperative radiographic view. (h) The implant uncovering stage; note the thick soft tissue.

Figure 5

Illustrative case for Category 4. (a) Fully edentulous mandible with extreme atrophy. (b) A CBCT view showing a severely atrophied mandibular basal bone with a superficially located nerve. (c) An intraoperative view highlighting the superficial position of the mental nerve and the superior placement of the IAN at the crest. (d) Access to the IAN was gained from the superior portion of the crest. (e) Superior repositioning (Superioralization) of the IAN. (f) Implant placement through the onlay bone block, with repositioning of the IAN beneath the graft (Roofing technique). (g) Application of a BFFG at the recipient site to enhance primary soft tissue closure and augment soft tissue volume. (h) Postoperative radiographic view.

Figure 6

Distribution and summary of patients, treated sites, and implants by category. (a) Distribution of patients by category. (b) summary of patients, sites, and implants.