The purpose of this first part of a two-part series was to review the literature concerning the indications, contraindications, advantages, disadvantages and surgical techniques of the lateralization and transposition of the inferior alveolar nerve, followed by the placement of an implant in an edentulous atrophic posterior mandible.
A comprehensive review of the current literature was conducted according to the PRISMA guidelines by accessing the NCBI PubMed and PMC database, academic sites and books. The articles were searched from January 1997 to July 2014 and comprised English-language articles that included adult patients between 18 and 80 years old with minimal residual bone above the mandibular canal who had undergone inferior alveolar nerve (IAN) repositioning with a minimum 6 months of follow-up.
A total of 16 studies were included in this review. Nine were related to IAN transposition, 4 to IAN lateralization and 3 to both transposition and lateralization. Implant treatment results and complications were presented.
Inferior alveolar nerve lateralization and transposition in combination with the installation of dental implants is sometimes the only possible procedure to help patients to obtain a fixed prosthesis, in edentulous atrophic posterior mandibles. With careful pre-operative surgical and prosthetic planning, imaging, and extremely precise surgical technique, this procedure can be successfully used for implant placement in edentulous posterior mandibular segments.
Tooth loss is one of the common causes of reduced quality of life in adults. Dental implants have become a widely accepted treatment option for patients with both partially and complete edentulous posterior mandibles. Rehabilitation of edentulous posterior mandibular regions with severe ridge atrophy using implants is subject to anatomical, surgical and biological difficulties and poses a challenge to dental teams [
In the posterior mandible, the bone quality may not be as good as it is in the anterior mandible. In particular, if shorter implants are used to ensure that there is no encroachment on the nerve canal, initial implant stability will be unicortical. In addition, there is a risk to the IAN as the operator tries to maximise implant length on the basis of measured available bone height. The advantages of IANT include the ability to place longer fixtures and to engage 2 cortices for initial stability [
IANL and IANT are surgical procedures that reposition the IAN for the purpose of implant placement without bone augmentation. The buccal cortex surrounding the MC is removed to allow IAN repositioning. This procedure raises the risk of neuropathies, such as paresthesia, hypoesthesia, and anaesthesia of the IAN [
IANL is defined as the lateral reflection of the IAN without incisive nerve traction (preservation of the incisive nerve and lateralization of inferior alveolar neurovascular bundle posterior to the mental foramen) [
During the IANT procedure, a corticotomy is done around the mental foramen and the incisive nerve is transacted (incisive neurovascular bundle is sacrificed), to allow transposition of both the mental foramen and the IAN such that the mental foramen is repositioned more posteriorly [
The first case of IAN repositioning was reported by Alling (1977) [
The review is registered in international prospective register of systematic reviews ‘PROSPERO’ [
Registration number: CRD42015016265.
The review included studies, case reports, clinical trials on human subjects that were published in English between January 1997 and July 2014, and included a minimum of 6 months of follow-up. Letters and PhD theses were excluded, as well as abstracts and reviews and studies on animals.
The information source was the MEDLINE (NCBI PubMed and PMC) database and other scientific electronic sources.
According to the PRISMA guidelines, an electronic search was conducted using the MEDLINE (NCBI PubMed and PMC) database to locate articles concerning IAN lateralization or transposition and implant placement in an edentulous atrophic posterior mandible. The search terms used were: “INFERIOR ALVEOLAR NERVE LATERALIZATION”, “INFERIOR ALVEOLAR NERVE REPOSITIONING“, “INFERIOR ALVEOLAR NERVE TRANSPOSITION”, “IMPLANTS IN ATROPHIC POSTERIOR MANDIBLE + REPOSITIONING”, “INFERIOR ALVEOLAR NERVE TRANSPOSITION + MENTAL”, “IMPLANTS IN ATROPHIC POSTERIOR MANDIBLE + LATERALIZATION”, “IMPLANTS IN ATROPHIC POSTERIOR MANDIBLE + TRANSPOSITION”, “MANDIBULAR ATROPHY + REPOSITIONING”, AND “INFERIOR ALVEOLAR NERVE + MINIMAL BONE HEIGHT”.
Due to the low number of relevant articles and to ensure the sensitivity of the systemic review process, articles were searched from January 1997 to July 2014. Bibliographies of the selected articles were also manually searched. Titles derived from this broad search were independently screened by two authors based on the inclusion criteria. Disagreements were resolved by discussion. Full reports were obtained for all the studies that were deemed eligible for inclusion in this paper.
PRISMA flow diagram.
Inclusion criteria for the selection were:
Articles regarding to IANL and IANT procedures;
All articles in English;
Clinical reports with minimum 6 months follow-up;
Information regarding implant osseointegration and survival;
Studies on adult (between the ages 18 and 80) human beings, with no immunologic diseases, uncontrolled diabetes mellitus, osteoporosis, or other contraindicating systemic conditions.
Exclusion criteria for the selection were:
Clinical reports with no minimum 6 months of follow-up;
Not enough information regarding the selected topic;
No information regarding implant osseointegration and survival;
Studies on animals;
Studies of patients with immunologic diseases, uncontrolled diabetes mellitus, osteoporosis or other contraindicating systemic conditions;
Studies of adolescents (under 18 years of age) and elderly people (over 80).
Article review and data extraction was performed according to a PRISMA flow diagram (
The search displayed 876 results from the NCBI PMC and PubMed databases, and 3 results from other sources (dental-tribune.com, acta.tums.ac.ir, hindawi.com/journals). A total of 879 search results were screened. Preliminary exclusion was made by duplication and relevancy (n = 841). A total of 38 titles and abstracts were selected according to relevancy after the removal of duplications. Exclusion was made by information amount regarding selected topic (n = 12). Twenty-six articles were examined. Another exclusion was made based upon follow-up time (n = 6) and information regarding implant osseointegration and survival (n = 4). Finally, 16 articles were included in the systematic review. Data was included for 160 patients.
Studies of adult human beings between 18 and 80 years of age with minimal residual bone above the MC, in which IANL and IANT + implant placement had been performed, were selected.
Data was independently extracted from reports in the form of variables according to the aim and themes of the present review as listed below.
The review aims to achieve the following:
To describe the purpose (indications and contraindications) of IANL and IANT.
To describe the current surgical techniques used for IANL and IANT with simultaneous implant placement.
To describe the advantages and disadvantages of the IANL and IANT procedures.
Risk of bias (e.g., lack of information or selective reports on variables of interest) was assessed at the study level. The risks were indicated as lack of precise information of interest in each individual study that can blind the reader from particular information about the examined samples. The Cochrane Collaboration tool for assessing risk of bias [
The search displayed 876 results from the NCBI PMC and PubMed databases, and 3 results from other sources (dental-tribune.com, acta.tums.ac.ir, hindawi.com/journals). A total of 879 search results were screened. Preliminary exclusion was made by duplication and relevancy (n = 841). A total of 38 titles and abstracts were selected according to relevancy after duplications removal. Exclusion was made according to information amount regarding selected topic (n = 12). Twenty-six full-text articles were in the end, assessed for eligibility. During the eligibility stage, articles that did not meet the inclusion and exclusion criteria where filtered as follows: no minimum 6 months of follow-up (n = 6) and no information regarding implant osseointegration and survival (n = 4). In the end, 16 articles that included data on 160 patients were utilised for the systematic review (
A total of 16 studies were included in this review. Nine were related to IANT, 4 to IANL and 3 to both IANT and IANL (
Description of studies included in the review
Study | Year of publication | Procedure performed | Number of patients |
---|---|---|---|
Lorean et al. [1] | 2013 | Transposition and repositioning | 57 |
Morrison et al. [2] | 2002 | Transposition | 12 |
Kan et al. [3] | 1997 | Lateralization | 10 |
Transposition | 5 | ||
Peleg et al. [4] | 2002 | Lateralization | 10 |
Khajehahmadi et al. [5] | 2013 | Lateralization | 10 |
Transposition | 11 | ||
Dal Ponte et al. [13] | 2011 | Transposition | 1 |
Vasconcelos et al. [14] | 2008 | Transposition | 1 |
Suzuki et al. [15] | 2012 | Lateralization | 1 |
Chrcanovic et al. [16] | 2009 | Transposition | 15 |
Proussaefs [17] | 2005 | Transposition | 1 |
Ferrigno et al. [18] | 2005 | Transposition | 15 |
Kan et al. [19] | 1997 | Transposition | 1 |
Karlis et al. [20] | 2003 | Transposition | 1 |
Proussaefs [21] | 2005 | Transposition | 1 |
Barbu et al. [24] | 2014 | Lateralization | 7 |
Del Castillo Pardo et al. [26] | 2008 | Lateralization | 1 |
The Cochrane Collaboration bias summary for potential bias was used to assess the quality of studies and identify papers with intrinsic flaws in method and design [
Assesment of the risks of bias
Study | Implant osseointegration was not |
Random |
The operation |
---|---|---|---|
Lorean et al. [1] | + | - | + |
Morrison et al. [2] | - | - | + |
Kan et al. [3] | + | - | + |
Peleg et al. [4] | - | - | - |
Khajehahmadi et al. [5] | - | + | + |
Dal Ponte et al. [13] | - | + | - |
Vasconcelos et al. [14] | - | + | - |
Suzuki et al. [15] | - | + | - |
Chrcanovic et al. [16] | - | + | - |
Proussaefs [17] | - | + | - |
Ferrigno et al. [18] | - | - | - |
Kan et al. [19] | - | - | - |
Karlis et al. [20] | - | - | - |
Proussaefs [21] | - | - | - |
Barbu et al. [24] | - | - | - |
Del Castillo Pardo et al. [26] | - | - | - |
Results of individual studies of implant treatment using are shown in
Results of individual studies
Study |
Number of |
Number of implants placed | Number of implants lost | Implant survival rate | Method of implant osseointegration evaluation | Results |
---|---|---|---|---|---|---|
Lorean et al. [1] |
68 - IANL |
232 | 1 | 99.57% | Not mentioned | One implant loss was observed during follow-up period (average 20.62 months). |
Morrison |
20 - IANT | 30 | 0 | 100% | Panoramic X-ray | All 30 implants had successfully integrated. No evidence of infections, wound dehiscences, fractures or other serious complications. |
Kan et al. [3] |
10 - IANL |
64 | 4 | 93.8% | Not mentioned | Four of 64 implants had been removed. Two implants were lost due to infection after the patient had sustained a mandibular fracture. Two other implants were lost due to non-integration. |
Peleg et al. [4] | 10 - IANL | 23 | 0 | 100% | Panoramic X-ray | All implants were clinically osseointegrated. |
Khajehahmadi |
28 - IANT | 65 | 0 | 100% | Panoramic X-ray | All implants survived and were subject to prosthodontic treatments. No evident of failure with at least 1 year of follow-up. |
Dal Ponte |
1 - IANT | 2 | 0 | 100% | Panoramic X-ray | On 2 and 7 years follow-up panoramic X-rays visible good osseointegration of implants without abnormality. |
Vasconcelos |
1 - IANT | 2 | 0 | 100% | Panoramic X-ray | Seven months after surgical procedure revealed excellent results. |
Suzuki et al. [15] | 1 - IANL | 2 | 0 | 100% | Panoramic X-ray | In the postoperative period of 6 months, satisfactory results have been shown as regards to soft and hard tissues wound healing and temporary prosthetic rehabilitation. |
Chrcanovic |
18 - IANT | 25 | 3 | 88% | Panoramic X-ray | Three implants did not integrate. |
Proussaefs [17] | 1 - IANT | 2 | 0 | 100% | Perio-Test Unit | The implants appeared clinically osseointegrated. Three years post-loading revealed no clinical signs of pathosis (i.e., mobility, probing depth < 3 mm, pain, BOP) |
Ferrigno et al. [18] | 19 - IANT | 46 | 2 | 95.7% | Clinic and radiographic examination | Two implants were lost (early failure). One implant was lost due to non-integration. Another implant was lost due to a mandibular fracture. |
Kan et al. [19] | 1 - IANT | 3 | 2 | 33.33% | Panoramic X-ray | Three weeks after implants placement the patient experienced a spontaneous right mandibular fracture involving two anterior implants, which were finally removed. |
Karlis et al. [20] | 1 - IANT | 2 | 2 | 0% | Panoramic X-ray | Panoramic X-ray revealed an area of radiolucency around the most posterior right implant with a non-displaced linear fracture through the inferior mandibular border. Finally, both implants were removed. |
Proussaefs [21] | 1 - IANT | 5 | 0 | 100% | Perio-Test Unit | Implants appeared clinically osseointegrated 6 months after implant placement (tested with Perio-Test, Siemens, Bensheim, Germany). Implants were restored with cement-retained PFM restorations. Three years post loading X-ray examination revealed minimal marginal bone loss (< 1 mm). |
Barbu et al. [24] | 11 - IANL | 32 | 0 | 100% | Panoramic X-ray | No implant loss was observed during the follow-up. |
Del Castillo |
1 - IANL | 3 | 0 | 100% | Panoramic X-ray | Six months after implants placement, no complications were observed. |
IANL = inferior alveolar nerve lateralization; IANT = inferior alveolar nerve transposition.
From the results of individual study data (
The study of number selected articles [
The major reason for using this technique is to prevent IAN injury during implant placement in edentulous posterior atrophic mandibles.
Class IV, V, or VI of Cawood and Howell [
Class V or VI of Cawood and Howell [
Class V or VI of Cawood and Howell [
In orthognathic surgeries, such as lower border shaving and total mandibular subapical osteotomy.
In the pre-prosthetic surgery.
In the anastomosis and repairing of a disrupted IAN.
Preservation of IAN in cancer surgery in the posterior mandible.
When placement of short implants is not a viable option (in case of severely atrophic mandibles when the residual bone above MC ranges between 0.5 and 1.5 mm).
Less than 10 - 11 mm bone height above the canal, when the quality of the spongy bone does not provide sufficient stability for implant placement.
If the mandible presents advanced resorption of the alveolar process.
If the patient has poor general health, including systemic diseases that may worsen the patient’s health condition after the IAN reposition procedure.
Limitations in accessing the surgical site.
The patient is susceptible to infection or bleeding.
The patient has thick corticalybone buccally and a thin neurovascular bundle.
People who become easily stressed out and are over sensitive even towards the smallest surgical complications. Such patients do not have tolerance and compatibility skills and, therefore, are not good candidates for nerve transposition surgery.
The preoperative work-up included an assessment of the IAN using appropriate diagnostic records, such as a panoramic radiograph, a computed tomography (CT) scan, casts, diagnostic wax-up, and surgical templates. During preoperative consultation with the patients, the risk of postoperative neurosensory disturbances (ND) that can result following the IAN repositioning is discussed. This possibility gives many patients pause to consider the ramifications of the procedure. To help the patient decide whether this would be tolerable, the clinician can perform a preoperative block with a long-acting local anaesthetic, such as Marcaine, which reproduces symptoms lasting 8 to 16 hours that are similar to the postoperative anaesthesia the patient may experience [
Inferior alveolar nerve (IAN) replacement division into two distinct surgical procedures, i.e. transposition and lateralization; the steps are outlined below [1]
IAN transposition | IAN lateralization |
---|---|
1. Buccal/lateral bone window | 1. Buccal/lateral bone window |
2. Complete osteotomy of the mental foramen | 2. Partial osteotomy of the mental foramen distal portion |
3. Micro-dissection of the IAN | 3. Maintaining the integrity of the incisive nerve |
4. Incision of the incisive nerve | 4. Gentle buccal traction of the IAN |
5. Repositioning of the IAN |
5. Replacement of the IAN on the implant surface |
6. Incorporation of the IAN into the buccal flap |
PRF = platelet-rich fibrin.
An osteotomy is performed at the mental foramen, drilling around the orifice to obtain a ring of external cortical bone. A window also may be made about 5 mm ahead of the foramen, in order to avoid damaging the nerve over its anterior loop. An en bloc osteotomy is then made at the external cortical level, or a posterior window is performed in the external cortical layer along the intrabony trajectory of the nerve (
Intraoperative photographs showing inferior alveolar neurovascular bundle transposition. A = before transposition; B = after transposition (courtesy of Dr Dainius Razukevicius, “Kauno Implantologijos Centras” Kaunas, Lithuania).
Then, with the nerve fully lateralized, the dental implants are placed under direct visualisation - in this case bicortically, taking advantage of the mandibular basal layer. Once the implants have been positioned, the vestibular cortical layer is replaced in those cases where an osteotomy has been performed, or the nerve is passively positioned against the implants in those cases where cortical drilling has been carried out. In either case, the emergence of the nerve becomes more distal [
In this case, neither dissection of the terminal branches of the IAN nor sectioning of the incisor branch is needed. The technique involves the preparation of a cortical bone window (via osteotomy or drilling) that is located posterior to the mental foramen [
Intraoperative photography showing the inferior alveolar neurovascular bundle lateralization (courtesy of Dr Dainius Razukevicius, “Kauno Implantologijos Centras” Kaunas, Lithuania).
Schematic drawing showing the inferior alveolar neurovascular bundle transposition (A) and lateralization (B).
Bone is removed using a round bur number 700 or 701, a straight handpiece and copious normal saline for irrigation or a piezosurgery device [
Some studies recommend piezosurgery for bone removal in nerve transposition surgery. This device causes vibrations in the range of 20 - 200 μm and cuts through the mineralized tissue completely and smoothly. If soft tissue or the neurovascular bundle comes in contact with this device, it stops functioning because it is designed to stop working when it contacts unmineralized tissue. This device is especially beneficial when a small osteotomy is going to be performed. Among the disadvantages of this device are the long duration of time that it takes to remove bone. Also, there remains controversy regarding the indications of piezosurgery devices, and some believe that the vibrations they generate may damage the nerve. Further investigations are required regarding indications of using piezosurgery devices in nerve transposition surgery [
Before this phase, the surgeon should decide whether or not to place materials between the implant and the inferior alveolar neurovascular bundle. The preference is to place a collagen membrane or bone material between the implant and the inferior alveolar neurovascular bundle. A potential advantage of bone over a membrane is that, if proper healing occurs in the area, the contact area of implant and bone will increase. Before releasing the inferior alveolar neurovascular bundle from the elastic band, the mentioned material must be inserted between the neurovascular bundle and implant. This way, the inferior alveolar neurovascular bundle will be in a vent that is medially adjacent to the implants and covered by the mucoperiosteal flap. Alternatively, the inferior alveolar neurovascular bundle may be left to lie passively outside of the MC [
The bone defect is then covered by several methods: repositioning the bony window that was removed or the bony window can be crushed and mixed with an allograft or xenograft. The area is then sutured.
Antibiotic and corticosteroid prophylaxis is recommended because of the extensiveness and duration of surgery. Using corticosteroids pre- and post-operatively helps diminish the symptoms. However, there is no consensus in this regard; since inflammation can be among the causes of nerve dysfunction, corticosteroid therapy can be beneficial [
Longer implants can be placed in the same surgical step.
Greater primary implant stability is provided thanks to the possibility of bicortical mandibular fixation. This technique avoids the need for additional radiation-intensive and costly imaging studies. Simple panoramic radiography and clinical examination are all that are required.
Possibility of placement of a greater number of implants, which improves the overall strength of the final prosthesis.
Possibility for simultaneous placement of implants during surgery, which allows a reduction in treatment time compared with other techniques as bone grafts that require a long waiting period before implant insertion together with additional surgeries.
The option for immediate loading for the enhancement of masticatory function, dramatically improving the patient’s quality of life.
The evaluation values for implant survival rates are similar to those for standard implantation procedures.
As a biomechanical advantage, IAN transposition presents an increase in resistance to occlusal forces and promotes a good proportion between the implant and the prosthesis.
In addition, with this procedure, all of the following are accomplished:
restoration of the correct vertical dimension;
occlusal stability;
chewing efficiency;
prevention of tissues atrophy;
replacement of dentures;
stabilisation of the anterior dentition;
temporomandibular joint and masticatory muscle balance.
One of the disadvantages of this procedure is that it does not recover alveolar ridge anatomy [
Another negative point of this procedure is that it temporarily weakens the mandible due to removal of cortical bone; which, in combination with implant placement, may lead to mandibular fracture at the operation site [
The initial stability will depend only on the marginal cortical bone. The most common failures are due to bruxism and poor occlusal relations; therefore, patients with bruxism or poor occlusal relations make, implant stability and survival to less favourable. An additional disadvantage for such operations is the potential risk for osteomyelitis [
The main limitations of this review were that six authors [
Inferior alveolar nerve repositioning is a technique that has been used for more than 20 years with good survival and survival rates. This is sometimes the only possible procedure to help patients to obtain a fixed prosthesis, especially in edentulous atrophic posterior mandibles. There are two main techniques for inferior alveolar nerve repositioning that are relatively safe and offer a high survival rate: inferior alveolar nerve lateralization and inferior alveolar nerve transposition. Increased protection of the neurovascular bundle is afforded during implant placement. Inferior alveolar nerve lateralization and transposition in combination with the installation of dental implants offer advantages, such as reducing the risk of inferior alveolar nerve damage. With careful pre-operative surgical and prosthetic planning, imaging, and extremely precise surgical technique, this procedure can be successfully used for implant placement in an edentulous atrophic posterior mandible.
The authors report no conflicts of interest related to this study.