inferior alveolar nerve lateralization in severe atrophic mandible

inferior alveolar nerve lateralization

1. Dr. Pouyan Sigari Oral and Maxillofacial Surgeon Inferior Alveolar Nerve Repositioning

2. 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 . 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 . This procedure raises the risk of neuropathies , such as paresthesia, hypoesthesia, and anesthesia of the IAN . the most popular surgical technique for IAN repositioning was IANT.

3. Indications 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 with extrusion of the antagonist tooth and reduced prosthetic free space. Class V or VI of Cawood and Howell with presence of interforaminal teeth (patients were not candidates for interforaminal implant-prosthetic methods). Class V or VI of Cawood and Howell if the patient desires a fast implant-prosthetic rehabilitation with predictable outcomes . 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.

4. Contraindications 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 cortical bone 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.

5. The decision whether to use IANT or IANL depends on the amount of stretching that is needed in order to mobilize the IAN.

6. S tretching the nerve by 10 - 17% of its original length may result in disruption of the nerve fibers internally. As a summary of both surgical techniques (IANT and IANL), it can be concluded that IANL produces less side effects than IANT.

7. The advantages of the IANL and IANT Longer implants can be placed in the same surgical step. Greater primary implant stability is provided thanks to the possibility of bicortical mandibular fixation. Possibility of placement of a greater number of implants , which improves the overall strength of the final prosthesis . 4. Possibility for simultaneous placement of implants during surgery, which allows a reduction in treatment time compared with other techniques as bone grafts . 5. The option for immediate loading for the enhancement of masticatory function, dramatically improving the patient’s quality of life. 6. The evaluation values for implant survival rates are similar to those for standard implantation procedures. 7. 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 .

8. The disadvantages of the IANL and IANT I t does not recover alveolar ridge anatomy . I t 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 . T hreaded implants in close contact with the nerve may cause neurosensory problems. I t is best performed under a general anesthesia to eliminate patient movement and to maximise access . The initial stability will depend only on the marginal cortical bone (Bruxism). P otential risk for osteomyelitis .

9. Neurosensory Complications H ypoesthesia (partial loss of sensitivity) P aresthesia (abnormal response to stimuli) H yperesthesia (hypersensitivity to all stimuli, except for special senses) T ransient anaesthesia and numbness, as well as temporary or permanent dysfunction of the lower lip and chin (loss of sensation of its terminal incisive branch) IANT is likely to be the most traumatic manoeuvre for the nerve Vascular damage can also jeopardise nerve function and recovery and may also cause loss of sensibility The process of nerve regeneration after compression or less severe crush injuries usually requires several weeks to 6 months ; if there is no sensory recovery during this time, permanent loss of continuity in the nerve trunk should be expected

10. case 58 yr male CC: lt mandibular jaw pain during mastication C lear PMH 5 yrs ago

11. E xt and implantation at the same time T his pano: 1 yr after surgery

12. 2023 follow up without any neurosensory disturbances immidiate paresthesia after surgery : 3 weeks

13. case 52 yr female PMH: antidepressants 4 yrs ago

14. P ersistant paresthesia after 4 yrs

15. Inferior alveolar nerve repositioning surgical techniques and outcomes− a systematic review J Stomatol Oral Maxillofac Surg 125 (2024) 101631 Thirty-three articles were reviewed, including a total of 899 patients , and approximately 950 IAN repositioning procedures. This systematic review was conducted following PRISMA guidelines (Preferred Reporting Items for Systematic review and Meta-Analysis). All follow-up periods lasted at least six months . The mean age of the included patients was 52.54 year-old , ranging from 19 to 82 year-old . The maximal distance between the alveolar ridge and the IAN considered to propose IAN repositioning varied from 5 mm to 8 mm  The included studies could be divided into 3 groups: studies focusing on IANL (n = 14), studies focusing on IANT (n = 13), and studies focusing or comparing both techniques (n = 6).

16.  Dental i mplants were placed generally simultaneously except for a few patients in some studies with a total of 2342 dental implants placed. Dental implant survival rate ranged between 86.95% and 100%  Among the patients who underwent IANT , there were 93% immediate neurosensory disturbance, and 15% persistent neurosensory disturbance at the end of the follow-up. Among the patients who underwent IANL there were 93% immediate neurosensory disturbance, and 6% persistent neurosensory disturbance at the end of the follow-up.

17. Other Complications Infection and mandibular osteomyelitis . C orporeal fractures and crestal fractures. I ntraoperative hemorrhage  Mandibular fractures were the most frequent of these serious complications  occurred between 10 days to 4 weeks following surgery. When the IAN is positioned lingually , removal of the buccal plate may significantly fragilize the mandible , causing these fractures .   Another factor which may explain these fractures is the bicortical anchorage. This caused several authors to advocate inferior border preservation .

18. Discussion Implant survival rate seemed higher for IANL procedures (99%) than for IANT procedures (95%). Since dental implants are inserted in strong cortical bone, often with a basilar anchorage, it could be inferred that most of the implants loss occurred in the early stages before osseointegration . This result is comparable with short dental implant survival rate ( 96% survival rate for ≤ 6 mm implants according to Ravida et al), and with dental implant survival rate in augmented bone ( 94.5% according to Chiapasco et al, or 95.3% according to Nissan et al).  Dursun et al did not show any significative difference regarding marginal bone loss between standard implants placed in association with IAN repositioning and short implants .

19. The main morbidity following IAN repositioning was IAN neurosensory disturbances . M anipulation of the IAN and old age are known risk factors of neurosensory disturbances. M ost studies found no differences between male and females . I mmediate neurosensory disturbance occurrence in 93% of the cases, ranging from 60% to 100% of the patients.  The significant morbidity was persistent neurosensory disturbances, caused by severe nerve trauma (neurotmesis), which must be avoided.  IANT was associated with twice more (15%) persistent neurosensory disturbance when compared to IANL (6%).  IANT should be considered only for patients with an edentulous or devitalized anterior sector.  many studies reported a high satisfaction of patients even in presence of residual neurosensory disturbances.

20. While IAN manipulation is the main cause of neurosensory distur - bances , it may also occur due to nerve trauma during implant place- ment or due to direct contact between the IAN and sharp implant thread. M any authors advocate the interposition of a biologic barrier to avoid direct contact between the IAN and the implants, such as a collagen membrane  . BUT: T he use of such interposition has not shown any significant difference regarding the neurosensory outcome or the implant survival in recent clinical studies, suggesting that interposition was uneffective in neurosensory disturbance prevention .

21. N erve trauma may occur during the osteotomy . The study that compared burs versus piezosurgery found less neurosensory disturbances when using piezosurgery (10,5%) versus burs (25%), albeit this result was not statistically significant .

22. Conclusion IANT and IANL are reliable techniques allowing safe dental implant placement in atrophic posterior mandible with high patient satisfaction . IANL seems to cause less persistent neurosensory disturbances compared to IANT and should be favored.