Although the previous studies reported good results concerning ND in IAN transposition surgery, the methods for evaluating ND differed, and most of the studies did not fully describe the evaluation procedure. The evaluation of ND of the IAN can be performed by purely subjective (questionnaire), relatively objective (static light touch, 2-point discrimination, etc.), and purely objective methods (trigeminal somatosensory evoked potential, blink reflex method, etc.). It is well known that there are discrepancies in the assessment results for nerve impairment between the subjective and objective methods. In the present study, only one patient complained of neurosensory disorder, while five out of six patients had ND if assessed by the objective method (SW test and Highet grading).

In cases where ND was judged by clinical assessment, the presence or absence of ND would be influenced by the evaluation criteria. In the studies by Rosenquist, Ferrigno et al., and Fernandez Diaz and Naval Gias, a patient who presented a 2-point discrimination capability below 14 or 15 mm was considered normofunctional [7, 8, 10]. In our study, if the patient was assessed according to the same criteria (Highet grading of ≥3+), six out of seven (85.7 %) operative sides were considered normofunctional. Our results showed ND rates after IAN lateralization similar to those reported by the studies described above. In the present study, the quality of ND was evaluated by Highet grading; according to this grading, complete recovery (grade 4) was obtained only on two operative sides and weak hypoesthesia (grade 3+) was observed on four operative sides. These results suggest that although the neurosensory function of the IAN was restored to almost normal levels over a period of time after IAN lateralization surgery, a weak or negligible degree of ND remained in some patients, which could be identified only by objective evaluation methods.

In this study, although two patients reported slight disturbance and one patient complained of ND, all patients were satisfied with the results of restoration by dental implant insertion. Hashemi reported that in his study, 82 of 87 patients were satisfied with the results of nerve lateralization after 1 year [9]. It was suggested that subjective reports of perceived sensory changes are initially overestimated, but may be underestimated as the postoperative time interval increases. It is possible that patients adapt or become accustomed to what they consider “normal” over time [15]. It is possible that a weak impairment of IAN function remains after IAN transposition in some patients. However, the impairment is negligible, and the patients may become accustomed to it.