nerve injury and specifically trigeminal nerve injury is known as a potential risk of many surgical procedures in the oral cavity in general [ 17 , 23 , 30 ] . usually after oral implant rehabilitation
, the patient expects and experiences significant improvements , not only regarding jaw function , but also in relation to dental , facial , and even overall body image .
one can perfectly understand that the patient does not accept neural side effects , which might compromise his well - being .
following the definitions of the subcommittee on taxonomy of the international association for the study of pain 1986 , the types of sensorial disturbances are principally anesthesia , paresthesia , or dysesthesia .
sensory disturbances in the maxillofacial region could be associated with different surgical procedures , like placement of endosseous implants [ 3 , 36 , 37 ] . with regard to immediately loaded implants , the presence of postoperative sensory disturbances was not documented .
branemark et al .   developed a new approach for immediate loading using fixed prosthesis of prefabricated standard components in the edentulous mandible .
this technique involves a flattening of the jaw crest , followed by the placement of the implants by means of prefabricated and thus not individualized surgical guides .
thus the distances ( but not the depth of drilling ) between the implants were always the same , considerably reducing the variation of the surgical procedure . sometimes the distal implants were positioned near the mental foramen .
damage to the mental nerve may result in loss of tactility and thus biting on the tongue or lip , drooling , painful sensations , and also interference with several jaw functions such as mastication , speech , hygiene maintenance , and social or psychosexual well - being .
different methods were used to evaluate such sensory disturbances after the placement of dental implants .
ellies   in 1992 and ellies and hawker   in 1993 published two retrospectives studies based on the analysis of questionnaires .
applied in a prospective study a self - administrated questionnaire and the somatic questionnaire , the hopkins symptoms checklist ( hscl ) .
the latter is a questionnaire routinely used in psychology to estimate a patient s psychoneurological and/or psychosomatic discomfort .
the somatic score of the hscl was oriented on physical complaints and shows the level of a patient s perception of his / her physical state .
the higher the somatic score ( i.e. , 25% in the study of wismeijer et al . ) , the more the patient tends to exaggerate physical complaints , but the risk of a sensory disturbance of the lower lip is a possible complication after implant surgery .
analyzed the neurosensory disturbances in a population of patients after oral implant placement , using a combination of psychophysical methods like soft brush , two - point discrimination , pain perception , and temperature sensitivity . a small number ( 8/94 ) of patients experience altered sensation after the placement of mandibular endosseous implants , but no permanent alteration was found .
walton   published a prospective study of 75 subjects using one objective ( the light touch sensation ) test , associated with a subjective analysis ( questionnaire ) ; both methods were used before and after placement of two implants in the anterior mandible . in this study , 24% of subjects reported neurosensory disturbances in the short term after implant surgery in the anterior mandible , but the problem appears to be a transient one with only about 1% experiencing sensation changes 1  year after implant surgery .
after reviewing the related literature , it is clear that the proportion of patients with sensory disturbances varies among publications .
it is therefore essential to assess if neurosensory changes take place after the immediate loading of oral osseointegrated implants in the edentulous mandible in patients who received a fixed prosthetic construction on the day of implant insertion or the next day .
distinguishing between dysesthesia , an unpleasant abnormal tactile sensation , and paresthesia , an abnormal ( not painful ) and often decreased sensation , is the first step in defining the character of the neurosensory disturbance reported by a patient .
further differentiation between paresthesia and hypoesthesia , which is a reduction in the level of sensation , and finally anesthesia , the complete absence of any sensation , is important from all viewpoints . in the presence of dysesthesia
, the differentiation must be established between spontaneous and a stimulus - induced unpleasant sensation . the clinical approach and sometimes legal implications of these different conditions
besides clinical evaluation , it must be understood that evaluation of nerve injuries such as demyelinization due to compression ( neuropraxia ) , distal wallerian degeneration with intact cell tubes ( axonotmesis ) , or proximal and distal wallerian degeneration with disparate schwann cell tubes ( neurotmesis ) is an impossible mission for the clinician .
nevertheless , if no spontaneous return of tactile sensibility is noted within 36  months , the permanent loss of continuity of some or all the elements of the nerve trunk should be expected [ 11 , 27 ] .
some observations indicate that the return to normal tactile sensibility may even occur after 2 to 3  years .
such methodology is clinically helpful and is a good basis for more detailed and objective evaluations .
immediate loading of oral implants was proposed as an alternative protocol in the rehabilitation of partially or fully edentulous patients .
surprisingly enough , no study has yet referred to the possible different neural sensibility when loading is imposed immediately after or together with the placement of the implants .
this tactile sense aspect is relevant especially if we consider that the prosthetic rehabilitation ( implying by example a full occlusal contact ) is functional within one or a few hours after the implant placement .
thus , the patient s awareness of the load imposed on the implants can be a key issue to avoid undue load transfer on the implant  bone interface .
the overall aim of the present research is to objectively evaluate the neurosensory disturbances and/or function occurring after placement of oral implants in the anterior region of the mandible .
this study comprised a total of 65 patients ( age range 3084  years , mean age 58  years ; 30 women ) .
all patients were treated by means of immediately loaded implants in the anterior mandible with the brnemark novum system approach .
surgery took place at the department of periodontology , catholic university leuven ( 55 patients , 3 surgeons ) , and at the department of oral and maxillofacial surgery , erasmus hospital , free university of brussels ( 10 patients , 2 surgeons ) .
selection criteria included ( 1 ) placement of implants in the anterior mandible using brnemark novum system ( nobelbiocare ab , gothenburg , sweden ) ; and ( 2 ) no history of neurological disorder .
an ad hoc multiple choice questionnaire ( 13 questions ) was designed to record past and present neurosensory disturbances in these patients .
the clinical history of the patient was used , and according to the selection criteria , a self - administered questionnaire was sent out to the 65 patients .
the questionnaire was sent by mail to the patients with the request to complete it and return it to the clinic .
the questionnaire was designed by experienced periodontologists , prosthodontists , and one psychologist ( see appendix for the questionnaire ) .
the answers to the questions were analyzed and data were collected by this same team . an objective evaluation took place after analysis of the questionnaire . during this evaluation
the clinical evaluation of trigeminal nerve injuries suggested by zuniga and essick   in 1992 was used as basis in the test and control population . a psychological test : the scl-90-r ( symptom checklist-90-revised ) was applied .
the scl-90-r is different from the hscl because it considers a broader area of psychopathology .
it reveals the global level of recent psychological and also physical dysfunction . in the present study ,
the scl-90-r scale reveals complaints , loaded with a general feeling of physical dysfunction , as a result from functional problems .
after completion of the questionnaire , each patient was interviewed using a standardized series of  key questions  on altered feeling in the chin , lips , tongue , and cheek . each time a distinction was made between the right and left sides of the face .
typical questions were as follows : 
 how would you describe the altered feeling?do you notice the altered feeling constantly or only when touching the area , or chewing , or talking?is it painful ? where ?
transient or constant?does it start spontaneously or is it evoked by touching , chewing , or speaking?what exacerbates the pain?what relieves the pain ?
do you notice the altered feeling constantly or only when touching the area , or chewing , or talking ?
does it start spontaneously or is it evoked by touching , chewing , or speaking ? what exacerbates the pain ? what relieves the pain ?
after thorough questioning about the patient s general and oral medical history , an extra- and intraoral clinical examination took place , including palpation and/or percussion , to detect eventual provoked pain at the site of injury .
finally , inspection of the oral cavity was performed to find eventual evidence of nerve injury , self - induced trauma , etc . in the present study three psychophysical tests
were selected : two - point perception at the lower lip , both left and right side ( fig . 
1 ) ; thermal sensitivity at the lower lip and gingiva of the anterior lower jaw , both left and right side ( fig . 
2 ) ; and light touch sensation at the lower lip and gingiva of lower jaw , both left and right side ( fig . 
3light touch sensation ( semmes - weinstein aesthesiometer ) instrument two - point discrimination instrument thermal sensitivity instrument light touch sensation ( semmes - weinstein aesthesiometer ) instrument psychophysical tests demand a thorough consciousness and active participation of the patients and a quiet environment .
a combination of both psychophysical tests with testing tools adapted to the intraoral and perioral sites were used .
the light touch sensation on the other hand was tested using the original semmes - weinstein aesthesiometer ( stoeling company , wood dale , usa ) device . to determine the threshold level the staircase method was applied . in the light touch sensation and static two - point discrimination ,
finally , in the thermal sensitivity test , all subjects were tested with ten trials . for a more detailed methodology of the procedures for sensory testing , see jacobs et al . .
the collected data were statistically analyzed using the statistica for windows 5.1 ( stat soft , tulsa , ok , usa ) .
a mann  whitney u test was applied to the threshold levels in the test and the control groups .
fifty - eight of the 65 patients ( 89% ) completed the questionnaire and returned it to the hospital .
systemic diseases like cardiac , respiratory , endocrine , and renal diseases , allergic reactions , and psychological ( depression ) problems were detected in 46% ( n=30 ) of the patients .
the mean time between the placement of the implants and the reception of the questionnaire was 20  months ( range 840  months ) .
the analysis of the questionnaire showed that 33% ( n=19 ) of patients reported a kind of neurosensory disturbance after the placement of the implants ( range 824  months ) .
the age range of this subpopulation was between 30 and 71  years ( mean age 56 , 13 women ) .
the duration of this postsurgical neurosensory disturbance after the implant surgery was less than 3  months in 58% ( n=11 ) of the patients .
the most commonly affected sites in the 19 patients were the gingiva only ( 6 patients ) , the inferior lip only ( 4 patients ) , and the chin ( 4 patients ) .
one of the patients did not remember or could not determine the affected zone . speaking and drinking ( five patients )
an important part of the affected population group ( 12 patients ) did nt complain about problems with oral function or daily activity .
the most common reported sensation was numbness ( nine patients ) , followed by cutting , beating , and itching reported by two patients .
only one patient considered that the benefits of a fixed prosthesis did not outweigh the disadvantages that she had experienced as a result of disturbances in sensation of the lower jaw .
she considered that she would not have done this surgery again , if she had been informed beforehand about the potential sensory changes in the orofacial region .
from the 19 patients , 9 volunteered to participate in the objective evaluation ( test group ) .
the test group was 3071  years old ( mean age 56  years , seven women ) .
their age ranged from 49 to 71  years ( mean age 63  years , all women ) .
the mean observation time in this group since the surgery ( two implants placed in the anterior mandible after a two - stage protocol ) was 18  months ( range 1122  months ) .
as psychological test , the scl-90-r test was applied for symptom measurement of patient treatment outcomes and their degree of somatization of the symptoms .
the psychophysical tests included three neurosensory evaluations : two - point discrimination , thermal sensitivity , and light touch sensation .
an age- and gender - matched group of patients who had undergone similar surgery ( two implants in the symphyseal region ) in the same area , but without reporting sensory disturbances , served as control .
as mentioned above , each of the 19 patients of the self - declared affected population was invited for a clinical evaluation and 9 of the 19 patients accepted to participate .
the time span between surgery and psychophysical evaluation was on average 29  months ( range 1949  months ) . during the clinical interview , before the actual objective testing took place , none of the nine patients had remaining complaints or clinical symptoms such as drooling or tongue bite wounds that could indicate a sensory disturbance .
however , at the reception of the questionnaire , which had to be mailed after the examination session , five of the nine patients with self - declared neurosensory disturbances still reported having them . in the remaining four patients
the scores of the scl-90-r of the test ( n=9 ) and control group ( n=10 ) revealed no statistic differences , neither on the global scale of neuroticism , nor on the dimension of somatic complaints .
after clinical examination and considering the negative interview for unpleasant dysesthesia and pain , it was concluded that only potential signs of paresthesia were currently present in the affected patients .
two - point discrimination , thermal sensation , and light touch sensation at the gingival level show no significant difference between test and control groups ( table  1 ) [ 14 , 16 , 26 , 28 ] . 
 table  1overview of psychophysical tests scores between test group , control group , and reference valuestype test / regiontest groupcontrol groupreference valuesreference
numberts / llls0.8 ( cr)0.9 ( cr)0.8 ( cr)18ts / llrs0.9 ( cr)0.9 ( cr)0.8 ( cr)18ts / lgls0.8 ( cr)0.8 ( cr)0.8 ( cr)18ts / lgrs0.8 ( cr)0.8 ( cr)0.8 ( cr)182pd / llls3.4  mm4.5  mm6.13.1  mm193.31.6  mm2024  mm21 , 222pd / llrs3.4  mm4.8  mm6.13.1  mm193.31.6  mm2024  mm21,22lts / lgls7 nf6 nf4 ( 2.83 ) nf 19lts / lgrs7 nf7 nf4 ( 2.83 ) nf19ts thermal sensation , llls lower lip left side , llrs lower lip right side , lgrs lower gingiva right side , lgls lower gingiva left side , cr correct ratio , 2pd two - point discrimination , mm millimeters , lts light touch sensation , and nf the number of the filamentmean value of von frey hair overview of psychophysical tests scores between test group , control group , and reference values ts thermal sensation , llls lower lip left side , llrs lower lip right side , lgrs lower gingiva right side , lgls lower gingiva left side , cr correct ratio , 2pd two - point discrimination , mm millimeters , lts light touch sensation , and nf the number of the filament mean value of von frey hair the light touch sensation of the lower lip was significantly impaired in the test group ( mann  whitney u test ) .
there was a statistical difference for both sides ( p0.03 ) between test and control groups .
systemic diseases have a significant effect on the outcome of the light touch testing at the lower lip .
the light touch sensation of the lower lip revealed a statistical difference ( p0.04 ) for both sides .
the anterior region of the mandible was always considered as a  safe zone  for the use of oral implants .
nevertheless , there is an important difference between the reported implant success rate with specific surgical technique and the postsurgical changes to function , sensory mechanisms , and the physiological integration in the human body .
anatomical considerations in the anterior region of the mandible and the skills and experience of the surgeon are also important .
it is surprising to note that the present methodology allowed us to observe a very high percentage of subjective postoperative complaints .
these results are in agreement with others , i.e , ellies   with 37% and ellies and hawker   with 36% .
this high degree of concordance for the percentages of incidence is interesting , considering the different surgical techniques used and cultural and sometimes ethnic differences between the three involved populations ( canada , australia , and belgium ) .
it was not possible , based on the subjective data , to establish any correlation between the systemic diseases presented in the study population and the reported sensory disturbances ( i.e. , impairment of perception in a patient with diabetes ) [ 2 , 4 ] .
it is interesting to know that eight patients had the impression to be affected by some kind of persistent neurosensory disturbance , most probably paresthesia or hypoesthesia , more than 12  months after the surgery . nevertheless , besides these results
, a majority of these affected patients considered that the benefits outweigh this kind of transient or permanent disadvantages , and consider that they would accepted an implant surgery again even if they knew about the present complication .
as expected from the neuroanatomical knowledge recently collected , neurosensory disturbances regularly occur in the anterior region of the mandible after surgery .
anatomical factors like the presence of an anterior loop , handling of the mental nerve during surgery , or the perforation of the incisive nerve canal can all provoke such disturbances . as mentioned above
this procedure can be considered rather invasive and can damage , in severely resorbed jaws , the incisive canal or the mental nerve emerging at the crestal level .
the relationship between a reduction of the crestal jawbone and neurosensory disturbances could not be traced in the literature . however , bone chin grafting procedures present some similarities .
von arx et al .   recently reported 8.1% of neurosensory disturbances after 6  months in patients who underwent such procedures .
for some systemic conditions , it was reported that persons can be more prone to sensory disturbances .
peripheral neuropathy in people with scleroderma is thought to be rare , however , nerve conduction studies showed abnormalities in patients with a mean disease duration of 10  years or longer .
polyneuropathies in mild or severe diabetic patients often cause subclinical damage of the trigeminal nerve .
moreover , their sensory complaints in the perioral area often remain unnoticed and the dysfunction undiagnosed .
the younger the subject , the greater the degenerative response but the quicker and more complete the overall recovery .
tactile threshold assessment reveals that detection of monofilaments up to 0.023  g ( monofilament number 2 ) can be considered normal in the orofacial region [ 14 , 37 ] .
neurophysiological recordings of the masseter reflex , the mental nerve blink reflex , or evoked potentials are all useful in evaluating trigeminal nerve damage .
this was specifically shown for damage of the inferior alveolar nerve [ 19 , 32 , 33 ] .
however , evaluation of nerve damage in the symphyseal region was not reported in the literature .
the number of nerves innervating this region , the vicinity of interfering structures ( e.g. , tongue , saliva , and labial muscles ) , and anatomical variations make this a difficult but challenging task . in humans ,
several reports show that during the stimulation of peripheral sensory limb nerve examined after surgical repair ( time span between 5 and 20  years ) , the sensory function remained deficient and often included abnormal sensory disorders .
it must also be considered that the loss of tactile sensitivity after surgery is not always reflected in abnormal psychophysical test results .
furthermore , it is also possible , as shown by the collected data in this study , that an abnormal test result , particularly the light touch sensation test , does not reflect clinical reality . in other words ,
it should be stressed that the selection of a control group of patients treated by means of two implants in the symphyseal region was principally motivated by the intent to have an age- and gender - matched group .
the selection of a control group among patients treated with the novum system but without neurosensory complaints would not have allowed this .
it must also be considered that sometimes thresholds of the psychophysical test are not easy to reach in the oral cavity ; the devices were not originally designed for this region , particularly light touch sensation .
not less important is the fact that 95% ( n=17 ) of the affected population considers that the treatment benefits outweigh the transient disadvantages , and that 18/19 of the patients consider that they would follow an implant surgery again if they knew beforehand the changes in sensation after the surgery .
there are no data in literature to compare neurosensory disturbances after immediate loading with those after the two - stage protocol .
it is clear that it is difficult for the patient to distinguish between postoperative inconveniences , early functional adaptation , and real neurosensory dysfunction .
a meticulous preoperative planning of the surgery , even in an improperly so - called safe region of the jaws , like the symphyseal region , might avoid many neural disturbances . in this perspective , the use of cross - sectional images and the transfer of the planning to the operative field may be considered .
the use of a questionnaire to determine the presence or absence of a problem after a medical procedure is easy and inexpensive ; but to clarify the type , magnitude , extension , and eventual persistence of the neurosensory disturbance , the use of objective methods ( i.e. , psychophysical methods ) in the evaluation of a population affected by any sensory disturbance , when complaints are detected , is highly recommended .
the objective follow - up revealed that patients are often not impaired by , and even not aware of , neurosensory dysfunctions after implant surgery in the anterior mandible .
none of the patients suffering from this impaired tactile function seems to have functional deficits resulting from it .
based on these data , proper preoperative planning using cross - sectional imaging can be advised even for surgical procedures in the symphyseal region .
in the next pages you can find several questions about your implant surgery in the lower jaw .
the objective of these questions is to evaluate if you have or had an alteration of sensibility after the placement of the implants in the lower jaw . put an x before the correct answer .
please try to complete this questionnaire to the very best.1 ) after your implant surgery , did you experience a change in feeling or sensation of your lower lip , chin or gums?__yes__noif yes , please indicate _ _ lower lip _ _
chin _ _ gums if your answer was  no  , it is nt necessary to follow with the questionnaire .
thank you very much for your cooperation . if your answer for the question number 1 was  yes
2 ) if you have experienced a changed sensation in an area of the lower jaw was it temporary ( one day to several months ) or is it still present?__temporary__persistent  3 ) if the change was temporary , how long did it last?__<(less ) 1  week__612  months__14  weeks__>(more ) 1  year , please state how long _ _ _ _ _ _ _ _ _ _ 13  months__36  months  4 ) did the change in sensation of your lower jaw affect your ability to continue your daily routine?__yes__no  5 ) did the changed sensation affect your ability to perform any of the following activities?__speaking__tasting__eating__whistling__drinking__kissing__swallowing__other , please specify _ _ _ _ _ _ _ _ _ _ _ _  6 ) which side of your lower jaw is ( was ) affected?__right__both right and left sides__left__i do nt remember which side  7 ) which of the following words best describes the change in sensation you have experienced ( please select onlyoneword!))?__burning__tickling__hot__itching__prickling__numb__penetrating__frozen__cutting__prurience__tearer__electric__ardent__palpitation if you have selected one word of the left column please continue with this questionnaire .
if you have selected one word of the right column go to the question 12 . describing a pain or
you have a word on the left side and a word on the right side . between the words
you have a line . on the line you put a littlex[eks ] ( x ) in the zone most representative ,
in other words take the next question like a  thermometer  to measure the intensity of rain.8 ) the type of pain is ( or was):insupportable_________________________________________supportable  9 ) is this region disturbing during the night?__yes__no  10 ) do you occasionally take painkillers ( i.e. aspirins , paracetamol ) to control this pain ?
attention : the analgesics you took immediately after the placement of the implants must not be considered.__yes__noif so , which painkillers do you take ? _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ if your answer to question 10 was  no  do nt fill in the question 11.11 ) do these painkillers relieve your pain?__yes__no  12 ) did you feel that the benefits to your implant surgery outweigh the disadvantages you have experienced as a result of changes in sensation of your lower jaw?__yes__no  13 ) would you go through implant surgery again if you knew you would have the changes in sensation that you have experienced?__yes__no you have finished the questionnaire ; now please return the questionnaire by mail in the envelope that we have prepared for you
 the aim of the study was to assess past and present neurosensory disturbances using a questionnaire and a psychophysical approach in patients treated with immediate loaded implants in the edentulous anterior mandible . 
 a group of 65 patients ( age range 3084  years , mean 58  years , 30 women ) was enrolled . 
 all were treated by means of three immediately loaded implants ( branemark novum system ) . 
 a self - designed questionnaire was used for data collection . 
 the response rate was 89% . 
 of the 58 responders , 33% ( n=19 ) reported neurosensory disturbances after implant surgery . 
 nine of these patients ( mean age 56  years , seven women ) participated in an objective evaluation and were subjected to a psychological and several psychophysical tests . at the moment of the evaluation none of the nine patients still had clinical complaints . 
 psychological testing revealed no statistical differences between the patients , who had previously experienced subjective complaints , and the control group . 
 two - point discrimination and thermal sensation tests revealed no sensory lesions . 
 the light touch sensation test at the lower lip indicated a more frequent reduction of tactility for the test group ( p0.03 ) . 
 neurosensory disturbances can occur in the anterior region of the mandible after implant surgery . 
Introduction
Materials and methods
Results
Results of the psychological and psychophysical tests
Discussion
Conclusions
Questionnaire