Emeka Nkenke Stefan Schultze-Mosgau Martin Radespiel-Tröger Frank Kloss Friedrich Wilhelm Neukam Authors’ affiliations: E. Nkenke, S. Schultze-Mosgau, F. Kloss, F. W. Neukam, Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg (Head: Prof. Dr. Dr. F.W. Neukam), Erlangen Martin Radespiel-Tröger, Institute of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nuremberg (Head: Prof. Dr. O. Gefeller), Erlangen, Germany Correspondence to: Dr. Dr. Emeka Nkenke Department of Oral and Maxillofacial Surgery University of Erlangen-Nuremberg Glückstr. 11 91054 Erlangen Germany Tel: π49 9131 8534221 Fax: π49 9131 8534219 e-mail: emeka.nkenke/mkg.imed.uni-erlangen.de Date: Morbidity of harvesting of chin grafts: a prospective study Key words: chin graft, sensitivity impairment, pulp sensitivity, PATH test Abstract: In a prospective study, 20 patients who underwent harvesting of chin grafts as outpatients, were followed up for 12 months (3 further patients with incomplete followup data were excluded from the study). Preoperatively and 7 days, 1, 3, 6 and 12 months postoperatively, follow-up data were assessed. Evaluation of the superficial sensory function of the inferior alveolar nerve was determined by the Pointed-Blunt Test and the Two-Point-Discrimination Test. Sensory disturbances were objectively assessed by testing thermal sensitivity with the ‘‘Pain and Thermal Sensitivity’’ Test (PATH Test). In addition, evaluation of the pulp sensitivity of teeth 35–45 was carried out by cold vitality testing. One week postoperatively, 8 patients were affected by superficial sensory impairment. 8 nerve territories showed hypoaesthetic reactions and 5 showed hyperaesthetic reactions. After 12 months, two patients still suffered from hypoaesthesia of one side of the chin. There was a statistically significant sensitivity impairment of the chin for all patients comparing the preoperative data of the Two-Point-Discrimination Test (left/right median: 8.17/8.17 mm, interquartile range (IQR) 1.00/2.00 mm) with the first postoperative measurement (left/right median 9.00/8.33 mm, IQR 1.67/2.66 mm). Comparing the latter to the last postoperative measurement there was significant tendency for regeneration of a nerve function (left/right median 8.00/7.84 mm, IQR 0.66/ 2.00 mm). In the PATH Test all hypoaesthetic areas could be identified by a reduction of thermal sensitivity. After the first postoperative examination 21.6% (nΩ38/176) of the examined teeth had lost their pulp sensitivity. After 12 postoperative months 11.4% (nΩ20/176) still did not react sensitively. Many of these were canines (nΩ8/20). Comparing the preoperative to the first postoperative examination, there was a significant reduction of pulp sensitivity. However, statistically significant recovery until the last postoperative follow-up could not be detected. The assessed data show that patients have to be informed extensively about disturbances of the inferior alveolar nerve function lasting longer than 12 months. Moreover, the loss of pulp sensitivity is a very frequent event which has always to be taken into account. Considering the high rate of complications with harvesting of chin grafts, more prospective trials should be done to find out whether there are other donor sites for autogenous bone which put less strain on patients. Accepted 10 April 2000 To cite this article: Nkenke, E., Schultze-Mosgau, S., Radespiel-Tröger, M., Kloss, F., Neukam, F.W. Morbidity of harvesting of chin grafts: a prospective study Clin. Oral Impl. Res. 12, 2001; 495–502 Copyright C Munksgaard 2001 ISSN 0905-7161 Edentulism, profound marginal periodontitis, trauma, malformation, neoplasia and insufficient dentures can lead to atrophy or defects of the alveolar ridge, which may complicate rehabilitation of the masticatory function with dental implants. Therefore, preparation of the implant site can require augmentation with autologous bone grafts. Different extra- and intraoral donor sites are available (Lundgren et al. 1996; Misch 1997). In order to confine surgery to the 495 Nkenke at al . Morbidity of chin graft harvesting oral cavity and to perform it under local anaesthesia, intraorally harvested grafts are preferred if a limited amount of bone is required (Precious & Smith 1992; Raghoebar et al. 1993). The largest quantity can be obtained from the mandibular symphysis. In this region mono- and bicorticospongious grafts can be harvested by several techniques (Bagatin 1987; Borstlap et al. 1990; Freihofer et al. 1991; Freihofer et al. 1993; Widmark et al. 1997). As it is membranous bone, fast revascularisation and less resorption are assumed (Kusiak et al. 1985; Koole 1994; Koole et al. 1989; Koole et al. 1991). Complications concerning the harvesting of chin grafts have been reported before (Hoppenreijs et al. 1992; Jensen et al. 1994; Sindet-Pedersen & Enemark 1988; Sindet-Pedersen & Enemark 1990; Widmark et al. 1997). However, few trials have been done with special emphasis on sensitivity impairment when using this donor site for implantology (Misch et al. 1992; Von Arx & Kurt 1998). Prospective studies cannot be found in the literature. Therefore it was the aim of this study to follow up the morbidity of harvesting Fig. 1. Pre- and postoperative panoramic x-rays. 496 | Clin. Oral Impl. Res. 12, 2001 / 495–502 of chin grafts prospectively. Particular attention was paid to the superficial sensory function of the inferior alveolar nerve and to pulp sensitivity of teeth 35– 45. Material and methods In the Department of Oral and CranioMaxillofacial Surgery at the University of Erlangen-Nuremberg, 23 chin grafts were harvested by three experienced surgeons from April until September 1997 for the preparation of implant sites. All patients who showed regular sensory function of the inferior alveolar nerve bilaterally and had a complete dentition from 35 to 45, were included in the study. None of the patients had had previous surgery in the anterior mandibular region. The 23 patients (14 women and 9 men) had an average age of 44.6∫16.5 years. After paramarginal incision from region 35 to 45, a muco-periosteal flap was prepared and the mental nerve was identified bilaterally. To keep an adequate margin of safety, the harvesting of chin grafts was performed at least 5 mm away from the mental foramina in an anterior direction and 5 mm caudally from the apices taking the root contour on the vestibular plain of the symphyseal region as landmarks (Neukam et al. 1981; Ousterhout 1996). Monocorticospongious bone grafts were harvested with a trephine drill (10 mm in diameter). The lower margin of the mandible was always preserved to avoid changes in the chin contour (Fig. 1). To determine sensitivity impairment after harvesting of chin grafts, different examination methods were applied to assess the different qualities of the superficial sensitivity of the chin and lower lip. In a preoperative test the function of the inferior alveolar nerve was determined on both sides by the Pointed-Blunt Test and the Two-PointDiscrimination Test. Moreover, the ‘‘Pain and Thermal Sensitivity’’ Test (PATH Test) was applied (Schultze-Mosgau et al. 1994; Schultze-Mosgau & Reich 1993). In addition, pulp sensitivity of teeth 35–45 was examined by cold vitality testing with carbon dioxide snow (Rowe & Pitt Ford 1990). The examinations were repeated 1 week, 1 month, 3, 6 and 12 months after surgery according to the follow-up regimen of Schultze-Mosgau et al. (1999). 3 patients did not attend all recall sessions and were therefore excluded from the study. The follow-up was confined to 1 year, because after this time further improvement of the superficial sensory function of the inferior alveolar nerve is unlikely (Robinson 1988). At the end of the follow-up the patients were asked to rate the postoperative strain of harvesting of the chin grafts in comparison to the implant insertion, using a visual analogue scale. The value 100 was defined as maximum postoperative strain. The Pointed-Blunt Test provides a semiquantitative statement on pain and tactile sensitivity. The examination was done with a dental probe and a cotton applicator. Mechanoreceptors (Aa-fibers) and nociceptors (Ad- and C-fibers) were addressed. The qualities normaesthesia/algesia, hypoaesthesia/-algesia, hyperaesthesia/-algesia, anaesthesia/-algesia and paraesthesia could thereby be distinguished (Nishioka et al. 1988). The Two-Point-Discrimination Test allows the simultaneous spatial limit to be quantified. The function of the Aafibers is tested. The examination was done with a Zielinsky caliper. The normal distance of the simultaneous spatial limit is 7–14 mm. An increase of more than 2 mm is considered pathological (Ghali & Epker 1989). The test was repeated three times at every follow-up session. The PATH Test (TSA 2001, Medoc Advanced Medical Systems Inc., Ramat Yishay, Israel) was applied to obtain objective data, since previously described clinical examinations are completely based on patients’ statements. With a computerised and semiautomatic measuring device, the thermal sensitivity of the skin (Ad- and C-fibres) is tested (Schultze-Mosgau et al. 1994; Schultze-Mosgau & Reich 1993). A thermoelectrode is positioned on the skin in the innervation area of the inferior alveolar nerve. It is connected to a computer work-station. By the warming up and cooling down of a Peltier element, thermal stimuli are transmitted. The patient stops the process by pushing a button when the limit of perception is Nkenke at al . Morbidity of chin graft harvesting Fig. 2. Box plot analysis of the Two-Point-Discrimination Test (right chin). reached. Subjective influences during the determination of the limit of perception are avoided by varying the time interval between each stimulus. Five warm and cold stimuli are applied at each measurement. An increase in the limit of perception of more than 1.2æ centigrade in the PATH Test is considered a disturbance of the nerve function (Schultze-Mosgau et al. 1994; Schultze-Mosgau & Reich 1993). With cold vitality testing the Ad- and C-fibers of the tooth innervation are addressed. The cold stimuli were applied to the labial surfaces. The generation of a sensation of pain was rated as a sensitive tooth, the absence of pain was rated as a non-sensitive tooth. A statement on the blood supply of the teeth cannot be provided by cold vitality testing (Nair 1995; Rowe & Pitt Ford 1990). measurement should evaluate whether there was a significant regeneration of the nerve function and the pulp sensitivity in the period of the follow-up. For the description of small groups, medians with interquartile ranges (IQR) were calculated. Comparisons of proportions for paired samples were done using the McNemar Test. The Wilcoxon Test and the Friedman Test, respectively, were used for comparisons of paired samples for rank-scaled variables or when normality of the variables could not be assumed due to small case numbers. The Kruskal-Wallis Test was chosen for comparison of more than two groups of unpaired data. P-values equal to or smaller than 0.05 were considered significant. All calculations were done using SPSS for Windows (SPSS Inc., Chicago, U.S.A.). Statistics Results To determine whether there were statistically significant changes in nerve function and pulp sensitivity, a comparison of the preoperative examinations and the first postoperative examinations was done. A comparison of the first postoperative and the last postoperative 20 patients were followed up for 12 months, corresponding to 40 areas of the inferior alveolar nerve. The first postoperative examination with the PointedBlunt Test showed 8 nerve areas that were hypoaesthetic and hypalgesic and 3 that were hyperaesthetic and hyperalgesic 1 one week and 1 month postoperatively. Altogether, 8 patients were affected by postoperative sensory disturbances at this time. Hyperaesthesia and hyperalgesia had vanished after the 1st postoperative month. However, 4 hypoaesthetic and hypalgetic nerve areas remained 3 months postoperatively. These diminished to two cases of hypoaesthesia and hypalgesia after 6 postoperative months. In two patients hypoaesthesia and hypalgesia remained in one innervation area of the inferior alveolar nerve until the 12th month. Aditionally, 3 patients suffered from paraesthesia. In one case it could still be detected in the last follow-up examination. There was a significant reduction in nerve function for the localisation ‘‘right chin’’ comparing the preoperative examination with the first postoperative control. Until the last measurement after 12 months there was significant regeneration. For the left nerve territory, no significant differences between preand postoperative nerve function could be detected with the Pointed-Blunt Test. With the Two-Point-Discrimination Test, 8 hypoaesthetic nerve areas in 5 patients could be identified after 1 week and after 1 month; these showed a pathological increase of the simultaneous spatial limit of more than 2 mm. After 3 months a pathological increase of the simultaneous spatial limit remained in 4 nerve areas. Impairment of nerve function reduced to 2 cases after 6 postoperative months. After 12 months, 2 nerve areas with a pathologically increased simultaneous spatial limit remained in 2 patients. They were identical with those detected in the Pointed-Blunt Test. However, hyperaesthetic nerve areas could not be identified. Box plots were used to describe the assessed data (Fig. 2). Statistical evaluation revealed that function of the inferior alTable 1. Statistical analysis of the PATH Test (McNemar Test) of difference preop.-1 week postop. vs. difference preop.-12 months postop. (cut-off 1.2æC) Region P-value right chin (warm stimulus) left chin (warm stimulus) right chin (cold stimulus) left chin (cold stimulus) 0.13 0.50 0.13 0.50 497 | Clin. Oral Impl. Res. 12, 2001 / 495–502 Nkenke at al . Morbidity of chin graft harvesting thermal stimuli were found 1 week postoperatively. 2 pathologically reacting nerve areas remained until the 12th month. Again the data were described using box plots (Fig. 3). For statistical evaluation, the differences between the preoperative and the first postoperative measurement and between the preoperative and the last postoperative measurement were compared. A significant impairment could not be found (Table 1). At the end of the follow-up the patients rated the postoperative strain after harvesting of chin grafts compared to the implant insertion, using a visual analogue scale. While the mean value for implantation was 29.5 (range 1–71), for harvesting of chin grafts it increased up to 64.4 (range 11–95) (Table 2). In the statistical analysis an influence of the surgeon on the sensitivity impairment and postoperative strain could not be detected. 1 week and 1 month postoperatively 21.6% (nΩ38/176) of the tested teeth did not react cold-sensitive. There were 19.9% (nΩ35/176) non-sensitive teeth after 3 months and 13.6% (nΩ24/176) after 6 postoperative months, which did not respond to cold vitality testing. At the final examination after 12 months, 11.4% (20/176) of the examined teeth still did not show pulp sensitivity. The canines were affected preferentially (Table 3). When the preoperative examination was compared with the first postoperative examination a significant reduction of pulp sensitivity could be detected. Comparing the first postoperative measurement with the last postoperative measurement, a significant tendency of regeneration of the pulp sensitivity could not be found. Discussion Fig. 3. a. Box plot analysis of the PATH Test (right chin, cold stimulus). b. Box plot analysis of the PATH Test (right chin, warm stimulus). veolar nerve was significantly disturbed bilaterally when the preoperative examination was compared with the first postoperative examination. The regeneration of the superficial sensitivity of the chin in the nerve territories bilaterally was 498 | Clin. Oral Impl. Res. 12, 2001 / 495–502 significant also, comparing first and last postoperative examinations. The PATH Test showed results that were comparable to the Two-Point-Discrimination Test. 8 innervation areas which showed pathological response on For augmentation of the implant site, several donor regions of autogenous bone grafts are available. Because of its biocompatibility and osteoinductivity, autogenous bone is still superior to all allografts and xenografts. However, shortcomings arising from donor site morbidity cannot be ignored. Problems with the harvesting of chin grafts have been described earlier (Hoppenreijs et al. 1992; Jensen et al. 1994; Nkenke at al . Morbidity of chin graft harvesting Sindet-Pedersen & Enemark 1988; Sindet-Pedersen & Enemark 1990; Von Arx & Kurt 1998; Widmark et al. 1997). However, the number of complications is smaller than in the presented study. This seems to be due to the fact that none of the studies are prospective or based on an objective test for the function of the mental nerve (Table 4). Examinations with the Two-PointDiscrimination Test showed a statistically significant impairment of function in the territory of the inferior alveolar nerve bilaterally at the first postoperative measurement. This test seems to be more sensitive when it comes to detecting hypoaesthesia than other clinical tests (Nocini et al. 1999). The bilateral regeneration of the nerve function at the final follow-up after 12 months was also significant. In contrast to the PointedBlunt Test, hyperaesthesia could not be detected by the Two-Point-Discrimination Test. Therefore, the PointedBlunt Test should always be done as well. The PATH Test did not show statistically significant differences for pre- and postoperative measurements. Like the Two-Point-Discrimination Test, it was not suitable to detect hyperaesthesia. However, all hypoaesthetic areas of the inferior alveolar nerve could be iden- Table 2. Postoperative strain (visual analogue scale, where 0Ωminimum and 100Ωmaximum postoperative strain) Surgeon VAS rating Implant insertion VAS rating Harvesting of chin graft 1 2 1 2 22 1 46 60 3 4 5 6 7 8 9 2 1 2 2 2 2 1 49 71 50 47 20 12 37 74 95 88 76 81 11 86 3 3 3 3 3 2 3 3 1 1 1 28 33 43 25 12 15 35 19 20 34 26 29.5 39 52 64 72 85 30 67 53 69 78 62 64.4 Patient 10 11 12 13 14 15 16 17 18 19 20 Mean value VASΩVisual analogue scale tified by an impairment of thermal sensitivity. The PATH Test completes the examination methods for the superficial sensory function of the skin and provides objective data for hypoaesthesia. It can be applied earlier and requires less time than other objective tests, e.g. the SSEP-Test (Schultze-Mosgau et al. 1994; Schultze-Mosgau & Reich 1993). Malfunction of the sensitivity of the lower lip was always correlated to a sensory impairment of the chin. The lower lip showed a regeneration pattern similar to that of the chin. The regeneration Table 3. Loss of pulp sensitivity of teeth 35–45 (nΩ176) Examination 45 (nΩ12) 44 (nΩ19) 43 (nΩ17) 42 (nΩ20) 41 (nΩ19) 31 (nΩ19) 32 (nΩ20) 33 (nΩ20) 34 (nΩ18) 35 (nΩ12) S (nΩ176) % 1 week postoperative 0 2 6 7 5 5 3 6 4 0 38 21.6 1 month postoperative 3 months postoperative 0 0 2 2 6 6 7 7 5 5 5 5 3 2 6 6 4 2 0 0 38 35 21.6 19.9 6 months postoperative 12 months postoperative 0 0 2 2 4 4 5 3 1 1 3 3 1 1 6 4 2 2 0 0 24 20 13.6 11.4 Table 4. Publications on chin grafts Number of patients Immediate complications Authors Complications longer than 3 postoperative months Prospective design Objective assessment of nerve function Sindet-Pedersen & Enemark 1988 Sindet-Pedersen & Enemark 1990 Jensen & Sindet-Pedersen 1991 Hoppenreijs et al. 1992 Misch et al. 1992 Jensen et al. 1994 Misch 1997 28 20 26 26 11 39 31 none none 5 times none none 8 times 3 times 3 times none none none 4 non-sensitive front teeth none 1 stained canine 9 times dull sensation in incisors until the 6th postop. month no no no no no no no no no no no no no no Widmark et al. 1997 Von Arx & Kurt 1998 9 15 2 times hypoaesthesia 13 non-sensitive teeth none 3 non-sensitive teeth no no no no hypoaesthesia hypoaesthesia incision dehiscence paraesthesia 1 stained 32 499 | Clin. Oral Impl. Res. 12, 2001 / 495–502 Nkenke at al . Morbidity of chin graft harvesting of the sensitivity of the lower lip always occurred before or with the regeneration of the chin, as it has been described before (Campell et al. 1987). When the chin graft is harvested the mental nerve is often stretched. Therefore, temporary sensory disorders have to be expected. An interruption of continuity can be avoided by keeping a sufficient margin of safety to the mental foramina, taking into account that the distance to the inferior alveolar nerve can be underestimated because of the Sshaped course of the nerve before leaving the mandible (Bavitz et al. 1993). In the present study, without interrupting the continuity of the inferior alveolar nerve, sensory disorders occurred which lasted longer than 1 year and therefore may be permanent (Robinson 1988). Careful instruction of the patient about these possible complications of the operation should be done, especially because of forensic reasons. If possible, preoperative data of the nerve function should be assessed. After 12 months, 11.4% (nΩ20/176) of the examined teeth remained non-sensitive, although damage to the apices could be excluded intraoperatively and in the radiological control. A statistically significant tendency towards regeneration of pulp sensitivity could not be found in the follow-up period. In an animal experiment, Neukam et al. (1981) proved with microangiography that the margin of safety should be at least 8 mm to preserve the blood supply of the front teeth. The follow-up data, too, indicate that the chosen margin of safety of 5 mm is not sufficient and should be extended as far as possible. Teeth which lose their sensitivity should be followed up regularly by clinical and radiological examinations. Staining of the affected teeth, described by other authors, did not occur (Von Arx & Kurt 1998). When more distal teeth lost their pulp sensitivity more mesial teeth on the ipsilateral side were not necessarily affected (Table 3). This finding proves the well-known overlapping supply for the front teeth by the anterior loops of the inferior alveolar nerve (Wadu et al. 1997). The large number of complications and the high postoperative strain of the patients reveal that chin grafts should 500 | Clin. Oral Impl. Res. 12, 2001 / 495–502 not be used as first choice in augmentation procedures. However, complications are reported with all other donor sites for autogenous bone, especially the iliac crest (Eckardt & Neukam 1992; Hausamen & Neukam 1992; Neukam et al. 1994). Therefore, for all widely used donor sites, prospective trials should be performed to find out which one puts minimum strain on the patient. Résumé Zusammenfassung In einer prospektiven Studie wurden dreiundzwanzig Patienten (durchschnittliches Alter 44.6∫16.5 Jahre, 14 weibliche und 9 männliche Patienten, 3 Ausfälle), bei welchen in der Kinnregion Knochentransplantate entnommen wurden, über einen Zeitraum von 12 Monaten nachuntersucht. Messungen wurden präoperativ, nach 7 Tagen, nach 1, 3, 6 und 12 Monaten durchgeführt. Die Untersuchung der oberflächlichen sensorischen Funktion des N. alveolaris inferior erfolgte mittels eines Tests mit einem stumpfen punktförmigen Instrument und durch den Zwei-Punkte-Diskriminationstest. Sensorische Störungen wurden durch Testung der Wärmeempfindlichkeit mit dem ‘‘Schmerz- und Wärmeempfindlichkeitstest’’ (PATH- Dans une étude prospective, 23 patients (d’un âge moyen de 45∫17 ans, quatorze femmes et neuf hommes, et trois désistements) qui avaient subi la prise de greffon au niveau du menton ont été suivis pendant douze mois. Des données ont été enregistrées avant l’opération ainsi que sept jours, un, trois, six et douze mois après l’opération. L’évaluation de la fonction sensorielle superficielle du nerf alvéolaire inférieur a été déterminée par le test de la pression à l’aide d’une sonde dentaire et le test de discrimination de deux points. Les perturbations sensorielles ont été mesurées objectivement (en évaluant la sensibilité thermique) au moyen du test de la sensibilité à la douleur et thermique (Test PATH). De plus l’évaluation de la sensibilité pulpaire des dents 35 à 45 a été mesurée par le test de vitalité au froid. Une semaine après l’opération huit patients souffraient d’un problème de sensibilité superficielle. Huit territoires nerveux montraient de l’hypoanésthésie et cinq des réactions d’hyperanésthésie. Après douze mois deux patients souffraient toujours d’hypoanésthésie d’un côté du menton. Il y avait une perte de sensibilité statistiquement significative du menton pour tous les patients en comparant les données préopératoires du test de discrimination de deux points (moyenne gauche/droite 8,17/8,17 mm, échelonnement [IQR] 1,00/ 2,00 mm) à la première mesure postopérative (moyenne gauche/droite 9,00/8,33 mm, IQR 1,67/2,66 mm). En comparant cette dernière à la dernière mesure postopérative il y avait une tendance significative à la régénération de la fonction nerveuse (moyenne gauche/droite 8,00/7,84 mm, IQR 0,66/2,00 mm). Dans le test PATH, toutes les hypoanésthésies pouvaient être identifiées par une réduction de la sensibilité thermique. Après le premier examen postopératif 21,6% (nΩ38/176) des dents examinées avaient perdu leur sensibilité pulpaire. Douze mois après l’opération 11,4% (nΩ20/176) ne réagissaient toujours pas à la sensibilité. Les canines étaint principalement les plus affectées (nΩ8/20). En comparant les examens préopératifs au premier examen postopératif, il en résultait une réduction significative de la sensibilité pulpaire. Cependant, un retour à la normale significatif jusqu’au dernier suivi postopératoire n’a pas pû être mis en évidence. Ces données montrent que les patients doivent être très bien informés à propos des problèmes de la fonction nerveuse alvéolaire inférieure qui peuvent durer plus de douze mois. De plus la perte de la sensibilité pulpaire est un évènement trés fréquent qui doit toujours être pris en considération. Considérant le très haut risque de complication lors du prélèvement des greffons osseux au niveau du menton davantage d’études prospectives devraient être effectuées pour découvrir s’il y a d’autres sites donneurs d’os autogène qui affecteraient nettement moins les patients. Test) objektiviert. Zusätzlich wurde noch die Pulpenempfindlichkeit der Zähne 35–45 durch einen Vitalitätstest mittels Kälte bestimmt. Eine Woche nach der Operation waren 8 Patienten von einer oberflächlichen sensorischen Störung betroffen. Acht Nervengebiete zeigten Hypoästhesien und 5 Hyperästhesien. Nach 12 Monaten litten immer noch zwei Patienten an Hypoästhesien auf einer Seite des Kinns. Es bestand bei allen Patienten eine statistisch signifikante Einschränkung der sensorischen Funktion in der Kinnregion zwischen den präoperativen (links/rechts Median: 8.17/8.17 mm interquartile Bandbreite (IQR) 1.00/2.00 mm) und postoperativen (links/rechts Median 9.00/8.33 mm, IQR 1.67/2.66 mm) Messungen mittels des Zwei-Punkte-Diskriminationstests. Wenn die Messungen nach der Operation mit den letzten postoperativen Messungen verglichen wurden, so zeigte sich eine signifikante Tendenz zur Regeneration der Nervenfunktion (links/rechts Median 8.00/ 7.84 mm, IQR 0.66/2.00 mm). Mit dem PATH Test konnten alle Areale mit Hypoästhesien durch eine Reduktion der Wärmeempfindlichkeit identifiziert werden. Nach der ersten postoperativen Untersuchung hatten 21.6% (nΩ38/176) der untersuchten Zähne die Sensibilität der Pulpa verloren. Zwölf Monate postoperativ reagierten immer noch 11.4% (nΩ20/176) der Zähne negativ auf den Kältetest. Meist waren die Eckzähne betroffen (nΩ8/20). Wenn die präoperativen Messungen mit der ersten postoperativen Untersuchung verglichen wurden, so bestand eine statistisch signifikante Reduktion der Sensibilität der Pulpen. Eine statistisch signifikante Erholung bis zur letzten postoperativen Nachuntersuchung konnte jedoch nicht ausgemacht werden. Die erhobenen Daten zeigen, dass die Patienten ausführlich über Beeinträchtigungen der Funktion des Unterkiefernerven während mehr als 12 Monaten informiert werden müssen. Zudem ist der Verlust der Sensibilität der Pulpen sehr häufig anzutreffen und muss daher immer in Betracht gezogen werden. Wenn die hohe Komplikationsrate bei der Gewinnung von Knochentransplantaten in der Kinnregion in Betracht gezogen wird, so kommt man zum Schluss, dass mehr prospektive Untersuchungen durchgeführt werden sollten, um herauszufinden, ob andere Entnahmestellen für autologen Knochen bestehen, welche den Patienten weniger Probleme bereiten. Resumen Se siguieron veintitrés pacientes (media de edad 44.6∫16.5 años), en un estudio prospectivo durante doce meses (14 pacientes hembras y 9 varones, 3 se salieron), que se sometieron a recogida de injertos del Nkenke at al . Morbidity of chin graft harvesting mentón. Se valoraron los datos de seguimiento, preoperativamente, a los 7 dı́as, 1, 3, 6 y 12 meses postoperativamente. La evaluación de la función sensorial del nervio alveolar inferior se determinó por medio del test Pointed-Blunt y el test de discriminación de dos puntos. Las alteraciones sensoriales se valoraron objetivamente probando la sensibilidad térmica con el test ‘‘Sensibilidad Térmica y dolorosa’’ (test PATH). Además la evaluación de la sensibilidad pulpar de los dientes 35–45 se llevó a cabo por medio del test de vitalidad al frı́o. Una semana tras la operación 8 pacientes se vieron afectados de un deterioro sensorial superficial. Ocho territorios nerviosos mostraron reacción hipoestésica, 5 hiperestésica. Tras doce meses dos pacientes todavı́a sufrı́an hipoestésia en un lado del mentón. Hubo un deterioro estadı́sticamente significativo de la sensibilidad del mentón para todos los pacientes comparando los datos preoperatorios del test de discriminación de dos puntos (media izquierda/derecha: 8.17/8.17 mm, rango intercuartil (IQR) 1.00/2.00 mm) a las primeras mediciones preoperatorias (media izquierda/derecha 9.00/8.33 mm, IQR 1.67/2.66 mm). Comparando esto con la última medida postoperatoria existió una tendencia significativa hacia la regeneración de la functión nerviosa (media izquierda/derecha 8.00/7.84 mm, IQR 0.66/2.00 mm). En el test PATH se pudieron identificar todas las áreas hipoestésicas al existir una reducción de la sensibilidad térmica. Tras el primer examen postoperatorio el 21.6% (nΩ176) de los dientes examinados perdieron su sensibilidad pulpar. Tras 12 meses postoperatorios 11.4% (nΩ20/176) no habı́an reaccionado sensitivamente todavı́a. Se afectaron los caninos preferentemen- te (nΩ8/20). Comparando los exámenes preoperatorios a los primeros postoperatorios se produjo una reducción significativa de la sensibilidad pulpar. De todos modos la recuperación estadı́sticamente significativa no se pudo detectar ni en el último control postoperatorio. Los datos valorados muestran que los pacientes deben ser informados extensivamente acerca de las alteraciones de la función del nervio alveolar inferior que duraran más de doce meses. Más aún, la pérdida de función pulpar es un acontecimiento muy frecuente que debe ser siempre tenido en cuenta. Considerando el alto ı́ndice de complicaciones con la recogida de injertos del mentón se deben realizar más experimentos prospectivos para averiguar si existen otros lugares para donar hueso autógeno que supongan menos perjuicio para el paciente. References Bagatin, M. (1987) Reconstruction of orbital defects Ghali, G.E. & Epker, B.N. (1989) Clinical neuro- mandibular and iliac crest bone grafts. An experi- with autogenous bone from mandibular symphysis. Journal of Craniomaxillofacial Surgery 15: 103–105. sensory testing: practical applications. Journal of Oral and Maxillofacial Surgery 47: 1074–1078. mental study in sheep. Journal of Craniomaxillofacial Surgery 19: 133–143. 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