CRANIOMAXILLOFACIAL DEFORMITIES/COSMETIC SURGERY
Inferior Alveolar Nerve Function After Sagittal Split Osteotomy by Reciprocating Saw or Piezosurgery Instrument: Prospective Double-Blinded Study Marcelo Silva Monnazzi, DDS, MSc, PhD,* Mario Francisco Real Gabrielli, DDS, MD, MSc, PhD,y Luis Augusto Passeri, DDS, MSc, PhD,z Marisa Aparecida Cabrini Gabrielli, DDS, MSc, PhD,x Rubens Spin-Neto, DDS, MSc, PhD,k and Valfrido Antonio Pereira-Filho, DDS, MSc, PhD{ Purpose:
The aim of this prospective study was to objectively evaluate inferior alveolar nerve (IAN) sensory disturbances in patients who underwent sagittal split ramus osteotomy (SSRO) by comparing 1 side treated with a reciprocating saw with the other side treated with a piezosurgery device.
Materials and Methods:
Clinical evaluation of IAN sensory disturbance was undertaken preoperatively and at 1 week, 4 weeks, 2 months, and 6 months postoperatively in 20 patients who underwent SSRO at the Division of Oral and Maxillofacial Surgery, Araraquara Dental School, S~ao Paulo State University. The 20 patients were examined at all periods for IAN functionality by Semmes-Weinstein testing; neither the patients nor the examiner knew which side was treated using piezosurgery or a reciprocating saw.
Results:
The mean age of the patients was 28.4 years (range, 20 to 48 yr). Before surgery, no patient had impaired function of the IAN in any of the 8 zones in the mental and inferior lip areas. All patients reported feeling the first monofilament at the time of the preoperative test. Seven days postoperatively, all patients reported some kind of altered sensitivity in at least 1 zone evaluated.
Conclusions: The results of this study suggest there was no statistically significant difference in the sensitivity of the labiomental area regarding the instrument used to perform the osteotomy. Future studies will focus on enlarging the sample and evaluating the results. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:1168-1172, 2014
In orthognathic surgery, each type of osteotomy has its particularities regarding execution, fixation, stability, and clinical outcomes. Those features are studied to make osteotomies easier, safer, and more predictable. The most common complication of the sagittal split ramus osteotomy (SSRO) is inferior alveolar nerve
(IAN) postoperative functional disturbance. There are several ways to quantify the lack of sensitivity in surgically treated patients. According to several studies, testing with graduated nylon filaments (Semmes-Weinstein test) produces enough evidence to evaluate sensitivity.1-5 {Assistant Professor, Division of Oral and Maxillofacial Surgery,
*Volunteer Professor, Araraquara Dental School, S~ao Paulo State University, Araraquara, SP, Brazil.
Araraquara Dental School, S~ao Paulo State University, Araraquara,
yProfessor, Division of Oral and Maxillofacial Surgery, Araraquara
SP, Brazil.
Dental School, S~ao Paulo State University, Araraquara, SP, Brazil.
Address correspondence and reprint requests to Dr Monnazzi:
zProfessor, Department of Oral and Maxillofacial Surgery,
Rua Voluntarios da Patria, 2777, ap 1001, Araraquara, SP, Brasil,
Division of Plastic Surgery, Department of Surgery, Faculty of
CEP 14801-320; e-mail: [email protected]
Medical Sciences, University of Campinas, Campinas, SP, Brazil.
Received October 1 2013
xAssistant Professor, Division of Oral and Maxillofacial Surgery, Araraquara Dental School, S~ao Paulo State University, Araraquara,
Ó 2014 American Association of Oral and Maxillofacial Surgeons
SP, Brazil.
0278-2391/13/01418-3$36.00/0
kPhD student at Aarthus University, Aarhus University, Aarhus,
Accepted November 8 2013
http://dx.doi.org/10.1016/j.joms.2013.11.007
Denmark.
1168
1169
MONNAZZI ET AL
FIGURE 1. Clinical photograph of evaluated cutaneous areas and their respective numbers. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
The tactile threshold measured by nylon monofilaments quantifies skin or mucous sensibility regarding light mechanical touch.6 This method is reliable according to many investigators,7-11 and its easy applicability and low price make it a useful clinical tool. Sensitivity evaluation using nylon filaments was developed by Semmes and Weinstein after studies by von Frey.4 The Semmes-Weinstein test is one of the most reliable tests for clinical application, and it presents 91% sensitivity and 80% specificity according to some investigators.12-14 Thus, it provides graduated measurements of sensitivity or its lack at many levels, from normal to profound loss. The use of piezosurgery is increasing because of the protection it offers to soft tissues.15 Several studies have described the advantages of the method over the use of saws or burs.16-19 This prospective clinical study compared postoperative IAN dysfunction after bilateral SSRO using a reciprocating saw versus piezosurgery.
Materials and Methods Twenty consecutive patients from the Division of Oral and Maxillofacial Surgery, Araraquara Dental School, S~ao Paulo State University (Araraquara, SP,
Brazil) who had an indication for orthognathic surgery and whose treatment planning included the need for an SSRO, regardless of the direction of mandibular repositioning, were included in this prospective study. Inclusion criteria were to be dentate, have orthodontic preparation for surgery, no history of facial fracture or significant trauma to the face, no history of neurologic disease or facial palsy, and no history of a systemic condition that could alter nerve function. Exclusion criteria were any systemic contraindication for surgery, craniofacial clefts or syndromes, preoperative testing of sensation indicating altered sensitivity, bad SSRO split, or unusual nerve manipulation during surgery, including the manipulation necessary to free the nerve from the proximal segment. All patients underwent surgery from July 2011 to December 2012 by the same surgical team whose surgeons followed the same principles and techniques when performing an SSRO. Sagittal osteotomies were performed on 1 side with a piezosurgery instrument (Piezosonic, Driller; group I) and on the other side of the same patient with a reciprocating saw (Stryker, Kalamazoo, MI; group II, Driller, Jaguare, Sp, Brazil). The design of the osteotomy was the Dal Pont modification, and the split was performed using Smith
1170 spreaders (superior and inferior border separators); the use of osteotomes and chisels was avoided so as to not damage the nerve and not interfere with the sensitivity evaluation. Stable fixation was achieved by the use of monocortical plates and bicortical screws in a hybrid method, in which 1 or 2 bicortical screws were placed behind and superior to the plate. The side chosen was determined according to the surgical schedule, namely the first patient underwent piezosurgery on the right side, the second patient underwent piezosurgery on the left side, and so on. All 20 patients were evaluated preoperatively and 1 week (T2), 1 month, 2 months, and 6 months (T5) after surgery. Skin sensibility was tested with an esthesiometer kit similar to the Semmes-Weinstein test (SORRI, Bauru, SP, Brazil) in 4 areas previously defined and always by the same examiner who had calibrated and did not know, as the patients did not, which osteotomy cutting device was used on which side. The cutaneous area to be evaluated was divided into 4 zones on each side of the face according to an outline similar to the one proposed by Gianni et al.10 Area 1 was the median region of the chin and lip 1 cm bilateral from the mandibular symphysis; area 2 was the paramedian region 2 cm bilateral from the symphysis; area 3 was the area of the mental foramen 3 cm bilateral from the symphysis; and area 4 was the vermilion of the lower lip (Fig 1). The Semmes-Weinstein monofilament esthesiometer used in this study consists of a group of 6 monofilaments of different thicknesses, numbered 1 to 6, with filament 1 being the finest with a weight value of 0.05 g, followed by number 2 with a value of 0.2 g, number 3 with a value of 2.0 g, number 4 with a value of 4.0 g, number 5 with a value of 10.0 g, and number 6 with a value of 300 g (filament 6 is the only filament that is not bendable). A number 7 was marked on the chart when the patient did not feel any of the other filaments previously tested in a particular area. The tests were carried out in a room free of any acoustic or visual disturbances capable of affecting the results, the patients keeping their eyes closed. The results were recorded on a standard form by writing the number of the first monofilament perceived by the patient, always starting from the lighter one and according to the manufacturer’s instructions. Each monofilament was applied to the skin or mucosa 3 times at each area until it bent and the patients were asked to identify its position by pointing with a finger. The results were tabulated and statistically analyzed. For the comparison between groups, the Wilcoxon test was applied, because the sensitivity function data present a nonparametric distribution. For comparisons between periods of evaluation, the Friedman test was used followed by the Dunn multiple comparison test.
INFERIOR ALVEOLAR NERVE FUNCTION
FIGURE 2. Preoperative score averages and standard deviations. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
This study followed the Declaration of Helsinki on medical protocol and ethics and the regional ethical review board of the Araraquara Dental School approved this study.
Results The mean age of the patients included in this study was 28.4 years (range, 20 to 48 yr). Before surgery, no patient had impaired function of the IAN in any of the 8 areas in the mental and inferior lip areas. All patients reported feeling the first monofilament at the time of the preoperative test. Seven days postoperatively (T2), all patients reported some kind of altered sensitivity in at least 1 of the areas evaluated. At the 4 postoperative periods evaluated, the comparison between the 2 groups did not show any significant difference (Figs 2-5) in sensitivity for bone cut by saw versus the piezo device. At T2, only 1 patient had
FIGURE 3. Score averages and standard deviations at 1 week after surgery. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
1171
MONNAZZI ET AL
FIGURE 4. Score averages and standard deviations at 1 month after surgery. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
complete lack of sensitivity at areas 1 and 2 in both sides. In this patient, the side osteotomized with the piezosurgery instrument had complete return of sensitivity after 1 month, whereas sensitivity returned after 6 months for the side cut with the saw. When comparing the same tested area for the 5 evaluation periods, there was a statistically significant difference for area 1 in group I between the baseline value and the values reported after 7 days (P # .0001) and 1 month (P # .05) postoperatively. The value reported at 6 months also differed (P # .01) from the reported value at 7 days. For area 1 in group II, there was a difference between the baseline value and the value reported after 7 days (P #.05) postoperatively, showing that sensitivity returned to normal similarly in time in the 2 groups. For area 2, there was a difference for group I between the baseline value and the values reported after
FIGURE 5. Score averages and standard deviations at 2 months after surgery. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
7 days and 1 month (P #.01) and between the values reported after 1 month and 6 months (P # .01). For group II, there was a difference between the baseline value and the value reported after 1 month (P # .05). For area 3, there was difference for group I between the baseline value and the values reported after 7 days and 1 month (P # .05) and between the values reported after 1 month and after 6 months (P # .05). For group II, there was a difference between the baseline value and the value reported after 1 month (P # .01) and between the values reported after 1 month and after 6 months (P # .05). For area 4, there was difference for group I between the baseline value and the values reported after 7 days and 1 month (P # .0001) and between the values reported after 1 month and after 6 months (P # .0001). Exactly the same results were seen for group II (except P # .01). This statistical study showed slight differences between the areas in relation to the periods; however, the differences between groups were not significant and the results for the 2 groups were similar in sensitivity recovery.
Discussion The SSRO is the most often used mandibular osteotomy20-23 owing to its several advantages, such as its broad application range for the treatment of facial deformities; the intraoral approach, making the surgical scar less conspicuous and avoiding facial nerve damage; and the possibility and ease of stable internal fixation. However, it also presents some disadvantages, and the most common is temporary IAN disturbance.20-24 There are numerous tests described by the scientific literature to measure sensitive nerve function, such as light touch, static 2-point discrimination, thermal tests, sharp and blunt testing, and electrical testing.1-14. The tactile sensibility variation determined by the Semmes-Weinstein monofilaments quantifies mucous and cutaneous sensitivity to the mechanical light touch,4 and this kind of test has been considered one of the most trustworthy in clinical studies.5-7 The mean age of the patients included in this study was approximately 28.4 years old, which is quite similar to the age-related data found in other studies that have evaluated orthognathic surgical outcome.20-24 The incidence of IAN sensory disturbance after surgery at the first postoperative evaluation (T2) was 100%; each patient showed some degree of disturbance at that time in all the areas considered, as reported by other investigators.18-24 The authors used routine follow-up periods to avoid adding expense to the patients or institution. The last period (T5) was chosen based on the surgeons’ clinical experience and in
1172 agreement with other investigators who performed similar studies, considering that after 6 months most of the cutaneous facial sensibility has returned.21-25 For the past 2 decades, Labanca et al15 described the use of ultrasonic vibrations for bone cutting, stating that piezosurgery is a minimally invasive technique that lessens the risk of damage to surrounding soft tissues and other important anatomic structures, such as vessels, nerves, and mucosa. This was the main reason for this study, namely to verify whether safety could be reflected in less neurosensory disturbance in the sagittal osteotomy. Landes et al16,17 stated other advantages of piezosurgical bone osteotomy, such as the individualization of cut designs and decreased blood loss. However, in the present study, no statistical significant difference was found in labiomental fold sensitivity when the SSRO was performed with a piezosurgical instrument or reciprocating saw. This reflects the fact that neurosensory dysfunction in this case is inherent to the technique and results from several factors other than the cutting instrument even in the absence of direct trauma to the nerve. Also, anatomy and nerve position, manipulation of the osteotomized segments, manipulation, stretching, or compression of the IAN, and the direction and dimension of repositioning, among others, play a role in postoperative neurosensory disturbance. Most patients will progress to the base level of sensitivity in the labiomental area within 6 months. The results of this study suggested no statistically significant difference in sensitivity of the labiomental area regarding the instrument used to perform the SSRO. Future studies will focus on enlarging the sample and evaluating the results.
References 1. Jerosch-Herold C: Assessment of sensibility after nerve injury and repair: A systematic review of evidence for validity, reliability and responsiveness of tests. J Hand Surg Eur Vol 30: 252, 2005 2. Patel MR, Bassini L: A comparison of five tests for determining hand sensibility. J Reconstr Microsurg 15:523, 1999 3. Anderson AM, Croft RP: Reliability of Semmes Weinstein monofilament and ballpoint sensory testing, and voluntary muscle testing in Bangladesh. Lepr Rev 70:305, 1999 4. Weinstein S: Fifty years of somatosensory research: From the Semmes-Weinstein monofilaments to the Weinstein Enhanced Sensory Test. J Hand Ther 6:11, 1993 5. Komiyama O, Gracely R, Kawara M, et al: Intraoral measurement of tactile and filament-prick pain threshold using shortened Semmes-Weinstein monofilaments. J Orofac Pain 24:16, 2008
INFERIOR ALVEOLAR NERVE FUNCTION 6. Jacobs R, Wu CH, Van Loven K, et al: Methodology of oral sensory tests. J Oral Rehabil 29:720, 2002 7. De Beukelaer JGP, Smeele LE, Van Ginkel FC: Is short-term neurosensory testing after removal of mandibular third molars efficacious? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 85:366, 1998 8. Eliav E, Gracely RH: Sensory changes in the territory of the lingual and inferior alveolar nerves following lower third molar extraction. Pain 7:191, 1998 9. Cordeiro PG, Schwartz M, Neves RI, et al: A comparison of donor and recipient site sensation in free tissue reconstruction of the oral cavity. Ann Plast Surg 39:461, 1997 10. Gianni AB, D’Orto O, Biglioli F, et al: Neurosensory alterations of the inferior alveolar and mental nerve after genioplasty alone or associated with sagittal osteotomy of the mandibular ramus. J Craniomaxillofac Surg 30:295, 2002 11. Monnazzi MS, Real-Gabrielli MF, Passeri LA, et al: Cutaneous sensibility impairment after mandibular sagittal split osteotomy: A prospective clinical study of the spontaneous recovery. J Oral Maxillofac Surg 70:696, 2012 12. Villarroel MF, Orsini MB, Lima RC, et al: Comparative study of the cutaneous sensation of leprosy-suspected lesions using SemmesWeinstein monofilaments and quantitative thermal testing. Lepr Rev 78:102, 2007 13. Bell-Krotoski J: Pocket filaments and specifications for the Semmes-Weinstein monofilaments. J Hand Ther 3:26, 1990 14. Bell-Krotoski J: Peripheral neuropathy and examination of the hands. Star 50:1, 1991 15. Labanca M, Azzola F, Vinci R, et al: Piezoelectric surgery: Twenty years of use. Br J Oral Maxillofac Surg 46:265, 2008 16. Landes CA, Stubinger S, Ballon A, et al: Piezoosteotomy in orthognathic surgery versus conventional saw and chisel osteotomy. Oral Maxillofac Surg 12:139, 2008 17. Landes CA, Stubinger S, Rieger J, et al: Critical evaluation of piezoelectric osteotomy in orthognathic surgery operative technique, blood loss, time requirement, nerve and vessel integrity. J Oral Maxillofac Surg 66:657, 2008 18. Sakkas N, Otten J, Gutwald R, et al: Transposition of the mental nerve by piezosurgery followed by postoperative neurosensory control: A case report. Br J Oral Maxillofac Surg 46:270, 2008 19. Pavlıkova G, Foltan R, Horka M, et al: Piezosurgery in oral and maxillofacial surgery. Int J Oral Maxillofac Surg 40:451, 2010 20. Kobayashi A, Yoshimasu H, Kobayashi J, et al: Neurosensory alteration in the lower lip and chin area after orthognathic surgery: Bilateral sagittal split osteotomy versus inverted L ramus osteotomy. J Oral Maxillofac Surg 64:778, 2006 21. Yamashita Y, Mizuashi K, Shigematsu M, et al: Masticatory function and neurosensory disturbance after mandibular correction by bilateral sagittal split ramus osteotomy: A comparison between miniplate and bicortical screw rigid internal fixation. Int J Oral Maxillofac Surg 36:118, 2007 22. Vriens JPM, Van der Glas HW: Extension of normal values on sensory function for facial areas using clinical tests on touch and two-point discrimination. Int J Oral Maxillofac Surg 38:1154, 2009 23. Wijbenga JG, Verlinden CRA, Jansma J, et al: Long-lasting neurosensory disturbance following advancement of the retrognathic mandible: Distraction osteogenesis versus bilateral sagittal split osteotomy. Int J Oral Maxillofac Surg 38:719, 2009 24. Phillips C, Essick G, Zuniga J, et al: Qualitative descriptors used by patients following orthognathic surgery to portray altered sensation. J Oral Maxillofac Surg 64:1751, 2006 25. Becelli R, Renzi G, Carboni A, et al: Inferior alveolar nerve impairment after mandibular sagittal split osteotomy: An analysis of spontaneous recovery patterns observed in 60 patients. J Craniofac Surg 13:315, 2002
Inferior Alveolar Nerve Function After Sagittal Split Osteotomy by Reciprocating Saw or Piezosurgery Instrument: Prospective Double-Blinded Study Marcelo Silva Monnazzi, DDS, MSc, PhD,* Mario Francisco Real Gabrielli, DDS, MD, MSc, PhD,y Luis Augusto Passeri, DDS, MSc, PhD,z Marisa Aparecida Cabrini Gabrielli, DDS, MSc, PhD,x Rubens Spin-Neto, DDS, MSc, PhD,k and Valfrido Antonio Pereira-Filho, DDS, MSc, PhD{ Purpose:
The aim of this prospective study was to objectively evaluate inferior alveolar nerve (IAN) sensory disturbances in patients who underwent sagittal split ramus osteotomy (SSRO) by comparing 1 side treated with a reciprocating saw with the other side treated with a piezosurgery device.
Materials and Methods:
Clinical evaluation of IAN sensory disturbance was undertaken preoperatively and at 1 week, 4 weeks, 2 months, and 6 months postoperatively in 20 patients who underwent SSRO at the Division of Oral and Maxillofacial Surgery, Araraquara Dental School, S~ao Paulo State University. The 20 patients were examined at all periods for IAN functionality by Semmes-Weinstein testing; neither the patients nor the examiner knew which side was treated using piezosurgery or a reciprocating saw.
Results:
The mean age of the patients was 28.4 years (range, 20 to 48 yr). Before surgery, no patient had impaired function of the IAN in any of the 8 zones in the mental and inferior lip areas. All patients reported feeling the first monofilament at the time of the preoperative test. Seven days postoperatively, all patients reported some kind of altered sensitivity in at least 1 zone evaluated.
Conclusions: The results of this study suggest there was no statistically significant difference in the sensitivity of the labiomental area regarding the instrument used to perform the osteotomy. Future studies will focus on enlarging the sample and evaluating the results. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:1168-1172, 2014
In orthognathic surgery, each type of osteotomy has its particularities regarding execution, fixation, stability, and clinical outcomes. Those features are studied to make osteotomies easier, safer, and more predictable. The most common complication of the sagittal split ramus osteotomy (SSRO) is inferior alveolar nerve
(IAN) postoperative functional disturbance. There are several ways to quantify the lack of sensitivity in surgically treated patients. According to several studies, testing with graduated nylon filaments (Semmes-Weinstein test) produces enough evidence to evaluate sensitivity.1-5 {Assistant Professor, Division of Oral and Maxillofacial Surgery,
*Volunteer Professor, Araraquara Dental School, S~ao Paulo State University, Araraquara, SP, Brazil.
Araraquara Dental School, S~ao Paulo State University, Araraquara,
yProfessor, Division of Oral and Maxillofacial Surgery, Araraquara
SP, Brazil.
Dental School, S~ao Paulo State University, Araraquara, SP, Brazil.
Address correspondence and reprint requests to Dr Monnazzi:
zProfessor, Department of Oral and Maxillofacial Surgery,
Rua Voluntarios da Patria, 2777, ap 1001, Araraquara, SP, Brasil,
Division of Plastic Surgery, Department of Surgery, Faculty of
CEP 14801-320; e-mail: [email protected]
Medical Sciences, University of Campinas, Campinas, SP, Brazil.
Received October 1 2013
xAssistant Professor, Division of Oral and Maxillofacial Surgery, Araraquara Dental School, S~ao Paulo State University, Araraquara,
Ó 2014 American Association of Oral and Maxillofacial Surgeons
SP, Brazil.
0278-2391/13/01418-3$36.00/0
kPhD student at Aarthus University, Aarhus University, Aarhus,
Accepted November 8 2013
http://dx.doi.org/10.1016/j.joms.2013.11.007
Denmark.
1168
1169
MONNAZZI ET AL
FIGURE 1. Clinical photograph of evaluated cutaneous areas and their respective numbers. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
The tactile threshold measured by nylon monofilaments quantifies skin or mucous sensibility regarding light mechanical touch.6 This method is reliable according to many investigators,7-11 and its easy applicability and low price make it a useful clinical tool. Sensitivity evaluation using nylon filaments was developed by Semmes and Weinstein after studies by von Frey.4 The Semmes-Weinstein test is one of the most reliable tests for clinical application, and it presents 91% sensitivity and 80% specificity according to some investigators.12-14 Thus, it provides graduated measurements of sensitivity or its lack at many levels, from normal to profound loss. The use of piezosurgery is increasing because of the protection it offers to soft tissues.15 Several studies have described the advantages of the method over the use of saws or burs.16-19 This prospective clinical study compared postoperative IAN dysfunction after bilateral SSRO using a reciprocating saw versus piezosurgery.
Materials and Methods Twenty consecutive patients from the Division of Oral and Maxillofacial Surgery, Araraquara Dental School, S~ao Paulo State University (Araraquara, SP,
Brazil) who had an indication for orthognathic surgery and whose treatment planning included the need for an SSRO, regardless of the direction of mandibular repositioning, were included in this prospective study. Inclusion criteria were to be dentate, have orthodontic preparation for surgery, no history of facial fracture or significant trauma to the face, no history of neurologic disease or facial palsy, and no history of a systemic condition that could alter nerve function. Exclusion criteria were any systemic contraindication for surgery, craniofacial clefts or syndromes, preoperative testing of sensation indicating altered sensitivity, bad SSRO split, or unusual nerve manipulation during surgery, including the manipulation necessary to free the nerve from the proximal segment. All patients underwent surgery from July 2011 to December 2012 by the same surgical team whose surgeons followed the same principles and techniques when performing an SSRO. Sagittal osteotomies were performed on 1 side with a piezosurgery instrument (Piezosonic, Driller; group I) and on the other side of the same patient with a reciprocating saw (Stryker, Kalamazoo, MI; group II, Driller, Jaguare, Sp, Brazil). The design of the osteotomy was the Dal Pont modification, and the split was performed using Smith
1170 spreaders (superior and inferior border separators); the use of osteotomes and chisels was avoided so as to not damage the nerve and not interfere with the sensitivity evaluation. Stable fixation was achieved by the use of monocortical plates and bicortical screws in a hybrid method, in which 1 or 2 bicortical screws were placed behind and superior to the plate. The side chosen was determined according to the surgical schedule, namely the first patient underwent piezosurgery on the right side, the second patient underwent piezosurgery on the left side, and so on. All 20 patients were evaluated preoperatively and 1 week (T2), 1 month, 2 months, and 6 months (T5) after surgery. Skin sensibility was tested with an esthesiometer kit similar to the Semmes-Weinstein test (SORRI, Bauru, SP, Brazil) in 4 areas previously defined and always by the same examiner who had calibrated and did not know, as the patients did not, which osteotomy cutting device was used on which side. The cutaneous area to be evaluated was divided into 4 zones on each side of the face according to an outline similar to the one proposed by Gianni et al.10 Area 1 was the median region of the chin and lip 1 cm bilateral from the mandibular symphysis; area 2 was the paramedian region 2 cm bilateral from the symphysis; area 3 was the area of the mental foramen 3 cm bilateral from the symphysis; and area 4 was the vermilion of the lower lip (Fig 1). The Semmes-Weinstein monofilament esthesiometer used in this study consists of a group of 6 monofilaments of different thicknesses, numbered 1 to 6, with filament 1 being the finest with a weight value of 0.05 g, followed by number 2 with a value of 0.2 g, number 3 with a value of 2.0 g, number 4 with a value of 4.0 g, number 5 with a value of 10.0 g, and number 6 with a value of 300 g (filament 6 is the only filament that is not bendable). A number 7 was marked on the chart when the patient did not feel any of the other filaments previously tested in a particular area. The tests were carried out in a room free of any acoustic or visual disturbances capable of affecting the results, the patients keeping their eyes closed. The results were recorded on a standard form by writing the number of the first monofilament perceived by the patient, always starting from the lighter one and according to the manufacturer’s instructions. Each monofilament was applied to the skin or mucosa 3 times at each area until it bent and the patients were asked to identify its position by pointing with a finger. The results were tabulated and statistically analyzed. For the comparison between groups, the Wilcoxon test was applied, because the sensitivity function data present a nonparametric distribution. For comparisons between periods of evaluation, the Friedman test was used followed by the Dunn multiple comparison test.
INFERIOR ALVEOLAR NERVE FUNCTION
FIGURE 2. Preoperative score averages and standard deviations. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
This study followed the Declaration of Helsinki on medical protocol and ethics and the regional ethical review board of the Araraquara Dental School approved this study.
Results The mean age of the patients included in this study was 28.4 years (range, 20 to 48 yr). Before surgery, no patient had impaired function of the IAN in any of the 8 areas in the mental and inferior lip areas. All patients reported feeling the first monofilament at the time of the preoperative test. Seven days postoperatively (T2), all patients reported some kind of altered sensitivity in at least 1 of the areas evaluated. At the 4 postoperative periods evaluated, the comparison between the 2 groups did not show any significant difference (Figs 2-5) in sensitivity for bone cut by saw versus the piezo device. At T2, only 1 patient had
FIGURE 3. Score averages and standard deviations at 1 week after surgery. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
1171
MONNAZZI ET AL
FIGURE 4. Score averages and standard deviations at 1 month after surgery. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
complete lack of sensitivity at areas 1 and 2 in both sides. In this patient, the side osteotomized with the piezosurgery instrument had complete return of sensitivity after 1 month, whereas sensitivity returned after 6 months for the side cut with the saw. When comparing the same tested area for the 5 evaluation periods, there was a statistically significant difference for area 1 in group I between the baseline value and the values reported after 7 days (P # .0001) and 1 month (P # .05) postoperatively. The value reported at 6 months also differed (P # .01) from the reported value at 7 days. For area 1 in group II, there was a difference between the baseline value and the value reported after 7 days (P #.05) postoperatively, showing that sensitivity returned to normal similarly in time in the 2 groups. For area 2, there was a difference for group I between the baseline value and the values reported after
FIGURE 5. Score averages and standard deviations at 2 months after surgery. Monnazzi et al. Inferior Alveolar Nerve Function. J Oral Maxillofac Surg 2014.
7 days and 1 month (P #.01) and between the values reported after 1 month and 6 months (P # .01). For group II, there was a difference between the baseline value and the value reported after 1 month (P # .05). For area 3, there was difference for group I between the baseline value and the values reported after 7 days and 1 month (P # .05) and between the values reported after 1 month and after 6 months (P # .05). For group II, there was a difference between the baseline value and the value reported after 1 month (P # .01) and between the values reported after 1 month and after 6 months (P # .05). For area 4, there was difference for group I between the baseline value and the values reported after 7 days and 1 month (P # .0001) and between the values reported after 1 month and after 6 months (P # .0001). Exactly the same results were seen for group II (except P # .01). This statistical study showed slight differences between the areas in relation to the periods; however, the differences between groups were not significant and the results for the 2 groups were similar in sensitivity recovery.
Discussion The SSRO is the most often used mandibular osteotomy20-23 owing to its several advantages, such as its broad application range for the treatment of facial deformities; the intraoral approach, making the surgical scar less conspicuous and avoiding facial nerve damage; and the possibility and ease of stable internal fixation. However, it also presents some disadvantages, and the most common is temporary IAN disturbance.20-24 There are numerous tests described by the scientific literature to measure sensitive nerve function, such as light touch, static 2-point discrimination, thermal tests, sharp and blunt testing, and electrical testing.1-14. The tactile sensibility variation determined by the Semmes-Weinstein monofilaments quantifies mucous and cutaneous sensitivity to the mechanical light touch,4 and this kind of test has been considered one of the most trustworthy in clinical studies.5-7 The mean age of the patients included in this study was approximately 28.4 years old, which is quite similar to the age-related data found in other studies that have evaluated orthognathic surgical outcome.20-24 The incidence of IAN sensory disturbance after surgery at the first postoperative evaluation (T2) was 100%; each patient showed some degree of disturbance at that time in all the areas considered, as reported by other investigators.18-24 The authors used routine follow-up periods to avoid adding expense to the patients or institution. The last period (T5) was chosen based on the surgeons’ clinical experience and in
1172 agreement with other investigators who performed similar studies, considering that after 6 months most of the cutaneous facial sensibility has returned.21-25 For the past 2 decades, Labanca et al15 described the use of ultrasonic vibrations for bone cutting, stating that piezosurgery is a minimally invasive technique that lessens the risk of damage to surrounding soft tissues and other important anatomic structures, such as vessels, nerves, and mucosa. This was the main reason for this study, namely to verify whether safety could be reflected in less neurosensory disturbance in the sagittal osteotomy. Landes et al16,17 stated other advantages of piezosurgical bone osteotomy, such as the individualization of cut designs and decreased blood loss. However, in the present study, no statistical significant difference was found in labiomental fold sensitivity when the SSRO was performed with a piezosurgical instrument or reciprocating saw. This reflects the fact that neurosensory dysfunction in this case is inherent to the technique and results from several factors other than the cutting instrument even in the absence of direct trauma to the nerve. Also, anatomy and nerve position, manipulation of the osteotomized segments, manipulation, stretching, or compression of the IAN, and the direction and dimension of repositioning, among others, play a role in postoperative neurosensory disturbance. Most patients will progress to the base level of sensitivity in the labiomental area within 6 months. The results of this study suggested no statistically significant difference in sensitivity of the labiomental area regarding the instrument used to perform the SSRO. Future studies will focus on enlarging the sample and evaluating the results.
References 1. Jerosch-Herold C: Assessment of sensibility after nerve injury and repair: A systematic review of evidence for validity, reliability and responsiveness of tests. J Hand Surg Eur Vol 30: 252, 2005 2. Patel MR, Bassini L: A comparison of five tests for determining hand sensibility. J Reconstr Microsurg 15:523, 1999 3. Anderson AM, Croft RP: Reliability of Semmes Weinstein monofilament and ballpoint sensory testing, and voluntary muscle testing in Bangladesh. Lepr Rev 70:305, 1999 4. Weinstein S: Fifty years of somatosensory research: From the Semmes-Weinstein monofilaments to the Weinstein Enhanced Sensory Test. J Hand Ther 6:11, 1993 5. Komiyama O, Gracely R, Kawara M, et al: Intraoral measurement of tactile and filament-prick pain threshold using shortened Semmes-Weinstein monofilaments. J Orofac Pain 24:16, 2008
INFERIOR ALVEOLAR NERVE FUNCTION 6. Jacobs R, Wu CH, Van Loven K, et al: Methodology of oral sensory tests. J Oral Rehabil 29:720, 2002 7. De Beukelaer JGP, Smeele LE, Van Ginkel FC: Is short-term neurosensory testing after removal of mandibular third molars efficacious? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 85:366, 1998 8. Eliav E, Gracely RH: Sensory changes in the territory of the lingual and inferior alveolar nerves following lower third molar extraction. Pain 7:191, 1998 9. Cordeiro PG, Schwartz M, Neves RI, et al: A comparison of donor and recipient site sensation in free tissue reconstruction of the oral cavity. Ann Plast Surg 39:461, 1997 10. Gianni AB, D’Orto O, Biglioli F, et al: Neurosensory alterations of the inferior alveolar and mental nerve after genioplasty alone or associated with sagittal osteotomy of the mandibular ramus. J Craniomaxillofac Surg 30:295, 2002 11. Monnazzi MS, Real-Gabrielli MF, Passeri LA, et al: Cutaneous sensibility impairment after mandibular sagittal split osteotomy: A prospective clinical study of the spontaneous recovery. J Oral Maxillofac Surg 70:696, 2012 12. Villarroel MF, Orsini MB, Lima RC, et al: Comparative study of the cutaneous sensation of leprosy-suspected lesions using SemmesWeinstein monofilaments and quantitative thermal testing. Lepr Rev 78:102, 2007 13. Bell-Krotoski J: Pocket filaments and specifications for the Semmes-Weinstein monofilaments. J Hand Ther 3:26, 1990 14. Bell-Krotoski J: Peripheral neuropathy and examination of the hands. Star 50:1, 1991 15. Labanca M, Azzola F, Vinci R, et al: Piezoelectric surgery: Twenty years of use. Br J Oral Maxillofac Surg 46:265, 2008 16. Landes CA, Stubinger S, Ballon A, et al: Piezoosteotomy in orthognathic surgery versus conventional saw and chisel osteotomy. Oral Maxillofac Surg 12:139, 2008 17. Landes CA, Stubinger S, Rieger J, et al: Critical evaluation of piezoelectric osteotomy in orthognathic surgery operative technique, blood loss, time requirement, nerve and vessel integrity. J Oral Maxillofac Surg 66:657, 2008 18. Sakkas N, Otten J, Gutwald R, et al: Transposition of the mental nerve by piezosurgery followed by postoperative neurosensory control: A case report. Br J Oral Maxillofac Surg 46:270, 2008 19. Pavlıkova G, Foltan R, Horka M, et al: Piezosurgery in oral and maxillofacial surgery. Int J Oral Maxillofac Surg 40:451, 2010 20. Kobayashi A, Yoshimasu H, Kobayashi J, et al: Neurosensory alteration in the lower lip and chin area after orthognathic surgery: Bilateral sagittal split osteotomy versus inverted L ramus osteotomy. J Oral Maxillofac Surg 64:778, 2006 21. Yamashita Y, Mizuashi K, Shigematsu M, et al: Masticatory function and neurosensory disturbance after mandibular correction by bilateral sagittal split ramus osteotomy: A comparison between miniplate and bicortical screw rigid internal fixation. Int J Oral Maxillofac Surg 36:118, 2007 22. Vriens JPM, Van der Glas HW: Extension of normal values on sensory function for facial areas using clinical tests on touch and two-point discrimination. Int J Oral Maxillofac Surg 38:1154, 2009 23. Wijbenga JG, Verlinden CRA, Jansma J, et al: Long-lasting neurosensory disturbance following advancement of the retrognathic mandible: Distraction osteogenesis versus bilateral sagittal split osteotomy. Int J Oral Maxillofac Surg 38:719, 2009 24. Phillips C, Essick G, Zuniga J, et al: Qualitative descriptors used by patients following orthognathic surgery to portray altered sensation. J Oral Maxillofac Surg 64:1751, 2006 25. Becelli R, Renzi G, Carboni A, et al: Inferior alveolar nerve impairment after mandibular sagittal split osteotomy: An analysis of spontaneous recovery patterns observed in 60 patients. J Craniofac Surg 13:315, 2002
