Changes in the sensitivity of cutaneous points and the oral mucosa after intraoral vertical ramus osteotomy

Abstract

In this study we investigated the changes in the sensitivity of cutaneous points and the oral mucosa that occur after intraoral vertical ramus osteotomy (IVRO). Additionally, postoperative changes in the sensitivity and the relationships between neurosensory disturbance and factors associated with IVRO operations were evaluated. An objective evaluation of the neurosensory status of cutaneous points and the oral mucosa of each patient was completed preoperatively and at 1, 2, 4, 8, 12, and 24 weeks postoperatively. The other variables studied for each patient included sex, age, magnitude of mandibular setback, and the amount of haemorrhage that occurred during surgery. In addition, the relationships between neurosensory disturbance and factors connected with IVRO operations were evaluated. We found that at cutaneous points, contributing factors such as sex, age, the magnitude of mandibular setback, and haemorrhage were associated with an increased risk of neurosensory disturbance after IVRO. However, these factors were not associated with that in the oral mucosa. In conclusion, we demonstrated the changes that occur in the sensitivity of cutaneous points and the oral mucosa after IVRO, the postoperative changes in sensitivity, and the relationships between neurosensory disturbance and factors connected with IVRO operations.

Introduction

The intraoral vertical ramus osteotomy (IVRO) is a method that is well-established for the correction of mandibular deformities. The vertical ramus osteotomy was first described as an extraoral procedure. The main disadvantages of this technique include the need for postoperative intermaxillary fixation (IMF) and the development of extraoral visible scars, condylar sag, and necrosis of the distal tip of the proximal segment. Moose introduced an intraoral approach to prevent the formation of facial scars. The need for postoperative IMF is still the primary shortcoming of IVRO. The foremost advantage of IVRO over sagittal split ramus osteotomy (SSRO) is a comparatively low incidence of neurosensory disturbance, which ranges from 0% to 35%. Previous investigators have reported findings regarding the neurosensory disturbance after IVRO, however only the cutaneous points have been studied. Few authors have examined changes in the tactile sense of the oral mucosa after orthognathic surgery. In this study, we investigated the changes in the sensitivity of cutaneous points and the oral mucosa that occur after IVRO. Additionally, postoperative changes in sensitivity and the relationships between neurosensory disturbance and factors connected with IVRO operations were evaluated.

Patients and methods

Subjects

This was a non-randomized, retrospective (historic) cohort study of patients, thus the study was granted exemption from institutional review board approval. The subjects included 46 patients (20 men and 26 women) with mandibular prognathism who underwent IVRO (88 rami) at our institution between March 2002 and June 2011. Four unilateral cases were included in this study. Patient age ranged from 16 to 54 years, with a mean age of 26.5 years. Each patient was diagnosed with a skeletal Class III malocclusion with mandibular prognathism after a clinical examination and a complete review of the patient’s orthodontic records. Exclusion criteria included evidence of a syndromic condition, congenital anomaly, or traumatic injury to the jaw or face. The IVRO surgical technique used in this study was performed as described by Terry and White. Four surgeons were involved in this study, each with more than 5 years of experience. The patients were administered 100 mg hydrocortisone on day 0 and on day 1 after the operation. All patients underwent IMF with stainless steel wires (0.3 mm) and had brackets placed in the maxillary and mandibular arches for 14 days, in accordance with the clinical protocol. We instructed all patients to wear elastic bands for 21 days in order to retain the bone fragments during their hospital stay. Functional treatment involved the use of guiding elastics and a regimen of active mobilization. The active movements with the elastic guidance were continued for up to 3 months. The guiding elastics were initially used full-time, and the patient was slowly weaned off them. All of the elastics were removed when the patients were eating.

Methods

An objective evaluation of the neurosensory status of each patient was completed preoperatively and at 1, 2, 4, 8, 12, and 24 weeks postoperatively. We routinely evaluated the neurosensory status preoperatively and at 1, 2, 4, 8, 12, and 24 weeks postoperatively, because we wanted to be able to clearly explain the changes in the neurosensory status to the patients. However, patients who did not wish to undergo examinations of their neurosensory status were not forced to do so.

Changes in the sensitivity at various cutaneous points were examined using a Semmes–Weinstein pressure esthesiometer (SW esthesiometer) (Research Design, Inc., Houston, TX, USA). The SW esthesiometer consists of 20 individual filaments with different diameters. One end of each filament is mounted on an individual Lucite rod. These monofilaments were labelled with filament marking values (Fmg) ranging from 1.65 to 6.65. These numbers represent the logarithm of 10 times the force in milligrams required to bow the monofilaments. The number for the lightest probe that evoked a perception of pressure was recorded. Touch stimulation was performed in accordance with the method described by Bell. The SW esthesiometer was lowered perpendicularly and placed on the test points for 1–1.5 s. Stimulation was initiated with a force of 1.65 Fmg and the force was increased until the patient recognized it.

Measurements were obtained at three points based on the running courses of the labial inferior ramification, the oral angular ramification, and the mental ramification: cutaneous point 1 (C1) was located on the vermilion border at one-third of the distance between the oral angles, cutaneous point 2 (C2) was located 5 mm below the oral angle, and cutaneous point 3 (C3) was located at the midpoint of the perpendicular line from cutaneous point 1 to the lower margin of the mentum ( Fig. 1 ). Points at which 1.65 Fmg of force was not recognized prior to surgery were excluded. A point at which 2.36–2.83 Fmg of force was required postoperatively was classified as showing reduced neurosensory function. Additionally, a point at which more than 3.22 Fmg of force was required postoperatively was classified as showing a neurosensory disturbance.

Fig. 1
Test sites in the cutaneous region.

Changes in the sensitivity of the oral mucosa were examined using needle puncture. Sensitivity was evaluated on a three-degree scale, where ‘3’ indicated fully normal sensitivity, ‘2’ indicated reduced sensitivity, and ‘1’ indicated total numbness. Measurements were obtained from two regions: gingival point 1 (G1; 4 mm under the marginal gingiva of the molar region), gingival point 2 (G2; 4 mm under the marginal gingiva of the incisal region (lateral incisor tooth)), buccal point 1 (B1; on the buccal mucosa 10 mm up from the oral vestibulum of the molar region), and buccal point 2 (B2; on the labial mucosa 10 mm up from the oral vestibulum of the incisal region (lateral incisor tooth)) ( Fig. 2 ). Sensitivity measurements of ‘1’ and ‘2’ were classified as showing a reduced neurosensory function.

Fig. 2
Test sites in the oral incisor region.

Other variables studied for each patient included sex, age, the magnitude of mandibular setback (in mm), and the amount of haemorrhage that occurred during surgery. The patients were classified into two age groups: patients aged ≤25 years and patients aged ≥26 years. The magnitude of mandibular movement was classified into two groups: mandibular segments with movement ≤7 mm and mandibular segments with movement >7 mm. The amount of blood loss that occurred during surgery was also classified into two groups: haemorrhage ≤200 ml and haemorrhage >200 ml.

Statistical analysis

StatView J-4.5 software (HULINKS Inc., Tokyo, Japan) was used for the statistical analysis, which was carried out on all data for each group by Mann–Whitney U -test or by means of one-way analysis of variance (ANOVA) and Fisher’s protected least significant difference (PLSD) method. Data were presented as the mean ± standard deviation (SD). A value of P < 0.05 was considered statistically significant.

Patients and methods

Subjects

This was a non-randomized, retrospective (historic) cohort study of patients, thus the study was granted exemption from institutional review board approval. The subjects included 46 patients (20 men and 26 women) with mandibular prognathism who underwent IVRO (88 rami) at our institution between March 2002 and June 2011. Four unilateral cases were included in this study. Patient age ranged from 16 to 54 years, with a mean age of 26.5 years. Each patient was diagnosed with a skeletal Class III malocclusion with mandibular prognathism after a clinical examination and a complete review of the patient’s orthodontic records. Exclusion criteria included evidence of a syndromic condition, congenital anomaly, or traumatic injury to the jaw or face. The IVRO surgical technique used in this study was performed as described by Terry and White. Four surgeons were involved in this study, each with more than 5 years of experience. The patients were administered 100 mg hydrocortisone on day 0 and on day 1 after the operation. All patients underwent IMF with stainless steel wires (0.3 mm) and had brackets placed in the maxillary and mandibular arches for 14 days, in accordance with the clinical protocol. We instructed all patients to wear elastic bands for 21 days in order to retain the bone fragments during their hospital stay. Functional treatment involved the use of guiding elastics and a regimen of active mobilization. The active movements with the elastic guidance were continued for up to 3 months. The guiding elastics were initially used full-time, and the patient was slowly weaned off them. All of the elastics were removed when the patients were eating.

Methods

An objective evaluation of the neurosensory status of each patient was completed preoperatively and at 1, 2, 4, 8, 12, and 24 weeks postoperatively. We routinely evaluated the neurosensory status preoperatively and at 1, 2, 4, 8, 12, and 24 weeks postoperatively, because we wanted to be able to clearly explain the changes in the neurosensory status to the patients. However, patients who did not wish to undergo examinations of their neurosensory status were not forced to do so.

Changes in the sensitivity at various cutaneous points were examined using a Semmes–Weinstein pressure esthesiometer (SW esthesiometer) (Research Design, Inc., Houston, TX, USA). The SW esthesiometer consists of 20 individual filaments with different diameters. One end of each filament is mounted on an individual Lucite rod. These monofilaments were labelled with filament marking values (Fmg) ranging from 1.65 to 6.65. These numbers represent the logarithm of 10 times the force in milligrams required to bow the monofilaments. The number for the lightest probe that evoked a perception of pressure was recorded. Touch stimulation was performed in accordance with the method described by Bell. The SW esthesiometer was lowered perpendicularly and placed on the test points for 1–1.5 s. Stimulation was initiated with a force of 1.65 Fmg and the force was increased until the patient recognized it.

Measurements were obtained at three points based on the running courses of the labial inferior ramification, the oral angular ramification, and the mental ramification: cutaneous point 1 (C1) was located on the vermilion border at one-third of the distance between the oral angles, cutaneous point 2 (C2) was located 5 mm below the oral angle, and cutaneous point 3 (C3) was located at the midpoint of the perpendicular line from cutaneous point 1 to the lower margin of the mentum ( Fig. 1 ). Points at which 1.65 Fmg of force was not recognized prior to surgery were excluded. A point at which 2.36–2.83 Fmg of force was required postoperatively was classified as showing reduced neurosensory function. Additionally, a point at which more than 3.22 Fmg of force was required postoperatively was classified as showing a neurosensory disturbance.

Fig. 1
Test sites in the cutaneous region.

Changes in the sensitivity of the oral mucosa were examined using needle puncture. Sensitivity was evaluated on a three-degree scale, where ‘3’ indicated fully normal sensitivity, ‘2’ indicated reduced sensitivity, and ‘1’ indicated total numbness. Measurements were obtained from two regions: gingival point 1 (G1; 4 mm under the marginal gingiva of the molar region), gingival point 2 (G2; 4 mm under the marginal gingiva of the incisal region (lateral incisor tooth)), buccal point 1 (B1; on the buccal mucosa 10 mm up from the oral vestibulum of the molar region), and buccal point 2 (B2; on the labial mucosa 10 mm up from the oral vestibulum of the incisal region (lateral incisor tooth)) ( Fig. 2 ). Sensitivity measurements of ‘1’ and ‘2’ were classified as showing a reduced neurosensory function.

Fig. 2
Test sites in the oral incisor region.

Other variables studied for each patient included sex, age, the magnitude of mandibular setback (in mm), and the amount of haemorrhage that occurred during surgery. The patients were classified into two age groups: patients aged ≤25 years and patients aged ≥26 years. The magnitude of mandibular movement was classified into two groups: mandibular segments with movement ≤7 mm and mandibular segments with movement >7 mm. The amount of blood loss that occurred during surgery was also classified into two groups: haemorrhage ≤200 ml and haemorrhage >200 ml.

Statistical analysis

StatView J-4.5 software (HULINKS Inc., Tokyo, Japan) was used for the statistical analysis, which was carried out on all data for each group by Mann–Whitney U -test or by means of one-way analysis of variance (ANOVA) and Fisher’s protected least significant difference (PLSD) method. Data were presented as the mean ± standard deviation (SD). A value of P < 0.05 was considered statistically significant.

Results

Prior to surgery, stimulation with the thinnest filament and 1.65 Fmg of force was recognized at 213 of 264 (C1, C2, C3) cutaneous points (80.7%); 2.36 Fmg of force was recognized at 36 points (13.6%); 2.44 Fmg of force was recognized at 12 points (4.5%); 2.83 Fmg of force was recognized at 2 points (0.8%); 3.22 Fmg of force was recognized at 1 point (0.4%). Of the 120 points tested in the male patients, more than 2.36 Fmg of force was required for recognition in 48 (40.0%). Of the 144 points tested in the female patients, more than 2.36 Fmg of force was required for recognition in only 3 (2.1%) ( Fig. 3 ). The number of points at which more than 2.36 Fmg of force was recognized in the male patients was significantly higher than that for the female patients ( P < 0.05).

Jan 20, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Changes in the sensitivity of cutaneous points and the oral mucosa after intraoral vertical ramus osteotomy
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