Correlation of mandibular bone quality with neurosensory disturbance after sagittal split ramus osteotomy

Evaluation of the Anatomic Position of the Mandibular Canal Regarding to the Segments of the Mandibular Sagittal Split Ramus Osteotomy to Diminish the Possibility of Injuries: a Pilot Study

Objectives

This pilot study evaluated the relationship between inferior alveolar nerve location through computed tomography scan and intraoperative inferior alveolar nerve entrapment after bilateral sagittal split osteotomy.

Material and Methods

Overall, 20 helicoidal computed tomography scans were evaluated in patients with facial deformities who underwent to bilateral sagittal split osteotomy (BSSO). The distance from the mandibular canal to the internal surface of the buccal and lingual cortical bone, mandibular thickness, bone density and proportion of medullary and cortical bone in 3 regions were evaluated. During the intraoperative period, the segment to which the nerve remained adhered after performing BSSO was analysed, and the data correlated.

Results

The distance from the mandibular canal to the buccal cortical bone showed a mean of 2.6 mm when the inferior alveolar nerve was adhered to the distal segment and mean of 0.7 mm when the nerve was adhered to the proximal segment. The thickness was 11.2 mm and 9.8 mm when the nerve was adhered the distal the proximal segments respectively. Mandibular thickness, distance from the mandibular canal to the buccal and lingual cortical were statistically related to intraoperative nerve entrapment (P < 0.05).

Conclusions

Narrow jaws and the distance from the mandibular canal to buccal cortical bone less than 2 mm increases the risk of the inferior alveolar nerve entrapment in bilateral sagittal split osteotomy.

"Crack under pressure"-Inducing life-like mandible fractures as a potential benefit to surgical education in oral and maxillofacial surgery

The aim of this study was to investigate whether life-like fractures of human cadaveric mandibles with a focus on the condylar process and the intact soft tissue envelope could be simulated. A total of nine fresh-frozen human head specimens were fractured in a custom-made drop-test bench. This reproducible method is based on a weight falling from a defined height onto the fixed specimens, simulating a direct blow to the symphysis of the mandible. All the fractures were analyzed by fluoroscopy and CT-scans. In all the specimens that were included in this study, several typical lesions could be created, resulting in a total of 27 mandible fractures. Seven condylar head fractures with intracapsular fracture patterns, three high, two low and five subcondylar fractures as well as different corpus fractures occurred. Human cadaveric mandibles as part of a complete head specimen with intact soft tissue can be successfully fractured by means of a drop-test bench setup. The amount of load and the exact angle at which the load is applied seem to be of high relevance. Such fractured specimens can be implemented in surgical education courses to teach and improve osteosynthetic techniques.

Do positional changes of the inferior alveolar canal after sagittal split mandibular osteotomy affect neurosensory recovery?

The purpose of this study was to assess the pre- and postoperative position and dimensions of the inferior alveolar canal (IAC) following sagittal split osteotomy (SSO) and identify any association with postoperative neurosensory deficit (NSD) at 1 year. This retrospective cohort study enrolled consecutive patients who had SSO performed to correct skeletal malocclusion. The pre- and postoperative cone beam computed tomography data were superimposed to visualize differences in IAC position and dimensions. Subjective and objective neurosensory tests were used to determine NSD in the inferior alveolar nerve distribution. A total of 20 subjects were included. The preoperative distance from the lateral cortex of the IAC to the inner aspect of the lateral cortex of the mandible was significantly greater in sides with NSD when compared to sides without NSD (P =  0.01). A significantly greater reduction in the postoperative distance measurement was seen in sides with NSD when compared to sides without NSD (P =  0.01). The magnitude of mandibular movement was significantly increased in sides with NSD (P = 0.02). The preoperative location of the IAC, as well as certain changes in the mediolateral and vertical positions as a result of SSO, are risk factors for postoperative NSD.

Neurosensory Disturbances After Bilateral Sagittal Split Osteotomy Using Piezoelectric Surgery: A Systematic Review

PURPOSE

The objective of the present systematic review was to test the hypothesis of no difference in neurosensory disturbances (NSDs) after bilateral sagittal split osteotomy (BSSO) with piezoelectric surgery compared with conventional techniques.

MATERIALS AND METHODS

A PubMed (Medline), Embase Library, and Cochrane Library search in combination with a manual search of relevant journals was conducted from January 2000 to November 2017. Randomized controlled trials and controlled trials in humans were considered. Primary outcome measures (assessment of neuro-sensitivity by subjective and objective evaluations) and secondary outcome measures (NSD risk factors, patient-reported outcome measures, complications, operating time, and intraoperative bleeding) were considered.

RESULTS

The search provided 241 studies of which 5 eligible studies were included. Meta-analysis was not possible because of considerable heterogeneity. Two studies were characterized by a moderate risk of bias and 3 were characterized by a high risk of bias. Piezoelectric surgery substantially decreased NSDs as evaluated by subjective tests. NSD after BSSO varied from 1.8 to 23.0% with piezoelectric surgery and from 7.3 to 52.0% with conventional techniques after 2 to 12 months. Furthermore, piezoelectric surgery seemed to considerably decrease the frequency of intraoperative bleeding in bimaxillary procedures and decrease the risk of an unfavorable split of the mandible and macroscopic damage of the inferior alveolar nerve.

CONCLUSIONS

The hypothesis of no difference in NSD after BSSO with piezoelectric surgery compared with conventional techniques could be neither confirmed nor rejected owing to insufficient knowledge. However, piezoelectric surgery seems to decrease the risk of NSDs after BSSO compared with conventional techniques. Long-term randomized controlled trials comparing the 2 treatment modalities by standardized subjective and objective electrophysiologic tests are needed before one treatment modality can be considered superior to another.

Does Sensory Retraining Improve Subjective Rating of Sensory Impairment after Bilateral Sagittal Split Osteotomy?

Background:

Sensory retraining could ameliorate neurosensory disturbance (NSD) resulting from the injury of the inferior alveolar nerve after a bilateral sagittal split osteotomy (BSSO). The aim of this study was to measure the effects of sensory retraining on NSD.

Methods:

A randomized, prospective, single-blinded clinical trial was conducted on consecutive patients with NSD resulting from a BSSO to correct skeletal class III malocclusion. The outcome measurement of sensory recovery was performed using a patient-centered survey assessed by the total score of questionnaire (TSQ) and visual analogue scale (VAS) at preoperation (T0), 1 week after surgery (T1), each month from 1 to 6 months after surgery (T2–T7), and 1 year after surgery (T8).

Results:

In total, 115 consecutive patients were randomized into a control group (56 patients without sensory retraining) or study group (59 patients with sensory retraining). TSQ and VAS values continually decreased from T1 to T8 in both groups. The study group tended to have lower, but not significantly lower, TSQ and VAS values than the control group at each postoperative time point. Women and men responded similarly to sensory retraining at each time point. The oldest patients did not respond well to sensory retraining, compared with the youngest patients, from T1 to T8, and this age effect evaluated by the VAS reached a significant difference at T7 and T8.

Conclusion:

NSD, assessed by the TSQ and VAS, continually decreased over time after the BSSO. Sensory retraining could improve NSD, but not significantly.

Relationship Between the Quantity of Nerve Exposure During Bilateral Sagittal Split Osteotomy Surgery and Sensitive Recovery

AIM AND OBJECTIVES

The purpose of this study was to evaluate how different exposures of the V3 nerves during orthognathic surgery impact neurosensory disturbances.

METHODS

The study included 127 patients who underwent either bilateral sagittal split osteotomy (BSSO) or BSSO with maxillary le Fort 1. They were divided into 6 groups, identified by the quantity of V3 nerve exposure. All patients were examined in a pre-op period and again after 1, 3, 6 months post-op. The standardized tests used were to clarify the objective and subjective neurosensory status of the exposed nerve. Neurosensory evaluation included; a pin prick test, the 2 points discriminator, light touch, warm and cold tests, and blunt discrimination. They were all done bilaterally on the lower lip area.

RESULTS

In only 2 patients the nerve was damaged during surgery and thus they were not included in this study. In 10.2% of patients there was no nerve exposure, 25.2% had longitudinal vestibular segment nerve exposed, 22.8% had the longitudinal upper-vestibular segment exposed, 20.5% had the longitudinal lower-vestibular segment exposed, 14.2% had the longitudinal upper-lower-vestibular segment exposed, and in 7.1% of patients the nerve was totally exposed. Given the estimated time of 1 month there was 100% recovery in patients whose nerve was unexposed. Considering the other patients, the authors had a variable number of patients who did not recover completely.

CONCLUSION

The authors estimate a correlation between the recovery time and the quantity of the exposed nerve. There is a high incidence of neurosensory disturbance in the lower lip and chin after BSSO and intraoperative quantity of nerve exposure.

Transversal Width of Mandibular Bone and Neurosensory Disturbance after Bilateral Sagittal Splitting Ramus Osteotomy

Objective

This study evaluated the condition of mandibular cancellous and cortical bone on computed tomography (CT) images in order to investigate its relationship with the incidence of neurosensory disturbances (NSD) in the mental nerve region after bilateral sagittal splitting ramus osteotomy (BSSRO).

Methods

BSSRO was performed on 58 lateral mandibles in 29 patients. From preoperative CT images, the width endpoints of the transversal bone were measured in region I immediately inferior to the mandibular foramen, region II in the mandibular angle region, and region III distal to the lower second molar. The incidence of NSD immediately after surgery and the residual NSD rate at 1, 3, and 6 months after surgery were investigated. The correlation between incidence of NSD in the mental nerve region and each transversal bone width endpoint immediately after and at 6 months after surgery was also comparatively evaluated.

Results

The overall incidence of NSD immediately after surgery was 67.2% (39/58 sides) and the overall residual NSD rate at 1, 3, and 6 months after surgery was 53.4% (31/58 sides), 31.0% (18/58 sides), and 17.2% (10/58 sides), respectively. No significant differences were observed for any width endpoints of the transversal bone measured at regions I or III, but the transversal width of the entire mandible was significantly different in region II between patients with and without NSD at 6 months after surgery (p < 0.05).

Conclusion

These findings demonstrate that the transversal width of the entire mandible may be an important factor in predicting NSD incidence.

Hypoesthesia associated with mandibular movement after sagittal split ramus osteotomy

PURPOSE

This retrospective study investigated the relationship between the degree of neurosensory disturbance (NSD) and mandibular movement distance after sagittal split ramus osteotomy (SSRO) and assessed sensory recovery.

METHODS

Lower lip hypoesthesia was evaluated at 1 week, 1 month, and 2 months after SSRO in 38 patients categorized according to the distance of mandibular movement: S group (0-7 mm; n = 17, 4 males and 13 females) and L group (7-14 mm; n = 21, 7 males, 14 females). Symptoms were evaluated by visual analog scale (VAS), tactile-threshold (SW) test, static 2-point discrimination (s-2PD) test, and current perception threshold (CPT) test.

RESULTS

The two groups did not differ significantly in gender and age. The Aβ fiber results of the CPT test differed significantly between the groups at 1 week and 1 month postsurgery (P < 0.05). There were no significant differences between the groups throughout the period in terms of VAS, SW, s-2PD, Aδ fiber, and C fiber of CPT.

CONCLUSIONS

Post-SSRO, the incidence of NSD in terms of tactile sensation may be greater in the L group early postoperatively. This may assist surgeons in explaining postoperative hypoesthesia to patients preoperatively.

Influence of anatomic position and intraoperative exposure of the inferior alveolar nerve on neurosensory disturbance after sagittal split ramus osteotomy: a three-dimensional computed tomography study

OBJECTIVE

To evaluate the influence of the anatomic position and intraoperative exposure of the inferior alveolar nerve on neurosensory disturbance (NSD) in sagittal split ramus osteotomy.

STUDY DESIGN

The anatomic factors of the nerve were measured on preoperative three-dimensional computed tomography in 98 patients. The intraoperative nerve exposure was assessed. NSD was evaluated for 1 year after surgery. The correlations between NSD and the factors were analyzed.

RESULTS

The NSD decreased as the lateral marrow space from the nerve increased (P < .01). The complete nerve exposure increased NSD by 7.6 times (P = .01). The nerve exposure increased as the buccal plate thickness increased (P = .01) and decreased as the vertical marrow space from the nerve increased (P = .01).

CONCLUSIONS

The nerve exposure and the lateral marrow space from the nerve affected NSD. The buccal plate thickness and the vertical marrow space indirectly affected NSD through nerve exposure.

A spatial association between odontomas and the gubernaculum tracts

OBJECTIVES

The purpose of this study was to identify the spatial relationship and/or association between odontomas and the gubernaculum tract or the dental sac and the characteristic findings for radiographic diagnosis of odontomas.

STUDY DESIGN

The visualizations of the odontomas and the gubernaculum tract were retrospectively analyzed using cone beam computed tomography or multidetector computed tomography.

RESULTS

Most of odontomas were within the gubernaculum tract or dental sac of unerupted permanent teeth on computed tomography. In some odontomas, the gubernaculum tract existed as a well-defined low density tract extending from the top of odontomas on computed tomography.

CONCLUSIONS

A close spatial relationship and/or association between odontomas and the gubernaculum tract or dental sac on computed tomography may be used as one of the criteria for radiographic diagnosis of odontomas. Development of odontomas may be associated with the gubernaculum tract or dental sac of unerupted permanent teeth.

Morphological features of the mandible as predictors for neurosensory disturbances after bilateral sagittal split osteotomy

This retrospective study aimed to identify anatomical predictors of neurosensory disturbance (NSD) after bilateral sagittal split ramus osteotomy (BSSO) by evaluating the morphology of the mandible on lateral cephalograms (LCs) and orthopantomograms (OPTs). The LCs and OPTs of 142 patients who underwent BSSO were reviewed. The influence of the mandibular angle was assessed on LCs, while the following morphological landmarks and subsequent measurements were analysed on OPTs: vertical and horizontal positions of the lingula, ramus width, mandibular body height, mandibular canal position and mandibular angle length. Post-operative NSD (hypoaesthesia) was considered permanent when objective tests or subjective evaluations indicated altered sensation one year after BSSO. Generalised linear mixed models were used to take into account the repeated measurement design (left and right measurements within one patient). Hypoaesthesia was present in 10.6% of the patients (5.6% of sites). After adjusting for age, a small mandibular body height was found to significantly increase the risk of hypoaesthesia. The other measurements showed no significant association with hypoaesthesia. These findings show a relationship between mandibular morphology and hypoaesthesia after BSSO and can aid surgeons in pre-operative assessments of the risk of NSD. Further research is needed to identify risk factors for NSD based on mandibular morphology.

Changes in the computed tomography (pixel) value of mandibular ramus bone and fixation screws after sagittal split ramus osteotomy

The purpose of this retrospective study was to evaluate the changes in computed tomography (CT) values of ramus bone and screws after sagittal split ramus osteotomy (SSRO) setback surgery. The subjects were 64 patients (128 sides) who underwent bilateral SSRO setback surgery. They were divided into six groups according to the fixation plate type used and the use or not of self-setting α-tricalcium phosphate (Biopex): group 1: titanium plate and screws; group 2: titanium plate and screws with Biopex; group 3: poly-l-lactic acid (PLLA) plate and screws; group 4: PLLA plate and screws with Biopex; group 5: uncalcined and unsintered hydroxyapatite particles and poly-l-lactic acid (uHA/PLLA) plate and screws; group 6: PLLA/uHA plate and screws with Biopex. CT values (pixel values) of the lateral cortex, medial cortex, osteotomy site, and screws were measured preoperatively, immediately after surgery, and 1 year postoperatively using horizontal CT images at the mandibular foramen taken parallel to the Frankfort horizontal plane. There were significant differences in the time-course change of pixel values for the lateral cortex (P<0.0001) and the osteotomy site (P<0.0001) among the six groups. This study suggests that the fixation plate type and use of bone alternative material may affect bone quality during the process of bone healing after SSRO.

Bone Replacement Materials and Techniques Used for Achieving Vertical Alveolar Bone Augmentation

Alveolar bone augmentation in vertical dimension remains the holy grail of periodontal tissue engineering. Successful dental implant placement for restoration of edentulous sites depends on the quality and quantity of alveolar bone available in all spatial dimensions. There are several surgical techniques used alone or in combination with natural or synthetic graft materials to achieve vertical alveolar bone augmentation. While continuously improving surgical techniques combined with the use of auto- or allografts provide the most predictable clinical outcomes, their success often depends on the status of recipient tissues. The morbidity associated with donor sites for auto-grafts makes these techniques less appealing to both patients and clinicians. New developments in material sciences offer a range of synthetic replacements for natural grafts to address the shortcoming of a second surgical site and relatively high resorption rates. This narrative review focuses on existing techniques, natural tissues and synthetic biomaterials commonly used to achieve vertical bone height gain in order to successfully restore edentulous ridges with implant-supported prostheses.

Detection and imaging characteristics of the gubernacular tract in children on cone beam and multidetector computed tomography

PURPOSE

To elucidate the appearance and imaging characteristics of the gubernacular tract (GT) during the growth stage of children. Furthermore, this study evaluated the significance of the appearance of the GT.

STUDY DESIGN

The visualizations of the GT were retrospectively analyzed by using panoramic radiographs and computed tomography (CT) in children.

RESULTS

In patients with normal eruption who had unerupted permanent teeth, except maxillary central supernumerary teeth, the GT was clearly visualized as a well-defined low-density tract on CT but not on panoramic radiographs. In patients with obstructive eruption, including impaction, the GT was deformed and not visible on CT.

CONCLUSIONS

This paper describes the frequency of detection and appearance of the GT in unerupted teeth. Preliminary data suggest that any alteration to the GT may be used to predict abnormal eruption of permanent teeth.

Systematic review of preoperative mandibular canal position as it relates to postoperative neurosensory disturbance following the sagittal split ramus osteotomy

The purpose of this study was to review the current literature for the relationship between the preoperative position of the mandibular canal on three-dimensional (3D) radiographic imaging and postoperative neurosensory disturbance (NSD) following a sagittal split ramus osteotomy (SSRO). A literature search was conducted using PubMed, EMBASE, and the Cochrane Database for articles published from 1 January 2000 through 31 December 2013. Studies that included preoperative 3D imaging and assessment of NSD after surgery were reviewed. Study sample characteristics and results were extracted. Of the 69 articles identified, seven met the inclusion and exclusion criteria. There was no standardization for measuring the canal position or for evaluating NSD. General consensus was that the less space between the mandibular canal and the outer border of the buccal cortex the more frequent the occurrence of NSD. Increased bone density also appeared to contribute to a higher incidence of NSD. Utilization of 3D images to locate and measure the position of the mandibular canal is not standardized. Advances in 3D imaging and evaluation tools allow for new methodologies to be developed. Early attempts are informative, but additional studies are needed to verify the relationship between the location of the nerve and NSD following surgery.

Quantitative evaluation of cortical bone thickness in mandibular prognathic patients with neurosensory disturbance after bilateral sagittal split osteotomy

PURPOSE

The buccal cortical thickness (BCT) between the mandibular canal and the corresponding external cortical surface was compared in patients with and without neurosensory disturbance (NSD) after they underwent a bilateral sagittal split osteotomy (BSSO) to correct mandibular prognathism.

PATIENTS AND METHODS

This prospective cohort study was conducted in 146 patients (95 women, 65.1%; 51 men, 34.9%) 18 to 39 years old who underwent bimaxillary surgery (ie, Le Fort I osteotomy and BSSO) to correct mandibular prognathism. NSD was identified using a light touch test with a Semmes-Weinstein monofilament and a pricking pain test with a sharp dental explorer 1 week after surgery. Preoperative cone-beam computed tomographic (CBCT) imaging was used to visualize the bone contacts or fusion of the mandibular canal to the buccal cortical bone and to decrease injury to the mandibular nerve during surgical dissection. Preoperative CBCT imaging also was used to assess the BCT every 2 mm from the mandibular foramen to the furcation of the mandibular first molar in the NSD group and the sensory normal (N) group.

RESULTS

The incidence of NSD was 32.5% at 1 week after surgery. There was no statistically significant difference between men and women, the side affected, or genioplasty at the time of undergoing BSSO. Of the total sample group, decreased BCT was identified throughout the observed length of the mandibular canal in the NSD group compared with the N group. Statistically significant decreased BCTs were 16 to 20 mm and 24 mm in the total sample, 6 to 8 mm in the female group, and 16 to 18 mm in the male group.

CONCLUSION

Compared with the N group, BCTs in the NSD group were always decreased, especially those located at 16 to 20 mm and 24 mm in the total sample, 6 to 8 mm in the female group, and 16 to 18 mm in the male group.

Lower-level laser therapy improves neurosensory disorders resulting from bilateral mandibular sagittal split osteotomy: a randomized crossover clinical trial

Bilateral sagittal split osteotomy (BSSO) is a technique commonly used to correct mandibular disproportion but many patients experience hypoaesthesia of the inferior alveolar nerve (IAN). The purpose of this study was to verify the effectiveness of using a low-level laser therapy protocol after BSSO. The 10 patients in our study, who underwent BSSO with Le Fort I osteotomy and had low-level laser therapy on one side of the jaw, were evaluated over a period of 60 days. The data for the treated and non-treated sides were compared post-operatively. At 15, 30 and 60 days after surgery, when sensitivity was recovered on both sides. On the treated side, recovery was faster and was almost complete at the time of the last evaluation. We suggest that this lower-level laser therapy protocol can improve tissue response and accelerate the recovery of neurosensory disorders following BSSO. (NCT01530100).

Review of orthognathic surgery and related papers published in the British Journal of Oral and Maxillofacial Surgery 2011-2012

This review summarises all orthognathic and related papers published between January 2011 and December 2012 in the British Journal of Oral and Maxillofacial Surgery (BJOMS). A total of 36 articles were published, a high proportion of which (78%) were full-length papers. The remainder consisted of short communications and technical notes. The topics included operative planning and postoperative outcomes, and there was a strong focus on distraction osteogenesis. There were fewer orthognathic articles published in BJOMS than articles on other subspecialties such as trauma or head and neck oncology. Only 8 (29%) of the full-length articles were prospective studies or randomised trials, which highlights a need for well-designed clinical studies in orthognathic research.

Full length articles published in BJOMS during 2010-11--an analysis by sub-specialty and study type

Full length articles such as prospective and retrospective studies, case series, laboratory-based research and reviews form the majority of papers published in the British Journal of Oral and Maxillofacial Surgery (BJOMS). We were interested to evaluate the breakdown of these types of articles both by sub-specialty and the type of study as well as the proportion that are written by UK colleagues compared to overseas authors over a 2 year period (2010-11). A total of 191 full length articles across all sub-specialties of our discipline were published, with 107 papers (56%) coming from UK authors. There were proportionately more oncology papers arising from the UK than overseas (60 and 30% of total respectively) while the opposite was found for cleft/deformity studies (10% and 22%). There was only one laboratory-based study published from the UK compared with 27 papers from overseas. The number of quality papers being submitted to the Journal continues to increase, and the type of article being published between UK and overseas probably reflects different practices and case-loads amongst colleagues. The relatively few UK laboratory based studies published in BJOMS compared to overseas authors are most likely due to authors seeking the most prestigious journals possible for their work.