Postoperative fractures of the lingual plate after bilateral sagittal split osteotomies

Age and gender variations in the cone-beam computed tomographic location of mandibular canal: Implications for mandibular sagittal split osteotomy

Background

Mandibular sagittal split osteotomy (MSSO) may incur unfavorable split and sensorineural injuries. Knowledge of the anatomic location of the mandibular canal (MC) and bone thickness in the region of interest for MSSO, and the possible variations by age and gender can assist in avoiding such complications. Purpose: To study the location of the MC and bone thickness in the region of MSSO by cone-beam computed tomography (CBCT) radiographs and to evaluate the possible variations by age and gender in a Jordanian population.

Material and Methods

This retrospective radio-anatomical study examined all CBCT radiographs for patients treated over three years at the University of Jordan Hospital, Amman, Jordan. Distances from the MC to the cortical external surfaces and MC diameter (MCD) were measured by a reliable observer at three predetermined regions for MSSO: region (A) [mandibular foramen area], region (B) [mandibular angle area] and region (C) [directly mesial to the second molar]. Gender and age differences in all measurements were then compared using non-parametric Mann-Whitney U test.

Results

The final study radiographs comprised a total of 202 CBCT belonged to a cohort of 202 subjects; 91 males (45.1%) and 111 (54.9%) females, with mean age (± SD) of 42.94 ± 18.54 years (range 18–90 years). Whereas only the bone thickness superior, buccal and inferior to MC in regions (B) and (C), and MCD in the three regions exhibited significant (p< 0.05) gender differences, all measured distances exhibited statistically significant (p< 0.05) differences between young and adult patients.

Conclusions

The location of MC and bone thickness in the region of MSSO were significantly variable according to age, but exhibited sexual diamorphism only in regions (B) and (C). This fundamental knowledge should be considered during MSSO planning.

Key words:Cone-Beam Computed Tomography, mandibular canal, mandibular sagittal split osteotomy.

Intra-oral mandibular sagittal osteotomy technique to correct mandibular distocclusion and mesio-occlusion

Skeletal malocclusions may be due to disturbances in the growth of the mandible or maxilla. In most cases, discomfort is the result of tooth-to-tooth malocclusion or tooth-to-softtissue contact. Currently, in veterinary medicine, these problems are treated palliatively. In humans, orthognathic surgery is indicated to correct severe skeletal malocclusions, offering aesthetic and functional benefits to the patients. This research evaluated the effects of an intra-oral mandibular sagittal split osteotomy in 20 dog cadavers with skeletal malocclusion. After sagittal osteotomy and mandibular repositioning, the osteotomies were fixed with titanium mini-plates and 1.5 mm diameter screws or 1.5 mm bicortical screws. The statistical analysis revealed a significant occlusion difference in the treated cadavers (Wilcoxon test, p <0.05). In 19/20 cadavers there was correction of the angular osteotomy while the mandibular alveolar vessels and nerve were preserved during osteotomy and fixation in all cadavers. In conclusion, intra-oral mandible sagittal osteotomy allowed correction of malocclusion in cadavers. However, it would be important to prepare a preoperative orthodontic-surgical treatment plan to obtain a satisfactory occlusion during the surgery in clinical patients.

Management of Nonsyndromic Skeletal Dysgnathia by Distraction Osteogenesis Long-Term Follow-Up

Distraction osteogenesis has been a paradigm shift in the field of orthognathic surgery. Majority of the published cases are those of syndromic patients that have been managed using varying treatment protocols. This communication describes a patient of 18-year-old male diagnosed with skeletal Class II malocclusion due to mandibular retognathism. The patient was taken up for mandibular corpus distraction of 10 mm. By this approach the patient was benefitted with good esthetic result and functional occlusion. Distraction protocol followed in this patient for lengthening of mandibular corpus has resulted in a stable outcome. The 2-year follow-up photographs show a stable result both esthetically and functionally.

CBCT location of the fusion between the buccal and lingual cortical in the mandibular ramus: importance to sagittal split osteotomy

Background

Mandibular Sagittal Split Osteotomy (MSSO) is a popular technique in orthognathic surgery used both to advance and to retreat the mandible. However, MSSO may incur in important complications, such as bad splits and sensorineural injuries. Knowing the location of the fusion between the buccal and lingual cortical (FBLC) in the mandibular ramus and the bone thickness in the region where osteotomies will be performed is determinant in MSSO planning to avoid complications. The aim of this study was to document and evaluate possible differences between sexes regarding the location of the FBLC in relation to the superior cortical of mandibular foramen (MF) and bone thickness in the region of interest for MSSO in a Brazilian population.

Material and Methods

Eighty five cone-beam Computed Tomography (CBCT) scans were used to perform linear measurements to determine the location of the FBLC. Bone thickness from the mandibular canal (MC) to the cortical external surfaces and the diameter of the MC were measured at three different points: mandibular ramus (A), mandibular angle (B) and mesial of the second molar (C).

Results

The FBLC was located at a mean distance of 8.3 mm from the superior cortical of the MF in males and 8.1 mm in females. There was no difference between males and females regarding the mean bone thickness from the MC to the buccal external surface at all the points investigated (p >>0.05). Bone thickness from the lingual external surface to the MC was bigger among females than males in regions B and C (p<0.05). The diameter of the MC was bigger among males in regions B and C.

Conclusions

Sexual dimorphism regarding mandibular bone thickness but not regarding the location of FBLC was present. This fundamental knowledge may assist to the panning of MSSO.

Key words:Cone-Beam Computed Tomography, mandibular nerve, orthognathic surgery, sagittal split ramus osteotomy.

Impacted third molars in sagittal split osteotomies in mandibular prognathism and micrognathia

BACKGROUND

The timing of removal of mandibular third molars (M3) in Sagittal Split Osteotomy (SSO) has been an issue of contention. The aim of this retrospective study is to identify the incidence of unfavorable fractures during SSO with the presence of M3 and to identify the association between unfavorable fractures with the factors specifically related to the M3.

MATERIALS AND METHODS

Retrospective analysis of consecutive bilateral sagittal split osteotomy (BSSO) patient's treatment records of 208 patients treated by a single surgeon was analyzed. The position of M3, fracture details, and demographics were collected. Descriptive statistics and Chi-square tests were employed in SPSS package. A P ≤ 0.05 was taken as significant.

RESULTS

There were altogether 416 SSO performed. M3 was completely impacted in 88.9% of all instances, and in 85.6% of the instances, the bulk of the M3 was identified to be above the external oblique ridge. In 59.4% of the cases, M3 was positioned in alignment with the arch as observed during surgery. There were about 27 (6.5%) instances of unfavorable splits. A statistically significant relationship was observed with M3 root morphology and axial position of M3.

DISCUSSION

This study for the first time has confirmed the spatial positioning of M3 as one of the several causes of unfavorable splits during SSO. An impacted M3 that lies below the oblique ridge, distoangularly/vertically oriented, with divergent/supernumerary root would cause unfavorable splits when the spreader is not used properly. Potential causes and influencing factors of the unfavorable splits are discussed.

A Bony Landmark 'RAI Triangle' to Prevent 'Misplaced and Misdirected' Medial Cut in SSRO

'Rai triangle', a new anatomic landmark on the medial surface of the ramus of the mandible which when identified and taken into consideration, may have a definite advantage. This is especially in terms of performing the medial horizontal cut which is an important and integral part of the sagittal split ramus osteotomy so as to avoid a bad split. The objective of this article is to propose an easily identifiable bony land mark, which is closely related to lingula of mandible that may ease the procedure of osteotomy and avoid bad splits.

The presence of mandibular third molars during sagittal split osteotomies does not increase the risk of complications

PURPOSE

The purpose of this study was to investigate prospectively the effects of the presence or absence of third molars during sagittal split osteotomies (SSOs) on the frequency of unfavorable fractures, degree of entrapment and manipulation of the inferior alveolar nerve (IAN), and procedural time.

MATERIALS AND METHODS

The investigators designed and implemented a prospective cohort study and enrolled a sample composed of patients who underwent SSOs to correct mandibular deformities. The primary predictor variable was the status of the mandibular third molar at the time of SSO, and it was divided into 2 levels, present at the time of SSO (group I) or absent at the time of SSO (group II). The primary outcome variable was unfavorable splits. The secondary outcome variables were the degree of entrapment/manipulation of the IAN and the procedural time. Appropriate bivariate and multivariate statistics were computed, and the level of statistical significance was set at P < .05.

RESULTS

Six hundred seventy-seven SSOs were performed in 339 patients: group I consisted of 331 SSOs (mean age ± SD: 19.6 ± 7.4 yrs), and group II consisted of 346 SSOs (30.4 ± 12.1 yrs). The overall rate of unfavorable fractures was 3.1% (21 of 677), with frequencies of 2.4% (8 of 331) in group I, compared with 3.8% (13 of 346) in group II (P = .3). The rate of IAN entrapment in the proximal segment was significantly lower in group I (37.2%) than in group II (46.5%; P = .01). The degree of entrapment was also significantly more severe for group II (P < .001). Third molars increased procedural time by 1.7 minutes (P < .001).

CONCLUSIONS

The presence of third molars during SSOs is not associated with an increased frequency of unfavorable fractures. Concomitant third molar removal in SSOs also decreases proximal segment IAN entrapment but only slightly increases operating time.

An unusual fracture of the mandible 20 months after a split sagittal osteotomy

An unusual fracture of the mandible is reported that occurred 20 months after a bilateral split sagittal osteotomy.