The median lingual foramen in the era of orthognathic virtual surgical planning.

The median lingual foramen (MLF), which contains neurovascular bundles, is located in an area commonly considered safe for surgical procedures. However, published reports of severe complications after interventions in the mandibular symphysis area indicate the need for caution when approaching this region surgically. The aim of this study was to evaluate the vertical location of the MLF and the median lingual canal (MLC) by measuring the distances of these landmarks to the root apex of the lower central incisors (LCI) and to the menton cephalometric point (Me) on pre-orthognathic surgery cone beam computed tomography scans (N = 100). The results were analyzed in relation to the patients' type of deformity, age, sex, and number of foramina (single vs multiple). The median MLF-LCI and MLF-Me distances were 5.9 mm and 15.0 mm, respectively, while the mean MLC-LCI and MLC-Me distances were 9.7 mm and 11.6 mm, respectively. The mean LCI-Me distance was 21.3 mm, while the mean MLC length was 3.4 mm. Apart from the length of the MLC, the distances were all significantly greater in the male patients than in the female patients. The MLC-Me distance and MLC length differed significantly according to the number of foramina. In preoperative planning, the vertical locations of the MLF and respective MLC appear to be relevant for avoiding neurovascular complications.

Are we able to predict airway dimensional changes in isolated mandibular setback?

The goal of this study was to determine whether a relationship exists between the amount of mandibular setback and the amount of airway dimensional changes. Records and cone beam computed tomography (CBCT) of patients who had undergone isolated bilateral sagittal split osteotomy setback between January 1, 2013 and March 16, 2020 at a single institution were reviewed retrospectively. The primary outcome variable was upper airway volume dimension change, and the predictor variable was the magnitude of mandibular setback as measured by six different methods. Thirty-one patients were included in the study, with a mean mandibular setback ranging from 1.41 mm to 6.11 mm. None of the predictor variables showed an association with oropharyngeal (P = 0.54) or hypopharyngeal (P = 0.33) volume. Stepwise regression analysis failed to show any significant relationships. Similarly, there was no statistically significant association between any of the predictor variables and oropharyngeal (P = 0.44) or hypopharyngeal (P = 0.74) minimum axial area. The results showed that no correlation exists between the magnitude of mandibular setback and the amount of static airway dimensional changes; therefore, it may not be possible to predict whether obstructive sleep apnea will develop following mild to moderate mandibular setback based upon CBCT measurements.

Does a learning curve exist for accuracy in three-dimensional planning for maxillary positioning in bimaxillary orthognathic surgery?

The purpose of this study was to investigate the influence of time, and experience, on the accuracy of maxillary repositioning in bimaxillary orthognathic surgery performed using virtual surgical planning (VSP). Patients who had undergone bimaxillary orthognathic surgery were reviewed. Maxillary position on pre- and postoperative computed tomography scans was compared. The patients were divided into groups according to the year in which VSP was performed and surgery completed. Linear distances between upper jaw reference landmarks were measured in all three planes of space to determine accuracy between the preoperative VSP and the surgical outcome at various time points. One hundred subjects met the eligibility criteria for assessment and were allocated to groups: 2013 (n=10), 2014 (n=17), 2015 (n=39), 2016 (n=20), and 2017 (n=14). Overall, the results demonstrated improved precision in maxillary position over the years, with more accurate results in patients who underwent surgery in 2015, 2016, and 2017. Mean linear differences between planned and obtained results demonstrated more accurate results in the horizontal direction, followed by transverse and vertical directions. An overall average difference within 1mm was observed for 51.3% of the measurements included in the sample group. Time, and surgeon experience, can influence the accuracy of maxillary positioning in bimaxillary orthognathic surgery.

Mandible-first sequence in bimaxillary orthognathic surgery: a systematic review.

The sequencing of bimaxillary orthognathic surgery remains controversial, although the traditional maxilla-first approach is performed routinely. The goal of this study was to present a systematic review of the mandible-first sequence in bimaxillary orthognathic surgery, to provide data that may assist in the decision as to which jaw should undergo osteotomy first in bimaxillary orthognathic surgery cases. A literature search was conducted for articles published in the English language, reporting the use of the altered sequence for bimaxillary orthognathic surgery (mandible-first), using the following descriptors: 'orthognathic' and 'double-jaw', 'orthognathic' and 'two-jaw', 'orthognathic' and 'mandible-first', 'orthognathic' and 'bimaxillary'. Eight hundred eighty-seven abstracts were initially identified and were evaluated for inclusion according to the proposed inclusion criteria. After evaluation of these abstracts and relevant references, six publications met the criteria for consideration. Performing mandible-first surgery in bimaxillary orthognathic cases dates back to the 1970s; however the decision regarding the jaw to be operated on first seems to rely on accurate preoperative planning based upon the surgeon's experience and preference. While there appear to be significant theoretical advantages to support the use of the altered orthognathic sequence (mandible-first), future prospective studies on its reliability, accuracy, and short- and long-term outcomes are required.

Accuracy of perioperative mandibular positions in orthognathic surgery.

Mandibular position is an important parameter used for the diagnosis of dentofacial deformities, as well as for orthognathic surgery planning and execution. Centric relation (anterior and superior relationship of the mandibular condyles interposed by the thinnest portion of their disks against the articular eminencies), centric occlusion (when lower teeth contact upper teeth at centric relation), and maximal intercuspation (complete interdigitation of lower and upper teeth) are not often addressed as factors that influence the results of orthognathic surgery, although these relationships are critical to ensure accuracy during the surgery. The present study assessed occlusal measurements taken before and after the induction of general anaesthesia from consecutive orthognathic surgery subjects. The variables assessed included the differences between these occlusal measurements, patient age, gender, type of deformity, and type of proposed orthognathic surgical procedure. The results demonstrated statistically significant differences for mandibular retrusion from maximal intercuspation to centric occlusion position, whereas the mandible appeared not to change significantly from centric occlusion after the induction of general anaesthesia. Patient age and the type of deformity appeared to influence the results. While in most instances centric occlusion can be adequately reproduced under general anaesthesia, for some specific orthognathic cases more accurate results might be obtained if the mandible-first sequence is used.

Is there consistency in cephalometric landmark identification amongst oral and maxillofacial surgeons?

There may be significant variation amongst oral and maxillofacial surgeons (OMFS) in the identification and placement of cephalometric landmarks for orthognathic surgery, and this could impact upon the surgical plan and final treatment outcome. In an effort to assess this variability, 10 lateral cephalometric radiographs were selected for evaluation by 16 OMFS with different levels of surgical knowledge and experience, and the position of 21 commonly used cephalometric landmarks were identified on radiographs displayed on a computer screen using a computer mouse on a pen tablet. The database consisted of real position measurements (x, y) to determine the consistency of landmark identification between surgeons and within individual surgeons. Inter-examiner analysis demonstrated that most landmark points had excellent reliability (intra-class correlation coefficient >0.90). Regardless of the level of surgeon experience, certain landmarks presented consistently poor reliability, and intra-examiner reliability analysis demonstrated that some locations had a higher average difference for both x and y axes. In particular, porion, condylion, and gonion showed poor agreement and reliability between examiners. The identification of most landmarks showed some inconsistencies within different parameters of evaluation. Such variability among surgeons may be addressed by the consistent use of high-quality images, and also by periodic surgeon education of the definition of the specific landmarks.

Keratocystic odontogenic tumors and Carnoy's solution: results and complications assessment.

OBJECTIVE: Keratocystic odontogenic tumors (KOTs) can be treated with Carnoy's solution, although this treatment modality is not free from complications. It is important to verify the incidence of complications after the use of Carnoy's solution and compare these with the literature. MATERIALS AND METHODS: This study verified the effects of a complementary treatment for KOTs and assessed the incidence of such complications as recurrence, infection, sequestrum formation, mandibular fracture, dehiscence, and neuropathy. RESULTS: Twenty-two KOTs treated with Carnoy's solution combined with peripheral ostectomy were included, and the follow-up period varied from 12 to 78months with a mean of 42.9months. Complications included recurrence (4.5%), dehiscence (22.7%), infection (4.5%), and paresthesia (18.2%). No difference was found among lesions associated (9.1%) or not (0%) with nevoid basal cell carcinoma syndrome (P>0.05). Dehiscence was influenced by marsupialization (P<0.05), and paresthesia was observed exclusively in cases of mandibular canal fenestration (P<0.01). CONCLUSIONS: Complementary treatment with Carnoy's solution and peripheral ostectomy appear to provide efficient treatment for KOTs. Complications originating from the use of the solution are less frequent and less serious than complications associated with cryotherapy. Neuropathy seems to be related to direct contact between the solution and the epineurium.