Do lower third molars increase the risk of complications during mandibular sagittal split osteotomy? Systematic review and meta-analysis

Biomechanical effects of mandibular deviation on the temporomandibular joint in patients with mandibular prognathism under incisal occlusion

PURPOSE

The aim of this study was to investigate the biomechanical effects of mandibular deviation on the TMJ in patients with mandibular prognathism before and after orthognathic surgery using three-dimensional finite element analysis.

METHODS

Eight patients with mandibular prognathism without deviation, eight patients with mandibular prognathism with deviation and sixteen normal subjects were recruited. Three-dimensional models of the maxillofacial were reconstructed using MIMICS. Nine muscle forces were used to simulate incisal occlusion and contact was used to simulate fossa-disc-condyle interactions.

RESULTS

Before surgery, the stress in the TMJ was generally greater in the Pre-MD&MP group than in the Pre-MD group; it was much greater in both groups than in the control group, ranging from about 2 to 12 times as great in the Pre-MD group and from about 5 to 64 times as great in the Pre-MD&MP group. After orthognathic surgeries, the stresses in the Post-MP&MD were significantly reduced by approximately 21.7 % to 93.4 %. And in the Post-MP group, the stresses were reduced by approximately 1.4 % to 51.1 %.

CONCLUSION

Mandibular deviation exacerbated the abnormal stress distribution in the TMJ of patients with mandibular prognathism. Orthognathic surgeries could improve the stress distribution in patients with mandibular prognathism (with and without deviation). TMD was closely related to the stress levels of the TMJ.

Current Orthognathic Surgery Practice Patterns Among Academic OMS

OBJECTIVE

Currently there is variation in perioperative care of orthognathic surgery patients and limited clinical practice guidelines. The current orthognathic surgery practice patterns among US academic OMFS training centers have not been described. The purpose of this study is to describe the practice patterns among US academic OMFS training centers.

DESIGN

The study design is cross-sectional. Data was collected through a survey of the sample.

SETTING

OMFS programs in the US.

PARTICIPANTS

Academic OMFS. 573 surgeons were contacted and 85 responses were received.

MAIN OUTCOME MEASURE

Descriptive and bivariate statistics were reported.

RESULTS

Respondents were 87% male and worked in full-time academic (80%), part-time academic (19%), or military settings (1%). Thirty-one percent have practiced for 30 years or more and then 29% with 11-20 years, 18% with 21-30 years, 12% with 6-10 years and 11% with 1-5 years. Twenty-six percent of respondents perform 20-40 orthognathic surgeries a year, 22% perform less than 20 surgeries a year, 21% perform 40-60 surgeries per year, and 19% perform more than 100 surgeries per year. Intraoperatively, 48% of surgeons request a mean arterial pressure of 60-64 mmHg, 25% utilize tranexamic acid (TXA), 85% report a blood loss of less than 400 milliliters, and 93% report a blood transfusion rate of <1%.

CONCLUSION

There are variations in orthognathic surgery practice patterns with limited clinical practice guidelines. Only 13 of the 32 survey questions had a single response holding a simple majority. This study demonstrates the need for further research and evidence-based protocols and decision making.

Two-stage extraction by partial grinding of impacted mandibular third molar in close proximity to the inferior alveolar nerve

BACKGROUND

Extraction of impacted third molars often leads to severe complications caused by damage to the inferior alveolar nerve (IAN).

AIM

To proposes a method for the partial grinding of an impacted mandibular third molar (IMM3) near the IAN to prevent IAN injury during IMM3 extraction.

METHODS

Between January 1996 and March 2022, 25 patients with IMM3 roots near the IAN were enrolled. The first stage of the operation consisted of grinding a major part of the IMM3 crown with a high-speed turbine dental drill to achieve sufficient space between the mandibular second molar and IMM3. After 6 months, when the root tips were observed to be away from the IAN on X-ray examination, the remaining part of the IMM3 was completely removed.

RESULTS

All IMM3s were extracted easily without symptoms of IAN injury after extraction.

CONCLUSION

Partial IMM3 grinding may be a good alternative treatment option to avoid IAN injury in high-risk cases.

Bilateral sagittal split osteotomy with or without concomitant removal of third molars: a retrospective cohort study of related complications and bone healing

PURPOSE

To carry out a comparative evaluation of the intra- and postoperative complications, and bone healing, following bilateral sagittal split osteotomy (BSSO) with or without concomitant removal of third molars.

MATERIAL AND METHODS

A retrospective analysis was performed of two cohorts subjected to BSSO with the intraoperative removal of third molars (test group) versus the removal of third molars at least 6 months prior to BSSO (control group), comprising at least 1 year of clinical and radiographic follow-up. Partially or completely erupted third molars were extracted immediately before completing the osteotomy, whereas impacted third molars were removed after the osteotomy had been performed. Hardware reinforcement was performed in bimaxillary cases where concomitant molar extraction impeded placement of the retromolar bicortical screw of the hybrid technique.

RESULTS

A total of 80 surgical sites were included (40 in each group). Concomitant extraction of the molar represented a mean increase in surgery time of 3.7 min (p < 0.001). No additional complications occurred in the test group (p = 0.476). The gain in bone density was preserved in both groups (p = 0.002), and the increase was of the same magnitude in both (p = 0.342), despite the fact that the immediate and final postoperative bone densities were significantly higher in the control group (p = 0.020).

CONCLUSION

The results obtained support concomitant molar extraction with BSSO as a feasible option.

Exploring the relationship between the number of systematic reviews and quality of evidence: an orthognathic surgery-based study

OBJECTIVE

We analyzed the quality and quantity of systematic reviews (SRs) of orthognathic surgery, the most frequently published topic in maxillofacial surgery.

STUDY DESIGN

We searched the PubMed database for SRs of orthognathic surgery with no restriction on the language of publication date. We assessed the certainty of evidence presented according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol and the Leiden Manifesto using the Grading of Recommendations Assessment, Development, and Evaluation approach. We analyzed the data using descriptive statistics, Pearson´s correlation test, and linear regression.

RESULTS

Of the 171 SRs evaluated, approximately one fifth presented evidence with a high level of certainty. The number of orthognathic surgery SRs has been increasing, and many SRs were published after very similar topics had already been published. There is no relationship between the impact factor and the certainty of evidence.

CONCLUSIONS

An excessive number of SRs of orthognathic surgery are published, and many SRs are superfluous, simply reporting previous findings. Clinicians should not base treatment decisions solely on the evidence presented in SRs, and journal editors and reviewers should evaluate these SRs more critically, particularly when they address topics that have already been covered in the literature.

Radiological evaluation of inferior alveolar nerve displacement after removal of impacted mandibular third molars prior to sagittal split osteotomy

INTRODUCTION

We hypothesize that the removal of mandibular third molars (M3) 6 months prior to a bilateral sagittal split osteotomy (BSSO) could allow the displacement of the inferior alveolar nerve (IAN) in a favorable lingual position. This study aimed to radiographically compare the position of IAN before and after M3 removal in patients with Class II malocclusion.

MATERIALS AND METHOD

The CBCT images of 30 randomly selected patients (mean age 15.5 years, 19 females and 11 males) were segmented regarding the mandibular bone and the IAN canal. Mandibles were then superimposed and compared using 3D slicer (www.slicer.org). An orthonormal system was constructed, and the coordinates of IAN were assessed in the x- (horizontal axis), y- (depth axis), and z- (vertical axis) directions.

RESULTS

The mean changes in x- and z-values were 0.37 %, -0.09 % for the right IAN, 0.07 %, and -0.10 % for the left IAN, respectively. Y-axis was the dimension the most impacted by the M3 removal with a mean variation of -11.96 % for the right IAN, and 0.45 % for the left nerve (p1=0.74 and p2=0.04, respectively). Three patients presented a change in the IAN position superior to 1 mm on at least one coordinate axis. We observed a more important change in x-values of the right IAN in male than in female (p = 0.04), and no significant modifications regarding the other dimensions. Finally, there was no correlation between the age of the patients and the changes in IAN position.

CONCLUSION

This study confirms the absence of influence of mandibular third molar removal on the inferior alveolar nerve route prior to BSSO.

Evaluation of the Lingual Splitting Patterns and the Lateral Bone Cut Ends Following Mandibular Bilateral Sagittal Split Osteotomy Using Cone Beam Computed Tomography (CBCT)

The bilateral sagittal split osteotomy (BSSO) is the most popular orthognathic procedure performed by maxillofacial surgeons to treat skeletal class II and class III and to correct mandibular asymmetries. The study aimed to evaluate the lingual splitting patterns and lateral bone cut end (LBCE) in bilateral sagittal split osteotomy (BSSO) and their relation with the ramal thickness and the presence of impacted third molars using cone beam computed tomography (CBCT). This prospective observational study included patients with mandibular prognathism who were treated with BSSO with or without Le Fort I osteotomy. Cone beam computed tomography was used to measure the ramal thickness preoperatively and to evaluate the LBCE, and the lingual splitting patterns postoperatively. Twenty-one patients (42 sides) were included in this study. The most commonly observed lingual splitting pattern was type III (47.6%), while the most common LBCE was type B (59.5%). The bad split was encountered 8 times on 42 sides (16.7%). A nonsignificant relationship between the ramal thickness and bad splitting was observed ( P =0.901). Impacted third molars were present in 16 of the 42 sides (38.1%) and had no significant effect on the occurrence of bad splitting ( P =0.063). Type III lingual splitting pattern and type B LBCE were the most commonly observed patterns. No direct association was observed concerning the presence of impacted mandibular third molars and the thickness of the ramus with the occurrence of bad splitting.

In vivo study of cone beam computed tomography texture analysis of mandibular condyle and its correlation with gender and age

OBJECTIVE

Texture analysis is an image processing method that aims to assess the distribution of gray-level intensity and spatial organization of the pixels in the image. The purpose of this study was to investigate whether the texture analysis applied to cone beam computed tomography (CBCT) images could detect variation in the condyle trabecular bone of individuals from different age groups and genders.

METHODS

The sample consisted of imaging exams from 63 individuals divided into three groups according to age groups of 03-13, 14-24 and 25-34. For texture analysis, the MaZda^® software was used to extract the following parameters: second angular momentum, contrast, correlation, sum of squares, inverse difference moment, sum entropy and entropy. Statistical analysis was performed using Mann-Whitney test for gender and Kruskal-Wallis test for age (P = 5%).

RESULTS

No statistically significant differences were found between age groups for any of the parameters. Males had lower values for the parameter correlation than those of females (P < 0.05).

CONCLUSION

Texture analysis proved to be useful to discriminate mandibular condyle trabecular bone between genders.