What factors affect the attachment of the inferior alveolar nerve to the buccal plate following sagittal split osteotomy?

PurposeThis study aimed to assess the factors that can possibly affect the positioning of the inferior alveolar nerve (IAN) in the proximal or distal segment following sagittal split osteotomy (SSO).Materials and methodsThis was a prospective cohort study. The patients were assigned according to the position of the IAN: the IAN was attached to the buccal plate in group 1 (27 SSOs), while it was in the distal segment in group 2 (83 SSOs).ResultsThe mean of the buccolingual thickness of the proximal segment at the vertical cut of the osteotomy (BLTP) was 5.0 ± 0.62 mm in group 1 and 4.16 ± 0.72 mm in group 2. The mean of the distance between the IAN and the external cortical bone at the distal of the second molar before the osteotomy (IANB) was 0.5 ± 0.24 mm in group 1 and 1.24 ± 0.45 mm in group 2. There were significant differences for the mean BLTP and IANB between the two groups (P = 0.001).ConclusionIt seems that the thickness of the buccal plate of the proximal segment, the distance from the IAN to the external cortical bone, the osteotomy technique, and the presence or absence of impacted third molars may be associated with the positioning of the IAN following SSO.     

How does bone thickness affect the split pattern of sagittal ramus osteotomy?

This study examined the influence of bone thickness on the split pattern of sagittal ramus osteotomy at 62 sites using Dolphin 3D software. Four measurements of thickness were obtained from the preoperative computed tomography scans: measurement A was made 1.5 mm above the lingula, using the coronal and sagittal planes; measurement B was made at the same height as measurement A and 1 mm from the anterior border of the ramus; measurement C was obtained 5 mm distal to the last molar and 5 mm below the upper border of the mandible; measurement D was made in the area between the first and second molars, 6 mm above the mandibular border. Three-dimensional postoperative images were used to classify the split pattern into types, based on the classification of Plooij et al. The data were analyzed using the Kruskal–Wallis test, followed by Dunn post-hoc test. Thirty-five sagittal splits were type I, one was type II, 19 were type III, and seven were type IV. Type I presented the greatest thickness, whereas type IV presented the lowest. There was a statistically significant difference in thickness only for measurement A, when types I and IV were compared. The results indicate that thinner mandibular rami are more prone to bad splits.     

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

The aim of this systematic review was to investigate whether the presence of third molars (3Ms) during sagittal split osteotomy of the mandible increases the risk of complications. Searches were conducted using MEDLINE via PubMed, LILACS, Cochrane Central, Scopus, DOSS, and SIGLE via OpenGrey up to December 2020. Fifteen articles were included for evaluation and 14 in the meta-analysis, with a total of 3909 patients and 7651 sagittal split osteotomies (670 complications). Inferior alveolar nerve (IAN) exposure in the proximal segment was the most frequent complication (n = 409), followed by bad splits (n = 151). Meta-analysis revealed no significant increase in the incidence of 3M-related IAN exposure (P = 0.45), post-surgical infections (P = 0.15), osteosynthesis material removal (P = 0.37), or bad splits (P = 0.23). The presence of 3Ms was associated with a reduced risk of nerve disorder (P = 0.05) and favoured bad splits in the lingual plate (P = 0.005). The quality of evidence was very low, mainly due to non-randomized study designs, high risk of bias, inconsistency, and imprecision. This systematic review suggests that the removal of 3Ms before sagittal mandibular osteotomy does not reduce the incidence of complications. Thus, we recommend future better-designed studies with rigorous methodologies and adjustments for confounding factors.     

Is injury to the inferior alveolar nerve still common during orthognathic surgery? Manual twist technique for sagittal split ramus osteotomy

The osteotomy in a bilateral sagittal split ramus osteotomy (BSSRO) is made in close proximity to the inferior alveolar nerve (IAN), so direct damage to the nerve and irreversible neurosensory deficit may result. The aim of this study was to compare the incidence of injury to the nerve when a conventional osteotomy using an osteotome was made, with that after manual twist splitting. We retrospectively reviewed the casenotes of 769 consecutive patients who had bilateral SSRO either alone or with a simultaneous maxillary procedure by a single surgeon from May 2009 ? October 2016. Patients were divided into two groups based on the technique used. Those in the first group had conventional split osteotomy using an osteotome and hammer for splitting (conventional group, 736 sides), and in those in the second group the manual twist technique was used (manual group, 802 sides). Patients who sustained Sunderland fifth degree injuries were identified from an existing record of nerve repairs. Fisher's exact test was used to evaluate the significance of the number of injuries to the nerve in each group. Conventional osteotomy and hammer-assisted SSRO resulted in 8/736 (1.1%) injuries to the IAN, whereas the manual twist splitting technique resulted in 1/802 injuries (0.1%). Our results confirm that the manual twist splitting technique significantly reduces the incidence of injury to the IAN, though the overall incidence was low.     

Which kind of miniplate to use in mandibular sagittal split osteotomy? An in vitro study

This study verified the resistance to displacement of six miniplate fixation methods after sagittal split osteotomy (SSO). SSO was performed in 30 polyurethane synthetic mandible replicas. The distal segments were advanced (4 mm) and specimens were grouped according to the fixation method: four-hole standard miniplate; four-hole locking miniplate; six-hole standard miniplate; six-hole locking miniplate; six-hole standard sagittal miniplate; six-hole locking sagittal miniplate. Biomechanical evaluation was performed by applying compression loads to three points on the second molar region, using an Instron universal testing machine until a 3 mm displacement of the segments occurred. Compression loads able to produce 3 mm displacement were recorded in kN and subjected to analysis of variance (P < 0.01) and Tukey's tests for comparison between groups (P < 0.05). The locking sagittal miniplate showed higher resistance to displacement than the regular four- and six-hole locking and standard miniplates. No significant differences were observed between the locking sagittal miniplate and the regular sagittal or the four-hole locking miniplates. Two of the three groups with the best results had locking plate fixation methods. Fixation of SSO with a single miniplate is better accomplished using six-hole locking sagittal miniplates, six-hole standard sagittal miniplates, or four-hole locking miniplates; these methods are more resistant to displacement.     

Does the presence of third molars during sagittal split mandibular ramus osteotomy favour complications? Systematic review and meta-analysis

The aim of this systematic review and meta-analysis was to assess whether the presence of inferior third molars during sagittal split mandibular ramus osteotomy increases the risk of intraoperative and postoperative complications. The PRISMA protocol was followed in this study, and the review was registered in the PROSPERO database (CRD42020147642). A search was conducted in the MEDLINE (PubMed), Web of Science, Cochrane Central, and Scopus databases on November 1, 2021. Nineteen articles were included, and the variables analysed were unfavourable fractures, infection, neurosensory disturbance, removal of osteosynthesis material, and duration of surgery. Meta-analyses were performed for the variables unfavourable fractures (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.58–1.57, P = 0.84), infection (RR 0.75, 95% CI 0.48–1.18, P = 0.21), and neurosensory disturbance (RR 1.55, 95% CI 0.61–3.91, P = 0.35); no statistically significant difference in the risk of these variables was found between the groups with and without third molars. The third molars did not increase the need to remove fixation material, but increased the surgery time. The presence of the third molar during sagittal split mandibular ramus osteotomy appears not to increase the risk of intraoperative and postoperative complications. The results presented here must be interpreted with caution due to the heterogeneity presented by the observational studies included.     

Is short-term neurosensory testing after removal of mandibular third molars efficacious?

Objective. The purpose of this study was the validation of two-point discrimination, Semmes-Weinstein, and pinprick tests of possible sensory disturbance of the inferior alveolar nerve after the surgical removal of lower wisdom teeth.Study design. Forty-two patients who had undergone elective unilateral lower wisdom tooth removal and 30 control subjects were given two-point discrimination, Semmes-Weinstein, and pinprick tests bilaterally in the dermatome of the mental nerve. Test results were compared to the patients' subjective experiences of sensory disturbance. Statistical analysis was done with multivariate analysis of variance.Results. Untreated sides in patients and test sides in control subjects agreed well for all tests. Five of the 42 patients mentioned sensory disturbance, which was confirmed objectively in 3 (by pinprick and two-point discrimination tests). Testing revealed that 16 of the 42 patients had abnormal pinprick and two-point discrimination tests without subjective sensory disturbance. No abnormal values were found for Semmes-Weinstein tests in any of the patients. Multivariate analysis of variance identified a univariately significant effect of the two-point discrimination test (p = 0.027); all other interactions were multivariately insignificant.Conclusion. The value of neurosensory testing after third molar removal is limited because of inconsistency between objective test results and subjective findings.     

Patients' evaluation of the final result of sagittal split osteotomy: is it influenced by impaired sensitivity of the lower lip and chin?

The purpose of this article was to evaluate whether neurosensory disturbances such as impaired sensitivity of the lower lip and chin influence patients' final evaluation of the treatment result. Information about the patients' degree of satisfaction and about lip and chin sensitivity were obtained from final follow-up documents of 215 patients. All patients had undergone sagittal split ramus osteotomy for mandibular advancement. In patients with normal sensitivity on both sides of the lower lip and chin, the degree of satisfaction was equally distributed at a very high level through all age groups. Among those with some degree of numbness on either or both sides of the lower lip and chin, patients in the younger quarter and middle half of the group were as satisfied as those with normal sensitivity, while those in the oldest quarter with impaired sensitivity demonstrated a lower degree of satisfaction than the rest of the patients. Although the difference was not statistically significant, the finding strongly indicates that older patients seem to suffer more from neurosensory disturbances than do younger patients with similar conditions.     

Does oral contraceptive use affect the incidence of complications after extraction of a mandibular third molar?

OBJECTIVE: This study investigated whether oral contraceptive use affects the incidence of complications (pain, trismus, dry socket) in women undergoing removal of impacted mandibular third molars. PATIENTS AND METHOD: Two hundred and sixty seven women, aged 17 - 45 years, underwent removal of an impacted mandibular third molar. Eighty seven of the women were regular users of oral contraceptives. All patients were evaluated for postoperative pain, trismus and dry socket (localized alveolar osteitis). RESULTS: Mean trismus values (measured as maximum interincisal distance) were similar in the two groups of patients. Postoperative pain was significantly more frequent among women taking contraceptives, both on day 1 (30% of women taking contraceptives used analgesics, versus 11% of women not taking contraceptives, p < 0.001) and on day 5 (14% versus 5%, p = 0.024). Similarly, dry socket occurred more frequently among women taking contraceptives than among women not taking contraceptives (11% versus 4%, p = 0.017). CONCLUSIONS: The results of this study support the view that oral contraceptive use favours the appearance of dry socket and postoperative pain after extraction, but has no effect on trismus.     

Effect of self-setting α-tricalcium phosphate between segments for bone healing and hypoaesthesia in lower lip after sagittal split ramus osteotomy

AimsThe aim of this study was to evaluate hypoaesthesia of the lower lip and bone formation using self-setting α-tricalcium phosphate (Biopex^®) between the proximal and distal segments following sagittal split ramus osteotomy (SSRO) with bent absorbable plate fixation.Subjects and methodsThe subjects were 40 patients (80 sides) who underwent bilateral SSRO setback surgery. They were divided into a Biopex^® group (40 sides) and a control group (40 sides). The Biopex^® was inserted into the anterior part of the gap between the segments in the Biopex^® group. Trigeminal nerve hypoaesthesia in the region of the lower lip was assessed bilaterally using the trigeminal somatosensory-evoked potential (TSEP) method. Ramus square, ramus length, and ramus width, the square of the Biopex^® at the horizontal plane under the mandibular foramen were assessed preoperatively, immediately after surgery, and 1 year postoperatively by computed tomography (CT).ResultsThe mean measurable period and standard deviation were 9.3 ± 15.7 weeks in the control group, 5.3 ± 8.3 weeks in the Biopex^® group, and there was no significant difference. Ramus square after 1 year was significantly larger than that prior to surgery and new bone formation was found between the segments in both groups (P < 0.05). In the Biopex^® group, the square of the Biopex^® after 1 year was significantly smaller than that immediately after surgery (P < 0.05).ConclusionThis study suggested that inserting Biopex^® in the gap between the proximal and distal segments was useful for new bone formation and it did not prevent the recovery of lower lip hypoaesthesia after SSRO with bent absorbable plate fixation.     

Do antibiotics reduce the frequency of surgical site infections after impacted mandibular third molar surgery?

Surgical removal of impacted third molars remains the most common procedure performed by oral and maxillofacial surgeons. Given the abundance of host bacteria within the operative sites, surgical site infections are among the most common complications of third molar removal, with an estimated frequency of 1% to 30%. In this setting, significant controversy has surrounded the use of prophylactic antibiotics in the surgical management of impacted third molars. This article provides a comprehensive review of the available data on antibiotic prophylaxis in impacted third molar surgery and offers specific recommendations on antibiotic use.     

Fate of mandibular canals displaced by enlarged cystic lesions: does the inferior alveolar neurovascular bundle relocate to its original position?

Our aim was to identify the positional changes of the inferior alveolar neurovascular bundle and evaluate the relocation of the displaced mandibular canal after enucleation of a cyst. Seventy patients (72 sites) who had had cysts enucleated were divided into three groups based on the degree of encroachment of the cystic lesion into the mandibular canal and whether a bone graft had been inserted after the cyst had been enucleated. The mean (range) of patients’ ages was 45 (18–75) years, and there were 29 male and 41 female patients. Group A comprised cysts with encroachment on the mandibular canal that were enucleated without a bone graft; Group B consisted of cysts with no encroachment of the mandibular canal, but were enucleated without a bone graft; and Group C comprised cysts with encroachment of the mandibular canal that were enucleated with a bone graft. The displacement of the mandibular canal was identified from analysis of computed tomographic (CT) images. Changes in the position of the mandibular canal were measured on panoramic radiographs. The mandibular canal was repositioned superiorly by a mean (SD) of 2.4 (1.65) mm after enucleation of the cyst, which was significant in Group A (p < 0.001), but not in Groups B and C. These results indicate that the displaced inferior alveolar neurovascular bundles that were not surrounded by bony canal tended to relocate towards a supposedly normal position, and after enucleation of the cyst the mandibular canal was remodelled in this new location. This tendency to relocate was blocked by bone grafting. Bone grafts are therefore recommended in cases where enough bony height is required for future insertion of implants.     

Three-dimensional analysis of changes of the malar–midfacial region after LeFort I osteotomy and maxillary advancement

Aim

It has been the objective of the present prospective study to assess visible volume changes of the facial soft tissue after LeFort I osteotomy with advancement and to determine the soft-tissue-to-hard-tissue ratios of advancement.

Patients and methods

Twenty adult patients (ten female, ten male, mean age 33.9?±?14.9 years) received a LeFort I osteotomy with advancement because of a maxillary protrusion. Lateral skull radiographs and optical three-dimensional (3D) scans of the facial surface were assessed preoperatively and 12 months after surgery. The lateral skull radiographs were used to carry out standard linear and angular cephalometric measurements. The pre- and postoperative optical 3D surface scans were registered. A well-defined area in the malar region was used to determine the visible volume changes for each side separately. The mean accommodation vector that transforms the preoperative into the postoperative surface was assessed for each facial half separately. The soft-tissue-to-hard-tissue ratios between the incision superius and the labrale superius, the maximal parasagittal advancement of soft tissue, and the accommodation vectors were calculated.

Results

A mean advancement of the incision superius of 5.3?±?2.1 mm was accompanied by a volume increase of 5.2?±?4.1 cm³ in the right malar–midfacial region and 4.6?±?4.7 cm³ on the left side, respectively, revealing a symmetrical volume change (p?=?0.370). The soft-tissue-to-hard-tissue ratios were 80?±?94% for labrale superius and incision superius, 56?±?79% (right) and 51?±?56% (left) for accommodation vector and incision superius and 97?±?79% (right) and 98?±?89% (left) for maximal parasagittal advancement of soft tissue and incision superius.

Discussion

The determination of volume changes and accompanying accommodation vectors complete the cephalometric analysis during the follow-up of patients undergoing LeFort I osteotomy. The data show that maxillary advancement leads to a more pronounced shifting of the soft tissues in the malar–midfacial area than of the upper lip. The new parameters will help to assess normative soft tissue data based on 3D imaging with a view to an improved three-dimensional prediction of the operative outcome of orthognathic surgery away from the midline.