3.0 Tesla MRI in the early evaluation of inferior alveolar nerve neurological complications after mandibular third molar extraction: a prospective study

Visualization of the Inferior Alveolar Nerve and Lingual Nerve Using MRI in Oral and Maxillofacial Surgery: A Systematic Review

We evaluate the preoperative visualization of the inferior alveolar nerve (IAN) and lingual nerve (LN) as reported using radiation-free magnetic resonance imaging (MRI). An accurate visualization shall minimize the postoperative risk for nerve injuries in oral and maxillofacial surgery. PubMed MEDLINE, EMBASE, Biosis, and Cochrane databases were selected for the PICOS search strategy by two reviewers using medical subject headings (MeSH) terms. Thirty studies were included in the systematic review. Based on these studies’ findings, the use of black bone MRI sequences, especially 3D short-tau inversion recovery (STIR), provides superior soft-tissue resolution and high sensitivity in detecting pathological changes. Due to the implementation variability regarding scan parameters and the use of different magnetic field strengths, studies with well-designed protocols and a low risk of bias should be conducted to obtain stronger evidence. With improved cost and time efficiency and considering the benefit–risk ratio, MRI is a promising imaging modality that could become part of routine clinical practice in the future.

Pathologies associated with the mandibular third molar impaction

To evaluate the associations of impaction patterns of mandibular third molars (M3Ms) with pathologies caused by them. In this study, 262 patients with 432 impacted M3Ms who referred in Shanghai Xuhui District Center were reviewed. The pathologies include pericoronitis, mandibular second molar (M2M) caries, and M2M distal periodontal pathology. The impaction patterns of M3Ms and the pathologies were examined, while the M2M outcomes after surgeries were evaluated. A χ2 test was used to analyze the data, with a p value of <0.05 being considered statistically significant. Pericoronitis was the major symptom in all patients, whereas the propensities of M2M distal caries and periodontal pathologies increased in older patients. Soft tissue impacted and vertically angulated teeth were more associated with pericoronitis (p < 0.05); mesio-angular impacted teeth in less deep positions had greater risks of M2Ms distal caries (p < 0.05); mesio-angular and horizontal impacted teeth in relative deep positions were more likely to cause M2Ms distal periodontal pathologies (p < 0.05). Extractions of soft tissue impacted teeth in vertical angulations should be considered, while removals of mesially and horizontally angulated or bony impacted teeth could be delayed.

A systematic review on diagnostic test accuracy of magnetic resonance neurography versus clinical neurosensory assessment for post-traumatic trigeminal neuropathy in patients reporting neurosensory disturbance

OBJECTIVES

To perform a systematic review of published studies on diagnostic accuracy of magnetic resonance neurography (MRN) vs clinical neurosensory testing (NST) for post-traumatic trigeminal neuropathy (PTTN) in patients reporting neurosensory disturbances (NSD).

METHODS

Human studies except case reports, reviews, systematic reviews and meta-analyses were included. PubMed, Embase, Web of Science and Cochrane Library were consulted. Risk of bias assessment was conducted using the Quality Assessment of Diagnostic Accuracy Studies 2 tool. Predetermined data extraction parameters were noted and summarized.

RESULTS

8 studies met eligibility criteria of which 7 were retrospective, representing 444 subjects. Most studies were at high risk of bias with low applicability concerns. Populations and objectives were divergent with a large variation in timing (3 days-17 years post injury) and parameters (multiple coil designs, fat suppression techniques, additional contrast agent) of MRI acquisition. T₂ weighted 3 T imaging with short echo times (2.2-100 ms) and fat suppression was applied in seven studies, techniques varied. Determination of sensitivity and specificity could not be performed due to the methodological variation between studies and lacking comparative data between index and reference tests. Based on limited data, PTTN correlated reasonably well between clinical assessment, intraoperative findings and MRN abnormalities (k = 0.57). Increased signal intensity correlated with persistency of neurosensory disturbances in one study. Intra- (ICC 0.914-0.927) and interobserver (k = 0.70-0.891) MRN variability was considered good to excellent. One retrospective study showed substantial impact of MRN on clinical decision making in one-third of patients.

CONCLUSION

Currently, there is insufficient scientific knowledge to support or refute the use of MRN. Based on limited data, MRN seems promising and reliable in detection and grading of PTTN. Methodological issues underline the importance for prospective blinded studies with standardization of signal intensity calculation and rigorous reporting of MRI acquisition parameters.

Assessment of impacted and partially impacted lower third molars with panoramic radiography compared to MRI-a proof of principle study

OBJECTIVES

Third molars often require surgical removal. Since three-dimensional radiological assessment is often indicated in difficult cases to avoid surgical complications, the radiation burden has to be considered. Here, MRI may offer a dose-free alternative to conventional X-ray techniques. The aim of this retrospective analysis was to evaluate the assessment quality of MRI compared to panoramic radiography in impacted and partially impacted lower third molars.

METHODS

Panoramic radiographs and MRI scans of 28 Caucasian patients were assessed twice by four investigators. Wisdom teeth were classified according to Juodzbalys and Daugela 2013.

RESULTS

When radiological lower third molar assessments with panoramic radiography and MRI were compared, staging concurred in 73% in the first round of assessments and 77% in the second.

CONCLUSIONS

The presented study demonstrates that MRI not only provides much the same information that panoramic radiography usually does, but also has the advantages of a dose-free three-dimensional view. This may facilitate and shorten third molar surgery. Image interpretation, however, can differ depending on training and experience.

The effects of a common stainless steel orthodontic bracket on the diagnostic quality of cranial and cervical 3T- MR images: a prospective, case-control study

OBJECTIVES

To evaluate the effect of orthodontic stainless steel brackets and two different types of archwires on the diagnostic quality of 3-T MR images.

METHODS

This prospective, case-control study was conducted following Strengthening the Reporting of Observational Studies in Epidemiology guidelines. The recruitment was conducted among orthodontic patients. 80 subjects, requiring MRI for the presence of temporomandibular disorders, were enrolled and divided into four groups: 20 patients using aligners (control group); 20 patients with stainless steel brackets without archwires; 20 patients with stainless steel brackets and nickel-titanium archwires; and 20 patients with stainless steel brackets and stainless steel archwires. Two experts in neuroradiology evaluated the images to determine the amount of distortion in 6 regions and 48 districts. A score was subjectively assigned according to a modified receiver operating characteristic method of distortion classification. Any disagreement was resolved through consensus seeking; when this was not possible, a third neuroradiologist was consulted. The following statistical methods were used: descriptive statistics, Cohen's kappa coefficient (k), Kruskal-Wallis test, pairwise comparisons using the Dunn-Bonferroni approach. The significance was set at p ≤ 0.05.

RESULTS

The presence of stainless steel brackets with or without archwires negatively influenced MRI of the cervical region, paranasal sinuses, head and neck region, and cervical vertebrae but did not influence MRI of brain and temporomandibular joint regions.

CONCLUSIONS

Patients with a stainless steel multibracket orthodontic appliance should remove it before cervical vertebrae, cervical region, paranasal sinuses, and head and neck MRI scans. The brain and temporomandibular joint region MRI should not require the removal of such appliances.

Diffusion tensor imaging of the inferior alveolar nerve using 3T MRI: a study for quantitative evaluation and fibre tracking

OBJECTIVES

Diffusion tensor imaging (DTI) can provide structural information and objective values for nerves. The aims of this study were to perform quantitative evaluation and fibre tracking of the normal inferior alveolar nerve (IAN) using DTI on 3.0-T MRI.

METHODS

DTI was applied to 92 IANs of 46 healthy volunteers. Circular regions of interest (ROIs) were placed on three different positions at the mandibular foramen, second molar and mental foramen of each nerve on apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps, and the ADC and FA of each ROI were measured. Differences in the values arising from the nerve positions were evaluated. Furthermore, fibre tracking of the IANs was performed by tractography, and the quality of visualization was evaluated.

RESULTS

There were no significant differences in the ADC and FA between the right and left sides regardless of the anteroposterior positions. Regarding differences arising from the anteroposterior measurement positions, the ADC and FA showed no significant differences (p > 0.017), except for the ADCs between the positions at the mandibular foramen and mental foramen in the left side (p = 0.0068). Overall, 70 (76%) of the 92 IANs could be visualized fully or partially by tractography.

CONCLUSIONS

The ADC and FA of the IAN were successfully obtained from healthy volunteers using DTI and were confirmed to be symmetrical regardless of the measurement positions. DTI is a feasible technique for the quantitative evaluation and visualization of the IAN.

Visualization techniques of the inferior alveolar nerve (IAN): a narrative review

Purpose

The purpose of this study was to produce an overview of the present visualization techniques of the inferior alveolar nerve (IAN) in order to reduce the rates of nerve damage after third molar (M3) removal and bilateral sagittal split osteotomy (BSSO).

Methods

An electronic literature search was performed of the English-language scientific literature published prior to December 31, 2014 using the LIMO KU Leuven search platform. Information on the specifications of the different imaging techniques, their clinical application, advantages, disadvantages, and duration was extracted from 11 reports.

Results

Five methods for IAN visualization were obtained from the search results, which are cone-beam computed tomography (CBCT) and automatic extraction of the IAN canal using computed tomography (CT), magnetic resonance imaging (MRI), panoramic radiography, endoscopy, and ultrasonographic visualization.

Conclusion

The results of this study suggest that high-resolution MRI is the most commonly used method for direct visualization of the IAN. Six out of the eleven manuscripts use this technique. Recently, there have been some (experimental) modifications to the conventional MRI in the form of diffusion tensor tractography (DTT), phase-contrast magnetic resonance angiography (PC-MRA), and dental MRI. Future studies will focus on an intraoperative application of MRI to visualize the IAN during surgery.