Reproducibility analysis of automated deep learning based localisation of mandibular canals on a temporal CBCT dataset.

Preoperative radiological identification of mandibular canals is essential for maxillofacial surgery. This study demonstrates the reproducibility of a deep learning system (DLS) by evaluating its localisation performance on 165 heterogeneous cone beam computed tomography (CBCT) scans from 72 patients in comparison to an experienced radiologist's annotations. We evaluated the performance of the DLS using the symmetric mean curve distance (SMCD), the average symmetric surface distance (ASSD), and the Dice similarity coefficient (DSC). The reproducibility of the SMCD was assessed using the within-subject coefficient of repeatability (RC). Three other experts rated the diagnostic validity twice using a 0-4 Likert scale. The reproducibility of the Likert scoring was assessed using the repeatability measure (RM). The RC of SMCD was 0.969 mm, the median (interquartile range) SMCD and ASSD were 0.643 (0.186) mm and 0.351 (0.135) mm, respectively, and the mean (standard deviation) DSC was 0.548 (0.138). The DLS performance was most affected by postoperative changes. The RM of the Likert scoring was 0.923 for the radiologist and 0.877 for the DLS. The mean (standard deviation) Likert score was 3.94 (0.27) for the radiologist and 3.84 (0.65) for the DLS. The DLS demonstrated proficient qualitative and quantitative reproducibility, temporal generalisability, and clinical validity.

Comparison of subjective image analysis and effective dose between low-dose cone-beam computed tomography machines.

OBJECTIVES: To compare the cone-beam computed tomography (CBCT) image quality and effective dose between low-dose scanning and standard manufacturer-recommended protocols among different CBCT units. METHODS: Three human-equivalent phantoms were scanned using the ultra-low-dose (ULD), low dose (LD), and standard dose (STD) modes of ProMax 3D Mid (Planmeca Oy, Helsinki, Finland) and Orthophos SL (Sirona, Bensheim, German) for the CBCT images. The quality of the dental anatomical images was assessed by four experienced oral and maxillofacial radiologists using a 5-point Likert scale. OnDemand3D (Cybermed Co., Seoul, Korea) was used as the third-party software for viewing. The percentage of absolute agreement was calculated to determine intra- and interrater agreements among the observers. The effective doses for all CBCT scanning protocols were also calculated. RESULTS: The STD protocol yielded a higher image quality than did the ULD and LD protocols in both ProMax 3D Mid and Orthophos SL. The ULD and LD protocols demonstrated an "acceptable-to-good" sense of visual perception of the CBCT images. The visibility scores significantly differed between the ULD and LD and the STD protocols in ProMax 3D Mid and Orthophos SL, except for the 120-kVp setting in ProMax 3D Mid. The average intra- and interrater agreement scores ranged from 0.63 to 0.89 and from 0.44 to 0.76, respectively. The ULD and LD protocols reduced the radiation dose sixfold compared with the STD protocol. CONCLUSIONS: High-tube-voltage protocols could remarkably reduce the imaging dose without degrading the image quality. Specifically, ULD and LD CBCT protocols may be adopted as routine practice for diagnosis and treatment planning.

Ultra-low-dose CBCT scan: rational map for ear surgery.

PURPOSE: This study will evaluate the clinical quality and usability of peripheral image data from the temporal bone area obtained using a sinonasal ultra-low-dose (ULD) cone-beam computed tomography (CBCT) scan and compare them to those obtained using a high-resolution (HR) CBCT. METHODS: The population consisted of 66 anatomical sites (ears of 33 subjects) imaged using two modalities: an HR CBCT (Scanora 3Dx scanner; Soredex, Tuusula, Finland) and a ULD CBCT (Promax 3D Mid scanner; Plandent, Helsinki, Finland). The image quality (IQ) for every anatomical site in each image was rated using a Likert scale from 0 to 5. RESULTS: The quality of ULD CBCT scans was clinically sufficient in over 95% of the assessed images of the sigmoid sinus, jugular bulb, epitympanum and mastoid antrum as well as external acoustic meatus (all p > 0.05 compared to HR CBCT). The IQ was clinically sufficient in 75-94% of the assessed images of the scutum, mastoid segment of the facial nerve, cochlea and semicircular canals (all p < 0.05 compared to HR CBCT). The overall IQ of the HR CBCT scans was good or excellent. CONCLUSION: CBCT imaging and the data at image margins are underutilized. CBCT can produce excellent structural resolution with conventional imaging parameters, even with off-focus images. Using ultra-low doses of radiation, the produced IQ is clinically sufficient. We encourage ear surgeons to check the patients' imaging history and to consider the use of imaging modalities that involve lower radiation doses especially when conducting repetitive investigations and with children.

MRI of odontogenic maxillofacial infections: diagnostic accuracy and reliability.

OBJECTIVES: To determine the diagnostic accuracy of emergency magnetic resonance imaging (MRI) in odontogenic maxillofacial infections, the clinical and surgical significance of MRI findings, and whether MRI can identify the tooth responsible for the infection. METHODS: A retrospective cohort study reviewed 106 emergency neck MRI scans of patients with neck infections of odontogenic origin. The diagnostic accuracy of MRI in identifying abscesses was studied relative to surgical findings. Correlations were analyzed between various MRI findings and clinical results and outcomes, such as the surgical approach (intraoral vs. extraoral). The ability of MRI findings to predict the causative tooth was assessed in a blinded multi-reader setting. RESULTS: Of the 106 patients with odontogenic infections, 77 (73%) had one or more abscesses. Imaging showed a sensitivity, specificity, and accuracy of 0.95, 0.84, and 0.92, respectively, for MRI diagnosis of an odontogenic abscess. Among the imaging findings, mediastinal edema was the strongest predictor of extraoral surgery. MRI showed bone marrow edema in the majority of patients, and multi-reader assessment showed good reliability. MRI was also able to predict the causative tooth accurately. CONCLUSIONS: Emergency neck MRI can accurately detect odontogenic abscesses and reliably point to the causative tooth. These results can increase the utility and reliance on emergency MRI in clinical decision-making.

Comparison of deep learning segmentation and multigrader-annotated mandibular canals of multicenter CBCT scans.

Deep learning approach has been demonstrated to automatically segment the bilateral mandibular canals from CBCT scans, yet systematic studies of its clinical and technical validation are scarce. To validate the mandibular canal localization accuracy of a deep learning system (DLS) we trained it with 982 CBCT scans and evaluated using 150 scans of five scanners from clinical workflow patients of European and Southeast Asian Institutes, annotated by four radiologists. The interobserver variability was compared to the variability between the DLS and the radiologists. In addition, the generalisation of DLS to CBCT scans from scanners not used in the training data was examined to evaluate its out-of-distribution performance. The DLS had a statistically significant difference (p < 0.001) with lower variability to the radiologists with 0.74 mm than the interobserver variability of 0.77 mm and generalised to new devices with 0.63 mm, 0.67 mm and 0.87 mm (p < 0.001). For the radiologists' consensus segmentation, used as a gold standard, the DLS showed a symmetric mean curve distance of 0.39 mm, which was statistically significantly different (p < 0.001) compared to those of the individual radiologists with values of 0.62 mm, 0.55 mm, 0.47 mm, and 0.42 mm. These results show promise towards integration of DLS into clinical workflow to reduce time-consuming and labour-intensive manual tasks in implantology.

Evaluation of voice commands for mode change in virtual reality implant planning procedure.

PURPOSE: In dental implantology, the optimal placement of dental implants is important to meet functional and aesthetic requirements. Planning dental implants in virtual three-dimensional (3D) environment is possible using virtual reality (VR) technologies. The three-dimensional stereoscopic virtual reality environment offers advantages over three-dimensional projection on a two-dimensional display. The use of voice commands in virtual reality environment to replace button presses and other simple actions frees the user's hands and eyes for other tasks. METHODS: Six dentomaxillofacial radiologists experimented using a prototype version of a three-dimensional virtual reality implant planning tool, and used two different tool selection methods, using either only button presses or also voice commands. We collected objective measurements of the results and subjective data of the participant experience to compare the two conditions. RESULTS: The tool was approved by the experts and they were able to do the multiple-implant planning satisfactorily. The radiologists liked the possibility to use the voice commands. Most of the radiologists were willing to use the tool as part of their daily work routines. CONCLUSION: The voice commands were useful, natural, and accurate for mode change, and they could be expanded to other tasks. Button presses and the voice commands should be both available and used in parallel. The input methods can be further improved based on the expert comments.

Evaluation of virtual handles for dental implant manipulation in virtual reality implant planning procedure.

PURPOSE: Many surgical complications can be prevented by careful operation planning and preoperative evaluation of the anatomical features. Virtual dental implant planning in three-dimensional stereoscopic virtual reality environment has advantages over three-dimensional projections on two-dimensional screens. In the virtual environment, the anatomical areas of the body can be assessed and interacted with in six degrees-of-freedom. Our aim was to make a preliminary evaluation of how professional users perceive the use of the virtual environment on their field. METHODS: We prepared a novel implementation of a virtual dental implant planning system and conducted a small-scale user study with four dentomaxillofacial radiologists to evaluate the usability of direct and indirect interaction in a planning task. RESULTS: We found that all four participants ranked direct interaction, planning the implant placement without handles, to be better than the indirect condition where the implant model had handles. CONCLUSION: The radiologists valued the three-dimensional environment for three-dimensional object manipulation even if usability issues of the handles affected the feel of use and the evaluation results. Direct interaction was seen as easy, accurate, and natural.

Association between Oral Pathology, Carotid Stenosis, and Oral Bacterial DNA in Cerebral Thrombi of Patients with Stroke.

METHODS: Thrombus aspirates and control arterial blood were taken from 71 patients (70.4% male; mean age, 67.4 years) with acute ischemic stroke. Tooth pathology was registered using CT scans. Carotid stenosis was estimated with CTA and ultrasonography. The presence of bacterial DNA from aspirated thrombi was determined using quantitative PCR. We also analyzed the presence of these bacterial DNAs in carotid endarterectomies from patients with peripheral arterial disease. RESULTS: Bacterial DNA was found in 59 (83.1%) of the thrombus aspirates (median, 8.6-fold). Oral streptococcal DNA was found in 56 (78.9%) of the thrombus aspirates (median, 5.1-fold). DNA from A. actinomycetemcomitans and P. gingivalis was not found. Most patients suffered from poor oral health and had in median 19.0 teeth left. Paradoxically, patients with better oral health had more oral streptococcal DNA in their thrombus than the group with the worst pathology (p = 0.028). There was a trend (OR 7.122; p = 0.083) in the association of ≥50% carotid artery stenosis with more severe dental pathology. Oral streptococcal DNA was detected in 2/6 of carotid endarterectomies. CONCLUSIONS: Stroke patients had poor oral health which tended to associate with their carotid artery stenosis. Although oral streptococcal DNA was found in thrombus aspirates and carotid endarterectomy samples, the amount of oral streptococcal DNA in thrombus aspirates was the lowest among those with the most severe oral pathology. These results suggest that the association between poor oral health and acute ischemic stroke is linked to carotid artery atherosclerosis.

Assessment of PIV performance in validating CFD models from nasal cavity CBCT scans.

OBJECTIVE: The aim of our study was to investigate how well Particle Image Velocimetry (PIV) measurements could serve Computational Fluid Dynamics (CFD) model validation for nasal airflow. MATERIAL AND METHODS: For the PIV measurements, a silicone model of the nose based on cone beam computed tomography (CBCT) scans of a patient was made. Corresponding CFD calculations were conducted with laminar and two turbulent models (k-ω and k-ω SST). RESULTS: CFD and PIV results corresponded well in our study. Especially, the correspondence of CFD calculations between the laminar and turbulent models was found to be even stronger. When comparing CFD with PIV, we found that the results were most convergent in the wider parts of the nasal cavities. CONCLUSION: PIV measurements in realistically modelled nasal cavities succeed acceptably and CFD calculations produce corresponding results with PIV measurements. Greater model scaling is, however, necessary for better validations with PIV and comparisons of competing CFD models.

Deep Learning Method for Mandibular Canal Segmentation in Dental Cone Beam Computed Tomography Volumes.

Accurate localisation of mandibular canals in lower jaws is important in dental implantology, in which the implant position and dimensions are currently determined manually from 3D CT images by medical experts to avoid damaging the mandibular nerve inside the canal. Here we present a deep learning system for automatic localisation of the mandibular canals by applying a fully convolutional neural network segmentation on clinically diverse dataset of 637 cone beam CT volumes, with mandibular canals being coarsely annotated by radiologists, and using a dataset of 15 volumes with accurate voxel-level mandibular canal annotations for model evaluation. We show that our deep learning model, trained on the coarsely annotated volumes, localises mandibular canals of the voxel-level annotated set, highly accurately with the mean curve distance and average symmetric surface distance being 0.56 mm and 0.45 mm, respectively. These unparalleled accurate results highlight that deep learning integrated into dental implantology workflow could significantly reduce manual labour in mandibular canal annotations.

Three-Dimensional Printing of the Nasal Cavities for Clinical Experiments.

3D printing has produced many beneficial applications for surgery. The technique´s applicability in replicating nasal cavity anatomy for clinical use has not been studied. Our aim was to determine whether 3D printing could realistically replicate the nasal cavities and the airflow passing through them from a clinical point of view. We included Cone Beam Computed Tomography (CBCT) scans of five patients with symptoms of chronic nasal congestion. These CBCT scans were used to print plastic 3D prints of the nasal cavities, which were also CBCT scanned and the measurements were compared. The results in vivo were higher than the results in vitro in maxillary sinus volumes with a ratio of 1.05 ± 0.01 (mean ± SD) and in the nasal cavities with a ratio of 1.20 ± 0.1 (mean ± SD). Linear measurements in vitro were very close to those in vivo. Rhinomanometric results showed some differences, but rhinomanometric graphs in vitro were close to the graphs in vivo. 3D printing proved to be a suitable and fast method for replicating nasal cavity structures and for the experimental testing of nasal function. It can be used as a complementary examination tool for rhinomanometry.

Effect of Maxillomandibular Advancement Surgery on Pharyngeal Airway Volume and Polysomnography Data in Obstructive Sleep Apnea Patients.

PURPOSE: To study volumetric changes in the upper airway in patients with obstructive sleep apnea (OSA) after maxillomandibular advancement (MMA) and compare those findings with polysomnographic (PSG) data of the same patients. MATERIALS AND METHODS: The study included 20 patients with OSA (1 woman and 19 men; mean age, 48 yr; range, 31 to 59 yr). Mean values of angles formed by the sella, nasion, and B point and the sella, nasion, and A point before surgery indicated mandibular and maxillary retrognathia, respectively. All patients were treated with MMA and pre- and postoperative orthodontics. Pre- and post-treatment cone-beam computed tomograms were used to measure upper airway volume and PSG data were used to examine the apnea-hypopnea index (AHI) and oxygen desaturation index (ODI-3 or ODI-4). In addition, Epworth Sleepiness Scale (ESS) score, General Health Questionnaire (GHQ-12) score, and amount of MMA were collected from patients' files. RESULTS: Mean maxillary and mandibular advancement was 4.6 ± 1.9 and 9.3 ± 1.7 mm, respectively. A statistically relevant increase (mean, 64.1%) in airway volume was found, with large individual variation. ODI-3 or ODI-4 and AHI values showed statistically relevant improvements from before to after surgery. ODI-3 or ODI-4 score decreased from 12.3 ± 9.8 to 4.0 ± 4.2 and AHI score decreased from 21.4 ± 13.8 to 5.8 ± 7.2. ESS scores showed improvement (lower scores) after surgery for most patients (n = 15), whereas GHQ-12 scores showed improvement (lower scores) for only 6 patients. CONCLUSION: MMA increases upper airway volume and lessens OSA symptoms according to PSG data. MMA can be considered curative treatment for OSA; however, residual apnea as measured by the AHI can be found in many patients.

Diagnosis of Newly Delivered Mothers for Periodontitis with a Novel Oral-Rinse aMMP-8 Point-of-Care Test in a Rural Malawian Population.

A novel qualitative point-of-care test of activated matrix metalloproteinase-8 (aMMP-8) using noninvasive oral rinse sampling procedures has been developed for the early detection of collagen breakdown indicating periodontal tissue destruction. The main object of this study was to assess the reliability of the test in a low-income setting to identify participants with history of periodontal destruction detected as alveolar bone loss (ABL) in radiographs. This cross-sectional study included 486 women who had recently delivered in rural Malawi. The aMMP-8 test and dental panoramic radiographs were taken within 48 h of delivery. The performance of the test in comparison to radiological examinations was tested by following the standards for reporting of diagnostic accuracy studies protocol (STARD) with respective statistical measures and 95% confidence intervals. From the 486 eligible participants, 461 mothers with complete data, aged from 15 to 46 years (mean 24.8, SD 6.0) were included in the analysis. ABL was identified in 116 of 461 participants. There was 56% agreement between the aMMP-8 test results and detected ABL (yes or no) in radiographs. Calculated sensitivity of the test was 80% (72⁻87%), specificity 48% (43⁻54%), positive predictive value 34% (31⁻37%), negative predictive value 88% (83⁻91%), positive likelihood ratio 1.55 (1.35⁻1.77), and negative likelihood ratio 0.41(0.28⁻0.60). The aMMP-8 test sensitivity and negative predictive value to identify the ABL cases were relatively high, but there was additionally a high rate of test-positive results in participants without ABL, especially in young mothers, leading to low overall agreement between the test results and radiological bone loss. Further longitudinal studies are needed to examine if the test positive subjects are in risk of future bone loss before the detectable signs of periodontitis in radiographs.

The dental infections in patients undergoing preoperative dental examination before surgical treatment of saccular intracranial aneurysm.

OBJECTIVE: Dental bacterial DNA and bacterial-driven inflammation markers have previously been detected in intracranial aneurysm tissue samples. This study aimed (i) to assess the possible presence of dental infectious foci, (ii) and the possible association between typical odontogenic bacteria and clinical dental findings in patients undergoing pre-operative dental examination before surgical treatment of saccular intracranial aneurysm. Ninety patients with an intracranial aneurysm were recruited to the study, and the patients' teeth were routinely investigated. Clinical data and bacterial samples from the gingival pockets were collected from a subpopulation of 60 patients. Five typical dental pathogens and total bacteria amounts were measured from gingival samples using real-time quantitative PCR. RESULTS: The amounts of total bacterial and Fusobacterium nucleatum DNA were significantly higher in the patients with ≥ 6 mm gingival pockets than patients without them (p < 0.01 and p < 0.01, respectively). A total of 43% of patients with an aneurysm had gingival pockets of 6 mm or deeper. Dental infectious foci are fairly common in the Finnish population, with the prevalence of severe periodontitis being around 20%. The frequency of chronic dental infections, especially periodontitis seems to be higher in patients with intracranial aneurysm.

Impact of prone, supine and oblique patient positioning on CBCT image quality, contrast-to-noise ratio and figure of merit value in the maxillofacial region.

OBJECTIVES: To assess the impact of supine, prone and oblique patient imaging positions on the image quality, contrast-to-noise ratio (CNR) and figure of merit (FOM) value in the maxillofacial region using a CBCT scanner. Furthermore, the CBCT supine images were compared with supine multislice CT (MSCT) images. METHODS: One fresh frozen cadaver head was scanned in prone, supine and oblique imaging positions using a mobile CBCT scanner. MSCT images of the head were acquired in a supine position. Two radiologists graded the CBCT and MSCT images at ten different anatomical sites according to their image quality using a six-point scale. The CNR and FOM values were calculated at two different anatomical sites on the CBCT and MSCT images. RESULTS: The best image quality was achieved in the prone imaging position for sinus, mandible and maxilla, followed by the supine and oblique imaging positions. 12-mA prone images presented high delineation scores for all anatomical landmarks, except for the ear region (carotid canal), which presented adequate to poor delineation scores for all studied head positions and exposure parameters. The MSCT scanner offered similar image qualities to the 7.5-mA supine images acquired using the mobile CBCT scanner. The prone imaging position offered the best CNR and FOM values on the mobile CBCT scanner. CONCLUSIONS: Head positioning has an impact on CBCT image quality. The best CBCT image quality can be achieved using the prone and supine imaging positions. The oblique imaging position offers inadequate image quality except in the sinus region.

Critical distance between the cartilaginous Eustachian tube and the internal carotid artery.

During the last decade, endoscopic surgery of the Eustachian tube (ET) has been advocated for ET dilatory dysfunction and for patulous ET. The internal carotid artery (ICA) and the ET are closely related, and knowledge of their surgical anatomy has become essential. This study was designed to establish the anatomical relationships between the endoscopically critical area along the full length of the cartilaginous ET and its closest association with the ICA. The perpendicular distance between the ET lumen and the ICA was measured from head magnetic resonance images (MRI) at three levels: (A) cartilaginous and bony ET junctional point, (B) mid cartilaginous ET point, and (C) the nasopharyngeal orifice of the cartilaginous ET. Totally, 200 sides were reviewed in MRI scans of 229 patients. The mean distances for each level were: A = 4.3 mm (range 1.6-10.4 mm), B = 25 mm (range 9.0-61.6 mm), and C = 62 mm (range 34.3-84.4 mm). The perpendicular distance between ET and ICA at the nasopharyngeal orifice is large, but the distance shortens quickly while moving from the nasopharyngeal orifice of the ET to the junctional point of the ET. The potential for complications to the ICA rises as the surgical field moves closer to the isthmus of the ET because of the decreasing distance between the ET and the ICA.

Nutrient supplementation may adversely affect maternal oral health--a randomised controlled trial in rural Malawi.

Nutritional supplementation during pregnancy is increasingly recommended especially in low-resource settings, but its oral health impacts have not been studied. Our aim was to examine whether supplementation with multiple micronutrients (MMN) or small-quantity lipid-based nutrient supplements affects dental caries development or periodontal health in a rural Malawian population. The study was embedded in a controlled iLiNS-DYAD trial that enrolled 1391 pregnant women <20 gestation weeks. Women were provided with one daily iron-folic acid capsule (IFA), one capsule with 18 micronutrients (MMN) or one sachet of lipid-based nutrient supplements (LNS) containing protein, carbohydrates, essential fatty acids and 21 micronutrients. Oral examination of 1024 participants was conducted and panoramic X-ray taken within 6 weeks after delivery. The supplement groups were similar at baseline in average socio-economic, nutritional and health status. At the end of the intervention, the prevalence of caries was 56.7%, 69.1% and 63.3% (P = 0.004), and periodontitis 34.9%, 29.8% and 31.2% (P = 0.338) in the IFA, MMN and LNS groups, respectively. Compared with the IFA group, women in the MMN group had 0.60 (0.18-1.02) and in the LNS group 0.59 (0.17-1.01) higher mean number of caries lesions. In the absence of baseline oral health data, firm conclusions on causality cannot be drawn. However, although not confirmatory, the findings are consistent with a possibility that provision of MMN or LNS may have increased the caries incidence in this target population. Because of the potential public health impacts, further research on the association between gestational nutrient interventions and oral health in low-income settings is needed.

Association between maternal dental periapical infections and pregnancy outcomes: results from a cross-sectional study in Malawi.

OBJECTIVES: Maternal infections are associated with intrauterine growth restriction (IUGR) and preterm birth (PTB). Dental infections are common in low-income settings, but their contribution to adverse pregnancy outcomes is unknown. We studied the epidemiology of dental periapical infections among pregnant women and their association to foetal growth restriction and the duration of pregnancy in a rural sub-Saharan African population. METHODS: This was a cross-sectional study on the association between maternal dental periapical infections and birth outcomes, in Malawi, Africa. We assessed oral health clinically and radiologically among recently delivered women with known duration of pregnancy and measured birthweight (BW), length and head circumference of their infants. RESULTS: Of 1024 analysed participants, 23.5% had periapical infections. Mean duration of pregnancy was 39.4 weeks, BW 2979 g and length 49.7 cm. Women with periapical infection had mean (95% CI) pregnancy duration 0.4 weeks (0.1-0.8) shorter and delivered infants with 79 g (13-145) lower BW and 0.5 cm (0.2-0.9) shorter neonatal length than women without periapical infection. The incidence of PTB was 10.0% among women with periapical infection and 7.3% among those without (adjusted difference 3.5%, 95% CI -1.1-8.1%). Corresponding prevalences for stunting were 20.9% and 14.2% (adjusted difference 9.0%, 95% CI 2.7%-15.2%). The population-attributable risk fraction attributable to periapical infection was 9.7% for PTB and 12.8% for stunting. CONCLUSIONS: Periapical infection was associated with shorter pregnancy duration and IUGR in the study area; interventions addressing this risk factor may improve birth outcomes in low-income settings.