Contrast-enhanced computed tomography of retromandibular vein position and course patterns relative to the mandible during sagittal split ramus osteotomy.

Background: Sagittal split ramus osteotomy is an established procedure used in oral and maxillofacial surgery. Major bleeding is representative intraoperative complication involves vessels such as the inferior alveolar, facial, and maxillary arteries and accompanying veins, in particular the retromandibular vein (RMV). We previously described the RMV course patterns using embalmed cadavers. However, owing to the possible influence of formalin fixation and unclear skeletal classification of the jaws, the present study aimed to use contrast-enhanced computed tomography to confirm the RMV in patients with defined jaw deformities. Methods: Twenty patients with orthognathic jaw deformities (40 sides) were included. The RMV and the lateral and posterior views of the mandible were evaluated using contrast-enhanced computed tomography. Course patterns and RMV positions were classified as previously reported. Results: Three patterns were identified in the lateral view. Type A: RMV posterior to the posterior border of the ramus (n=25; 62.5%). Type B: adjoining the posterior border of the ramus (n=12; 30.0%). Type C: anterior to the posterior border of the ramus (n=3; 7.5%). Five course patterns were identified in the posterior view. Pattern I: rectilinear course running medial to the posterior border of the ramus (n=3; 7.5%). Pattern II: diagonal course running medially from immediately posterior to posterior border of the ramus (n=11; 27.5%). Pattern III: rectilinear course running immediately posterior to the posterior border of the ramus (n=12; 30.0%). Pattern IV: diagonal course running from lateral to medial relative to the posterior border of the ramus (n=8; 20.0%). Pattern V: diagonal course running from lateral to immediately posterior relative to the posterior border of the ramus (n=6; 15.0%). In the no-course pattern group, the RMV inferior to the lingula was lateral to its position and superior to that of the lingula. In half of the cases, the left and right sides exhibited different running patterns. We observed no correlation between the skeletal patterns of jaw deformities and the course of the RMV. Conclusions: Type B/Pattern II that runs in a straight line bordering the posterior margin of the ramus requires the most attention during surgery. These findings suggest the possibility of predicting intraoperative bleeding risk.

Enhanced Precision in Genioplasty: A Novel Intraoperative Spatial Repositioning Using Computer-Aided Design and Manufacturing Technology and a Holographic Mixed Reality Application.

Genioplasty is performed for the orthognathic surgical correction of dentofacial deformities. This article reports a safe and accurate method for genioplasty combining a novel three-dimensional (3D) device with mixed reality (MR)-assisted surgery using a registration marker and a head-mounted display. Four types of devices were designed based on the virtual operation: a surgical splint with a connector; an osteotomy device; a repositioning device; and a registration marker. Microsoft HoloLens 2 and Holoeyes MD were used to project holograms created using computed tomography (CT) data onto the surgical field to improve the accuracy of the computer-aided designed and manufactured (CAD/CAM) surgical guides. After making an incision on the oral vestibule, the splint was fitted on the teeth and the osteotomy device was mounted at the junction site, placed directly on the exposed mandible bone surface. Temporary screws were fixed into the screw hole. An ultrasonic cutting instrument was used for the osteotomy. After separating the bone, a repositioning device was connected to the splint junction and bone segment, and repositioning was performed. At the time of repositioning, the registration marker was connected to the splint junction, and mandible repositioning was confirmed three-dimensionally through HoloLens 2 into the position specified in the virtual surgery. The rate of overlay error between the preoperative virtual operation and one-month postoperative CT data within 2 mm was 100%. CAD/CAM combined with MR enabled accurate genioplasty.

Cephalometric landmark detection without X-rays combining coordinate regression and heatmap regression.

Fully automated techniques using convolutional neural networks for cephalometric landmark detection have recently advanced. However, all existing studies have adopted X-rays. The problem of direct exposure of patients to X-ray radiation remains unsolved. We propose a model for detecting cephalometric landmarks using only facial profile images without X-rays. First, the model estimates the landmark coordinates using the features of facial profile images through high-resolution representation learning. Second, considering the spatial relationship of the landmarks, the model refines the estimated coordinates. The estimated coordinates are input into fully connected networks to improve the accuracy. During the experiment, a total of 2000 facial profile images collected from 2000 female patients were used. Experiments results suggested that the proposed method may perform at a level equal to or potentially better than existing methods using cephalograms. We obtained an MRE of 0.61 mm for the test data and a mean detection rate of 98.20% within 2 mm. Our proposed two-stage learning method enables a highly accurate estimation of the landmark positions using only facial profile images. The results indicate that X-rays may not be required when detecting cephalometric landmarks.

Three-dimensional Maxillofacial Morphology Measurements in Japanese Adults with Normal Occlusion.

Accurate orthodontic analysis and diagnosis based on anatomical landmarks is essential to the success of orthodontic treatment. Helical computed tomography (CT) has evolved markedly, and dentists can now quickly obtain 3-dimensional (3D) reconstruction data using this imaging modality. The planning of orthodontic treatment had traditionally been based on cephalometric analysis using 2D landmarks. This study aimed to collect 3D morphological data using CT images to establish new landmarks for analysis and diagnosis in orthodontic treatment. Twenty male and 20 female adult Japanese dry skulls with of normal occlusion were selected. The skulls were scanned using a multidetector helical CT system (SIEMENS, Volume Zoom Plus 4, Germany). Models were reconstructed using 3D measurement software (Simplant, Dentsply Sirona, Tokyo, Japan) and 45 landmarks determined. Three-dimensional measurement for a total of 30 items representing these landmarks was then performed. The results provided 3D standard values for maxillofacial morphology in adult Japanese individuals with normal occlusion. These measurement items should allow the disadvantages of 2D cephalometric analysis to be overcome.

Mechanical stress-induced FGF-2 promotes proliferation and consequently induces osteoblast differentiation in mesenchymal stem cells.

Mechanical stimuli serve as crucial regulators of bone mass, promoting bone formation. However, the molecular mechanisms governing how mesenchymal stem cells (MSCs) respond to mechanical cues during their differentiation into osteogenic cells remain elusive. In this study, we found that cyclic stretching enhances MSC proliferation but does not increase the expression of osteoblast-related genes. We further revealed that this proliferative effect is mediated by fibroblast growth factor 2 (FGF-2), synthesized by MSCs in response to mechanical stress. Cell proliferation induced by cyclic stretching was inhibited upon the addition of either U0126, an inhibitor of mitogen-activated protein kinase kinase (MEK), or early growth response 1 (EGR1)-targeting small-hairpin RNA (shRNA), indicating the involvement of the extracellular signal-regulated kinase (ERK)/EGR1 signaling pathway. Osteoblast differentiation, evaluated through ALP activity, osteoblast-related gene expression, and mineralization, was stimulated by recombinant human FGF-2 (rhFGF-2) when applied during the proliferation phase, but not when applied during the differentiation stage alone. Our results suggest that FGF-2 indirectly promotes osteoblast differentiation as a downstream effect of stimulating cell proliferation. For the first time, we demonstrate that cyclic stretching induces MSCs to produce FGF-2, which in turn encourages cell proliferation through an autocrine/paracrine mechanism, consequently leading to osteoblast differentiation.

Characteristics of Mandibular Arch Forms in Patients with Skeletal Mandibular Prognathism.

Arch forms in orthodontics are considered to affect occlusal stability. This study's subjects were 47 patients (Class III S group) who visited the Chiba Dental Center of Tokyo Dental College and were surgical orthodontic cases, and 60 patients with Class I malocclusion were selected as the control group. A mandibular model of each subject was plotted with each tooth on a digitizer. The clinical bracket points of each tooth were plotted, and intercanine and intermolar measurements were taken. The least squares method was used to fit a quartic equation, and the arch form was drawn. The Class IIIS group was divided by Wits appraisal and facial pattern into a dolichofacial or brachyfacial pattern, and arch forms were compared. The results show that the Class IIIS group had a significantly smaller intermolar width, canine depth, and molar depth and a significantly larger canine W/D ratio. In those with a dolichofacial pattern, the anterior curve of the arch form tended to be flat and the posterior curve narrower. This is because, in skeletal mandibular prognathism, the mandibular anterior shows lingual tipping, and the molars show palatal tipping due to dental compensation, and it was inferred that this tendency was higher in high-angle cases.

Effect of the Correction of Bilateral Differences in Masseter Muscle Functional Pressure on the Mandible of Growing Rats.

The objective of this study is to clarify the effect of restoring the lowered masticatory muscle functional pressure and correcting bilateral differences in masticatory muscle functional pressure on jawbone growth during growth and development with a quantitative evaluation of the changes in the micro/nanostructural characteristics of entheses. Male Wistar rats aged 4 weeks were divided into an experimental group injected with a botulinum toxin serotype A (BoNT/A) formulation to reduce muscle function (BTX group) and a control group (CTRL group). They were euthanised after 6, 8, 10, 12, and 16 weeks after measuring the difference between the midline of the upper and lower incisors. The mandibles were harvested for histological examination, second harmonic generation imaging, and the quantitative evaluation of biological apatite (BAp) crystal alignment. The midline difference decreased with age in weeks. In rats from 6 weeks after BoNT/A administration to 12 weeks after administration, the collagen fibre bundle diameter was significantly smaller in the BTX group; the difference between the two groups decreased with increasing age. BAp crystal alignment was significantly different on the x-axis and the y-axis on the BTX group from 6 weeks after BoNT/A administration to 10 weeks after administration. Asymmetry of mandibular bone formation caused by load imbalance during growth could be corrected by the adjustment of the function of the masseter muscle on either side.

Relationship between Changes in Condylar Morphology and Masticatory Muscle Volume after Skeletal Class II Surgery.

The treatment of dentofacial deformities generally includes orthognathic surgery in which mandibular condyle changes following surgery are a common cause of relapse. This study investigated the changes in the mandibular condyle and related muscles to identify the factors that affected the changes in the mandibular condyle after orthognathic surgery in skeletal class II patients. This research studied 60 joints in 30 patients with skeletal class II dentofacial deformities who received surgical orthodontic treatment, including bilateral sagittal split ramus osteotomy, and underwent computed tomography before and after orthodontic treatment. The mandibular condyle, masseter, and medial pterygoid muscles were reconstructed and measured in 3D. Condylar positional and morphology changes, masseter and medial pterygoid muscle volume, temporomandibular joint (TMJ) pain, and distal segment movement were analyzed. The study observed that both the masseter and medial pterygoid muscle volumes decreased with statistical significance. The changes in the horizontal direction were positively correlated with the amount of movement. The findings indicated that mandibular condyle changes were significantly affected by the movement of the distal segment, the medial pterygoid muscle volume, and the direction of the distal segment, which influenced the treatment's long-term stability after orthognathic surgery.

Alveolar Bone Microstructure Surrounding Orthodontic Anchor Screws with Plasma Surface Treatment in Rats.

A lateral load was applied to anchor screws that had undergone surface treatment, and the structure, cellular dynamics, and quality of the bone surrounding anchor screws were analyzed to investigate the effect of this surface treatment on the peri-implant jawbone. In addition, bone microstructural characteristics were quantitatively evaluated for each site of loading on the bone around the anchor screw. Rats were euthanized after observation on days 3, 5, or 7, and bone quality analyses were performed. Bone-implant contact rate increased more rapidly at an early stage in the treated surface group than in the untreated surface group. Bone lacuna morphometry showed that the measured values adjacent to the screw at the screw neck on the compressed side (A) and at the screw tip on the uncompressed side (D) were significantly lower than those at the screw tip on the compressed side (B) and at the screw neck on the uncompressed side (C). Collagen fiber bundle diameter showed that the measured values adjacent to regions A and D were significantly higher than those at regions B and C. Anchor screw surface activation facilitates initial bone contact of the screw, suggesting that early loading may be possible in clinical practice.

The effects of orthodontic anchor screw inserted into the femur of growth-phase or mature rats -Osteoid formation, bone mineral density, collagen fiber bundles, biological apatite crystal orientation.

The purpose of this study is to investigate the effect of orthodontic anchor screws (OASs) inserted into the femur of growth-phase or mature rats using histological observation and bone structure analysis. The experimental animals are growth-phase (6-week-old) or mature (25-week-old) male Wistar rats. OAS was placed into the point one-third of the femoral length from the proximal end of the femur, and the response of the surrounding bone was observed and measured. The results showed at the OAS bone interface, in growth-phase rats, bone mineral density (BMD) was reduced and the running angle of collagen fiber bundles varied significantly. In mature rats, more osteoid was observed and biological apatite (BAp) crystals showed a different orientation. It was suggested that after the insertion of OASs, bone volume and quality are decreased, but after a sufficient healing period, a new bone micro/nano structure, different from the original structure, are reconstructed.

Three-Dimensional Analysis of the Cranial Base Structure in Patients with Facial Asymmetry.

Facial asymmetry is often seen in patients with skeletal mandibular prognathism and is associated with deformities in the maxillofacial and head regions. The maxillofacial deviation is three-dimensional and affects not only the lateral deviation of the mandible and midface, but also the cranium. This study conducted a three-dimensional morphological evaluation of the cranial base morphology of patients with skeletal mandibular prognathism (ANB < 0°, Wits < 0 mm) with the aim of examining the relationship between deformities of the head region and facial asymmetry. Data obtained from computed tomography conducted during the initial examination of patients with and without skeletal mandibular prognathism with facial asymmetry were used. Differences in the position of structures present in the cranial base were measured, and the association between cranial deformities and mandibular deviation was assessed. The middle cranial base area and the lateral deviation of the mandibular fossa were significantly larger in patients with facial asymmetry compared to those without facial asymmetry. In addition, a correlation between the amount of mandibular deviation and the area of the anterior cranial base was identified in patients with significant cranial deformity (p = 0.012). Given the identified association between the structure of the head region and facial asymmetry, further studies are needed to determine the factors implicated in the growth process.

External Root Resorption of Second Molars Due to Impacted Mandibular Third Molars during Orthodontic Retention.

Whether there is a relationship between impaction of the third molars and the onset of crowding remains to be determined, and extraction of third molars after orthodontic treatment is left to the judgement of the practitioner. This report describes a case where a third molar caused external root resorption (ERR) of the mandibular second molar after orthodontic treatment. As ERR of the mandibular second molar was detected after non-extraction orthodontic treatment, the affected tooth was extracted and substituted with the third molar. External root resorption of the second molar occurred despite being determined as low risk given the state of the impacted third molar as observed on a panoramic radiograph obtained at the end of active treatment. The present results indicate that in cases where the mandibular third molar is present, the corpus length is short, and non-extraction treatment has been performed, it is necessary to obtain X-ray images on a regular basis or preventively extract the third molar to avoid ERR of the second molars.

Semaphorin 3A regulates alveolar bone remodeling on orthodontic tooth movement.

Semaphorin 3A (Sema3A) promotes osteoblast differentiation and inhibits osteoclast differentiation. In the present study, we observed the regulation of alveolar bone remodeling by Sema3A during orthodontic tooth movement (OTM). Four inflammatory cytokines (IL-1ß, IL-6, TNFα, and INF-γ) involved in OTM were applied to osteoblasts in vitro, and Sema3A expression was determined by reverse-transcription quantitative polymerase chain reaction (RT-qPCR). In vivo, springs were attached to the maxillary first molars of C56BL/6J mice (OTM model) and the localization of Sema3A was confirmed by immunofluorescent. Recombinant Sema3A (rSema3A) was locally injected into the OTM model. Inflammatory cytokine localization in the OTM model was confirmed by immunohistochemistry. In vivo, more Sema3A was observed on the tension side in the OTM group. Injection of rSema3A into the OTM model increased mineralization on the tension side and decreased the number of osteoclasts on the compression side. In vitro, IL-1ß significantly increased Sema3A mRNA levels. Immunohistochemistry for IL-1ß in vivo showed more concentrated staining in the periodontal ligament on the tension side than on the compression side. In summary, our findings revealed the distribution of Sema3A in the periodontal ligament and demonstrated that rSema3A administration promotes bone formation and inhibits bone resorption during OTM.

Quercetin Reduces the Development of 2,3,7,8-Tetrachlorodibenzo-p-dioxin-Induced Cleft Palate in Mice by Suppressing CYP1A1 via the Aryl Hydrocarbon Receptor.

Quercetin is a flavonoid with a wide range of pharmacological activities, including anticancer, antioxidant, and anti-inflammatory effects. Since it is a nutrient that can be consumed with a regular diet, quercetin has recently garnered interest. Quercetin acts as a phytochemical ligand for the aryl hydrocarbon receptor (AhR). Cleft lip and palate are among the most frequently diagnosed congenital diseases, and exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during pregnancy induces cleft palate via AhR. In this study, we investigated the preventive effect of quercetin intake on the TCDD-induced cleft palate and its mechanism of action. The in vivo results suggest that quercetin intake by pregnant mice can prevent cleft palate in fetal mice. In vitro, the addition of TCDD induced a reduction in cell migration and the proliferation of mouse embryonic palatal mesenchymal cells, which was mitigated by the addition of quercetin. The addition of quercetin did not alter the mRNA expression levels of the AhR repressor but significantly suppressed mRNA expression of CYP1A1. In addition, the binding of AhR to a xenobiotic responsive element was inhibited by quercetin, based on a chemically activated luciferase expression assay. In conclusion, our results suggest that quercetin reduces the development of TCDD-induced cleft palate by inhibiting CYP1A1 through AhR.

Three-Dimensional Evaluation of Pharyngeal Morphology in Bimaxillary Surgery with and without Horseshoe Osteotomy in Skeletal Class III Cases.

Repositioning of the jaw in orthognathic treatment generates changes in the soft tissues of the maxillofacial region, with consequent changes in the airway. The purpose of this study was to determine how type of orthognathic surgical procedure affected the 3-dimensional morphology of the upper airway. Forty patients were divided into the following 2 groups according to the type of surgical procedure used: a horseshoe osteotomy (HS) group (20 patients, comprising 11 men and 9 women; average age 24.3±4.5 years) who underwent bimaxillary surgery; and a LeFort I osteotomy (LF) group (20 patients, comprising 8 men and 12 women; average age 22.5±4.6 years) who also underwent bimaxillary surgery. Cephalometric measurements were taken and 3-dimensional pharyngeal morphology evaluated in each group. The amounts of maxilla rotation, posterior maxilla impaction, and mandibular setback all revealed a significantly larger value in the HS group. Evaluation of pharyngeal volume revealed a significant decrease in the upper pharyngeal segment in the LF group. A significant decrease in the lower pharyngeal segment was observed in both groups. Differences were noted in postoperative pharyngeal morphology between the two groups. The results of this study suggest that HS has less effect on the upper pharyngeal segment, regardless of the amount of posterior maxilla impaction.

A Case of Orthodontic Treatment for Generalized Aggressive Periodontitis.

Aggressive periodontitis mostly affects young people, causing rapid destruction of periodontal tissue and loss of supporting alveolar bone. The destruction of periodontal tissue induces pathological tooth movement, resulting in various types of malocclusion such as crowding or spacing in the dentition. This report describes orthodontic treatment for malocclusion due to generalized aggressive periodontitis. The patient was a 31-year-old woman who presented with the chief complaint of displacement in the anterior teeth. An oral examination revealed pathological tooth mobility throughout the entire oral cavity due to severe loss of periodontal support. Many gaps in the displaced maxillary anterior teeth and crowding in the mandibular anterior teeth were also observed. The goal of subsequent treatment was to achieve ideal overjet and overbite by aligning the teeth and closing the spaces via non-extraction orthodontic treatment with stripping. The periodontal disease was managed by a periodontist who provided guidance on oral hygiene and periodontal disease control throughout the course of orthodontic treatment. Appropriate occlusion and a good oral environment were achieved. The condition of the periodontal tissue stabilized during and after orthodontic treatment, and favourable occlusal stability was observed at the 2-year follow-up examination.

A Case of Mandibular Prognathism with Generalized Aggressive Periodontitis and Crowding.

Aggressive periodontitis during adolescence has a poor prognosis due to rapid alveolar bone resorption. Few studies have investigated long-term follow-up after surgical orthodontic treatment performed in conjunction with that for invasive periodontitis. Here, we report a case of mandibular prognathism accompanied by generalized aggressive periodontitis and crowding. A 31-year-old woman was referred to our department for treatment of masticatory dysfunction due to reverse overjet. The patient exhibited a class III molar relationship, protrusion of the ANB of －6.0°, and severe maxillary crowding. Initial periodontal examination revealed deep periodontal pockets and extensive inflammation. Mandibular prognathism accompanied by generalized aggressive periodontitis and crowding was diagnosed. Therefore, it was necessary to adopt an interdisciplinary approach involving surgical, orthodontic, and periodontal treatment. Prior to commencement of orthodontic treatment, plaque control, scaling, and root planing of all teeth were performed by a periodontist to suppress inflammation and reduce probing depth. During pre-surgical orthodontic treatment, the maxillary first premolars were extracted to reduce crowding of the maxillary incisors. To correct the mandibular prognathism, the mandible was repositioned by sagittal split ramus osteotomy. Proper occlusion of the incisors and maximum intercuspation were achieved by post-surgical orthodontic treatment. After completion of active orthodontic treatment, acceleration of inflammation was observed together with aggravated resorption of the alveolar bone surrounding the molars. However, reduction of probing depth and inflammation were observed after scaling and root planing. The surgical-orthodontic treatment time was 1 year and 11 months, which was followed by a 2-year retention period. There was no tooth loss due to periodontitis, and an overall satisfactory outcome was achieved.

Overload of the Temporomandibular Joints Accumulates γδ T Cells in a Mouse Model of Rheumatoid Arthritis: A Morphological and Histological Evaluation.

Recently, it has been reported that γδ T cells are associated with the pathology of rheumatoid arthritis (RA). However, there are many uncertainties about their relationship. In this study, we investigated the morphological and histological properties of peripheral as well as temporomandibular joints (TMJ) in a mouse model of rheumatoid arthritis with and without exposure to mechanical strain on the TMJ. Collagen antibody-induced arthritis (CAIA) was induced by administering collagen type II antibody and lipopolysaccharide to male DBA/1JNCrlj mice at 9-12 weeks of age, and mechanical stress (MS) was applied to the mandibular condyle. After 14 days, 3D morphological evaluation by micro-CT, histological staining (Hematoxylin Eosin, Safranin O, and Tartrate-Resistant Acid Phosphatase staining), and immunohistochemical staining (ADAMTS-5 antibody, CD3 antibody, CD45 antibody, RORγt antibody, γδ T cell receptor antibody) were performed. The lower jawbone was collected. The mandibular condyle showed a rough change in the surface of the mandibular condyle based on three-dimensional analysis by micro-CT imaging. Histological examination revealed bone and cartilage destruction, such as a decrease in chondrocyte layer width and an increase in the number of osteoclasts in the mandibular condyle. Then, immune-histological staining revealed accumulation of T and γδ T cells in the subchondral bone. The temporomandibular joint is less sensitive to the onset of RA, but it has been suggested that it is exacerbated by mechanical stimulation. Additionally, the involvement of γδ T cells was suggested as the etiology of rheumatoid arthritis.

Extraction of Maxillary Central Incisors with Short Roots for Orthodontic Treatment of Maxillary Protrusion and Open Bite.

This case report describes the unusual choice of extraction of maxillary incisors with short roots as part of an orthodontic treatment plan. The patient was a 20-year-old woman referred to our department in whom the diagnosis was maxillary protrusion and open bite. Both of the maxillary central incisors had short roots. Two treatment options were considered. The first involved extraction of the 4 first premolars with the aim of improving dentoalveolar protrusion and crowding. If preservation of the central incisors subsequently became difficult due to root resorption, prosthetic options were to be considered. The second treatment option involved extraction of the maxillary central incisors with short roots and the mandibular first premolars. The second treatment option was selected as survival of the central incisors following orthodontic movement was uncertain and the patient also wanted to minimize the risk of future extractions and the use of prosthetics. Active treatment was performed over a span of 31 months, and circumferential type retainers were used on both arches for retention. For such treatment to be successful, careful diagnosis and orthodontic treatment planning must be taken to ensure the anterior dental esthetics are properly restored.