The hyoid bone: an overview

Hyoid displacement during swallowing function for completely edentulous subjects rehabilitated with mandibular implant retained overdenture

BACKGROUND

Hyoid bone is attached to the mandible, tongue, larynx, temporal bone, and cervical spine via different types of muscles or ligaments. The tongue, mandible, and hyoid system play a crucial role in swallowing function. This within subject study aimed to evaluate the impact of mandibular implant overdentures on the displacement of the hyoid bones during the swallowing process.

METHODS

Twenty five healthy edentulous subjects were selected for participating in the study. New complete dentures were constructed for all the participants. Subsequently two dental implants were inserted in the canine regions of the participant's mandibular arch. In order to retain the mandibular prosthesis in place, ball attachments were incorporated into the mandibular dentures to convert them into implant overdentures. Using 10 ml of thin liquid bolus, videofluoroscopy swallowing examination was performed in three different oral conditions: without complete dentures (WCD), with complete denture (CDs), and with a mandibular implant overdenture (IODs). ANOVA with Bonferroni test was used to analyze the data in order to determine how the hyoid displacement varied throughout different oral conditions.

RESULTS

Compared to complete dentures, mandibular implant overdentures showed a significant decrease (P < 0.05) in both anterior hyoid displacement and duration of hyoid maximum anterior excursion (DOHMAE). However, there was a non-significant difference (P > 0.05) between the two oral circumstances in terms of superior hyoid displacement or duration for hyoid maximum elevation (DOHME). There is no penetration or aspiration for both complete denture and implant overdenture oral conditions.

CONCLUSION

Implant retained overdentures have a positive effect on hyoid displacement during swallowing of thin liquid bolus consistency relative to conventional complete dentures.

TRIAL REGISTRATION

Retrospectively registered (NCT06187181) 02/1/2024.

Modified Sistrunk Procedure in 391 Pediatric Thyroglossal Duct Cyst Cases: Clinical Analysis of Efficacy and Recurrence Risk

Objectives: The study aims to retrospectively summarize the clinical features of pediatric thyroglossal duct cyst (TGDC), investigate the efficacy of the modified Sistrunk (mSis) procedure, and analyze the recurrence risks. Methods: The clinical data of 391 children with TGDC admitted to Beijing Children's Hospital affiliated Capital Medical University and Baoding Children's Hospital from March 2012 to December 2021 were retrospectively analyzed. All patients underwent cervical ultrasound for preoperative evaluation. Twenty cases had magnetic resonance imaging and 8 cases had computed tomography for further evaluation. All patients underwent the standard mSis procedure, and clinical manifestations information, surgical information, complications, and prognosis were analyzed. Results: Among the 391 TGDC cases, 118 (30.2%) had a history of recurrent neck infection and 36 (9.2%) had undergone previous neck cyst and fistula resection surgeries, initially diagnosed as neck cyst (22 cases), TGDC (12 cases), or branchial fistula (2 cases), with only 6 cases having undergone partial hyoid bone resection in the previous operation. During the 15 to 156 months of follow-up, 10 children experienced local wound infection, but no other complications were reported. The recurrence rate was 2.30%, and the recurrence time ranged from 0.5 to 34 (average, 7.2) months post surgery. In the Poisson regression model examining factors related to recurrence, the P values of the 3 factors were <.05: clearness of the lesion boundary, surgical history, and maximum diameter and the relative risk (RR) values corresponding to the 3 risk factors, such as Exp (B), were 27.918, 10.054, and 6.606, respectively. Conclusions: The mSis procedure demonstrated safety and efficacy with fewer complications and a low recurrence rate of 2.30% in the study. Furthermore, the indistinct lesion boundary, surgical history, and large lesion diameter (>2 cm) were independent risk factors for recurrence in pediatric TGDC.Level of Evidence: IV.

Hyoid Bone Fracture Pattern Assessment in the Forensic Field: The Importance of Post Mortem Radiological Imaging

Post mortem hyoid bone fracture findings may be attributable to various factors, including both the onset of acute mechanical asphyxia as it happens in manual strangulation and in charred corpses. In forensic practice, the discovery of corpses burned after death to hide their real cause of death is not uncommon: in these cases, the diagnostic challenge is even greater, as the action of flames is capable of both masking previously generated lesions and/or generating new ones, as occurs for hyoid bone fractures. The case concerns a 76-year-old man found charred in his bedroom. Almost complete body charring made it impossible to evaluate any external damage. Post mortem computed tomography (PMCT) was performed, and an evident bilateral fracture of the greater horn of the hyoid bone was detected. Although the absence of typical charring signs had steered the diagnosis towards post mortem exposure to flames, PMCT proved to be very useful in increasing the accuracy in correctly determining the cause of death. In particular, making use of Maximum Intensity Projection (MIP) hyoid bone reconstructions, it was possible to measure the medial dislocation angle of the fracture fragments and then to establish the applied direction of force, which acted in a lateral-medial way. A manual strangulation diagnosis was confirmed. The increasing importance of performing post mortem radiological exams as a corollary for conventional autopsy has been further confirmed.

Lowered hyoid bone overlapping the thyroid cartilage in CT angiograms

BACKGROUND

The ventral enclosure of the thyroid cartilage by a collapsed hyoid bone (CHB) is poorly encountered in previous research. It was aimed to observe whether or not these malformations could be found and detailed anatomically in a consistent lot of computed tomography (CT) files.

METHODS

Two hundred archived CT angiograms were explicitly observed for the CHB anatomical variant.

RESULTS

Different possibilities of CHB were found in 6/200 cases, five males and one female. The symmetrical overlap of the thyroid cartilage by the hyoid body was found in one male case. In three cases, two males and one female, there was asymmetrical overlapping due to tilted hyoid bones. In one male case with such asymmetrical CHD, an ossified anterior longitudinal ligament was noted: the tips of the superior horns of the thyroid cartilage reached lateral to it, thus being retropharyngeal. A different male case had a lowered hyoid with a greater horn fused to the superior horn of the thyroid cartilage, with an interposed ossified triticeal cartilage. In the last male case, the right greater horn collapsed laterally to an ossified triticeal cartilage fused with the thyroid cartilage's superior horn.

CONCLUSIONS

The CHB is an undeniable anatomical possibility of an atavism that alters conventional anatomical and surgical landmarks. Different anatomical components of the hyoid bone can descend uni- or bilaterally.

Mylohyoid Muscle: Current Understanding for Clinical Management-Part I: Anatomy and Embryology

The mylohyoid is one of the suprahyoid muscles, along with the geniohyoid, digastric, and stylohyoid muscles. It lies between the anterior belly of the digastric muscle inferiorly and the geniohyoid superiorly. In Part I, the anatomy and embryology of the mylohyoid muscle will be reviewed in preparation for the clinical discussion in Part II.

Mylohyoid Muscle: Current Understanding for Clinical Management Part II: Clinical Anatomy, Radiology, and Surgical/Clinical Relevance

The mylohyoid is one of the suprahyoid muscles along with the geniohyoid, digastric, and stylohyoid muscles that lies between the anterior belly of the digastric muscle inferiorly and the geniohyoid superiorly. In Part II, the radiology and clinical/surgical importance of the mylohyoid muscle will be discussed.

Diagnostic value of a deep learning-based hyoid bone tracking model for aspiration in patients with post-stroke dysphagia

Objective

Hyoid bone movement is potentially related to aspiration risk in post-stroke dysphagia (PSD) patients but is difficult to assess quantitatively. This study aimed to measure the distance of hyoid bone movement more efficiently and accurately using a deep learning model and determine the clinical usefulness of the model in PSD patients.

Methods

This study included 85 patients with PSD within 6 months from onset. Patients were grouped into an aspiration group (n = 35) and a non-aspiration group (n = 50) according to the results of a videofluoroscopic swallowing study. Hyoid bone movement was tracked using a deep learning model constructed with the BiFPN-U-Net(T) architecture. The maximum distance of hyoid bone movement was measured horizontally (H max), vertically (V max), and diagonally (D max).

Results

Compared with the non-aspiration group, the aspiration group showed significant decreases in hyoid bone movement in all directions. The area under the curve of V max was highest at 0.715 with a sensitivity of 0.680 and specificity of 0.743. The V max cutoff value for predicting aspiration risk was 1.61 cm. The success of oral feeding at the time of discharge was significantly more frequent when hyoid movement was equal to or larger than the cutoff value although no significant relationship was found between hyoid movement and other clinical characteristics.

Conclusion

Hyoid bone movement of PSD patients can be measured quantitatively and efficiently using a deep learning model. Deep learning model-based analysis of hyoid bone movement seems to be useful for predicting aspiration risk and the possibility of resuming oral feeding.

Effects of maxillary expansion and protraction on pharyngeal airway dimensions in relation to changes in head posture and hyoid position : A retrospective cohort study

PURPOSE

To assess changes in pharyngeal airway dimensions, head posture and hyoid position after maxillary expansion and face mask (FM) treatment compared to untreated class III patients.

METHODS

This study examined 24 class III patients (10 girls, 14 boys, mean age: 10.97 ± 0.88 years) treated with expansion and a petit-type FM appliance and 24 untreated class III patients (16 girls, 8 boys, mean age: 10.50 ± 1.06 years). Pre- and posttreatment cephalometric radiographs were digitally analysed. Parametric data were analysed with paired and independent-samples t‑tests, nonparametric data were analysed with Wilcoxon signed-rank and Mann-Whitney U tests. Spearman's correlation analysis was used to examine the relationship between dental/skeletal treatment changes and those of craniocervical postural position, pharyngeal airway dimension and hyoid position.

RESULTS

With respect to the hypopharyngeal airway dimension, the hypopharyngeal sagittal length (CV3'-LPW), velar angle (HRL/U-PNS) and velar length (U-PNS) significantly increased in the treatment group. All the parameters describing head posture and those describing the distances of the hyoid bone to the HRL changed significantly after treatment, but these changes were not significantly different from the control group. In the treatment group, there also occurred a significant increase in the sagittal growth of the maxilla (SNA, Co‑A, Na-Perp A, Wits), vertical growth of the maxillomandibular complex (SN-GoGN, N‑ANS, N‑Me), counterclockwise rotation of the maxilla (SN-PP) and overjet, while a clockwise rotation (y-axis) and a nonsignificant inhibition of the sagittal growth (Co-Gn) of the mandible were observed. The treatment induced increases of hypopharyngeal sagittal length (CV3'-LPW), soft palate thickness and anteroposterior movement of hyoid bone (H-CV3) demonstrated a positive correlation with changes of craniocervical angles (NSL/OPT, NSL/CVT) and a negative correlation with craniohorizontal angles (OPT/HOR, CVT/HOR). The change of the anteroposterior movement of hyoid bone (H-CV3) was also positively correlated with oropharyngeal sagittal length (CV2'-MPW), the hypopharyngeal sagittal length (CV3'-LPW) and the minimal dimension of the pharyngeal airway space (PASmin).

CONCLUSION

While expansion and FM treatment did not affect the head posture and hyoid bone position, positive effects were observed in the hypopharyngeal airway region.

Comparison of invisalign mandibular advancement and twin-block on upper airway and hyoid bone position improvements for skeletal class II children: a retrospective study

BACKGROUND

This study is to evaluate and compare the improvement of upper airway morphology and hyoid bone position in children with Class II mandibular retrusion treated with Invisalign mandibular advancement (MA) and Twin-Block (TB) appliances, utilizing cone beam computed tomography (CBCT).

METHODS

32 children aged between 8 and 11.5 years old were included in this study, with an average age of 10.2 years old. These children were divided into two groups, MA and TB, with 16 children in each group. Changes in upper airway morphology and hyoid bone position before and after treatment were analyzed using CBCT.

RESULTS

(1) Changes in upper airway before and after treatment: the oropharynx volume (Or-V), the oropharynx minimum cross-sectional area (Or-mCSA), the hypopharynx volume (Hy-V), and the hypopharynx minimum cross-sectional area (Hy-mCSA) in both the MA and TB groups increased after treatment, and the differences were statistically significant (P < 0.05) compared to pre-treatment status. (2) Changes in hyoid bone position before and after treatment: The distances between H point and third cervical vertebra (H-C3), H point and pogonion (H-RGN), H point and mandibular plane (H-MP), H point and Frankfort horizontal plane (H-FH), H and S point (H-S), and H point and palatal plane (H-PP) in both the MA and TB groups increased after treatment, and the differences were statistically significant (P < 0.05).

CONCLUSION

Both MA and TB appliances effectively improved the structural narrowness of the upper airway and reduced respiratory resistance, thus improving breath quality. However, MA showed more effectiveness in improving the narrowest part of the hypopharynx compared to TB. Both appliances also promoted anterior downward movement of the hyoid bone, which opens the upper airway of the oropharynx and hypopharynx and helps the upper airway morphology return to normal range.

Hyoid bone position in subjects with different facial growth patterns of different dental ages

OBJECTIVE

To explore the correlation between hyoid bone (HB) positions and facial growth patterns (facial patterns) in Chinese adults; to identify any significant difference in HB position among subjects with different facial patterns in various dental ages.

METHODS

Lateral cephalometric radiographs of 197 Chinese subjects were divided into nine groups based on their dental ages and facial patterns. Seven measurements were used to define HB position. Regression, correlation analyses, and one-way ANOVA were carried out.

RESULTS

Significant correlations were found between facial patterns and anteroposterior HB positions. The HB was more anterior in the horizontal group after mixed dentition and further away from the mandibular plane in the vertical group of adults. Vertical HB positions were insignificantly different in any stage.

CONCLUSION

HB position and facial patterns were correlated. There were significantly different HB positions among people with different facial patterns in various dental ages.

Modeling the influence of the extrinsic musculature on phonation

Neck muscles play important roles in various physiological tasks, including swallowing, head stabilization, and phonation. The mechanisms by which neck muscles influence phonation are not well understood, with conflicting reports on the change in fundamental frequency for ostensibly the same neck muscle activation scenarios. In this work, we introduce a reduced-order muscle-controlled vocal fold model, comprising both intrinsic muscle control and extrinsic muscle effects. The model predicts that when the neck muscles pull the thyroid cartilage in the superior-anterior direction (with a sufficiently large anterior component), inferior direction, or inferior-anterior direction, tension in the vocal folds increases, leading to fundamental frequency rise during sustained phonation. On the other hand, pulling in the superior direction, superior-posterior direction, or inferior-posterior direction (with a sufficiently large posterior component) tends to decrease vocal fold tension and phonation fundamental frequency. Varying the pulling force location alters the posture and phonation biomechanics, depending on the force direction. These findings suggest potential roles of particular neck muscles in modulating phonation fundamental frequency, with implications for vocal hyperfunction.

Reconsideration of hyoid bone syndrome-A case series with a review of the literature

BACKGROUND

Hyoid bone syndrome is a type of faciocervical pain and occasionally concomitant clicking larynx that is caused by degeneration and/or elongation of the greater horn of the hyoid bone at the attachment of the stylohyoid ligament.

CASES PRESENTATION

We report five patients who presented with deep-seated, dull, aching, throat pain that radiated from neck, accompanying by throat clicking while speaking, swallowing, yawning, and turning head. Most notably, one of them also complained an intermittent ulcer hemorrhage in the tongue base. Diagnostic tests included physical palpation of the hyoid greater cornu and computed tomography examination. One patient did not accept the surgery, but other than that four patients responded well to resection of the abnormal hyoid bone, which resulted in immediate and complete relief of their symptoms and with no postoperative complications.

CONCLUSIONS

Clicking sensation and pain while deglutition is an unpleasant condition, which produces physiological and psychological bearings. This dictates the need for accurate diagnosis and proper management of the condition. Oral and maxillofacial surgeons involved in the treatment of orofacial pain should consider this rare condition as a differential diagnosis.

Physiological Mechanisms and Associated Pathophysiology of Dysphagia in Older Adults

Dysphagia can be a common secondary sequela of neurological and neurodegenerative disorders in older adults. Early screening, identification, and management of dysphagia is essential to avoid serious complications, including malnutrition, dehydration, aspiration pneumonia; and promote quality of life. Although individuals of all ages may experience swallowing difficulties, dysphagia and its complications are more common in older adults. This literature review aims to provide an overview of the physiological mechanisms of normal swallowing in healthy individuals and age-related changes to swallowing function, the pathophysiology of dysphagia associated with three common neurological disorders affecting older adults (stroke, Parkinson's disease, and dementia), and implications for interdisciplinary clinical practice. Increased awareness of these issues may contribute to a more timely and efficient identification of older adults with dysphagia and to improve overall dysphagia management.

Noninvasive Evaluation of the Biomechanical Accommodations to Bolus Volume during Human Swallowing

Bolus volume is very important in the biomechanics of swallowing. By noninvasively characterizing swallow responses to volume challenges, we can gain more knowledge on swallowing and evaluate swallowing behavior easily. This study aimed to evaluate the impact of bolus volume on the biomechanical characteristics of oropharyngeal swallowing events with a noninvasive sensing system. Fifteen healthy male subjects were recruited and instructed to swallow 5, 10, and 15 ml of water. The sensing system consisted of a tongue pressure sensor sheet, bend sensor, surface electrodes, and a microphone. They were used to monitor tongue pressure, hyoid activity, surface EMG of swallowing-related muscles, and swallowing sound, respectively. In addition to the onset, the peak time and offset of the above four structures, certain characteristics, such as the duration, peak value, and interval of the structure motions, were measured during the different drinking tasks. The coordination between the hyoid movement and tongue pressure was also assessed. Although no sequence of the structural events changed with volume, most of the timings of the structural events were significantly delayed, except for certain hyoid activities. The swallowing volume did not affect the active durations of the monitored structures, the peak values, or intervals of tongue pressure and supra- and infrahyoid muscle activity, but certain hyoid kinetic phases were prolonged when a larger volume was swallowed. Additionally, sequential coordination between hyoid movement and tongue pressure was confirmed among the three volumes. These findings suggest that oropharyngeal structural movements change in response to bolus volume to facilitate safe swallowing. The noninvasive and quantitative measurements taken with the sensing system provide essential information for understanding normal oropharyngeal swallowing.

Position of the Hyoid Bone and Dimension of Nasopharynx and Oropharynx after Occlusal Splint Therapy and Physiotherapy in Patients Diagnosed with Temporomandibular Disorders

Background: The aim of the study was to assess the position of the hyoid bone, as well as the width of the nasopharynx and oropharynx after occlusal splint therapy combined with physiotherapy in patients diagnosed with temporomandibular disorders (TMD). Methods: This was a clinical trial study. The study group consisted of 40 patients diagnosed with TMD, who were qualified for the treatment combining physiotherapy and occlusal splint therapy. Hyoid bone position as well as the width of the nasopharynx and oropharynx were assessed in lateral cephalograms taken before and after the end of the treatment. There were 15 generally healthy participants included into the control group, who had taken lateral cephalograms twice within the period of 1 to 2 years and did not receive any occlusal treatment in the meantime. Results: The position of the hyoid bone was significantly lowered and the dimension of the lower part of the oropharynx was significantly decreased after the end of the long-term occlusal splint therapy combined with physiotherapy in patients diagnosed with TMD. Conclusions: Long-term occlusal splint therapy combined with physiotherapy affected the position of the hyoid bone and the dimension of the lower part of the oropharynx.

Residue localization and risk for aspiration in partial laryngectomy: the relevance of assertive therapeutic strategies and resources

Objective:

To describe the correlation between the residues, their anatomical location and the presence of laryngotracheal penetration and aspiration in patients after supracricoid laryngectomy undergoing cricohyoidoepiglotopexy reconstruction.

Methods:

This study included 70 patients treated by supracricoid laryngectomy with cricohyoidoepiglotopexy reconstruction in a referral national cancer hospital. The patients were submitted to swallowing videofluoroscopy, and the findings were classified by the penetration and aspiration scale. The images were described observing the presence or absence of residues and their anatomical location.

Results:

The prevalence of penetration in this study was 68.6% and aspiration was 34.3%. An association was found between the presence of residue on the tongue (p=0.005), posterior pharyngeal wall (p=0.013), pyriform recesses (p=0.002), valecula (p=0.061), and laryngeal penetration. The residue in the upper esophageal sphincter (p=0.039) was associated with the occurrence of laryngotracheal aspiration.

Conclusion:

Patients undergoing supracricoid laryngectomy with cricohioidoepiglotopexy reconstruction have food residues in different anatomical regions after swallowing. Penetration was associated with the presence of residues on the base of the tongue and posterior pharyngeal wall. Aspiration was associated with the presence of residues in the upper esophageal sphincter.

Radiographic studies of the hyoid bone and cervical spine in Angle Class I and Class II/2nd Division malocclusions

Abstract Introduction Interdisciplinary investigative study of the stomatognathic-cervical complex, necessary to understand the structure and biomechanics of the hyoid bone and cervical spine in Class I and II / 2nd Division participants. Objective To analyze the position of the hyoid bone and the curvature of the cervical spine on lateral radiographs of participants with Class I and II/2nd Division Angle malocclusion. Material and method We evaluated the position of the hyoid bone from its alignment with the corresponding cervical vertebra. The presentation of curvature of the cervical spine was evaluated from the fourth cervical vertebra. Result There was a statistically significant difference in the position of the hyoid bone (p=0.027) between the classes, which was located at C3 in Class I and further down, between C3 and C5, in Class II/2nd Division. The cervical spine showed alterations in both classes, with an increase, rectification, and inversion of the curvature with no statistical difference between them (p=0.533). Conclusion In this study, the hyoid bone showed different positions in the malocclusions studied, however, poor posture of the cervical spine was common in both classes.

Hyoid Bone Position in Patients with and without Temporomandibular Joint Osteoarthrosis: A Cone-Beam Computed Tomography and Cephalometric Analysis

Objective

To assess the differences in hyoid bone position in patients with and without temporomandibular joint osteoarthrosis (TMJOA).

Methods

The present cross-sectional study was conducted in 427 participants whose osseous status was evaluated using cone-beam computed tomography and classified into normal, indeterminate osteoarthrosis (OA), and OA. The hyoid bone position and craniofacial characteristics were evaluated using cephalograms. Patients were divided into the normal group (N = 89), indeterminate OA group (N = 182), and OA group (N = 156). Descriptive statistics, one-way analysis of variance, and age- and sex-based stratified analyses were performed. P < 0.05 was considered statistically significant.

Results

The differences in Hy to MP, Hy-RGn, Hy to C3-RGn, C3-RGn, and Go-Hy-Me among the three groups were statistically significant. The differences in the Frankfort-mandibular plane angle, saddle angle, articular angle, gonial angle, ramus height, and posterior facial height were statistically significant. After adjusting age and sex, the Hy-RGn and C3-RGn in the normal group were significantly greater than the OA group. No statistical differences were observed in the hyoid measurements in the stratified analyses in males or subjects less than 18 years old. The differences in Hy to MP, Hy to C3-RGn, and Go-Hy-Me in female patients among the three groups were statistically significant. The differences in Hy to SN, Hy to FH, Hy to PP, Hy to MP, Hy-RGn, Hy-C3, Hy to C3-RGn, Go-Hy-Me, Hy-S, and C3-Hy-S in adults were statistically significant.

Conclusion

The differences in the hyoid bone position, mainly relative to the mandible, were statistically significant in patients with or without TMJOA. The difference pattern varied among different age and sex groups. Clinical evaluation of the hyoid position must consider the age and sex of patients. Longitudinal studies are required to clarify the causal relationship between TMJOA and hyoid bone position.

Comparison of hyoid bone morphology between obstructive sleep apnea patients and healthy individuals

OBJECTIVE

We aimed to find morphological properties of the hyoid bone, which are predominant among the patients diagnosed with obstructive sleep apnoea (OSA), and compare them with healthy individuals.

METHODS

A total of 67 cone-beam computed tomography (CBCT) image sequences of patients (44 males, 23 females) diagnosed with OSA and a total of 70 multislice computed tomography (MSCT) data of non-OSA patients (45 males, 25 females) were selected in this study. DICOM images were imported into InVivo 5.1.2 (Anatomage) software. The position of the hyoid bone relative to the C3 and C4 cervical vertebrae, as well as its morphological type (B, V, U, H, D, HK-type) and its total volume was determined.

RESULTS

The volumetric values of the hyoid bone of OSA patients (2384.49 ± 682.073 mm³ ) were significantly (P < .001) lower compared to the values derived from non-OSA patients (2952.96 ± 932.5 mm³ ). The difference was independent of gender, and volumetric values showed a strong significant (P < .01) difference between male OSA and non-OSA (2709.18 ± 608.05; 3157.87 ± 926.5 mm³ ) and female OSA and non-OSA patients (1763 ± 242.51 2584; 2584.12 ± 840.21 mm³ ), as well. In the case of B and V-types, the volumetric values showed significant differences (P < .05), when the OSA (2300,77 ± 622; 2166 ± 312 mm³ ) and non-OSA patients were compared (2823,48 ± 780; 3216 ± 463 mm³ ).

CONCLUSION

Our results suggest that the volume of the hyoid bone might be a potential biological marker for OSA, especially in the case of B and V hyoid bone types.

Msx1 haploinsufficiency modifies the Pax9-deficient cardiovascular phenotype

BACKGROUND

Successful embryogenesis relies on the coordinated interaction between genes and tissues. The transcription factors Pax9 and Msx1 genetically interact during mouse craniofacial morphogenesis, and mice deficient for either gene display abnormal tooth and palate development. Pax9 is expressed specifically in the pharyngeal endoderm at mid-embryogenesis, and mice deficient for Pax9 on a C57Bl/6 genetic background also have cardiovascular defects affecting the outflow tract and aortic arch arteries giving double-outlet right ventricle, absent common carotid arteries and interruption of the aortic arch.

RESULTS

In this study we have investigated both the effect of a different genetic background and Msx1 haploinsufficiency on the presentation of the Pax9-deficient cardiovascular phenotype. Compared to mice on a C57Bl/6 background, congenic CD1-Pax9^-/- mice displayed a significantly reduced incidence of outflow tract defects but aortic arch defects were unchanged. Pax9^-/- mice with Msx1 haploinsufficiency, however, have a reduced incidence of interrupted aortic arch, but more cases with cervical origins of the right subclavian artery and aortic arch, than seen in Pax9^-/- mice. This alteration in arch artery defects was accompanied by a rescue in third pharyngeal arch neural crest cell migration and smooth muscle cell coverage of the third pharyngeal arch arteries. Although this change in phenotype could theoretically be compatible with post-natal survival, using tissue-specific inactivation of Pax9 to maintain correct palate development whilst inducing the cardiovascular defects was unable to prevent postnatal death in the mutant mice. Hyoid bone and thyroid cartilage formation were abnormal in Pax9^-/- mice.

CONCLUSIONS

Msx1 haploinsufficiency mitigates the arch artery defects in Pax9^-/- mice, potentially by maintaining the survival of the 3rd arch artery through unimpaired migration of neural crest cells to the third pharyngeal arches. With the neural crest cell derived hyoid bone and thyroid cartilage also being defective in Pax9^-/- mice, we speculate that the pharyngeal endoderm is a key signalling centre that impacts on neural crest cell behaviour highlighting the ability of cells in different tissues to act synergistically or antagonistically during embryo development.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2020 professional literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to this work to cover this broad topic. Specific subject areas addressed include prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders (TMDs); sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence day-to-day dental treatment decisions with a keen eye on future trends in the profession. With the tremendous volume of dentistry and related literature being published today, this review cannot possibly be comprehensive. The purpose is to update interested readers and provide important resource material for those interested in pursuing greater detail. It remains our intent to assist colleagues in navigating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the dental patients they encounter.

Contributions of anatomy to forensic sex estimation: focus on head and neck bones

This study sought to provide an up-to-date review of the importance of anatomy to human identification, focusing on the usefulness of anatomical knowledge about the head and neck bones and teeth to sex estimation in routine forensic anthropology methods. A detailed search of osteology applications in forensic sex estimation was conducted through the electronic databases for the 10 years prior to July 2020. Relevant articles and classic literature on the subject were gathered and are outlined in this review. Among the available literature, several metric analyses showed accuracy superior to 80% in sexual diagnosis. Angles measured from the inclination of glabellae and analysis of the external frontal bone surface through three-dimensional computer-aided design emerge as reliable cranial indexes for sex estimation. In the mandible, the condylar and coronoid height, bigonial width, and coronion–gonion distance express significant sexual dimorphism. Measurements of the canine are the best option for sex estimation using teeth, as well as the thickness of the dentine or enamel of incisors. The axis vertebra surpasses other neck bones for sex estimation due to its atypical shape and the presence of the odontoid process. Metric analyses based on anatomy can provide reliable accuracy in sexual diagnosis. Adequate training and anatomical knowledge can reduce bias and interobserver differences, and the use of three-dimensional models and computed tomography images can enhance the accuracy of these methods for sex estimation. However, every method should be validated before being applied to a different population.

Key Points

• Anatomy-based metric analyses can provide reliable accuracy in forensic sex estimation.

• Glabellae inclination, external frontal bone surface, mandible, and canine teeth measurements can reach accuracies superior to 80% in sexual diagnosis.

• The use of three-dimensional models and computed tomography images can enhance accuracy in sex estimation.

• Every method should be validated before being applied to a different population.

Hyoid Bone Tracking in a Videofluoroscopic Swallowing Study Using a Deep-Learning-Based Segmentation Network

Kinematic analysis of the hyoid bone in a videofluorosopic swallowing study (VFSS) is important for assessing dysphagia. However, calibrating the hyoid bone movement is time-consuming, and its reliability shows wide variation. Computer-assisted analysis has been studied to improve the efficiency and accuracy of hyoid bone identification and tracking, but its performance is limited. In this study, we aimed to design a robust network that can track hyoid bone movement automatically without human intervention. Using 69,389 frames from 197 VFSS files as the data set, a deep learning model for detection and trajectory prediction was constructed and trained by the BiFPN-U-Net(T) network. The present model showed improved performance when compared with the previous models: an area under the curve (AUC) of 0.998 for pixelwise accuracy, an accuracy of object detection of 99.5%, and a Dice similarity of 90.9%. The bounding box detection performance for the hyoid bone and reference objects was superior to that of other models, with a mean average precision of 95.9%. The estimation of the distance of hyoid bone movement also showed higher accuracy. The deep learning model proposed in this study could be used to detect and track the hyoid bone more efficiently and accurately in VFSS analysis.

Microstructure of the hyoid bone based on micro-computed tomography findings

In this study, micro-CT was used to observe the microscopic anatomy of the hyoid bone, examine the variation of the trabecular bone inside the hyoid bone, and investigate the internal structure of the hyoid bone.A total of 22 hyoid bones were scanned using micro-CT. The changes in the internal bone trabeculae were assessed with 3D reconstructions, and the fine anatomical structure of the hyoid bone was further analyzed.Micro-CT images showed the microstructure of various parts of the hyoid bone. There were significant differences in total volume, bone volume, bone area, bone density, and volume fraction between the body and greater horns of the hyoid bone (P < .05), but no significant differences in the ratio of bone area/volume and bone surface density were found between the body and greater horns of the hyoid bone (P > .05). In addition, significant differences in the trabecular bone measurements, bone trabecular connectivity, and Euler number were found between the body and greater horns of the hyoid bone (P < .05). Other parameters, including bone trabecular thickness, number of trabecular bones, bone trabecular structure model index, and anisotropy of bone trabeculae, did not differ between the body and greater horns of the hyoid bone (P > .05). There was noticeably ossified healing at the joint between the body and greater horns of the hyoid bone.Micro-CT can adequately display the internal structure of the hyoid bone. The identified bone structure may help clarify the physiological function of the hyoid bone. The present findings provide a theoretical basis for further studies aimed at pathological changes due to hyoid injury in clinical and forensic medicine.

Effect of suprahyoid muscles on mouth opening with and without lateral pterygoid muscle: 3D inverse dynamic model analysis

Objective: To evaluate the contribution of suprahyoid muscles to mouth opening in different hyoid bone positions.Methods: The jaw-opening and closing movements were imposed on the 3D inverse dynamic jaw model with and without the lateral pterygoid muscle (LPM). The activation of the muscles was evaluated for eight different positions of the hyoid bone.Results: The muscles with 100% activation provided maximum mouth opening (MMO). When the hyoid bone was replaced, the muscles could achieve MMO at the 135º, 180º, and 225º points with the LPM. Mouth opening was estimated to be 36.8 mm in the absence of the LPM. A jaw opening greater than 36.8 mm was seen when the hyoid bone was repositioned at the 90º, 180º, and 135º points.Discussion: The contribution of suprahyoid muscles to mouth opening varies in different hyoid bone positions, with the inferior and anterior positions having a positive impact.