Mandibular Arch Research Articles

A new approach for sex prediction by evaluating mandibular arch and canine dimensions with machine-learning classifiers and intraoral scanners (a retrospective study).

In circumstances where antemortem information concerning the deceased individual is unavailable, forensic experts prepare biological profiling for unidentified human remains that aids in narrowing the search for identity. Biological profiling includes basic demographic information such as sex, age, stature, and ethnicity. Sex identification is the first and key step in the biological profiling of unidentified human remains, as it effectively reduces potential matches by excluding nearly one-half of the suspected cases and facilitates the subsequent stages. This study was conducted to assess the accuracy of artificial intelligence (AI) in predicting sex by analysing mandibular canine dimensions, mandibular intercanine distance (MICD), and mandibular canine index (MCI) obtained from three-dimensional (3D) digital impressions captured by using an intraoral scanner (IOS). The results of the receiver operating characteristic (ROC) test indicated that mean mandibular canine width (MeanMCW) had the highest sexual dimorphism with the area under the curve (AUC) of 0.912, and the Gaussian Naive Bayes (GNB) classifier demonstrated the highest testing accuracy among all machine learning (ML) models, achieving an accuracy of 92.5%. While the outcomes of this study are promising, further studies are imperative to validate these findings with larger sample sizes in different ethnic populations.

Accuracy of different maxillomandibular relationship recording techniques in the edentulous maxillary arch.

This study investigated the effect of three digital bite registration techniques on the accuracy of intraoral scanning in maxillary edentulous and mandibular dentate arches. Maxillary edentulous and mandible fully dentate models were created. Four dental implants were placed in the maxilla, fitted with scan bodies, and reference scans were obtained using a Nikon Altera 10.7.6 scanner. Digital impressions were acquired 10 times for each model using a Trios 4 intraoral scanner. Three different digital bite records were collected for each pair of mandible and maxilla scans. The first one was a bite record without additional material (WSB), the second utilized a silicone index between the models (WSB silicone), and the third followed a pre-preparation scanning protocol (Pre-PREP). The data was exported in standard tessellation language (STL) format, which was assessed for trueness and precision using statistical analysis. According to mean trueness values, WSB exhibited the lowest value, 173 µm, followed by WSB silicone 242 µm and Pre-PREP 620 µm. The differences were significant only when comparing Pre-PREP to WSB and Pre-PREP to WSB silicone (p <0.05). Regarding precision, WSB demonstrated a mean value of 171.5 µm, followed by WSB silicone with 213.8 µm, and Pre-PREP with 222.2 µm with no significant difference between the groups. The presence of interarch bite registration material adversely affected interocclusal record accuracy, while WSB silicone presented a suitable substitute for WSB.

Abstract 4140180: The Effect of Benzodiazepine Use in Patients with Atrial Fibrillation and Obstructive Sleep Apnea

Introduction: Sleep apnea is a common sleep disorder that can worsen atrial fibrillation(AF) prognosis. Benzodiazepines(BZD) are commonly prescribed for insomnia, which often accompanies sleep apnea. However, BZDs have been associated with worsening of sleep apnea due to respiratory depression, pharyngeal muscle relaxation, and increase of arousal threshold, which all may lead to prolonged hypoxia. There is little research on the effect of BZD use in AF patients with sleep apnea. Therefore, the objective of this study is to investigate the effects of BZD usage on outcomes in the AF population with sleep apnea. Methods: Data from patients with AF and sleep apnea seen at Tulane Medical Center between 2010 and 2019 was obtained from Research Action for Health Network(REACHnet), a Clinical Research Network in PCORnet®. Patients with AF and sleep apnea were divided between those with a prescription of BZD and those without BZD. These two groups were compared using the Kaplan-Meier method for time-to outcome for all-cause mortality, ischemic stroke, myocardial infarction(MI), and hospitalizations in the five years following their AF diagnosis. Cox regression analysis was used to investigate proportional hazards and control for demographics, comorbidities, and medication use. Results: There were 524 total patients included with AF and sleep apnea. Of these, 413(78.8%) were not prescribed BZDs, while 111(21.1%) were taking BZDs. Use of BZDs was associated with worse outcomes. In the no BZD and the BZD group over the 5 years following AF diagnosis, the rate of mortality was 6.1% and 12.6%(p&lt;.001), the rate of ischemic stroke was 16% and 23.4%(p=.008), the rate of MI was 11.9% and 22.5%(p&lt;.001), and the rate of hospitalization was 51.8% and 59.5%(p&lt;.001), respectively. In multivariate Cox regression, use of BZD was associated with higher mortality(HR: 2.65; CI: 2.26-3.05; p=.013) and hospitalization(HR: 2.15; CI: 1.99-2.31;p&lt;.001). Conclusion: BZD use was associated with an over 2-fold increase in all-cause mortality and hospitalizations in patients with AF and sleep apnea. This suggests that BZDs should be used with caution in this patient population, and other treatment modalities for insomnia should be considered.

Middle Ear Malformations

Middle ear malformations (MEMs) represent a diverse group of congenital anomalies with significant implications for auditory function. These malformations, which occur in approximately 0.5 to 3% of conductive hearing loss cases, can arise from various genetic and environmental factors. They often manifest unilaterally and may occur in isolation or as part of a syndromic condition. MEMs are closely associated with abnormalities of the external ear and less frequently with inner ear anomalies.Embryologically, the middle ear develops from the first and second pharyngeal arches, with interactions between the ectoderm and endoderm contributing to the formation of essential structures such as the tympanic membrane, ossicles and Eustachian tube. Disruptions in these developmental processes can lead to a spectrum of MEMs, ranging from minor defects to severe malformations affecting multiple middle ear components.Clinical management of MEMs requires a multidisciplinary approach, involving otolaryngologists, pediatricians, and audiologists. Early intervention with appropriate hearing aids, including conventional hearing aids and bone conduction devices, is essential to mitigate the impact of conductive hearing loss on speech and language development, particularly in children.Surgical planning involves comprehensive preoperative assessment, including high-resolution computed tomography imaging to evaluate middle ear anatomy, the facial nerve course, and vascular anomalies. Traditional surgical approaches such as stapesplasty and tympanoplasty remain mainstays for correcting specific middle ear defects, while advances in technology have expanded the role of active middle ear implants in treating special cases.In conclusion, MEMs represent a heterogeneous group of congenital anomalies with diverse etiologies and clinical implications. A thorough understanding of their embryological basis, genetic underpinnings, and surgical management strategies is crucial for optimizing outcomes in affected individuals.

Modified salpingopharyngeus myomucosal flap: a novel technique for skull base reconstruction.

Advancements in endoscopic skull base surgery have enabled complex tumor resections, necessitating a variety of reliable reconstructive techniques to repair resultant defects. Vascularized flaps represent optimal options, but frequently used local pedicled intranasal flaps may be unavailable due to tumor invasion or prior surgery. This study applies a modification to the previously described salpingopharyngeus myomucosal flap (Dicle flap) with potential for its use in extensive endoscopic skull base surgery defect's repair. Cadaveric dissections (n = 5) were performed utilizing endoscopic visualization to access the skull base via endonasal and transoral routes. A superiorly based posterior pharyngeal myomucosal flap along the salpingopharyngeus muscle was elevated off the superior pharyngeal constrictors, preserving their vascular pedicles. This combined flap could be 180 degrees transposed to reconstruct clival defects up to the sella turcica. The modified salpingopharyngeus myomucosal flap (Modified Dicle flap) provided approximately 40 cm2 of robust vascularized tissue based on the ascending pharyngeal artery and random posterior pharyngeal vessels. It was sufficiently mobilized to cover extensive skull base defects in the craniocervical junction, sella turcica, and protecting the exposed internal carotid artery segments. The modified Dicle flap offers a viable reconstructive option for extensive endoscopic endonasal skull base defects when commonly utilized vascularized flaps are unavailable. Further research on clinical cases is warranted to investigate postoperative function and refine techniques to minimize donor site morbidity. Not applicable.

A Computational Model Reveals How Varying Muscle Activation in the Lateral Pharyngeal Wall and Soft Palate Differentiates Velopharyngeal Closure Patterns.

Finite element (FE) models have emerged as a powerful method to study biomechanical complexities of velopharyngeal (VP) function. However, existing models have overlooked the active contributions of the lateral pharyngeal wall (LPW) in VP closure. This study aimed to develop and validate a more comprehensive FE model of VP closure to include the superior pharyngeal constrictor (SPC) muscle within the LPW as an active component of VP closure. The geometry of the velum and the lateral and posterior pharyngeal walls with biomechanical activation governed by the levator veli palatini (LVP) and SPC muscles were incorporated into an FE model of VP closure. Differing muscle activations were employed to identify the impact of anatomic contributions from the SPC muscle, LVP muscle, and/or velum for achieving VP closure. The model was validated against normative magnetic resonance imaging data at rest and during speech production. A highly accurate and validated biomechanical model of VP function was developed. Differing combinations and activation of muscles within the LPW and velum provided insight into the relationship between muscle activation and closure patterns, with objective quantification of anatomic change necessary to achieve VP closure. This model is the first to include the anatomic properties and active contributions of the LPW and SPC muscle for achieving VP closure. Now validated, this method can be utilized to build robust, comprehensive models to understand VP dysfunction. This represents an important advancement in patient-specific modeling of VP function and provides a foundation to support development of computational tools to meet clinical demand.

New titanium mesh design method in customized bone regeneration of the jaws: preliminary study on a sample of 11 patients

The aim of this study is 1) to present a new method of virtually-designed custom made scaffolds to be employed in customized bone regeneration (CBR) for segmental jaw atrophies and 2) to evaluate long-term clinical results in terms of bone regeneration success and implant rehabilitation success. A total of 11 patients with edentulousness and bone atrophy in a localized area of the mandible or the maxilla were recruited for the study. To fulfill the research inquiries, CT images of the pre-regeneration mandibular or maxillary arch of each patient were collected. A dedicated Mevislab 2.4 software was employed to virtually design custom bone regeneration meshes designed to fit the atrophic sector of each patient's mandible or maxilla. Subsequently, a second Meshmixer software was used to refine the margins of each of the designed meshes. All patients underwent oral surgery, during which a mixture of autologous and heterologous bone in a 1:1 proportion was grafted into the atrophic site, a custom-made mesh was placed, and a resorbable membrane was inserted. The mesh was removed after this procedure, and implant rehabilitation was performed. All patients underwent the bone regeneration procedure, with eight undergoing titanium mesh removal. A total of seven patients completed implant rehabilitation. Average horizontal bone augmentation was 3.525 ± 1.36 mm; average vertical bone augmentation was 4.45 ± 2.22 mm. Implant survival was 92.85%. During the healing phase, complications occurred in 9.09% of patients. The use of dedicated software, Mevislab 2.4 and Meshmixer, for titanium mesh design is an accurate, predictable, effective, and quick-to-use method. The learning curve for design is uncomplicated and rapid. Mesh exposure does not necessarily lead to bone graft failure; this complication can be treated by chlorhexidine aids.

Prevalence of Edentulousness among Patient visiting a Tertiary Care Centre

Introduction: Absence of teeth i.e., edentulism is a common oral health issue worldwide and is an under evaluated disability. It is a preventable oral disability which brings major impact on overall health of individuals affecting the function, aesthetics, comfort and psychology. So, it should be identified and awareness for its management should be done so as to improve the quality of life of an individual. Objective: The purpose of this study was to collect baseline data on edentulism in the Nepalese population so that community-level awareness and educational programs could explain the importance of replacement lost teeth with prosthesis. Methods: The study was conducted in the College of Medical Sciences in the department of Oral medicine and Radiology and in the department of Prosthodontics from the patient visiting in these OPD for five months duration. Data were recorded in proforma and classified as complete / partial edentulous and further classified into Kennedy’s classification. The data were recorded and analyzed in SPSS 20. Result: Out of 301 patients, 24 (8%) had total edentulism, while 277 (92% had partial edentulism). Of the partially edentulous individuals, 90 showed just maxillary edentulism, 148 showed only mandibular edentulism, and 39 showed both maxillary and mandibular edentulism. Conclusion: Females were more likely than males to exhibit partial edentulism. Females showed more Kennedy's Class III classification than males. Both had equal complete edentulism. The mandibular arch showed more partial edentulism than the maxillary arch.

Determination of Maxillary and Mandibular Arch Width in Angle’s Class I Patients

Introduction: The transverse dimension plays a key role in smile. Maintaining the pretreatment arch form is a key to obtaining stable results. Objectives: The main aim of this study was to determine mean intercanine arch width and mean intermolar arch width in Angle’s class I patients. Methods: Seventy-six pretreatment casts were obtained from the records of patients who sought orthodontic treatment in Orthodontics and Dentofacial Orthopedics. Four parameters were used in this study namely; intercanine arch width and intermolar arch width in maxilla and mandible. Linear measurements were carried out with digital caliper. Kappa test was done for intra-observer reliability. Shapiro-Wilk test was done to determine the normal distribution of data. The Pearson Correlation test was done to assess the correlation between intercanine and intermolar arch width in maxilla and mandible. The independent t-test was used to compare between intercanine and intermolar arch width with male and female. Results: Mean intercanine arch width in maxilla and mandible were 35.41±1.47 mm and 26.85±1.59 mm respectively. Mean intermolar arch width in maxilla and mandible were 53.82±2.82 mm and 51.71±2.60 mm respectively. Statistically significant difference was found between intercanine and intermolar arch width in maxilla and mandible between male and female. The intercanine and intermolar arch width in maxilla and mandible has significantly low correlation. Conclusions: Intercanine and intermolar arch width in male and female were statistically significant and male has lager intercanine and intermolar arch width than female.

Analysis of 15 children with type Ⅳ branchial cleft cyst treated with endoscopic transoral approach

Objective: To analyze the clinical characteristics and endoscopic surgical procedures of the second branchial cleft cyst type Ⅳ in children. Methods: A retrospective review was conducted on 15 pediatric cases with type Ⅳ second branchial cleft cysts treated at the Beijing Children's Hospital affiliated with Capital Medical University and Henan Children's Hospital from September 2019 to November 2023. All patients underwent excision via a two-person, three-hand endoscopic transoral approach. The cohort included 12 males and 3 females, with an age range of 10 months to 10 years and 5 months, and a median age of (59.20±32.05) months. The clinical data of initial symptoms, sides, imaging features, treatment methods, complications, length of hospital stay, prognosis and outcome were recorded and analyzed. SPSS 22.0 software was used for statistical analysis. Results: Of the 15 children, 13 cases presented with snoring as the primary symptom, 1 case with dysphagia, and 1 case was asymptomatic and was found unintentionally. The mean disease duration was (6.74±9.05) months (range, from 3 days-2 years). MRI revealed cystic lesions on the right side in 12 cases and on the left side in 3 cases, characterized by uniform long T2 signal, equal T1 or short T1 signal. The cysts appeared dumbbell-shaped in 10 cases with the pharyngeal constrictor muscle as the waist, the posterior outside of the mass was adjacent to the internal carotid artery. The remaining 5 cases showed an isolated cyst located inside the pharyngeal constrictor muscle. The intraoperative MRI findings were consistent. Partial cystectomy was performed in 10 cases near the internal carotid artery, leaving only the portion with a clear arterial pulse intact. Five cases with isolated cysts on the medial side of the pharyngeal constrictor muscle were totally removed. The average length of hospital stay was (4.53±0.52) days (4-5 days). All patients were followed up for 7-56 months [median (30±15.12) months] with no recurrence of symptoms observed. Conclusions: The second branchial cleft cyst type Ⅳ in children is characterized by prominent pharyngeal cystic mass, with snoring as a predominant initial symptom, MRI provides excellent diagnostic value. The two-person, third-hand endoscopic transoral approach for cyst excision is feasible, safe, and offers the benefits of minimal invasiveness and reduced hospitalization time.

Spontaneous space closure after extraction of young first permanent molar. Retrospective cohort study.

Early compromised first-permanent-molar (FPM) extraction can adversely affect occlusion. However, the current literature does not provide sufficient support for definitive early extraction outcome. This cohort study aimed to evaluate the pattern of post-FPM extraction spontaneous space closure and its pre-extraction indicators. Patients of 7-13 years, with compromised FPM at three-tertiary-centers between 2015 and 2019 were retrospectively screened. Pre-extraction indicators were evaluated (extraction location, direction of the second permanent molar (SPM) long-axis, and SPM Demirjian development stage). Spontaneous space closure pattern was evaluated clinically and radiographically using the American Board of Orthodontics (ABO) grading system. In total, 112 FPMs (73-patients) were identified and five (4.5%) of the extraction sites showed favorable combined-ABO-scores. Distal direction of the SPM long-axis in the maxillary arch significantly decreased the relative risk (RR) of having a SPM rotation/alignment ABO score-1 (P = 0.002; RR = 0.64). For the mandibular arch, Demirjian stage D and E significantly decreased the RR of having ABO score-1 for spacing between the SPMs and second premolars (P = 0.029; RR:0.57, P = 0.004; RR:0.53, respectively) and vertical dimension (P = 0.02; RR = 0.53). The direction of the SPM long-axis and its developmental stage are key indicators of the favorable outcome pattern of spontaneous space closure after FPM early extraction.

Intravenous Bolus Injection of Fentanyl Triggers an Immediate Central and Upper Airway Obstructive Apnea via Activating Vagal Sensory Afferents.

Intravenous bolus (IVb) injection of fentanyl induces an immediate apnea, but the characteristics of the apnea and relevant mechanism remain unclear. Here, we tested whether IVb injection of fentanyl induced an immediate central and upper airway obstructive apnea associated with chest wall rigidity via activating vagal C-fibers (VCFs) and vagal afferent opioid receptors (ORs). Cardiorespiratory and electromyography of external and internal intercostal, thyroarytenoid and superior pharyngeal constrictor muscles (EMGEI, EMGII, EMGTA and EMGSPC) responses to IVb injection of fentanyl were recorded in anesthetized and spontaneously breathing rats with or without bilateral peri-vagal capsaicin treatment or intra-vagal microinjection of naloxone. Immunohistochemical approach was employed to define the presence of opioid mu-receptor (MOR) expression in vagal C-neurons and a patch clamp technique utilized to determine the evoked current responses of vagal C-neurons to fentanyl in vitro. Fentanyl induced an immediate apnea and subsequent respiratory depression. The apnea was characterized by cessation of EMGEI activity and augmentation of tonic discharges of EMGII, EMGTA, and EMGSPC, i.e., central expiratory apnea, laryngeal closure and pharyngeal constriction/collapse accompanied with chest wall rigidity. The apneic response was abolished by blockade of VCF signal conduction and largely attenuated by antagonism of vagal afferent ORs. The latter significantly alleviated the initial (within 5 min post injection), but not the later, respiratory depression. Vagal C-neurons expressed MORs and were activated by fentanyl. We conclude that IVb injection of fentanyl causes a VCF- and vagal afferent OR-mediated immediate central apnea, upper airway obstruction and chest wall rigidity.

Comparative Evaluation of Surgical Difficulty of Impacted Maxillary and Mandibular Third Molars: An Observational Study.

Introduction Extraction of the third molar is the surgical intervention most frequently performed by dental professionals. Notwithstanding a meticulously designed surgical strategy, complications may arise during extraction of the lower third molars. The primary objective of this study was to evaluate and compare the surgical difficulties encountered when managing impacted maxillary and mandibular third molars. The secondary objective was identifying the predictors of surgical difficulty in extracting the third molars from both arches. Materials and methods This study included 30 systemically healthy patients requiring upper and lower third molar extractions on the same side. The Pederson index was used to assess surgical difficulty in such patients on pre-treatment orthopantomograms. The time interval between upper and lower extraction was one week for all patients, and all extractions were performed by an experienced oral and maxillofacial surgeon. An independent t-test was performed to determine the significance of the differences between group variables. Predictors of surgical difficulty, such as sex, type of impaction, duration of surgical procedure, type of surgical procedure, fused roots, and root curvature,were assessed using multivariate analysis. Results The mean patient age was 29.93 ± 2.81 years. The mean mouth opening was 41.25 ± 3.5 mm. Chi-square test results revealed no significant differences between the maxillary and mandibular groups across all variables (p > 0.05). The independent t-test results revealed significant differences between the maxillary and mandibular groups in procedure duration (p < 0.05). The duration of the procedure was significantly longer in the mandibular group (44.13 ± 15.20 minutes) than in the maxillary group (33.33 ± 13.96 minutes). Root curvature, duration of the surgical procedure, type of surgical technique employed, and patient sex were all identified as significant predictors. Conclusion The surgical difficulty for impacted third molars was similar in both arches. The duration of the surgical procedure was longer in the mandibular arch.

Anchorage loss of the posterior teeth under different extraction patterns in maxillary and mandibular arches using clear aligner: a finite element study

BackgroundExtracting the premolars is an effective strategy for patients with bimaxillary dentoalveolar protrusion. Clear aligners (CAs) close the extraction spaces through shortening the length of aligners. The contraction force generated by the terminal of aligners makes the posterior teeth tip mesially, which is known as the roller coaster effect. This phenomenon is even worse in the 2nd premolar extraction cases. Posterior anchorage preparation is commonly used to protect the angulation of molars, taking the form of presetting distal tipping value. However, the distal tipping design aggravates the anchorage loss of anterior teeth simultaneously. This study aimed to explore the different anchorage loss of the posterior teeth when the 1st or 2nd premolars were extracted using CAs, respectively in maxillary and mandibular arches, further providing guidance for anchorage preparation design in clinical practice.MethodsTwo bimaxillary finite element models with different extraction patterns were established to simulate the anterior en-masse retraction process of the CAs. In Model 1, the maxillary and mandibular 1st premolars were extracted, while in Model 2, the 2nd premolars were extracted. Finite element analysis methods were utilized to analyze the tipping angle of the anterior and posterior teeth.ResultsCompared between two models, the anterior teeth exhibited a greater lingual inclination tendency and the posterior teeth exhibited a slighter mesial tipping tendency in Model 1 regarding individual tooth. The closer to the extraction spaces, the greater the tip, and the distal tipping tendency of the 1st premolars was more evident than the mesial tipping tendency of the 1st molars in Model 2. Compared between the maxillary and mandibular arches, the mesial tipping tendency of individual posterior tooth was more evident in the maxilla. In addition, the highest hydrostatic stress of the periodontal ligaments was concentrated on the cervical and apical parts directly adjacent to the extraction spaces, and it exhibited relatively uniform distribution in Model 1.ConclusionsThe individual posterior tooth showed the same mesial tipping direction but to different degree when the 1st or the 2nd premolars were extracted during clear aligner treatment. Presetting anchorage preparation design for the posterior teeth is essential to alleviate the roller coaster effect, especially in the 2nd premolar extraction cases. Furthermore, larger anchorage preparation value should be proposed for the maxillary posterior teeth.

The Prevalence of Partial Edentulism and Associated Factors: A Cross-Sectional Study

Objective: The current study aimed to determine the prevalence of partial edentulism according to Kennedy’s classification and its association to arch, age and gender. Methods: Data were collected from 358 patients aged 18 to 80 years. Selected patients were grouped according to gender and age (&lt;45, =&gt;45). Intra oral examination for each patient was done. The pattern of partial edentulism according to Kennedy’s classification was determined. Statistical analysis was done using the SPSS V26 statistical program. Chi-square test was used to test for differences in frequency at p-value&lt;0.05. Results and Conclusion: The rate of class III pattern in maxillary arch was significantly higher than that of mandibular arch. Class I pattern in mandibular arch was significantly higher than that of maxillary arch (25.1% vs 14%, P=0.001). No differences in frequency were found between class II and IV pattern and affected arch. Class IV was the least frequent in both dental arches. Frequency of class I and class II partial edentulism increased with age, while class III was more frequent at young age. Class IV pattern was more frequent among males than females.

Deep-time origin of tympanic hearing in crown reptiles.

The invasion of terrestrial ecosystems by tetrapods (c. 375 million years [Ma]) represents one of the major evolutionary transitions in the history of life on Earth. The success of tetrapods on land is linked to evolutionary novelties. Among these, the evolution of a tympanic ear contributed to mitigating the problem of an impedance mismatch between the air and the fluid embedding sound-detecting hair cells in the inner ear.1,2,3 Pioneering studies advocated that similarities in the tympanic ear of tetrapods could only result from a single origin of this structure in the group,4,5 an idea later challenged by paleontological and developmental data.4,6,7,8 Current evidence suggests that this sensory structure evolved independently in amphibians, mammals, and reptiles,1,6 but it remains uncertain how many times tympanic hearing originated in crown reptiles.9,10 We combine developmental information with paleontological data to evaluate the evolution of the tympanic ear in reptiles from two complementary perspectives. Phylogenetically informed ancestral reconstruction analyses of a taxonomically broad sample of early reptiles point to the presence of a tympanic membrane as the ancestral condition of the crown group. Consistently, comparative analyses using embryos of lizards and crocodylians reveal similarities, including the formation of the tympanic membrane within the second pharyngeal arch, which has been previously reported for birds. Therefore, both our developmental and paleontological data suggest a single origin for the tympanic middle ear in the group, challenging the current paradigm of multiple acquisitions of tympanic hearing in living reptiles.

Dental arch shape in twins: A morphometric study of genetic influences

The objective of this study was to assess the relative contribution of genes to shape variation in the permanent dental arches in individuals of Western European descent. The dental casts from 64 monozygotic and 38 dizygotic twins, housed in the Adelaide Dental School's twin record collection, Australia, were assessed. The subjects were of Western European descent, with a mean age of 19.4 ± 5.4 years. Dental casts were scanned using a 3-dimensional scanner (3Shape E4, 3Shape, Copenhagen, Denmark), and landmarks were placed on incisal edges and cusp tips of canines, premolars, and molars. Procrustes superimposition and principal components analysis were applied to examine shape variation. Two-block partial least-squares analysis was used to assess shape covariation between arches. Structural equation modeling was utilized to decompose observed shape variation into genetic and environmental components using the normal assumptions of the twin model. The first 3 principal components (PCs) of the maxillary and mandibular arch were meaningful, accounting for 53% and 50% of the variation in shape space, respectively. The PCs represented shape variability as follows: PC1 - arch depth-width ratio, PC2 - arch taper, canine position (and first premolar rotation for the mandibular arch), and PC3 - incisor displacement and rotation. Genetic modeling indicated that a model incorporating additive genetic and unique environmental factors optimally explained the observed variation for all meaningful PCs. Within shape space, most of the variation in maxillary and mandibular arches exhibited moderate to high heritability (h2= 0.61-0.74). Maxillary and mandibular dental arches had strong and significant shape covariation, with high heritability in their reciprocal influences on shape (h2= 0.72-0.74; rpls coefficient= 0.87; P<0.05). In this cohort, dental arch shape variation was predominantly influenced by genetic factors. High covariation and heritability were observed between the maxillary and mandibular dental arches. This information may help inform decisions around orthodontic intervention.

Tooth sensitivity in different arches post in-office dental bleaching: A multicenter randomized controlled trial

ObjectiveTo compare the risk and intensity of tooth sensitivity (TS) and gingival irritation (GI), as well as bleaching efficacy (BE) in the maxillary and mandibular arches after in-office dental bleaching. Materials and Methods90 participants were randomly into two groups according to the arch (maxillary or mandibular) in which the patient will first receive a 35 % hydrogen peroxide gel (2 sessions; 1 × 30 min; 1 week apart). TS and GI were recorded immediately after, up to 1 h, 24 h and 48 h after bleaching, using the 0–10 Visual Analogue Scale (VAS). BE was assessed before bleaching and 30 days after the end of the treatment (shade guide units [ΔSGU], CIELab [ΔEab], CIEDE2000 [ΔE00], and Whiteness Index for Dentistry [WID]). TS and GI were compared using McNemar's and paired t-test. BE were compared with Wilcoxon Signed Rank Test (ΔSGU) and paired t-test (ΔEab, ΔE00, and WID) (α = 0.05). ResultsThe risk and the intensity of TS was statistically higher for the mandibular arch (p < 0.003). The risk and intensity of GI did not differ between arches (p > 0.38). Both arches demonstrated significant BE (ΔSGU, ΔEab, ΔE00 and WID), without differences between them (p > 0.08). ConclusionsIn-office dental bleaching induces higher risk and the intensity of TS in the mandibular arch when compared to maxillary arch, without significant differences in gingival irritation, or bleaching efficacy. Clinical RelevanceMost patients experience tooth sensitivity regardless of the dental arch involved. However, when performing in-office dental bleaching, clinicians should consider that the mandibular arch is more likely to experience greater sensitivity compared to the maxillary arch.

Gastrostomy tube (g-tube) placement timing and clinical outcomes in patients with locally advanced squamous cell carcinoma of the head and neck (HNSCC) receiving definitive chemoradiation.

37 Background: Patients with HNSCC who undergo definitive chemoradiation (dCRT) frequently require nutritional support via G-tubes; despite this, the factors associated with the timing of G-tube placement remain poorly understood. Methods: We performed a retrospective analysis of patients with HNSCC who received dCRT and required G-tube placement between 01/2018 – 01/2024. We segregated G-tube timing into two groups as determined by the intent of the treating clinician: “prophylactic” placement (ordered in anticipation of dCRT start) or “reactive” placement (ordered in response to weight loss or other adverse clinical indicators). We then evaluated associated clinical variables (patient, disease, treatment) and outcomes (weight loss, G-tube duration, healthcare utilization). Differences across G-tube groups were assessed using t-tests or Wilcoxon Rank Sum tests for continuous measures and Fisher’s exact tests or logistic regression for binary variables. Results: We identified 86 patients; 59 (69%) prophylactic and 27 (31%) reactive G-tubes were placed. At baseline, patients had a mean age of 63, BMI of 28 kg/m 2 , and Charlson Comorbidity Index of 4. Patients were 12% non-White, 2% non-English speaking, and 10% unhoused; 27% had a non-metropolitan address, 67% had public insurance, 31% were smokers and 26% had a history of alcohol dependence. The most common site was the oropharynx (66%; 75% HPV+). Across HNSCC types, 38% had stage IV disease and 60% had preexisting dysphagia/odynophagia. Most received weekly (83%) cisplatin (84%) and bilateral (95%) radiation (RT). We collected RT dose data (parotids, esophagus, pharyngeal constrictors) and found no association between RT dose and G-tube group. Patients with prophylactic G-tubes were significantly more likely to have preexisting odynophagia/dysphagia (69% vs 41%, p = 0.017). Compared to the prophylactic group, reactive G-tube placement occurred more often among patients living in non-metropolitan settings (44% vs 19%, p = 0.018) and was associated with a trend towards a higher mean percent weight loss (12% vs 10%; p = 0.128) and cachexia (per int’l criteria; 89% vs 74%, p = 0.159). We observed no difference in the median G-tube duration or in the rate of persistent G-tube use at last follow-up or death. Notably, we found that patients with reactive G-tubes were hospitalized more frequently (74% vs 36%, p = 0.001) and had a longer median length of stay (LOS; 6 vs 0 days, p = 0.001); these findings remained statistically significant when controlling for other factors (OR 3.76 [95% CI: 1.20-12.65]; p = 0.026). Conclusions: We found that reactive G-tubes were associated with increased hospitalization and LOS, suggesting that select patients may benefit from earlier G-tube placement.

Evidence for the Presence of the Fifth Pharyngeal Arch During the Chick Development

Evidence for the Presence of the Fifth Pharyngeal Arch During the Chick Development