Movement Of Mandible Research Articles

TMJ Changes Before and After Implant of Posterior Partial Edentulous Patients Free of TMD Signs Under the Scope of Cadiax Compact II Device

Introduction: Assessing occlusion and TMJ discrepancies presents a persistent challenge for health professionals due to the complexity of the conditions that include accurate: diagnostic methods, treatment, associated comorbidities. Researches are being delved in this field. Cadiax Compact II is one of the technological innovations that can analyze and provide a simple and minimally invasive way, enabling early preventive action and treatment with a long-term impact on the good functioning of the masticatory system. Objectives: The objective of this research is to evaluate TMJ changes among dental implant patients. A comparison of the implant impact on posterior partial edentulous patient is taken place by the aid of Cadiax Compact II. Cadiax Compact II investigates in parameters such as Immediate Side-Shift (ISS), Sagittal Condylar Guidance (SCG), and Transverse Condylar Guidance (TCG) that are derived from mandible movements (opening, closing, protrusion, retrusion, and lateral excursion). The objective is to evaluate the changes in TMJ before and after implants in partial edentulous (posterior teeth) patients. Methods: Condylography using Cadiax Compatct II device (Gamma Dental, Klosterneuburg, Austria) was conducted on 40 patients. R statistical software was used to perform statistical analysis to perform a cephalometric analysis. Results: Age groups covered are (<40), (40-49), (50-59), and (≥ 60). Alpha value, level of uncertainty, was chosen to be 0.05. There is no statistical evidence in the change of ISS, SCG, and TCG before and after implant in the age groups (<40) and (40-49); however, there is a significant statistical change in age groups (50-59) and (≥ 60) with p-value <0.05. Conclusions: This research extended from December 2022 to March 2024 to cover time changes on mandible bone structure. The research outcomes revealed that implant has pronounced impact on TMJ articulation during opening, protrusion, retrusion, and lateral movements through (ISS, SCG, and TCG or so-called Bennet Angle) variables. Evidence-based statical tests with p-value < 0.05 showed that (ISS, SCG, TCG, and Bennet Angle) variables changed in age groups (50-59) and (≥ 60) from abnormal ranges to the normal ranges after implant. However, no statistical evidence was approved of the implant impact on age groups (<40) and (40-49). Though these age groups have normal ranges before and after implants.

A novel electro-mechanical chewing system for food oral processing research: A comprehensive design approach

This paper presents a comprehensive design approach for an electro-mechanical system for food oral processing research. The bespoke design and prototype of the proposed device is a standalone and compact table top model and can be operated using a customized software interface. The design considered a bi-directional chewing motion to enable nearly similar mandible movement pattern as in human. Food texture profile can be estimated using a load cell with capacity up to 300 N. This design included a section of real shaped teeth assembly consisting of three teeth; and a controlled supply line for multi-point saliva injections. The device is fitted with easily replaceable sensors for in situ measurements of conductivity, pH, and temperature. Operating volume of the device can be kept in equivalence with the volume of human oral and nasal space. The device chamber can be hermetically sealed and temperature controlled. A duct system is fitted to connect the device with external analytical systems, such as electronic nose, for measuring gaseous substance release during experimentation. The system also enables easy retrieval of the processed sample so as to use the masticated samples and processed saliva for subsequent analysis by analytical instruments, such as electronic tongue, to identify released soluble compounds and taste profiles. Moreover, the design emphasized on easy cleaning and maintainability. Based on the proposed design, two working prototypes are developed. It is envisaged that the device will be a novel contribution to the progress in the field of food science, new product development, training to future professionals, and strengthening industry-academic collaborations in foreseeable future.

Effectiveness of Rehabilitation for Disk Displacement of the Temporomandibular Joint—A Cross-Sectional Study

(1) Background: Dislocations of articular disk can occur as a result of parafunctions in the Temporo Mandibular Joint (TMJ), which limits the opening of the mandible and other movements. The aim of this study was to evaluate the effectiveness of rehabilitation in patients with disk displacement of the TMJ. A total of 327 subjects with Temporo Mandibular Disorders underwent stomathognatic physiotherapy. (2) Methods: Based on the results obtained by a manual functional analysis, 35 patients who were identified with articular disk locking (disk displacement without reduction) were included in the study. The study group (N = 35) was subjected to passive repositioning of the articular disk, reposition splints, and physiotherapy. The patient’s TMJs were then examined before the therapy, immediately after the therapy, and during the follow-up visit 3–6 weeks after the therapy. The Diagnostic Criteria for the Most Common Intra-articular Temporomandibular Disorders was used to evaluate the effects of rehabilitation on the patients’ range of motions and the Numeric Pain Rating Scale (NPRS). For the statistical analysis, Pearson’s r correlation coefficient test and Wilcoxon signed-rank test were used. (3) Results: The results showed a significant improvement in the range of motion of the mandible movements. The level of improvement was dependent on the time from the incident until undergoing rehabilitation. (4) Conclusions: The stomatognathic physiotherapy applied increased the range of motion of the mandible and reduced pain levels to the expected range.

The Role of Digital Facebow for CAD/CAM Implant-Supported Crowns Workflow.

Recent advancements in digital technologies have transformed clinical workflows in dentistry, ensuring precise restorations. Custom-made crowns and fixed partial dentures (FPDs) now rely on virtual articulation. The digital facebow provides individualized data for CAD settings, streamlining the fabrication via digital workflow. For the purpose of demonstrating the differences observed during fabrication, we present a case report involving a 68-year-old patient seeking a replacement for missing teeth 24, 25, 26, and 27. The treatment plan involved the fabrication of an implant-supported FPD using monolithic zirconia (ZrO2). However, technical hurdles emerged during the planning phase, primarily due to spatial limitations posing a risk of mechanical failure over time. Consequently, we pivoted approach towards a porcelain fused to metal (PFM) FPD. For the PFM FPD, individual values from the digital facebow adjusted both virtual and conventional articulators. For comparison, two ZrO2 FPDs were milled-individual settings and average settings. All restorations underwent assessment for occlusion in maximal intercuspal position and eccentric mandible movements. In conclusion, the case report showed that individualized PFM FPD required minimal adjustments compared to milled ZrO2 restorations, whether using individual or average values. Utilizing individual values from the digital facebow reduced operator working time and minimized the intraoral adjustments.

The dual function of prokinesis in the feeding and locomotor systems of parrots.

Prokinesis, a mode of avian cranial kinesis involving motion between the neurocranium and upper beak, has long been investigated in biomechanical analyses of avian feeding and drinking. However, the modern avian beak is also used for non-feeding functions. Here, we investigate the dual function of prokinesis in the feeding and locomotor systems of the rosy-faced lovebird (Agapornis roseicollis). Lovebirds and other parrots utilize their beak both during feeding and as a third limb during vertical climbing. Thus, we experimentally measured both force-generating potential and movement of the rosy-faced lovebird mandible and maxilla (via prokinetic flexion of the craniofacial hinge) during tripedal climbing and mandibular/maxillary adduction. We found that whereas the maxilla is primarily responsible for generating force during locomotion, the mandible is primarily responsible for generating force during forceful jaw adduction, hinting at a remarkable capacity to alter prokinetic function with differing neuromuscular control. The ability of the prokinetic apparatus to perform functions with competing optimality criteria via modulation of motor control illustrates the functional plasticity of the avian cranial kinesis and sheds new light on the adaptive significance of cranial mobility.

Designing customized temporomandibular fossa prosthesis based on envelope surface of condyle movement: validation via in silico musculoskeletal simulation.

Objective: This study presents an innovative articular fossa prosthesis generated by the envelope surface of condyle movement, and compares its mandible movements, muscle activities, and joint reaction forces with two temporomandibular joint (TMJ) prostheses using multibody musculoskeletal simulation. Methods: A healthy 23-year-old female was recruited for this study. Cone-beam computed tomographic (CBCT) was performed to reconstruct the mandibular bone geometry. A customized TMJ fossa prosthesis was designed based on the subject-specific envelope surface of condyle movement (ESCM). Mandibular kinematics and jaw-closing muscle electromyography (EMG) were simultaneously recorded during maximum jaw opening-closing movements. To validate our prosthesis design, a mandibular musculoskeletal model was established using flexible multibody dynamics and the obtained kinematics and EMG data. The Biomet fossa prosthesis and the ellipsoidal fossa prosthesis designed by imitating the lower limb prostheses were used for comparison. Simulations were performed to analyze the effects of different fossa prostheses on jaw opening-closing motions, mandibular muscle activation, and contact forces. Results: The maximum opening displacement for the envelope-based fossa prosthesis was greater than those for Biomet and ellipsoidal prostheses (36mm, 35mm, and 33mm, respectively). The mandibular musculoskeletal model with ellipsoidal prosthesis led to dislocation near maximal jaw opening. Compared to Biomet, the envelope-based fossa reduced the digastric and lateral pterygoid activation at maximal jaw opening. It also reduced the maximal resistance to condylar sliding on the intact side by 63.2N. Conclusion: A customized TMJ fossa prosthesis was successfully developed using the ESCM concept. Our study of musculoskeletal multibody modeling has highlighted its advantages and potential. The artificial fossa design successfully achieved a wider condylar range of motion. It also reduced the activation of jaw opening muscles on the affected side and resistance on the intact side. This study showed that an ESCM-based approach may be useful for optimizing TMJ fossa prostheses design.

Three-dimensional kinematics of leaf-cutter ant mandibles: not all dicondylic joints are simple hinges.

Insects use their mandibles for a variety of tasks, including food processing, material transport, nest building, brood care, and fighting. Despite this functional diversity, mandible motion is typically thought to be constrained to rotation about a single fixed axis. Here, we conduct a direct quantitative test of this 'hinge joint hypothesis' in a species that uses its mandibles for a wide range of tasks: Atta vollenweideri leaf-cutter ants. Mandible movements from live restrained ants were reconstructed in three dimensions using a multi-camera rig. Rigid body kinematic analyses revealed strong evidence that mandible movement occupies a kinematic space that requires more than one rotational degree of freedom: at large opening angles, mandible motion is dominated by yaw. But at small opening angles, mandibles both yaw and pitch. The combination of yaw and pitch allows mandibles to 'criss-cross': either mandible can be on top when mandibles are closed. We observed criss-crossing in freely cutting ants, suggesting that it is functionally important. Combined with recent reports on the diversity of joint articulations in other insects, our results show that insect mandible kinematics are more diverse than traditionally assumed, and thus worthy of further detailed investigation. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

KED gene expression in early response to wounding stress in tomato plants.

The wounding-responsive KED gene, named for its coding for a lysine (K), glutamic acid (E), and aspartic acid (D)-rich protein, is widely present among land plants. However, little is known about its regulation or function. In this study, we found that transcription of the tomato (Solanum lycopersicum) KED gene, SlKED, was rapidly and transiently elevated by wounding or ethephon treatment. Compared to the wild-type plants, the CRISPR/Cas9-mediated SlKED knockout plants did not exhibit altered expression patterns for genes involved in hormone biosynthesis or stress signaling, suggesting a lack of pleiotropic effect on other stress-responsive genes. Conversely, jasmonic acid did not appear to directly regulate SlKED expression. Wounded leaves of the KED-lacking plants exhibited higher binding of Evans blue dye than the wild-type, indicating a possible role for KED in healing damaged tissues. The SlKED knockout plants showed a similar dietary effect as the wild-type on the larval growth of tobacco hornworm. But a higher frequency of larval mandible (mouth) movement was recorded during the first 2 minutes of feeding on the wounded KED-lacking SlKED knockout plants than on the wounded KED-producing wild-type plants, probably reflecting an initial differential response by the feeding larvae to the SlKED knockout plants. Our findings suggest that SlKED may be an ethylene-mediated early responder to mechanical stress in tomato, acting downstream of the wound stress response pathways. Although its possible involvement in response to other biotic and abiotic stresses is still unclear, we propose that SlKED may play a role in plant's rapid, short-term, early wounding responses, such as in cellular damage healing.

Clinical-statistical study on the use of articulators in orthodontic practice

Dental-maxillary anomalies are accompanied by changes in the interbasal maxillary ratio in all reference planes, with influences on the functionality of articular structures. These joint changes not detected in time and not included in the treatment plan may worsen while wearing fixed appliances, as orthodontic treatment changes the cranio-mandibular position and causes cranio-mandibular reshaping. The articulator is an instrument that reproduces more or less all mandible movements. TMJ characteristics of skeletal dento-maxillary anomalies, especially class II sagittal pattern mainly reflected in condylar position rather than morphology. TMJ of different vertical patterns differed more in joint spaces, position of condyle and glenoid fossa than in morphologic measurements. Vertical position of glenoid fossa and proportion of posterior condyle increased gradually from hypodivergent to hyperdivergent. Highest glenoid fossa position, maximum ratio of posterior positioned condyle, smallest joint spaces, shallowest glenoid fossa depth, and narrowest condylar long axis diameter were found in skeletal class. The patients with high angle have considerable joint instable factors, and we should especially pay attention when orthodontic treatment is carried out on them. The condyle-fossa position and morphology differ with various vertical facial patterns in individuals with skeletal Class II mandibular retrognathism. These differences could be considered during temporo-mandibular diagnosis and orthodontic treatment

Evaluation of Mandibular Movements in Patients with Bell's Palsy Using Kinematic Variables.

Since the function of muscles, and subsequently the mandibular joint, is affected in patients with Bell's palsy, therefore, the evaluation of facial muscles and mandibular function in these patients can be effective in diagnosis, prevention, and treatment planning. The present study aimed to evaluate the degree of displacement and range of motion (ROM) of the mandible and the ability of the facial symmetrical muscles of patients with Bell's palsy. This was a quasi-experimental comparative study. The variables evaluated were mandibular movement in a vertical direction and side-to-side displacement. Ten patients with Bell's palsy and 10 healthy eligible volunteers participated in the present study. Three mobile video cameras (to record jaw movements), 9 color markers, Kinovea software, House-Brackmann index, Toledo protocol, and a specialized patient questionnaire were used. Descriptive and inferential statistics were used for data analysis, the Kolmogorov-Smirnov test was used to investigate the normality of data distribution, and independent samples the t test and paired samples t test were used to compare means. The maximum lateral on the sound side was 12.40 and 4.49 mm during lateral movements of the patients' mandible, while this value was between 12.30 and 3 mm on the involved side. There is a difference between the affected side and the nonaffected side in terms of the mean lateral movements of the patients' mandible. However, this difference in the mean ROM on both sides is not statistically significant. The maximum mouth opening in healthy individuals during mandibular movements was between 40 and 60 mm, while this value was between 25 and 50 mm in the patients with Bell's palsy. This study shows a significant difference (P = 0.007) between patients and healthy individuals in terms of the mean of maximum mouth opening ( P < 0.05). The results of this study showed that the ROM of temporomandibular joint (TMJ) of the patient is the same as that of normal subjects, but the side-to-side motion is more than normal which should be considered in rehabilitation treatments. The present study emphasizes the need to implement a mandibular kinematic evaluation protocol in patients with bell's palsy to prevent damage to the TMJ in the long term.

Benefits and Limitations of Computer-Assisted Surgery in Maxillofacial Surgery

Computer-assisted surgery (CAS) has revolutionised surgical procedures in both medicine and dentistry. This review explores the benefits and limitations of CAS in maxillofacial surgery. Virtual surgical planning allows for a clear declaration of surgical intentions, avoiding conflicts between resection and reconstruction teams, and enabling communication of preferences and uncertainties. CAD-CAM software facilitates virtual surgery and generates templates and cutting guides for precise implementation in the operating room. CAS has had a significant impact on dental implant placement, enabling accurate positioning and improved outcomes. It also aids in skull base surgery and the removal of foreign bodies. Navigation systems provide real-time tracking and visualisation, ensuring accuracy and safety. However, because of the mandible's movement, there are restrictions, especially in mandibular surgery. Despite these challenges, CAS offers numerous advantages, including increased precision, reduced anaesthesia time, and improved efficiency

Condylographic evaluation of propulsive and Bennett angles in patients with temporomandibular disorders

Introduction. Mandibular kinetics is composed of a series of complex movements regarding opening and closing and latero-lateral movements. The procedure for registration of this trajectory is condylography. This procedure represents a diagnostic method for monitoring and registering the movements of the mandibular condyles. The analysis starts from the most distal position of the condyle to the maximum propulsive point and latero-lateral maximum extensions. The aim of this examination is to compare the trajectory of movement of the mandibular condyle in patients with symptoms of TMD, in the acute phase and the trajectory after the treatment and corrections of intermaxillary relations. Materials and methods. The examination was carried out in 20 (10 men and 10 women) patients of PHO Denta Estetika Team Skopje. The patients were complaining about pain, limitation of movements and crepitations in the temporomandibular joint as well as difficult mastication. Condylographic measurements were made with the Kavo Arcus Digma digital condylograph. The registration of the movements was done in two sessions, before and after the treatment. Results. There was no statistically significant difference in temporomandibular condyle movement angles before and after the treatment in patients with TMD. There was a statistically significant difference in the value of Bennett?s angle. Easier and more accurate movements of mandible were noticed in the patients after the treatment.

Describing the Acoustic and Vocal Production Characteristics of the Irrintzi: Feasibility of Its Use for the Treatment of Voice Disorders.

The aims of this study were to analyze and characterize the irrintzi (a folkloric shout emitted in a single breath used by the Basque people) acoustically and to describe the mechanism by which it is emitted. Thirty-six sound samples of 12 female volunteers were analyzed. Acoustic analysis included primarily fundamental frequency (f o), spectral analysis in the time domain with a narrowband filter, and the use of linear predictive coding (LPC). Laryngeal and pharyngeal movements while emitting an irrintzi were studied by fiberoptic nasal endoscopy. Postural and mandible movements were observed and video recorded. Movements of the larynx and the vocal tract were also studied by lateral pharyngo-laryngeal radioscopy. The central part of an irrintzi spectrogram contains a peculiar, repeated M-shaped motif unseen in the spectrogram of any other human vocal emission, and intensity was over 90 dB SPL in all cases. f o was very high (1487 Hz) especially at the end of the irrintzi. Fiberoptic nasal endoscopy consistently revealed considerable elevation of the glottis, with the larynx swinging forward and retraction of the ventricular bands. Lateral radioscopy showed a very high larynx and a high tongue dorsum. The irrintzi is a sound emitted in a single breath and characterized by its shrillness and loudness, qualities that make it audible in noisy environments and over large distances and the vocal technique observed when it is produced can be explained by the Estill voice model (Steinhauer et al., 2017). The use of this technique may help in the treatment of voice disorders and improve efficiency in singers, teachers, actors, and people who use their voice at high volume or at high frequency. https://doi.org/10.23641/asha.20779405.

Repeated Intra-Articular Administration of Platelet-Rich Plasma (PRP) in Temporomandibular Disorders: A Clinical Case Series.

Background: Temporomandibular joint disorders (TMDs) are manifested, inter alia, by pain and limited scope of the mandibular abduction. Among the treatment strategies for these ailments, intra-articular injections of autologous blood preparations, including platelet-rich plasma (PRP), are administered. This prospective case series was aimed at assessing the effectiveness of repeated platelet-rich plasma (PRP) administration to the TMJ cavities in terms of reducing articular pain and increasing the mobility of the mandible. Material and methods: 40 consecutive patients diagnosed with TMJ pain qualified for the case series. The entire treatment program consisted of five PRP administrations and a summary appointment. Regression was analyzed for (1) intensity of spontaneous pain; (2) effectiveness of spontaneous pain relief; (3) mastication efficiency values; (4) painless mandibular abduction; (5) maximum mouth opening. The correlations between the abovementioned variable series were analyzed. Results: The mean spontaneous pain decreased consistently with successive PRP administrations in line with the regression model: −0.4x + 4.2 (R2 = 0.98). Articular pain improvement was reported in 71% of joints treated. Improvement in chewing quality at the end of the entire injection cycle was found in 63% of patients. The equations for the linear regression models for painless mandibular abduction (five applications of PRP) and maximum mouth opening (the first four applications of PRP) were x + 34 (R2 = 0.89) and 0.6x + 43.6 (R2 = 0.96), respectively. Improvement in these domains was found in 78% and 53% of patients, respectively. The strongest correlations were found between pain and chewing efficiency (−0.95), pain and painless mandible abduction (−0.96), and painless mandibular abduction and mastication efficiency (0.94). Conclusion: PRP injections into TMJ cavities should be considered as a low invasive, highly accessible form of treatment for various TMDs causing pain and mandible movement limitation.

Three-dimensional movement of the beak during seed processing in domestic canaries.

Many songbird species rely on seeds as a primary food source and the process of picking up, positioning, cracking, dehusking and swallowing seeds is one of the most sophisticated tasks of the beak. Still, we lack understanding about how granivorous songbirds move their beak during the different phases of seed processing. In this study, we used multi-view high-speed imaging to analyze the 3D movement of the beak in feeding domestic canaries. Our analysis focused on the correlation of the upper and lower beak, the frequency of mandibulation and the direction of mandible movement in 3D space. We show that the correlation of maxilla and mandible movement differs among the phases of seed processing. Furthermore, we found that the beak moves at extremely high frequencies, up to 25 Hz, which resembles previously reported maximal syllable rates in singing canaries. Finally, we report that canaries use specific 3D mandible movements during the different phases of seed processing. Kinematic parameters do not differ between male and female canaries. Our findings provide an important biomechanical basis for better understanding the beak as a functional tool.

Biomechanical comparative analysis of temporomandibular joint, glenoid fossa and head of the condyle of conventional models prothesis with new PEEK design

This article reviews the design of the temporomandibular joint (TMJ) prostheses used for TMJ joint replacement from 2000 to 2020. The TMJ is a complex joint, with distinct anatomical and functional characteristics making it challenging to maintain. Many authors from the early 20th century reported techniques for TMJ reconstruction, with the goal of restoring its shape and ideal function. Many prototypes have been developed in pursuit of an ideal prosthesis that adheres to the principles of biomechanics and biocompatibility, with good long-term performance and lower cost.The TMJ prosthesis is divided in two parts: the glenoid fossa and the mandibular ramus component.These two parts are fixed with metal screws in the glenoid fossa and fixed in the zygomatic arch with 4 or 5 screws. The mandibular part is fixed to the mandible ramus with 8 or 9 titanium screws.In our review, since 2000 to 2020, little has changed to improve the design and allow for natural mandible movement. From 2000 to 2006, 48 TMJ surgeries were performed using UHMWPE with this design. All patients had good results, preserving opening mouth and lateral movements.All the designs are similar in principle. The glenoid fossa, which resembles a box, limiting the rotation and translation movement. It is known that lateral movements are lost in function as the lateral pterygoid muscle is detached.

Jaw tracking integration to the virtual patient: A 4D dynamic approach

This dental technique describes a novel cost-effective workflow for integrating mandible kinematics into a static virtual patient. Computed tomography data are segmented and merged with intraoral surface scans and a target tracking video reproducing the mandible movements. A 4-dimensional dynamic virtual patient is created by using an open-source software program, and all patient-specific parameters can be exported for individualization of a virtual or analog articulator.

The relationship between mandibular advancement, tongue movement, and treatment outcome in obstructive sleep apnea.

To characterize how mandibular advancement enlarges the upper airway via posterior tongue advancement in people with obstructive sleep apnea (OSA) and whether this is associated with mandibular advancement splint (MAS) treatment outcome. One-hundred and one untreated people with OSA underwent a 3T magnetic resonance (MRI) scan. Dynamic mid-sagittal posterior tongue and mandible movements during passive jaw advancement were measured with tagged MRI. Upper airway cross-sectional areas were measured with the mandible in a neutral position and advanced to 70% of maximum advancement. Treatment outcome was determined after a minimum of 9 weeks of therapy. Seventy-one participants completed the study: 33 were responders (AHI<5 or AHI≤10 events/hr with >50% AHI reduction), 11 were partial responders (>50% AHI reduction but AHI>10 events/hr), and 27 nonresponders (AHI reduction<50% and AHI≥10 events/hr). Responders had the greatest naso- and oropharyngeal tongue anterior movement (0.40 ± 0.08 and 0.47 ± 0.13 mm, respectively) and oropharyngeal cross-sectional area enlargement (6.41 ± 2.12%) per millimeter of mandibular advancement. A multivariate model that included tongue movement and percentage of airway enlargement per millimeter of mandibular advancement along with baseline AHI correctly classified 69.2% (5-fold cross-validated 62.5%, n = 39) of participants in response categories when the jaw was advanced in the range that would usually be regarded as sufficient for clinical efficacy (> 4 mm). In comparison, a model using only baseline AHI correctly classified 50.0% of patients (5-fold cross-validated 52.5%, n = 40). Tongue advancement and upper airway enlargement with mandibular advancement in conjunction with baseline AHI improve treatment response categorization to a satisfactory level (69.2%, 5-fold cross-validated 62.5%).

Biomechanical Evaluation and Factorial Analysis of the 3-Dimensional Printing Self-Designed Metallic Reconstruction Plate for Mandibular Segmental Defect

Reconstruction plates are frequently used to treat mandibular segmental defects. The aim of this study is to compare the biomechanical performance of a 3-dimensional-printed self-designed titanium alloy reconstruction plate with that of the traditional reconstruction plate in mandible reconstruction. The analyzed parameters of the self-designed reconstruction plate, including plate length (100mm and 125mm), plate thickness (2.1, 2.4, and 2.7mm), and bone mass (100, 75, and 50%), were also evaluated. An artificial mandible with anatomical geometry was used to develop the self-designed reconstructed plate. Both invitro experiments and finite element simulations were performed for the biomechanical comparison of the self-designed and traditional reconstruction plates. In finite element analysis, 3 major muscle forces of mandible movement were set as the loading condition, and the displacement of the condyle was fixed in all directions as the boundary condition. The biomechanical performances (stresses in the plate and strains in bone) of the self-designed reconstruction plate were superior to those of the traditional plate. Factorial analysis indicated that plate length and thickness had significant effects on decreasing stresses of the plate and mandibular bone. The self-designed reconstruction plate might have a benefit to reduce the stresses/strains in plate itself and surrounding bone.

Investigating Opioid‐induced Respiratory Depression and Analgesia Using Larval Zebrafish

Introduction Opioid drugs produce both analgesia and severe respiratory depression which can be lethal. In 2019, over 50,000 North Americans died of an opioid overdose. Our understanding on how to differentiate between these two effects is limited due to a lack of simple animal models. Therefore, we aim to understand respiratory depression and analgesia by opioids using novel zebrafish models, allowing for drug screening. Using these models, we tested a variety of drugs including serotoninergic agonists, glutamatergic modulators, and calcium channel activators, for their ability to reverse opioid-induced respiratory depression. Methods We have established phenotype-based approaches using in-vivo zebrafish models of respiratory depression and analgesia by fentanyl. To quantify respiratory depression, we measured respiratory activity by quantifying mandible movements in 12-14 day post-fertilization larvae. To quantify analgesia, we measured the escape swimming response to nociceptive stimuli such as formalin or allyl isothiocyanate (AITC) combined with fentanyl to induce analgesia. We then introduced various candidate drugs to measure their effects on respiratory depression and analgesia. Results Respiratory rate was normalized to each fish's baseline (baseline=100%). Zebrafish strains were found to be differentially sensitive to opioids, where Tübingen (TU) fish did not respond to fentanyl (1µM, p=0.4240, n=9) and AB fish showed significant respiratory rate depression (p<0.001, n=11). AB and TU crosses did not show respiratory depression (n=7). In AB zebrafish, a dose-dependent decrease in respiratory rate was observed with 1μM and 3µM fentanyl (p=0.01, n=11 and p<0.001, n=27, respectively). The opioid antagonist naloxone (20µM) and selective antagonist CTAP (4μM) reversed respiratory depression by fentanyl (p<0.001, n=9 and p=0.049, n=11, respectively). Respiratory depression by 1μM fentanyl was reversed by the AMPA receptor positive allosteric modulator CX614 (5μM, p<0.001, n=9) but not the serotoninergic 5-HT4 agonist BIMU8 (10μM, n=21). Calcium channel activators nefiracetam (1µM) and FLP-64176 (1µM) reversed respiratory depression by fentanyl (1µM, p=0.005, n=11 and3µM, p<0.001, n=15, respectively). Formalin (0.075%) and AITC (100µM) significantly increased swimming velocity (p=0.005, n=21 and p<0.001, n=23, respectively), which was reduced by fentanyl (4μM, p<0.001, n=12and 6µM, p=0.004, n=14, respectively). FLP-64176 reversed fentanyl analgesia when administered with formalin (p<0.001, n=10). Discussion: Our models show that respiratory depression and analgesia by opioids can be measured in zebrafish larvae. The strain differences point to a potential genetic protection which we are investigating using quantitative real-time polymerase chain reaction (qPCR). Our novel zebrafish models can be used to investigate the effects of opioids, as well as for drug screening to find ways to treat respiratory depression while preserving analgesia.