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Intoduction: Limited research has explored the mechanical characteristics of recently introduced multilayered monolithic zirconia (MZC) crowns with feather-edge margins design. Moreover, most of the conventional techniques for evaluating the mechanical behavior of brittle dental ceramics rely on destructive tests, making it impossible to precisely evaluate real strength values due to premature crack initiation detection failure. Objectives: The main objective of the study was to assess the load capacity of translucent multilayered monolithic zirconia crowns with feather-edge margin thicknesses of 0.4 mm and 0.5 mm. Additionally, the research introduced a novel non-destructive acoustic emission testing (AET) technique in the laboratory to identify early cracks in dental ceramics. Methods: Forty multilayered zirconia crowns produced using computer-aided design and computer-aided manufacturing (CAD/CAM) technology were evenly divided into two groups, each with distinct feather-edge margin thicknesses: 0.5 mm (group 1) and 0.4 mm (group 2). These crowns were securely cemented onto customized polymethyl methacrylate (PMMA) dies using a universal restorative glass ionomer. Subsequently, the crowns underwent a compressive axial loading test, controlled by an innovative AET crack detection system rooted in the principles of non-destructive laboratory testing. Fractographic analysis was conducted to determine the location of crack or eventual fracture. Results: The proportion of MZCs with a crack was statistically higher than the proportion with a fracture in the whole sample (p<0.001). In addition, the results showed that the crowns in group 1 exhibited higher loading values than those in group 2. The mean loading capacity in group was 911.2 N ± 614.7 N. Two locations of crack and fracture were registered: occlusal and marginal. No statistical association was observed between the two groups for the location of cracks or fractures. Conclusions: The feather-edge crowns with a 0.5 mm margin thickness had a higher loading capacity than those with a 0.4 mm. However, the latter supports loads that exceed occlusal force in the oral cavity suggesting that 0.4 mm feathered edge MZCs may be a valid and less invasive alternative to thicker margins. The novel load-to-fracture AET setup proved effective in detecting early crack initiation, suggesting it as a promising method for assessing the mechanical properties of brittle materials prior to failure, potentially impacting the field of dentistry. However more advanced research is needed to enhance the accuracy of the proposed technique. Clinical implications: The examined MZC demonstrates the ability to withstand occlusal forces in a patient's mouth, offering clinical practitioners the option of embracing minimally invasive dentistry through the use of 0.4 mm feather-edge MZC in their treatment options. Furthermore, the positive results from the innovative acoustic emission testing technique, facilitating early crack detection, indicate a promising future for studying the behavior of brittle materials in dental laboratory testing. [ABSTRACT FROM AUTHOR]

Objective: This systematic review aimed to investigate and examine whether intra‐articular injections of platelet‐rich plasma (PRP) after arthrocentesis are beneficial for the treatment of temporomandibular disorders, when compared to other treatments, such as injections of hyaluronic acid (HA) or saline after arthrocentesis. Methods: An electronic search on PubMed was performed using combinations of the terms 'temporomandibular' and 'platelet rich plasma', to identify studies reported in English and published up until 2017. The initial screening identified 222 records, of which only seven fulfilled the inclusion criteria and were included in this review. Of these studies, three compared injection of PRP after arthrocentesis with the injection of HA after arthrocentesis, while two compared injection of PRP after arthrocentesis with Ringer's lactate after arthrocentesis and one compared injection of PRP after arthrocentesis to sodium chloride. Results: Five of the studies found that PRP injections have led to significant improvements in mandibular range of motion and pain intensity up to 12 months after treatment, while the remaining two studies found similar results for the different treatments. Conclusion: However, a standardized protocol for PRP preparation and application needs to be established. [ABSTRACT FROM AUTHOR]

SUMMARY: Objective: To review the materials and fabrications methods of occlusal splints with their advantages and shortcomings and to clarify the indications for each. Background: Temporomandibular joint disorders (TMDs) encompass a range of conditions affecting the masticatory system. Occlusal splints are currently recognised as a viable option for the management of TMDs when they are adopted in conjunction with additional approaches varying from conservative procedures (counselling, biofeedback, physical therapy, pharmacotherapy) to irreversible and less conservative ones (occlusal adjustments, orthodontics, arthroscopy and surgery). These splints can vary in design, function and material. The components used to fabricate the splints must withstand occlusal forces, be aesthetically pleasing, comfortable and minimally interfering with function and phonetics. Traditional methods for fabricating splints include sprinkle‐on, thermoforming and lost wax techniques. However, with the advancement of CAD/CAM technology, additive (3D printing) and subtractive (milling) manufacturing methods expand the range of possibilities by introducing novel solutions for elaborating splints. Methods: An electronic search was conducted on PubMed using the following keywords: "occlusal splint", "guard and "materials", and "manufacturing." Thirteen in vitro publications were screened and they consisted of four clinical studies, nine reviews (three of them were systematic reviews), and five case reports. Conclusion: The choice of material is crucial for the success of splint therapy. Factors such as biocompatibility, ease of fabrication, adjustability, cost and patient preference should be considered. Newer materials and techniques are emerging because of advancements in material science and manufacturing techniques. However, it should be noted that most of the evidence is based on in vitro studies with different methodologies, limiting their validity in daily practice. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of this in vitro study was to test the influence of the margin design of implant supported monolithic zirconia crowns and test if monolithic zirconia crowns with extra fine finish line thickness cemented on zirconia implant abutments can bare the maximum masticatory forces on molars and hence be used in the posterior region. Methods: Fourteen identical monolithic zirconia crowns cemented on zirconia implant abutments mounted on titanium bases and fixed on implant replicas embedded in PMMA resin were divided into two groups: group I designed with a 0.5 mm CFL (CFL) and group II with a feather-edge finish line (FEFL) of 0.3 mm. All specimens underwent static load until fracture in order to determine the break force. Break forces in N were recorded for each group. Results: The CFL group exhibited slightly higher fracture resistance (1879.14 ± 322.28 N) compared to the feather-edge finish line group (1685.00 ± 362.18 N). However, statistical analysis revealed that the observed difference between the two groups (194.14 ± 183.24; p = 0.310) was not significant. Conclusions: Within the limitations of this study, both monolithic zirconia crowns with 0.5 mm chamfer and 0.3 mm feather edge margins cemented on zirconia implant abutments can be used in the posterior region as their resistance to fracture is similar and surpasses the maximum masticatory force applied on molars. [ABSTRACT FROM AUTHOR]

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The aim of this research is to review the literature for the influence of the thickness and shape of cervicalmargins on the strength of posterior monolithic zirconia crowns. Studies to assess the fracture resistance of monolithic zirconia crowns with different types of cervical margins, published from 2014 to 2020, were searched using the electronic database PubMed and Google Scholar using the following keywords: "monolithic zirconia," "translucent," "shoulderless," and "margin preparation design." Analysis of studies has shown that overall the design of the margin would have a significant effect on the strength of these crowns. Monolithic zirconia crowns with a knife-edge margin have shown a breaking load higher than the maximum chewing force of humans. It would be safe to suggest the utilization of posteriormonolithic zirconia crowns with vertical preparation. As the new translucent monolithic zirconia crowns are recent, further studies would be needed to guide the selection of the appropriate minimum thickness of the knife-edge margin to meet the clinical guidelines for their use. [ABSTRACT FROM AUTHOR]

Objective The purpose of this study was to evaluate the influence of the connector area on the chipping rate of the VM9 veneering ceramic in a 4-unit yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) framework, using a novel sonographic technique. Materials and Methods The framework was designed as a 4-unit fixed dental prostheses (FDP) with two abutment teeth at the first mandibular premolar and second mandibular molar. The cross-sectional area of the connector was 7.5, 8, or 9mm². The prepared teeth were scanned using CAD/CAM technology, and five frameworks were prepared for each design, making a total of 15. The frameworks were divided according to the veneering ceramics: Y-TZP FDPs using Vita VM9 (12 frameworks), and porcelain fused to metal (PFM) FDPs using Vita VM13 (3 frameworks). The specimens were statically loaded until failure. To capture the initiation of the failure within the specimens, a novel sonographic technique, designed for this research, combining acoustic emission and visual monitoring during live load bearing tests, was used to determine the failure load value. Failed frameworks were inspected using a microscope, and failure patterns were identified. One-way ANOVA and Tukey HSD tests were applied for statistical analysis of the results (p-value≤0.05). Results Despite the fact that the chipping strength is proportional to the crosssectional area of the connector, the effect of the cross-sectional area on chipping load revealed no statistically significant differences, while PFMs showed superior chipping strength relative to the zirconia frameworks regardless of the connector's size. A high rate of catastrophic fracture occurred while loading the specimens. Conclusion The effect of the cross-sectional area on chipping load revealed no statistically significant differences in Y-TZP frameworks. The novel sonographic technique may be a potential method to study the behavior of dental ceramics, including chipping and fracture. [ABSTRACT FROM AUTHOR]

Botulinum toxin type A (BTA) injections in masticatory muscles are used to treat numerous clinical conditions. This neurotoxin causes atrophy and transient paralysis of the concerned muscles. The aim of this review is to gather and define the effects of BTA injections in masticatory muscles on the underlying cartilage and bone structures. Electronic search of Medline and Google scholar databases covering the period between January 2007 and July 2019 was carried out. Eligible articles were selected according to the inclusion/exclusion criteria. Fourteen articles were included. BTA injections may cause short term reduction of cortical bone thickness and trabeculation. On the long term, cartilage volume reduction and bone volume loss were evident on the condyle and mandibular angle, at both injected and non-injected mandibular bone structures. Bone mineral density remained unaffected when only one masticatory muscle was injected but was reduced when several masticatory muscles were treated with BTA. Several cellular and molecular alterations were noticed in some articles. Because of evidence of irreversible negative effects of BTA on the underlying structures, possible muscle, bone and cartilage volume reduction should be communicated to the patients prior to any intervention. Further studies are needed to fully understand the cellular mechanisms and molecular responses behind this phenomenon. [ABSTRACT FROM AUTHOR]

Tissue engineering is an alternative to traditional strategies to repair and regenerate temporomandibular joints (TMJ). Nowadays, patients suffering from severe dysfunctions of the TMJ may undergo discectomy, a procedure that consists of removing the damaged disc in hopes of reducing the symptoms. However, tissue engineering presents a potential solution for patients suffering from these disorders, due to the lack of safety and effectiveness of TMJ disc implants. Since 1991, several studies have investigated the possibility of regenerating the articular disc. This literature review aims to expose the new challenges and techniques in TMJ disc tissue engineering whether it concerns cell sourcing, scaffold or bioreactors. As these challenges are overcome, the goal of future studies remains to create a functional biological replacement of the TMJ components. [ABSTRACT FROM AUTHOR]

Introduction During the pandemic of coronavirus disease 2019 (COVID-19), an increase in temporomandibular disorders (TMDs) was noticed in infected patients. In the present study, we aimed to assess the prevalence of TMDs during COVID-19 infection and to evaluate associated factors. Methods An observational cross-sectional online survey was conducted in April and May 2021 in order to estimate the prevalence of TMDs in participants who were previously infected with COVID-19. A multivariable logistic regression model was carried out to explore predicting factors of TMDs during COVID-19 infection. Results In total, the prevalence of TMDs during the COVID-19 infection period among participants was 41.9%. High fever episodes (adjusted odds ratio {aOR}: 3.25), gastro-esophageal reflux (aOR: 2.56), and toothache (aOR: 3.83) during COVID-19 illness were found to be positive predictors of TMDs, while vitamin D deficiency was found to be a negative predictor (aOR: 0.28). Conclusion Our study has highlighted a relatively high prevalence of TMDs in COVID-19-infected patients that may conclude TMDs as a possible COVID-19 symptom. Further studies are warranted to confirm the association between TMDs and COVID-19 infection and thereupon include TMDs among the known symptoms of COVID-19., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Haddad et al.)

Aim and Objective: Force platforms are widely used to evaluate the relationship between bodily posture and jaw positions. The aim and objective of this clinical prospective study was to evaluate the effect of occlusal splints on bodily posture using force platforms., Materials and Methods: Forty-seven female patients with temporomandibular disorders (TMD) underwent a clinical and postural examination before and during an occlusal treatment with an upper splint. Six postural stabilometric examinations were performed under different visual conditions. Postural stability was assessed using a force platform (SATEL). Subjects were evaluated in static and dynamic conditions, with open and closed eyes, at baseline, at 1 week, and at 3 months. Changes in stabilometric parameters (sway area and sway length) were assessed and compared., Results: In static and dynamic positions, the sway surface area decreased significantly after the occlusal guard placement with closed eyes ( p -value, 0.012). Likewise, the sway surface area decreased significantly in the dynamic lateral position with closed eyes ( p -value, 0.018) and in anteroposterior dynamic position with open eyes ( p -value, 0.031). The mean sway length decreased significantly after the placement of the occlusal guard when participants were in the lateral position with open eyes ( p -value, 0.025) and in the anteroposterior position with open eyes ( p -value, 0.014). On a 3-month assessment, the mean surface and mean length decreased significantly after the placement of the occlusal guard for practically all the static and dynamic positions., Conclusion: The sway surface area and sway length decreased significantly with the use of occlusal splints Clinical significance: In female patients with TMD, the use of an occlusal splint is associated with a postural improvement evaluated by posturo-stabilometric tests.