Novel antibacterial mouthguard material manufactured using silver-nanoparticle–embedded ethylene-vinyl acetate copolymer masterbatch

Enhancing sports mouthguards with PLA + and PC: stress reduction, energy absorption, and topology optimization

OBJECTIVES

The objective of this paper was to compare the effectiveness of different materials for mouthguards in preventing oral and maxillofacial injuries during sports activities. The present study compares the stress-reduction and energy absorption capabilities of two other fused filament materials - poly(lactic-acid plus) (PLA+) and polycarbonate (PC), with Ethylene-vinyl acetate (EVA), which is the most commonly used material for mouthguard fabrication.

MATERIALS AND METHODS

Two human skulls were modelled, and a boxing glove simulated punches along the x, y, and z-axes with 5 mm displacement with 1 kN force. Firstly, the maximum principal stress curve in the skull was compared for forces along the three perpendicular directions. Furthermore, the present study examines materials energy absorption properties, including their specific energy absorption characteristics and initial peak von Mises stresses. Additionally, a topology optimization approach is used to create an alternative design for a mouthguard to improve specific energy absorption.

RESULTS

The model without a mouthguard showed the highest stress concentration of 32.298 MPa in the teeth, followed by the EVA material, which resulted in a maximum principal stress of 28.525 MPa. Fused filament 3D materials, such as PLA + and PC, on the other hand, showed better mechanical effectiveness in both lower jaw dislocation and lower maximum principal stress by 30.82% and 51.25% in the mandibular and maxillary teeth. Though EVA comparatively shows better specific energy absorption capability at 2.24 kJ/kg post-optimization than PLA + and PC, the peak principal stress experienced in the mandibular region was comparatively higher. The topology optimization, however, improved the energy-absorbing capabilities of PLA + by 4.5 times, reaching 1.37 kJ/kg and PC from 0.165 kJ/kg to 0.38 kJ/kg.

CONCLUSIONS

This study demonstrates that PLA + and PC have better stress reduction capabilities than EVA and could be promising materials for the fabrication of mouthguards in sports activities. This study highlights the importance of topology optimization in dental materials science and engineering to develop safer and more effective mouthguard designs.

Silver nanoparticles incorporated dental restorative resin and its antibiofilm effect

Dental restoration materials are susceptible to bacterial biofilm formation, which damages the restorations and causes oral health problems. Therefore, to overcome this, silver nanoparticles (AgNPs) are studied widely due to their antimicrobial, anti-inflammatory and healing properties. The purpose of this study was to develop a strategy for incorporating AgNPs onto the surface of bisacrylic resin (Bis) to evaluate its antibiofilm effects using Streptococcus sanguinis and Actinomyces naeslundii. AgNPs with an average size of 25 nm at two different concentrations were dispersed on the Bis surface (Bis-AgNPs) by mechanical deposition. Ag release was quantified until 7 days of incubation. Bacterial growth was assessed using a viability assay kit and observed using confocal microscopy. The biofilm biomass was quantified using arbitrary fluorescence units. Cell viability was evaluated using an MTT assay. The results showed that Bis-AgNPs significantly inhibited biofilm formation along with a significant difference in the viability of human gingival fibroblasts. The quantification confirmed a decrease in Ag release over time, and elemental mapping showed AgNP penetration up to 10 µm from the surface. Therefore, it was concluded that Bis-AgNPs presented enhanced antibiofilm properties, even at a concentration with no adverse effects. Therefore, this nanocomposite may be a promising alternative for biofilm control in temporary restorative materials.

Effects of different custom-made mouthguard palatal extensions on the stress-state of dentoalveolar structures: a 3D-FEA

OBJECTIVES

The present study aimed to simulate the influence of palatal extensions for custom-made mouthguards (MGs) on protecting dentoalveolar structures and to provide a theoretical basis for designing a comfortable MG.

MATERIALS AND METHODS

Based on finite element analysis (3D-FEA), five groups of maxillary dentoalveolar models of wearing MGs were established: no MG on palatal side (NP), on palatal gingival margin (G0), 2 mm from the palatal gingival margin (G2), 4 mm from the palatal gingival margin (G4), 6 mm from the palatal gingival margin (G6), and 8 mm from the palatal gingival margin (G8). A cuboid was created to simulate the solid ground impacted in falls, a gradually increasing force was applied from 0 to 500 N on the vertical ground, and the distribution and peak values of the Critical modified von-Mises stress, maximum principal stress, and displacement of dentoalveolar models were calculated.

RESULTS

Stress distribution range, stress, and deformation peak value of dentoalveolar models increased as the impact strength increased, at 500 N. Maximum critical modified von-Mises stress, peak maximum principal stress and maximum displacement of dentoalveolar models G4, G3, G2, G1, G0, and NP were 154.5 MPa, 154.5 MPa, 154.4 MPa, 154.7 MPa, 154.4 MPa, and 154.7 MPa; 191.65 MPa, 192.11 MPa, 191.62 MPa, 191.81 MPa, 191.56 MPa, and 191.62 MPa; and 88.78 μm, 88.57 μm, 88.19 μm, 88.67 μm, 88.43 μm, and 89.04 μ, respectively. However, the position of the MG palatal edge had little effect on stress distribution, stress, and deformation peak values of the dentoalveolar models.

CONCLUSIONS

Different extension ranges of the MG palatal edge have little effect on the protective effects of MGs on maxillary teeth and maxilla. An MG with palatal extension on the gingival margin is more appropriate than other models and may help dentists to design a suitable MG and increase its usage.

CLINICAL RELEVANCE

MGs with palatal extensions on the gingival margin may provide a more comfortable wearing experience for individuals involved in sports and encourage increased MG usage.

Sports mouthguard overview: Materials, fabrication techniques, existing standards, and future research needs

Sports mouthguards are proven devices that reduce both the probability of and damage to orofacial tissues. While commonly used, clinicians may be unaware of the different sports mouthguard materials, proposed fabrication techniques, design recommendations, and newer digital fabrication methods. An overview of existing sports mouthguard standards is presented. It identifies that identify that the present requirements, while historically chosen in good faith, appear to be arbitrarily selected and not from clinical evidence-based derived data. In addition, identified sports mouthguard heterogeneous testing and data acquisition methods distinguishes that little possibility is afforded for the correlation of results. Furthermore, updated evidence with concussion prevention and/or alleviation is presented with evidence provided by sports mouthguard imbedded technology. The need for continued research is stressed to provide evidence-based data for concussion alleviation/prevention, digital fabrication methods and materials, and clinically based information for the revision of existing standards.

Silver nanoparticles induced testicular damage targeting NQO1 and APE1 dysregulation, apoptosis via Bax/Bcl-2 pathway, fibrosis via TGF-β/α-SMA upregulation in rats

In medicine, silver nanoparticles (AgNPs) are employed often. They do, however, have negative impacts, particularly on the reproductive organs. This research aimed to assess AgNP impact on the testis and the possible intracellular mechanisms to induce testicular deteriorations in rats at various concentrations and different time intervals. Sprague Dawley rats (n = 40) were allocated into four equal groups: the control one, and three other groups injected intra-peritoneally with AgNP solution 0.25, 0.5, and 1 mg/kg b.w. respectively for 15 and 30 days. Our findings revealed that AgNPs reduced body and testicular weights, estradiol (E2) and testosterone (T) hormone levels, and sperm parameters while elevating the nitric oxide and malondialdehyde levels with inhibition of reduced glutathione contents in testicular tissue. Interestingly, AgNPs significantly upregulated the testicular inducible nitric oxide synthase, B cell lymphoma 2 (Bcl-2)-associated X, transforming growth factor, and alpha-smooth muscle actin (α-SMA) expression levels. However, apurinic/apyrimidinic endo deoxyribonuclease 1 (APE1), NAD (P) H quinone dehydrogenase 1 (NQO1), and Bcl-2 expression levels were all downregulated indicating exhaustion of body antioxidant and repairing defense mechanisms in testicles in comparison with the control rats. Various histological alterations were also detected which dramatically increased in rats sacrificed after 30 days such as loss of the lining cells of seminiferous tubules with no spermatozoa and tubular irregularities associated with thickening of their basement membranes. Immunolabeling implicated in the apoptotic pathway revealed a negative expression of Bcl-2 and marked immunoreactivity for caspase-3 after 30 days of AgNP treatment in comparison to the control rats. To our knowledge, there have been no previous publications on the role of the α-SMA, APE1, and NQO1 genes in the molecular pathogenesis of AgNP testicular cytotoxicity following AgNP acute and chronic exposure.

Putative adverse outcome pathways for silver nanoparticle toxicity on mammalian male reproductive system: a literature review

BACKGROUND

Adverse outcome pathways (AOPs) are conceptual frameworks that organize knowledge about biological interactions and toxicity mechanisms. They present a sequence of events commencing with initial interaction(s) of a stressor, which defines the perturbation in a biological system (molecular initiating event, MIE), and a dependent series of key events (KEs), ending with an adverse outcome (AO). AOPs have recently become the subject of intense studies in a view to better understand the mechanisms of nanomaterial (NM) toxicity. Silver nanoparticles (Ag NPs) are one of the most explored nanostructures and are extensively used in various application. This, in turn, has increased the potential for interactions of Ag NPs with environments, and toxicity to human health. The aim of this study was to construct a putative AOPs (pAOP) related to reproductive toxicity of Ag NPs, in order to lay the groundwork for a better comprehension of mechanisms affecting both undesired toxicity (against human cell) and expected toxicity (against microorganisms).

METHODS

PubMed and Scopus were systematically searched for peer-reviewed studies examining reproductive toxicity potential of Ag NPs. The quality of selected studies was assessed through ToxRTool. Eventually, forty-eight studies published between 2005 and 2022 were selected to identify the mechanisms of Ag NPs impact on reproductive function in human male. The biological endpoints, measurements, and results were extracted from these studies. Where possible, endpoints were assigned to a potential KE and an AO using expert judgment. Then, KEs were classified at each major level of biological organization.

RESULTS

We identified the impairment of intracellular SH-containing biomolecules, which are major cellular antioxidants, as a putative MIE, with subsequent KEs defined as ROS accumulation, mitochondrial damage, DNA damage and lipid peroxidation, apoptosis, reduced production of reproductive hormones and reduced quality of sperm. These successive KEs may result in impaired male fertility (AO).

CONCLUSION

This research recapitulates and schematically represents complex literature data gathered from different biological levels and propose a pAOP related to the reproductive toxicity induced by AgNPs. The development of AOPs specific to NMs should be encouraged in order to provide new insights to gain a better understanding of NP toxicity.

Dimensions of Hybrid and Nanohybrid Mouthguards for Mixed Martial Arts Fighters-Evaluation of a New Method of Fabrication

Ethylene vinyl acetate mouthguards are the most often used custom protective intraoral appliances by combat sports practitioners. However, due to the difficulties in maintaining the hygiene of such mouthguards and thinning during fabrication, resulting in difficulty in predicting final dimensions, they may not be the optimal solution. The aim of this research was to evaluate an innovative method of mouthguard formation using intraoral modeling of the mouthguard pattern, hybrid acrylic material, and the addition of ZnO nanoparticles. Seventeen mouthguards patterns and 34 custom mouthguards were evaluated: 17 hybrid and 17 nanohybrid. A total of 1122 measurements were performed: each mouthguard and pattern was measured at 22 points. Statistical analyses were performed with the use of IBM^® SPSS^® Statistics 27.0.0 software (IBM, Armonk, NY USA). The mean thickness of the patterns and mouthguards at all labial areas of central incisors were between 4.65 and 4.80 mm. The thickness at the buccal surface of the first molar was between 3.71 and 4 mm, and at the occlusal surface between 3.40 and 3.56 mm in the cusp area. All measurements of hybrid and nanohybrid mouthguards were strongly and highly correlated with the measurements of the mouthguard patterns. Hybrid and nanohybrid mouthguards are an advantageous alternative to thermoformed custom appliances.

Therapeutic Applications of Antimicrobial Silver-Based Biomaterials in Dentistry

Microbial infection accounts for many dental diseases and treatment failure. Therefore, the antibacterial properties of dental biomaterials are of great importance to the long-term results of treatment. Silver-based biomaterials (AgBMs) have been widely researched as antimicrobial materials with high efficiency and relatively low toxicity. AgBMs have a broad spectrum of antimicrobial properties, including penetration of microbial cell membranes, damage to genetic material, contact killing, and dysfunction of bacterial proteins and enzymes. In particular, advances in nanotechnology have improved the application value of AgBMs. Hence, in many subspecialties of dentistry, AgBMs have been researched and employed, such as caries arresting or prevention, root canal sterilization, periodontal plaque inhibition, additives in dentures, coating of implants and anti-inflammatory material in oral and maxillofacial surgery. This paper aims to provide an overview of the application approaches of AgBMs in dentistry and present better guidance for oral antimicrobial therapy via the development of AgBMs.

Mouthguards in dentistry: Current recommendations for dentists

Properly fitted mouthguards reduce the risk and severity of orofacial injury, to both hard and soft tissues, preventing thousands of dollars of trauma management. In this review, findings from recent research will be evaluated to discuss the strengths and limitations of the different types of mouthguards, including their indications by sport. Design, ideal dimensions, and other characteristics will also be explored. Additionally, patient education and motivation will be examined, with a focus on the dentist's role in this regard. Finally, in addition to proper oral hygiene, the importance of proper mouthguard maintenance and evaluation will be discussed. This review will therefore be able to act as a guide for dentists looking to provide patients of all ages with personal protective equipment and stay up-to-date on recent developments in this branch of the sports dentistry field.

The Impact of Sport Training on Oral Health in Athletes

Athletes' oral health appears to be poor in numerous sport activities and different diseases can limit athletic skills, both during training and during competitions. Sport activities can be considered a risk factor, among athletes from different sports, for the onset of oral diseases, such as caries with an incidence between 15% and 70%, dental trauma 14-70%, dental erosion 36%, pericoronitis 5-39% and periodontal disease up to 15%. The numerous diseases are related to the variations that involve the ecological factors of the oral cavity such as salivary pH, flow rate, buffering capability, total bacterial count, cariogenic bacterial load and values of secretory Immunoglobulin A. The decrease in the production of S-IgA and the association with an important intraoral growth of pathogenic bacteria leads us to consider the training an "open window" for exposure to oral cavity diseases. Sports dentistry focuses attention on the prevention and treatment of oral pathologies and injuries. Oral health promotion strategies are needed in the sports environment. To prevent the onset of oral diseases, the sports dentist can recommend the use of a custom-made mouthguard, an oral device with a triple function that improves the health and performance of athletes. During training, the sports dentist must monitor the athletes and the sports examination protocol must be implemented with the inclusion of the clinical examination, quantitative and qualitative analysis of saliva and instructions on the use, cleansing and storage of the mouthguard.

Applications of Silver Nanoparticles in Dentistry: Advances and Technological Innovation

Silver nanoparticles (AgNPs) have been successfully applied in several areas due to their significant antimicrobial activity against several microorganisms. In dentistry, AgNP can be applied in disinfection, prophylaxis, and prevention of infections in the oral cavity. In this work, the use of silver nanoparticles in dentistry and associated technological innovations was analyzed. The scientific literature was searched using PubMed and Scopus databases with descriptors related to the use of silver nanoparticles in dentistry, resulting in 90 open-access articles. The search for patents was restricted to the A61K code (International Patent Classification), using the same descriptors, resulting in 206 patents. The results found were ordered by dental specialties and demonstrated the incorporation of AgNPs in different areas of dentistry. In this context, the search for patents reaffirmed the growth of this technology and the dominance of the USA pharmaceutical industry over AgNPs product development. It could be concluded that nanotechnology is a promising area in dentistry with several applications.

Alterations in reproductive parameters and gene expression in Balb/c mice testes after exposure to silver nanoparticles

Silver nanoparticles (AgNPs) have become one of the most common nanomaterials in various commercial products; however, its potential toxicity to the male reproductive system and the possible mechanisms remains unknown. Our study aimed to investigate the toxicity of silver nanoparticle (AgNPs) in the testis and to elucidate its possible mechanisms. We exposed 6-week-old Balb/c male mice to AgNP daily [0 (control), 30 or 125 mg/kg BW] for 90 days. The histological structure, sperm production and levels of reproductive hormones were assessed; we also observed apoptotic cell nuclei and the ultrastructural characteristics of the testis. Microarray analyses were used to identify differentially expressed genes, and dysregulated apoptosis-related genes and protein were also analysed. Our results indicated that 125 mg/kg AgNP changed testis morphology and decreased sperm production. AgNP treatment also increased apoptosis of germ cells and induced the presence of swollen or dissolved mitochondria in the testis. Microarray analysis showed the expression of 383 genes was altered by AgNP treatment, with apoptosis-related genes showing the greatest changes. Furthermore, we verified dysregulated apoptosis-related genes and proteins (caspase3 and Myc). These results demonstrated that AgNP induced changes of testis morphology, sperm production and apoptosis-related genes, suggested this process maybe associated with apoptosis.