Dental Restorations Research Articles

Novel quinoline photoinitiators for dimethacrylate monomer photopolymerization under UV and blue light

Composite resins based on methacrylated monomers are the main materials for dental restorations, however, incomplete polymerization and leaching have been identified as the major problems in this process, highlighting the importance of a search for new photoinitiating materials with improved properties and, therefore, can produce cheaper and stronger polymers with reduced toxicity. In this work, two novel quinoline derivatives were evaluated to obtain dimethacrylate-based polymers. Here we present the synthesis and characterization of a quinoline derivative containing a hydroxyl group and another containing a methacrylate group, as type II photoinitiator materials for UDMA-based resins polymerization. The photoinitiators were analyzed through photolysis (at two distinct wavelengths) and theoretical calculations were performed via a DFT-based approach, to provide a better understanding of the photoexcitation process of quinoline-based photoinitiators. The thermal stability, mass loss rate and glass transition of the generated polymers and the quinoline photoinitiators were analyzed via TG-DTA and DSC. The morphological characteristics of final polymerized compounds were performed with scanning electron microscopy. The water sorption and solubility were also investigated. Our results indicate that hydroxyl-containing quinoline promotes an efficient photopolymerization of UDMA resin precursors under blue light (65.9 %), while methacrylate-containing quinoline presents higher conversions under ultraviolet irradiation (66.3 %). The polymerization of the compounds presented 40 % to 66 % conversion under 60 s, comparable to the camphorquinone standard at the same conditions. The polymer of UDMA with hydroxyl-containing quinoline, showed a slightly higher water sorption than the methacrylate-containing one and both indicate no solubility in water at 37 °C. Overall, the results show that quinoline-based photoinitiators present an efficient photopolymerization of UDMA and produce fluorescent polymers, similarly to commonly used resin materials.

Minimally Invasive Extraction System Benex-Clinical Evaluation and Comparison.

Tooth extraction is one of the oldest and most well-known surgical procedures in dental medicine. It is still routinely performed by general practitioners and dental undergraduates. The Benex extraction system allows for the extraction of teeth in a vertical direction, which avoids most trauma against surrounding alveolar bone and soft tissues. The study included 56 patients who were recruited from the Department of Oral Surgery, Medical University-Plovdiv. The patients were split into two groups of 28 patients-Group I (control group) and Group II (study group). For each group, the success of the extraction, buccal cortical plate preservation, pain experience and early wound healing were assessed. There was no statistical significance between the success of the extractions in both groups. The Benex extractions preserved the buccal cortical plate in 95% of the cases, whereas the forceps extractions preserved it in only 71.8%, which is statistically significant. On the seventh day, patients in Group II reported less pain, without a significant difference. There was a significantly bigger number of completely healed extraction wounds on the 10th day. Atraumatic extractions allow for more hard and soft tissues to be preserved in the extraction site. This is essential for a successful outcome and the aesthetically pleasing results of the following dental restoration.

Esthetic crown lengthening treatment on the maxillary anterior teeth

Background: Asymmetrical smile design due to uneven gingival margin heights of the anterior upper teeth can lead to aesthetic issues and inadequate crown restorations, necessitating crown lengthening treatment. Purpose: The objective of this case report is to demonstrate the outcomes of crown lengthening to achieve improved aesthetics and symmetric gingival margin heights. Case: A 16-year-old female patient sought treatment for decayed left maxillary anterior teeth. Clinical examination revealed a non-vital tooth (tooth 21) with decay and excessively low gingival margins, along with asymmetrical gingival heights between the incisors and canines. Radiographs indicated radiolucent mass in the pulp chamber. Case Management: Crown lengthening was performed on teeth 12, 11, 21, and 22, and apexification was conducted on tooth 21 using a customized fiber post and lithium disilicate crown. Follow-up evaluations showed no complaints, well-maintained crowns, and healthy gingiva. Conclusion: Crown lengthening is feasible for anterior teeth with low gingival margins, enhancing clinical crown length to support aesthetic and final restorations in maxillary anterior teeth.

A multicenter prospective clinical trial on the effect of domestic bone level implants on single tooth implantation and restoration

Objective: To evaluate the clinical application effects of a domestic bone-level implant system for restoring single tooth loss, and provide clinical evidence for the promotion and application of domestic implants. Methods: A prospective, multicenter clinical trial was conducted from April 2018 to January 2020 in three institutions: Department of Oral Implantology, School & Hospital of Stomatology, Wuhan University, Department of Stomatology, The First Affiliated Hospital of Zhejiang University School of Medicine, and Department of Stomatology, The Third Hospital of Hebei Medical University. The trial planned to include 100 patients for single tooth implantation and restoration, followed up for 1 year, to evaluate the implantation success rate and other related outcomes. Results: This study screened a total of 142 patients and ultimately included 100, comprising 43 males and 57 females with age of (47.0±12.2) years. Ninety-eight out of 100 patients completed a one-year follow-up (98.0%), while 2 patients terminated the trial early due to implant loosening (2.0%). After a one-year follow-up, the implants of the 98 patients were all functioning successfully, with a success rate of 98.0% (98/100). The patients were satisfied with the overall restoration effect. Conclusions: This study indicates that the domestic bone-level implant system has achieved favorable short-term clinical outcomes for single-tooth implantation and restoration.

Comparative Evaluation of Mechanical Properties and Color Stability of Dental Resin Composites for Chairside Provisional Restorations.

Resin composites have become the preferred choice for chairside provisional dental restorations. However, these materials may undergo discoloration, changes in surface roughness, and mechanical properties with aging in the oral cavity, compromising the aesthetics, functionality, and success of dental restorations. To investigate the color and mechanical stability of chairside provisional composite resins, this study evaluated the optical, surface, and mechanical properties of four temporary restoration resin materials before and after aging, stimulated by thermal cycling in double-distilled water. Measurements, including CIE LAB color analysis, three-point bending test, nanoindentation, scanning electron microscopy (SEM), and atomic force microscopy (AFM), were conducted (n = 15). Results showed significant differences among the materials in terms of optical, surface, and mechanical properties. Revotek LC (urethane dimethacrylate) demonstrated excellent color stability (ΔE00 = 0.53-Black/0.32-White), while Artificial Teeth Resin (polymethyl methacrylate) exhibited increased mechanical strength with aging (p < 0.05, FS = 68.40 MPa-non aging/87.21 MPa-aging). Structur 2 SC (Bis-acrylic) and Luxatemp automix plus (methyl methacrylate bis-acrylate) demonstrated moderate stability in optical and mechanical properties (Structur 2 SC: ΔE00 = 1.97-Black/1.38-White FS = 63.20 MPa-non aging/50.07 MPa-aging) (Luxatemp automix plus: ΔE00 = 2.49-Black/1.77-White FS = 87.72 MPa-non aging/83.93 MPa-aging). These results provide important practical guidance for clinical practitioners, as well as significant theoretical and experimental bases for the selection of restorative composite resins.

Analyzing the Salivary Antioxidant Capacity in Children before and after Dental Caries Restoration: A Comparative Scientific Investigation

Aim: The purpose of this study is to examine the total antioxidant capacity (TAC) as a biomarker to investigate oxidative stress in different pathological conditions. The primary goal is to compare the TAC levels in saliva before and after the restoration of carious teeth. Additionally, the study aims to explore potential differences in TAC between genders with the intention of establishing a possible link between salivary TAC and dental caries. Materials and Methods: In this research, we employed a random selection process to assemble two cohorts: Group I, comprising 27 male individuals, and Group II, encompassing 27 females, all falling within the age bracket of 7 to 10 years. Saliva samples were procured from each participant both thirty days prior to and subsequent to the restorative dental intervention. To gauge the levels of total antioxidant capacity (TAC), we employed Cayman’s antioxidant assay kit and quantified the outcomes employing a nanodrop instrument. Results: The obtained data was subjected to statistical analysis using SPSS version 18.0. The paired t-test was used to compare the TAC levels before and after the restorative procedure within each group (Group I and Group II). The results revealed that after restoration, both Group I and Group II showed a significant increase in TAC levels compared to before restoration (P = 0.000). Additionally, the Student t-test was employed to compare the TAC levels between Group I (males) and Group II (females). Interestingly, the study observed that the TAC of saliva was significantly higher in males compared to females, both before and after the restoration of carious teeth. Conclusion: Our research demonstrated reduced TAC levels in areas affected by dental caries, and these levels exhibited a significant rise following the restoration of all carious teeth. Consequently, it can be deduced that the evaluation of caries activity and the effectiveness of its treatment can be facilitated through the assessment of salivary factors, which holds promise for applications in preventive dentistry. Clinical Significance: TAC can be employed as a biomarker and a therapeutic target because a reduced TAC level before restoration is a sign of infection.

Automatic deep learning detection of overhanging restorations in bitewing radiographs.

This study aimed to assess the effectiveness of deep convolutional neural network (CNN) algorithms for the detecting and segmentation of overhanging dental restorations in bitewing radiographs. A total of 1160 anonymized bitewing radiographs were used to progress the artificial intelligence (AI) system for the detection and segmentation of overhanging restorations. The data were then divided into three groups: 80% for training (930 images, 2399 labels), 10% for validation (115 images, 273 labels), and 10% for testing (115 images, 306 labels). A CNN model known as You Only Look Once (YOLOv5) was trained to detect overhanging restorations in bitewing radiographs. After utilizing the remaining 115 radiographs to evaluate the efficacy of the proposed CNN model, the accuracy, sensitivity, precision, F1 score, and area under the receiver operating characteristic curve (AUC) were computed. The model demonstrated a precision of 90.9%, a sensitivity of 85.3%, and an F1 score of 88.0%. Furthermore, the model achieved an AUC of 0.859 on the receiver operating characteristic (ROC) curve. The mean average precision (mAP) at an intersection over a union (IoU) threshold of 0.5 was notably high at 0.87. The findings suggest that deep CNN algorithms are highly effective in the detection and diagnosis of overhanging dental restorations in bitewing radiographs. The high levels of precision, sensitivity, and F1 score, along with the significant AUC and mAP values, underscore the potential of these advanced deep learning techniques in revolutionizing dental diagnostic procedures.

Resin-based dental pulp capping restoration enclosing silica and portlandite nanoparticles from natural resources

Natural-based materials represent green choices for biomedical applications. In this study, resin pulp capping restoration enclosing strengthening silica and bioactive portlandite nanofillers were prepared from industrial wastes. Silica nanoparticles were isolated from rice husk by heat treatment, followed by dissolution/precipitation treatment. Portlandite nanoparticles were prepared by calcination of carbonated lime waste followed by ultrasonic treatment. Both were characterized using x-ray diffraction, energy dispersive x-ray, and transmission electron microscopy. For preparing pulp capping restoration, silica (after silanization) and/or portlandite nanoparticles were mixed with 40/60 weight ratio of bisphenol A-glycidyl methacrylate and triethylene glycol dimethacrylate. Groups A, B, and C enclosing 50 wt.% silica, 25 wt.% silica + 25 wt.% portlandite, and 50 wt.% portlandite, respectively, were prepared. All groups underwent microhardness, compressive strength, calcium release, pH, and apatite forming ability inspection in comparison to mineral trioxide aggregate (MTA) positive control. In comparison to MTA, all experimental groups showed significantly higher compressive strength, group B showed comparable microhardness, and group C showed significantly higher calcium release. Groups B and C showed prominent hydroxyapatite formation. Thus, the preparation of economic, silica-fortified, bioactive pulp capping material from under-utilized agricultural residues (rice husk) and zero-value industrial waste (carbonated lime from sugar industry) could be achieved.

Comparison of Additive and Subtractive Manufacturing for Fixed Dental Restorations: A Systematic Review and Meta-Analysis

Comparison of Additive and Subtractive Manufacturing for Fixed Dental Restorations: A Systematic Review and Meta-Analysis

Polymerizable alkyl 2-(tosylmethyl)acrylates: Highly efficient addition-fragmentation chain transfer agents for the development of low shrinkage dental composites

One of the major drawbacks for restorative dentistry is the polymerization shrinkage and the consequential shrinkage stress in methacrylate-based dental composites. An efficient way to reduce shrinkage stress is the incorporation of addition fragmentation chain transfer agents (AFCT agents). In this contribution, five novel polymerizable allyl sulfones were synthesized in four to five steps. A photo-DSC study was carried out in order to evaluate the influence of the addition of each AFCT agent on the polymerization rate of a dimethacrylate-based monomer mixture. The glass transition temperature (Tg) of the resulting networks was measured using DMTA. Dental composites based on these new chain transfer agents (CTAs) were prepared. A combination of camphorquinone, ethyl 4-(dimethylamino)benzoate and bis-(4-t-butylphenyl)-iodonium hexafluorophosphate was selected as photoinitiator system. Low shrinkage force values, suitable ambient light working time and excellent mechanical properties were obtained for all CTA based materials. Composites based on three of the synthesized CTAs even exhibited higher flexural modulus than the corresponding CTA-free material. Furthermore, a significant reduction of unreacted CTA leaching was found if a polymerizable moiety was introduced in the CTA structure. Hence, the incorporation of polymerizable allyl sulfones in dental composites is a promising strategy to obtain low shrinkage materials exhibiting improved biocompatibility.

Influence of Low pH on the Microhardness and Roughness Surface of Dental Composite-A Preliminary Study.

Dental composites are gaining great popularity in restorative dentistry because of their aesthetic appeal and capacity to replicate the natural color of teeth. Nevertheless, their lifespan and durability rely on various factors, such as the polishing technique and the environmental conditions they are exposed to. The study aimed to assess the influence of the method of final polishing of dental composite on the surface roughness and microhardness of materials also considering the environment of different pHs. Disc-shaped samples (5 mm diameter and 2 mm thickness) have been prepared for microhardness and roughness tests from two dental composites: A2 Clearfil Majesty ES 2 Classic and A2D Clearfil Majesty Premium. One-third of samples were polished with polishing discs, OptiDisc, another one-third of samples were polished with Eve Diacomp Twist rubbers and polishing brush with diamond particles, and rest of the samples were stored without any polishing (the control group). Tested materials were incubated in distilled water or acidic buffer (pH = 2) for 3 weeks at a temperature of 37 °C. No statistically significant differences were found for roughness for the two materials tested after incubation in liquids. A decrease in Vicker microhardness was found for Clearfil Majesty ES 2 Classic after soaking in a low pH liquid, and no such relationship was found for Clearfil Majesty Premium. The improved resistance of these materials to the negative oral environment may result in the longer survival of composite restorations in patients with poor diet or diseases, causing a decrease in oral pH.

Effect of TiO2 and CaO Addition on the Crystallization and Flexural Strength of Novel Leucite Glass-Ceramics.

The aim of this study was to investigate the effects of TiO2/CaO addition on the crystallization and flexural strength of leucite glass-ceramics (GC). Synthesis of translucent and high strength GCs is important for the development of aesthetic and durable dental restorations. To achieve this, experimental aluminosilicate glasses (1-3 mol% TiO2 and CaO (B1, B2, B3)) were melted in a furnace to produce glasses. Glasses were ball milled, screened and heat treated via crystallization heat treatments, and characterized using XRD, differential scanning calorimetry, dilatometry, SEM and biaxial flexural strength (BFS). Increasing nucleation hold time (1-3 h) led to a reduction in crystallite number for B2 and B3 GC, and significant differences in leucite crystal size at differing nucleation holds within and across test groups (p < 0.05). A high area fraction of leucite crystals (55.1-60.8%) was found in the GC, with no matrix microcracking. Changes in the crystal morphology were found with higher TiO2/CaO addition. Mean BFS of the GC were 211.2-234.8 MPa, with significantly higher Weibull modulus (m = 18.9) for B3 GC. Novel glass compositions enriched with TiO2/CaO led to crystallization of leucite GC of high aspect ratio, with high BFS and reliability. The study's findings suggest a potential high performance translucent leucite GC for use in the construction of dental restorations.

Do Not Extract Teeth which you could Restore Perhaps you do?

The Kurer Anchor System, a once widely used dental restoration method, offered a solution for retaining root canal posts in treated teeth. Despite its success in preserving natural teeth and providing a cost-effective alternative to implants, the system's popularity waned due to changes in the dental industry. This paper revisits the Kurer Anchor System, examining its clinical efficacy, economic advantages, and potential integration with modern dental practices. Emphasizing the importance of implant surface cleanliness, the paper advocates for the revival of the Kurer Anchor System in contemporary dentistry. The conclusion underscores the need for educating dental professionals about this system's benefits and proper application.

What can impact on the presence of carious lesions in first permanent molars? Revisiting the association between MIH and caries.

Assess whether the independent variables (IV) such as number of MIH-affected molars, MIH severity, past caries experience, visible plaque index (VPI), gingival bleeding index (GBI), age, and gender affect the presence of caries lesion (DMF_s) in first permanent molars, considering or not atypical restoration in MIH-affected molars as a previous caries lesion. A sample of 476 schoolchildren, aged 6-10years, were evaluated for MIH and caries diagnosis, using the Severity Scoring System (MIH-SSS) and the International Caries Detection and Assessment System (ICDAS), respectively. From the ICDAS, the DF-s/ D-s and df-s were calculated. The Zero-inflated Negative Binomial Regression was used to evaluate the impact of the IV on the dependent variable, considering or not the restorative component in MIH-affected molars. When the presence of caries was evaluated with the restorative component, age, MIH severity and past caries experience had a significant impact on the dependent variable (R2 = 0.176). Without the restorative component in MIH-affected molars, only age and past caries experience were statistically significant (R2 = 0.167). Since in the case of MIH teeth restoration may be attributed to post-eruptive breakdown rather than previous caries lesions, in the present study MIH did not influence the presence of caries lesions in the MIH-affected molars showing that restoration is not an adequate parameter for measuring the historical occurrence of caries. The first permanent molars may not necessarily be at an increased risk of caries due to MIH if the etiological factors for caries development are effectively managed.

Zirconia toughened fluorosilicate glass-ceramics for dental prosthetic restorations

BackgroundDental glass-ceramics have limited strength and are unsuitable for high-stress-bearing areas. Zirconia stands out as a popular choice for reinforcing dental glass-ceramics due to its biocompatibility and high fracture toughness. ObjectivesThe objective of the study is to investigate the effect of an increase in zirconia (25, 30, 35 and 50 wt%) on microstructure, chemical solubility, hardness, fracture toughness, and brittleness index of fluorosilicate glass systems for dental restorative applications. Material and methodsThe fluorosilicate glass frit was obtained through the melt-quench technique. The glass frit was ball-milled with 25, 30, 35 and 50 wt % of 3 mol % yttria-stabilized zirconia (G-25Z, G-30Z, G-35Z, and G-50Z). The composites were sintered to 1000 °C for 48h at a heating rate of 5 °C/min. The glass frit was subject to differential scanning calorimetry. Phase analysis and microstructural characterization were carried out. The crystallite size of zirconia and glass-ceramics, micro-hardness, indentation fracture toughness, brittleness index, and chemical solubility were evaluated. ResultsPhase analysis reveals tetragonal and monoclinic zirconia with minor peaks of forsterite, fluorphlogopite, norbergite, and spinel. Their microstructures reveal the characteristic house-of-cards arrangement of fluorophlogopite crystals with dispersed zirconia. The results of hardness and fracture toughness show a statistically significant improvement with an increase in zirconia content. The crystallite size of zirconia and fluorophlogopite crystals with aspect ratio, brittleness index, and chemical solubility declined as the zirconia content increased. ConclusionsIncrease in zirconia content from 25 wt % to 50 wt % in heat-treated fluorosilicate glass systems reveals non-reactive zirconia with a stable glass matrix and limits the growth of fluorphlogopite crystals with a house-of-cards microstructure. This results in a range of properties suitable for dental restorations of enhanced hardness, and improved fracture toughness. Despite these improvements, the material maintains its machinability with reduced chemical solubility.

Multi-Species Biofilm Interactions and Their Impact on the Biocorrosion of Copper-Coated CoCr Alloys in Dental Application

Biocorrosion of materials used in dental restorations is a complex process involving various bacterial species that coexist as biofilms. Since copper possesses excellent antibacterial properties, it could help minimize this problem. The aim of this study is to assess the antibiofilm characteristics and corrosion resistance of CoCr and copper-coated CoCr alloys in a multispecies biofilm model. CoCr alloys and CoCr coated with copper (CoCr/Cu) using Physical Vapor Deposition (PVD) were investigated. The samples were incubated in media with and without a multispecies biofilm for 24 h and for 15 days. Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) were used to assess the corrosion behavior of the samples. Scanning Electron Microscopy (SEM) was utilized to observe the growth of multispecies biofilms and the type of corrosion. The Mann–Whitney U test was employed to examine corrosion results, with significant differences defined as p &lt; 0.05. CoCr/Cu alloys demonstrated superior corrosion resistance at 24 h and 15 days in the presence of biofilm compared to those without coating. No differences were observed in multispecies biofilm formation at 24 h. The study demonstrates that copper-coated CoCr alloys (CoCr/Cu) exhibit a more positive corrosion potential (Ecorr) compared to uncoated CoCr alloys, both in the presence and absence of multispecies biofilm (BP) at 24 h and 15 days. After 15 days, the potential of CoCr/Cu with BP was −0.144 V, compared to −0.252 V for uncoated CoCr. These significant differences in Ecorr values underscore the protective effect of copper against corrosion in multispecies biofilm environments.

Assessing tooth wear progression in non-human primates: a longitudinal study using intraoral scanning technology.

Intraoral scanners are widely used in a clinical setting for orthodontic treatments and tooth restorations, and are also useful for assessing dental wear and pathology progression. In this study, we assess the utility of using an intraoral scanner and associated software for quantifying dental tissue loss in non-human primates. An upper and lower second molar for 31 captive hamadryas baboons (Papio hamadryas) were assessed for dental tissue loss progression, giving a total sample of 62 teeth. The animals are part of the Southwest National Primate Research Center and were all fed the same monkey-chow diet over their lifetimes. Two molds of each dentition were taken at either two- or three-year intervals, and the associated casts scanned using an intraoral scanner (Medit i700). Tissue loss was calculated in WearCompare by superimposition of the two scans followed by subtraction analysis. Four individuals had dental caries, and were assessed separately. The results demonstrate the reliability of these techniques in capturing tissue loss data, evidenced by the alignment consistency between scans, lack of erroneous tissue gain between scans, and uniformity of tissue loss patterns among individuals (e.g., functional cusps showing the highest degree of wear). The average loss per mm2 per year for all samples combined was 0.05 mm3 (0.04 mm3 for females and 0.08 mm3 for males). There was no significant difference in wear progression between upper and lower molars. Substantial variation in the amount of tissue loss among individuals was found, despite their uniform diet. These findings foster multiple avenues for future research, including the exploration of wear progression across dental crowns and arcades, correlation between different types of tissue loss (e.g., attrition, erosion, fractures, caries), interplay between tissue loss and microwear/topographic analysis, and the genetic underpinnings of tissue loss variation.

Modeling fracture in multilayered teeth using the finite volume-based phase field method

The present work, utilizing the finite volume-based phase field method (FV-based PFM), aims to investigate the initiation and propagation of cracks in the second molar of the left mandible under occlusal loading. By reconstructing cone beam computed tomography scans of the patient, the true morphology and internal mesostructure of the entire tooth are implemented into numerical simulations, including both 2D slice models and a realistic 3D model. Weibull functions are introduced to represent the tooth's heterogeneity, enabling the stochastic distribution characteristics of mechanical parameters. The results indicate that stronger heterogeneity leads to greater crack tortuosity, uneven damage distribution, and lower fracture stress. Additionally, different cusp angles (50° and 70°) and pre-existing fissure morphologies (i.e., U-shape, V-shape, IK-shape, I-shape, and IY-shape) also significantly affect the mechanical performance of the tooth. The study reveals that different cusp angles affect the location of crack initiation. Overall, this work demonstrates the utility of the FV-based PFM framework in capturing the complex fracture behavior of teeth, which can contribute to improved clinical treatment and prevention of tooth fractures. The insights gained from this study can inform the design of dental crown restorations and the optimization of cusp inclination and contact during clinical occlusal adjustments.

Comparing Properties of Urethane Dimethacrylate (UDMA) Based 3D Printing Resin Using N-Acryloylmorpholine (ACMO) and Triethylene Glycol Dimethacrylate (TEGDMA) Separately as Diluents

The purpose of our study reported here was to investigate the performance of urethane dimethacrylate (UDMA) based 3D printable resin systems when using N-acryloylmorpholine (ACMO) as a diluent. UDMA was mixed with ACMO with a series of mass ratios, and the viscosity, degree of double bond conversion (DC), volumetric shrinkage (VS), flexural strength (FS), and modulus (FM), water sorption (WS) and solubility (SL), hardness, wear resistance, and accuracy thereof the obtained resin systems were studied and compared with triethylene glycol dimethacrylate (TEGDMA) diluted resin systems. The results showed that the ACMO diluted resin systems had a higher viscosity than the TEGDMA diluted resin systems with the same diluent concertation. Replacing TEGDMA with ACMO showed improvement in DC, VS, FS and FM in dry conditions, and the accuracy of 3D printable resin systems. However, the reduction of water resistance and wear resistance would limit the application as dental restoration materials of ACMO diluted 3D printable resin systems. With the aim to improve the water resistance and wear resistance of ACMO diluted 3D printable resin systems, we suggest further research concerned about using a new base resin and optimizing resin composition should be undertaken.

Neurobehavioral, neurotransmitter and redox modifications in Nauphoeta cinerea under mixed heavy metal (silver and mercury) exposure

Heavy metals are encountered in nature, and are used in several human endeavors, including in dental fillings. It is well known that the safety of metals depends on their chemical form, as well as the dose and route through which biological systems are exposed to them. Here, we used the Nauphoeta cinerea model to examine the mechanism by which salts of the heavy metals used in dental fillings – silver and mercury – exert their neurotoxicity. Nymphs exposed to heavy metals presented with reduced motor and exploratory abilities as they spent more time immobile, especially in the periphery of a novel object, and covered less distance compared with control nymphs. Exposure to AgNO3 and HgCl2 also exacerbated levels of oxidative stress markers (MDA & ROS) and the neurotransmitter regulators – AChE and MAO, while reducing antioxidant activity markers, both in biochemical (thiol & GST) and RT-qPCR (TRX, GST, SOD, Catalase) examinations, in neural tissues of the cockroach. The observed disruptions in neurolocomotor control, synaptic transmission and redox balance explain how heavy metal salts may predispose organisms to neurological disorders.