Monomer Release from Dental Resins: The Current Status on Study Setup, Detection and Quantification for In Vitro Testing

Monomer release, cytotoxicity, and surface roughness of temporary fixed prosthetic materials produced by digital and conventional methods

This study compared surface roughness, monomer release, and, cytotoxicity of temporary fixed prosthetic materials manufactured using the conventional, CAD/CAM milling and 3D printing methods. Disc-shaped samples (2 mm height, 5 mm diameter) were prepared from four materials [polyethyl methacrylate/polymethyl methacrylate (Dentalon Plus-DP), bis-acrylic composite resin (Protemp 4-PT), polymethyl methacrylate CAD/CAM disc (On Dent), and methacrylate-based resin (QuraCROWN Temp)]. Surface roughness was measured with a profilometer; scanning electron microscopy (SEM) was used for surface characterization. Following 24, 72, and 120 h of artificial saliva incubation for the samples, the obtained extracts were evaluated for cytotoxicity by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test in the mouse fibroblast cell. Monomer release from the test samples was analyzed by High‑Performance Liquid Chromatography. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) was performed to evaluate the chemical composition of artificial saliva extracts. Cell viability was assessed by one-way ANOVA, and surface roughness by Kruskal-Wallis and Mann-Whitney U tests. No monomer was detected in artificial saliva for any materials. The FTIR spectroscopy of the extracts did not show any peaks corresponding to these monomer or polymer structures, indicating that no residual monomer or polymer was released into the artificial saliva after exposure to artificial saliva. 3D-printed materials were significantly more cytotoxic than the other three test materials at all time points and dilutions (p < 0.05). The highest cell viability rates were detected in CAD/CAM milling (99.43 ± 3.79) at 24 h and PT materials (100.47 ± 5.31) at 72 h for 1:8 dilution. At 1:4 dilution, except for the DP-3D printing test groups, the other groups show similar cell viability rates with the control group (p > 0.05). Digitally manufactured materials had lower roughness than conventionally produced ones (p < 0.05). CAD/CAM milling and PT materials were the most biocompatible, while 3D-printed material was found to be cytotoxic. CAD/CAM milling and PT materials may offer safe and effective options for temporary prosthetic restorations. Although DP showed acceptable results, it was less effective than CAD/CAM milling and PT materials. Due to their cytotoxicity, 3D-printed materials require further investigation before clinical use.

Assessing Toxicological Safety of EverX Posterior and Filtek Ultimate: An In-Depth Extractable and Leachable Study Under ISO 10993-17 and 10993-18 Standards

This study critically evaluates the biocompatibility and toxicological safety of EverX Posterior (eXP) and Filtek Ultimate (FU) dental composites following the International Standardization Organization (ISO) 10993-17:2023 and 10993-18:2020 guidelines. Our research highlights important findings on the depth of cure, water absorption, solubility, and release profiles of organic compounds in these composites using advanced chromatographic techniques. The analysis revealed that both eXP and FU composites are safe for patients regarding extractable and leachable (E&L) compounds, indicating a low risk of adverse biological effects. It was found that eXP and FU had solubilities of 6.062 ± 0.576 and 0.864 ± 0.436 μg/mm3, respectively, revealing their stability and reliability for clinical use. Our results suggest that there is no significant difference in the release profiles of the uncured (dough) and cured forms of these materials. Also, the likelihood of systemic toxicological effects caused by the identified E and L compounds is considered to be low. This research emphasizes the compliance of these materials with strict ISO standards and highlights the importance of conducting extraction studies on both dough and cured forms for comprehensive toxicological safety assessments in dental practice.

A comparative in vitro study on monomer release from flash-free or conventional bonding systems

OBJECTIVES

To examine the amount of residual monomer released from adhesive-precoated flash-free brackets and compare it to traditional light cure and chemical cure adhesives.

MATERIALS AND METHODS

Sixty stainless steel brackets were bonded on upper premolar teeth using three groups of adhesive systems: Adhesive-precoated flash-free system, Transbond XT light cure, Sia chemical cure. The extracts of 0.5 ml of liquid samples were taken on the first, 7th, 21st, and 35th days. To determine the amount of residual monomer release, extracted samples were analyzed using a liquid chromatography device.

RESULTS

Urethane-dimethacrylate, triethylene glycol dimethacrylate, hydroxyethyl methacrylate and Bisphenol A-glycidyl methacrylate monomers were released from all study groups. The amount of total monomer release except hydroxyethyl methacrylate was detected as greater in adhesive-precoated flash-free system. Among the study groups, the chemical cure group showed the highest hydroxyethyl methacrylate monomer release.

CONCLUSIONS

This in vitro study indicate that the APC flashless system exhibited the greatest release of residual monomers, suggesting that its possible cytotoxic effects need to be evaluated prior to clinical application.

CLINICAL RELEVANCE

This is the first study that evaluates the residual monomer release from adhesive-precoated flash-free brackets. The novel bracket system has a different mesh structure at the bracket base compared to traditional systems with different chemical components which might alter the amount of residual monomer release. To investigate the harmful effects of adhesives used in orthodontic applications is very important for the health of the patient and the orthodontist.

Bisphenol A Release from Fiber-Reinforced vs. Conventional Stainless-Steel Fixed Retainers: An In Vitro Study

OBJECTIVES

The objectives of this study were to investigate in vitro BPA release from two common fiberglass fixed lingual canine-to-canine retainers and to compare these amounts with those released from a conventional multistranded stainless-steel orthodontic retainer.

METHODS

Fifty-four recently extracted teeth were divided into groups of six teeth each, formed in an arch shape. Three different retainer types were evaluated: Ribbond, EverStick Ortho and Wildcut wire. Three identical specimens were constructed for each retainer type. BPA release was determined with validated the liquid chromatography-tandem mass spectrometry method at 1 and 24 h, as well as at 7, 14 and 30 days. The method's limits of detection and quantification were 0.32 ng/mL and 0.96 ng/mL, respectively. A two-way mixed, repeated-measures analysis of variance with Greenhouse-Geisser correction was employed to verify the existence of any significant differences.

RESULTS

Higher levels of BPA were released from the polyethylene fiber and glass fiber retainer in comparison with the conventional retainer in the present study. The differences between the systems over time were not statistically significant at the 95% confidence level.

CONCLUSIONS

In vitro BPA release during the first month did not differ between the examined retainer types. The highest BPA concentrations were observed at 1 month.

Myricetin Modulates Matrix Metalloproteinases Expression Induced by TEGDMA in Human Odontoblast-Like Cells

The activity of matrix metalloproteinases (MMPs) plays a crucial role in the aging of the resin-dentin interface. The in situ action of MMP-2 and MMP-9 has been confirmed in the process of dentin-collagen degradation. However, the involvement of dental pulp cells in MMP secretion as a response to oxidative stress induced by contact with resin monomers has not been fully elucidated. Myricetin (MYR), like proanthocyanidin (PAC), has antioxidant properties and may help prevent extracellular matrix degradation. The objective was to evaluate the effect of MYR on the MMP expression and activity in response to reactive oxygen species (ROS) increase induced by triethylene glycol dimethacrylate (TEGDMA) in human odontoblast-like cells (hOLCs). hOLCs differentiated from dental pulp mesenchymal stem cells were exposed to TEGDMA released from dentin blocks using a barrier model with transwell inserts for 18, 24, and 36 h. Intracellular oxidation was evaluated using the 2',7'-dichlorofluorescein probe. The effect of 600 μM MYR on the MMP-2 and MMP-9 expression was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The extracellular MMP levels were quantified using enzyme-linked immunosorbent assay, and their activation by means of a proteolytic fluorometric assay. The results were analyzed by one-way analysis of variance and Tukey's post hoc test, p ≤ 0.05. TEGDMA exposure increased intracellular ROS and upregulated MMP-2 and MMP-9 mRNA in hOLCs (p < 0.001). The levels of MMPs increased significantly 24 h after TEGDMA exposure (p = 0.013). These secreted proteases exhibited high activation ability. MYR reduced ROS production and downregulated MMP expression and activity at both mRNA and protein levels, similar to the effect found for PAC, which was used as a control. A relationship was observed between MMP-2 and MMP-9 expression, secretion, and early activation with ROS increase due to TEGDMA exposure. MYR showed potential as a therapeutic strategy to control MMP expression and modulate redox imbalance, offering a protective effect on cellular response.

Consideration of the work environment in a case of an industrial homeworker with allergic contact dermatitis by UV-curing acrylic resin

We report a case of an industrial homeworker diagnosed with allergic contact dermatitis by UV-curing acrylic resin for crafts. Approximately 2 months after a female in her 40s started producing handicrafts using resin, itchy desquamative erythema and vesicles occurred on her eyelids and palms. The course of the symptoms suggested that her dermatitis was occupational origin. Interviews regarding the work environment indicated that her employer did not adequately explain the hazards of resin. An inappropriate work environment may have led to the development of allergy. For industrial homeworkers, managing chemical exposures is predicted to be challenging. However, the expansion of the handmade market and the spread of craft resin increase opportunities for exposure to resin. In order to prevent the spread of health problems, appropriate information should be provided regarding the hazards of resin.

Scots Pine Bark Extracts as Co-Hardeners of Epoxy Resins

Extracts from natural waste like bark or leaves are great sources of phytochemicals, which contain functional groups (hydroxyl, carboxylic, vinyl, allyl) attractive in terms of polymer synthesis. In this study, the synthesis of epoxy with an extract of Scots pine bark as a natural co-hardener was evaluated. Ultraviolet-visible (UV-Vis) spectroscopy was used for the identification of phytochemicals with conjugated dienes and quantification of TPC. Also, the total solid content (TSC) of representative extracts was calculated. The best extract in terms of total phenolic content (TPC) value was selected as a co-hardener and investigated using differential scanning calorimetry (DSC) for thermal effects and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR) for reactions between functional groups. Also, the mechanical properties (flexural modulus, flexural strength, impact strength, Shore D hardness) and density of composition were obtained for extract-based epoxy and compared to reference sample values. Results were discussed in terms of future research and improvement of compositions. Also, potential applications were proposed.

Histological Evaluation of Polyacid-Modified Composite Resin and Conventional Composite Resin Used for Primary Molars Restoration

Background: The present study evaluated the histological outcomes of two dental restorative materials, polyacid-modified composite resin (compomer) and conventional composite resin, in the primary molars of puppies. Materials and Methods: Twenty sound primary molars in four puppies were used. The puppies were rendered unconscious using general anesthesia. Similar cylindrical Class V cavities were prepared in 16 of the 20 selected primary molars. The teeth were divided into three groups: Group I: Eight cavities were restored with compomer; Group II: Eight cavities were restored with conventional composite resin; Group III: Four teeth remained untreated and were used as controls. In Groups I and II, four teeth were examined histologically after 2 weeks and the other four after 6 weeks. The histological findings were analyzed and compared to determine the effects of each type of resin material on the dentine and the pulp. Results: At 6 weeks, the specimens tested for compomer showed obvious destructive changes in the central region and the region of the pulp adjacent to the cavity. The specimens tested for conventional composite resin revealed, at 6 weeks, massive destruction of the pulp tissues and abscess formation was observed. All the specimens tested in the control group showed normal cellularity, normal vascularity, and proper alignment of odontoblast cells. Conclusions: The teeth restored with compomer demonstrated more favorable pulpal reactions when compared with the teeth restored with conventional composite resin after 6 weeks.

Investigation of the biocompatibility of various pulp capping materials on zebrafish model

Testing the biocompatibility of commercially available dental materials is a major challenge in dental material science. In the present study, the biocompatibility of four commercially available dental materials Mineral Trioxide Aggregate, Biodentine, Harvard BioCal-CAP and Oxford ActiveCal PC was investigated. The biocompatibility analysis was performed on zebrafish embryos and larvae using standard toxicity tests such as survivability and hatching rates. Comparative toxicity analysis of toxicity was performed by measuring apoptosis using acridine orange dye and whole mount immunofluorescence methods on zebrafish larvae exposed to the dental materials at different dilutions. Toxicity analysis showed a significant decrease in survival and hatching rates with increasing concentration of exposed materials. The results of the apoptosis assay with acridine orange showed greater biocompatibility of Biodentine, Oxford ActiveCal PC, Harvard BioCal-CAP and Biodentine compared to MTA, which was concentration dependent. Consequently, this study has shown that showed resin-modified calcium silicates are more biocompatible than traditional calcium silicates.

Effectiveness of postprocessing on 3D printed resin biocompatibility in prosthodontics: A systematic review

STATEMENT OF PROBLEM

Additive manufacturing is used in prosthodontics for producing casts, surgical guides, and interim and definitive prostheses. Printed resin components that will be in contact with the oral mucosa must meet biocompatibility requirements in accordance with current standards for medical devices. Despite such approvals being obtained by the manufacturer, the dentist remains responsible for following the manufacturer recommendations. Evidence for the effect of postprocessing 3-dimensionally (3D) printed resin components on biocompatibility is lacking PURPOSE: The purpose of this systematic review was to assess the effectiveness of 3D printing postprocessing on the biocompatibility of resins that will be in contact with the oral mucosa.

MATERIAL AND METHODS

The PubMed, Scopus, and DOSS search engines were used to identify articles. Two independent researchers conducted the systematic review by following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines and by following a combination of keywords.

RESULTS

Of a total of 249 articles, 27 were selected, including only 1 in vivo study. Thirty-two commercially available and a few experimental resins were tested. The main applications were removable denture bases and denture teeth, interim and definitive fixed restorations, occlusal splints, and surgical guides. Postprocessing procedures were those recommended by the manufacturer, experimental, or not implemented and involving alcohol, ultrasonic or centrifugal rinsing, photopolymerization at different UV wavelengths, a nitrated atmosphere chamber with air drying or compressed air drying and with heat treatment. The majority of postprocessed 3D printed resins were reported to be noncytotoxic, implying sufficient biocompatibility.

CONCLUSIONS

The heterogeneity of materials and methods did not allow the identification of an ideal postprocessing protocol or of the need for additional steps after following the manufacturer's recommendations.

Surface alterations and compound release from aligner attachments in vitro

AIM

The aim of the present study was to assess the alterations in morphology, roughness, and composition of the surfaces of a conventional and a flowable composite attachment engaged with aligners, and to evaluate the release of resin monomers and their derivatives in an aqueous environment.

METHODS

Zirconia tooth-arch frames (n = 20) and corresponding thermoformed PET-G aligners with bonded attachments comprising two composite materials (universal-C and flowable-F) were fabricated. The morphological features (stereomicroscopy), roughness (optical profilometry), and surface composition (ATR-FTIR) of the attachments were examined before and after immersion in water. To simulate intraoral use, the aligners were removed and re-seated to the frames four times per day for a 7-day immersion period. After testing, the eluents were analyzed by LC-MS/MS targeting the compounds Bis-GMA, UDMA, 2-HEMA, TEGDMA and BPA and by LC-HRMS for suspect screening of the leached dental material compounds and their degradation products.

RESULTS

After testing, abrasion-induced defects were found on attachment surfaces such as scratches, marginal cracks, loss of surface texturing, and fractures. The morphological changes and debonding rate were greater in F. Comparisons (before-after testing) revealed a significantly lower Sc roughness parameter in F. The surface composition of the aligners after testing showed minor changes from the control, with insignificant differences in the degree of C = C conversion, except for few cases with strong evidence of hydrolytic degradation. Targeted analysis results revealed a significant difference in the compounds released between Days 1 and 7 in both materials. Insignificant differences were found when C was compared with F in both timeframes. Several degradation products were detected on Day 7, with a strong reduction in the concentration of the targeted compounds.

CONCLUSIONS

The use of aligners affects the surface characteristics and degradation rate of composite attachments in an aqueous environment, releasing monomers, and monomer hydrolysates within 1-week simulated use.

Bisphenol A release from CAD/CAM splint materials

This study aimed to investigate the bisphenol A (BPA) release from four CAD/CAM splint materials: three polycarbonate-based (DD BioSplint C, Splint Plus Biostar, Temp Premium Flexible) and one polymethylmethacrylate-based (Temp Basic) material. From each material, ten cylindrical samples (n = 40) were immersed in high-performance liquid chromatography (HPLC) grade water following ISO 10993-12 and incubated for 24 h in an incubation shaker at 37°C and 112 rpm. Following BPA derivatization, analysis was performed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). After 24 h of incubation, all investigated materials released significant amounts of BPA compared to water blanks. The material-dependent elution increased in the following order: DD BioSplint C < Splint Plus Biostar < Temp Basic < Temp Premium Flexible. Subtracting extraneous BPA, the concentrations ranged between 2.27 ng/mL and 12.65 ng/mL. After extrapolating the concentrations in relation to the average surface area of occlusal splints, the amount of BPA per mL exceeded the Tolerable Daily Intake (TDI) set by the European Union for a person weighing 70 kg by 1.32-6.16 times. Contrary to the release from previously investigated materials, BPA elution from CAD/CAM splint materials was highly elevated. Considering the increasing adaptation of CAD/CAM techniques, elution from them may represent a relevant BPA source in daily dental practice.

Contact allergies to dental materials in patients

BACKGROUND

Concerns regarding contact allergies and intolerance reactions to dental materials are widespread among patients. Development of novel dental materials and less frequent amalgam use may alter sensitization profiles in patients with possible contact allergy.

OBJECTIVES

To analyse current sensitization patterns to dental materials in patients with suspected contact allergy.

METHODS

This retrospective, multicentre analysis from the Information Network of Departments of Dermatology (IVDK) selected participants from 169 834 people tested in 2005-2019 and registered with (i) an affected area of 'mouth' (and 'lips'/'perioral'), (ii) with the dental material in question belonging to one of three groups (dental filling materials, oral implants or dentures or equivalents) and (iii) with patch-testing done in parallel with the German baseline series, (dental) metal series and dental technician series.

RESULTS

A total of 2730 of 169 834 tested patients met the inclusion criteria. The patients were predominantly women (81.2%) aged ≥ 40 years (92.8%). The sensitization rates with confirmed allergic contact stomatitis in women (n = 444) were highest for metals (nickel 28.6%, palladium 21.4%, amalgam 10.9%), (meth)acrylates [2-hydroxyethyl methacrylate (HEMA) 4.8%] and the substances propolis (6.8%) and 'balsam of Peru' (11.4%). The most relevant acrylates were HEMA, 2-hydroxypropyl methacrylate, methyl methacrylate, ethylene glycol dimethacrylate and pentaerythritol triacrylate. Few men were diagnosed with allergic contact stomatitis (n = 68); sensitization rates in men were highest for propolis (14.9%) and amalgam (13.6%).

CONCLUSIONS

Allergic contact stomatitis to dental materials is rare. Patch testing should not only focus on metals such as nickel, palladium, amalgam and gold, but also (meth)acrylates and the natural substances propolis and 'balsam of Peru'.

Digital manufacturing techniques and the in vitro biocompatibility of acrylic-based occlusal device materials

OBJECTIVES

Material chemistry and workflow variables associated with the fabrication of dental devices may affect the biocompatibility of the dental devices. The purpose of this study was to compare digital and conventional workflow procedures in the manufacturing of acrylic-based occlusal devices by assessing the cytotoxic potential of leakage products.

METHODS

Specimens were manufactured by 3D printing (stereolithography and digital light processing), milling, and autopolymerization. Print specimens were also subjected to different post-curing methods. To assess biocompatibility, a human tongue epithelial cell line was exposed to material-based extracts. Cell viability was measured by MTT assay while Western blot assessed the expression level of selected cytoprotective proteins.

RESULTS

Extracts from the Splint 2.0 material printed with DLP technology and post-cured with the Asiga Flash showed the clearest loss of cell viability. The milled and autopolymerized materials also showed a significant reduction in cell viability. However, by storing the autopolymerized material in dH2O for 12 h, no significant viability loss was observed. Increased levels of cytoprotective proteins were seen in cells exposed to extracts from the print materials and the autopolymerized material. Similarly to the effect on viability loss, storing the autopolymerized material in dH2O for 12 h reduced this effect.

CONCLUSIONS/CLINICAL RELEVANCE

Based on the biocompatibility assessments, clinical outcomes of acrylic-based occlusal device materials may be affected by the choice of manufacturing technique and workflow procedures.

Analysis of Resin-Based Dental Materials' Composition Depending on Their Clinical Applications

The objective of this study was to detail the monomer composition of resin-based dental materials sold in the market in 2023 and to evaluate the proportion of bisphenol A (BPA)-derivatives in relation to their applications. A search on manufacturers' websites was performed to reference resin-based dental materials currently on the European market (including the European Union (EU) and United Kingdom (UK). Their monomer composition was determined using material-safety data sheets and was completed by a search on the PubMed database. Among the 543 material compositions exploitable, 382 (70.3%) contained BPA derivatives. Among them, 56.2% contained BisGMA and 28% BisEMA, the most frequently reported. A total of 59 monomers, of which six were BPA derivatives, were found. In total, 309 materials (56.9%) contained UDMA and 292 (53.8%) TEGDMA. Less than one third of materials identified contained no BPA derivatives. These proportions vary a lot depending on their applications, with materials dedicated to the dental care of young populations containing the highest proportions of BPA-derivative monomers. The long-term effects on human health of the different monomers identified including BPA-derivative monomers is a source of concern. For children and pregnant or lactating women arises the question of whether to take a precautionary principle and avoid the use of resin-based dental materials likely to release BPA by opting for alternative materials.

Validation of a human saliva model for the determination of leachable monomers and other chemicals from dental materials

This study aimed to prove the validity of a mixture of chemicals, including salts, small organic molecules, mucin, and α-amylase, as saliva surrogate ("artificial saliva") for assessing leakage of methacrylate monomers and other constituents from dental materials. To achieve this, we developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), diurethane dimethacrylate (UDMA), bisphenol A glycerolate dimethacrylate (BisGMA), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), bisphenol A (BPA), and five homologues of ethoxylated bisphenol A dimethacrylate (BisEMA EO2-6) in unstimulated and artificial saliva, and compared their concentrations in the two saliva media following either spiking with a mixture of the compounds or incubation of test specimens of printed biomaterials. Test specimens were immersed in unstimulated/artificial saliva, incubated at 37 °C for 24 h, and saliva aliquots were extracted with methanol and subsequently analyzed by LC-MS/MS. The method was validated with regard to matrix effects, linearity, selectivity, lower limits of quantification (LLOQ), precision, bias and combined measurement uncertainty (u'). The performance characteristics of the method were comparable for unstimulated and artificial saliva samples. The combined u' for individual chemicals at a concentration of 10 × LLOQ were within the range of 5.3-14 % for unstimulated saliva and 6.9-16 % for artificial saliva, except for the BisEMA homologues. Combined u' for the latter were 27-74 % in unstimulated saliva, and 27-79 % in artificial saliva. There was no detectable release of BPA from the test specimens, and the TPO concentrations were mainly below the LLOQ. TEGDMA and UDMA were detected in the highest quantities, and at comparable concentrations in the unstimulated and artificial saliva. For all BisEMA homologues, the release was higher in unstimulated saliva than in artificial saliva. The study showed that the artificial saliva model can be a suitable replacement for native saliva, but might underestimate leakage of more lipophilic methacrylates.

Does Preheating Influence the Cytotoxic Potential of Dental Resin Composites?

Resin-based dental composites (RBC) release cytotoxic components, however the extent of the elution from preheated RBCs is barely investigated. The aim was therefore to determine the cytotoxic effect of preheated conventional, bulk, and thermoviscous RBCs of clinically relevant sizes using different cell viability methods in a contact-free model. Samples (6 × 4 mm) were prepared from conventional [Estelite Sigma Quick (ESQ), Filtek Z250 (FZ)] and bulk-filled [Filtek One BulkFill Restorative (FOB), SDR Plus Bulk Flow (SDR), VisCalor Bulk (VCB)] RBCs. The pre-polymerization temperature was set to room temperature (RT) and 55/65 °C. Pulp cells were cultured, followed by a 2-day exposure to monomers released from solid RBC specimens suspended in the culture medium. Cytotoxicity was assessed using a WST-1, MTT, and LDH colorimetric viability assays. Data were analyzed using one-way ANOVA, Tukey's post hoc test, multivariate analysis, and independent t-test. The effect size (ƞp2) of material and temperature factors was also assessed. All the RBCs demonstrated cytotoxic effect upon exposure to pulp cells, but to a varying extent (ESQ >> VCB > FZ = FOB = SDR). The effect of pre-polymerization temperature was insignificant (ƞp2 < 0.03), except for the thermoviscous RBC, which showed inconsistent findings when subjected to distinct viability tests. Cell viability was predominantly dependent on the type of material used (p < 0.001) which showed a large effect size (ƞp2 > 0.90). Irrespective of the pre-polymerization temperature, RBC samples in a clinically relevant size can release monomers to such an extent, which can substantially decrease the cytocompatibility.

Physical-Chemical and Microhardness Properties of Model Dental Composites Containing 1,2-Bismethacrylate-3-eugenyl Propane Monomer

A new eugenyl dimethacrylated monomer (symbolled BisMEP) has recently been synthesized. It showed promising viscosity and polymerizability as resin for dental composite. As a new monomer, BisMEP must be assessed further; thus, various physical, chemical, and mechanical properties have to be investigated. In this work, the aim was to investigate the potential use of BisMEP in place of the BisGMA matrix of resin-based composites (RBCs), totally or partially. Therefore, a list of model composites (CEa0, CEa25, CEa50, and CEa100) were prepared, which made up of 66 wt% synthesized silica fillers and 34 wt% organic matrices (BisGMA and TEGDMA; 1:1 wt/wt), while the novel BisMEP monomer has replaced the BisGMA content as 0.0, 25, 50, and 100 wt%, respectively. The RBCs were analyzed for their degree of conversion (DC)-based depth of cure at 1 and 2 mm thickness (DC1 and DC2), Vickers hardness (HV), water uptake (WSP), and water solubility (WSL) properties. Data were statistically analyzed using IBM SPSS v21, and the significance level was taken as p < 0.05. The results revealed no significant differences (p > 0.05) in the DC at 1 and 2 mm depth for the same composite. No significant differences in the DC between CEa0, CEa25, and CEa50; however, the difference becomes substantial (p < 0.05) with CEa100, suggesting possible incorporation of BisMEP at low dosage. Furthermore, DC1 for CEa0-CEa50 and DC2 for CEa0-CEa25 were found to be above the proposed minimum limit DC of 55%. Statistical analysis of the HV data showed no significant difference between CEa0, CEa25, and CEa50, while the difference became statistically significant after totally replacing BisGMA with BisMEP (CEa100). Notably, no significant differences in the WSP of various composites were detected. Likewise, WSL tests revealed no significant differences between such composites. These results suggest the possible usage of BisMEP in a mixture with BisGMA with no significant adverse effect on the DC, HV, WSP, and degradation (WSL).

Unveiling the mechanisms behind surface degradation of dental resin composites in simulated oral environments

Dental resin composites are widely used as restorative materials due to their natural aesthetic and versatile properties. However, there has been limited research on the degradation mechanisms of these composites in gastric acid environments, which would be common in patients with gastroesophageal reflux. This study aims to investigate the degradation behavior of dental composites immersed in simulated oral environments, including acid, saliva, and water. Mechanical and morphological properties of the composites, upon immersion in the simulated environments, were thoroughly examined using hardness testing and SEM imaging. Qualitative analyses of the ions leached from the polymer matrix and fillers were conducted using XPS and ICP-MS. In addition, the thermodynamic stability of the inorganic fillers of the composites in aqueous solutions across a wide range of pH values was theoretically studied through construction of Pourbaix diagrams. This study proposed a mechanism for composite leaching involving interactions between the matrix's hydrophilic groups and the aqueous immersion media, leading to swelling and chemical degradation of the composites. Furthermore, it was demonstrated that filler leaching was followed by ion exchange with Ca and P, resulting in the formation of hard calcified layers on the composite surface. The current findings provide valuable insights into the development of new composite materials with improved durability and resistance to degradation, especially for patients suffering from gastroesophageal reflux.

Evaluation of Physical-Chemical Properties of Contemporary CAD/CAM Materials with Chromatic Transition "Multicolor"

The use of materials for computer-aided design/computer-aided manufacturing (CAD/CAM) has been rapidly increasing in daily practice. However, one of the main issues regarding modern CAD/CAM materials is their aging in the oral environment, which may lead to significant changes in their overall properties. The aim of this study was to compare the flexural strength, water sorption, cross-link density (softening ratio%), surface roughness, and SEM analysis of three modern CAD/CAM "multicolor" composites. Grandio (Grandio disc multicolor-VOCO GmbH, Cuxhaven, Germany), Shofu (Shofu Block HC-Shofu Inc., Kyoto, Japan), and Vita (Vita Enamic multiColor-Vita Zahnfabrik, Bad Sackingen, Germany) were tested in this study. They were prepared in stick-shaped specimens and submitted to different tests after several aging protocols, such as thermocycling and mechanical cycle loading challenge. Further disc-shaped specimens were also created and tested for water sorption, cross-link density, surface roughness, and SEM ultramorphology, before and after storage in an ethanol-based solution. For flexural strength and ultimate tensile strength, Grandio showed the greatest values both at baseline and after aging (p < 0.05). Grandio and Vita Enamic presented the highest modulus of elasticity and the lowest water sorption (p < 0.05). A significant reduction (p < 0.05) in microhardness after ethanol storage (softening ratio%) was observed especially in Shofu. Grandio had the lowest roughness parameters compared to the other tested CAD/CAM materials, while ethanol storage significantly increased the Ra and RSm values in Shofu (p < 0.05). Despite the comparable modulus of elasticity of Vita and Grandio, this latter showed greater flexural strength and ultimate tensile strength both at baseline and after aging. Hence, Grandio and Vita Enamic may be employed for the anterior teeth and for those restorations requiring load-bearing capacity. Conversely, aging seems to affect several properties of Shofu, so its use for permanent restorations should be well-pondered based on the clinical situation.

Cytotoxicity and Microbiological Properties of Copolymers Comprising Quaternary Ammonium Urethane-Dimethacrylates with Bisphenol A Glycerolate Dimethacrylate and Triethylene Glycol Dimethacrylate

Using dental composite restorative materials with a copolymeric matrix chemically modified towards bioactive properties can help fight secondary caries. In this study, copolymers of 40 wt.% bisphenol A glycerolate dimethacrylate, 40 wt.% quaternary ammonium urethane-dimethacrylates (QAUDMA-m, where m represents 8, 10, 12, 14, 16 and 18 carbon atoms in the N-alkyl substituent), and 20 wt.% triethylene glycol dimethacrylate (BG:QAm:TEGs) were tested for (i) cytotoxicity on the L929 mouse fibroblast cell line; (ii) fungal adhesion, fungal growth inhibition zone, and fungicidal activity against C. albicans; and (iii) bactericidal activity against S. aureus and E. coli. BG:QAm:TEGs had no cytotoxic effects on L929 mouse fibroblasts because the reduction of cell viability was less than 30% compared to the control. BG:QAm:TEGs also showed antifungal activity. The number of fungal colonies on their surfaces depended on the water contact angle (WCA). The higher the WCA, the greater the scale of fungal adhesion. The fungal growth inhibition zone depended on the concentration of QA groups (x_QA). The lower the x_QA, the lower the inhibition zone. In addition, 25 mg/mL BG:QAm:TEGs suspensions in culture media showed fungicidal and bactericidal effects. In conclusion, BG:QAm:TEGs can be recognized as antimicrobial biomaterials with negligible biological patient risk.

A Pilot Study on Monomer and Bisphenol A (BPA) Release from UDMA-Based and Conventional Indirect Veneering Composites

This study aimed to investigate the release of common monomers from conventional (Dialog Vario, Enamel Plus HFO) and UDMA-based indirect veneering composites (VITA VM LC, GC Gradia). Ten cylindrical samples of each material were prepared (n = 40), immersed in HPLC grade water, and incubated for 24 h in an incubation shaker at 37 °C and 112 rpm. Extraction was performed following ISO 10993-12 and monomers were detected and quantified by HPLC-MS/MS. In all the samples, urethane dimethacrylate (UDMA) and bisphenol A (BPA) were quantifiable. Compared to water blanks, BPA levels were only elevated in the eluates from conventional composites. In all other samples, concentrations were in the range of extraneous BPA and were therefore clinically irrelevant. Low concentrations of Bisphenol A-glycidyl methacrylate (BisGMA) were found in one BPA-free composite and in both conventional materials. Statistical analyses showed that BPA-free materials released significantly less BisGMA and no BPA, while UDMA elution was comparable to elution from conventional materials. All measured concentrations were below reported effective cytotoxic concentrations. Considering these results, the substitution of BPA-derivatives with UDMA might be beneficial since BPA-associated adverse effects are ruled out. Further studies should be enrolled to test the biocompatibility of UDMA on cells of the oral environment.

The Cytotoxicity and Genotoxicity of Bioactive Dental Materials

The promotion of biologically based treatment strategies in restorative dentistry is of paramount importance, as invasive treatments should be avoided to maintain the tooth's vitality. This study aimed to assess the biocompatibility of commercially available bioactive materials that can be used for dental pulp capping. The study was performed with a monocyte/macrophage peripheral blood SC cell line (ATCC CRL-9855) on the following six specific bioactive materials: ProRoot MTA (Dentsply Sirona), MTA Angelus (Angelus), Biodentine (Septodont), TheraCal LC (Bisco), ACTIVA BioACTIVE (Pulpdent) and Predicta Bioactive Bulk (Parkell). The cytotoxicity of the investigated agents was measured using a resazurin-based cell viability assay, while the genotoxicity was evaluated using an alkaline comet assay. Additionally, flow cytometry (FC) apoptosis detection was conducted with a FITC (fluorescein isothiocyanate) Annexin V Apoptosis Detection Kit I. FC cell-cycle arrest assessment was carried out with propidium iodide staining. The results of this study showed no significant cytotoxicity and genotoxicity (p > 0.05) in ProRoot MTA, MTA Angelus, Biodentine, ACTIVA BioACTIVE and Predicta Bioactive. Conversely, TheraCal LC presented a significant decrease (p < 0.001). In conclusion, due to excellent biocompatibility and low cytotoxicity, MTA, Biodentine, ACTIVA BioACTIVE and Predicta Bioactive may be suitable for pulp capping treatments. On the other hand, due to the high cytotoxicity of TheraCal LC, its use should be avoided in vital pulp therapies.

Pierre Robin Sequence and 3D Printed Personalized Composite Appliances in Interdisciplinary Approach

This paper introduces a complex novel concept and methodology for the creation of personalized biomedical appliances 3D-printed from certified biocompatible photopolymer resin Dental LT Clear (V2). The explained workflow includes intraoral and CT scanning, patient virtualization, digital appliance design, additive manufacturing, and clinical application with evaluation of the appliance intended for patients with cranio-facial syndromes. The presented concept defines virtual 3D fusion of intraoral optical scan and segmented CT as sufficient and accurate data defining the 3D surface of the face, intraoral and airway morphology necessary for the 3D design of complex personalized intraoral and extraoral parts of the orthopedic appliance. A central aspect of the concept is a feasible utilization of composite resin for biomedical prototyping of the sequence of marginally different appliances necessary to keep the pace with the patient rapid growth. Affordability, noninvasiveness, and practicality of the appliance update process shall be highlighted. The methodology is demonstrated on a particular case of two-year-old infant with Pierre Robin sequence. Materialization by additive manufacturing of this photopolymer provides a highly durable and resistant-to-fracture two-part appliance similar to a Tübingen palatal plate, for example. The paper concludes with the viability of the described method and material upon interdisciplinary clinical evaluation of experts from departments of orthodontics and cleft anomalies, pediatric pneumology and phthisiology, and pediatric otorhinolaryngology.