Effects of Monomer Composition of Urethane Methacrylate Based Resins on the C=C Degree of Conversion, Residual Monomer Content and Mechanical Properties

(1) Background: This study investigated the influence of Bis-GMA, TEGDMA, UDMA, and two different polyethylene glycol (PEG)-containing, UDMO-based co-monomers on the Young’s modulus and flexural strength, degree of methacrylate C=C double bond conversion and residual monomer elution of experimental dental resins. (2) Methods: Urethane methacrylate-based monomer was synthesised via a radical chain growth polymerization mechanism using PEG in order to improve the mechanical properties. Dental resins were formulated using Bis-GMA, UDMA, or UDMO as base monomers combined with TEGDMA as a dilution monomer and DMAEM + CQ as the photo-initiator system. Degree of conversion (DC), mechanical properties, and residual monomer content of light-activated methacrylate resin formulations were evaluated and statistically analysed by ANOVA and a Tukey’s test. (3) Results: PEG-containing UDMO resins had lower Young’s modulus and elastic strength than UDMA-derived resin for all irradiation times. The highest DC (67,418%) was observed for the PEG-containing UDMO-based resin formulation when light cured for 40 s. For all samples, DC increased with the photo-polymerization time. The amount of residual monomer decreased after increasing the light-curing period from 20 to 40 s, resin with UDMO content 0.01 mol of PEG having the smallest amount of free eluted monomer. (4) Conclusions: A strong structure–property relationship exists in photo-cured dimethacrylate-based dental resins. The time and quantity of the photochemical initiation system can influence the physical–mechanical properties of the resins but also the monomers in their composition.

CONDITIONAL TISSUE CONDITION IN PATIENTS WITH PROSTHETIC DENTISTS IN THE PROCESS OF ORTHOPEDIC TREATMENT WITH PROSTHESES MODIFIED BY NANOMATER

The main cause of prosthetic stomatitis belongs to the chemical and toxic action of the residual monomer of the prosthesis base, which is a protoplasmic poison. Occurrence of prosthetic stomatitis depends not only on quality of production of prosthesis in laboratory though at non-observance of technology indicators of residual monomer can reach 2-5%, but also at individual intolerance at its minimum concentration in a prosthesis after polymerization - 0,2-0 .5%. The aim of our study was to increase the effectiveness of orthopedic treatment of patients with prosthetic stomatitis by coating the plastic of removable prostheses with nanoscale materials. Materials and methods. To solve this goal, we studied the condition of the tissues of the prosthetic place of patients with prosthetic stomatitis with prosthetic removable prostheses with modified plastic. Orthopedic dental treatment of 50 people was examined and performed, including 25 people (the second group, prostheses were not covered with nanoparticles) and 25 people (the third group, prostheses were covered with nanoparticles). The first control group consisted of 10 people without signs of pathology. Prior to treatment, all patients had removable acrylic plastic dentures. The reason for seeking orthopedic care was a violation of masticatory function and the inability to use previously made prostheses due to the development of pain in the soft tissues of the prosthetic place. Complaints of pain were observed in all patients of varying intensity, impaired fixation and stabilization of the prosthesis due to swelling of the mucous membrane of the soft tissues of the prosthetic place, heartburn and dryness were observed in 90% of patients. Complaints were also about speech and aesthetic defects. Patients of III group after two weeks of using prostheses were coated with the inner surface of the prosthesis, which is in direct contact with the mucous membrane of the prosthetic place with molecules of fullerene C60, by magnetron sputtering. For this purpose, the prostheses were removed from the patients for several days and returned after the coating with the nanomaterial, after which the observation was continued. The results. After coating the prostheses in patients of group III with Fullerene C60, we observed the disappearance of inflammation of the mucous membrane under the prosthesis and patients noted the absence of discomfort. Рatients in II group had a negative dynamics in 80% and had diffuse inflammation of the mucous membrane under the prosthesis. Within 3 months of use, 18 patients (72%) in II group reported that they stopped using removable dentures during the day, due to unpleasant pain under the prosthesis, and used only during meals and during conversations. In contrast to II group, patients in III group did not notice discomfort when using plate prostheses. Conclusions. Obtained in the course of the work convincingly prove the effectiveness of the use of removable plate prostheses with nanocoating for the treatment and prevention of prosthetic stomatitis in patients. This is evidenced by the data of objective examination and the disappearance of complaints from patients.

Characteristics of Dental Resin-Based Composites in Leukemia Saliva: An In Vitro Analysis

Background: The aim was to analyze, in vitro, four resin based composite systems (RBCs) immersed in saliva of leukemia patients before starting chemotherapy regiments. Material and methods: Saliva was collected from 20 patients (4 healthy patients, 16 leukemia patients). Resin disks were made for each RBC and were immersed in the acute leukemia (acute lymphocytic (ALL), acute myeloid (AML)), chronic leukemia (chronic lymphocytic (CLL), chronic myeloid (CML)), Artificial saliva and Control environment, and maintained for seven days. At the end of the experiment, the characteristics and the effective response of saliva from the studied salivas’ on RBCs was assessed using water sorption, water solubility, residual monomer and scanning electron microscopy (SEM). Data analysis was performed and a p-value under 0.05 was considered statistically significant. Results: The behaviour of RBCs in different immersion environments varies according to the characteristics of the RBCs. RBCs with a higher filler ratio have a lower water sorption. The solubility is also deteriorated by the types of organic matrix and filler; the results of solubility being inversely proportional on the scale of negative values compared to sorption values. Chromatograms of residual monomers showed the highest amount of unreacted monomers in ALL and AML, and the Control and artificial saliva environments had the smallest residual monomer peaks. Because of the low number of differences between the experimental conditions, we further considered that there were no important statistical differences between experimental conditions and analysed them as a single group. Conclusion: The influence of saliva on RBCs depends on the type of leukemia; acute leukemia influenced the most RBCs by changing their properties compared to chronic leukemia.

Research on the Mechanical Properties, Fluoride and Monomer Release of a New Experimental Flowable Giomer in Comparison to Three Commercial Flowable Giomers

Giomers are hybrid dental materials with controlled fluoride release properties. The aim of this study was to characterise a new experimental flowable giomer (G) in comparison to three commercial flowable giomers: Beautifil flow Plus X F00 (B-F00), Beautifil flow F02 (B-F02) and Beautifil flow Plus X F03 (B-F03), Shofu, Kyoto, Japan. The studied properties are fluoride ion release, residual monomers release and mechanical properties. The data analysis was performed using the ANOVA test and Tukey test for post hoc comparisons between groups. During the first day of the fluoride releasing measurement, the following classification resulted: B-F02 ˃ B-F03 ˃ B-F00 ˃ G and at the end of the investigation period, at 60 days: B-F02 ˃ B-F03 ˃ G ˃ B-F00. The experimental giomer released a lower percentage of total residual monomers than the commercial giomers. The highest value for the mechanical properties was recorded for the commercial giomers. The experimental giomer registered the lowest values for mechanical properties but higher than the imposed standard limit. There were statistically significant differences between the analyzed materials, in terms of fluoride releasing, residual monomer releasing and mechanical properties.

Effect of Polymerization Time on Residual Monomer Release in Dental Composite: In Vitro Study

Light activated resin-based composites are the most accepted and used materials among clinicians. The aim of this study is to determine the amount of residual monomer released from nanofiller composite resins for different polymerization times and storage periods in vitro. To this purpose, Tetric Ceram (Ivoclar, Liechtenstein), Clearfil Majesty Posterior (Kuraray, Japan), Grandio (VOCO, Germany), and Filtek Ultimate Universal (3M, USA) were used as nanofiller resin composites samples. Four groups ( n = 40 , diameter: 5 mm, thickness: 2 mm) of each material were fabricated, and each group was exposed to three different polymerization time (10, 20 and 40 sec). High-performance liquid chromatography (HPLC) was used to measure the amount of monomers released over 1, 15, and 30 days. The highest amount of monomer release was seen in Tetric EvoCream composite, while the least monomer release was seen in Clearfil Majesty composite. Regardless of the polymerization time, material, or storage period, the highest amount of eluted monomer was Bis-GMA. It is observed that there is no statistically significant difference between various polymerization times. Monomer release reached its highest level on the 15th day and decreased on the 30th day for all composites. Polymerization time did not affect the monomer release from the composites, but the type of the monomers and concentration of the filler used in the composites affected the amount of released monomers. The use of TEGDMA (co)monomer reduced the monomer release.

Development of a Promising Method for Producing Oligomeric Mixture of Branched Alkylene Guanidines to Improve Substance Quality and Evaluate Their Antiviral Activity against SARS-CoV-2

This paper reports the synthesis of branched alkylene guanidines using microfluidic technologies. We describe the preparation of guanidine derivatives at lower temperatures, and with significantly less time than that required in the previously applicable method. Furthermore, the use of microfluidics allows the attainment of high-purity products with a low residual monomer content, which can expand the range of applications of this class of compounds. For all the samples obtained, the molecular-weight characteristics are calculated, based on which the optimal condensation conditions are established. Additionally, in this work, the antiviral activity of the alkylene guanidine salt against the SARS-CoV-2 virus is confirmed.

The Effect of Chitosan Addition in Acrylic Resin Matrix towards the Residual Monomers and Impact Strength

Background: A residual monomer might have impact on the quality of acrylic resin since its caused allergic reactions and inflammation. Chitosan is a biocompatible material and potential to reduce residual monomers and ameliorate the impact strength of acrylic resin Objective of the study: To examine the effect of an acrylic resin matrix mixed with chitosan together with 1% and 2% acrylic acid as denture base and orthodontic material on residual monomers and impact strength. Methodology: There were 30 samples for the test analysis. The impact strength test sample formed with a plate size of 55 × 10 × 10mm, whereas the residual monomer test sample was prepared into powder. The test samples were divided into 3 groups, of 10 samples. Group 1 acrylic resin only, group 2 acrylic resin matrix mixed with chitosan and 1% acrylic acid, group 3 is the same as group 2 but with a concentration of 2% acrylic acid. Gas chromatography was used for measuring the residual monomers. The impact strength was tested by the Charpy impact. The data was evaluated using the ANOVA and correlation test. Results: There were significant differences (p < 0.05) in acrylic resin without addition with the matrix of acrylic resin with chitosan and acrylic acid 1% and 2% to the number of monomers and impact strength. Conclusion: The mixture of acrylic resin with chitosan and acrylic acid 1% and 2% can reduce the amount of residual monomer and increase the impact strength.

POSSIBILITIES FOR MODIFICATION OF SURGICAL OBTURATOR INTO TEMPORARY OBTURATOR

Background: Maxillary resection causes different types of damages in the maxillofacial area, which are treated by surgical and prosthetic restorative methods. Aim: The described clinical case follows up the initial stages of the prosthetic treatment, as well as the possible modification of surgical obturator into temporary obturator in a patient with maxillary resection. Materials and methods: The prosthetic treatment of a 55-years-old female patient with a surgical operation of upper jaw cancer is described. The surgical obturator is developed a week after the resection. The preliminary impressions are taken with irreversible hydrocolloid impression material. The occlusion height and central relation are fixed by occlusion rims. The surgical obturator was fabricated by heat cured acrylic resin with a low amount of residual monomer. Moreover, metal clasps were used for retention and stability. The borders of the obturating part were covered with a thin layer of relining silicone material after the adjustment. The surgical obturator was modified into a temporary one directly in the patient's mouth after two months by applying the same rebasing material and designing a silicone hollow-bulb obturating part. Results: The treatment results revealed a successful restoration of the patient's speaking, feeding, and swallowing abilities. The application of silicone material inhibited the appearance of decubitus ulcers and facilitated the normal healing process. The direct design of hollow-bulb silicone obturating part significantly improved the retention and stability of the obturator. Conclusion: The application of prosthetic treatment methods in the first days after the maxillary resection allows for restoration of speaking and feeding.