Methacrylate-based Dental Composites Research Articles

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.

Effects of Water Sorption and Solubility on Degradation of Silorane and Methacrylate-Based Dental Composites.

Wet oral environment may have deleterious effects on performance of the composites due to influences of water sorption and solubility. The study evaluated the hydrolytic degradation caused because of water sorption and solubility of silorane and methacrylate-based dental composites. Ten disc samples (2 mm × 10 mm) were prepared. Samples were analyzed for water solubility and sorption according to ISO 4049:2000 regulations and tested for mass gain or loss following immersion in water or in artificial saliva at 1 day, 15 days, and 30 days period. Student's 't' test, repeated measures analysis of variance (ANOVA), and Tukey's post-hoc tests determined statistical significance of the experimental results with global significance set at P = 0.05. Considerable sorption and solubility was observed with time in both materials on immersion. Silorane composites showed lower water sorption and solubility than methacrylate-based composite (MBC). Artificial saliva demonstrated higher sorption and solubility compared to distilled water. Silorane composites display enhanced hydrolytic stability even after a month of immersion in contrast to conventional methacrylate-based composites (MBCs), making it a better alternative to MBC resins clinically.

Evaluation of allyl sulfides bearing methacrylate groups as addition-fragmentation chain transfer agents for low shrinkage dental composites

Polymerization shrinkage and the consequential shrinkage stress in methacrylate-based dental composites are crucial drawbacks for restorative dentistry. An effective way for the reduction of shrinkage stress is the incorporation of addition fragmentation chain transfer agents (AFCT agents). In this contribution, four novel polymerizable allyl sulfides were synthesized and evaluated in dental composites. Photo-DSC and DMTA measurements were performed to evaluate their influence on the polymerization rate and on the network homogeneity. Good to excellent shrinkage force values and mechanical properties were obtained for all AFCT based composites. Especially, the incorporation of AFCT agents containing multiple urethane and methacrylate moieties improved the mechanical properties. Hence, the incorporation of polymerizable and urethane-based allyl sulfides in dental composite is a promising strategy to obtain low shrinkage materials exhibiting high flexural strength and modulus.

Mesoporous silica aerogel reinforced dental composite: Effects of microstructure and surface modification

A mesoporous silica aerogel (SiA) with a high specific surface area was synthesized through the sol-gel process and subsequently modified with two different silane-based modifiers to reveals the effect of microstructure and surface modification on the fracture mechanics of a dental composite. The synthesized and modified aerogel were characterized using field-emission scanning electron microscopy (FESEM), nitrogen adsorption-desorption, and Fourier-transform infrared spectroscopy (FTIR). The prepared aerogels were then incorporated within methacrylate-based dental composites with the filler content of 0–35 wt%. Flexural modulus (FM) and Flexural strength (FS) were evaluated by the three-point bending test. The fracture toughness (FT) of the composites was evaluated by single edge V-notched beam (SEVNB) flexure test, while FESEM was employed to investigate the fracture surface morphology of the composites. Furthermore, the wettability of the composites was assessed according to the sessile drop method. The characterization of synthesized aerogels revealed the formation of SiA with a surface area of 550–560 m2/g and porosity of 77%, while FTIR results confirmed the successful modification. Statistical analysis (ANOVA, p≤0.05, and n = 5) revealed that FM significantly enhanced (from 1.43 GPa to 2.66 GPa) as filler content increased over 0–30 wt%, and FS improved (from 80 to 95 MPa) as filler content increased over 0–15 wt%. Furthermore, the modification of aerogels improved both fracture characteristics and the wettability of the composites. The FT evaluations and fractography analysis revealed that the mesoporous structure of the fillers mainly dominated the filler-matrix adhesion strength at the same filler content.

Cytotoxicity of Silorane and Methacrylate based Dental Composites on Human Pulp Cells

Introduction: The ingredients from the dental restoratives are known to leach and elicit a host response. The prerequisite to deem a material biocompatible requires its toxicologic evaluation. The study was performed to analyze the probable toxicity resulting from silorane-based composite (SBC) with methacrylate-based composite (MBC). Materials and Methods: The in vitro cytotoxicity test, methyl thiazolyl tetrazolium (MTT) assay, evaluated the cell viability and proliferation rate of dental pulp cells (DPCs). The extirpated pulp was cultured in α-MEM-containing supplements and incubated at 37°C. DPCs were subjected to varying doses of SBC or MBC at different time intervals after attaining confluence and monitored for proliferation and viability via MTT assay. An independent Student t test was performed to compare the effect of composites on the DPC. The cytotoxicity levels were compared using one-way analysis of variance and posthoc Tukey multiple comparison test at 5% level of significance and P-value of 90%) in the first 24 hours. The count significantly reduced by the end of 48 hours (minimum 65% in 25 μg/ml) at all concentrations (P

Synthesis and polymerization of vinylcyclopropanes bearing urethane groups for the development of low-shrinkage composites

Polymerization shrinkage of methacrylate-based dental composites remains a major concern in restorative dentistry. Cyclic monomers, such as 1,1-disubstituted 2-vinylcyclopropanes, might represent an interesting alternative to dimethacrylates in order to reduce shrinkage. In this contribution, the synthesis of seven crosslinking vinylcyclopropanes bearing urethane groups is described. These monomers were synthesized by esterification of 1-ethoxycarbonyl-2-vinylcyclopropane-1-carboxylic acid with either ethylene glycol or diethylene glycol, followed by a reaction with selected diisocyanates. In order to evaluate the reactivity of the synthesized vinylcyclopropanes, their photopolymerization behavior was investigated by photo-differential scanning calorimetry. Real-time (RT)-NIR-photorheology measurements were performed to evaluate rheological behavior (i.e. time of gelation, polymerization induced shrinkage force) and chemical conversion (i.e. double bond conversion at the gel point, final double bond conversion) of the vinylcyclopropanes in situ. Composites based on these monomers show good to excellent mechanical properties and exhibit low shrinkage. The presence of urethane groups provides a significant improvement of the mechanical properties. The replacement of methacrylates by urethane vinylcyclopropanes appears to be a promising approach to develop low-shrinkage dental composites without sacrificing the mechanical properties.

A comparative evaluation of microleakage of restorations using silorane-based dental composite and methacrylate-based dental composites in Class II cavities: An in vitro study.

Aim:The aim of this in vitro study was to evaluate and compare the microleakage of restorations using low shrinkage silorane-based dental composite and methacrylate-based dental composites in Class II cavity at the occlusal and gingival margins.Materials and Methods:Sixty mandibular molars were collected and divided into three experimental groups and one negative control group. Class II slot cavity was prepared on the mesial surface. Experimental groups were restored with Group I: silorane-based microhybrid composite, Group II: methacrylate-based nanohybrid composite, and Group III: Methacrylate-based microhybrid composite, respectively. Group IV: negative control. The samples were thermocycled, root apices were sealed with sticky wax and coated with nail varnish except 1 mm around the restoration. This was followed by immersion in 2% Rhodamine-B dye solution under vacuum at room temperature for 24 h. Then, the samples were sectioned longitudinally in the mesiodistal direction and evaluated under stereomicroscope ×40 magnification. Scoring was done according to the depth of dye penetration in to the cavity. Statistical analysis of the data was done.Results:The results were that no statistically significant difference in the microleakage at the occlusal margin for all the restorative materials, whereas at the gingival margin, silorane-based microhybrid composite showed less microleakage than the methacrylate-based nano- and micro-hybrid composites.Conclusion:In general, silorane-based microhybrid composite had less microleakage among the other materials used in this in vitro study.

Evaluation of Cytotoxicity of Silorane and Methacrylate based Dental Composites using Human Gingival Fibroblasts.

The effects of leached substances from the restorative dental materials may induce local and systemic adverse effects. Thus the biological and toxic properties of the restorative dental materials must be compatible with the oral tissues or with general health. Therefore, the need for biocompatible restorative dental material implies the necessity of toxicity testing. It was the purpose of this investigation to determine and compare the possible toxic effect of silorane based composite (Filtek P90) on human gingival fibroblast (HGF) in vitro using cytotoxicity measuring parameters (MTT assay) in comparison with its methacrylate counterpart (Z100) for their viability, proliferation rate. Fresh healthy biopsy specimens of human gingival tissue of patients were obtained. For HGF, cells were cultured in Dulbecco's modified Eagle medium and grown to sub confluent monolayers. After attaining confluence, cells were treated with different doses of the Filtek P90 or Z 100 for different time point. HGF cells were observed for their proliferation, viability by MTT assay. The results of the cytotoxicity assay showed that, the percentage of viable cells was very good in the first 24h and marginally decreased in the next 48h period in all groups. However, the proliferation rate was never below 84% in all the groups, at any given concentration. Filtek P90 and Z100 treated cells exhibited insignificant decrease in the cell proliferation both in 24h and 48h exposure when compared to significant decrease in the cell survival rate in the positive control (Mitomycin C 250 μg/ml).) Comparison of the toxicity between Filtek P90 and Z100 in 24h & 48h separately showed that there was no significant difference (p<0.05) between these two composites in 24h and 48h' time period at all concentrations of the composites. To conclude, the new silorane based restorative composite showed comparable cytotoxic characteristics to clinically successful dimethacrylate composites suggesting the non-toxic nature in the oral environment and hence contributing to clinical success of these new restorative materials.

Comparison of Various Properties of a Silorane Based Dental Composite with Two Methacrylate Based Dental Composites

AbstractThe synthesis of a new monomer system named silorane (obtained from the reaction of oxirane and siloxane molecules) gave way to the production of a novel low shrinkage silorane based composite. Objectives: The purpose of this study was to compare some physical properties of a silorane based composite (Filtek Silorane, 3MESPE) to those of two well-known low shrinkage methacrylate-based composites (Filtek Supreme XT, 3MESPE; Esthet X HD, Dentsply). The study also includes the effect of external media (food simulating solutions; distilled water, artificial saliva, 25% ethanol, coconut oil and Coke) on the three composites. Methods: Cured samples underwent water absorption (with immersion in food simulating solutions) and desorption. The data were analysed; the water absorption and desorption profiles were mapped, the diffusion coefficients and solubility of each sample were calculated. Curing efficiency was measured on the top and bottom surfaces of cured composite samples using Fourier Transform Infrared (FTIR) spectroscopy. Finally, the temperature profile during polymerisation of each composite sample was mapped, allowing the calculation of the sample‘s maximum exotherm. Results: From the results obtained from these experiments, overall, the properties of Filtek Silorane are comparable with those of Filtek Supreme XT and Esthet X HD.

Comparison of Various Properties of a Silorane Based Dental Composite with Two Methacrylate Based Dental Composites

Comparison of Various Properties of a Silorane Based Dental Composite with Two Methacrylate Based Dental Composites

Silorane-기질 치아 수복용 복합레진의 중합수축과 중합수축응력

본 연구의 목적은 silorane 기질의 치아 수복용 복합레진의 중합수축과 수축응력의 동력학을 평가하고 전통적인 methacrylate 기질의 복합레진과 비교하기 위함이다. 두 종의 methacrylate 기질의 복합레진(Z250, Z350 flowable)과 silorane 기질 복합레진(P90)이 사용되었다. 아르키메데스 원리를 응용해 자체 제작한 중합수축 측정 장치를 사용하여 광중합 중 일어나는 복합레진의 체적 중합수축을 측정하였고 스트레인게이지로 중합수축응력을 측정하였다. Silorane 기질 복합레진인 P90의 중합수축과 최대 중합수축률이 가장 낮았고 methacrylate 기질 복합레진인 Z350 flowable이 가장 높았다. Methacrylate 기질의 복합레진과 비교하여 silorane 기질의 복합레진 P90이 최대 수축률에 이른 시간은 더 길었고 중합수축응력은 낮았다. The purpose of this study was to measure the volumetric polymerization shrinkage kinetics and stress of a silorane-based dental restorative composite and compare it with those of conventional methacrylate-based dental composites. Two methacrylate-based composites (Z250, Z350 flowable) and one silorane-based composite (P90) were investigated. The volumetric polymerization shrinkage of the composites during light curing was measured using a laboratory-made volume shrinkage measurement instrument based on the Archimedes' principle, and the polymerization stress was also determined with the strain gage method. The shrinkage of silorane-based composites (P90) was the lowest, and that of Z350 flowable was the highest. Peak polymerization shrinkage rate was the lowest in P90 and the highest in Z350 flowable. The time to reach peak shrinkage rate of P90 was longer than those of the methacrylate-based composites. The polymerization shrinkage stress of P90 was lower than those of the methacrylate-based composites.

The Noise in Measurements of Degree of Conversion of (Meth)Acrylates by FTIR-ATR

Noise frequently appears on FTIR-ATR spectra of a cured (meth)acrylic material during determination of its double bond conversion. The goals of this work were to investigate the source of the noise and to find an effective way to reduce it. Two methacrylate-based dental composites, one unfilled methacrylate resin blend, and one acrylate resin system were used as the materials to be tested. Uncured and visible light cured specimens were mounted on an FTIR-ATR and their IR spectra were taken. The characteristics of the spectra were analyzed along with those of other solids and liquids. It was found that the origin of the noise is IR absorption bands of water adsorbed on the surface of the solid specimens. Among several remedies, digital subtraction of the water absorption baseline is demonstrated to be a flexible, easy-to-implement, and time-saving method to reduce or even eliminate the noise of the sample spectrum. Noise reduction improves the quality of FTIR-ATR spectra and makes the measurement of double bond conversion more accurate.