Release Of Monomers Research Articles

Pre-Heating Effect on Monomer Elution and Degree of Conversion of Contemporary and Thermoviscous Bulk-Fill Resin-Based Dental Composites

Detection of unreacted monomers from pre-heated resin-based dental composites (RBC) is not a well-investigated topic so far. The objectives were to determine the temperature changes during the application and polymerization, the degree of conversion (DC) and unreacted monomer elution of room temperature (RT), and pre-heated thermoviscous [VisCalor Bulk(VCB)] and high-viscosity full-body contemporary [Filtek One Bulk(FOB)] bulk-fill RBCs. The RBCs’ temperatures during the sample preparation were recorded with a K-type thermocouple. The DC at the top and bottom was measured with micro-Raman spectroscopy and the amounts of eluted BisGMA, UDMA, DDMA, and TEGDMA were assessed with High-Performance Liquid Chromatography. The temperatures of the pre-heated RBCs decreased rapidly during the manipulation phase. The temperature rise during photopolymerization reflects the bottom DCs. The differences in DC% between the top and the bottom were significant. RT VCB had a lower DC% compared to FOB. Pre-heating did not influence the DC, except on the bottom surface of FOB where a significant decrease was measured. Pre-heating significantly decreased the elution of BisGMA, UDMA, DDMA in the case of FOB, meanwhile, it had no effect on monomer release from VCB, except TEGDMA, which elution was decreased. In comparison, RBC composition had a stronger influence on DC and monomer elution, than pre-cure temperature.

Physico-chemical properties and biocompatibility of in situ-hardening polylactide/nano hydroxyapatite composite for bone substitute

Polylactide (PLA) and hydroxyapatite (HA) composite is a promising material for biomedical applications. The bioresorbability and adequate strength of PLA in combination with the bioactivity of HA clearly provide prospective properties for resorbable bone substitute. The material, however, requires to be shaped prior to surgery, which impedes its practical use, particularly in complex shaped bone defects. In this study, a novel combination of star-shaped and linear PLA powder with various amounts of nano HA, and triethylene glycol dimethacrylate liquid was developed as an in situ forming cement for bone substitute. The effects of different amounts of initiator (0.5 and 1 wt%) and nano HA powder (5, 10, and 15 wt%) on various properties of the composite cement, including handling properties, degree of conversion, gel fraction, residual monomer toxicity and osteoblast differentiation were studied. The in vitro degradation was also examined in terms of weight and mechanical loss. The results demonstrated that the amount of initiator had a great effect on the handling properties of the cement, however, the HA content did not have any significant effect. The increasing HA content slowed down the degradation rate of the cement. All cement formulations in this study exhibited good network forming and ability to induce osteoblast differentiation with negligible residual monomer release to harm cells. The optimal cement formulation was found to be at 15 wt% HA, which allowed for in situ hardening with satisfactory biocompatibility and mechanical support for bone regeneration during deterioration.

The effects of polymerization mode and layer thickness on monomer released from bulk fill composite resins.

Residual monomers released from composite resins have cytotoxic, mutagenic, and estrogenic effects. Mode of polymerization and application thickness are important for monomer release. The aim of this study was to investigate the effects of different modes of a third-generation light-curing unit (LCU) and layer thickness on residual monomer released from two different bulk-fill composite resins. A total of 80 samples were prepared for each bulk-fill composite using a mold. Each bulk-fill composite was divided into four groups according to polymerization mode (standard and extra power) and layer thickness (2 and 4 mm). In addition, four groups were divided into four subgroups according to time periods (1 h, 24 h, 3 days, and 7 days). The samples were polymerized with VALO LED device. The amount of residual monomer was measured with High-Performance Liquid Chromatography (HPLC). All statistical analyses were processed using SPSS Version 23.0. The normal distribution of data was confirmed using Kolmogorov-Smirnov Normal Distribution Test and Shapiro-Wilk Normal Distribution Test. When the distribution was normal, parametric tests, Student's t test and one-way ANOVA, were used. When the distribution was not normal, non-parametric tests, Mann-Whitney U test, and Kruskal-Wallis testwere used. It was found that the standard mode of LCU produced lower amounts of TEGDMA, Bis-GMA, and UDMA in both composite materials. In addition, when the layer thickness increased, TEGDMA, Bis-GMA, and UDMA releases increased, too. This study revealed that the amount of residual monomers released from bulk-fill composites was affected by layer thickness and polymerization time.

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.

Evaluation of Residual Monomers Eluted from Pediatric Dental Restorative Materials.

Unreacted monomers eluted from resin-based restorative materials have been considered a reason of local and systemic adverse reactions. This study was designed to determine the effect of finishing and polishing procedures on the elution of Bis-GMA, TEGDMA, UDMA, and HEMA monomers from compomer and bulk-fill composite resins. Bulk-fill composite (3M ESPE GmbH, Seefeld, Germany) and compomer (Dentsply DeTrey GmbH, Konstanz, Germany) specimens with 3 × 4 mm diameters were prepared. The specimens were randomly divided into two groups, and finishing-polishing procedures were applied only to the experimental groups. Release of residual monomers was analyzed by using High-Performance Liquid Chromatography (HPLC) after 24, 48, and 72 hours. Repeated measures ANOVA and Tukey post hoc tests were used for comparisons. Finishing and polishing procedures had a significant effect on reducing the quantity of UDMA release in the Filtek™ Bulk Fill composite and Bis-GMA, HEMA, and TEGDMA in the Dyract XP compomer (p < 0.05). The restorative materials investigated here are not chemically stable after polymerization, and concentrations of eluted monomers may reach critical toxicity levels even after one restoration placement. Finishing and polishing procedures are mandatory to reduce residual monomers.

Long Term Monomer Elution of Bulk-Fill and Conventional Resin Composites

The process of elution of unreacted monomers from dental resin composites can adversely affect their biocompatibility and longevity. In this regard, it is of interest to monitor relies on unreacted monomers from SonicFill, especially since this new type of bulk-fill composite materials entered dental practice with their simplified and shortened application protocol. This study aimed to assess long term monomer elution from bulk- fill (SonicFill) and conventional low shrinkage resin composites (FiltekP60 and FiltekUltimate), applied in 2mm layer thickness and stored in different extraction media - 6-month period exposure in artificial saliva, followed by 24 hours exposure in 75% ethanol solution. Analysis of monomer elution was performed using HPLC-MS. Monomers detected in artificial saliva were: UDMA and EDB from the conventional composites. No eluted monomers were detected from SonicFill. In just 24 hours of exposure in 75% alcoholic solution, components were extracted from all the materials that were not extracted for 6 months in the artificial saliva: Bis-GMA, TEGDMA, EDB from SonicFill; Bis-GMA from Filtek P60, and Filtek Ultimate. There was a new peak in the release of UDMA from Filtek P60 and Filtek Ultimate. Data reveal, that the extraction medium is extremely important for the separation of monomers. The degree of polymerization cannot completely influence the release of monomers into the surrounding environment. Internal factors, concerning materials composition, are more important, than the ability to control clinically degree of polymerization by intensity and duration of light exposure.

Characteristics of experimental resin-modified glass-ionomer cements, containing alternate monomers to HEMA

ObjectiveResin-modified glass ionomer cements (RMGICs) present several advantages (e.g. fluoride release), but their reported cytotoxicity has been associated with hydroxyethyl methacrylate (HEMA) monomer release. Therefore, different monomers were tested for use in RMGICs in order to improve their biocompatibility and reduce monomer release. MethodsEight experimental liquid compositions were prepared replacing different percentages of HEMA (conventional monomer used in commercial RMGICs) with hydroxypropyl-methacrylate (HPM) and/or tetrahydrofurfuryl-methacrylate (THFM), which are known to have better biocompatibility. Moreover, two commercial materials (Fuji-Plus and RelyX) and two compositions, based on these (home), were included as controls. Monomer release of all materials (commercial, home and experimental) were tested using high-performance liquid chromatography (HPLC) methods after immersing discs in deionized-water (DW) or ethanol:DW. Cytotoxicity of the materials extracts was tested on normal human oral fibroblast line (NHOF-1) using 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. ResultsThree experimental materials containing THFM (F3, R3 and R4) showed less or similar monomer release compared to corresponding commercial products. Furthermore, two experimental materials (F3 and F4) showed similar effects on NHOF-1 cells compared to the negative control medium. SignificanceThe lower monomer release and higher cell viability of some experimental THFM compositions are encouraging. THFM partially replacing HEMA is potentially a suitable alternative for producing biocompatible RMGICs.

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.

Cytotoxicity and cell response of preosteoblast in calcium sulfate-augmented PMMA bone cement

Poly(methyl methacrylate) (PMMA) has been widely used in orthopedic applications, but bone ingrowth and toxic monomer release are drawback of this material. Particle reinforcement with osteoconductive substitute, such as calcium sulfate (CaSO4), is one of the solutions used to modify PMMA bone cement. The current study investigated the mechanical, chemical and biological properties of CaSO4-augmented bone cement. Mechanical strength was measured by a material testing machine. The concentration of methyl methacrylate (MMA) monomer from the various formulations of PMMA mixed with CaSO4 was measured by ultra-performance liquid chromatography (UPLC). CCK-8 assay and ALP assay were performed to evaluate cytotoxicity of released MMA monomer and cell differentiation. The attachment of cells to CaSO4-augmented bone cement discs was observed by confocal and scanning electron microscopy, and surface topography was also evaluated by atomic force microscopy. The results revealed that increased CaSO4 weight ratios led to compromised mechanical strength and increased MMA monomer release. Cell density and cell differentiation on CaSO4-augmented bone cement discs were decreased at CaSO4 weight ratios above 10%. In addition, the presence of micropores on the surface and surface roughness were both increased for PMMA composite discs containing higher levels of CaSO4. These results demonstrated that fewer MC3T3-E1 cells on the surface of CaSO4–PMMA composites was correlated to increased MMA monomer release, micropore number and surface roughness. In summary, the augmentation of a higher proportion of CaSO4 (>10 wt. %) to PMMA did not promote the biological properties of traditional PMMA bone cement.

Translation of a spinal bone cement product from bench to bedside

Spinal acrylic bone cements (ABCs) are used clinically for percutaneous vertebroplasty (PVP) and kyphoplasty (PKP) to treat osteoporotic vertebral compression fractures. Product translation of spinal ABC products followed the design control processes including design verification and validation. The bench to bedside translation of the first Chinese spinal ABC product (Alliment®, namely Alliment Cement) approved by National Medical Products Administration of China was investigated and another commercial product served as the control (Osteopal®V, namely Osteopal V Cement). Results of non-clinical bench performance verification tests of compression, bending and monomer release showed that the newly marketed Alliment Cement is similar to the Osteopal V Cement with properties of both meeting the criteria specified by standards. The Alliment Cement demonstrated good biocompatibility during the 26 weeks’ bone implantation test. Porcine cadaver validation tests further revealed that the Alliment Cement satisfied the needs for both PVP and PKP procedures. A post-approval, retrospective clinical investigation further demonstrated the safety and efficacy of the Alliment Cement, with a significant reduction of pain and the improved stability of the fractured vertebral bodies. A successful translation of biomaterial medical products needs close collaborations among academia, industry, healthcare professionals and regulatory agencies.

β-amyloid monomers drive up neuronal aerobic glycolysis in response to energy stressors

Research on cerebral glucose metabolism has shown that the aging brain experiences a fall of aerobic glycolysis, and that the age-related loss of aerobic glycolysis may accelerate Alzheimer’s disease pathology. In the healthy brain, aerobic glycolysis, namely the use of glucose outside oxidative phosphorylation, may cover energy demand and increase neuronal resilience to stressors at once. Currently, the drivers of aerobic glycolysis in neurons are unknown. We previously demonstrated that synthetic monomers of β-amyloid protein (Aβ) enhance glucose uptake in neurons, and that endogenous Aβ is required for depolarization-induced glucose uptake in cultured neurons. In this work, we show that cultured cortical neurons increased aerobic glycolysis in response to the inhibition of oxidative phosphorylation by oligomycin or to a kainate pulse. Such an increase was prevented by blocking the endogenous Aβ tone and re-established by the exogenous addition of synthetic Aβ monomers. The activity of mitochondria-bound hexokinase-1 appeared to be necessary for monomers-stimulated aerobic glycolysis during oxidative phosphorylation blockade or kainate excitation. Our data suggest that, through Aβ release, neurons coordinate glucose uptake with aerobic glycolysis in response to metabolic stressors. The implications of this new finding are that the age-related drop in aerobic glycolysis and the susceptibility to Alzheimer’s disease could be linked to factors interfering with release and functions of Aβ monomers.

Cutin extraction and composition determined under differing depolymerisation conditions in cork oak leaves

Cutin is a biopolyester involved in waterproofing aerial plant organs, including leaves. Cutin quantification and compositional profiling require depolymerisation, namely by methanolysis, but specific protocols are not available. Investigate how different methanolysis conditions regarding catalyst concentration effect cutin depolymerisation and monomer release, to better define protocols for cutin content determination and composition profiling. Cork oak (Quercus suber) dewaxed leaves were reacted with five sodium methoxide (NaOMe) concentrations. Extracts were analysed: glycerol by high-performance liquid chromatography (HPLC) and long-chain lipids by gas chromatography-mass spectrometry (GC-MS). Cutin was completely removed by 3% NaOMe (8.4% of dewaxed leaves), while mild 0.1% and 0.01% NaOMe methanolysis only depolymerised 14% of total cutin. Reactivity of cutin ester bonds is not homogeneous and glyceridic ester bonds are more easily cleaved, releasing the existing glycerol already under the mildest conditions (0.53% with 0.01% NaOMe and 0.41% with 3% NaOMe). The composition of cutin extracts varies with depolymerisation extent, with easier release of alkanoic acids and alkanols, respectively, 34.9% and 8.8% of total monomers at 0.1% NaOMe, while ω-hydroxyacids (49.3% of total monomers) and α,ω-diacids (9.0% of the monomers) are solubilised under more intensive reactive conditions. Cutin of Quercus suber leaves is confirmed as a glyceridic polyester of ω-hydroxyacids and alkanoic acids, with minor content of α,ω-diacids, and including coumarate moieties. The protocol for the determination of cutin content and compositional profiling was established regarding catalyst concentration. The molar composition of cutin suggests a macromolecular assembly based on glycerol linked to lipid oligomeric chains with moderate cross-linking.

Nickel, chromium and methyl methacrylate monomer release from orthopaedic functional appliances.

This study was purposed to evaluate release of nickel and chromium ions and methyl methacrylate (MMA) monomers from functional appliances and their possible health effects. Study design: Twin-block appliances and Bionators were immersed in artificial saliva and kept in a thermal incubator. Control group was established as artificial saliva without appliances. Artificial saliva was analysed after 7 days, 30 days and 90 days. Inductively coupled plasma mass spectrometry and gas chromatography-mass spectrometry was used for detection of nickel and chromium ions and MMA monomers. MTT assays and cytokine array were performed. One way ANOVA with Tukey test and Dunnett's T3 for post-hoc analysis was used for evaluation of time-dependent changes and independent t-test was used for evaluation of MTT assay results. The results revealed that metal ions and MMA monomers are released from the appliances. Metal ion detection pattern was irregular and could not be analysed. Twin-block group showed significantly larger amount of MMA release. MTT assay revealed statistically significant but minimally reduced cellular activity on Bionator and twin-block groups compared to control groups. Cytokine array showed no or less inflammatory cytokine release on Bionator and twin-block groups. MMA monomer release was confirmed but the cytotoxic effect of functional appliance material release is minimal or negligible. General toxicity of the functional appliance from the MMA monomer release is likely to be minimal or negligible.

Thermal Stability and Monomer Elution of Bulk Fill Composite Resins Cured from Different Irradiation Distances.

Objectives : This study aimed to evaluate the thermal stability and monomer elution of bulk fill composite resins cured at different irradiation distances. Materials and Methods: Forty cylindrical-shaped (3×4mm) specimens were fabricated from two composite resins (X-tra fil, X-tra base) and cured from 0 and 7mm distances. In 9 specimens, the degree of conversion was determined by the release of monomers. For this purpose, after curing of composites, they were immersed in 5 mL of 99.9% methanol and stored at 37°C for 24h. The eluted monomer was then analyzed by gas chromatography (GC). Also, thermal stability of one sample from each group was assessed by thermogravimetric analysis (TGA) at a rate of 10°C/min. Data were analyzed using two-way ANOVA and Tukey’s post-hoc test (P<0.05). Results: X-tra fil had significantly higher degree of conversion than X-tra base (P=0.001). Specimens cured at 7mm distance had significantly lower degree of conversion compared with those cured at 0 mm distance (P=0.001). The interaction effect of composite type and distance of light curing unit from the surface of samples was statistically significant (P=0.001). Regarding the TGA results, the lowest and the highest percentages of weight loss were detected in X-tra fil cured at 0 mm distance and X-tra base cured at 7mm distance, respectively. Conclusion: X-tra fil composite cured at 0mm distance had the highest degree of conversion and thermal stability, and X-tra base composite cured at 7mm distance had the lowest values.

Determination of the residual monomer concentration of ε‐caprolactam in polyamide‐6 using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy gas analysis

AbstractFor the anionic polymerization of ε‐caprolactam to polyamide‐6 the residual monomer concentration in the final polymer is an important characteristic. To determine this residual ε‐caprolactam monomer concentration, a fast and fail‐safe method was developed, which couples thermogravimetric analysis (TGA) with Fourier transform infrared spectroscopy (FTIR) gas analysis. FTIR allows an identification of the types of gasses released during heat treatment. Calibration of the infrared absorbance of ε‐caprolactam and the corresponding mass loss in TGA allows a quantitative evaluation of the ε‐caprolactam monomer release. Low‐heating rates and powdery samples guarantee high‐precision measurements.

Effect of layer thickness on residual monomer release in polymerization of bulk-fill composites

The aim of the present study was to investigate and compare the quantity of residual monomers leached from the bulk-fill composites with different compositions polymerized at varying layer thickness. Three bulk-fill (X-tra-fil, Beautifil Bulk Restorative, Fill-Up) and a nanohybrid composite (Filtek Z550) were used for the study. The composite resin samples were prepared with a stainless steel mold. For each composite, two groups were constructed. The samples in the first group were prepared using the 2 + 2 mm layering technique. In the second group, the composite samples were applied as a 4 mm-thick one layer and polymerized. Then, each composite samples were kept in a 75% ethanol solution and residual monomers released from composite resins were analyzed with an HPLC device after 24hour and 1 month. The data were analyzed using Kruskal-Wallis and Mann-Whitney U tests. Except the Fill-Up, all of residual monomer elution from the bulk-fill composites was significantly affected by the layer thickness (p &lt; 0.05). The greatest monomer release was detected at 1 month after polymerization as a single 4 mm layer for Beautifil Bulk Restorative. Fill-Up composite showed similar residual monomer release in polymerization at different layer thicknesses compared to other composite resins. In the 2 + 2 mm layering technique, the least monomer elution was detected in the Filtek Z550 composite group. While Bis-GMA was the most released monomer in X-tra fil composite, UDMA was the most released monomer in all other composite resins. During polymerization of the bulk-fill composite, the layer thickness of the composite applied may affect the amount of residual monomers released from the composite resins. Conventional composites may release less monomer than bulk-fill composites when used with layering.

Influence of pH and calcium concentration on milk protein fractionation by 0.1 μm microfiltration at low temperatures

During the microfiltration of skim milk at low temperatures, such as 10–20 °C, the casein micelle partially disintegrates, mainly releasing β-casein into the serum phase, which can pass the membrane along with the whey proteins. This results in undesirable casein losses on the retentate side and in a reduced purity of the whey protein fraction. The goal of this study was to assess means to reduce the permeation of casein monomers during milk protein fractionation by microfiltration at temperatures between 10 and 20 °C. Therefore, calcium concentration and pH variation were applied in order to counter the effect of release of casein monomers. It could be shown that the permeation of serum casein monomers can thus be substantially reduced, without negative effects on flux, as long as the added calcium level does not exceed 5 mm. Whey protein concentration in the permeate remained unaffected up to 1 mm added calcium.

Evaluation of Residual Monomer Release After Polymerization of Colored Compomer Materials

Objective: To evaluate the amount of residual monomers released after polymerization by the compomers in different colors and viscosities over time. Material and Methods: The compomer samples of different colors and viscosities (flowable compomers; blue-pink and packable compomers; A2-blue-pink-gold) were prepared in molds with an inner diameter of 5 mm and a height of 2 mm. In polymerization of samples, a LED unit was used. The amount of monomers released from the samples kept in 75% ethanol/water solution was measured by a high-performance liquid chromatography (HPLC) instrument in the 10th minute, in the 1st hour, and in the 1st, 7th, and 14th days. For statistical analyses, the paired sample t-test, independent sample t-test, and one-way ANOVA with Tukey's post hoc test were used. Results: The amount of residual monomers released from all materials increased over time. At the end of the 14th day, the most released monomer from all compomer samples was BisGMA. The total amounts of released monomers from the packable compomers were Gold>A2>blue>pink. The amount of residual monomers released from flowable compomers was higher in blue than in pink. Conclusion: The color and the viscosity are the factors affecting the residual monomer release in compomers.

Effect of Degree of Conversion of Different Resin Composite Monomers (Methacrylate and Silorane) on Two Caries-Associated Bacteria

Abstract Background and Objectives: The biological response of oral bacteria to dental restorative polymer composites is mediated by the release of unpolymerized residual monomers. The aims of the present study were first, evaluating the effect of composite elutes from methacrylate composite resins and silorane-based composites on two cariogenic bacterial pathogens: Streptococcus mutans and Lactobacillus acidophilus and second, determination of degree of conversion (DC) of standardized discs made from the low-shrinkage silorane-based composite (FiltekTM P90) resin and methacrylate-based composite resin (FiltekTM Z350XT nanocomposite, FiltekTM Z350 Flow) using Fourier transform infrared spectroscopy (FTIR). Materials and Methods: Thirty-six composite specimens were prepared for the agar diffusion test and dissolved in a solvent (dimethyl sulfoxide) to attain a suspension, which was used to assess the effect of the residual monomers from methacrylate composite resins and silorane-based composites on the growth of S. mutans and L. acidophilus. To avoid more dilutions of the specimens, the colonies of bacteria were counted by the naked eye. Thirty composite specimens of 2 mm × 6 mm were polymerized for DC test, and the DC was measured using FTIR, also for unpolymerized composite resin. Results: The growth of S. mutans bacteria was inhibited when cultured with Filtek Z350 Flow composite resin, while the growth of L. acidophilus bacteria was stimulated by the Filtek Silorane p90 and Filtek Z350 Flow composite resin. The DC test with the Filtek Silorane composite resin showed highest DC (58%), then the Filtek Z350XT (Nanocomposite) (42%) followed by the Filtek Z350 Flow (Flowable) showed lowest (35%). Conclusions: Our results demonstrate that composite filling materials have a versatile nature of effect on oral pathogenic bacteria, which could modulate their pathogenesis. Dentists may thus select the appropriate type of composite filling according to the caries susceptibility of patients.

Monomer conversion, release and cytotoxicity analyses of experimental GDMA-P based adhesives

This study aimed to evaluate the effects of a photoinitiator system and acidic monomer (GDMA-P) concentrations on self-etch experimental dental adhesive degree of conversion (DC), monomer release and cytotoxicity. Three monomer blends containing different GDMA-P/HEMA/UDMA ratios were produced: 1/3/3; 2/3/2; and 3/3/1. CQ + EDMAB; BAPO or CQ + BAPO + EDMAB were used as photoinitiator systems. DFI was added as co-initiator, and a water/ethanol mixture was used as solvent. DC was evaluated by Fourier transform infrared spectroscopy (FTIR) (n = 10). Monomer release was identified by ultra-high performance liquid chromatography (UHPLC) (n = 6). The Alamar Blue assay was used to test NIH-3T3 fibroblast cell viability (n = 8). A two-way ANOVA and Tukey post-hoc test were used for the data analyses (p < 0.05). Experimental adhesives presenting higher GDMA-P concentrations displayed an overall statistically lower DC, less monomer release and increased cell viability (p < 0.05). BAPO resulted in increased DC and lower monomer release rates than CQ only (p < 0.05). Low GDMA-P concentrations associated to BAPO generated an adhesive system with improved conversion and both lower monomer release rates and cytotoxicity.