The mechanical, wear, antibacterial properties and biocompatibility of injectable restorative materials under wet challenge.

OBJECTIVES: To evaluate the mechanical, wear, antibacterial properties, and biocompatibility of injectable composite materials. METHODS: Two injectable composite resins (GU and BI), one flowable composite resin (FS), and one flowable compomer (DF), in A2 shade, were tested. Mechanical properties were tested via three-point bending test immediately after preparation and after 1-day, 7-day, 14-day, and 30-day water storage. Under water-PMMA slurry immersion, specimens were subjected to a 3-body wear test (10,000 cycles) against stainless steel balls, while the roughness, wear depth, and volume loss were recorded. After 1-day and 3-day MC3T3-E1 cell culture, cell viability was evaluated with CCK-8 test kits, while the cell morphology was observed under CLSM and SEM. Antibacterial properties on S. mutans were assessed via CFU counting, CLSM, and SEM observation. SPSS 26.0 was used for statistical analysis (α = 0.05). RESULTS: The mechanical properties were material-dependent and sensitive to water storage. Flexural strength ranked GU > FS > BI > DF at all testing levels. Three nanocomposites had better wear properties than DF. No significant difference on 1-day cell viability was found, but DF showed significantly lower cell proliferation than nanocomposites on 3-day assessment. GU and FS had more favourable cell adhesion and morphology. CFU counting revealed no significant difference, while FS presented a slightly thicker biofilm and BI showed relatively lower bacteria density. CONCLUSIONS: Injectable nanocomposites outperformed the compomer regarding mechanical properties, wear resistance, and biocompatibility. The tested materials presented comparable antibacterial behaviours. Flowable resin-based composites' performances are affected by multiple factors, and their compositions can be attributed. CLINICAL SIGNIFICANCE: A profound understanding of the mechanical, wear, and biological properties of the restorative material is imperative for the clinical success of dental restorations. The current study demonstrated superior properties of highly filled injectable composite resins, which imply their wider indications and better long-term clinical performances.

Three-dimensional finite element analysis of the composite and compomer onlays in primary molars.

Resin onlay restoration is an esthetic alternative technique used for restoring extensively damaged primary molars. Understanding the behavior of materials under repeated functional stress and how the stress is transmitted to the remaining tooth structure is important. The aim of this study was to compare stresses in primary molars restored with indirect composite and compomer onlay. 3D frame models of the right mandibular and maxillary primary molars and the alveolar bone were created using computerized tomography images of a six-year-old girl. The enamel and dentine layers above the cement layer were unified to generate onlay restoration, and composite and compomer were used as restorative materials. The vertical occlusal load (100 N) was applied to the teeth in the occlusal contact areas. The von Mises stress distributions and normal stress distributions of the y-axis (parallel to the long axis of tooth) were evaluated. The occlusal stress is transmitted to the cervical part of healthy teeth by spreading it through the enamel layer. The composite and compomer restorative materials exhibited similar stress distribution patterns. An indirect technique creates a structure similar to the original morphological form, and it allows restorations to distribute high occlusal stresses and to minimize possible breakages.

Evaluation of Four Different Restorative Materials for Restoration of the Periodontal Condition of Wedge-Shaped Defect: A Comparative Study.

BACKGROUND This study aimed to conduct a clinical evaluation of four restorative materials for restoration of dental wedge-shaped defect (WSD) and their impacts on periodontal tissues. MATERIAL AND METHODS A total of 280 maxillary premolars with dental WSD were selected from 106 patients; the patient cases were divided into eight groups according to different combinations of restorative materials (flowable resin composites, Dyract compomers, glass ionomer cement (GIC), light-curing composite resin), and WSD positions (approaching gingival and subgingival positions). Gingival crevicular fluid (GCF) volume, levels of aspartate aminotransferase (AST), alkaline phosphatase (ALP), and interleukin-1ß (IL-1ß) in GCF were analyzed, while probing depth (PD), plaque index (PLI), and sulcus bleeding index (SBI) were also measured. The periodontal conditions of all patients were followed prior to restoration, as well as six months and 12 months after restoration. RESULTS After six months of restoration, the overall clinical success rates of flowable resin composites, Dyract compomers, and light-curing composite resin were greater than those of GIC. GCF volume, GCF-AST, IL-1ß levels, PD, PLI, and SBI of cases restored by GIC were higher than those restored by the other three materials. After 12 months of restoration, the overall clinical success rates of flowable resin composites and Dyract compomers were greater than those of light-curing composite resin and GIC. GCF volume, GCF-AST, GCF-ALP, IL-1ß levels, PD, PLI, and SBI of cases restored by GIC were higher than those restored by the other three materials. CONCLUSIONS Our study provided evidence that the clinical efficacy of flowable resin composites, Dyract compomers, and light-curing composite resin was greater than that of GIC for restoration of dental WSD.

Evaluation of candida albicans biofilm formation on various dental restorative material surfaces.

AIMS: Candida adhesion to any oral substrata is the first and essential stage in forming a pathogenic fungal biofilm. In general, yeast cells have remarkable potential to adhere to host surfaces, such as teeth or mucosa, and to artificial, nonbiological surfaces, such as restorative dental materials. This study compared the susceptibility of six dental restorative materials to Candida albicans adhesion. MATERIALS AND METHODS: Cylindrical samples of each material were made according to the manufacturersa instructions. The antifungal effect of the samples on C. albicans was determined with the disc-diffusion method. The samples were put in plates with sterile Mueller Hinton and Sabouraud dextrose agar previously seeded with C. albicans. After the incubation period, the inhibition zone around each sample was evaluated. To evaluate the biofilm formation, the XTT technique and scanning electron microscopy (SEM) were used. RESULTS: No inhibition zone was observed around the samples. According to the XTT assays, the amalgam samples revealed the lowest quantity of biofilm formation (P > 0.001). The highest median XTT values, significantly higher than the other materials (P < 0.001), were found for the composite and the compomer samples. Within the SEM examination, the amount of candidal growth was significantly lower on the resin-modified glass ionomer and glass-ionomer cement samples. The compomer and the composite samples showed more candidal adhesion. CONCLUSION: This finding emphasizes the use of glass ionomer restorative cements and amalgam to reduce C. albicans adhesion to dental restorative materials especially in people with weakened immune systems, neutropenia, and cancer.

Do bonding agents protect the bracket-periphery?--Evaluation by consecutive µCT scans and fluorescence measurements.

OBJECTIVES: The aim of this in vitro study was to consecutively determine the effect of three bonding agents on the prevention of enamel demineralisation at the bracket-periphery and to compare the suitability of micro-computed tomography (µCT) scans and quantitative light-induced fluorescence (QLF) to detect changes within subsurface lesions. MATERIALS AND METHODS: The effect of a resin-modified glass ionomer cement (RMGI) (Fuji Ortho LC), a compomer (Assure) and a composite (Transbond XT) on the prevention of enamel demineralisation at the bracket-periphery was examined. After 7, 14, 21 and 28 days of pH cycling, the teeth (N = 45) were examined by consecutive µCT scans and by using a customised QLF set-up. RESULTS: Particularly for the RMGI and for the compomer, the QLF and µCT scans showed that the formation and the body of the lesion were not precisely located at the enamel next to the bracket margin. There was an area that was almost protected. The progression of demineralisation was decreased for the RMGI and the compomer-treated teeth. CONCLUSION: For bonding orthodontic brackets, the RMGI and compomer were comparably able to decrease the progression of white spot lesions (WSL), although the RMGI showed marginally superior protection. Both methods (QLF and µCT scans) were suitable for investigating the longitudinal fluoride effects on WSL, though these effects were more accurately described by mineral (fluorescence) loss or volume changes than by lesion depth. CLINICAL RELEVANCE: The progression of WSL at the bracket-periphery could be altered by using fluoride-releasing bonding agents for bracket application. This approach represents a minimally invasive preventive measure.

Antibacterial surface properties of various fluoride-releasing restorative materials in vitro.

PURPOSE: The aim of this study was to investigate the antibacterial surface properties of high-viscosity glass ionomers (Fuji IX GP, Ketac Molar), a resin-modified nano-ionomer (Ketac N100), resin-modified glass ionomers (Fuji II LC, Vitremer), a compomer (Compoglass F) and a resin-based composite (Filtek Z250). METHODS: ISO-standardized specimens 6 mm in diameter were prepared for each restorative material. The antibacterial properties of the materials were tested in an agar diffusion assay using Streptococcus mutans (ATCC 25175) for 24 and 48 hours. An inhibition zone greater than 6 mm was defined as diffuse inhibition, whereas zones ≤6 mm were described as contact inhibition. RESULTS: All tested materials exhibited a contact antibacterial effect against S. mutans. Vitremer showed the most remarkable antibacterial diffuse inhibition. CONCLUSIONS: These materials might cause antibacterial effects against S. mutans when placed on cavity surfaces in both enamel and dentine, thereby preventing secondary caries formation.

Poly-(L-lactic acid) and citric acid-crosslinked gelatin composite matrices as a drug-eluting stent coating material with endothelialization, antithrombogenic, and drug release properties.

Biodegradable composite matrices comprising poly-(L-lactic acid) (PLLA) and citric acid-crosslinked alkali-treated gelatin (AlGelatin) with endothelialization, antithrombogenic, and drug release properties were prepared. The characterization of composite matrices with various mixing ratios was performed by evaluating their swelling ratio, endothelial cell culture, antithrombogenic tests, and drug release behavior. Tamibarotene (Am80), which specifically inhibits smooth muscle cell proliferation, was employed as the drug. The swelling ratio of composite matrices decreased as the PLLA content decreased. The number of endothelial cells cultured on the surfaces of composite matrices was maximal at the PLLA/AlGelatin-TSC ratio of 80/20. Antithrombogenic tests revealed that the levels of platelets and fibrin network formation decreased as the AlGelatin-TSC content increased. The Am80 release test indicated that the release rate decreased as PLLA content increased. Using the resulting composite matrix, Am80-eluting stents possessing a smooth surface and a coating thickness of ∼15 µm were successfully obtained. Am80 was continuously released from the resulting stent at ∼40%, up to 28 days without burst release. Therefore, Am80-eluting stent with its antithrombogenic and endothelialization properties has great potential for clinical use.

Histological evaluation of rat tissue response to GMTA, Retroplast, and Geristore retrograde filling materials.

The aim of the study was to compare the short-term biocompatibility of grey mineral trioxide aggregate (GMTA), Retroplast and Geristore. Silicon tubes filled with the materials and empty control tubes were implanted in the dorsal connective tissue of 30 Wistar albino rats. The tubes and surrounding tissues were excised and prepared for histological examination at 1 week, 1 month and 2 months after implantation. Inflammatory cell counts and the presence or absence of necrosis adjacent to the materials and control tubes were recorded. Data were statistically analysed using one-way anova and Tukey's multiple comparisons tests. The empty control tubes were well tolerated. All tested materials showed a more severe initial reaction than the control group. With time, the reaction became chronic, with variable increase in the numbers of inflammatory cells. Retroplast recorded the most statistically significant increase in the sum of inflammatory cells. Although the increase in the sum of inflammatory cells was statistically significant for Geristore but not for GMTA, the inflammatory cell counts for both were comparable. It was concluded that the three materials continued to irritate tissues throughout the evaluation period. Retroplast was the least biocompatible of the three tested materials at 2 months, followed by Geristore then GMTA.

Pre-warming of dental composites.

OBJECTIVES: Cavity lining with flowable composites have been proposed to improve initial marginal adaptation and minimize shrinkage stresses. The purpose of this study was to evaluate if prewarming of composites would influence the flow and enhance marginal adaptation thus the effect of pre-warming different types of composites on their properties are reported. METHODS: Six different composites were used in this study including a flowable and a polyacid modified composite. Uncured composites were pressed between two glass plates with a known load and the film thickness was measured to determine flow. Polymerization shrinkage was measured by means of a one-dimension contacting transducer. Flexural strength was determined using a three-point bend test. Microleakage was determined in human lower third molars on both enamel and dentin restoration interfaces. Cytocompatibility was analyzed with an Alamar Blue redox cell proliferation assay. The flow properties, linear shrinkage, flexural strength, microleakage and cytocompatibility were evaluated at 22 °C and 60 °C. RESULTS: The results indicated that the film thickness for each of the materials was significantly lower at 60 °C and the linear shrinkage was greater as a result of the higher degree of polymerization. The flexural strength of Spectrum TPH and Wave were found to be statistically significantly higher with pre-warming, however the other composites did not exhibit any differences. Microleakage studies showed that pre-warming had no significant bearing on the results and alamarBlue(®) results showed that the pre-heating did not have an effect on the cytotoxicity however the levels of cytotoxicity varied between the composites that can be attributed to the composition. SIGNIFICANCE: Pre-warming of the composites studied enhanced flow as observed by measuring film thickness and did not significantly affect other properties.

[Clinical and microbiological study regarding surface antibacterial properties of bioactive dental materials]. / Studiu clinico-microbiologic privind proprietatile antibacteriene ale unor materiale de restaurare cu caracter bioactiv.

UNLABELLED: In the new era of dentistry the coronal restoration materials must possess "bio-active" features represented by fluor ions release, chemical adhesion and antibacterial agents. AIM: Our study aims to determine the surface antibacterial properties of glassionomer cements and compomers. MATERIALS AND METHOD: The study group included 64 patients with high cariogenic risk with 80 teeth with acute and chronic dental caries affecting proximal and occlusal dental surfaces. The teeth with cariogenic lesions were restored with zinc-oxide-eugenol (n=20), glassionomer cement GC Fuji Triage (n=20), glassionomer cement modified with resins Fuji II LC (n=20), compomer Dyract (n=20). DENTOCULT SM test (Orion Diagnostica, Finland) was used for bacterial analyses. The samples from bacterial biofilm were collected from the restorated dental surfaces (study group) and intact enamel surfaces (control group). The recorded data were processed using non-parametrical statistical tests. RESULTS: The lowest mean value of bacterial indices was recorded for glassionomer cement Fuji Triage (0.4), and Fuji II LC (1.2), material with highest surface antibacterial properties. The highest value (1.5) was recorded for compomer Dyract. The Kruskal-Wallis test proves the significant statistical differences between the three bioactive materials. CONCLUSION: The materials with bioactive features have the ability to inhibate the growth of Streptococcus mutans in bacterial biofilm to the surfaces of coronal restoration.

Antibacterial properties of pit and fissure sealants combined with daily fluoride mouth rinse.

PURPOSE: Pit and fissure sealants are widely used in the prevention of initial occlusal caries. The purpose of this study was to determine whether fluoride releasing pit and fissure sealants regain their antibacterial properties after rinsing with a fluoride solution. METHOD: Helioseal F, Ultraseal XT, Dyract Seal, and GC Fuji TRIAGE were placed on the sidewalls of the wells of a 96-microtiter plate. After polymerization and a 30 day aging process, the samples were rinsed daily with a 0.05% NaF solution for 14 days. Twenty four hours after the last fluoride rinse, freshly grown Streptococcus mutans cells (circa 1 x 106) were placed on the surface of each sample for 1 hour at 37 degrees C. Growth medium was then added to each well and bacterial growth was followed for 24 hours in a temperature-controlled spectrophotometer. Similar experiments were conducted on samples 48 hours and 72 hours after the last fluoride rinse. RESULTS: The results showed that both GC Fuji TRIAGE and Dyract Seal possessed antibacterial properties 24 hours after the last fluoride exposure. GC Fuji TRIAGE maintained potent antibacterial properties 48 hours after the last fluoride rinse. 72 hours after the last fluoride rinse none of the materials showed any antibacterial properties. CONCLUSIONS: None of the tested materials showed any antibacterial properties after a 30 day aging process An aging process of all tested sealant materials, for 30 days, resulted in a complete elimination of their antibacterial properties. After a daily 30 second rinse for two weeks with a 0.05% NaF solution, the antibacterial attributes of the glass-ionomer and the compomer based sealants were regained.

Influence of different resin-based restorative materials on mutans streptococci adhesion. An in vitro study.

PURPOSE: To investigate the surface roughness and the initial adhesion of Streptococcus mutans on seven dental resin-based restorative materials. METHODS: Five cylinder specimens, with 5 mm diameter and 3 mm height, of three resin composites (Z100, Prodigy and Tetric), three polyacid modified composite resins (Compoglass, Compoglass F and Dyract AP) and a resin modified glass ionomer (Vitremer) were made. Materials were handled following manufacturer's instructions. The materials were polished up to 1200 grit SiC abrasive paper under running water in an automatic polisher. Surface roughness measurements were carried out by a profilometer. Five diametrical measurements were made and Ra was calculated in microm. The bacterial initial cell adhesion assay was performed with S. mutans ATCC 25175. The initial adhesion of Streptococcus mutans on the materials tested was observed by SEM. ANOVA and Student-Newman-Keuls multiple comparisons were used. RESULTS: The statistical analyses showed no significant differences in initial cell adhesion among tested materials, even when the resin-modified glass inonomer showed a rougher surface than the rest of the materials.

In vitro antibacterial evaluation of flowable restorative materials.

OBJECTIVES: The microgap at the tooth-restoration interface is inevitable and may allow bacterial penetration that could lead to failure. The purpose of this in vitro study was to assess the antibacterial potential of 4 flowable composite restorative materials. METHOD AND MATERIALS: The antibacterial potential of Aeliteflo (Bisco), Filtek Flow (3M ESPE), Tetric Flow (Ivoclar Vivadent), and Dyract Flow (Dentsply) was tested against Streptococcus mutans. Agar diffusion test (ADT) and direct contact test (DCT) were the methods used. For ADT, wells were punched in S mutans-inoculated plates. The materials were placed in the wells and polymerized. Inhibition zones were measured after 48 hours' incubation at 37 degrees C. In the DCT, 8 samples of each tested material were placed on the side walls of wells in a 96-microtiter plate and polymerized. A suspension of S mutans was placed on the surface of each sample. Bacterial growth was monitored by optical density changes at 650 nm every 30 minutes for 16 hours. The experiment was repeated after the samples were aged in phosphate-buffered saline for 1 and 7 days. RESULTS: In both tests, only Dyract Flow showed inhibition of S mutans growth. Except for Dyract Flow samples, aged samples did not statistically differ in S mutans inhibition when compared to their 1-hour control counterparts. Dyract Flow samples lost their S mutans inhibitory potential after 24 hours. CONCLUSION: The flowable composites tested do not possess effective long-term antibacterial ability.

Effects of Dyract AP and released ionic products on periodontal ligament cells and bone marrow cultures.

OBJECTIVES: The aim of this work was to investigate the release of inorganic ionic products from specimens of the polyacid-modified composite resin Dyract AP (DAP) and furthermore, to analyze the biological effect of DAP and the medium extract in human periodontal ligament (PDL) cells and mouse bone marrow cell (BMC) cultures. METHODS: Ion release from DAP specimens immersed in cell culture medium was analyzed with inductively coupled plasma optical emission spectroscopy (ICP-OES). Cells were cultured with either DAP specimens or with DAP media extract and effects on cell proliferation, osteoblastic gene expression and mineralization capacity were analyzed with direct-contact tests, neutral red (NR) uptake, quantitative real-time PCR and a bone nodule formation assay. RESULTS: ICP-OES analysis of DAP extract demonstrated a significant increase in fluoride, strontium and silica. PDL cells demonstrated normal growth pattern in the direct-contact tests with the material. DAP extracts produced a dose-dependent stimulation of cell proliferation and concomitant inhibition of osteoblast specific markers and nodule formation. SIGNIFICANCE: The compomer may have possible bioactive properties due to ions leaching out from the filler component.

Comparison of nanoscale and microscale bioactive glass on the properties of P(3HB)/Bioglass composites.

This study compares the effects of introducing micro (m-BG) and nanoscale (n-BG) bioactive glass particles on the various properties (thermal, mechanical and microstructural) of poly(3hydroxybutyrate) (P(3HB))/bioactive glass composite systems. P(3HB)/bioactive glass composite films with three different concentrations of m-BG and n-BG (10, 20 and 30 wt%, respectively) were prepared by a solvent casting technique. The addition of n-BG particles had a significant stiffening effect on the composites, modulus when compared with m-BG. However, there were no significant differences in the thermal properties of the composites due to the addition of n-BG and m-BG particles. The systematic addition of n-BG particles induced a nanostructured topography on the surface of the composites, which was not visible by SEM in m-BG composites. This surface effect induced by n-BG particles considerably improved the total protein adsorption on the n-BG composites compared to the unfilled polymer and the m-BG composites. A short term in vitro degradation (30 days) study in simulated body fluid (SBF) showed a high level of bioactivity as well as higher water absorption for the P(3HB)/n-BG composites. Furthermore, a cell proliferation study using MG-63 cells demonstrated the good biocompatibility of both types of P(3HB)/bioactive glass composite systems. The results of this investigation confirm that the addition of nanosized bioactive glass particles had a more significant effect on the mechanical and structural properties of a composite system in comparison with microparticles, as well as enhancing protein adsorption, two desirable effects for the application of the composites in tissue engineering.

Surface antibacterial properties of resin and resin-modified dental cements.

OBJECTIVE: Cements possessing antibacterial properties may reduce bacteria-induced fixed partial denture complications. The purpose of this study was to evaluate the antibacterial properties of 4 dental cements using the direct contact test (DCT) and the agar diffusion test (ADT). METHOD AND MATERIALS: The ADT was performed using mitis salivarius agar plates. Each plate was evenly inoculated with freshly grown mutans streptococci. Two samples of each test material-RelyX ARC, Variolink II, GC FujiCEM, and Principle-were placed, and the inhibition halo obtained was measured after 48 hours. For the DCT, 8 samples were placed on the sidewalls of wells in a 96-well microtiter plate. After polymerization, freshly grown Streptococcus mutans cells (1 X 10(6)) were placed on the surface of each sample for 1 hour at 37 degrees C. Fresh medium was then added to each well, and bacterial growth was followed for 16 hours in a temperature-controlled spectrophotometer. Similarly prepared samples were aged in phosphate-buffered saline for 1 or 7 days and the DCT was repeated. Analysis of variance (ANOVA) and Tukey multiple comparisons were applied to the data. RESULTS: In the ADT, GC FujiCEM showed an inhibition zone of 2.0 +/- 0.3 mm, and Principle showed an inhibition zone of 1.2 +/- 0.2 mm. In the DCT, freshly polymerized samples of GC FujiCEM and Principle exhibited potent antibacterial properties, while samples of Variolink II and RelyX ARC showed moderate antibacterial properties. Principle showed some antibacterial properties even after 1 day (P < .001). CONCLUSION: None of the tested cements in this study possesses long-term antibacterial properties.

Surface antibacterial properties of compomers.

AIM: This was to evaluate the antibacterial properties of four different compomers, using direct contact test (DCT) and agar diffusion test (ADT). Compomers (Polyacid Modified Composite Resin) form a group of dental restorative materials which were developed in order to improve conventional glass-ionomer and are widely used by pediatric dentists in primary dentition. Microorganisms captured under restorations or penetrating through the micro-gap at the tooth-restoration interface are the cause of secondary caries and pulpal pathology. METHODS: For the DCT, 8 samples of Freedom (SDI), F2000 (3M-ESPE), Dyract (Dentsply) and Hytac Hplitip (3M-ESPE) were placed on the sidewalls of wells in 96 microtiter plate. After polymerization, freshly grown streptococcus mutans cells (1x10(6)) were placed on the surface of each sample for one hour at 37 degrees C, fresh media was then added to each well and bacterial growth was followed for 16 hours by temperature controlled spectrophotometer. Similarly prepared samples were aged in phosphate buffered saline for 1, or 7 days and the DCT was repeated. The ADT was performed by placing samples in uniform wells punched in agar plates. RESULTS: In the DCT, freshly polymerized samples of F2000 showed the most potent antibacterial properties, while those of Hytac Hplitip showed moderate antibacterial phenomena. Dyract and Freedom did not show any antibacterial activity relative to the control material. None of the four aged materials showed antibacterial activity in the DCT after 1 or 7 days. In the ADT the halo in the bacterial lawn was measured after 48 hours and only F2000 demonstrated an inhibition zone of 2.15+/-0.3 mm. Statistics. Two way ANOVA indicated a significant difference in the growth rate of bacteria placed both on the different compomers (P<0.001) and in different tested time points (P<0.001). CONCLUSION: None of the compomers tested provided significant long term antibacterial activity.

Modeling and experimental investigation of rheological properties of injectable poly(lactide ethylene oxide fumarate)/hydroxyapatite nanocomposites.

Injectable multiphasic polymer/ceramic composites are attractive as bioresorbable scaffolds for bone regeneration because they can be cross-linked in situ and are osteoconductive. The injectability of the composite depends on the nanoparticle content and the energetic interactions at the polymer/particle interface. The objective of this research was to determine experimentally the rheological properties of the PLEOF/apatite composite as an injectable biomaterial and to compare the viscoelastic response with the predictions of a linear elastic dumbbell model. A degradable in situ cross-linkable terpolymer based on low molecular weight poly(L-lactide) and poly(ethylene oxide) linked by unsaturated fumarate groups is synthesized. The poly(L-lactide-co-ethylene oxide-co-fumarate) (PLEOF) terpolymer interacts with the surface of the apatite nanoparticles by polar interactions and hydrogen bonding. A kinetic model is developed that takes into account the adsorption/desorption of polymer chains to/from the nanoparticle surface. Rheological properties of the aqueous dispersion of PLEOF terpolymer reinforced with nanosized hydroxyapatite (HA) particles are investigated using mechanical rheometry. To this end, we performed a series of rheological experiments on un-cross-linked PLEOF reinforced with different volume fractions of HA nanoparticles. The results demonstrate that the observed nonlinear viscoelasticity at higher shear rates is controlled by the energetic interactions between the polymer chains and dispersed particle aggregates and by the rate of the adsorption/desorption of the chains to/from the surface of the nanoparticles.

Antibacterial effect of selected root-end filling materials.

The purpose of this study was to evaluate the antibacterial activity of leachable components of selected root-end filling materials: amalgam, ProRoot MTA (mineral trioxide aggregate), Intermediate Restorative Material (IRM), Super Bond C&B, Geristore, Dyract, Clearfil APX composite with SE Bond, or Protect Bond. The direct contact test (DCT) with Staphylococcus aureus, Enterococcus faecalis, and Pseudomonas aeruginosa, was used. The materials were tested immediately after application to the microtiter wells (fresh samples) and after setting for 3 days (set samples). Ten microliters of bacterial suspension was added to each well for direct contact with each material for 1 h at 37 degrees C. Growth of surviving bacteria was then measured in a microplate spectrophotometer hourly at 620 nm for 15 h. Twelve uncoated wells using identical inoculum size served as positive controls. The data obtained at the end of 15 h was subjected to one-way ANOVA and post hoc comparisons were done using Tamhane's T2 test. Fresh samples of all materials showed a 3-h delay in exponential growth of both E. faecalis and S. aureus, and a 5-h delay in growth of P. aeruginosa. Set samples of IRM and ProRoot MTA cements showed generally greater antibacterial activity than the other materials: both completely inhibited P. aeruginosa, and both delayed or limited growth of E. faecalis. The DCT, by being quantitative and virtually independent of solubility and diffusion, was found suitable to assay solid root-end filling materials. IRM and ProRoot MTA were generally more potent inhibitors of bacterial-growth than the other tested materials.

Influence of different adhesive restorative materials on mutans streptococci colonization.

PURPOSE: To evaluate the effect of some restorative materials on mutans streptococci colonization. METHODS: Awild strain of mutans streptococci was isolated from human dental plaque and a monospecific biofilm adherent to the surfaces of 12 adhesive restorative materials (F2000, Dyract AP, Compoglass F, Z100 MP, Filtek Z250, Clearfil, Ketac-Bond, Ketac-Fil Plus, Ketac-Molar, Fuji Cap II, Fuji Bond LC and Fuji II LC) were tested. A colorimetric technique (MTT assay), based on the reduction of a yellow tetrazolium salt to a purple formazan, was used to evaluate the biomass adherent to the disk surfaces after a 24-hour growth. RESULTS: One-way ANOVA showed that glass-ionomer cements (Fuji Cap II, Ketac-Bond, Ketac-Fil and Ketac-Molar) had similar antibacterial effects on mutans streptococci and were significantly more effective (P < 0.001) than all other products tested in reducing the biofilm development on their surfaces. The compomers (Dyract, Compoglass F and F 2000) showed a significantly higher value of bacterial colonization than all the other materials (P < 0.001).