Dental Materials RSS feed: Current Issue. Online submission and editorial system now available at http://ees.elsevier.com/dema Dental Materials publishes original research, review articles, and short communications. Academy of Dental Materials members click here here to register for free access to Dental Materials online. The principal aim of Dental Materials is to promote rapid communication of scientific information between academia, industry, and the dental practitioner. Original Manuscripts on clinical and laboratory research of basic and applied character which focus on the properties or performance of dental materials or the reaction of host tissues to materials are given priority publication. Other acceptable topics include application technology in clinical dentistry and dental laboratory technology. Comprehensive reviews and editorial commentaries on pertinent subjects will be considered. Only manuscripts... http://www.demajournal.com/?rss=yesElsevier Inc.en © 2012 Published by Elsevier Inc. All rights reserved. Dental Materials0109-5641282February 2012 © 2012 Published by Elsevier Inc. All rights reserved. healthpermissions@elsevier.comhttp://www.demajournal.com/article/PIIS0109564112000036/abstract?rss=yesEditorial Board10.1016/S0109-5641(12)00003-6Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2CO2CO2http://www.demajournal.com/article/PIIS0109564111008384/abstract?rss=yesAbstract: Objectives: To evaluate the effects of silica (SiO2) (0.5wt%) and zinc oxide (ZnO) (0.25wt%) dopants on the mechanical and biological properties of tricalcium phosphate (TCP) scaffolds with three dimensionally (3D) interconnected pores.Methods: Scaffolds were created with a commercial 3D printer. Post sintering phase analysis was determined by X-ray diffraction. Surface morphology of the scaffolds was examined by field emission scanning electron microscopy (FESEM). Mechanical strength was evaluated with a screw driven universal testing machine. MTT assay was used for cellular proliferation characteristics and cellular morphology was examined by FESEM.Results: Addition of dopants into TCP increased the average density of pure TCP from 90.8±0.8% to 94.1±1.6% and retarded the β to α phase transformation at high sintering temperatures, which resulted in up to 2.5 fold increase in compressive strength. In vitro cell–materials interaction studies, carried out using hFOB cells, confirmed that the addition of SiO2 and ZnO to the scaffolds facilitated faster cell proliferation when compared to pure TCP scaffolds.Significance: Addition of SiO2 and ZnO dopants to the TCP scaffolds showed increased mechanical strength as well as increased cellular proliferation.Effects of silica and zinc oxide doping on mechanical and biological properties of 3D printed tricalcium phosphate tissue engineering scaffoldsGary A. Fielding, Amit Bandyopadhyay, Susmita Bose10.1016/j.dental.2011.09.010Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles113122http://www.demajournal.com/article/PIIS0109564111008645/abstract?rss=yesAbstract: Objectives: The C-Factor has been used widely to rationalize the changes in shrinkage stress occurring at the tooth/resin-composite interfaces. Experimentally, such stresses have been measured in a uniaxial direction between opposed parallel walls. The situation of adjoining cavity walls has been neglected. The aim was to investigate the hypothesis that: within stylized model rectangular cavities of constant volume and wall thickness, the interfacial shrinkage-stress at the adjoining cavity walls increases steadily as the C-Factor increases.Methods: Eight 3D-FEM restored Class I ‘rectangular cavity’ models were created by MSC.PATRAN/MSC.Marc, r2-2005 and subjected to 1% of shrinkage, while maintaining constant both the volume (20mm3) and the wall thickness (2mm), but varying the C-Factor (1.9–13.5). An adhesive contact between the composite and the teeth was incorporated. Polymerization shrinkage was simulated by analogy with thermal contraction. Principal stresses and strains were calculated. Peak values of maximum principal (MP) and maximum shear (MS) stresses from the different walls were displayed graphically as a function of C-Factor. The stress-peak association with C-Factor was evaluated by the Pearson correlation between the stress peak and the C-Factor.Results: The hypothesis was rejected: there was no clear increase of stress-peaks with C-Factor. The stress-peaks particularly expressed as MP and MS varied only slightly with increasing C-Factor. Lower stress-peaks were present at the pulpal floor in comparison to the stress at the axial walls. In general, MP and MS were similar when the axial wall dimensions were similar. The Pearson coefficient only expressed associations for the maximum principal stress at the ZX wall and the Z axis.Significance: Increase of the C-Factor did not lead to increase of the calculated stress-peaks in model rectangular Class I cavity walls.Finite element analysis of bonded model Class I ‘restorations’ after shrinkageFlávia P. Rodrigues, Nick Silikas, David C. Watts, Rafael Y. Ballester10.1016/j.dental.2011.10.001Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles123132http://www.demajournal.com/article/PIIS0109564111008967/abstract?rss=yesAbstract: Objectives: The study evaluates properties of an experimental dental composite consisting of a porous thermally sintered nano-silica as filler. The properties are compared with those of an experimental composite containing micro fillers and a commercially available nano-composite, Filtek Supreme® Translucent. Different models are used to predict the elastic modulus and strength of the composites.Methods: Nano-silica with primary particles of 12nm was thermally sintered to form nanoporous filer particles. The experimental composites were prepared by incorporating 70wt.% of the fillers into a mixture of Bis-GMA and TEGDMA as matrix phase. Having added photoinitiator system the composites were inserted into the test molds and light-cured. The microfiller containing composites were also prepared using micron size glass fillers. Degree of conversion (DC%) of the composites was measured using FTIR spectroscopy. Diametral tensile strength (DTS), flexural strength, flexural modulus and fracture toughness were measured. SEM was utilized to study the cross section of the fractured specimens. The surface topography of the specimens was investigated using atomic force microscopy (AFM). The specific surface area of the sintered nano silica was measured using BET method. The data were analyzed and compared by ANOVA and Tukey HSD tests (significance level=0.05).Results: The results showed improvements in flexural modulus and fracture toughness of the composites containing sintered filler. AFM revealed a lower surface roughness for sintered silica containing composites. No significant difference was observed between DTS, DC%, and flexural strength of the sintered nanofiller composite and the Filtek Supreme®. The results also showed that the modulus of the composite with sintered filler was higher than the model prediction.Significance: The thermally sintered nano-porous silica fillers significantly enhanced the mechanical properties of dental composites introducing a new approach to develop materials with improved properties.Nano-porous thermally sintered nano silica as novel fillers for dental compositesMohammad Atai, Ayoub Pahlavan, Niloofar Moin10.1016/j.dental.2011.10.015Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles133145http://www.demajournal.com/article/PIIS0109564111008906/abstract?rss=yesAbstract: Objectives: Inlay-retained fixed partial dentures are conservative prosthetic restorations. Their failure resistance is influenced by the stress distribution that depends on the material properties as well as the loading conditions. Finite element analysis provides the ability to estimate the loading capacity by simulating the stress distribution in all-ceramic dental restorations. The null-hypothesis of this study was that tooth mobility or tooth bearing condition significantly influences the stress distribution and therefore the failure resistance of all-ceramic inlay-retained fixed dental prostheses. Therefore, the stress distribution under different loading and bearing conditions of the teeth was analyzed using the finite element method.Methods: Three different bearing conditions, one fixed and two flexible were chosen to simulate tooth mobility. The flexible models were constrained with spring elements to a virtual center of rotation. In addition, loading conditions were varied.Results: The influence of tooth mobility on the stress distribution depended on the degree of modeled tooth mobility, as well as the loading conditions. The maximum first principal stresses differed significantly in magnitude and location depending on the modeled bearing condition and the simulated load case. The maximum difference between fixed and flexible model was more than 100%.Significance: Tooth mobility and occlusal loading conditions have to be considered in finite element analyses as the simulated stress distribution is strongly influenced by these factors.Influence of tooth mobility on critical stresses in all-ceramic inlay-retained fixed dental prostheses: A finite element studyKristina Möllers, Daniel Parkot, Armin Kirsten, Jan-Frederik Güth, Daniel Edelhoff, Horst Fischer10.1016/j.dental.2011.10.013Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles146151http://www.demajournal.com/article/PIIS0109564111009006/abstract?rss=yesAbstract: Objectives: Dimer acid based metacrylates and TCD-urethane are promoted as new monomers of nano-hybrid resin based composites as alternatives for the conventional BisGMA. Investigations of this study focused on the mechanical and the storage behavior of nano-hybrid resin based composites (RBCs) composed of these new types of monomers in comparison to RBCs using BisGMA.Methods: Flexural strength and modulus were determined in a three-point-bending test. Additionally, the modulus of elasticity was measured on microscopic scale (Emicro) using an automatic microhardness indenter. Tests were performed on samples after 24h storage in distilled water, as well as after thermocycling and storing the materials for four weeks in either distilled water, artificial saliva or ethanol.Results: The six measured materials showed a pronounced decrease of flexural strength, flexural modulus and Emicro after four weeks storage in alcohol. Results after four weeks storage in water and saliva could not be proven to be significantly different. The most sensitive factor of influence on all test parameters was the material.Significance: Nano-hybrid composites with new or conventional monomers performed similar in regard to the mechanical properties and the behavior of the materials after aging.The mechanical stability of nano-hybrid composites with new methacrylate monomers for matrix compositionsChristine Schmidt, Nicoleta Ilie10.1016/j.dental.2011.11.007Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles152159http://www.demajournal.com/article/PIIS0109564111009018/abstract?rss=yesAbstract: Objectives: The veneering process of frameworks induces residual stresses and can initiate cracks when combined with functional stresses. The stress distribution within the veneering ceramic as a function of depth is a key factor influencing failure by chipping. This is a well-known problem with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objective of this study is to investigate the influence of veneer thickness on the stress profile in zirconia- and metal-based structures.Methods: The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. The stress profile was measured in bilayered disc samples of 20mm diameter, with a 1mm thick zirconia or metal framework. Different veneering ceramic thicknesses were performed: 1mm, 1.5mm, 2mm, 2.5mm and 3mm.Results: All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth up to 0.5–1.0mm from the surface, and then becoming compressive again near the framework, except for the 1.5mm-veneered zirconia samples which exhibited interior tensile stresses. Stresses in the surface of metal samples were not influenced by veneer thickness. Variation of interior stresses at 1.2mm from the surface in function of veneer thickness was inverted for metal and zirconia samples.Significance: Veneer thickness influences in an opposite way the residual stress profile in metal- and in zirconia-based structures. A three-step approach and the hypothesis of the crystalline transformation are discussed to explain the less favorable residual stress development in zirconia samples.Influence of veneer thickness on residual stress profile in veneering ceramic: Measurement by hole-drillingAmélie K. Mainjot, Gary S. Schajer, Alain J. Vanheusden, Michaël J. Sadoun10.1016/j.dental.2011.11.008Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles160167http://www.demajournal.com/article/PIIS0109564111009225/abstract?rss=yesAbstract: Objective: Dentin hypersensitivity (DH) is a commonly occurring dental condition, and bioactive glasses (BG) are used in dentifrice formulations for treating DH by forming a surface layer of hydroxycarbonate apatite (HCA) on the tooth, thereby occluding exposed dentinal tubules. Fluoride-containing BG, however, form fluorapatite, which is more stable toward acid attack, and provide a more sustainable option for treating DH.Methods: Melt-derived multi-component BG (SiO2–P2O5–CaO–CaF2–SrO–SrF2–ZnO–Na2O–K2O) with increasing CaF2+SrF2 content (0–32.7mol%) were prepared. Apatite formation, occlusion of dentinal tubules in dentin discs and ion release in Tris buffer were characterized in vitro over up to 7 days using X-ray diffraction, infrared spectroscopy, scanning electron microscopy and inductively coupled plasma emission spectroscopy.Results: The fluoride-containing bioactive glasses formed apatite from as early as 6h, while the fluoride-free control did not form apatite within 7 days. The glasses successfully occluded dentinal tubules by formation of apatite crystals and released ions such as fluoride, strontium and potassium.Significance: Fluoride significantly improved apatite formation of the BG, allowing for treatment of DH by occlusion of dentinal tubules. The BG also released therapeutically active ions, such as strontium and fluoride for caries prevention, zinc for bactericidal properties and potassium, which is used as a desensitizing agent in dentifrices.Multi-component bioactive glasses of varying fluoride content for treating dentin hypersensitivityEilis Lynch, Delia S. Brauer, Natalia Karpukhina, David G. Gillam, Robert G. Hill10.1016/j.dental.2011.11.021Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles168178http://www.demajournal.com/article/PIIS0109564111009390/abstract?rss=yesAbstract: Objectives: We aimed to achieve detailed biomaterials characterization of a drug delivery system for local periodontitis treatment based on electrospun metronidazole-loaded resorbable polylactide (PLA) fibers.Methods: PLA fibers loaded with 0.1–40% (w/w) MNA were electrospun and were characterized by SEM and DSC. HPLC techniques were used to analyze the release profiles of metronidazole (MNA) from these fibers. The antibacterial efficacy was determined by measuring inhibition zones of drug-containing aliquots from the same electrospun fiber mats in an agar diffusion test. Three pathogenic periodontal bacterial strains: Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were studied. Cytotoxicity testing was performed with human gingival fibroblasts by: (i) counting viable cells via live/dead staining methods and (ii) by exposing cells directly onto the surface of MNA-loaded fibers.Results: MNA concentration influenced fiber diameters and thus w/w surface areas: diameter being minimal and area maximal at 20% MNA. HPLC showed that these 20% MNA fibers had the fastest initial MNA release. From the third day, MNA release was slower and nearly linear with time. All fiber mats released 32–48% of their total drug content within the first 7 days. Aliquots of media taken from the fiber mats inhibited the growth of all three bacterial strains. MNA released up to the 28th day from fiber mats containing 40% MNA significantly decreased the viability of F. nucleatum and P. gingivalis and up to the 2nd day also for the resistant A. actinomycetemcomitans. All of the investigated fibers and aliquots showed excellent cytocompatibility.Significance: This study shows that MNA-loaded electrospun fiber mats represent an interesting class of resorbable drug delivery systems. Sustained drug release properties and cytocompatibility suggest their potential clinical applicability for the treatment of periodontal diseases.Release of metronidazole from electrospun poly(l-lactide-co-d/l-lactide) fibers for local periodontitis treatmentMarkus Reise, Ralf Wyrwa, Ulrike Müller, Matthias Zylinski, Andrea Völpel, Matthias Schnabelrauch, Albrecht Berg, Klaus D. Jandt, David C. Watts, Bernd W. Sigusch10.1016/j.dental.2011.12.006Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles179188http://www.demajournal.com/article/PIIS0109564111008724/abstract?rss=yesAbstract: Objectives: This study characterized the feldspathic ceramic surfaces after various silanization protocols.Methods: Ceramic bars (2mm×4mm×10mm) (N=18) of feldpathic ceramic (VM7, VITA Zahnfabrik) were manufactured and finished. Before silane application, the specimens were ultrasonically cleaned in distilled water for 10min. The ceramic specimens were randomly divided into nine groups (N=2 per group) and were treated with different silane protocols. MPS silane (ESPE-Sil, 3M ESPE) was applied to all specimens and left to react at 20°C for 2min (G20). After drying, the specimens were subjected to heat treatment in an oven at 38°C (G38), 79°C (G79) or 100°C (G100) for 1min. Half of the specimens of each group were rinsed with water at 80°C for 15s (G20B, G38B, G79B, G100B). The control group (GC) received no silane. Attenuated total reflection infrared Fourier transform analysis (ATR FT-IR) was performed using a spectrometer. Thickness of silane layer was measured using a spectroscopic ellipsometer working in the λ=632.8nm (He–Ne laser) at 70° incidence angle. Surface roughness was evaluated using an optical profilometer. Specimens were further analyzed under the Scanning Electron Microscopy (SEM) to observe the topographic patterns.Results: ATR FT-IR analysis showed changes in Si–O peaks with enlarged bands around 940cm−1. Ellipsometry measurements showed that all post-heat treatment actions reduced the silane film thickness (30.8–33.5nm) compared to G20 (40nm). The groups submitted to rinsing in hot water (B groups) showed thinner silane films (9.8–14.4nm) than those of their corresponding groups (without washing) (30.8–40nm). Profilometer analysis showed that heat treatments (Ra≈0.10–0.19μm; Rq≈0.15–0.26μm) provided a smoother surface than the control group (Ra≈0.48μm; Rq≈0.65μm). Similar patterns were also observed in SEM images.Significance: Heat treatment after MPS silane application improved the silane layer network. Rinsing with boiling water eliminated the outmost unreacted regions of the silane yielding to thinner film thicknesses.Surface characterization of feldspathic ceramic using ATR FT-IR and ellipsometry after various silanization protocolsJosé Renato Cavalcanti Queiroz, Paula Benetti, Mutlu Özcan, Luiz Fernando Cappa de Oliveira, Alvaro Della Bona, Fernando Eidi Takahashi, Marco Antonio Bottino10.1016/j.dental.2011.10.009Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles189196http://www.demajournal.com/article/PIIS0109564111008700/abstract?rss=yesAbstract: Objectives: We investigated the elastic properties of one dental restoration resin composite of common use, Venus Diamond, at submicrometer spatial resolution.Methods: We performed both nanoindentation experiments with atomic force microscopy, and microindentation experiments with a traditional indenter setup. We also used scanning electron microscopy and energy dispersive X-rays spectroscopy to better understand the correlation between properties and microscopic structure and composition.Results: With atomic force microscopy we obtained quantitative evaluation of the elastic modulus (10.8±4.3GPa), in agreement with the microindentation value (reduced modulus of 12.7±2.0GPa), and by microindentation we also obtained an hardness value (460±109MPa) compatible in turn with the nominal value provided by the material manufacturer (H∼578MPa). The nanoindentation also revealed that no relevant difference in elasticity appears between the 5 and 10μm diameter filler particles and the surrounding areas, showing an excellent uniformity of the composite. In support of this finding, compositional uniformity of the material was also observed by X-rays spectroscopy. We conclude that the composite contains prepolymerized particles.Significance: We demonstrate that, in addition to reliable quantitative analysis, the high resolution and two-dimensional mapping capability of atomic force microscopy allows for advanced insights into the microstructure of the composite that are not accessible via traditional microindentation.Atomic force microscopy nanoindentation of a dental restorative midifill compositeMarco Salerno, Niranjan Patra, Alberto Diaspro10.1016/j.dental.2011.10.007Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles197203http://www.demajournal.com/article/PIIS0109564111008694/abstract?rss=yesAbstract: Objectives: The purposes of this study were: (1) to determine the light transmission characteristics (straight-line and diffusion transmission) of bulk-filled and layered resin composites, and (2) to evaluate the effect of layering filling on translucency and color appearance of resin composites.Methods: Three light-cured resin composites (EsteliteΣ, Tokuyama Dental; Beautifil II, Shofu and Clearfil Majesty, Kuraray Medical) in A2 and OA2 shades were used in this study. 2mm-thick resin composite discs were prepared by two methods; bulk filling technique (2mm filling at one time), layering technique (two layers each 1mm thickness). The transmitted light intensity of each resin composite disc was measured using a goniophotometer, and diffusion factor (DF), an indicator for diffuse transmission property, and peak gain (G0) for straight-line transmission were calculated from the light distribution graphs. Color was measured according to the CIELAB color scale on a spectrophotometer, and the translucency parameter (TP) and color difference (ΔE*) between bulk-filled and layered specimens were calculated. The data were statistically analyzed using three-way ANOVA, and Dunnett's T3 and t-test for post-hoc test.Results: Three-way ANOVA revealed that the layered specimens had significantly lower G0 values and higher DF values than the bulk-filled specimens, and significantly reduced TP values. The color differences (ΔE*) ranged from 1.07 to 1.85 between the bulk-filled and layered specimens.Significance: Resin composite placed in layers exhibited reduced straight-line light transmission and increased diffusion transmission compared with bulk-filled resin composite. The layering technique affected the translucency and color rendition of resin composite.Influences of composite–composite join on light transmission characteristics of layered resin compositesKanako Horie, Masatoshi Nakajima, Keiichi Hosaka, Kimisuke Kainose, Azusa Tanaka, Richard M. Foxton, Junji Tagami10.1016/j.dental.2011.10.006Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles204211http://www.demajournal.com/article/PIIS0109564111008682/abstract?rss=yesAbstract: Objectives: The aim of this study was to develop a new method to measure the polymerization shrinkage of light cured composites and to evaluate the overall utility and significance of the technique.Methods: An optical instrument to measure the linear polymerization shrinkage of composites without directly contacting the specimen was developed using a particle tracking method with computer vision. The measurement system consisted of a CCD color video camera, a lens, an image storage device, and image processing and analysis software. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and a flowable Z350) were investigated and compared with the data measured using the “bonded disc method”.Results: The linear shrinkage of the composites was 0.33–1.41%. The shrinkage value was lowest for the silorane-based (P90) composite and highest for the flowable Z350 composite. The estimated volume shrinkages of the materials were comparable to the axial shrinkages measured with the bonded disc method.Significance: The new instrument was able to measure the true linear shrinkage of composites without sensitivity to the specimen geometry and the viscosity of the material. Therefore, this instrument can be used to characterize the shrinkage kinetics for a wide range of commercial and experimental visible-light-cure materials in relation to the composition and chemistry.A new method to measure the polymerization shrinkage kinetics of composites using a particle tracking method with computer visionIn-Bog Lee, Sun-Hong Min, Deog-Gyu Seo10.1016/j.dental.2011.10.005Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles212218http://www.demajournal.com/article/PIIS0109564111008670/abstract?rss=yesAbstract: Objectives: The widespread incidence of recurrent caries highlights the need for improved dental restorative materials. The objective of this study was to synthesize low viscosity ionic dimethacrylate monomers (IDMAs) that contain quaternary ammoniums groups (antimicrobial functionalities) and are compatible with existing dental dimethacrylate-based monomers. Such monomers have the potential to copolymerize with other methacrylate monomers and produce antibacterial polymers.Methods: Two monomers (IDMA-1 and IDMA-2) were synthesized using the Menschutkin reaction and incorporated at 0–30% (by mass) into a 1:1 (by mass) bisphenol A glycerolate dimethacrylate (BisGMA):triethylene glycol dimethacrylate (TEGDMA) resin. Resin viscosity was quantified using rheology, and polymer degree of conversion (DC) and surface charge density were measured using Fourier transform infrared spectroscopy (FTIR) and fluorescein binding, respectively. Effects of IDMA-1 on initial attachment of Streptococcus mutans and on viability and metabolic activity (via reductase enzymes) of RAW 264.7 macrophage-like cells were quantified.Results: IDMA-1 and IDMA-2 were prepared and characterized. IDMA-1 was miscible with BisGMA:TEGDMA and slightly increased the resin viscosity and DC. As expected, polymeric surface charge density increased with increasing IDMA-1. Incorporation of 10% IDMA-1 into BisGMA:TEGDMA reduced bacterial colonization without affecting viability or metabolic activity of mammalian cells. Increasing IDMA-1 up to 30% had no additional effect on bacterial coverage, but ≥20% IDMA-1 significantly reduced macrophage density, viability, and metabolic activity. Leachables from polymers containing IDMA-1 were not cytotoxic.Significance: The Menschutkin reaction provides a facile, convenient means to synthesize new monomers with quaternary ammonium groups for dental and medical applications.Synthesis and characterization of dimethacrylates containing quaternary ammonium functionalities for dental applicationsJoseph M. Antonucci, Diana N. Zeiger, Kathy Tang, Sheng Lin-Gibson, Bruce O. Fowler, Nancy J. Lin10.1016/j.dental.2011.10.004Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Original articles219228http://www.demajournal.com/article/PIIS0109564111008888/abstract?rss=yesAbstract: Objectives: Four commercial glass-ionomer cements have been studied for their ability to take up fluoride from aqueous solution following variable maturation times in the dry at 37°C.Methods: Sets of five specimens of four different materials were cured for times of 10min, 24h and 1 month, then transferred to a neutral solution of NaF at approximately 1000ppm in fluoride. Fluoride concentration was then measured at regular time intervals up to 1 month using a fluoride ion selective electrode.Results: Specimens cured for 1 month showed little or no uptake over 24h, specimens cured for 24h showed fluctuating uptake over time, and specimens cured for 10min showed the greatest fluoride uptake. For the latter specimens, simple kinetic models were found to apply in two cases (pseudo-first order and pseudo-second order for Chemflex and Ketac Molar Quick respectively).Significance: The ability to take up fluoride has been shown to decline with age of cement which suggests that in clinical use glass-ionomers may become less effective at undergoing fluoride recharge than has been previously assumed.Maturation affects fluoride uptake by glass-ionomer dental cementsJohn W. Nicholson, Beata Czarnecka10.1016/j.dental.2011.10.011Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Online only articlese1e5http://www.demajournal.com/article/PIIS0109564111009055/abstract?rss=yesAbstract: Objectives: The reliability and longevity of ceramic prostheses have become a major concern. The existing studies have focused on some critical issues from clinical perspectives, but more researches are needed to address fundamental sciences and fabrication issues to ensure the longevity and durability of ceramic prostheses. The aim of this paper was to explore how “sensitive” the thermal and mechanical responses, in terms of changes in temperature and thermal residual stress of the bi-layered ceramic systems and crown models will be with respect to the perturbation of the design variables chosen (e.g. layer thickness and heat transfer coefficient) in a quantitative way.Methods: In this study, three bi-layered ceramic models with different geometries are considered: (i) a simple bi-layered plate, (ii) a simple bi-layer triangle, and (iii) an axisymmetric bi-layered crown.Results: The layer thickness and convective heat transfer coefficient (or cooling rate) seem to be more sensitive for the porcelain fused on zirconia substrate models.Significance: The resultant sensitivities indicate a critical importance of the heat transfer coefficient and thickness ratio of core to veneer on the temperature distributions and residual stresses in each model. The findings provide a quantitative basis for assessing the effects of fabrication uncertainties and optimizing the design of ceramic prostheses.Sensitivity analysis of bi-layered ceramic dental restorationsZhongpu Zhang, Shiwei Zhou, Qing Li, Wei Li, Michael V. Swain10.1016/j.dental.2011.11.012Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Online only articlese6e14http://www.demajournal.com/article/PIIS0109564111009286/abstract?rss=yesAbstract: Objectives: To compare the viscoelastic behavior (creep) of dental resin-composites under both static and cyclic loading in compression.Methods: Ten cylindrical specimens (4mm×6mm), divided into two subgroups (n=5) were prepared from each of four commercial resin-composites, using a divisible stainless steel mold. They were thoroughly cured from all sides. Groups 1 and 2 were loaded statically and dynamically respectively after 1d of fabrication and dry storage. Group 1 was loaded with a constant static load of 35MPa and it was applied for 2h followed by 2h of strain recovery to obtain the static creep (%) and permanent set (%) respectively. To Group 2 a cyclic load between 1MPa and 50MPa was applied at a frequency of 0.25Hz for 30min to obtain the “dynamic” creep strain (%). Regression and correlation analysis (α=0.05) was performed to examine possible correlations between static and “dynamic” creep.Results: For the resin-composite investigated, a good correlation was found between “dynamic” creep strain (%) and maximum static creep strain (%) (r=0.92) and a strong correlation was also found between “dynamic” creep strain (%) and permanent set (%) (r=0.97), Significance: Maximum static creep was significantly higher than “dynamic” creep. A direct numerical equivalence was not expected between static and “dynamic” creep values, as in the case of “dynamic” creep, loading was cyclic and was applied for a shorter overall period. Nevertheless a strong correlation was found between the static and dynamic creep measurement.Viscoelastic stability of resin-composites under static and dynamic loadingMuhammad Kaleem, Konstantinos Masouras, Julian D. Satterthwaite, Nick Silikas, David C. Watts10.1016/j.dental.2011.11.026Dental Materials 28, 2 (2012)2012-02-01Dental Materials2012-02-01282S0109-5641(12)X0002-2Online only articlese15e18