Dental materials: official publication of the Academy of Dental Materials Journal Impact Factor & Information

Publisher: Elsevier

Current impact factor: 3.77

Impact Factor Rankings

2015 Impact Factor Available summer 2016
2014 Impact Factor 3.769
2013 Impact Factor 4.16
2012 Impact Factor 3.773
2011 Impact Factor 3.135
2010 Impact Factor 2.92
2009 Impact Factor 2.882
2008 Impact Factor 2.941
2007 Impact Factor 2.99
2006 Impact Factor 2.381
2005 Impact Factor 2.056
2004 Impact Factor 2.057
2003 Impact Factor 2.064
2002 Impact Factor 1.912
2001 Impact Factor 1.441
2000 Impact Factor 1.016
1999 Impact Factor 0.884
1998 Impact Factor 1.434
1997 Impact Factor 1.34
1996 Impact Factor 1.241
1995 Impact Factor 1.362
1994 Impact Factor 1.601
1993 Impact Factor 1.055
1992 Impact Factor 0.938

Impact factor over time

Impact factor

Additional details

5-year impact 4.43
Cited half-life 6.80
Immediacy index 0.51
Eigenfactor 0.01
Article influence 0.94
ISSN 1879-0097

Publisher details


  • Pre-print
    • Author can archive a pre-print version
  • Post-print
    • Author can archive a post-print version
  • Conditions
    • Authors pre-print on any website, including arXiv and RePEC
    • Author's post-print on author's personal website immediately
    • Author's post-print on open access repository after an embargo period of between 12 months and 48 months
    • Permitted deposit due to Funding Body, Institutional and Governmental policy or mandate, may be required to comply with embargo periods of 12 months to 48 months
    • Author's post-print may be used to update arXiv and RepEC
    • Publisher's version/PDF cannot be used
    • Must link to publisher version with DOI
    • Author's post-print must be released with a Creative Commons Attribution Non-Commercial No Derivatives License
    • Publisher last reviewed on 03/06/2015
  • Classification

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: To investigate the effect of firing protocols on flexural strength, surface roughness, and crystalline structure of a leucite-based glass ceramic. Methods: Discs produced by automated machining were distributed into five groups (n=30) according to the applied firing protocols, conducted above (790°C) or below (575°C) the ceramic transition temperature (Tg) (625±20°C): C - control, no heat treatment; G790 - glaze firing (790°C) for 1.5min (manufacturer-recommended); G790-SC - G790 modified by slow cooling; EGF790-SC - extended G790 for 15min, with slow cooling; and EF575-SC - extended firing below Tg at 575°C for 15min, with slow cooling. Discs were subjected to biaxial flexural tests and results were assessed using Weibull analysis. Surface roughness was measured before and after treatments. One specimen from each group was used for X-ray diffraction (XRD). Results: Highest values of characteristic strength (σ0) were obtained for EGF790-SC (211.7MPa). Regimens EF575-SC, G790-SC, and G790 produced σ0 values (167.9, 157.7, and 153.7MPa, respectively) lower than the control (C) (187.7MPa). The Weibull modulus (m) was statistically similar between groups. All treatments reduced the mean roughness (Ra) of the specimens. Extended cycles (EGF790-SC, EF575-SC) decreased the mean amplitude (Rz). XRD revealed no crystalline phase transformation and slight changes in size of leucite crystallites. Significance: Increased values of fracture strength and decreased surface roughness for a leucite-reinforced glass ceramic are achieved by extended glaze firing after machining. Crystalline structure is not modified. Glaze cycles, manufacturer-recommended or modified by slow cooling, and firing below Tg, significantly reduce fracture strength.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; 31(12). DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: to determine the physicochemical properties of experimental adhesive resins containing hydroxyethyl acrylamide. Methods: Three groups of experimental resin were formulated, GHEAA33% (33.3wt% HEAA+66.6wt% BisGMA), GHEAA50% (50wt% HEAA+50wt% BisGMA), and GHEAA-FREE (33.3wt% HEMA+66.6wt% of BisGMA). The polymerization process of each adhesive resin group, as well as for the homopolymers, BisGMA, HEMA, HEAA, HEMA* without EDAB, and HEAA* without EDAB, was characterized through differential scanning calorimetry (DSC). Elution of monomers was evaluated by (1)H NMR. Dynamic mechanical analysis (DMA) was used to collect the glass transition temperature (Tg), the storage modulus (E') and the reticulation degree (ρ). Flexural strength was calculated by three-point bending test with 0.75mm/min. Softening in solvent was calculated through hardness before and after immersion in water or ethanol. Results: GHEAA50%, GHEAA33%, GHEAA-FREE presented higher polymerization rate ( [Formula: see text] , 12.3 and 5.3mmolg(-1)s(-1), respectively) than homopolymers HEMA, HEMA* and HEAA*. Group with HEAA presented higher degree of conversion (GHEAA50%=64.07%>GHEAA33%=55.82%>GHEAA-FREE=49.02%; p=0.008) All groups presented low elution of monomers (p>0.05). The values of E' were higher on GHEAA33% than GHEAA-FREE (p=0.034). Tg and flexural strength values of GHEAA-FREE were higher than acrylamide groups (p=0.022 and p<0.001, respectively). Hardness varied from 27.05 to 34.78 for water and from 63.27 to 68.51 for ethanol with no difference for ρ values. Significance: The addition of HEAA increased the materials reactivity and, consequently, improved the maximum rate of polymerization, degree of conversion and the storage modulus of experimental adhesive resin.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: To study the effect of resin matrix and maturation time (1 and 24h) on the creep deformation of resin-composites, two of which have matrix-forming monomers that are either bis-GMA free or have an ormocer structure between the CC groups. Methods: Five resin-composites: four commercial and one experimental were investigated. Six specimens were prepared for each material and were divided into two groups (n=3) according to the maturation time and condition. Group A was stored dry at room temperature for 1h and Group B was stored for 24h in distilled water to allow post-curing at 37°C. Each specimen was loaded (20MPa) for 2h and unloaded for 2h. The strain deformation was recorded continuously for 4h. Statistical analysis was performed using one-way ANOVA and the Bonferroni post hoc test at a significance level of a=0.05. Results: The maximum creep-strain % after 1h ranged from 1.32% to 2.50% and was reduced after 24h post-cure to between 0.66% and 1.47%. Also, the permanent set after 1h ranged from 0.70% up to 1.27% (Group A) and after 24h ranged from 0.53% up to 1.20% (Group B). Significance: Creep deformation and maximum recovery for all resin-composites decreased with time, demonstrating improvement in viscoelastic stability. However, there was no significant difference between the permanent set at different times, except for Herculite XRV Ultra. Composites with novel matrices showed comparable properties to existing bis-GMA based materials.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: The purpose of this study was to assess the effect of surface treatment on the fracture resistance of zirconia-based all-ceramic anterior crowns. Methods: Sixty-four zirconia-based all-ceramic anterior crowns, veneered by use of a press-on technique, were produced. For 48 crowns intraoral adjustment was simulated (A-group), 16 crowns remained unadjusted (WA-group). The adjusted area was then treated in three ways: 1. no further surface treatment; 2. polishing, with irrigation, using polishers interspersed with diamond grit for ceramics; and 3. polishing and glaze firing. Half of the specimens were loaded until fracture in an universal testing device without artificial ageing; the other crowns underwent thermocycling and chewing simulation before ultimate-load testing. Explorative statistical analysis was performed by use of non-parametric and parametric tests. In addition, fracture-strength tests according to ISO 6872 were performed for veneer ceramic subjected to the different surface treatments. Finite element analysis was also conducted for the crowns, and surface roughness was measured. Results: Crowns in the A-group were more sensitive to aging than crowns in the WA-group (p=0.038). Although both polishing and glaze firing slightly improved the fracture resistance of the specimens, the fracture resistance in the WA-group (initial fracture resistance (IFR): 652.0±107.7N, remaining fracture resistance after aging (RFR): 560.6±233.3N) was higher than the fracture resistance in the A-group (polished: IFR: 477.9±108.8N, RFR: 386.0±218.5N; glaze firing: IFR: 535.5±128.0N, RFR: 388.6±202.2N). Surface roughness without adjustment was Ra=0.1μm; for adjustment but without further treatment it was Ra=1.4μm; for adjustment and polishing it was Ra=0.3μm; and for adjustment, polishing, and glazing it was Ra=0.6μm. Stress distributions obtained by finite element analysis in combination with fracture strength tests showed that fractures most probably originated from the occlusal surface. Significance: To improve fracture resistance and reduce the incidence of failure, extensive occlusal adjustment of veneered anterior zirconia restorations should be avoided. Neither polishing nor glazing could restore the fracture resistance to the level maintained with unadjusted crowns.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: A commercial restorative material, BondfillSB (BF), is a modification of 4-META/MMA-TBB resin cement. BF uses a self-etching primer and added pre-polymerized organic fillers. We compared BF with another self-etching system, EasyBond (EB), in shear bond strength, bonded interface characteristics to human dentin and contraction gap when used in bulk-filling. Methods: Shear bond strength of BF and EB+Z100 (Z), bonded by different experience-level operators, was evaluated. Bonded interfaces were characterized by SEM, AFM, and AFM based nano-indentation. Contraction gaps (CG) at 0h and 24h after polymerization were evaluated for BF or EB bulk filled class I cavities. To meet the clinical recommendation, BF's powder was replaced by experimental radioopaque powder (BFO) for the CG study. EB was used with Z (EBZ) or with a resin marketed for bulk-fill base (SureFil-SDR-flow (EBSF)). Results: Shear bond strengths (Mean±Standard Deviation (S.D.)) of BF (37.4±2.6MPa; n=36) were higher and less variable than EBZ (18.2±7.6MPa; n=36) (p<0.0001, One-way ANOVA). Weibull characteristic strength (η) differed significantly between materials (p<0.0001) but not between operators (p=0.90). EBZ often had non-uniform interfaces and a wider band of reduced elastic modulus (E) of greater than 20μm across the interface. BF had uniform interfaces and a smaller width of affected dentin under the interface (∼1μm). There was a difference in dentin-E between EBZ and BF up to 9μm from the interface (mixed-effects model; P=0.03). A stratified linear regression model used for CG. EBSF and BFO showed significantly smaller CG than EBZ at time 0. None of three combinations showed any significant change between 0h-CG and 24h-CG. Significance: BF possessed bonding characteristics required to serve as a restorative.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; 31(12):1567–1578. DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: To evaluate degree of conversion (DC), Knoop microhardness (KHN), internal marginal adaptation (IA), and polymerization shrinkage stress (PS) of one conventional and four bulk-fill composites. Methods: Bulk-fill composites tested were Surefil SDR (SDR), Filtek Bulk-Fill (FBF), Tetric EvoCeram Bulk-Fill (TEC), and EverX Posterior (EXP). The conventional composite Herculite Classic (HER) was tested using both incremental and bulk-fill insertion techniques. Standardized Class I preparations (4-mm-depth) were made in extracted molars and restored with each product system (N=5). After 1-week wet storage, restorations were cross-sectioned and DC and KHN were evaluated at four depths (1, 2, 3, and 4mm) using confocal Raman spectroscopy and KHN techniques, respectively. Epoxy resin replicas of restorations were evaluated using scanning electron microscopy for IA. PS was determined using composite bonded to acrylic rods attached to a universal testing machine (N=5). Results: Within bulk-fill products, only SDR and FBF demonstrated similar DC at all depths, and KHN values did not statistically differ among depths, except for TEC. Neither placement method nor depth affected KHN or DC, except the DC of HER bulk-fill at 4mm. Incrementally layered HER, and bulk-fills SDR and TEC demonstrated the lowest proportion of internal gaps. Highest and lowest PS values were measured for EXP and TEC, respectively. Significance: DC with depth was not uniform among all bulk-fill materials, although no difference in KHN was found. Higher PS correlated positively with higher proportion of interfacial gaps. The incremental technique using conventional composite showed reduced gap formation.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Swept-source optical coherence tomography (SS-OCT) and micro-CT can be useful non-destructive methods for evaluating internal adaptation. There is no comparative study evaluating the two methods in the assessment of internal adaptation in composite restoration. The purpose of this study was to compare internal adaptation measurements of SS-OCT and micro-CT. Two cylindrical cavities were created on the labial surface of twelve bovine incisors. The 24 cavities were randomly assigned to four groups of dentin adhesives: (1) three-step etch-and-rinse adhesive, (2) two-step etch-and-rinse adhesive, (3) two-step self-etch adhesive, and (4) one-step self-etch adhesive. After application, the cavities were filled with resin composite. All restorations underwent a thermocycling challenge, and then, eight SS-OCT images were taken using a Santec OCT-2000™ (Santec Co., Komaki, Japan). The internal adaptation was also evaluated using micro-CT (Skyscan, Aartselaar, Belgium). The image analysis was used to calculate the percentage of defective spot (%DS) and compare the results. The groups were compared using one-way ANOVA with Duncan analysis at the 95% significance level. The SS-OCT and micro-CT measurements were compared with a paired t-test, and the relationship was analyzed using a Pearson correlation test at the 95% significance level. The %DS results showed that Group 3≤Group 4<Group 1≤Group 2 on both SS-OCT and micro-CT images. The %DSs on micro-CT were lower than SS-OCT (p<0.05) and the Pearson correlation coefficient between SS-OCT and micro-CT was r=0.787 (p<0.05).
    Dental materials: official publication of the Academy of Dental Materials 11/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: The aim of this study was to assess monomer elution from bulk-fill and conventional resin-composites stored in different media using high performance liquid chromatography (HPLC) for up to 3 months. Methods: Six bulk-fill (SureFil SDR, Venus Bulk Fill, X-tra base, Filtek Bulk Fill flowable, Sonic Fill, and Tetric EvoCeram Bulk Fill) and eight conventional resin-composites (Grandioso Flow, Venus Diamond Flow, X-Flow, Filtek Supreme XTE, Grandioso, Venus Diamond, TPH Spectrum, and Filtek Z250) were tested. Cylindrical samples (n=5) were immersed in water, 70% ethanol/water solution (70% E/W), and artificial saliva and stored at 37°C for 24h, 1 month, and 3 months. The storage solutions were analysed with HPLC. Data were analysed with repeated measures ANOVA, one-way ANOVA, and Tukey post hoc test at α=0.05. Results: Monomers detected in water and artificial saliva were TEGDMA, DEGDMA, UDMA, and TCD-DI-HEA. No eluted monomers were detected from X-tra base and Sonic fill in these media. All monomers showed a variable extent of elution into 70% E/W with significantly higher amounts than those detected in water and artificial saliva. Significantly higher elution was detected from UDMA-BisEMA based composites compared to BisGMA and BisGMA-BisEMA based systems in 70% E/W. The rate of elution into different media varied between different monomers and was highly dependent on the molecular weight of the eluted compounds. Significance: Elution from bulk-fill resin-composites is comparable to that of conventional materials despite their increased increment thickness. Monomer elution is highly dependent on the hydrophobicity of the base monomers and the final network characteristics of the resin-matrix.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: This study investigated the effects of bacterial biofilm on the surface properties of novel bioactive glass (BAG)-containing composites of different initial surface roughness. Methods: BAG (65mol% Si; 4% P; 31% Ca) and BAG-F (61% Si; 31% Ca; 4% P; 3% F; 1% B) were synthesized by the sol-gel method and micronized (size ∼0.1-10μm). Composites with 72wt% total filler load were prepared by replacing 15% of the silanized Sr glass with BAG, BAG-F, or silanized silica. Specimens (n=10/group) were light-cured and divided into 4 subgroups of different surface roughness by wet polishing with 600 and then up to 1200, 2400, or 4000 grit SiC. Surface roughness (SR), gloss, and Knoop microhardness were measured before and after incubating in media with or without a Streptococcus mutans (UA 159) biofilm for 2 weeks. Results were analyzed with ANOVA/Tukey's test (α=0.05). Results: The SR of the BAG-containing composites with the smoothest surfaces (2400/4000 grit) increased in media or bacteria; the SR of the roughest composites (600 grit) decreased. The gloss of the smoothest BAG-containing composites decreased in bacteria and media-only, but more in media-alone. The microhardness of all of the composites decreased with exposure to media or bacteria, with BAG-containing composites affected more than the control. Significance: Exposure to bacterial biofilm and its media produced enhanced roughness and reduced gloss and surface microhardness of highly polished dental composites containing a bioactive glass additive, which could affect further biofilm formation, as well as the esthetics, of restorations made from such a material.
    Dental materials: official publication of the Academy of Dental Materials 11/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: The functional monomer 10-MDP has been considered as one of the best performing functional monomers for dental adhesives. Different adhesives containing 10-MDP are commercially available, among which many so-called 'universal' adhesives. We hypothesize that the quality of the functional monomer 10-MDP in terms of purity may affect bonding performance. Methods: We therefore characterized three different 10-MDP versions (10-MDP_KN provided by Kuraray Noritake; 10-MDP_PCM provided by PCM; 10-MDP_DMI provided by DMI) using NMR, and analyzed their ability to form 10-MDP_Ca salts on dentin using XRD. The 'immediate' and 'aged' micro-tensile bond strength (μTBS) to dentin of three experimental 10-MDP primers was measured. The resultant interfacial adhesive-dentin ultra-structure was characterized using TEM. Results: NMR disclosed impurities and the presence of 10-MDP dimer in 10-MDP_PCM and 10-MDP_DMI. 10-MDP_PCM and 10-MDP_DMI appeared also sensitive to hydrolysis. 10-MDP_KN, on the contrary, contained less impurities and dimer, and did not undergo hydrolysis. XRD revealed more intense 10-MDP_Ca salt deposition on dentin induced by 10-MDP_KN. The adhesive based on the experimental 10-MDP_KN primer resulted in a significantly higher 'immediate' bond strength that remained stable upon aging; the μTBS of the experimental 10-MDP_PCM and 10-MDP_DMI adhesives significantly dropped upon aging. TEM revealed thicker hybridization and more intense nano-layering for 10-MDP_KN. Significance: It was concluded that primer impurities and the presence of 10-MDP dimer affected not only hybridization, but also reduced the formation of 10-MDP_Ca salts and nano-layering. 10-MDP in a high purity grade is essential to achieve durable bonding.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: Evaluate the effect of environment on post-gel shrinkage (Shr), cuspal strains (CS), microtensile bond strength (μTBS), elastic modulus (E) and shrinkage stress in molars with large class II restorations. Methods: Sixty human molars received standardized Class II mesio-oclusal-distal cavity preparations. Restorations were made with two composites (CHA, Charisma Diamond, Heraus Kulzer and IPS Empress Direct, Ivoclar-Vivadent) using three environment conditions (22°C/50% humidity, 37°C/50% humidity and 37°C/90% humidity) simulated in custom developed chamber. Shr was measured using the strain gauge technique (n=10). CS was measured using strain gauges. Half of the teeth (n=5) were used to assess the elastic modulus (E) and Knoop hardness (KHN) at different depths using microhardness indentation. The other half (n=5) was used to measure the μTBS. The composites and environment conditions were simulated in a two-dimensional finite element analysis of a tooth restoration. Polymerization shrinkage was modeled using Shr data. The Shr, CS, μTBS, KHN and E data were statistically analyzed using two-way ANOVA and Tukey test (significance level: 0.05). Results: Both composites had similar Shr, CS, μTBS and shrinkage stress. CHA had higher elastic modulus than IPS. Increasing temperature and humidity significantly increased Shr, CS and shrinkage stress. μTBS were similar for groups with lower humidity, irrespective of temperature, and higher with higher humidity. E and KHN were constant through the depth for CHA. E and KHN values were affected by environment only for IPS, mainly deeper in the cavity. Shrinkage stress at dentin/composite interface had high inverse correlation with μTBS. Shrinkage stress in enamel had high correlation with CS. Conclusions: Increasing temperature and humidity caused higher post-gel shrinkage and cusp deformation with higher shrinkage stresses in the tooth structure and tooth/restoration interface for both composites tested. The chamber developed for simulating the oral environment conditions will improve the realism of in vitro studies. Clinical significance Simulating oral temperature and humidity is important to better determine the biomechanical behavior of composite resin restoration. Avoiding high humidity during restorative procedures using rubber dam isolation may reduce cuspal deformation and shrinkage stress and improve the bonding strength of posterior composite restorations.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: The aim of this study was to investigate the viscoelastic properties and creep behavior of bulk fill composites under different conditions and evaluate their degree of conversion. Methods: Seven bulk fill composites were examined: everX Posterior (EV), SDR (SD), SonicFill (SF), Tetric EvoCeram Bulk Fill (TE), Venus Bulk Fill (VE), x-tra base (XB) and x-tra fil (XF). Each material was tested at 21°C, 37°C and 50°C under dry and wet conditions by applying a constant torque for static and creep testing and dynamic torsional loading for dynamic testing. Degree of conversion (%DC) was measured on the top and bottom surfaces of composites with ATR-FTIR spectroscopy. Statistical analysis was performed with two-way ANOVA, Bonferroni's post hoc test and Pearson's correlation coefficient. Results: Shear modulus G ranged from 2.17GPa (VE) to 8.03GPa (XF) and flexural modulus E from 6.16GPa (VE) to 23GPa (XF) when the materials were tested dry at 21°C. The increase of temperature and the presence of water lead to a decline of these properties. Flowable materials used as base composites in restorations showed significantly lower values (p<0.05) than non-base composites, while being more prone to creep deformation. %DC ranged from 47.25% (XF) to 66.67% (SD) at the top material surface and 36.06% (XF) to 63.20% (SD) at the bottom. Significance: Bulk fill composites exhibited significant differences between them with base flowable materials showing in most cases inferior mechanical properties and higher degree of conversion than restorative bulk fill materials.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: Additive manufacturing, which is more colloquially referred to as 3D printing, is quickly approaching mainstream adoption as a highly flexible processing technique that can be applied to plastic, metal, ceramic, concrete and other building materials. However, taking advantage of the tremendous versatility associated with in situ photopolymerization as well as the ability to select from a variety of preformed processible polymers, 3D printing predominantly targets the production of polymeric parts and models. The goal of this review is to connect the various additive manufacturing techniques with the monomeric and polymeric materials they use while highlighting emerging material-based developments. Methods: Modern additive manufacturing technology was introduced approximately three decades ago but this review compiles recent peer-reviewed literature reports to demonstrate the evolution underway with respect to the various building techniques that differ significantly in approach as well as the new variations in polymer-based materials being employed. Results: Recent growth of 3D printing has been dramatic and the ability of the various platform technologies to expand from rapid production prototypic models to the greater volume of readily customizable production of working parts is critical for continued high growth rates. This transition to working part production is highly dependent on adapting materials that deliver not only the requisite design accuracy but also the physical and mechanical properties necessary for the application. Significance: With the weighty distinction of being called the next industrial revolution, 3D printing technologies is already altering many industrial and academic operations including changing models for future healthcare delivery in medicine and dentistry.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: In pulpal revascularization, a protective material is placed coronal to the blood clot to prevent recontamination and to facilitate osteogenic differentiation of mesenchymal stem cells to produce new dental tissues. Although mineral trioxide aggregate (MTA) has been the material of choice for clot protection, it is easily displaced into the clot during condensation. The present study evaluated the effects of recently introduced calcium silicate cements (Biodentine and TheraCal LC) on the viability and osteogenic differentiation of human dental pulp stem cells (hDPSCs) by comparing with MTA Angelus. Methods: Cell viability was assessed using XTT assay and flow cytometry. The osteogenic potential of hDPSCs exposed to calcium silicate cements was examined using qRT-PCR for osteogenic gene expressions, alkaline phosphatase enzyme activity, Alizarin red S staining and transmission electron microscopy of extracellular calcium deposits. Parametric statistical methods were employed for analyses of significant difference among groups, with α=0.05. Results: The cytotoxic effects of Biodentine and TheraCal LC on hDPSCs were time- and concentration-dependent. Osteogenic differentiation of hDPSCs was enhanced after exposure to Biodentine that was depleted of its cytotoxic components. This effect was less readily observed in hDPSCs exposed to TheraCal LC, although both cements supported extracellular mineralization better than the positive control (zinc oxide-eugenol-based cement). Significance: A favorable tissue response is anticipated to occur with the use of Biodentine as a blood clot-protecting material for pulpal revascularization. Further investigations with the use of in vivo animal models are required to validate the potential adverse biological effects of TheraCal LC on hDPSCs.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: Low-temperature-degradation (LTD) has been reported to cause property changes in yttria-tetragonal zirconia polycrystals (Y-TZP). The current study measured monoclinic phase transformation of Y-TZP with different grain sizes and corresponding property changes due to artificial aging. Null hypothesis: the grain size of aged Y-TZP will not influence its transformation, roughness, hardness or modulus of elasticity. Methods: Four groups of Y-TZP were examined with differing grain sizes (n=5). The line intercept technique was used to determine grain sizes on SEM images (100,000×). Artificial aging was accomplished by autoclaving at 2bar pressure for 5h. X-ray diffraction (30mA, 40kV) was used to measure tetragonal to monoclinic transformation (t→m). Surface roughness analysis was performed using a non-contact surface-profilometer. Nano-hardness and modulus of elasticity were measured using nano-indentation. Results: SEM analyses showed different grain sizes for each sample group (0.350μm, 0.372μm, 0.428μm, and 0.574μm). The fraction of t→m transformation increased as grain size increased; furthermore, aging of zirconia caused increased roughness. Modulus and hardness after aging displayed no significant correlation or interaction with grain size. Significance: Smaller grains caused less transformation, and aging caused increased roughness, but grain size did not influence the amount of increased surface roughness. Future studies are needed to determine the effects of grain size on the wear and fracture properties of dental zirconia.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: The purpose of this study was to investigate a range of variables affecting the synthesis of a miserite glass-ceramic (GC). Methods: Miserite glass was synthesized by the melt quench technique. The crystallization kinetics of the glass were determined using Differential Thermal Analysis (DTA). The glasses were ground with dry ball-milling and then sieved to different particle sizes prior to sintering. These particle sizes were submitted to heat treatment regimes in a high temperature furnace to form the GC. The crystal phases of the GC were analyzed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to examine the microstructure of the cerammed glass. Results: XRD analysis confirmed that the predominant crystalline phase of the GC was miserite along with a minor crystalline phase of cristobalite only when the particle size is <20μm and the heat treatment at 1000°C was carried out for 4h and slowly cooled at the furnace rate. For larger particle sizes and faster cooling rates, a pseudowollastonite crystalline phase was produced. Short sintering times produced either a pseudowollastonite or xonotolite crystalline phase. Significance: The current study has shown that particle size and heat treatment schedules are major factors in controlling the synthesis of miserite GC.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: To evaluate the flexural strength, Weibull modulus, fracture toughness, and failure behavior of ceramic structures obtained by the CAD-on technique, testing the null hypothesis that trilayer structures show similar properties to monolithic structures. Methods: Bar-shaped (1.8mm×4mm×16mm) monolithic specimens of zirconia (IPS e.max ZirCAD - Ivoclar Vivadent) and trilayer specimens of zirconia/fusion ceramic/lithium dissilicate (IPS e.max ZirCAD/IPS e.max CAD Crystall./Connect/IPS e.max CAD, Ivoclar Vivadent) were fabricated (n=30). Specimens were tested in flexure in 37°C deionized water using a universal testing machine at a crosshead speed of 0.5mm/min. Failure loads were recorded, and the flexural strength values were calculated. Fractography principles were used to examine the fracture surfaces under optical and scanning electron microscopy. Data were statistically analyzed using Student's t-test and Weibull statistics (α=0.05). Results: Monolithic and trilayer specimens showed similar mean flexural strengths, characteristic strengths, and Weibull moduli. Trilayer structures showed greater mean critical flaw and fracture toughness values than monolithic specimens (p<0.001). Most critical flaws in the trilayer groups were located on the Y-TZP surface subjected to tension and propagated catastrophically. Trilayer structures showed no flaw deflection at the interface. Significance: Considering the CAD-on technique, the trilayer structures showed greater fracture toughness than the monolithic zirconia specimens.
    Dental materials: official publication of the Academy of Dental Materials 10/2015; DOI:10.1016/