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  1. Daood U, Matinlinna JP, Fawzy AS
    Dent Mater, 2019 02;35(2):356-367.
    PMID: 30528297 DOI: 10.1016/j.dental.2018.11.031
    OBJECTIVE: Effect of d-alpha-tocopheryl poly(ethyleneglycol)-1000-succinate (VE-TPGS) with riboflavin-5'-phosphate solution on crosslinking of dentine collagen was investigated to analyze collagen's structural integrity.

    METHODS: VE-TPGS was added to RF-solution, at RF/VE-TPGS (w/w) ratios of 0.125/0.250 and 0.125/0.500. Demineralized dentine beams were used (10wt.% phosphoric acid), rinsed using deionized-water and analysed using ELISA (Human MMP2 ELISA; Human CTSK/Cathepsin-K for MMP2 and Cathepsin K analysis). AFM of dentine collagen-fibrils structure was done before and after dentine specimens' placement in mineralization solution and tested after 14days in artificial saliva/collagenase (AS/Co) solution. The specimens were tested after 24h in mineralization solution for surface/bulk elastic modulus. Nano-indentation was carried out for each specimen on intertubular-dentine with lateral spacing of 400nm. Reduced elastic-modulus and nano-hardness were calculated and collagen content was determined using hydroxyproline-assay. Micro-Raman were performed. TEM was carried out to study structural variations of dentine-collagen in artificial-saliva (collagenase). Data were presented as mean±standard deviation and analyzed by SPSS v.15, by analysis of variance.

    RESULTS: Synergetic effect of VE-TPGS was observed with RF through higher structural integrity of dentine collagen-fibrils shown by TEM/AFM. Superior surface/bulk mechanical stability was shown by nano-indentation/mechanical testing. Improvement in collagenase degradation resistance for hydroxyproline release was observed and lower endogenous-protease release of MMP-2/Cathepsin-K. Raman-analysis analysed chemical interactions between RF and collagen confirming structural-integrity of collagen fibrils after crosslinking. After 24h mineralization, AFM showed mineral depositions in close association with dentine-collagen fibrils with RF/VE-TPGS formulations.

    SIGNIFICANCE: Potential synergetic effect of RF/VE-TPGS was observed by reflection of higher structural integrity and conformational-stability of dentine-collagen fibrils.

  2. Fawzy AS, Daood U, Matinlinna JP
    Dent Mater, 2019 07;35(7):979-989.
    PMID: 31003759 DOI: 10.1016/j.dental.2019.04.001
    OBJECTIVE: This study introduced the potential and proof-of-concept of high intensity focused ultrasound (HIFU) technology for dentin-surface treatment for resin-dentin bonding without acid-aided demineralization. This new strategy could provide a way to enhance interface-integrity and bond-durability by changing the nature of dentin-substrate; bonded-interface structure and properties; and minimizing denuded-collagen exposure.

    METHODS: The interaction between HIFU waves and dentin-surface in terms of structural, mechanical and chemical variations were investigated by SEM, TEM, AFM, nano-indentation and Raman-analysis. The bonding between HIFU-treated dentin and two-step, etch-and-rinse, adhesive was preliminary explored by characterizing dentin-bound proteases activities, resin-dentin interfacial morphology and bond-durability with HIFU exposure at different time-points of 60, 90 and 120 s compared to conventional acid-etching technique.

    RESULTS: With the increase in HIFU exposure-time from 60-to-120 s, HIFU waves were able to remove the smear-layer, expose dentinal-tubules and creating textured/rough dentin surface. In addition, dentin surfaces showed a pattern of interlocking ribbon-like minerals-coated collagen-fibrils protruding from the underlaying amorphous dentin-background with HIFU exposure for 90 s and 120 s. This characteristic pattern of dentin-surface showing inorganic-minerals associated/aligned with collagen-fibrils, with 90-to-120 s HIFU-treatment, was confirmed by the Raman-analysis. HIFU-treated specimens showed higher nano-indentation properties and lower concentrations of active MMP-2 and Cathepsin-K compared to the acid-etched specimens. The resin-dentin bonded interface revealed the partial/complete absence of the characteristic hybrid-layer formed with conventional etch-and-rinse bonding strategy. Additionally, resin-infiltration and resin-tags formation were enhanced with the increase in HIFU exposure-time to 120 s. Although, all groups showed significant decrease in bond-strength after 12 months compared to 24 h storage in artificial saliva, groups exposed to HIFU for 90 s and 120 s showed significantly higher μTBS compared to the control acid-etched group.

    SIGNIFICANCE: The implementation of HIFU-technology for dental hard-tissues treatment could be of potential significance in adhesive/restorative dentistry owing to its ability of controlled, selective and localised combined tissue alteration/ablation effects.

  3. Daood U, Akram Z, Matinlinna JP, Fawzy AS
    Dent Mater, 2019 07;35(7):1017-1030.
    PMID: 31064669 DOI: 10.1016/j.dental.2019.04.005
    OBJECTIVE: The aim of this study was to investigate EDC-assisted collagen crosslinking effect with different concentrations of tiopronin-protected gold (TPAu) nanoparticles on demineralized dentine.

    METHODS: TPAu nanoparticles were fabricated from 0.31-g tetrachloroauric acid and 0.38-g of N-(2-mercaptopropionyl) glycine (2.4-mmol). Then co-dissolved using 35-mL of 6:1 methanol/acetic acid and mixed using NaBH4. EDC (0.3-M) was conjugated to TPAu nanoparticles at TPAU/EDC-0.25:1, and TPAU/EDC-0.5:1 treatment formulations ratios. Dentin specimens treated with 0.3-M EDC solution alone or left untreated were used as control. Nanoparticles formulations were characterized in term of particles morphology and size, Zeta potential, thermogravimetric analysis and small-angle X-ray scattering. Dentin substrates were characterized in term of TEM investigation, dentin proteases characterization, hydroxyproline liberation, elastic modulus measurement, Raman analysis and confocal microscopy viewing.

    RESULTS: TEM evaluation of tiopronin protected gold nanoparticles dispersion revealed nano-clusters formations in both groups. However, based on our TEM measurements, the particle-size was ranging from ˜20 to 50 nm with spherical core-shape which were almost similar for both TPAu/EDC ratios (0.5:1 and 0.25:1). Zeta potential measurements indicate negative nanoparticles surface charge. SAXS profiles for both formulations, suggest a typical profile for uni-lamellar nanoparticles. Superior dentin collagen cross-linking effect was found with the TPAu/EDC nanoparticles formulations compared to the control and EDC treated groups.

    SIGNIFICANCE: Cross-linking of dentin collagen using TPAu coupled with EDC through TPAu/EDC nanoparticles formulations is of potential significance in improving the biodegradation resistance, proteases inhibition, mechanical and structural stability of demineralized dentin substrates. In addition, the cross-linking effect is dependent on TPAu/EDC ratio, whereas higher cross-linking effect was found at TPAu/EDC ratio of 0.5:1.

  4. Mustafa AA, Matinlinna JP, Saidin S, Kadir MR
    J Prosthet Dent, 2014 Dec;112(6):1498-506.
    PMID: 24993375 DOI: 10.1016/j.prosdent.2014.05.011
    STATEMENT OF PROBLEM: The inconsistency of dentin bonding affects retention and microleakage.

    PURPOSE: The purpose of this laboratory and finite element analysis study was to investigate the effects on the formation of a hybrid layer of an experimental silane coupling agent containing primer solutions composed of different percentages of hydroxyethyl methacrylate.

    MATERIAL AND METHODS: A total of 125 sound human premolars were restored in vitro. Simple class I cavities were formed on each tooth, followed by the application of different compositions of experimental silane primers (0%, 5%, 25%, and 50% of hydroxyethyl methacrylate), bonding agents, and dental composite resins. Bond strength tests and scanning electron microscopy analyses were performed. The laboratory experimental results were validated with finite element analysis to determine the pattern of stress distribution. Simulations were conducted by placing the restorative composite resin in a premolar tooth by imitating simple class I cavities. The laboratory and finite element analysis data were significantly different from each other, as determined by 1-way ANOVA. A post hoc analysis was conducted on the bond strength data to further clarify the effects of silane primers.

    RESULTS: The strongest bond of hybrid layer (16.96 MPa) was found in the primer with 25% hydroxyethyl methacrylate, suggesting a barely visible hybrid layer barrier. The control specimens without the application of the primer and the primer specimens with no hydroxyethyl methacrylate exhibited the lowest strength values (8.30 MPa and 11.78 MPa) with intermittent and low visibility of the hybrid layer. These results were supported by finite element analysis that suggested an evenly distributed stress on the model with 25% hydroxyethyl methacrylate.

    CONCLUSIONS: Different compositions of experimental silane primers affected the formation of the hybrid layer and its resulting bond strength.

  5. Mustafa AA, Matinlinna JP, Razak AA, Hussin AS
    J Investig Clin Dent, 2015 Aug;6(3):161-9.
    PMID: 24415731 DOI: 10.1111/jicd.12083
    AIM: To evaluate in vitro the effect of different concentrations of 2-hydroxyethyl methacrylate (HEMA) in experimental silane-based primers on shear bond strength of orthodontic adhesives.

    METHODS: Different volume percentages of HEMA were tested in four experimental silane-based primer solutions (additions of HEMA: 0, 5.0 vol%, 25.0 vol% and 50.0 vol%). An experimental silane blend (primer) of 1.0 vol% 3-isocyanatopropyltrimethoxysilane (ICMS) + 0.5% bis-1,2-(triethoxysilyl) ethane (BTSE) was prepared and used. The experimental primers together with the control group were applied onto acid-etched premolars for attachment of orthodontic brackets. After artificial aging by thermocycling the shear-bond strength was measured. The fractured surfaces of all specimens were examined under scanning electron microscopy (SEM) to evaluate the failure mode on the enamel surface.

    RESULTS: The experimental primers showed the highest shear-bond strength of 21.15 MPa (SD ± 2.70 MPa) and with 25 vol% showed a highly significant increase (P < 0.05) in bond strength. The SEM images showed full penetration of adhesive agents when using silane-based primers. In addition, the SEM images suggested that the predominant failure type was not necessarily the same as for the failure propagation.

    CONCLUSIONS: This preliminary study suggested that nonacidic silane-based primers with HEMA addition might be an alternative to for use as adhesion promoting primers.

  6. Mustafa A, Lung CY, Mustafa NS, Mustafa BA, Kashmoola MA, Zwahlen RA, et al.
    Clin Oral Implants Res, 2016 Mar;27(3):303-9.
    PMID: 25393376 DOI: 10.1111/clr.12525
    OBJECTIVES: To investigate the effect of eicosapentaenoic acid (EPA)-coated Ti implants on osteoconduction in white New Zealand rabbit mandibles.

    MATERIAL AND METHODS: Sandblasted and cleansed planar titanium specimens with a size of 5 × 5 × 1 mm were coated on one side with 0.25 vol% eicosapentaenoic acid (EPA). The other side of the specimens was kept highly polished (the control side). These specimens were inserted in rabbit mandibles. Twelve rabbits were randomly assigned into three study groups (n = 4). The rabbits were sacrificed at 4, 8, and 12 weeks. The harvested specimens with the implants were assessed for new bone formation on both sides of the implant using CBCT, conventional radiographs, and the biaxial pullout test. The results were statistically analyzed by a nonparametric Kruskal-Wallis test and Friedman's test as multiple comparisons and by Brunner-Langer nonparametric mixed model approach (R Software).

    RESULTS: A significant osteoconductive bone formation was found on the EPA-coated Ti implant surface (P < 0.05) at 8 weeks when compared to the polished surface (control). Biaxial pullout test results showed a significant difference (P < 0.05) after 8 and 12 weeks with a maximum force of 243.8 N, compared to 143.25 N after 4 week.

    CONCLUSION: EPA implant coating promoted osteoconduction on the Ti implant surfaces, enhancing the anchorage of the implant to the surrounding bone in white New Zealand rabbits.

  7. Daood U, Tsoi JKH, Neelakantan P, Matinlinna JP, Omar HAK, Al-Nabulsi M, et al.
    Dent Mater, 2018 08;34(8):1175-1187.
    PMID: 29779627 DOI: 10.1016/j.dental.2018.05.005
    OBJECTIVE: Collagen fibrils aid in anchoring resin composite restorations to the dentine substrate. The aim of the study was to investigate effect of non-enzymatic glycation on bond strength and durability of demineralized dentine specimens in a modified two-step etch-and-rinse dentine adhesive.

    METHODS: Dentine surfaces were etched with 37% phosphoric acid, bonded with respective in vitro ethanol and acetone adhesives modified with (m/m, 0, 1%, 2% and 3% ribose), restored with restorative composite-resin, and sectioned into resin-dentine slabs and beams to be stored for 24h or 12 months in artificial saliva. Bond-strength testing was performed with bond failure analysis. Pentosidine assay was performed on demineralized ribose modified dentine specimens with HPLC sensitive fluorescent detection. The structural variations of ribose-modified dentine were analysed using TEM and human dental pulpal cells were used for cell viability. Three-point bending test of ribose-modified dentine beams were performed and depth of penetration of adhesives evaluated with micro-Raman spectroscopy. The MMP-2 and cathepsin K activities in ribose-treated dentine powder were also quantified using ELISA. Bond strength data was expressed using two-way ANOVA followed by Tukey's test. Paired T tests were used to analyse the specimens for pentosidine crosslinks. The modulus of elasticity and dentinal MMP-2 and cathepsin K concentrations was separately analyzed using one-way ANOVA.

    RESULTS: The incorporation of RB in the experimental two-step etch-and-rinse adhesive at 1% improved the adhesive bond strength without adversely affecting the degree of polymerisation. The newly developed adhesive increases the resistance of dentine collagen to degradation by inhibiting endogenous matrix metalloproteinases and cysteine cathepsins. The application of RB to acid-etched dentine helps maintain the mechanical properties.

    SIGNIFICANCE: The incorporation of 1%RB can be considered as a potential candidate stabilizing resin dentine bond.

  8. Neelakantan P, Ahmed HMA, Wong MCM, Matinlinna JP, Cheung GSP
    Int Endod J, 2018 Aug;51(8):847-861.
    PMID: 29377170 DOI: 10.1111/iej.12898
    The aim of this systematic review was to address the question: Do different irrigating protocols have an impact on the dislocation resistance of mineral trioxide aggregate (MTA)-based materials? The review was performed using a well-defined search strategy in three databases (PubMed, Scopus, Web of Science) to include laboratory studies performed between January 1995 and May 2017, in accordance with PRISMA guidelines. Two reviewers analysed the papers, assessed the risk of bias and extracted data on teeth used, sample size, size of root canal preparation, type of MTA-based material, irrigants, canal filling method, storage method and duration, region of roots and the parameters of push-out testing (slice thickness, plunger dimensions and plunger loading direction), the main results and dislocation resistance values (in MPa). From 255 studies, 27 were included for full-text analysis. Eight papers that met the inclusion criteria were included in this review. There was a wide variation in dislocation resistance due to differences in irrigation sequence, time and concentration of irrigants, storage method and duration, and the parameters of push-out bond strength testing. A meta-analysis was not done but qualitative synthesis of the included studies was performed. No definitive conclusion could be drawn to evaluate the effect of irrigation protocols on dislocation resistance of MTA-based materials. Recommendations have been provided for standardized testing methods and reporting of future studies, so as to obtain clinically relevant information and to understand the effects of irrigating protocols on root canal sealers and their interactions with the dentine walls of root canals.
  9. Daood U, Parolia A, Elkezza A, Yiu CK, Abbott P, Matinlinna JP, et al.
    Dent Mater, 2019 09;35(9):1264-1278.
    PMID: 31201019 DOI: 10.1016/j.dental.2019.05.020
    OBJECTIVE: To analyze effect of NaOCl+2% quaternary ammonium silane (QAS)-containing novel irrigant against bacteria impregnated inside the root canal system, and to evaluate its antimicrobial and mechanical potential of dentine substrate.

    METHODS: Root canal was prepared using stainless steel K-files™ and ProTaper™ and subjected to manual and ultrasonic irrigation using 6% NaOCl+2% CHX, 6% NaOCl+2% QAS and saline as control. For confocal-microscopy, Raman spectroscopy and SEM analysis before and after treatment, Enterococcus faecalis cultured for 7 days. Raman spectroscopy analysis was done across cut section of gutta percha/sealer-dentine to detect resin infiltration. Indentation of mechanical properties was evaluated using a Berkovich indenter. The contact angle of irrigants and surface free energy were evaluated. Mineralization nodules were detected through Alazarin red after 14 days.

    RESULTS: Control biofilms showed dense green colonies. Majority of E. faecalis bacteria were present in biofilm fluoresced red in NaOCl+2% QAS group. There was reduction of 484cm-1 Raman band and its intensity reached lowest with NaOCl+2% QAS. There was an increase in 1350-1420cm-1 intensity in the NaOCl+2% CHX groups. Gradual decrease in 1639cm-1 and 1609cm-1 Raman signal ratios were seen in the resin-depth region of 17μm>, 14.1μm> and 13.2μm for NaOCl+2% QAS, NaOCl+2% CHX and control groups respectively. All obturated groups showed an intact sealer/dentine interface with a few notable differences. 0.771 and 83.5% creep indentation distance for NaOCl+2% QAS ultrasonic groups were observed. Highest proportion of polar component was significantly found in the NaOCl+2% QAS groups which was significantly higher as compared to other groups. Mineralized nodules were increased in NaOCl+2% QAS.

    SIGNIFICANCE: Favorable antimicrobial and endodontic profile of the NaOCl+2% QAS solution might suggest clinical use for it for more predictable reduction of intracanal bacteria.

  10. Daood U, Matinlinna JP, Pichika MR, Mak KK, Nagendrababu V, Fawzy AS
    Sci Rep, 2020 07 03;10(1):10970.
    PMID: 32620785 DOI: 10.1038/s41598-020-67616-z
    To study the antimicrobial effects of quaternary ammonium silane (QAS) exposure on Streptococcus mutans and Lactobacillus acidophilus bacterial biofilms at different concentrations. Streptococcus mutans and Lactobacillus acidophilus biofilms were cultured on dentine disks, and incubated for bacterial adhesion for 3-days. Disks were treated with disinfectant (experimental QAS or control) and returned to culture for four days. Small-molecule drug discovery-suite was used to analyze QAS/Sortase-A active site. Cleavage of a synthetic fluorescent peptide substrate, was used to analyze inhibition of Sortase-A. Raman spectroscopy was performed and biofilms stained for confocal laser scanning microscopy (CLSM). Dentine disks that contained treated dual-species biofilms were examined using scanning electron microscopy (SEM). Analysis of DAPI within biofilms was performed using CLSM. Fatty acids in bacterial membranes were assessed with succinic-dehydrogenase assay along with time-kill assay. Sortase-A protein underwent conformational change due to QAS molecule during simulation, showing fluctuating alpha and beta strands. Spectroscopy revealed low carbohydrate intensities in 1% and 2% QAS. SEM images demonstrated absence of bacterial colonies after treatment. DAPI staining decreased with 1% QAS (p 
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