Comparative Numerical Analyses of Tooth Restored with Hydroxyapatite Ceramic Insert Versus Traditional Composite Restoration

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Composite scaffolds based on magnesium doped hydroxyapatite and mesoporous nanosized bioactive glass

Bioceramic materials based on hydroxyapatite (HAP) are widely used as scaffolding material for bone tissue engineering due to their similarity with inorganic part of human bones. Magnesium ion as a dopant in hydroxyapatite was previously shown to improve mechanical properties of HAP based materials, as well as to improve osteoblasts cell proliferation, and induce angiogenesis which stimulate the bone regeneration. Mesoporous bioactive glass nanoparticles (MBGNPs) present the latest generation of the sol-gel glasses, having high surface area and large pore volume that allow the loading of drugs (antiinflammatory, anti-osteoporotic, anti-cancer etc.) and growth factors for stimulating cell differentiation and proliferation. MBGNPs are highly soluble and more bioactive compared to the hydroxyapatite. However, their high porosity leads to poor mechanical properties of pure MBGNP-based scaffolds. Here we propose composite scaffolds based on magnesium doped hydroxyapatite and MBGNPs obtained by a modified microemulsion-assisted sol-gel synthesis for bone tissue engineering application. Hydrothermally obtained hydroxyapatite doped with 5 mol. % of magnesium ions was calcinated at 1000 °C and mixed with 10-20 wt.% BGNPs to form composite scaffolds by sponge replica method. The addition of MBGNPs has the influence on the sinterability, mechanical properties and bioactivity of the scaffolds

Physically Crosslinked Poly(methacrylic acid)/Gelatin Hydrogels with Excellent Fatigue Resistance and Shape Memory Properties

Hydrogels endure various dynamic stresses, demanding robust mechanical properties. Despite significant advancements, matching hydrogels’ strength to biological tissues and plastics is often challenging without applying potentially harmful crosslinkers. Using hydrogen bonds as sacrificial bonds offers a promising strategy to produce tough, versatile hydrogels for biomedical and industrial applications. Poly(methacrylic acid) (PMA)/gelatin hydrogels were synthesized by thermally induced free-radical polymerization and crosslinked only by physical bonds, without adding any chemical crosslinker. The addition of gelatin increased the formation of hydrophobic domains in the structure of the hydrogels, which acted as permanent crosslinking points. The increase in PMA and gelatin contents generally led to a lower equilibrium water content (WC), higher thermal stability and better mechanical properties. The values of tensile strength and toughness reached up to 1.44 ± 0.17 MPa and 4.91 ± 0.51 MJ m−3, respectively, while the compressive modulus and strength reached up to 0.75 ± 0.06 MPa and 24.81 ± 5.85 MPa, respectively, with the WC being higher than 50 wt.%. The obtained values for compressive mechanical properties are comparable with super-strong hydrogels reported in the literature. In addition, hydrogels exhibited excellent fatigue resistance and biocompatibility, as well as great shape memory properties, which make them prominent candidates for a wide range of biomedical applications

Examination of antimicrobial potential in natural isolates of lactobacillus casei/paracasei group

Cilj ove studije je izučavanje antimikrobnog potencijala 52 prirodna izolata vrste L. casei/paracasei. Učestalost gena koji kodiraju BacSJ (bacSJ2-8/bacSJ2-8i genski klaster), acidocin 8912 (acdT), ABC-transporter (abcT) i pomoćni protein (acc) su takođe izučavani. Genski klaster bacSJ2-8/bacSJ2-8i prisutan je kod 49 (94.23%), a acdT kod 41 (78.85%) od 52 testirana soja. Četrdeset sojeva (76.92%) poseduje oba analizirana gena. Interesantno je da samo 17 sojeva (32.69%) koji poseduju bacSJ2-8/bacSJ2-8i genski klaster i/ili acdT gen proizvode bakteriocine. Soj L. paracasei BGNK1-62 poseduje bacSJ2-8/bacSJ2-8i genski klaster, ali ne proizvodi bakteriocin BacSJ što je verovatno posledica nedostatka abcT i acc gena. Nakon transformacije soja BGNK1-62 konstruktom pA2A koji poseduje abcT i acc gene ostvarena je proizvodnja bakteriocina BacSJ. Osim toga, utvrđeno je da soj L. paracasei BGGR2-66 proizvodi nov bakteriocin označen kao BacGR, koji je biohemijski okarakterisan, a određena je i njegova N-terminalna sekvenca.The aim of this study was to investigate the antimicrobial potential of 52 natural isolates of Lactobacillus casei/paracasei. The incidence of relevant genes encoding BacSJ (bacSJ2-8/bacSJ2-8i gene cluster), acidocin 8912 (acdT), ABC-transporter (abcT) and accessory protein (acc) was also studied. These genes were found to be widespread amongst the analyzed L. casei/paracasei strains. The bacSJ2-8/bacSJ2-8i gene cluster was present in 49 (94.23%) and acdT in 41 (78.85%) of the 52 tested strains. Forty of these strains (76.92%) harbored both analyzed genes. Interestingly, only 17 strains (32.69%) with the bacSJ2-8/bacSJ2-8i gene cluster and/or the acdT gene showed bacteriocin production. Strain L. paracasei BGNK1-62 contained the bacSJ2-8/bacSJ2-8i gene cluster, but did not produce bacteriocin BacSJ possibly due to absence of the abcT and acc genes. Hence, these genes were introduced into BGNK1-62 by transformation with constructed plasmid pA2A, after which BacSJ was produced. In addition, it was found that L. paracasei BGGR2-66 produced new bacteriocin designated as BacGR that was biochemically characterized and its N- terminal sequence was determined

Optical properties of composite restorations influenced by dissimilar dentin restoratives

Objectives. To evaluate optical properties (color and translucency) of 'sandwich' restorations of resin-based composites and esthetically unfavorable dentin restoratives. Methods. Cylindrical 'dentin' specimens (8 mm in diameter and 2 mm thick, N = 5/group) were prepared using EverX Posterior (GC), Biodentine (Septodont), experimental hydroxyapatite (HAP) or conventional composites (Gradia Direct Posterior, GC; Filtek Z250 and Filtek Z500, 3M ESPE). Capping 'enamel' layers were prepared using composites (Gradia Direct Posterior, Filtek Z250 or Z550) of Al or A3 shade and the following thickness: 0.6, 1 or 2 mm. Color (Delta E) and translucency parameter (TP) were determined using a spectrophotometer (VITA Easyshade Advance 4.0, VITA Zahnfabrik). Data were statistically analyzed using analysis of variance with Tukey's post-hoc tests (alpha = 0.05). Results. TP was greatly affected by layer thickness, whilst Delta E depended on shade and layer thickness of the capping composite. HAP and Biodentine showed significantly lower TP and higher Delta E (deviation from 'ideal white') than composites (p lt 0.05). Greater TP was seen in EverX_composite groups than in corresponding control groups of the same shade and thickness. TP of composites combined with Biodentine or HAP was below 2, lower than the corresponding control groups (p lt 0.05). Within-group differences of Delta E were greatest in HAP_composite groups. EverX_Gradia and EverX_FiltekZ250 combinations showed the most comparable Delta E with the control groups. Significance. A 2 mm thick layer of composite covering dentin restoratives with unfavorable esthetics is recommended for a final 'sandwich' restoration that is esthetically comparable to a conventional, mono-composite control restoration