Antimicrobial efficacy of platinum-doped silver nanoparticles.

Silver nanoparticles (AgNPs) have been proposed to combat oral infection due to their efficient ionic silver (Ag+ ) release. However, concentrations required for antimicrobial efficacy may not be therapeutically viable. In this work, platinum-doped silver nanoparticles (Pt-AgNPs) were explored to evaluate their potential for enhanced Ag+ release, which could lead to enhanced antimicrobial efficacy against S. aureus, P. aeruginosa, and E. coli. AgNPs doped with 0.5, 1, and 2 mol% platinum (Pt0.5 -AgNPs, Pt1 -AgNPs, and Pt2 -AgNPs) were synthesized by a chemical reduction method. Transmission electron microscopy revealed mixed morphologies of spherical, oval, and ribbon-like nanostructures. Surface-enhanced Raman scattering revealed that the surface of Pt-AgNPs was covered with up to 93% Pt. The amount of Ag+ released increased 16.3-fold for Pt2 -AgNPs, compared to AgNPs. The initial lag phase in bacterial growth curve was prolonged for Pt-AgNPs. This is consistent with a Ag+ release profile that exhibited an initial burst followed by sustained release. Doping AgNPs with platinum significantly increased the antimicrobial efficacy against all species. Pt2 -AgNPs exhibited the lowest minimum inhibitory concentrations, followed by Pt1 -AgNPs, Pt0.5 -AgNPs, and AgNPs, respectively. Doping AgNPs with a small amount of platinum promoted the release of Ag+ , based on the sacrificial anodic effect, and subsequently enhanced their antimicrobial efficacy.

Effect of Surface Modification on In-Depth Transformations and Flexural Strength of Zirconia Ceramics.

PURPOSE: Chairside surface adjustments of zirconia dental restorations enhance the toughening stress-induced tetragonal-to-monoclinic phase transformation and domain reorientation by ferro-elastic domain switching (FDS), but also trigger subsurface damage, which could compromise long-term clinical performance. The purpose of this study was to assess the depth of phase transformation, associated FDS, and flexural strength of dental zirconia (BruxZir HT 2.0), after chairside surface treatments. MATERIALS AND METHODS: Square specimens were sectioned from CAD/CAM blocks and sintered according to manufacturer's recommendations (n = 30). They were left as-sintered (AS; control), air abraded with fine (AAF) or coarse (AAC) alumina particles, ground (G) or ground and polished (GP). Roughness was measured by profilometry. Crystalline phases were investigated by grazing incidence X-ray diffraction (GIXRD) (n = 3). GIXRD data were fit using semi-log regression protocols to assess transformation depth and extent of FDS. The mean biaxial flexural strength was measured according to ISO 6872. Subsurface damage was assessed from SEM images using a bonded polished interface configuration. Flaw distribution was assessed by Weibull analysis. Results were analyzed by Kruskal-Wallis with Tukey's adjustment for multiple comparisons (p < 0.05). RESULTS: Air-abraded and ground groups exhibited higher mean surface roughness than control. AAF group exhibited the highest flexural strength (1662.6 ± 202.6 MPa) with flaw size (5.9 ± 1.8 µm) smaller than transformation (14.5 ± 1.2 µm) or FDS depth (19.3 ± 1.1 µm), followed by GP group (1567.2 ± 209.7 MPa) with smallest FDS depth (9.3 ± 2.0 µm) and flaw size (2.6 ± 1.8 µm), but without m-phase. AAC group (1371.4 ± 147.6 MPa) had the largest flaw size (40.3 ± 20.3 µm), transformation depth (47.2 ± 3.0 µm) and FDS depth (41.2 ± 2.2 µm). G group (1357.0 ± 196.7 MPa) had the smallest transformation depth (8.6 ± 1.5 µm), and mean FDS depth (19.8 ± 3.7 µm) and flaw size (18.6 ± 3.1 µm). AAC and AAF exhibited the highest Weibull modulus (11.2 ± 0.4 and 9.8 ± 0.3 µm, respectively). CONCLUSIONS: Variations in mean biaxial flexural strength were explained by the balance between the depth of toughening mechanisms (phase transformation and FDS) and subsurface damage. AAF and GP groups were the most efficient surface adjustments in promoting the highest mean biaxial flexural strength.

Dental caries, cariogenic microorganisms and salivary properties of allergic rhinitis children.

OBJECTIVES: The aim of this study was to observe the caries activities of allergic rhinitis patients in relation to salivary properties, salivary levels of mutans streptococci (MS) and lactobacillus (LB), oral hygiene and dietary habits. METHODS: The study groups composed of 40 allergic rhinitis children and 40 healthy controls aged between 6 and 13 years old. Demographic data, oral hygiene practices and dietary habits were recorded by questionnaire. For permanent teeth, caries experience was expressed as DMFT (D=decayed; M=missing; F=filled; T=teeth) index. The dmft (d=decayed; m=missing; f=filling; t=teeth) index was used for caries prevalence in primary teeth. Unstimulated salivary flow rate, salivary buffering capacity, and salivary MS and LB were also determined in children with allergic rhinitis and controls. RESULTS: There were no significant differences in combined DMFT/dmft, salivary flow rate, buffer capacity of saliva, salivary LB levels, and sugary food consumption between cases and controls (p>0.05). However, higher salivary MS levels were observed in allergic rhinitis patients, compared to controls (P<0.05). CONCLUSIONS: Our results demonstrated that patients with allergic rhinitis had an increase in the level of salivary MS.