Alaa Sabrah

Full-contour yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations have started to be advocated in clinical situations where occlusal/palatal space is limited or to withstand parafunctional activities. Objectives: To investigate the effects of different polishing techniques on the surface roughness of Y-TZP (Ardent Dental, Inc) and on the wear behavior of synthetic hydroxyapatite (HA) utilized herein as a substitute for human enamel. Methods: Thirty-two Y-TZP sliders (ϕ=2mm×1.5mm in height) were manufactured using CAD/CAM and embedded in acrylic resin using brass holders. Samples were then randomly allocated into four groups (n=8) according to the finishing/polishing procedure: G1-as-machined, G2-glazed, G3-diamond bur finishing (Brasseler, USA) and G4-G3+OptraFine® polishing kit (Ivoclar-Vivadent). Thirty-two sintered HA disks (ϕ=11mm×2.9mm in height) were mounted in brass holders as previously described. Baseline surface roughness (Ra and Rq, in µm) were recorded...

The presence of microorganisms and derivative toxins in the infected root canals determine the changes that occur in the apical periodontium. The aim in this in vitro study has been to evaluate the antimicrobial activity of the intracanal medicaments against bacterial isolates in cases with acute periapical periodontitis. The following clinical isolates from cases with acute periodontitis (nonexudative form) were used in the present study: Streptococcus pyogenes, Streptococcus mitis, Streptococcus bovis, Streptococcus anginosus, Enterococcus faecalis, Staphylococcus aureus. We tested their sensitivity to some of the most frequently used intracanal medicaments (in vitro), i.e.: Calcium hydroxide paste (Calcident 450® W/P Dental, Germany), Sodium hypochlorite 3% (Switzerland), Metronidazole 0.5% (Troya Pharm, Bulgaria), Chlorhexidine gluconate 0.1% (Troya Pharm, Bulgaria), and a combination of Sodium hypochlorite 3% and Metronidazole 0.5%. The results show that Calcium hydroxide had t...

The aim of this study was to investigate the residual antibacterial effect of human radicular dentin treated with various concentrations of triple antibiotic paste and double antibiotic paste (DAP). Sterilized dentin specimens were randomly assigned to 6 treatment groups and a no-treatment control group (n = 45 per group). For treatment groups, specimens were treated with either TAP or DAP at various concentrations (1000, 1, or 0.5 mg/mL) for 2 weeks. Then, each specimen was irrigated with 5 mL saline and incubated in phosphate-buffered solutions for 3, 7, 14, or 30 days. After that, Enterococcus faecalis was cultured on the specimens for 3 days. Each specimen was then transferred to a tube containing 200 μL saline, sonicated, and vortexed to detach the bacterial biofilm. The detached biofilm was spiral plated, and the number of colony-forming units was determined using an automated counting machine. Dentin specimens treated with 1000 mg/mL TAP or DAP had a significant residual anti...

ABSTRACT This study compared the traditional radiotracer method (Rt) for determination of dentifrice abrasivity to the recently introduced surface profile (Sp) method (ISO 11609). Specimens from human root dentin were prepared for each method and randomly assigned to 8 dentifrice/abrasive groups (n=8), of wide abrasivity range. Aqueous dentifrice slurries or abrasive suspensions were used to brush specimens in a toothbrushing machine. Two independent studies (Rt, Sp) were carried out. For Rt, the specimen preparation, study design, analysis and calculation of the dentifrice abrasive level (RDA) followed the ISO 11609/Annex-A guidelines. Similarly for Sp, the ISO 11609/Annex-B recommendations were followed, except by the number of brushing strokes, which was pre-determined to be 2000 strokes. RDA data were analyzed using ANOVA and Tukey tests (α=0.05). The correlation between methods was also investigated. Overall, higher variation and RDA values were observed for Sp compared to Rt. While good correlation was found between methods (R2=0.841), group ranking was dissimilar and better statistical differentiation among groups was observed in Rt. The Rt method showed to be a more standardized and robust method compared to Sp for the determination of RDA values of dentifrices/abrasives. Sp needs further development before being considered as an equivalent method to Rt. Keywords Dentifrice; Abrasivity; Dentin; Radiation; Profilometry

The purpose of this study was to evaluate the influence of full-contour (Y-TZP) zirconia surface roughness (glazed vs. as-machined) on the wear behavior of glass-ceramics. Thirty-two full contour Y-TZP (Diazir®) specimens (hereafter referred to as zirconia sliders) (ϕ = 2 mm, 1.5 mm in height) were fabricated using CAD/CAM and sintered according to the manufacturer's instructions. Zirconia sliders were embedded in brass holders using acrylic resin and then randomly assigned (n = 16) according to the surface treatment received, that is, as-machined or glazed. Glass-ceramic antagonists, Empress/EMP and e.max/EX, were cut into tabs (13 × 13 × 2 mm(3) ), wet-finished, and similarly embedded in brass holders. Two-body pin-on-disk wear testing was performed at 1.2 Hz for 25,000 cycles under a 3 kg load. Noncontact profilometry was used to measure antagonist height (μm) and volume loss (mm(3) ). Qualitative data of the zirconia testing surfaces and wear tracks were obtained using SEM. Statistics were performed using ANOVA with a significance level of 0.05. As-machined yielded significantly higher mean roughness values (Ra = 0.83 μm, Rq = 1.09 μm) than glazed zirconia (Ra = 0.53 μm, Rq = 0.78 μm). Regarding glass-ceramic antagonist loss, as-machined zirconia caused significantly less mean height and volume loss (68.4 μm, 7.6 mm(3) ) for EMP than the glazed group (84.9 μm, 9.9 mm(3) ), while no significant differences were found for EX. Moreover, EMP showed significantly lower mean height and volume loss than EX (p < 0.0001). SEM revealed differences on wear characteristics between the glass-ceramics tested. e.max wear was not affected by zirconia surface roughness; however, Empress wear was greater when opposing glazed zirconia. Overall, surface glazing on full-contour zirconia did not minimize glass-ceramic wear when compared with as-machined zirconia.

To investigate the effects of polishing techniques on the surface roughness of Y-TZP ceramic and on the wear behavior of synthetic hydroxyapatite (HA). Thirty-two full-contour Y-TZP (Diazir(®)) sliders (φ=2 mm × 1.5 mm in height) were manufactured using CAD/CAM, embedded in acrylic resin using brass holders, and randomly allocated into four groups (n=8): according to the finishing/polishing procedure: G1-as-machined, G2-glazed, G3-diamond bur finishing and G4-G3+OptraFine(®) polishing kit. Thirty-two sintered HA disks (φ=13 mm × 2.9 mm in height) were similarly mounted in brass holders. Y-TZP sliders baseline surface roughness values (Ra and Rq, in μm) were recorded using a non-contact profilometer (Proscan 2000). A two-body pin-on-disc wear test was performed. HA height (μm) and volume (mm(3)) losses were measured. Y-TZP height loss was measured using a digital micrometer. One-way ANOVA was used to determine the effect of the polishing techniques on the surface roughness. Comparisons between groups for differences in antagonist height loss/volume, and slider height loss were performed using one-way ANOVA. Statistical significance was set at α=0.05. Roughness measurements showed significant differences (p=0.0001) among the surface treatments with G1 (Ra=0.84, Rq=1.13 μm) and G3 (Ra=0.89, Rq=1.2 μm) being the roughest, and G2 (Ra=0.42, Rq=0.63 μm) the smoothest (p=0.0001). Y-TZP slider height loss was highest for the glazed group (35.39 μm), and was lowest for the polished group (6.61 μm) (p=0.0001). Antagonist volume and height losses for groups (G1-G3) were similar, while the polished group (1.3 mm(3), 14.7 μm) showed significant lower values (p=0.0001). Although glazed zirconia provides an initially smooth surface, significantly increased antagonist wear was observed compared to the polished Y-TZP zirconia surface.