Comparison Between Radiotracer and Surface Profile Methods for the Determination of Dentifrice

poster abstractIntroduction: ISO11609 states that a surface profile (Sp) method can be used to determine dentifrice abrasivity in relation to dentin (RDA) as an alternative to the traditional radiotracer method (Rt). A comparison between both methods was performed in this study. Methods: Specimens from human root dentin were prepared for each method and randomly assigned to 8 dentifrice/abrasive groups (n=8), which represented a wide abrasivity range. Aqueous dentifrice slurries or abrasive suspensions in a solution containing 0.5% carboxymethylcellulose and 10% glycerin were used to brush specimens in a custom-made V-8 cross-brushing machine. Two independent studies (Sp, Rt) were carried out. For Rt, the specimen preparation, study design, analysis and calculation of the abrasive level (RDA) followed the ISO11609/Annex A guidelines. Similarly for Sp, the ISO11609/Annex B recommendations were followed, except by the number of brushing strokes, which was pre-determined to be 2000 strokes (instead of 10000) in a preliminary test. Data were analyzed using ANOVA and Tukey tests, with significance level set at 5%. The correlation between methods was also investigated. Results: Overall, higher variation and RDA values were observed for the Sp method 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. Conclusions: 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 to be further developed before being considered as an equivalent test method for RDA. The determination of the abrasive levels of toothpastes using standard testing methods is important to guide oral care professionals and patients on the prevention of toothbrushing abrasive wear

Effect of different endodontic regeneration protocols on wettability, roughness and chemical composition of surface dentin

Introduction We investigated the changes in physiochemical properties of dentin surfaces after performing different endodontic regeneration protocols. Methods Human dentin slices were randomized into 4 treatment groups and 1 untreated control group (n = 10). One treatment group was irrigated with sodium hypochlorite (NaOCl) for 5 minutes followed by EDTA for 10 minutes. The other 3 treatment groups were irrigated with NaOCl; treated for 4 weeks with triple antibiotic paste (TAP), diluted triple antibiotic paste (DTAP), or calcium hydroxide (Ca[OH]2); and then irrigated with EDTA. After treatment, contact angles between a blood analog and dentin surfaces were evaluated. Surface roughness and chemical composition were characterized using optical profilometry and energy-dispersive X-ray spectroscopy, respectively. One-way analysis of variance followed by Fisher least significant difference tests were used for statistical analyses. Results All treatment groups showed a significant reduction in wettability and a significant increase in surface roughness when compared with untreated dentin. Dentin treated with Ca(OH)2 had significantly lower wettability compared with all other groups. No significant difference in wettability was found between dentin treated with DTAP and TAP protocols. Dentin treated with TAP had significantly higher surface roughness compared with all other groups. Untreated dentin and NaOCl + EDTA–treated dentin had significantly higher calcium and phosphorus as well as significantly lower carbon compared with dentin treated with Ca(OH)2, DTAP, and TAP. Conclusions Endodontic regeneration protocols had a significant effect on wettability, surface roughness, and chemical composition of surface dentin. The Ca(OH)2 protocol caused a significant reduction in dentin wettability compared with TAP or DTAP protocols

Color stability, Roughness, and Microhardness of Enamel and Composites Submitted to Staining/Bleaching Cycles

Objective: To compare the effect of two bleaching systems (bleaching gel and whitening strips) on the color change, roughness, and microhardness of enamel and two resin composites. Material and methods: Two cavities were prepared on bovine enamel specimens (n = 16) and restored with two composites: a nano-hybrid [Herculite Ultra (HU)] and a micro-hybrid composite [TPH Spectra (TS)]. Baseline color (CIE L*a*b*), roughness (μm), and microhardness (kgf/mm2) were measured using a spectrophotometer, optical profilometer, and Vickers microhardness (VHN) tester, respectively. The specimens were stained with coffee for 14 days, and randomized into two bleaching groups: gel and strips (n = 8), then submitted to a 10-day bleaching/staining test. Color, roughness, and microhardness were re-measured. The outcomes were analyzed using two-way ANOVA and Fisher's-PLSD test (α = 0.05). Results: Gel significantly improved the color (ΔE 4.9-8.3) and increased the roughness (Ra 0.04-0.08 μm) of all substrates (p < 0.0001) compared to strips. Enamel color was significantly improved (ΔE 5.4-8.3) compared to that of HU (ΔE 2.6-4.9) and TS (ΔE 2.0-4.9) with either gels or strips. TS roughness (0.03-0.08 μm) was significantly higher than that of enamel (0.01-0.05 μm) and HU (0.02-0.04 μm). Enamel had significantly reduced microhardness compared to HU (p = 0.0144). Conclusion: Gels produced the greatest color improvement and roughness compared to strips. Enamel had significant color improvement but had the greatest decrease in microhardness. Clinical significance: There was unacceptable color change between enamel and the composites after the combined cyclic effects of staining and bleaching

3D-Image Analysis of the Impact of Toothpaste Abrasivity on the Progression of Simulated Non-Carious Cervical Lesions

Objectives To investigate the effect of toothpaste abrasive level on the progression of non-carious cervical lesions (NCCLs) using 3D-image subtraction. Methods Upper first premolars were allocated into seven groups (n = 16) of toothpaste/abrasive slurries: A-Zeodent113/5%, B-Zeodent124/10%, C-Zeodent103/15%, D-Sensodyne Pronamel, E-Crest Cavity-Protection, F-Crest Pro-Health-Whitening, and G-Deionized water (DIW). Teeth were mounted on acrylic blocks, and their root surfaces covered with acrylic resin, except for 2-mm near the cemento-enamel junction that was exposed to toothbrushing. Specimens were brushed with the slurries for 5000-, 15,000-, 35,000- and 65,000-strokes. Impressions were taken at baseline and after each brushing time, and then scanned by a 3D optical profilometer. Dentine volume loss was calculated by image subtraction software and subjected to mixed-model ANOVA and multiple comparison tests (α = 0.05). Results No significant differences among slurries were observed at 5000 and 15,000. At 35,000, F showed higher loss than all other groups except C, which did not differ from the others. At 65,000, F (4.19 ± 3.29 mm3) showed the highest loss, followed by C (2.33 ± 1.47 mm3), which differed from all the other groups except B (1.85 ± 0.91 mm3). Groups B, A (1.35 ± 0.65 mm3), D (1.17 ± 0.48 mm3), E (1.40 ± 0.68 mm3) and G (1.12 ± 0.73 mm3) did not differ from each other. Groups F and C showed significant increase of volume loss starting at 35,000, while B, A, D and E only at 65,000; no increase loss was observed for G. Conclusions 3D-image subtraction was able to quantify and differentiate tooth loss, but only at advanced stages. The progression of NCCLs was more evident and faster for highly abrasive slurries. Clinical significance Upon root dentin exposure, brushing with lower abrasive dentifrices is advisable to reduce the risk for NCCLs development

The Effect of Diluted Triple and Double Antibiotic Pastes on Dental Pulp Stem Cells and Established Enterococcus faecalis Biofilm

Objectives To investigate the effect of various dilutions of antibiotic medicaments used in endodontic regeneration on the survival of human dental pulp stem cells (DPSCs) and to determine their antibacterial effect against established Enterococcus faecalis biofilm. Materials and methods The cytotoxic and antibacterial effects of different triple (TAP) and double antibiotic paste (DAP) dilutions (0.125, 0.25, 0.5, 1, and 10 mg/ml) were tested against Enterococcus faecalis established biofilm and DPSC. Established bacterial biofilm were exposed to antibiotic dilutions for 3 days. Then, biofilms were collected, spiral plated, and the numbers of bacterial colony forming units (CFU/ml) were determined. For the cytotoxic effect, lactate dehydrogenase activity assays (LDH) and cell viability assays (WST-1) were used to measure the percentage of DPSC cytotoxicity after 3-day treatment with the same antibiotic dilutions. A general linear mixed model was used for statistical analyses (α = 0.05). Results All antibiotic dilutions significantly decreased the bacterial CFU/ml. For WST-1 assays, all antibiotic dilutions except 0.125 mg/ml significantly reduced the viability of DPSC. For LDH assays, the three lowest tested concentrations of DAP (0.5, 0.25, 0.125 mg/ml) and the two lowest concentrations of TAP (0.25 and 0.125 mg/ml) were non-toxic to DPSC. Conclusions All tested dilutions had an antibacterial effect against E. faecalis. However, 0.125 mg/ml of DAP and TAP showed a significant antibacterial effect with no cytotoxic effects on DPSCs. Clinical relevance Using appropriate antibiotic concentrations of intracanal medicament during endodontic regeneration procedures is critical to disinfect root canal and decrease the adverse effects on stem cells

Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

Objectives To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al2O3) particles at different pressures. Materials and Methods Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ2 tests (α = 0.05). Results The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used

The predictive value of high school grade point average to academic achievement and career satisfaction of dental graduates

Abstract Background In a country where admission to dental schools is based solely on the cognitive abilities of students, the aim of the study was to investigate the correlation between high school grade point average and graduating academic achievement for dental students; moreover, determine whether a correlation exists between dental students’ graduating academic achievement and their career choices and job satisfaction. Methods A five-year retrospective cohort study was conducted at the University of Jordan, involving (828) dental graduates first enrolled between 2010 and 2014. Correlations comparing high school grade point average and graduating academic achievement were done for the total sample composed of (736) students. A short survey was constructed to assess the career choices and job satisfaction for recently graduated dentists and correlate them with their graduating academic achievement. Results Statistically significant but weak positive correlation (0.3) was found between high school grade point average and graduating academic achievement for dental students (p ≤ 0.05). Statistically significant correlations were found between graduating academic achievement and career choices and job satisfaction. Conclusion The significant positive correlation between the high school grade point average and graduating academic achievement of our dental students indicate that our school admission system depending on high school grade point average is a valid system. There was a significant negative correlation between the graduating academic achievement and both the career choices and job satisfaction among fresh graduate dentists in Jordan. This information is required to update the dental school admissions procedures in response to the changing dental educational landscape

Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

OBJECTIVES To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al2O3) particles at different pressures. MATERIALS AND METHODS Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ2 tests (α = 0.05). RESULTS The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. CONCLUSIONS CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used