In vitro evaluation of modified surface microhardness measurement, focus variation 3D microscopy and contact stylus profilometry to assess enamel surface loss after erosive-abrasive challenges

The aim of the study was to compare surface loss values after erosion-abrasion cycles obtained with modified surface microhardness measurement (mSMH), focus variation 3D microscopy (FVM) and contact stylus profilometry (CSP). We cut human molars into buccal and lingual halves, embedded them in resin and ground 200 μm of enamel away. The resulting surfaces were polished. To maintain a reference area, we applied Block-Out resin to partly cover the enamel surface. The samples were incubated in artificial saliva (37°C; 1 h), then rinsed in deionized water (10 s) and dried with oil-free air (5 s). We immersed the specimens individually in 30 mL citric acid (1%, pH 3.6) for 2 min (25°C, 70 rpm dynamic conditions) before brushing them (50 strokes, 200 g) in an automatic brushing machine with toothpaste-slurry. We calculated the surface loss as per mSMH, by re-measuring the length of the same six indentations made before the abrasive challenge. The experiment consisted of five experimental groups that received between 2 and 10 erosion-abrasion cycles. Each group contained 15 specimens and samples in groups 1, 2, 3, 4 and 5 underwent a total of 2, 4, 6, 8 and 10 cycles, respectively. The resin was removed from the reference area in one piece under 10× magnification and the FVM and CSP were performed. Agreement between the methods was calculated with the intraclass correlation coefficient (ICC) and depicted in Bland-Altman plots. All methods presented a linear pattern of surface loss measurements throughout the experiment, leading overall to a strong, statistically significant correlation between the methods (ICC = 0.85; p<0.001). So, despite the different surface loss values, all methods presented consistent results for surface loss measurement

Effect of dentin powder on the antimicrobial properties of hyperpure chlorine-dioxide and its comparision to conventional endodontic disinfecting agents

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Comparing the efficacy of hyper-pure chlorine-dioxide with other oral antiseptics on oral pathogen microorganisms and biofilm in vitro.

This study examines the antibacterial properties of sodium hypochlorite (NaOCl), chlorhexidine gluconate (CHX), Listerine(R), and high purity chlorine dioxide (Solumium, ClO2) on selected common oral pathogen microorganisms and on dental biofilm in vitro. Antimicrobial activity of oral antiseptics was compared to the gold standard phenol. We investigated Streptococcus mutans, Lactobacillus acidophilus, Enterococcus faecalis, Veillonella alcalescens, Eikenella corrodens, Actinobacillus actinomycetemcomitans and Candida albicans as some important representatives of the oral pathogens. Furthermore, we collected dental plaque from the upper first molars of healthy young students. Massive biofilm was formed in vitro and its reduction was measured after treating it with mouthrinses: CHX, Listerine(R) or hyper pure ClO2. Their biofilm disrupting effect was measured after dissolving the crystal violet stain from biofilm by photometer. The results have showed that hyper pure ClO2 solution is more effective than other currently used disinfectants in case of aerobic bacteria and Candida yeast. In case of anaerobes its efficiency is similar to CHX solution. The biofilm dissolving effect of hyper pure ClO2 is significantly stronger compared to CHX and Listerine(R) after 5 min treatment. In conclusion, hyper pure ClO2 has a potent disinfectant efficacy on oral pathogenic microorganisms and a powerful biofilm dissolving effect compared to the current antiseptics, therefore high purity ClO2 may be a new promising preventive and therapeutic adjuvant in home oral care and in dental or oral surgery practice

EFFECTIVENESS OF A HIGH PURITY CHLORINE DIOXIDE SOLUTION IN ELIMINATING INTRACANAL ENTEROCOCCUS FAECALIS BIOFILM

We investigated the effectiveness of chlorine dioxide (ClO2) solution in comparison to sodium hypochlorite (NaOCl) and chlorhexidine gluconate (CHX) in the elimination of intracanal Enterococcus faecalis biofilm. Extracted human teeth were inoculated with E. faecalis. After preparation the canals were irrigated with ClO2, NaOCl, CHX or physiologic saline for control. Two and five days later bacterial samples were collected and streaked onto Columbia agar. CFU/mL were counted. The canal walls were investigated by scanning electron microscopy (SEM). The gas phase was investigated in an upside down Petri dish where E. faecalis was inoculated onto blood agar. The irrigants were placed on absorbent paper into the cover. Bacteria were detectable in the control group, but not in any of the irrigants groups. There was a massive reinfection 2 or 5 days after irrigation in the control group. The lowest reinfection was found after the ClO2 treatment. These findings were confirmed by SEM images. We observed an antibacterial effect of ClO2 and NaOCl gas phases on E. faecalis growth, but not of CHX. ClO2 eliminates intracanal biofilm and keeps canal nearly free from bacteria. We suggest the use of high purity ClO2 as a root canal irrigant in clinical practice

Enamel surface loss median values in percentage according to the different groups as measured using the three different methods.

<p>Enamel surface loss median values in percentage according to the different groups as measured using the three different methods.</p

Illustration of the FVM measurement.

<p>The figure represents a typical output of the FVM (constant field of view 110 μm x 144 μm). The different colors represent the different heights on the surface of the specimen (see scale on the right). For measurement, rectangular areas are selected on both the reference surface (yellow) and the eroded-abraded surface (magenta). The software calculates the average height of these two selected areas, from these we calculate the amount of enamel lost.</p

Bland-Altman plots assessing agreements between the different methods.

<p>“A” is the plot comparing FVM and mSMH, “B” stands for CSP versus mSMH and “C” compares CSP and FVM. Solid lines represent ordinary least square regression models (y = mx + c), where the slope (m) represents proportional bias when p < 0.05. Dotted lines represent the systematic differences, where relative bias is assumed when p < 0.05. The dotted and dashed lines represent 95% confidence intervals of the systematic difference (dotted) line. SL: surface loss.</p

Box plots representing enamel surface loss values as a function of cycle numbers.

<p>Enamel surface loss median and interquartile values in μm according to the different cycle numbers (groups) using the three different methods. Different lower-case letters (a, b, c) represent significant differences between different methods after the same number of cycles (p<0.05).</p