A rapid nondestructive method for root dentin moisture measurements: in vitro pilot study

Effects of different storage media on dentin moisture, microhardness, and bond strength of resin composite

Background

In in vitro studies, it is desirable that the storage solutions in which dental samples kept between extraction and experiment should prevent dehydration and have antimicrobial properties. However, it should be taken into consideration that these solutions may have some effects that directly change test results on physical and mechanical properties of laboratory samples.

Aims

The aim of this in vitro study was to evaluate the effects of different storage media on dentin moisture, microhardness, and microshear bond strength of resin composite to dentin. Thirty non-carious human premolars were randomly divided into three groups: 1. 0.1% Thymol (T), 2. Distilled water (DW), 3. Dry storage (DS) (control) (n = 10). Dentin moisture was measured with a digital grain moisture meter. Dentin microhardness was measured with the Vickers test. The bond strength was measured with a microshear test.

Materials and Methods

Analysis of variance (ANOVA) followed by the Bonferroni test was used for statistical evaluation (p = 0.05).

Results

Dentin moisture of the experimental groups was statistically higher than that of the control group (p < 0.05). In addition, the dentin moisture of group DW was significantly higher than that of group T (p < 0.05). The mean microshear bond strength of resin composite to dentin was higher in group DW than in group T and group DS (p < 0.05), while there was no statistical difference between group T and group DS. The microhardness values of all groups were statistically similar.

Conclusions

Storage solutions used for disinfection and to prevent dehydration may have negative effects on dentin moisture and bond strength.

Inline 3D Volumetric Measurement of Moisture Content in Rice Using Regression-Based ML of RF Tomographic Imaging

The moisture content of stored rice is dependent on the surrounding and environmental factors which in turn affect the quality and economic value of the grains. Therefore, the moisture content of grains needs to be measured frequently to ensure that optimum conditions that preserve their quality are maintained. The current state of the art for moisture measurement of rice in a silo is based on grab sampling or relies on single rod sensors placed randomly into the grain. The sensors that are currently used are very localized and are, therefore, unable to provide continuous measurement of the moisture distribution in the silo. To the authors’ knowledge, there is no commercially available 3D volumetric measurement system for rice moisture content in a silo. Hence, this paper presents results of work carried out using low-cost wireless devices that can be placed around the silo to measure changes in the moisture content of rice. This paper proposes a novel technique based on radio frequency tomographic imaging using low-cost wireless devices and regression-based machine learning to provide contactless non-destructive 3D volumetric moisture content distribution in stored rice grain. This proposed technique can detect multiple levels of localized moisture distributions in the silo with accuracies greater than or equal to 83.7%, depending on the size and shape of the sample under test. Unlike other approaches proposed in open literature or employed in the sector, the proposed system can be deployed to provide continuous monitoring of the moisture distribution in silos.

[Effects of different methods on drying root canal by near-field microwave detection system]

OBJECTIVE

To set up near-field microwave detection system, to evaluate the accuracy of measuring water and to compare the effects of different methods on drying root canal.

METHODS

Known and quantitative distilled water in Eppendorf tube and root canal was detected by near-field microwave detection system which was set up first. The microwave reflection coefficient was recorded so as to evaluate the accuracy of the measuring water. 12 single-rooted mandibular premolar teeth with apical matureness and a curvature less than 10° were decoronated, leaving roots 14 mm in length. After instrumentation to F3, the root canals were air-dried and injected with 10 μL distilled water each. Then all the root canals were assigned to 4 groups (n=12) according to different methods on root canal drying. Near-field microwave detection system was used to detect the change of water after air-drying and root canal drying so as to evaluate the effects of different root canal drying methods: (1) negative control group, the canals were injected with 10 μL distilled water and no root canal drying method was performed; (2) paper points drying experimental group, four #60 paper points were used to blot-dry the middle and upper part of the canal, followed by #40 paper points blot-drying the apical area. The above step was repeated with the tip of paper point that appeared with no water under microscope as finished; (3) 95% (volume fraction) ethanol drying experimental group, after the distilled water was removed with paper points (similar to paper points experimental group), 10 μL 95% ethanol was injected into the canal and was left in place for 10 s, then paper points were used to dry the canal; (4) 70% (volume fraction) isopropyl alcohol drying experimental group, after the distilled water was removed with paper points (similar to paper points experimental group), 10 μL 70% isopropyl alcohol was injected into the canal and was left in place for 10 s, then paper points were used to dry the canal. The linear correlation analysis was used to test the accuracy of the measuring water by near-field microwave detection method and physical measurement. The Pearson correlation coefficient was calculated based on the data. The effects of different methods on drying root canal were analyzed by Chi square test.

RESULTS

The R2 for the microwave reflection coefficient and the physical measurement of the water in Eppendorf tube and root canal were 0.991 and 0.970. The microwave reflection coefficient in all the experimental groups showed significant difference (P<0.05). After drying with paper points, the residual water was the most, and the microwave reflection coefficient was the highest: 0.023. While after 70% isopropyl alcohol drying root canal, the residual water was the least with the microwave reflection coefficient 0.006, showing that the effect of drying was the best.

CONCLUSION

Near-field microwave detection system could detect the change of water in root canal. The effect of root canal drying by 70% isopropyl alcohol was superior to 95% ethanol and paper points.

Chronologic comparison of root dentin moisture in extracted human teeth stored in formalin, sodium azide, and distilled water

This study quantified in vitro the root dentin moisture when 10% formalin (group A), 3% sodium azide (group B), and distilled water (group C) were used as teeth storage media. The root dentin moisture of 66 extracted human mandibular single-rooted teeth was measured at baseline (day 0) and at 1, 3, 7, and 14 days using a digital grain moisture meter. The baseline dentin moisture value was used as covariate in the generalized estimating equation (GEE) analysis. The mean dentin moisture values (%) +/- SD on days 0, 1, 3, 7, and 14 were, respectively: 10.6 +/- 0.64, 14.3 +/- 0.71, 14.6 +/- 0.84, 14.4 +/- 0.64, and 14.7 +/- 0.75 in group A; 11.4 +/- 0.94, 14.6 +/- 0.95, 14.6 +/- 0.76, 14.6 +/- 0.93, and 14.8 +/- 0.81 in group B; and 10.2 +/- 0.95, 12.8 +/- 0.90, 13.3 +/- 0.95, 13.0 +/- 0.91, and 13.2 +/- 0.89 in group C. The dentin moisture increased in all 3 groups; however, there was no overall significant difference in moisture between the formalin and sodium azide groups.

Root dentin body moisture changes caused by ascorbic acid

OBJECTIVES

To quantify in vitro the root dentin moisture (DM) when soaked in 10% ascorbic acid solution (Group A) and distilled water (Group B) for up to 14 days.

METHODS

Forty-four extracted human mandibular single-rooted teeth were sectioned perpendicular to the long axis at the CEJ to access the root dentin. The samples were divided into Groups A and B. Baseline (day 0) DM was measured using a digital grain moisture meter. One sample was placed in each tube, which was then filled with solution. All tubes were kept at 37 degrees C and 100% humidity. DM was measured after 1, 3, 7, and 14 days. The baseline DM value was used as a covariate in the generalized estimating equation (GEE) analysis to account for the difference in the baseline DM between the two groups.

RESULTS

The mean DM (%) values+/-standard deviation on days 0, 1, 3, 7, and 14 were 11.4+/-1.08, 17.1+/-0.87, 18.2+/-0.76, 18.4+/-0.77, and 17.9+/-0.90 in Group A, and 10.2+/-0.95, 12.8+/-0.90, 13.3+/-0.95, 13.0+/-0.91, and 13.2+/-0.89 in Group B, respectively. Group A had significantly higher baseline DM than Group B (p=0.006). After adjusting for differences in the baseline, the GEE analysis indicated that, on average, Group A had a significantly higher increase in DM than Group B, with means+/-standard deviation of 4.35+/-0.26.

CONCLUSIONS

The moisture increase in the ascorbic acid group was greater than that in the distilled water group. Soaking root dentin in the unreplenished ascorbic acid solution or distilled water beyond 3 days did not further increase DM.