ABSTRACT
In this work, we describe a methodology for developing a mathematical model based on infrared (IR) detection to determine the moisture content (M) in solid samples. For this purpose, an experimental setup was designed, developed and calibrated against the gravimetric method. The experimental arrangement allowed for the simultaneous measurement of M and the electromotive force (EMF), fitting the experimental variables as much as possible. These variables were correlated by a mathematical model, and the obtained correlation was M=1.12×exp(3.47×EMF), ±2.54%. This finding suggests that it is feasible to measure the moisture content when it has greater values than 2.54%. The proposed methodology could be used for different conditions of temperature, relative humidity and drying rates to evaluate the influence of these variables on the amount of energy received by the IR detector.
ABSTRACT
PURPOSE: To clinically evaluate and compare a dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate (Test Dentifrice delivering 0.243% sodium fluoride), to a dentifrice containing 0.243% sodium fluoride in a silica base (Positive Control Dentifrice). MATERIALS AND METHODS: This study was conducted in harmony with the published 1988 American Dental Association guidelines for studies geared toward the comparison of fluoride dentifrices. This 2-yr caries clinical study employed a double-blind, parallel-group design, and involved 6-10 yr-old children from the metropolitan area of Maceio, Alagoas, Brazil. Qualifying subjects were stratified according to age and sex, and were randomly assigned to the two treatment groups, with multiple subjects in the same household all assigned to the dentifrice randomly allocated to the first among them. Caries examinations were conducted in accordance with U.S. Food and Drug Administration guidelines for the clinical evaluation of drugs to prevent dental caries. One calibrated examiner performed all the measurements. After treatment assignment, study participants were instructed to brush their teeth at home with their assigned dentifrice at least twice daily. Brushing instructions were reinforced by indoctrination in proper oral hygiene techniques by dental professionals, supplemented by pamphlets supplied by the sponsor and yearly mailings to participants, emphasizing good oral hygiene and the need to enforce compliance with the study. Post-baseline examinations were performed after 1 yr of product use, and again after 2 yrs of product use. RESULTS: Two thousand four hundred thirty-two (2,432) subjects completed this 2-yr study. For these subjects, the mean caries scores (DMFS, decayed, missing and filled tooth surfaces) at baseline were 3.84 for the Test Dentifrice group, and 4.06 for the Positive Control Dentifrice group. For caries increments after 1 yr, the respective means were 2.02 for the Test Dentifrice group and 2.12 for the Positive Control Dentifrice group. Finally, after 2 yrs, the mean caries increments were 4.30 for the Test Dentifrice group, and 4.83 for the Positive Control Dentifrice group. No statistically significant difference was indicated between the treatment groups at baseline or between the 1-yr caries increment scores. However, there was a statistically significant difference in the 2-yr caries increment scores between the treatment groups. Relative to the Positive Control Dentifrice group, the Test Dentifrice group presented a 10.97% reduction in caries increment scores at 2 yrs. In accordance with the procedures and standards provided by the published guidelines of the American Dental Association for the comparison of the anticaries efficacy of fluoride dentifrices, the results of this study support the conclusion that the dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate, delivering 0.243% sodium fluoride, provided a superior level of anticaries efficacy than did the dentifrice containing 0.243% sodium fluoride in a silica base.
