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Comparison of smartphone camera and conventional flatbed scanner images for analytical evaluation of chewing function.

BACKGROUND
The two-color mixing-test is a quick method to assess chewing function (CF). The use of smartphone cameras for acquiring images may help in further simplifying the process.


OBJECTIVE
This study evaluated the reliability of smartphone-camera images of chewing gums to assess CF.


METHODS
Five test samples of a bi-colored chewing gum were produced by a single fully dentate adult volunteer. The specimens were flattened to 1 mm thick wafers. The two sides of the wafers were digitized with a conventional flatbed scanner (control), and were photographed 20 times using 8 different smartphones. The images were assessed opto-electronically to obtain the variance of hue (VoH), and subjectively by visual assessment (SA) using a categorical scale (SA1-SA5). Spearman's correlation and regression models were used for statistical analyses.


RESULTS
The intra-group variability for SA1-SA3 was <1% for all smartphones, but significantly higher than controls for SA4 and SA5 (Smartphone: SA4=5.57%; SA5=8.76%; control: SA4=2.5%; SA5=0.79%). VoH was progressively lower from SA1 to SA5 for all imaging devices (r>-0.97; p<.001). VoH comparisons between control and smartphone images revealed significant differences for the individual SA categories, however, the magnitude of differences was small and non-significant when the full range of SA levels were considered. The linear mixed model regression showed significant effects for all the smartphones (p<0.001) and SA levels (p<0.001) in relation to the flatbed scanner values.


CONCLUSIONS
Smartphone cameras may be used to evaluate color-mixture for a bolus-kneading test, however the precision is lower with higher degrees of color-mixing.