These results indicated that the visual scoring method was valid and reliable for evaluation of masticatory performance.

Objective methods for evaluating masticatory performance are invaluable for quantitative comparisons between various dental treatments as well as diagnosing masticatory disorder. The purpose of this study was to develop an accurate method for automatically measuring masticatory performance using a new measuring device consisting of light-emitting diodes and a photodiode and test gummy jelly. First, the relationship between six known β-carotene concentrations in aqueous solution and the voltage values exhibited on a photodiode was investigated. Mean voltage obtained by red light incident on the photodiode indicated a significantly high correlation (r=0·999 in a cubic function, P<0·01) with β-carotene concentration in the aqueous solution. Second, to establish the optimal measuring conditions for evaluating masticatory performance, factors influencing mean voltage were investigated, such as water temperature and times for rinsing the gummy jelly and dissolving β-carotene from the jelly. A stable mean voltage was obtained by measuring under the following conditions: rinsing water temperature, 35°C; rinsing time, 30s; water dissolving temperature, 35°C; dissolving time, 10s. Finally, the relationship between seven surface area values of divided gummy jelly and β-carotene concentrations dissolved from the divided jellies was investigated. The increase in surface area of divided test gummy jelly particles was accurately calculated (r=0·992, P<0·001) from mean voltage on the photodiode to change with β-carotene concentration dissolved from the jelly surface. This new method using test gummy jelly and an automatic measuring device appears useful for precisely evaluating masticatory performance.

Despite the importance of masticatory performance in health promotion, assessment of masticatory performance has not been widely conducted to date because the methods are labour intensive. The purpose of this study is to investigate the accuracy of a novel system for automatically measuring masticatory performance that uses β-carotene-containing gummy jelly. To investigate the influence of rinsing time on comminuted jelly pieces expectorated from the oral cavity, divided jelly pieces were treated with two types of dye solution and then rinsed for various durations. Changes in photodiode (light receiver) voltages from light emitted through a solution of dissolved β-carotene from jelly pieces under each condition were compared with those of unstained jelly. To investigate the influence of dissolving time, changes in light receiver voltage resulting from an increase in division number were compared between three dissolving times. For all forms of divided test jelly and rinsing times, no significant differences in light receiver voltage were observed between any of the stain groups and the control group. Voltages decreased in a similar manner for all forms of divided jelly as dissolving time increased. The highest coefficient of determination (R(2)  = 0·979) between the obtained voltage and the increased surface area of each divided jelly was seen at the 10 s dissolving time. These results suggested that our fully automatic system can estimate the increased surface area of comminuted gummy jelly as a parameter of masticatory performance with high accuracy after rinsing and dissolving operations of 10 s each.