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I Heynderickx

Publications and source records attributed to I Heynderickx.

6 recordsLinked to original sources
PubMed2005

Statistical methods for testing plaque removal efficacy in clinical trials.

OBJECTIVES: To evaluate the ability of different statistical approaches in finding a statistically significant difference in plaque removal efficiency between brushes in clinical trials. MATERIALS AND METHODS: The approaches, which are evaluated, concern the scores after brushing only, the difference in scores before and after brushing and the relative difference scores (i.e. score before minus score after brushing divided by the score before brushing). In each case the scores before brushing may be included as a covariate. Except for the relative difference scores, the power of the test statistics of the approaches has been compared by assuming a simple statistical model. These theoretical results have been compared with the numerical results of two particular clinical trials--one with a between-subject design and one with a within-subject design. RESULTS: The numerical results of these clinical trials show that the calculated p-values support the conclusions drawn from the statistical model, i.e. the power of the F-test is highest when evaluating the data after brushing with the data before brushing included as a covariate. Using the differences in scores before and after brushing--again with the data before brushing as a covariate--does not add additional power to the test. Omitting the data before brushing as a covariate only gives satisfactory results when the variance over the subjects or the error variance is zero, which in general is not the case. CONCLUSIONS: This investigation reveals that in general the approach of analysing the scores after brushing with the scores before brushing as a covariate yields the highest chance of finding a statistically significant difference between two brushes.

Adult↗
PubMed2001

Influence of a controlled pressure system on toothbrushing behavior.

The use of excessive brushing force has been shown to be a major cause of gingival abrasion. To aid in preventing over-vigorous brushing, the Philips/Jordan electric toothbrush incorporates a Controlled Pressure system (CPS) that causes the brush head to flex back when a toothbrushing force (TBF) in excess of a pre-determined threshold is exerted against the teeth or soft tissues. Two studies (I/II) were conducted to determine whether this mechanical feedback system is sufficiently sensitive to enable users to control their brushing behavior. In Study I, the learning pattern of brushing behavior as a response to the feedback system was evaluated. Seventeen subjects were asked to brush their teeth under observation at least twice a day for a two-week period. During these observations, the number of clicks, as well as the time the brush was pushed "through the click" were recorded. Ten of seventeen volunteers demonstrated a clear learning behavior; the mean number of clicks/minute (for all subjects) was reduced from 10 to 4 after 10 sessions of brushing, and then to 2 or 3 clicks at the end of two weeks. In Study II, 46 subjects used the electric toothbrush with the CPS click force set at various levels between 150-420 g (at 30 g intervals). After a 4-week learning period, the mean TBF was determined in each subject. TBF was most strongly influenced at pre-set click forces between 180 and 270 g. The mean TBF was lowest (about 80 g) when the threshold was set at 210 or 240 g; it then increased (to about 130-140 g TBF) both for smaller and larger values of the threshold setting. Hence, both studies indicate that the Controlled Pressure system is a functional feature that can be used to control the habitual brushing force in a learning period of less than 2 weeks.

Adult↗