glmtoolbox (version 0.1.12)

rinse: Dental Clinical Trial

Description

These data arose from a study in dentistry. In this trial, subjects were generally healthy adult male and female volunteers, ages 18–55, with pre-existing plaque but without advanced periodontal disease. Prior to entry, subjects were screened for a minimum of 20 sound, natural teeth and a minimum mean plaque index of 2.0. Subjects with gross oral pathology or on antibiotic, antibacterial, or anti-inflammatory therapy were excluded from the study. One hundred nine volunteers were randomized in a double-blinded way to one of two novel mouth rinses (A and B) or to a control mouth rinse. Plaque was scored at baseline, at 3 months, and at 6 months by the Turesky modification of the Quigley-Hein index, a continuous measure. Four subjects had missing plaque scores. The main objective of the analysis is to measure the effectiveness of three mouth rinses at inhibiting dental plaque.

Usage

data(rinse)

Format

A data frame with 315 rows and 7 variables:

subject

a character string giving the identifier of the volunteer.

gender

a factor indicating the gender of the volunteer: "Female" and "Male".

age

a numeric vector indicating the age of the volunteer.

rinse

a factor indicating the type of rinse used by the volunteer: "Placebo", "A" and "B".

smoke

a factor indicating if the volunteer smoke: "Yes" and "No".

time

a numeric vector indicating the time (in months) since the treatment began.

score

a numeric vector giving the subject’s score of plaque.

References

Hadgu A., Koch G. (1999) Application of generalized estimating equations to a dental randomized clinical trial. Journal of Biopharmaceutical Statistics 9:161-178.

Examples

data(rinse)
dev.new()
boxplot(score ~ time, data=subset(rinse,rinse=="Placebo"),ylim=c(0,3.5),
        at=c(1:3)-0.2, col="yellow", xaxt="n", boxwex=0.15)
boxplot(score ~ time, data=subset(rinse,rinse=="A"), add=TRUE,
        at=c(1:3), col="gray", xaxt="n", boxwex=0.15)
boxplot(score ~ time, data=subset(rinse,rinse=="B"), add=TRUE,
        at=c(1:3) + 0.2, col="blue", xaxt="n", boxwex=0.15)
axis(1, at=c(1:3), labels=unique(rinse$time))
legend("bottomleft",legend=c("placebo","rinse A","rinse B"),
       title="Treatment",fill=c("yellow","gray","blue"),bty="n")