Aim of the in vitro study was to evaluate the time period needed to re-establish enamel surface microhardness after bleaching with fluoridated (0.5% F− as NaF) and unfluoridated carbamide peroxide (CP) bleaching gels under a daily de- and remineralization protocol.
Therefore it was difficult to evaluate which time period was most important in relation to health effects.
Because of the strong correlation between maternal smoking during and after pregnancy, we could not evaluate which time period contributed most to the effects we observed.
In order to evaluate time trends, we divided the observation period into four periods: 1985 89, 1990 94, 1995 99, and 2000 04.
Given that the study drugs are generally administered in seven day treatment regimens, a follow-up of 37 days allowed effects of treatment to be evaluated for time periods up to 30 days after treatment had ended.
We examined the risk of fracture in the 6 observation periods by evaluating time to fracture as shown in Figure 2.
The proposed modeling approach is applied to states (Arizona, California, Colorado, Nevada, New Mexico, and Utah) in the southwestern U.S., where conditional forecasts of climate-change variables are evaluated against recent (2012) observations, evaluated at a future time period (2030), and evaluated as future trends (2009 2059).
However it seems consensual that in child's questions it is more appropriate and reliable to evaluate short time periods.
The strengths of this study include the large number of birth records, high quantity of exposure data (including some biweekly data), and the ability to evaluate multiple time periods of exposure to specific THMs and HAAs.
