Descriptive statistics summarize and describe the characteristics of a sample, while inferential statistics use data from a sample to make predictions or inferences about the population from which the sample was drawn.

Clinical studies often measure the effectiveness of caries inhibiting preparations by comparing the number of new decayed, filled, and missing tooth surfaces that appear over the course of the study period.

For optimal fluoride uptake and protection against dental caries, tooth surfaces should be exposed to topical fluorides for at least 4 minutes.

The correct concentration for topically applied acidulated phosphate fluoride is 1.23% (Answer: 2). This concentration is commonly used in various dental products like gels, foams, and varnishes for professional in-office applications to strengthen tooth enamel and prevent decay. It is acidulated to facilitate better penetration into the enamel.

The OHI-S (Oral Hygiene Index-Simplified) index of Greene and Vermillion evaluates oral hygiene by assessing the extent to which calculus and debris cover six specified tooth surfaces (Answer: 4). This index is a simplified version of the original OHI index and is widely used in dental practice and research to evaluate the level of oral hygiene. It looks at the presence of debris and calculus on the lingual, labial, and buccal surfaces of the upper right first molar, lower left first molar, upper right central incisor, and lower left central incisor.