I will continue the introduction to observational studies by explaining some of the common nomenclature that might also be encountered in randomized controlled trials. We often use the terms exposure and outcome . Exposure is a potential risk factor, and we are interested in whether it is associated with the outcome, which could be a condition, disease, health measure, or behavior of interest. For example, if we are assessing the association between orthodontic therapy and periodontal conditions, the exposure is the orthodontic therapy, and the outcome is the periodontal condition, which can be measured as sulcus depth, bone height, and so on. Other examples of exposures and outcomes relevant to orthodontics are shown in Table I .
|Dental agenesis||Canine impaction|
|Early loss of maxillary deciduous canine||Maxillary canine impaction|
|Orthodontic treatment||Dental caries|
|Nonextraction therapy||Third molar impaction|
|Cleft palate||Dental agenesis|
|Water fluoridation||Dental caries|
|Socioeconomic status||Oral hygiene status|
Exposures and outcomes are often described with alternative names, which are shown in Table II .