In 1992 and 1997, all US and Canadian dental schools were surveyed by mail regarding the preferred initial radiographic examination prescribed for non-emergency, comprehensive-care patients (dentulous adults, edentulous adults, and children). In both survey years, a minority of US and Canadian dental schools reported using selection criteria for dentulous adults and children, while nearly all schools reported doing so for edentulous adults. The purpose of this secondary analysis was to investigate the relationship between the use of radiology selection criteria (vs. predetermined routine examinations) in US and Canadian dental school clinics and three factors: (1) the credentials of the chief-of-service, (2) institutional funding, and (3) geographic region. "Credentials of the chief-of-service" is the single factor significantly related to the distributions of radiographic examinations prescribed for dentulous adults in both years (Fisher exact test, p