Evidence exists that some dentists may be failing to perform adequate periodontal diagnostic and preventive care for their patients. Continuing education (CE) is an avenue that is frequently employed as a strategy to alter the style of practice. This paper presents an evaluation of a year‐long continuing education intervention “Periodontics in General Practice”, conducted among randomly selected private general dental practices in Adelaide. South Australia. The CE intervention featured a 1‐day seminar, bi‐monthly newsletters, individualised 3‐monthly comparative feedback, and technical assistance. The study employed a longitudinal quasi‐experimental design, which allowed for evaluation of the effectiveness of the intervention among practices employing hygienists (n: = 12) and not employing dental hygienists (n: = 12), taking into account the covariates of baseline level of provision of periodontal services, the practice's level of participation in the intervention and attendance at other CE courses in periodontics over the year. A comparison group of practice (n: = 12) did not participate in the intervention over the year. Patient record audits, conducted at baseline and at 12 months, provided data for the evaluation of the effect of the intervention on the recording of periodontal diagnostic, preventive and treatment items. Practices participating in the intervention showed increases in the percentage of records containing at least one periodontal diagnostic notation, and those practices employing hygienists showed an increase in the percentage of records with at least one preventive notation and one treatment item. Using ANCOVA to account for covariation, the main effect of the study group was significant in explaining changes in the provision of preventive periodontal services. The results indicate that an extended continuing education intervention can have significant effect on the provision of periodontal services, and that the magnitude of the effect differs between practices employing and not employing hygienists.