Oral hygiene phase revisited: How different study designs have affected results in intervention studies

Every periodontal researcher have been taught, and every textbook in periodontics have advocated, that a phase in which the patient is meticulously motivated and instructed in proper oral hygiene-the oral hygiene phase-must be included in any periodontal intervention. However, how is this oral hygiene phase actually portrayed in periodontal intervention studies, and how much space have this important phase received in the planning and carry-through of intervention studies? The purpose of this letter to the editor was to review current literature in the period 1975/01/01-2017/12/31 on periodontal, mechanical intervention studies in order to see what focus the oral hygiene phase had received in these articles. The result showed that the oral hygiene phase is variable in length and content, variable in claimed result, insufficiently described, and invariably amalgamated with the scaling and root planing which is the intervention or part of an intervention. The consequences of these findings are discussed and suggestions proposed for more harmonized and calibrated oral hygiene phase introduced to avoid biased and inflated results of interventions.