Recall intervals: six months for everyone is a convention, not a recommendation

The six-month interval between hygiene appointments is the most widespread recommendation in dentistry and one of those with the weakest foundations.

Its origin is historical rather than derived from clinical trials: it settled over time as an organisational habit, and it has persisted because it is easy to remember and to schedule.

The problem is that it applies the same interval to patients with very different risks. A healthy adult without pockets and with good hygiene, and a periodontal patient in maintenance, do not have the same needs.

For the former, six months may be more than necessary. For the latter it is too long, and within that interval the subgingival biofilm reorganises until progression resumes.

The evidence on periodontal maintenance points to intervals of three or four months as the reference in treated patients, and it is among the factors determining long-term stability.

It is not the appointment itself that makes the difference, but the fact that the biofilm is disrupted before reaching the maturity and composition capable of reactivating destruction.

The criteria for personalising the interval are identifiable. A history of treated periodontitis, inadequate plaque control, smoking, diabetes, xerostomia, the presence of implants, complex prosthetic work.

On the caries side, recent lesions, a diet with frequent sugar exposures, orthodontic appliances and reduced salivary flow all weigh in.

Structured risk assessment tools have the advantage of making the decision explicit and repeatable, and above all of making it comprehensible to the patient.

A patient shown which factors underlie a three-month interval accepts the greater frequency far more readily than one to whom it is simply announced.

The interval should be reviewed over time and in both directions. A patient stable for years can move to longer intervals; one deteriorating should be shortened before the situation consolidates.

The recall is not merely instrumentation. It is when probing is reassessed, technique is checked with a disclosing agent, restorations and prostheses are examined, and mucosal lesions are intercepted. Reducing it to a cleaning wastes most of its value.

In summary: six months is a historical convention, periodontal maintenance calls for three or four, risk criteria should be made explicit to the patient, and the interval is reviewed periodically in both directions.