Air polishing powders: glycine works where bicarbonate is contraindicated

Air polishing has moved from a technique for removing stains to a debridement tool, and the change was made possible by low-abrasivity powders.

Sodium bicarbonate is the historical powder, with particles around 65 micrometres. It is effective on supragingival stains and on intact enamel, and has no other indications.

On dentine, cementum, composite restorations and implant surfaces it is contraindicated, because the abrasion is disproportionate to the hardness of the substrate.

It also carries a sodium content that argues against use in patients with poorly controlled hypertension or on a low-sodium diet, a detail that rarely appears in the history.

Glycine has much finer particles, around 25 micrometres, and far lower abrasivity. It is this difference that opened up subgingival use.

With a dedicated nozzle, glycine powder reaches pockets several millimetres deep and disrupts biofilm without mechanical instrumentation, in less time and with less discomfort for the patient.

On exposed root surfaces and implants glycine is now the reference, because it removes biofilm without altering the surface. On titanium it is preferable to any contact instrumentation.

Erythritol has finer particles still, around 14 micrometres, with further reduced abrasivity. It also has documented activity against Streptococcus mutans, adding an effect beyond the mechanical one.

The choice between glycine and erythritol turns on narrow margins of efficacy; erythritol is preferable where maximum gentleness is required and cost is not the main constraint.

Technique changes with the powder. Bicarbonate is used with the nozzle at a distance and in continuous motion; fine subgingival powders require a slim nozzle inserted into the pocket with a vertical movement.

High-volume suction is not optional. The aerosol produced contains particles and biological material, and without adequate suction the risk to the operator and environmental contamination are real.

Contraindications include respiratory disease in the acute phase, because of aerosol inhalation, and inflamed or ulcerated mucosa, where the jet causes pain and can produce subcutaneous emphysema.

In summary: bicarbonate supragingivally on enamel only, glycine for subgingival work, implants and root surfaces, erythritol where maximum gentleness is needed, high-volume suction always, and respiratory contraindications checked.