Understanding Whitening Gel Strengths, Why Some Products Need a Consultation First
Whitening gels are usually described by their percentage of hydrogen peroxide (HP) or carbamide peroxide (CP) — the active ingredients that lift staining from the tooth surface. The strength of a gel affects both how quickly it works and how it needs to be supplied.
Hydrogen Peroxide vs Carbamide Peroxide
Carbamide peroxide breaks down into hydrogen peroxide once applied, at roughly a 3:1 ratio — so a 16% carbamide peroxide gel is roughly equivalent to a 5–6% hydrogen peroxide gel. Product labels usually state one or the other, which is worth checking when comparing strengths.
Why Some Products Are Available Without an Appointment
Under Dental Board of Australia guidelines, whitening products at or below 6% hydrogen peroxide (or the carbamide peroxide equivalent) can be sold directly to the public. This is why products like Opalescence Go 6% and Philips Zoom DayWhite 6% are available to purchase online without booking in first.
Why Higher-Strength Products Require a Consultation
Anything above that threshold — including Philips Zoom DayWhite 9.5% and 14%, Philips Zoom NiteWhite 22%, and Opalescence Go 15% — can only be supplied or administered by a registered dental practitioner. This isn't a sales barrier; it's a safety measure. A consultation allows your teeth, gum health and sensitivity to be assessed before a stronger formula is recommended, and gives you the chance to be shown exactly how to use it.
Managing Sensitivity
Most whitening gels, regardless of strength, contain potassium nitrate and fluoride to help reduce sensitivity and support enamel health during treatment. Sensitivity varies from person to person and isn't necessarily linked to gel strength alone.
Not Every "Whitening" Product Contains an Active Whitening Ingredient
Not all products marketed as "whitening" contain hydrogen peroxide or carbamide peroxide. Some — particularly certain toothpastes, powders and rinses — work mainly through mild abrasives or polishing agents that remove surface stains, rather than a bleaching action that changes the underlying tooth colour. These can help maintain a clean, polished look between whitening treatments, but they aren't a substitute for a peroxide-based product if the goal is to actually lift staining.
The Takeaway
Higher whitening gel strengths aren't simply "stronger versions" of the same product — they come with additional regulatory and safety requirements. If you're unsure which strength is right for you, a whitening consultation is the best starting point.
Read next: What's the Difference Between In-Chair and Take-Home Whitening?
Book a whitening consultation.
Source for the regulatory detail above: Australian Dental Association Policy Statement 2.2.8, "Teeth Whitening (Bleaching) by Persons Other Than Dental Practitioners"; Dental Board of Australia teeth whitening guidance (dentalboard.gov.au).