Hydrogen peroxide and carbamide peroxide are both used in professional whitening, but they work at different speeds and suit different treatment settings. Most providers use both — HP for in-office chairside treatment, CP for take-home maintenance. Here's the clinical rationale for that distinction and what professionals actually need to know about each.
HP vs CP: How Each Agent Whitens Teeth
Hydrogen Peroxide (HP)
Hydrogen peroxide is the directly active whitening agent. When HP gel contacts the tooth surface, hydrogen peroxide molecules immediately begin penetrating enamel and dentin. Inside the tooth, H₂O₂ releases oxygen radicals that break apart the carbon double bonds in stain chromophores — the molecular structures responsible for tooth discoloration. The result is that stain molecules lose their color. HP works from first contact.
Carbamide Peroxide (CP)
Carbamide peroxide (also called urea peroxide) is a compound that breaks down into hydrogen peroxide and urea when it contacts moisture. The important number: roughly one-third of the carbamide peroxide concentration converts to active hydrogen peroxide. A 30% CP gel produces approximately 10% active HP. A 44% CP gel produces approximately 14–15% active HP.
Because this conversion takes time, CP releases hydrogen peroxide more slowly and over a longer period than HP gel at equivalent concentrations. This makes CP's whitening effect more gradual — and its tolerability better for extended contact times.
HP for Chairside, CP for Home: Why the Setting Matters
The speed difference between HP and CP maps directly to the best treatment setting for each:
| Factor | Hydrogen Peroxide | Carbamide Peroxide |
|---|---|---|
| Active agent | Directly H₂O₂ | Converts to H₂O₂ over time |
| Whitening onset | Immediate from application | Gradual — begins as conversion occurs |
| Session length | 30–60 minute chairside session | Hours to overnight — designed for extended home use |
| Best setting | In-office chairside treatment | Home tray whitening, take-home maintenance |
| Sensitivity profile | Moderate–High (concentration-dependent) | Lower — gradual release is more tolerable for extended contact |
| LaserGlow products | HP Gels 16%–44% | 44% CP Pen |
HP and CP Concentration Equivalents
Because CP converts to HP at roughly a 3:1 ratio (CP:active HP), comparing concentrations requires translating between them. This matters when discussing equivalent whitening strength with clients or when reading product specifications.
| Carbamide Peroxide % | Approximate Active HP Released | Equivalent HP Gel Strength |
|---|---|---|
| 10% CP | ~3.3% HP | Below professional HP range |
| 16% CP | ~5.3% HP | Below professional HP range |
| 22% CP | ~7.3% HP | Below 16% HP |
| 35% CP | ~11.7% HP | Below 16% HP |
| 44% CP | ~14.7% HP | Below 16% HP |
How Professional Whitening Practices Use Both
Professional whitening practices typically use HP and CP together in a two-phase approach, not as competing alternatives:
- Phase 1 — In-office HP session: Chairside whitening with 25%, 35%, or 44% HP gel. Full gingival barrier, LED activation, provider-supervised session. Fast visible results in a single appointment.
- Phase 2 — CP home maintenance: Client uses the 44% CP pen at home for maintenance whitening and event-based touch-ups. No provider supervision required for maintenance.
This approach gives clients the best of both: immediate results from the in-office HP session, and a practical home option for maintaining shade without repeating the full chairside service for every touch-up.
HP vs CP Whitening FAQ
Which is better for professional whitening — hydrogen peroxide or carbamide peroxide?
HP is better for in-office chairside whitening because it's directly active and delivers fast results in a single session. CP is better for home maintenance whitening because its gradual release suits extended contact times and is more tolerable for hours-long home tray use. Professional practices typically use both — HP for in-office treatment, CP for take-home follow-up. The question isn't which is "better" overall; it's which is better for the specific treatment setting.
Is 44% carbamide peroxide the same as 44% hydrogen peroxide?
No — they are significantly different in whitening strength. 44% CP releases approximately 14–15% active HP as it breaks down. LaserGlow's 44% HP gel delivers 44% active hydrogen peroxide directly from application. The CP percentage refers to the carbamide compound concentration, not the active HP concentration. Compare them by active HP content, not by the number on the label.
Can clients whiten at home with carbamide peroxide after an in-office HP treatment?
Yes — this is the standard two-phase professional whitening approach. The in-office HP session delivers immediate results; the client continues with a CP take-home product (like the 44% CP pen) to maintain shade between professional visits. There's no required waiting period between the in-office HP session and starting CP home maintenance, as long as there's no significant sensitivity from the in-office appointment.
Why does carbamide peroxide cause less sensitivity than hydrogen peroxide?
CP's gradual hydrogen peroxide release is the main reason. Sensitivity during whitening is associated with the concentration and speed of HP penetrating enamel and dentin. Because CP converts to HP gradually, the active HP concentration in contact with dental tissue at any given moment is lower than with a direct HP gel of equivalent concentration labeling — which reduces the intensity of the sensitivity response.
Do carbamide peroxide gels require gingival barrier?
Home-use CP products like pens and take-home trays don't typically use gingival barrier because they're designed for self-application with lower active HP concentrations and extended contact times. Professional CP gels used in-office under provider supervision follow the same barrier protocol as HP gels at equivalent active-HP concentrations. For the LaserGlow 44% CP pen used at home, barrier is not required as part of standard home maintenance use.
