Professional teeth whitening: how it works and how long it lasts

by Dr Nihad Pljevljak | Nov 30, 2025

Professional teeth whitening is the gold standard for a brighter smile, using scientifically validated clinical protocols. Dr Nihad Pljevljak, at Nea Bios Dental Clinic in Rome EUR Laurentina, uses advanced cosmetic dentistry techniques to achieve safe, long-lasting results, tailoring each treatment to the individual characteristics of the patient.

The biochemistry of professional whitening

Professional teeth whitening is based on a controlled oxidation-reduction reaction. The whitening agents, mainly hydrogen peroxide (H₂O₂) or carbamide peroxide, pass through the enamel to reach the dentine, where they break down into oxygen free radicals.

These radicals break up the chromophore macromolecules responsible for discolouration, turning them into colourless, low-molecular-weight compounds. According to a recent meta-analysis of laboratory studies, when recommended protocols are followed whitening causes at most a slight reduction in enamel surface hardness, with no evidence of clinically meaningful effects.

Clinical protocols and therapeutic concentrations

In-office whitening

In international studies, in-office treatment often uses high-concentration hydrogen peroxide (around 25-35%); in the European Union, however, tooth whitening products may contain no more than 6% hydrogen peroxide, whether present as such or released from other compounds such as carbamide peroxide. The procedure involves:

Protecting the soft tissues with a light-cured liquid dam
Applying the whitening gel for 15-20 minutes
Optional activation with LED lamps, which according to systematic reviews does not significantly improve the result
Repeating the cycle 2-3 times in the same session

The whole process takes about 60-90 minutes and produces a colour improvement that is visible by the end of the session, to an extent that varies from person to person.

Supervised home whitening

This approach uses custom-made trays produced from a digital impression, with a low-concentration carbamide peroxide gel, within the EU limit of 6% released hydrogen peroxide. The patient wears the trays for 2-4 hours a day or overnight, for 2-4 weeks, under professional supervision.

Combined walking bleach technique

For root-treated teeth with internal discolouration, Dr Pljevljak uses the internal bleaching technique, placing a whitening agent directly inside the pulp chamber: traditionally a paste of sodium perborate and water, sealed inside the tooth. The method usually requires several sessions, with the whitening material replaced periodically until the desired result is achieved.

Factors that affect how well whitening works

The effectiveness of whitening depends on several variables:

Cause of the discolouration: external stains (coffee, smoking, tannins) respond better than internal ones (tetracyclines, fluorosis)
Enamel thickness and translucency: thin enamel allows deeper penetration but requires lower concentrations
Patient age: young teeth with wide dentinal tubules respond better

How long results last and what helps maintain them

Colour stability over time

Clinical studies indicate that after whitening the colour tends to fade partially, but teeth can remain lighter than at the start even 18 months later. How long results last varies from person to person and depends on:

Eating and drinking habits (consumption of staining foods and drinks)
Oral hygiene at home
The structural characteristics of the enamel
The maintenance protocols followed

Professional maintenance strategies

To make results last longer, Nea Bios follows a maintenance protocol that includes:

Six-monthly recalls with application of remineralising gels
Annual touch-ups with lower concentrations of peroxide
Professional polishing every three months to remove surface stains
Specific toothpastes containing biomimetic hydroxyapatite

Technological innovations in teeth whitening

Technological progress has introduced cutting-edge methods:

LED lamps: what the studies say

LED lamps are often promoted to activate the whitening gel. According to systematic reviews of the literature:

Light activation (LED, halogen or laser) generally does not improve the effectiveness of whitening
It does not reduce post-treatment sensitivity, which in some studies is actually higher
Evidence for newer forms of activation is still limited

Applied nanotechnology

Adding calcium phosphate nanoparticles to the whitening gel is being studied with the aim of:

Helping to remineralise the enamel during the treatment
Reducing dentine permeability and therefore sensitivity
So far, however, the proven benefits of calcium-based agents are limited and the evidence is of low certainty

Managing sensitivity and protecting the pulp

Tooth sensitivity is a common but usually temporary side effect, and is managed through:

Desensitising agents based on potassium nitrate, which reviews of the literature suggest can reduce its intensity
Application of neutral fluoride after whitening
Use of gels with a buffered pH close to neutral
Application of ACP (amorphous calcium phosphate) to seal the tubules

Dr Pljevljak, drawing on his PhD in Oral and Dental Diseases from Sapienza University, tailors each protocol to minimise side effects through a careful assessment before treatment.

Clinical indications and contraindications

Ideal candidates for treatment

Professional whitening is particularly suitable for:

Discolouration due to natural ageing
Mild to moderate fluorosis stains
External stains caused by diet
Preparation before prosthetic work, for colour matching

Limitations and contraindications

The treatment is not recommended in the case of:

Pregnancy and breastfeeding
Under 18 years of age
Severe tooth sensitivity
Decay or leaking fillings
Extensive gum recession with exposed roots
Large restorations on the front teeth (which cannot be whitened)

Medico-legal aspects and treatment safety

Professional teeth whitening, when carried out according to validated clinical protocols, has a favourable safety profile: the most common side effect, tooth sensitivity, is usually temporary. European legislation (Directive 2011/84/EU) sets a maximum of 6% hydrogen peroxide in tooth whitening products; products containing more than 0.1% may only be sold to dentists, the first application of each treatment cycle must be carried out by a dentist, and they must not be used on anyone under 18.

Dr Nihad Pljevljak, registered with the Rome Order of Physicians and Dentists (Ordine dei Medici Chirurghi e Odontoiatri di Roma), strictly follows international guidelines, documenting every stage of treatment and monitoring the vitality of the pulp with sensitivity tests.

To find out how the treatment works at our clinic, visit our page on professional teeth whitening; if you are considering over-the-counter products, read the dentist's answer on how to whiten your teeth at home.

Combining whitening with other cosmetic treatments

Whitening is often the first step in a complete smile makeover. At Nea Bios Dental Clinic, it is frequently combined with:

All-ceramic veneers to correct tooth shape
Invisible orthodontics to align the teeth before whitening
Gum contouring to optimise the balance between pink and white
Conservative restorations with nanofilled composites

To find out whether professional whitening is right for you and receive a personalised plan for your smile, contact the Nea Bios Dental Clinic reception. The team is available Monday to Friday from 9:00 to 13:00 and 14:00 to 18:00 to arrange a specialist consultation at Via Cesare Pavese 135, Rome EUR Laurentina.

Sources

Council of the European Union. Council Directive 2011/84/EU of 20 September 2011 amending Directive 76/768/EEC, concerning cosmetic products, for the purpose of adapting Annex III thereto to technical progress. Official Journal of the European Union. 2011;L 283:36-38. EUR-Lex
Hajeer O, Hasan A. In-office tooth bleaching protocols: an umbrella review of systematic reviews and meta-analyses on whitening efficacy and tooth sensitivity. Saudi Dent J. 2026;38(4):39. PubMed
Attin T, Paqué F, Ajam F, et al. Review of the current status of tooth whitening with the walking bleach technique. Int Endod J. 2003;36(5):313-329. PubMed
Auschill TM, Schneider-Del Savio T, Hellwig E, et al. Randomized clinical trial of the efficacy, tolerability, and long-term color stability of two bleaching techniques: 18-month follow-up. Quintessence Int. 2012;43(8):683-694. PubMed
Kurmanalina MA, Tankibayeva ZG, Sagimbayeva TB, et al. Interventions for bleaching-induced tooth sensitivity: an umbrella review. Front Oral Health. 2026;7:1927686. PubMed
Márton P, Antal M, Kiss-Dala S, et al. Enamel damage from tooth-whitening - a systematic review and meta-analysis. J Dent. 2026;172:106786. PubMed