Tooth discolouration is one of the most common cosmetic concerns patients raise — and one where there's a lot of confusion about what actually works. Not all yellowing is the same, not all whitening is effective on every type, and the difference between a result that lasts and one that disappoints often comes down to identifying the cause first.

Here's how to read what your teeth are telling you, and what treatment can realistically achieve.

Why Teeth Discolour

Tooth colour is determined by two layers: the outer enamel, which is naturally off-white, and the inner dentine, which is naturally yellow. As enamel thins with age or stains accumulate on its surface, the dentine shows through more prominently — and teeth look yellower.

Discolouration falls into two categories that respond very differently to treatment.

Extrinsic staining — on the surface

Surface stains are the most common cause of yellowing and the most responsive to whitening. They build up from contact with staining substances over time:

• Coffee and tea — tannins bind to enamel and deposit a yellow-brown film
• Red wine — both tannins and chromogens adhere to enamel surfaces
• Tobacco — nicotine and tar staining is among the most stubborn and hardest to shift at home
• Dark sauces, berries, and coloured foods — regular exposure builds up gradually
• Plaque and tartar — when left to accumulate, they create a yellow coating that brushing can't remove once hardened

Intrinsic discolouration — within the tooth

This originates inside the tooth structure and doesn't respond to surface whitening. Common causes include:

• Ageing — enamel thins naturally over decades, making the yellow dentine beneath progressively more visible
• Childhood antibiotic use — certain antibiotics taken during tooth development can cause grey-brown banding within the tooth structure
• Fluorosis — excessive fluoride during enamel development causes white spots or brownish patches
• Trauma — a knocked or damaged tooth can darken as the internal tissue responds to injury
• Root canal-treated teeth — teeth that have had root canal treatment sometimes darken over time as the internal tissue breaks down

Genetics

Baseline tooth colour is partly genetic. Some people have naturally thinner enamel or more yellow dentine — not a reflection of hygiene, and something whitening can improve but not fully eliminate.

Reading the Pattern

The location and distribution of discolouration points toward the cause:

• Uniform yellowing across all teeth, worsening gradually — typically enamel thinning and dentine visibility increasing with age
• Staining concentrated near the gumline — often hardened tartar; a professional clean is the starting point before considering whitening
• One tooth noticeably darker than the rest — may indicate trauma or a root canal-treated tooth that has darkened internally
• Staining that varies with diet and lifestyle — extrinsic staining, the most straightforward to treat

What Helps at Home

Home care slows the rate of staining and maintains professional results — it won't reverse significant yellowing on its own.

Whitening toothpaste

Works through mild abrasives and, in some formulations, low-concentration peroxide or blue covarine — an optical pigment that creates a whitening effect. Reduces surface staining with consistent use but doesn't alter the underlying tooth colour.

Brushing timing

Brushing within 30 minutes of consuming staining food or drinks reduces pigment absorption before it sets. Rinsing with water immediately after is also effective.

Avoid brushing immediately after acidic food or drink — enamel is temporarily softened and more vulnerable to abrasion.

Reducing staining habits

The main causes of extrinsic staining are tobacco, red wine, tea, and coffee. Reducing frequency has more impact than quantity. Using a straw for cold drinks limits tooth-surface contact.

Regular professional cleans

Hardened tartar and surface staining that brushing can't shift is removed during a scale and clean. For patients with significant surface staining, a professional clean before whitening treatment clears the surface layer and allows bleaching to work directly on the enamel.

Professional Whitening at Prahran Family Dental

At Prahran Family Dental, we offer three whitening options depending on the type and cause of discolouration, your timeline, and personal preference.

Take-home whitening

Custom whitening trays are fabricated from impressions of your teeth. The trays evenly distribute whitening gel across the tooth surfaces and minimise contact with the gum tissue.

Worn for a prescribed period each day over two or more weeks, the treatment produces gradual, controlled results. The custom trays can be reused for top-up treatments in future.

In-chair whitening — SDI Pola

Completed in approximately one hour at the practice. Your dentist applies a professional whitening gel and activates it with a light to brighten your teeth during a single appointment.

This is the most time-efficient option for patients wanting immediate results. Dr Jun oversees the process for managing sensitivity and ensuring even application.

Internal whitening

Regular external whitening is ineffective for teeth that have darkened from within, as this discolouration occurs inside the tooth structure.

Internal whitening involves placing whitening material inside the tooth over a series of visits, gradually restoring the natural colour before sealing the access point with a filling. It's a specialised procedure for a specific type of discolouration.

Worth noting across all options: teeth whitening doesn't alter the colour of existing restorations — crowns, veneers, bonding, and fillings remain their original shade. If you have visible restorations near the front teeth, they are factored into the treatment plan before treatment starts.

Frequently Asked Questions

Does professional whitening damage enamel?

Professional whitening, when carried out as directed, doesn't damage enamel. The bleaching agents temporarily open the enamel's pores to break down staining compounds, after which the enamel remineralises. Sensitivity during or after treatment is common but temporary and settles within a few days.

Why are my teeth yellow even though I brush regularly?

Brushing removes plaque but doesn't address intrinsic discolouration, hardened tartar, or staining from ageing and diet. The cause determines what will work — a professional assessment identifies whether a clean, whitening, or a different approach is the right starting point.

How long do whitening results last?

Typically one to three years, depending on diet and habits. Coffee, tea, red wine, and tobacco accelerate re-staining. Top-up treatments using existing custom trays refresh results without repeating the full process.

Can all yellow teeth be whitened?

Not all discolouration responds to bleaching. Extrinsic staining and age-related yellowing respond well to treatment. Fluorosis, discolouration from childhood antibiotic use, trauma-related darkening, and root canal-related darkening are more resistant to standard whitening — though internal whitening addresses the last of these. Veneers or bonding may be appropriate for cases that don't respond to bleaching.

Is over-the-counter whitening worth trying?

For mild surface staining, it's a reasonable starting point. OTC strips and gels contain lower concentrations than professional products and produce more limited results. They won't address intrinsic discolouration or match the outcome of a professionally supervised treatment.

Teeth Whitening in Prahran

If you're unsure what's causing your teeth to discolour or want to find out which whitening option suits your situation, a consultation with Dr Jun is a good starting point. At Prahran Family Dental, we see patients from across the area — including Windsor, South Yarra, Toorak, and Armadale — and our focus is always on providing you with clear information so you can make an informed decision.

Call us on (03) 9533 2288 or book online. Visit us at Shop 7, 180 Commercial Road in Prahran.