Crown vs Filling: When You Need Each and What They Cost in the UK

There's a moment in the dental appointment that feels decisive. The dentist examines the tooth, studies the X-ray, and delivers one of two verdicts: "This needs a filling" or "This needs a crown." Two different treatments, two very different price points (£99-£250 versus £650), and for the patient sitting there, the reasoning behind the choice can feel opaque.

But the logic is elegant, once you see it. It comes down to a single question: how much healthy tooth is left?

A filling repairs a hole inside the tooth. A crown wraps around the entire tooth and holds it together. When there's plenty of tooth remaining and the damage is contained, a filling handles it beautifully. When the damage has gone far enough that the remaining tooth can't reliably hold itself together under chewing forces, a crown takes over. The threshold between them is where dentistry gets interesting.

The Structural Logic of Fillings

Think of a tooth as a small box. Four walls, a floor. The nerve lives underneath the floor, in the root system. Decay eats through the walls.

A filling works when the damage has breached one wall, maybe part of a second. The remaining walls and floor are intact enough to hold the tooth together. The dentist removes the decay, cleans the cavity, and fills it with composite resin (the tooth-coloured material that's become standard) or occasionally amalgam. The filling bonds into the hole, the tooth's shape is restored, and the remaining structure does what it's always done: bear the chewing load.

Cost: £99-£250 at UrgentCare Dental, depending on how many surfaces the cavity involves.

Here's the part that's worth appreciating: a well-placed filling in a tooth with good remaining structure is a remarkably effective repair. The composite bonds chemically to the enamel and dentine. The tooth functions normally. The repair is invisible. And it lasts 5-15 years, sometimes considerably longer.

But fillings exist inside a story that unfolds over decades. When a filling eventually wears out or new decay develops at its margins, the replacement filling is slightly larger (the old filling is removed along with any new decay, and the new filling fills the slightly bigger hole). Each replacement cycle takes a little more tooth with it. First replacement: the tooth is fine. Second replacement: still fine, but the walls are thinner. Third replacement: the walls are getting thin enough that the dentist pauses, studies the X-ray carefully, and starts thinking about a crown.

When the Crown Conversation Begins

A crown becomes the right answer when the remaining walls of the tooth are too thin to reliably support a filling under the forces of everyday chewing. And those forces are considerable: the average bite force on a molar is around 70kg. On a tooth with thin walls and a large filling, that's enough to split the tooth like a log.

Cost: £650 at UrgentCare Dental.

The crown fits over the entire visible portion of the tooth like a protective helmet. It holds the weakened walls together, distributes the chewing force evenly, and prevents the catastrophic fracture that would otherwise be a matter of time.

The scenarios that lead here are varied but they share a common thread: the tooth's own structure can no longer do the job alone.

Large cavities where three or four walls are compromised, and the remaining shell is too thin to trust with just a filling. Cracked teeth, where a fracture line runs through the structure and propagates a little further every time the tooth flexes: a crown binds the crack, stopping its progress. Teeth after root canal treatment, where the living core has been removed and an access hole drilled through the top: the tooth is structurally weakened on two fronts, and a crown restores what's been lost. Teeth with massive old fillings that occupy most of the tooth's volume, where the remaining walls are thin and undermined and the next fracture could split the tooth below the gum line: a crown before that happens is prevention at its most pragmatic.

And then there's the cosmetic use: teeth with severe discolouration, malformation, or damage that goes beyond what bonding or veneers can address. A crown rebuilds the entire visible surface.

The Grey Zone (Where It Gets Honest)

Some cases sit right on the boundary. The cavity is large but not enormous. Two walls are compromised but the remaining structure seems adequate. It could go either way.

This is where the dentist's experience becomes the deciding factor. How many teeth like this have they seen survive with a filling? How many have they seen break? The pattern recognition that comes from years of clinical work informs the recommendation in a way that the X-ray alone can't capture.

The honest conversation in this grey zone sounds like: "A filling will work here, and it might last years. But this tooth is at higher risk of fracture with a filling than it would be with a crown. If it fractures, the outcome could be extraction. A crown reduces that risk significantly."

Some dentists offer an onlay for these borderline cases: a partial crown that covers the biting surface and the weakened walls without wrapping the entire tooth. More protection than a filling, less tooth removal than a full crown. It's a precise middle ground, at a similar cost to a full crown.

The economics of the grey zone are worth noting. The difference between a large filling (£250) and a crown (£650) is £400. If the filling fails and the tooth fractures, the outcome might be extraction plus an implant (from £1,999). That £400 difference in the grey zone starts looking like very good insurance.

What Each Procedure Feels Like

A filling is a single appointment: 20-45 minutes, depending on the size. Local anaesthetic numbs the area. The decay is removed, the cavity is cleaned, and the composite is placed in layers, each one hardened with a blue light that's vaguely science-fiction in its intensity. The filling is sculpted to match the tooth's natural shape, polished, and done. The tooth works immediately. There might be some sensitivity to cold for a few days, which settles on its own.

A crown is usually two appointments. At the first, the tooth is prepared: shaped down to make room for the crown that will fit over it. An impression or digital scan captures the prepared tooth precisely, and a temporary crown is fitted to protect it. The impression goes to a dental laboratory, where the permanent crown is crafted from porcelain, zirconia, or a metal-ceramic combination. Skilled technicians build the crown to match the colour, shape, and translucency of the natural teeth around it. This takes one to two weeks.

At the second appointment, the temporary crown comes off, the permanent crown is tried in: the fit is checked, the bite is adjusted, the colour is confirmed against the neighbours. Then it's cemented permanently. The whole fitting takes about 30 minutes. The result is a tooth that looks, feels, and functions like the original.

The Long View

A filling is the beginning of a relationship with a tooth. It solves the immediate problem beautifully, and when it eventually needs replacing in 5-15 years, the replacement is straightforward. The tooth's story continues.

A crown is typically a later chapter in that story. It arrives when the filling chapters have run their course and the tooth needs more substantial protection. A crown lasts 10-25 years, often longer with good care. When it eventually needs replacing, the process is clean: remove the old crown, check the tooth underneath, take a new impression, place a new crown.

Both are excellent treatments for their respective situations. The dentist's recommendation isn't about upselling from the cheaper option to the more expensive one: it's about reading the structural story of the tooth and recommending what that story requires. A tooth that needs a filling gets a filling. A tooth that needs a crown gets a crown. The assessment at UrgentCare Dental examines the tooth, reviews the X-ray, and explains exactly what's happening and why.