Fillings for Front Teeth: Class III and Class IV Repairs

In brief: Class III fillings repair decay on the sides of front teeth, between the incisors and canines, without touching the biting edge. Class IV fillings rebuild a front tooth when the damage includes a corner or the incisal (biting) edge, usually after a chip, a fracture or larger decay. Both are normally done in one visit with layered, shade-matched composite; a veneer or crown is the better choice when much of the tooth is lost or discoloured.

Class III and Class IV: what the difference is

Dentists classify cavities by position, following the system set out by G.V. Black. Front teeth (incisors and canines) have two classes of their own.

A Class III cavity sits on a proximal surface of a front tooth: the side that touches the neighbouring tooth. The incisal edge and corner are still intact. These cavities start where plaque collects below the contact point, so they are often missed by brushing and spotted at a check-up as a grey shadow between two teeth.

A Class IV restoration involves a proximal surface plus the incisal angle, the corner of the biting edge. It is needed when Class III decay has grown large enough to undermine the corner, or when trauma has broken off part of the edge. Because it rebuilds a visible corner that also takes biting force, it is the more demanding of the two.

Common causes and signs

• Decay between front teeth: a grey or brown shadow seen through the enamel, a rough spot your tongue can feel, or floss catching at one contact. Small cavities often cause no symptoms.
• Trauma: a fall, a sports knock or biting something hard can chip a corner. Sharp edges can cut the lip or tongue.
• Old fillings: a front filling that has darkened, stained at its edges or chipped is often replaced as a Class III or IV restoration.
• Wear: grinding or an edge-to-edge bite can thin and chip the incisal edges over time.

After a knock to a front tooth, see a dentist even if only a small piece has broken. The nerve can be bruised by the impact, and an X-ray helps check the root and the pulp. If you find the broken fragment, keep it moist in milk or saliva and bring it with you, as it can sometimes be bonded back.

When a Class IV filling is the right choice

A Class IV composite is usually advised in four situations:

• A broken corner after trauma: a chip or fracture through the incisal angle, once an X-ray shows the root and nerve are healthy.
• Decay that has undermined the corner: a Class III cavity that has grown until the corner enamel has no dentine support left.
• Chipping from grinding or bite problems: a single corner that has cracked or broken off. The cause needs managing too, or the repair will chip again.
• A failed old corner filling: one that has stained, chipped or leaks at its edges.

If several front teeth are worn or discoloured, or the break is large, a veneer or crown may serve better (see below). Dazzle places mercury-free fillings only, so front-tooth repairs are done in tooth-coloured composite.

Matching shade and shape

A front filling has to match the tooth in colour, translucency and surface texture, or it will show in daylight. Natural teeth are not one colour: the body (dentine) is more opaque and warmer, while the edge is thinner, more translucent and often slightly bluish.

Shade is chosen before the tooth dries out, because a dry tooth looks lighter than it really is. Your dentist compares shade tabs or places small test samples of composite on the tooth, sets them and checks them in natural light. A filling that is the right colour but too opaque looks flat and obvious, so translucency matters as much as shade.

Shape counts too. The new surface is contoured to match the outline, the curve and the light-reflecting ridges of the tooth on the other side, then polished to a gloss similar to enamel. Well-polished composite also picks up less stain and plaque.

How the filling is placed

Most Class III and Class IV fillings are completed in a single appointment of about an hour per tooth, depending on size.

1. Examination. The tooth is checked visually and, where needed, with an X-ray to see how deep the decay or fracture goes.
2. Anaesthetic if needed. Decay removal is done with local anaesthetic. A small chip with no decay can sometimes be repaired without it.
3. Preparation. Only decayed or weakened tooth is removed. For a chip, the broken edge is smoothed and a short bevel is added on the enamel so the join blends in.
4. Isolation and bonding. The tooth is kept dry, etched and coated with a bonding agent. Neighbouring teeth are protected with a thin strip.
5. Layering. For a Class IV, a thin back wall is often built first, guided by a silicone key made from a mock-up or a scan. Dentine shades go in next to create depth, then a final enamel layer on the front. Each layer is set with a curing light.
6. Finishing. The bite is checked, including sliding the lower jaw forward, then the surface is shaped and polished in stages with fine discs and cups.

Filling, veneer or crown?

A filling is the most conservative option because it replaces only what is missing. It is usually the right first choice for a cavity between front teeth, a small to moderate chipped corner, or a stained old filling in an otherwise healthy tooth. It costs less than a veneer and can be repaired or added to later.

A veneer covers the whole front surface of the tooth. It may be the better choice when:

• the tooth already has several fillings, so it looks patchy
• there is deep discolouration (for example from fluorosis or tetracycline) that whitening and a filling cannot hide
• you also want to change the shape, length or small gaps across several front teeth, often as part of a smile makeover
• the edges are worn along their full width rather than at one corner

Porcelain veneers resist staining and keep their gloss longer than composite, but most need some enamel removed and take two or more visits. Composite veneers are an in-between option. Our comparison of veneers and composite bonding covers the trade-offs in more detail.

A crown is usually advised when so much tooth is lost that a large filling would be fragile, when the tooth has had root canal treatment and is weakened, or when a fracture runs deep. Crowns for front teeth are typically all-ceramic; see ceramic and zirconia crowns. Your dentist will weigh how much healthy tooth remains, your bite and grinding habits, and the look you want.

Caring for front-tooth fillings

• Brush twice a day with fluoride toothpaste and clean between the front teeth daily with floss, since Class III cavities start at the contact.
• Do not bite directly into very hard foods, nails, pens or thread with a restored corner. Cut apples and similar foods into pieces.
• Composite can pick up stain from tea, coffee, red wine, tobacco and turmeric-rich food over time. Rinsing with water afterwards helps, and a professional polish can lift surface stain.
• If you grind your teeth, a custom night guard protects the edges from chipping.
• Wear a sports mouthguard for contact sports.
• Keep regular check-ups so the edges of the filling can be checked and polished.

Front composite fillings commonly last five to ten years; Class IV fillings sit at the lower end because they take biting force at the corner. Small chips can usually be repaired without replacing the whole filling.

For cavities in back teeth (molars and premolars) see our guide to fillings for back teeth. To learn more about tooth-coloured repairs for chips and gaps, see tooth bonding.

Chipped a front tooth or noticed a shadow between your teeth? Book a Consult at our Bandra West or Kemps Corner clinic.