What Are Cavity Fillings Made Of? Materials, Pros, and How to Choose
When your dentist treats a cavity, they remove the decay and replace it with a material that seals and strengthens the tooth. In Canada, the most common options are composite resin, amalgam, ceramic (porcelain), gold alloys, and glass ionomer. Each has unique advantages, costs, and best uses.
What are cavity fillings made of?
Cavity fillings are made from one of several materials: composite resin (plastic with fine glass), amalgam (mercury mixed with silver, tin, and copper), ceramic or porcelain, gold alloys, and glass ionomer (acrylic with glass powders that can release fluoride). Your dentist recommends a material based on tooth location, bite forces, budget, and appearance goals.
Composite resin (plastic + glass)
Composite is a tooth-coloured material made of plastic and tiny glass particles. It bonds to enamel, so your dentist often removes less healthy tooth structure. It’s popular for front teeth and small to medium cavities where appearance matters.
Pros
Natural look, conservative preparation (less drilling), bonds to tooth, immediate set with curing light, often repairable if chipped.
Cons
Can stain over time (coffee/tea/smoking), may wear faster than metal in large back-tooth fillings, and can be sensitive right after placement. Prices vary by clinic and province.
If you want a fuller overview of every common option, try this helpful guide to different types of dental fillings.
Amalgam (mercury + silver/tin/copper)
Amalgam is a silver-coloured metal mixture. It’s been used for over a century and is known for strength and long life, especially under heavy chewing forces in molars.
Pros
Very durable, strong for large back-tooth cavities, and generally budget-friendly.
Cons
Metal colour is noticeable, it doesn’t bond to enamel (so more tooth removal may be needed to lock it in place), and it can conduct temperature, leading to brief hot/cold sensitivity.
“Dental amalgam is a safe, durable and effective restorative material for dental fillings.” — American Dental Association, Council on Scientific Affairs
For a direct head-to-head comparison of the two most common choices, see composite vs amalgam fillings.
Ceramic (porcelain) fillings and inlays/onlays
Ceramic fillings are often porcelain. They’re tooth-coloured and resist staining better than composite. They’re typically made by a lab or with in-office CAD/CAM (computer-aided) systems and bonded into the tooth as an inlay or onlay.
Pros
Excellent appearance, strong and wear-resistant, and less likely to stain than composite.
Cons
Higher cost than composite and amalgam, may require removing a bit more tooth for proper fit, and can be brittle without proper design and bonding.
Gold alloy fillings
Gold fillings (usually a gold alloy) are extremely durable and well-tolerated by gums. They’re placed as inlays/onlays made in a lab, then cemented in a second visit.
Pros
Top-tier longevity (often decades), gentle on opposing teeth, and does not corrode.
Cons
Premium cost, multi-visit process, and a visible metallic look that some people don’t prefer.
Glass ionomer (acrylic + glass powders)
Glass ionomer releases fluoride over time, which can help protect against new decay. Dentists often use it for non-biting areas, small cavities, temporary fillings, or in children where moisture control is difficult.
Pros
Fluoride release helps prevent future decay, bonds to enamel and dentin, and is useful where isolation is tricky.
Cons
Lower strength and wear resistance than composite or porcelain, not ideal for heavy chewing areas, and less glossy appearance.
What’s new in fillings?
Modern dentistry continues to improve bonding agents, light-curing, and bioactive materials that may support remineralization (adding minerals back into the tooth surface). Some dentists also use lasers to remove decay (a gentler sound and feel for some patients). Curious about what’s next? Explore new methods of tooth filling to see how materials and techniques keep evolving.
How to choose the right filling material
Your dentist weighs several factors and will discuss options with you:
1) Tooth location and size of the cavity
Front teeth and small fillings often favour composite or ceramic for a seamless look. Large molar fillings may lean toward amalgam, ceramic, or gold for strength.
2) Bite forces and habits
If you grind or clench (bruxism), a stronger material (ceramic, gold, or a carefully placed composite with a night guard) may last longer.
3) Appearance goals
Composite or ceramic best match tooth colour. Gold is visible but extremely durable; amalgam is silver and noticeable.
4) Budget and insurance
Costs vary by clinic and province. Some Canadian plans cover certain materials differently for back vs front teeth. Your dentist can help you understand choices within your coverage.
5) Moisture control and access
Composite and ceramic work best in a dry field. If moisture is hard to control (e.g., deep or hard-to-reach areas), your dentist may suggest alternatives like glass ionomer or amalgam.
6) Medical history and sensitivities
Discuss allergies, pregnancy, and any concerns about metals or BPA. Your dentist will recommend safe options for you.
Pros and cons at a glance
• Composite: natural look, conservative prep; can stain and wear faster under heavy chewing.
• Amalgam: long-lasting and strong; silver colour and more tooth removal to retain the filling.
• Ceramic: highly aesthetic and stain-resistant; higher cost and careful technique needed.
• Gold: most durable; visible colour and highest cost.
• Glass ionomer: fluoride release and good bond; lower strength for heavy bite areas.
What to expect during a filling visit
Most fillings are done in one visit. You’ll get local anesthesia to numb the area. The dentist removes decay, prepares the tooth, places the material, and shapes your bite. Composite is light-cured to harden immediately. Ceramic and gold restorations usually require scans or impressions, then a second visit to cement the final piece.
Aftercare: sensitivity, biting, and longevity
Mild sensitivity to cold or pressure can happen for a few days. Avoid chewing on numb cheeks or tongue, and follow your dentist’s chewing advice, especially after amalgam, which hardens fully over a few hours. Good brushing with fluoride toothpaste, daily flossing, and routine checkups help any filling last longer.
Conclusion
There’s no single “best” filling for everyone. Composite, amalgam, ceramic, gold, and glass ionomer each shine in different situations. The right choice depends on where the cavity is, how hard you bite, your budget, and how you want your smile to look. A quick chat with your Canadian dentist can match the material to your needs—and keep the tooth strong for years.
FAQ
How long do cavity fillings last?
It varies by material and your oral habits. Composite often lasts 5–10 years, amalgam 10–15 years (or more), ceramic 10–15 years, and gold can last decades. Night guards, good hygiene, and regular cleanings help extend lifespan.
Do cavity fillings hurt?
Most patients feel only pressure or vibration. Dentists numb the area with local anesthesia, so you should be comfortable. Some temporary sensitivity after treatment is normal and usually fades within a few days.
Can fillings fall out?
Yes, fillings can loosen from wear, new decay under the filling, or bite stress (like grinding). If one chips or comes out, keep the area clean and see your dentist as soon as possible to prevent more damage.
Are mercury (amalgam) fillings safe?
Major dental organizations (including the ADA and many national dental bodies) state amalgam is safe for most people. If you have specific concerns, allergies, or preferences, discuss alternatives with your dentist to choose what’s right for you.
When can I eat after a filling?
Composite hardens right away under the curing light, so you can usually eat once the numbness wears off. Amalgam takes a few hours to fully set; avoid hard chewing on that side until your dentist’s recommended time.
Which filling is best for children?
It depends on the tooth and the child’s needs. Glass ionomer is helpful in some cases because it releases fluoride, but composite is common for front teeth. Your dentist will suggest the safest, most practical option for your child.
