How to Choose Between a Filling, Inlay, Onlay, or Crown
Prosthodontics

How to Choose Between a Filling, Inlay, Onlay, or Crown

"This tooth needs a filling, while the other tooth is deeply decayed and needs an inlay." The patient looked at me in confusion and asked, "What's the difference between the two?"

"This tooth needs a filling, while the other tooth is deeply decayed and needs an inlay." The patient looked at me in confusion and asked, "What's the difference between the two?"

When do you need a dental filling?

Relatively shallow tooth decay can be handled by manual filling. After removing the decayed part of the tooth, different materials can be used to fill the tooth cavity. The choice of filling materials varies according to the location and size of the cavity, doctor's advice and patient's preference.
 

When is an inlay needed?

Once the doctor assesses that the tooth decay is relatively deep, or the position is difficult to repair by manual filling, he may suggest considering inlays to restore the teeth. Routine cases are handled by the general dental team at Home Dental Centre, with appointments arranged according to the dentists on duty. If clinical assessment indicates another area of care, the centre will arrange a further assessment with the appropriate dentist, and dentists from different areas can jointly develop a combined treatment plan.

Removing cavities is the first step in the treatment. However, compared with manual fillings, inlay restoration requires a dentist to take an impression or a three-dimensional scan of the patient, and to subsequently make the inlay in a laboratory. As for the choice of inlay material, it is usually ceramic, or other alloys, which are closest to the color of the teeth.

It can be imagined that the inlay is like one of the three-dimensional puzzle pieces inlaid into the missing part of the tooth. Because inlay is tailor-made, it has a high degree of fit with the tooth, and the material is stronger than that of human fillings, so it is more suitable for some deeply decayed teeth, teeth that have lost filling materials many times, or areas with a large chipping area.

existing old filling with leakage replaced with inlay before and after treatment

Comparison of a tooth with a leaked old filling on the left side and a tooth with a new dental inlay for better marginal fit and higher strength on the right side.

When is an onlay needed?

If the extent of tooth decay or tooth damage involves the occlusal area that mainly bears the force, then the crown cap (Onlay) is a better choice. Its principle and material selection are similar to those of inlays, and the difference is that the crown cap covers more teeth.

fractured filling replaced with onlay before and after photo

Comparison of a fractured and dislodged old filling with a weakening tooth on the left side, and an onlay treatment providing cuspal protection to prevent further fracturing on the right side.

When do you need Crown?

If inlays and crown caps are like three-dimensional puzzles, then the crown is like a helmet, which firmly covers the teeth that need to be protected, especially if the teeth to be protected have a large degree of decay/abrasion/chipping, or have cracked condition. In addition, if the tooth has undergone root canal treatment, then it is generally recommended to have a crown to better protect it.

Left photo shows an unfit and unaesthetic crown causing bacteria trap, dental caries, and gum problems. Right photo shows a new crown providing a more aesthetic and healthy long-term conditio

Left photo shows an unfit and unaesthetic crown causing bacteria trap, dental caries, and gum problems. Right photo shows a new crown providing a more aesthetic and healthy long-term condition

There are three main types of crowns, including:

-    metal crown

-    porcelain fused to metal crown

-    full-ceramic crown

Image showing three types of dental crowns with different designs and materials for various advantages and case scenarios: the left crown is a gold crown, the middle crown is a cerametal crown with metal underneath and porcelain added, and the right crown is a pure porcelain crown

Image showing three types of dental crowns with different designs and materials for various advantages and case scenarios: the left crown is a gold crown, the middle crown is a cerametal crown with metal underneath and porcelain added, and the right crown is a pure porcelain crown.

Unlike inlay or onlay, teeth need to be ground down to make room for the crown, and the subsequent impressions or scans, but the installation process of the trial dental mold are not very different.

Weigh the pros and cons, make a choice

Dentists often need to determine which treatment plan is suitable for a patient through clinical examination. Often a dentist will offer more than one option. Patients can weigh the pros and cons of various options and choose the one that best suits them. If you have any questions, please consult your trusted family dentist.

Article Info

First published: 28 February 2022

Last reviewed: August 2026

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FAQ

Frequently Asked Questions

  • How do I know whether I need a filling, inlay, onlay or crown?

    The choice depends on how much tooth structure remains and where the damage is. Shallow decay usually needs a filling. Deeper decay or large cavities may require an inlay. If the biting surface is involved, an onlay offers better protection. Teeth with very extensive damage, cracks, or root canal treatment typically need a crown. Your dentist will assess your tooth clinically and recommend the most suitable option.

  • What's the main difference between an inlay and a filling?

    A filling is shaped by hand directly in your mouth during one visit. An inlay is custom-made in a laboratory from a scan or impression of your tooth, so it requires two appointments. Inlays offer a more precise fit and use stronger materials like ceramic, making them better for larger cavities or teeth that have lost fillings repeatedly.

  • How much does a dental crown cost?

    Crown costs start from HK$6,500 per tooth, depending on the material chosen—metal, porcelain-fused-to-metal, or full ceramic—and the complexity of your case. We provide a personalised quote after examining your tooth and discussing your preferences. Marginal fit determines longevity — a poor fit traps bacteria, causing decay at the margins or pressure sores, and may require remakes. After a clinical assessment we explain the fee components clearly, and treatment starts only with your consent. WhatsApp us to arrange a consultation and get an accurate estimate.

  • How long does it take to get an inlay or onlay fitted?

    The process typically requires two visits. At the first appointment, we remove decay and take an impression or digital scan. The inlay or onlay is then made in a laboratory, which usually takes one to two weeks. You return for the second visit to have it bonded permanently onto your tooth.

  • Will I need a crown after root canal treatment?

    In most cases, yes. Root canal treatment removes the nerve and blood supply, leaving the tooth more brittle and prone to fracture. A crown acts like a protective helmet, covering and strengthening the tooth so it can withstand normal chewing forces. Your dentist will confirm whether a crown is necessary based on how much tooth structure remains.

  • Are there any risks with getting a crown?

    Crowns are generally safe when fitted by a qualified dentist. However, the tooth must be shaped down to make room for the crown, which is irreversible. Occasionally, sensitivity or discomfort can occur if the fit isn't perfect or if decay develops underneath. Regular checkups help catch any issues early. We recommend discussing your specific concerns during a consultation.

  • Can an old filling be replaced with an inlay?

    Yes, if an old filling has leaked, fractured, or no longer fits well, replacing it with an inlay can provide a stronger, longer-lasting restoration. Inlays are custom-made for a precise fit and use durable materials like ceramic, which helps prevent further decay and reduces the chance of repeated failures. Your dentist will assess whether an inlay is the best option for your tooth.

Still wondering about something? Our team is happy to chat.

Reminder: You have the right to choose a Hong Kong dentist based on your individual needs. We recommend referring to the list of registered dentists published on the official website of the Dental Council of Hong Kong to make a choice best suited to your personal needs. The above content is intended to give you a brief introduction to the nature and effects of the relevant dental procedures, so that you can make informed decisions when choosing a dentist and related treatment options. All treatments have advantages and disadvantages — the key is that you must have a basic understanding of different treatments and procedures and be aware of the associated risks. The above content does not represent the professional opinion or views of any dentist or dental institution. For the sake of your health, please consult your family dentist for formal medical advice.

This article is compiled by the Public Education Team of Home Dental and has been reviewed and approved by the Content Review Committee of Home Dental. The Committee comprises members of our Board of Directors, legal advisors, and relevant professionals, and is responsible for vetting all externally published health education content to ensure it is professional, accurate, relevant to the local context, and regularly updated to meet Hong Kong dental service standards.

This content is originally produced by Home Dental, all rights reserved. Unauthorized reproduction, modification, or publication is prohibited. Violators will bear legal responsibility. For citation or partnership inquiries, please contact our center for written permission.

Last updated: Aug 2026

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