Inlays, Onlays, or Crowns: How to Choose the Right Restoration for Your Tooth

Yesterday, a patient sat in my Henderson office holding an estimate from another dentist. The paper listed three treatment options for a cracked molar: an inlay at $800, an onlay at $1,200, or a crown at $1,400. She looked at me and asked the question I hear constantly: “Which one do I actually need? And what’s the difference?”

I pulled up her x-ray and showed her the crack extending from the chewing surface toward the tooth’s cusp – the pointed peak on top. “Here’s how I think about it,” I told her. “A filling patches a hole. Inlays fill larger areas of damage between the cusps of a tooth. Onlays cover one or more cusps. A crown covers the entire tooth above the gum line.

She nodded, but I could see she still wasn’t sure which one made sense for her situation – and how to weigh the cost difference against the coverage difference.

If you’re facing a similar decision, this article will help you understand what you’re actually choosing between. After 20+ years placing these restorations in Las Vegas and Henderson, I can tell you that the “best” option isn’t always the most expensive one – it depends on how much tooth structure you still have, where the damage is located, and what your tooth needs to function long-term.

Understanding What Each Restoration Actually Does

Let me start with the basics, because the terminology confuses people.

Inlays fit within the cusps of your tooth – those are the pointed peaks on the chewing surface. Think of an inlay as a custom-made filling that’s fabricated in a lab rather than placed directly in your mouth. Dentists use inlays when decay or damage is too large for a regular filling but hasn’t reached the outer edges of the tooth.

Onlays (sometimes called partial crowns) cover one or more cusps plus the area between them. They’re larger than inlays because they extend over the tooth’s peaks. Onlays work when damage extends to or weakens the cusps, but the sides of the tooth remain mostly intact.

Crowns cover the entire visible portion of the tooth above the gum line – top, sides, everything. They’re necessary when the tooth is so damaged or weakened that partial coverage won’t provide adequate strength.

All three are indirect restorations, meaning they’re custom-made outside your mouth (usually in a dental lab or using in-office CAD/CAM technology) and then bonded or cemented to your tooth. This is different from fillings, which are placed directly.

How Much Tooth Structure Gets Removed

This is the critical difference that affects long-term outcomes.

For inlays and onlays, I remove only the damaged or decayed portion of the tooth. The healthy tooth structure stays. This conservative approach preserves your natural tooth, which is always preferable when possible. Recent dental literature emphasizes that preserving tooth structure leads to better long-term prognosis, following conservative dentistry principles recommended by leading dental organizations.

For crowns, I need to reduce the entire tooth – top and sides – to create space for the crown to fit over it. Research shows that traditional crown preparation removes approximately 63-73% of the tooth structure. Even the most conservative crown prep takes away significantly more healthy tooth than an inlay or onlay.

Why does this matter? Every time you remove tooth structure, you weaken what remains. Your natural tooth is almost always stronger than any restoration. The less I have to remove, the better your long-term outcome.

That said, sometimes removing more structure and placing a crown is necessary because the tooth is already so compromised that partial coverage won’t protect it adequately.

When Each Restoration Makes Sense

Here’s how I decide which restoration to recommend:

Choose an Inlay When:

• Decay is contained between the cusps – The damage hasn’t reached the tooth’s outer edges
• The cusps are still strong – No cracks extending into the peaks of the tooth
• You need more than a filling can provide – The cavity is too large for composite to last, but not large enough to require cusp coverage

Choose an Onlay When:

• One or more cusps are damaged or weakened – Cracks, fractures, or extensive wear affecting the peaks
• You have a large old filling that’s failing – Especially if the filling has weakened the surrounding tooth structure
• The tooth has had a root canal – But retains enough structure that a full crown isn’t necessary
• You’re trying to prevent future cuspal fracture – The tooth shows early signs of stress but hasn’t broken yet

Choose a Crown When:

• Multiple cusps are damaged or missing – The tooth lacks structural integrity
• The tooth has extensive decay reaching the sides – Not just the top surface
• Following root canal treatment on molars – These teeth are particularly prone to fracture without full coverage
• You’re restoring a tooth with an existing large filling – Where so little natural tooth remains that anything less than a crown won’t provide adequate protection
• Severe wear or grinding has shortened the tooth significantly – The tooth needs both protection and height restoration

In my Henderson and Las Vegas practices, I see a common pattern: patients who delay treatment end up needing more extensive restorations. A tooth that could have been saved with an onlay three years ago now needs a crown – or worse, extraction and a dental implant.

Materials: What They’re Made From

Inlays, onlays, and crowns can all be made from similar materials:

Porcelain (Ceramic) – The most popular choice for all three because it matches your natural tooth color perfectly. Modern ceramics like lithium disilicate are extremely strong and aesthetically excellent. This is what I use for most patients.

Gold – Exceptionally durable and gentle on opposing teeth. Some patients prefer gold for back molars where aesthetics matter less. Gold restorations often last 20+ years with proper care.

Composite Resin – Less expensive but also less durable than ceramic. Sometimes used for inlays and onlays, though I generally recommend ceramic for longevity.

Porcelain Fused to Metal (PFM) – A metal base with porcelain on top, typically used for crowns. Strong, but the metal can show as a dark line at the gum line over time. I rarely recommend these anymore given the strength of modern all-ceramic options.

How Long Do They Last?

Recent research provides good data on longevity:

5-Year Survival Rates:

• Inlays: 91% survival rate
• Onlays: 93-94% survival rate
• Crowns: 95% survival rate

10-Year Survival Rates:

• Ceramic inlays/onlays: approximately 85-91% survival
• Crowns: similar rates when properly placed

2024 studies show excellent long-term performance for all three options. One study following ceramic onlays for up to 24.8 years found survival rates of 71-98.5%, with proper maintenance being the key factor.

What causes failure? The most common reasons are:

• Fracture – The restoration itself breaks, most common with ceramic
• Secondary decay – New cavities form under or around the restoration
• Loss of retention – The restoration debonds from the tooth
• Tooth fracture – The natural tooth under the restoration cracks

Good oral hygiene, regular dental cleanings, and avoiding excessive grinding dramatically improve longevity for all three restoration types.

The Cost Difference – And What It Means

In the Las Vegas and Henderson area, typical costs are:

• Inlays: $650-$1,200 per tooth
• Onlays: $800-$1,400 per tooth
• Crowns: $1,000-$3,000 per tooth (depending on material)

Most dental insurance covers 50% of these restorations after your deductible, categorizing them as major restorative work. Coverage specifics vary by plan, so verify benefits before treatment.

Here’s my honest take on cost: choosing a less expensive restoration when you need more coverage is false economy. If your tooth needs an onlay but you opt for an inlay to save $300, you risk the tooth fracturing within a year – then you’re paying for an extraction and implant ($4,000-6,000 total). Or if your tooth genuinely needs a crown but you choose an onlay, the restoration may fail prematurely.

Conversely, choosing a crown when an onlay would work means removing extra tooth structure unnecessarily and paying more for coverage you don’t need.

The goal is the restoration that matches your tooth’s actual condition – not the cheapest option or the most expensive one.

The Treatment Process

The procedure is similar for all three:

First Visit (About 1-2 hours):

• I numb the area and remove any decay or damaged tooth structure
• For crowns, I reduce the entire tooth to create space. For inlays/onlays, I remove only damaged portions
• I take impressions (or digital scans) of the prepared tooth
• I place a temporary restoration to protect the tooth
• The lab fabricates your custom restoration (typically takes 1-2 weeks)

Second Visit (About 1 hour):

• I remove the temporary restoration
• I check the fit of your permanent restoration
• Once we’re both satisfied with the fit and appearance, I bond or cement it permanently

Some practices now offer same-day restorations using CAD/CAM technology – the restoration is designed and milled in-office during a single appointment. At Comprehensive Dental Care, we provide both options depending on your preference and schedule.

Questions to Ask Your Dentist

When your dentist recommends a specific restoration, ask:

• “Can you show me on the x-ray why you’re recommending this option?”
• “Would a more conservative restoration work, or would that risk failure?”
• “What happens if I choose the less extensive option?”
• “What material do you recommend and why?”
• “What’s the expected longevity given my specific situation?”
• “Do I grind my teeth at night? Will that affect which restoration I should choose?”

A good dentist will explain their reasoning and show you exactly what they see. If I’m recommending a crown over an onlay, I want you to understand why the additional coverage is necessary for your specific tooth.

Making Your Decision

Here’s what I tell patients when they’re trying to decide:

Trust the assessment of structural damage – Your dentist can see (via x-rays and clinical examination) how much healthy tooth structure remains. This dictates which restoration will actually protect your tooth long-term.

Consider your bite forces – If you grind your teeth or have a heavy bite, you may need more coverage than someone with lighter forces. We can evaluate this and factor it into the recommendation.

Think long-term – A restoration that costs $300 less but fails in 3 years because it didn’t provide adequate coverage ends up costing far more in the long run.

Ask about alternatives – Sometimes there’s genuinely a choice between two options. Other times, only one restoration will adequately protect your tooth. Understanding which situation you’re in helps you make an informed decision.

That patient with the cracked molar? After discussing her situation, we agreed an onlay made the most sense. The crack extended into one cusp, so an inlay wouldn’t have protected against further fracture. But enough tooth structure remained that a full crown wasn’t necessary. Three years later, that onlay is functioning perfectly – no cracks, no problems.

What We Do at Comprehensive Dental Care

At our Henderson and Las Vegas offices, we use digital imaging and careful examination to determine exactly how much tooth structure remains and which restoration will provide adequate protection without removing unnecessary healthy tooth.

We explain the reasoning behind our recommendations and show you what we see on x-rays. We discuss material options, expected longevity, and costs upfront. And if you’re choosing between two legitimate options, we help you understand the tradeoffs.

Most importantly, we prioritize preserving your natural tooth structure whenever possible – while ensuring the restoration we place will actually protect your tooth long-term.

If you’ve been told you need a crown, inlay, or onlay and want a second opinion or clearer explanation of why, call our office. We’ll evaluate your tooth, explain what we see, and help you make an informed decision about your care.