There’s a specific scenario that seems to repeat itself in almost all our dental clinics. A patient walks in, needing a restoration for a posterior tooth, and as soon as you glance inside their mouth, the battle scars are unmistakably clear: severe wear facets on most teeth, craze lines, and perhaps even old fractures. The diagnosis is quite evident: this patient has bruxism, meaning they clench or grind their teeth with significant force, especially at night.
The real challenge often begins when the patient tells you, “But doctor, I want a white, aesthetically pleasing restoration.” This is where the dilemma truly starts. Do you place an E-max restoration for its incredible aesthetics? Or do you lean towards zirconia for its sheer strength? And if you choose zirconia, which specific type?
This article won’t just give you theoretical information. We’re going to dive deep into the subject, comparing these materials based on both current research and extensive clinical experience. Our goal is to guide you to the correct decision, ensuring you work with confidence and your patient receives a restoration that looks great and lasts for years.
Understanding the Adversary: The Destructive Force of Bruxism
Before we can even select our weapon, we need to understand the power of the enemy we’re up against. Bruxism isn’t just simple tooth-to-tooth friction. The forces generated during nocturnal clenching or grinding can reach up to six times the normal chewing force (1). We’re talking about immense, continuous pressure exerted for hours every single day.
This relentless force is capable of fracturing old fillings and restorations. It causes severe wear on natural tooth enamel and can even lead to fractures and cracks in otherwise healthy teeth.
Therefore, any material we choose must be “armored” and ready to enter this battle.
Option One: E-max – Beautiful, Yet Vulnerable
We all have a soft spot for E-max, or as it’s scientifically known, Lithium Disilicate. And its aesthetics are truly stunning. It’s probably the closest thing we have to the natural appearance of a tooth, boasting excellent translucency, and we can bond it with a strength that makes the margin between it and the tooth almost invisible.
But is it actually suitable for a bruxism patient?
The unequivocal answer is: No. In most cases, it’s a very poor choice.
Why? Simply put, E-max is fundamentally a type of glass-ceramic. Imagine it like a chic glass cup—gorgeous to look at, but if it falls or takes a hard knock, it will shatter. E-max is beautiful, but it’s inherently “brittle.” Its fracture toughness is considerably lower compared to zirconia.
When you place a brittle material like this under the relentless, crushing forces of bruxism, the outcome is usually one of two things:
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Chipping: Small fractures occurring at the edges of the restoration.
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Catastrophic Fracture: A complete break of the restoration into two or more pieces.
The Bottom Line: Reserve E-max for cases demanding high aesthetics and moderate occlusal forces, such as anterior incisors or veneers in patients who do not exhibit bruxism. But if your patient is a “grinder,” steer completely clear of E-max for posterior teeth (2).
Option Two: Zirconia – The Robust Workhorse
When it comes to strength and durability, nothing in the world of ceramics truly rivals zirconia. Its strength can exceed 1200 megapascals (MPa), meaning it can comfortably withstand the intense forces of bruxism.
However, are all types of zirconia created equal? This is where the crucial distinction lies, separating an informed dentist from one who simply asks the lab for “a zirconia crown.”
The zirconia we use has different generations and types, with the most significant difference being the balance between strength and translucency:
First Generation: The Traditional Tank (3Y-TZP)
This is the original workhorse. Extremely strong, typically around 1200 MPa. Its main drawback is that it’s quite opaque, with a very unnatural, chalk-like white appearance. This is why, in the past, we often used it as a core and layered porcelain over it (PFZ), which unfortunately led to common porcelain chipping.
Newer Generations: Aesthetic Zirconia (4Y-TZP & 5Y-TZP)
Manufacturers modified its composition to boost its translucency and make its appearance more appealing, closer to natural teeth. The catch, however, is that this aesthetic enhancement came at the expense of strength. These aesthetic zirconias have reduced strength, potentially dropping to 600-800 MPa. While still stronger than E-max, they don’t quite match the brute force of the first generation (3).
So, we find ourselves at a crossroads: do we opt for the stronger zirconia that isn’t as aesthetic? Or do we choose the more aesthetic zirconia that might not withstand the most extreme grinding forces?
The Ideal Solution: Monolithic High-Strength Zirconia
The ingenious solution that has emerged as the go-to choice globally for bruxism patients is to utilize the strongest type of zirconia—the first-generation 3Y-TZP—but without covering it with a porcelain layer. We fabricate the entire crown from a single block of this robust zirconia, which is what we refer to as Monolithic Zirconia.
One of the most renowned international brands for this type is BruxZir® Zirconia; its very name, derived from “Bruxism,” directly communicates its intended purpose for these challenging cases.
Why is this solution so ideal?
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Immense Strength: You get the maximum strength of zirconia, 1200+ MPa, meaning it’s virtually unbreakable under grinding forces.
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No Chipping: Since there’s no external porcelain layer, there’s nothing to chip or peel off. The entire crown is a single, homogeneous unit.
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Highly Acceptable Aesthetics: While it might not possess the unparalleled beauty of E-max, with modern staining and polishing techniques available in dental labs, its appearance is now perfectly acceptable for posterior teeth.
A Critically Important Point about Opposing Tooth Wear: There’s an old myth that zirconia “wears down” the opposing tooth. This might have held some truth in earlier days when we lacked proper polishing techniques. However, contemporary research has conclusively shown that a highly polished zirconia crown presents a surface that is actually smoother than porcelain, causing the lowest possible amount of wear on opposing natural dentition (4). The key to this benefit lies entirely in the final finishing and meticulous polishing. You absolutely must emphasize to your dental lab the importance of achieving an excellent polish.
Working Protocol: How to Prepare and Cement Such a Restoration
So, you’ve decided to place a Monolithic Zirconia restoration for your bruxism patient. How do you proceed?
Preparation
Zirconia thrives on clear and conservative preparation. It generally requires at least 1 to 1.5 mm of reduction on all surfaces (occlusal and axial). Most importantly, all line angles must be rounded. Zirconia dislikes sharp angles intensely, as these create stress concentrations and can lead to fracture.
Cementation
This is one of the most appealing advantages of high-strength zirconia: it doesn’t demand complicated bonding protocols.
The best options for luting these restorations are Resin-Modified Glass Ionomer (RMGI) cements, like RelyX Luting Plus, or Self-Adhesive Resin Cements, such as RelyX Unicem 2. Cementation with these is straightforward, quick, and involves fewer steps.
Post-Insertion: The Final Secret Weapon – The Night Guard
Your work isn’t fully complete just by placing the crown. The most critical step in the treatment plan for a bruxism patient is to fabricate a custom night guard for them.
The night guard doesn’t just protect the new restoration; it also shields the rest of their teeth and significantly reduces the strain on their masticatory muscles and temporomandibular joint. You must explain to the patient that the night guard is an absolutely integral part of their comprehensive treatment.
The Takeaway: What to Do When a Bruxism Patient Arrives
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E-max: A beautiful choice, but emphatically avoid it for posterior teeth in bruxism patients.
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Aesthetic (Translucent) Zirconia: Might be an option in some anterior cases if the bruxism isn’t severe, but it’s not the primary choice for posterior restorations.
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The Golden Solution for Posterior Teeth: A Monolithic High-Strength Zirconia crown, such as BruxZir.
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Crucial Lab Instruction: Insist on excellent polishing to protect the opposing dentition.
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Treatment Plan Incomplete Without: A custom night guard.
By diligently following this clear protocol, you will be able to provide your patient with a solution that perfectly combines the strength to withstand the toughest conditions, acceptable aesthetics, and long-term safety.
