Definitions of words and language used in modern dental conversations
Communication is paramount when discussing treatment with your patient, colleagues, and lab, the intention of this dental glossary is to ensure we are all on the same (web)page. As dentistry modernizes, new methods, materials, and practices come into play requiring new words and language—many detailed below reflect the linguistics of digital dentistry. We have organized this digital dentistry glossary by category rather than alphabetically, if you have issues locating the term you are looking for, use the Find function in your browser (desktop: go to top of window, click Edit, click Find, click Find again and type).
Crown and Bride glossary terms
Chamfer Crown prep
A Horizontal Crown preparation similar to knife edge, but with a deeper cut, great for patients with weaker teeth, used with metal and cast-metal crowns
If you select a chamfer crown preparation, you’ll be creating a well-defined finishing line—a bit like a knife edge but with a deeper cut and greater angulation —meaning you can allow a marginal width of up to 0.3 mm. [note: Dandy prefers Shoulder prep for Crowns and Bridges in digital dentistry]
Many dentists prefer chamfer over other techniques because the marginal fit is adhered toward a larger tooth surface, making an angle that exhibits less stress on the tooth itself. This guard against fracture in patients with weaker teeth.
Chamfer prep is historically only recommended for full cast-metal crowns like gold (and occasionally metal-ceramic), because even the thinnest cast-metal materials are quite resilient, and we’re already dealing with narrow finish margins. You need a strong, thin material for the crown.
When working on the existing tooth to create this margin, there is no hard and fast rule on which bur you should be using to shape, just know that it’s up to the dentist to create the right-shaped margin with whatever tip and bur you choose. To create a good chamfer, do not engage the whole shape of your bur. Ensure that half the diameter is outside the margins, because a chamfer prep width is only 0.3 mm.
Dental composite restoration (composite veneers)
Resin-based composites that are replacing classic metal fillings and can match tooth color
For those with metal allergies or reactions, gone are the days of silver fillings as the main restoration option when cavities or tooth injuries crop up. Composite restoration describes the process in which a composite resin is used to restore teeth that don’t need full crowns.
Made from a mixture of resin and natural materials, composite bonds to the tooth’s structure, not only “filling” the cavity and restoring the physical integrity, but strengthening it for the long haul. This also means less drilling and less tooth loss, because instead of covering, composite work is actually rebuilding and restoring the injured tooth.
Composite veneers, like porcelain, only cover the front of the tooth, but when compared to porcelain veneers, have the added flexibility of being able to be removed later, if additional work needs to be done. The process bonds veneers but does not remove enamel, as in the case of traditional porcelain veneers.
But the real appeal in composite restoration is the color matching and finish. Metal fillings look like metal; resin-based composites are added in layers, cured, and hardened. This process is repeated until the tooth is completely restored. The finished product is then shaped, polished, and shaded to match the original tooth and teeth around it.
The resin hardens in moments (with a special light) instead of days, can be easily repaired if damaged, and provides a restoration solution that doesn’t require the commitment and cost of a full crown restoration, for teeth that are still relatively healthy outside of cavity base or injury.
eMax Crowns and Bridges
A newer all-ceramic crown material, alongside zirconia, that offers tremendous esthetic benefit over traditional ceramic and metal
Ceramic mix (meaning, covering metal) crowns are often affordable and have been the standard for a long time, but this material also has long-known disadvantages. Some patients are allergic, many don’t love the appearance, and they are less comfortable than their ceramic (and more expensive) counterparts. eMax crowns and bridges, made from lithium desiccated ceramic, represents an all-ceramic alternative.
eMax Crowns and Bridges are translucent, durable, and known for incredible color matching and natural appearance. There is no metal band at the gumline as with metal-mix crowns, and they’re lighter and thinner, meaning less tooth has to be removed to fit. Like zirconia, they also provide better, more comfortable fits than metal, and there aren’t the worries of allergic reaction when you’re dealing with ceramic restorations.
eMax crowns are a little more prone to cracking than metal, of course, but are substantially strong. eMax Bridges are often supported by more-durable zirconia.
The crowns themselves are designed in a lab on computers, aided by impressions or the much-simpler digital intraoral scan, and then milled from a block of ceramic using a super-fancy modern milling machine before being glazed and fired. The result is one of the best, most durable and esthetically pleasing restorations available. The only downside? The cost.
The eMax bridge or crown is worth the money, but not everyone can justify the expense—which is understandable, since many other very solid options, like zirconia, exist in the field of modern dental restoration.
Feather Edge Crown prep
A vertical Crown preparation without a defined finish line that preserves more tooth structure, and is great for all-ceramic crowns
When you’re preparing a tooth for a crown, you might pick a Feather Edge—this is a vertical finishing line, meaning there’s no defined finish line. This helps preserve tooth structure and can be ideal for marginal adaptation.
Feather edge (also known as a knife-edge chamfer) is so named because of the feather-thin margins. When you have a patient with fairly healthy tooth structure and want to keep as much of that as possible, this option presents as a flexible, fast, and sturdy crown preparation [note: Dandy prefers Shoulder prep for Crowns and Bridges in digital dentistry].
And there is nothing wrong with a conservative preparation (meaning saving tooth structure), and feather edge can be well-utilized for marginal adaptation, where we’re selecting the crown, trimming it to proper length, crimping its edges to proximate the prepared tooth, and then finishing. Feather Edge was originally primarily used with gold and metal, but is also now useful for newer zirconia crowns.
Dentists also love vertical preparations because the final line can be finished at various levels, and is often based on the patients’ gingival tissue information (gum health), letting clinicians make the call and modify emergence profiles, but ultimately also just perform simpler and faster preparations. The marginal width of your finish line will be less than 0.3mm, making this the narrowest when compared to Chamfer and Shoulder Preparation techniques. In instances of significant damage or tooth decay where you want to retain less tooth base, you might look to other preparation methods.
Gingival Retraction Cord
A cord that helps dentists pull the gum back to properly evaluate teeth for much dental work; digital scanning lessens the time you need to use them
During the preparation for crown and bridge procedures, dentists need to be able to get a clear working view of the tooth (or teeth) they’ll be preparing for work. Knowing what’s going on below the gumline is important, as many of our margins will end here, and x-rays can tell us some things, but not everything. So we need to displace gum tissue (the gingiva) before an impression or scanning. Enter the gingival retraction cord.
Gingival retraction cords are thin, flosslike “cords” that are wrapped around a tooth to “pull back” the gingiva and give dentists a clear view (and impression) of margins. These cords are often made of braided cotton of polyester fibers, and look like a flossing device (or string) connected to a stick. And while some impression materials like silicon create a gingival gap large enough to make the retraction cord pointless, with digital intraoral scanning, some displacement is still necessary to get a full view of the tooth and gum.
The good thing is, gingival retraction cords are safe. A good dentist will evaluate a patient’s dental health before using this device to reduce the potential for swelling and bleeding, and will also take care to quickly remove the cord to minimize gum irritation. With the advent of digital intraoral scanning, we’re able to spend less time retracting the gums than with traditional impressions, further reducing the sometimes-irritating side effects.
Layered Zirconia vs. Monolithic Zirconia
You may pick between solid zirconia and layered when preparing zirconia crowns—each has its advantages.
Monolithic zirconia refers to material that is formed of a single block. This material is super-sturdy, durable, and works for crowns, implants, and bridges up to 35mm in span. You will find it in situations where an all-metal crown may have previously been the recommendation.
Layered zirconia (also known as multilayer zirconia, or porcelain zirconia) is coated with a special ceramic where teeth are visible. You will find layered zirconia as the modern replacement for most PFM (porcelain-fused-metal) crowns. Layered is good for longer bridges (up to 48mm) compared with monolithic, as well as some inlays.
The differences between these options are mostly in durability. Solid is recommended for heavy bites (bruxism) and posterior teeth because of its near-invulnerability.
As the uses of each are different, the preparations will also be typically, similarly different: feather-edge preparations for posterior monolithic zirconia crowns, but chamfers for the more esthetically pleasing (and commonly anterior) layered zirconia crowns.
Both options are terrific advancements in restorative dentistry, helping clinicians replace teeth with a material that doesn’t get hot or cold, never produces allergic irritation, and lasts nearly as long as solid-metal. And because modern dentists are often moving away from impressions and toward intraoral digital scanning, the milling machines and labs that create zirconia crowns and bridges are able to deliver these restorations both faster and with more precision than once seemed possible.
Maryland Bridge dental / Maryland Bonded Bridges
For patients missing teeth but who aren’t suited to dental implants or traditional bridges, the Maryland bridge (aka a resin-bonded bridge or Maryland bonded bridge) is a conservative, cost-effective option.
The process involves two metal (or ceramic) wings on either side of the missing tooth, bonded with a special dental adhesive, onto which then the pontic (the replacement restoration) is attached. This creates a bridge where the tooth is missing, without requiring the adjacent teeth to be prepared or shaped for crowns. More natural tooth structure is preserved, less work is done, and a Maryland bridge can be removed, if the patient’s long-term needs or care changes over time.
Of course this procedure has a few drawbacks — you have to have healthy adjacent teeth for the bonding, Maryland bridges can cover up to 2-3 missing teeth, but Maryland bridges aren’t as long-lasting as some of their traditional, more invasive counterparts. It’s a cost-effective, fairly uninvasive option that many dentists prefer, especially for its flexibility in patient care.
PFM – Porcelain fused to metal crown
Porcelain covering a metal crown, which was the longtime preferred crown in dentistry
A longtime dental standard, porcelain-fused-to-metal crowns (PFM crowns) and bridges combine the strength and durability of a metal base with the esthetics of porcelain.
The are what they sound like. A metal base is covered with porcelain and fused with a process called baking, giving you almost all of the benefits of metal with the look of a tooth. They are affordable compared to all-porcelain, zirconia, or eMax restorations, metal bonds well to teeth, and so long as you don’t have irritation or allergic reaction, PFM work is built to last.
For people with night grinding, porcelain fused to metal bridges are one of the more common recommendations, and PFM bridges are good for any span. Another reason PFM crowns have been a popular choice for decades is a high rate of success. It’s one thing to say “they’re durable,” but the benefits of metal really are proven across the years.
And now, the disadvantages:
Despite the translucency of porcelain and excellent color-matching, one esthetic concern is that it’s impossible to cover the entire metal base, and most PFM crowns show a small gray line in patients’ smiles. Technology has given dentists the “porcelain butt joint margin,” which covers this line, but some gum recession is inevitable as we age.
PFM restorations will also require you to lose a lot of your tooth to fit the metal base. It is always better for long-term health to preserve as much tooth as possible, of course, even when restorations need to happen for the same dental-health reasons.
Porcelain will wear out existing, opposing teeth in the long run (and occasionally chip), but as with some of these other disadvantages, the cost and benefit always tips toward getting a good restoration. Which brings us to cost.
The best way to improve your durability and long-term satisfaction with a PFM Bridge or PFM Crown is to go with precious metals. Gold is expensive, but it lasts a long time. From Gold on down through base metal alloys like silver or nickel, you can adjust work to a budget and still leave patients with a winning smile and work that’s built to last.
PFZ – Porcelain fused to zirconia crown
A stronger composite restoration production gaining popularity
One of the main drawbacks to the (very sturdy) porcelain-fused-to-metal crown is the possibility of chipping the porcelain and revealing the less-esthetically pleasing metal beneath. Durability is not a major issue, but porcelain does fuse even better, making a stronger composite crown, to some ceramic materials — even more than it does with gold. This is to say that porcelain stands even less of a chance of pulling, peeling, or chipping away from its base with zirconia even than metal.
And so we have the porcelain-fused-to-zirconia crown and bridge. Zirconia can often be a good match to existing teeth, but translucency can be an issue. Add a porcelain coating, and you’ve got an even better match—rivaling even eMax.
The biocompatibility of zirconia and its strength are hard to ignore, and many dentists are opting for the material even before porcelain finish.
Shoulder Crown prep
A horizontal crown preparation similar to knife edge, but with a deeper cut, preferred by Dandy for digital Crowns and Bridges
Shoulder crown preparation (also called a “butt” finishing line) is basically the least conservative crown finishing method, on the basis that it’s the method where you’re removing the most volume of tooth structure—which mightly helps in getting a clear scan.
To accommodate visibility and provide support for this bulk, we make a small shoulder around the tooth, onto which the crown fits. Axial walls, then, meet your finishing line at a right angle, with a marginal finish line above 0.3mm—wider than feather edge or chamfer crown preparation. Clinicians should take care to avoid undercuts where the shoulder meets the (tooth’s) axial wall, a common area for mistakes in fit and later failure.
Successful Shoulder Crown prep ends up producing remarkably natural restorations that last, as zirconia crowns create tremendous aesthetics when matched to existing tooth color. The easy, accurate edge closure attainable with shoulder prep also means that the crown also helps improve long-term dental hygiene as much as possible.
Yttria / Yttria-stabilized Zirconia
Yttria is the element number 39 on the periodic chart, a silvery-metallic transition metal that. When yttrium oxide is combined with zirconinum oxide, we get yttria-stabilized zirconia—a super-strong, super-durable ceramic that’s resistant to corrosion, oxidation, and high temperatures.
Yttria-stabilized zirconia is, due to these properties, a fast-growing top choice for crowns and bridges, because of this resistance to fracture and chipping. it also can blend (and be shaded) to match teeth. Zirconia restorations are already popular among contemporary dental work, and increased yttria content is making them even more durable. The more yttria in a zirconia crown, the more sturdy, but less aesthetic.
Zirconia Crowns and Bridges
Biocompatible zirconium oxide crowns, and a miraculous modern dental restoration material
Consider how much you bite, how often, and with how much force — our teeth are miracles, and approximating them with man made material is one of the great challenges in the history of dentistry. Zirconia crowns are a major leap forward in the direction of solving these challenges.
Made from Zirconium Oxide, Zirconia crowns and bridges are strong and durable, long-lasting, and available in shading to approximate dozens of tooth colors. One of the main reasons that traditional porcelain (or porcelain-fused-to-metal) crowns don’t last is because of fracture. Zirconia is so strong that clinicians don’t have to do as much preparation (and don’t have to sacrifice as much of your existing tooth to this preparation).
The crown and bridge material is biocompatible, and won’t trigger allergic reactions or irritation, and because the crowns are made on a milling machine often aided by CAD/CAM technology, the fit is next-to-perfect.So what’s the catch? There aren’t a ton. Zirconia crowns and bridges are becoming increasingly common and indicated for all types of procedures. Many dentists were initially afraid that the too-tough material would damage other teeth, but over the last decade studies have revealed zirconia to be, in many cases, as durable as metal but less-damaging than even some porcelain options.
Note: When you see the words “lava crown,” you’re seeing a zirconia crown, only the variety trademarked by the 3M company, which uses an also-trademarked porcelain (“Lava Ceram”) to finish and aid with translucency and look.
Zirconia Crown prep
The newest crown material on the block is popular, its preparation is similar to ceramic counterparts, and much-aided by modern technique
Zirconium oxide (zirconia) crowns are becoming increasingly popular for a few reasons, including their durability and color/aesthetic accuracy. They’re the newest player in dental restoration, and dentists everywhere have fallen in love with what is quite simply a top-quality, well-loved new crown.
Zirconia allows for a wider variety of shades, smoother edges leading to fewer fractures, and great fit. Their prep works similarly to other (metal and ceramic) preparations, and as zirconia is thicker than metal, it’s usually recommended to go with a shoulder preparation. Whether you’re working on anterior or posterior teeth, one of the best parts about going with modern materials is that you typically are accompanying them with modern techniques.
Intraoral scanning is rapidly replacing impressions to find shape, size, and fit. A digital scan sent to a lab can save days and weeks on crown preparation, and provide a level of measurement precision that allows for crowns with better fit.For a zirconia crown, you’ll pay attention to clearance and circumferential chamber as has been done on ceramic and metal restorations forever. Zirconia allows for stronger, prettier crowns that last longer and promote better dental health and hygiene. See Dandy’s Complete Zirconia Crown Prep Guide for the nitty-gritty when it comes to margins and chamfer recommendations.
Dandy’s digital dentistry glossary will be updated regularly.