The ‘Maryland Bridge’ in Dentistry: Baltimore’s Influence in Global Prosthetics

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The ‘Maryland Bridge’ in Dentistry: Baltimore’s Influence in Global Prosthetics

Dentistry has one of the strangest vocabularies in medicine. Some of it comes from Latin, some from civil engineering, and at least one phrase comes from Baltimore. Specifically, from the University of Maryland School of Dentistry, which opened in Baltimore in 1840 as the Baltimore College of Dental Surgery. It was the first dental school anywhere in the world. If you have ever wondered why your dentist is a DDS rather than an MD, that degree was invented there too.

The Maryland bridge really is from Maryland

The problem the Maryland bridge solved is that of traditional dental bridges: grinding the healthy teeth on either side of a tooth gap. In the early 1980s, two researchers in Baltimore, Gregory Livaditis and Van Thompson, worked out that etching the inner surface of two metal wings with acid and an electrical current gave the resin cement something microscopic to hold onto. 

That is a Maryland bridge. A replacement tooth with thin wings bonded to the backs of its neighbors. Modern versions are usually ceramic and often use a single wing instead of two. That has proved to be a better design long-term, as one wing flexes with its own tooth and stays put.

The problem of traditional bridges

In order for traditional dental bridges to carry a replacement tooth, the teeth on either side of the gap are cut down into pegs so crowns can be seated over them. A 2002 study weighed exactly how much disappears: preparing a front tooth for a conventional crown removes roughly 63 to 72 percent of the visible tooth by weight. 

That missing two thirds cannot be rebuilt.

Then there is the nerve. Removing that much structure means working close to the living pulp at the tooth’s center, generating heat as you go. In long-term follow-up of teeth used as bridge supports, only about two thirds still had a living nerve fifteen years later. 

Conventional bridges also do not last forever, and roughly a quarter have failed by year fifteen. 

The original Maryland bridge

The original Maryland bridge was designed to fix these imperfections, but it carried flaws of its own. Those etched wings were nickel-chromium alloy, and metal is completely opaque. Front teeth are not. Bond a dark grey plate behind one and the light stops passing through. 

Ceramics fixed that. Lithium disilicate came first, then zirconia, the same material used for a zirconia crown on a back tooth. Zirconia is strong enough to be milled into a wing under a millimeter thick, and it is white, so nothing shadows through.

Getting it to stay put took longer. Glass ceramics can be etched with acid, which roughens the surface for the cement to grip. Zirconia shrugs acid off entirely. The fix turned out to be air-abrading the fitting surface with fine alumina particles and using a cement containing a phosphate monomer that bonds chemically to zirconia. 

Why one wing beats two in the modern Maryland bridge design

When one wing debonds in a Maryland bridge, the other holds everything in place, so nothing feels loose and nothing looks wrong. But there is now a sheltered gap between the wing and the tooth, sealed off from your toothbrush and open to saliva. Decay develops there for months, unnoticed, on a tooth that was healthy when this started.

A single wing moves with its own tooth, and if it ever let’s go, the bridge comes out in your hand and you know immediately. It’s also supported by data. Single-wing bridges show ten-year survival around 94 percent, against 74 percent for the two-wing design. Newer single-wing zirconia versions report survival above 97 percent at fifteen years.

Current Innovations

The school on West Baltimore Street is 186 years old this year and still running, which means somebody there is currently working on something that might replace the Maryland bridge.

Whatever eventually makes the Maryland bridge obsolete has to come out of a laboratory somewhere. It might be in Japan. Researchers at Kyoto University showed that blocking the USAG-1 protein with an antibody wakes dormant tooth buds which can grow an extra tooth. A first human trial in Japan has finished and reported the drug appears safe, with a small pediatric trial planned next for children born missing several teeth.

Worth being clear: no human has grown a tooth from this yet. It may not work in people, and if it does, it will help patients with congenital missing teeth long before it helps anyone who lost one to a hockey puck.

Less dramatic possibilities may arrive sooner. Ceramic implants that avoid metal entirely. Narrower implants for gaps a conventional one will not fit. Better ways of rebuilding lost jawbone, which is usually the real obstacle.

Either way, the sensible move today is the one Livaditis and Thompson were making forty years ago. Take away as little natural tooth as possible, and leave the door open for changes without negatively affecting your mouth.

References

1. University of Maryland, Baltimore. “UMB Celebrates America at 250: Where Dentistry Cut Its Teeth.” The Elm, 15 July 2026. https://elm.umaryland.edu/elm-stories/2026/UMB-Celebrates-America-at-250-Where-Dentistry-Cut-Its-Teeth.php
2. Livaditis GJ, Thompson VP. “Etched castings: an improved retentive mechanism for resin-bonded retainers.” Journal of Prosthetic Dentistry. 1982;47(1):52–58. For a historical overview, see also: Durey K, Cook P, Chan M. “The resin bonded bridge: techniques for success.” https://www.sciencedirect.com/science/article/pii/S0889540619307279
3. Edelhoff D, Sorensen JA. “Tooth structure removal associated with various preparation designs for anterior teeth.” Journal of Prosthetic Dentistry. 2002;87(5):503–509. https://www.thejpd.org/article/S0022-3913(02)00007-0/abstract
4. Cheung GSP, Lai SCN, Ng RPY. “Fate of vital pulps beneath a metal-ceramic crown or a bridge retainer.” International Endodontic Journal. 2005;38(8):521–530. https://pubmed.ncbi.nlm.nih.gov/16011770/
5. Yazigi C, Kern M, et al. “Long-term outcome of anterior cantilever zirconia ceramic resin-bonded fixed dental prostheses: Influence of the pontic location.” Journal of Prosthetic Dentistry. 2025. https://www.thejpd.org/article/S0022-3913(25)00071-X/fulltext
6. Alqarawi FK, et al. “Do zirconia single-retainer resin-bonded fixed dental prostheses present a viable treatment option for the replacement of missing anterior teeth? A systematic review and meta-analysis.” Journal of Prosthetic Dentistry. 2022. https://www.sciencedirect.com/science/article/abs/pii/S0022391321005886
7. Kern M, Sasse M. “Ten-year survival of anterior all-ceramic resin-bonded fixed dental prostheses.” Journal of Adhesive Dentistry. 2011;13(5):407–410. doi:10.3290/j.jad.a22096
8. Murashima-Suginami A, Kiso H, Tokita Y, et al. “Anti-USAG-1 therapy for tooth regeneration through enhanced BMP signaling.” Science Advances. 2021;7(7):eabf1798. https://www.science.org/doi/10.1126/sciadv.abf1798
9. “Tooth regrowth in adults: what we know so far.” Dentistry, 18 August 2026. https://dentistry.co.uk/2026/08/18/tooth-regrowth-in-adults-what-we-know-so-far/