message board How to Do a Keyway Bridge The keyway bridge is used to span an edentulous space while mitigating the stresses destructive to the natural dentition. This case and discussion show the technique and offer variations. Tom Mitchell Member Since: 02/16/04 Post: 1 of 41 Introduction: I use keyways on most lower posterior bridges. There's so much vertical force coming down on the pontics that can damage the bridge. A keyway allows for some movement, protecting the bridge from damage. The procedure is really no different than a routine bridge procedure, and most labs are well aware of the technique. This case is replacing a gold swaged bridge done a few years ago in China. This was done by my old partner in 1987. Great example of the design done right. This is the gold swaged bridge we're replacing done 4-5 years ago in China. Wide open margins all the way around but amazingly very little decay. It's an obvious sway-back bridge due to the supraeruption of #14 after the early extraction of #19. Easy to see how #14 has moved vertically and buccally after the extraction of #19. That extends the palatal cusp into the interocclusal space needed for the bridge, reducing interocclusal space for the restoration and creating an uneven occlusal plane. The first thing I did was shorten the palatal cusp of #14. Now I have more room for the bridge and a level occlusal plane, so developing mutually protected occlusion will be simple. Here's the prep on #18 with mesial and distal box forms and grooving to increase resistance/retention form. For more info on that, see Dr. Lane Ochi's CE course on Dentaltown titled "Fundamentals of Fixed Prosthodontics." 40 MAY 2017 // dentaltown.comhttp://www.dentaltown.com