Bridges

Bridges are used primarily for tooth replacement. In lab we're working on preparing a 3-unit bridge, replacing #19 (lower left first molar). To do so we prepare the adjacent teeth as abutments in a form that makes for adequate retention, support and stability. The hardest point thus far is creating a path of insertion parallel to both abutments, and not creating undercuts, so that the final restoration seats correctly.

Clinically, bridges present the ethical dilemma of preparing sound tooth structure, which is something we always want to avoid. In some cases, all teeth involved in the bridge may be carious and should be replaced, but this may not always be the case. With the advent of implants and their becoming more affordable, we should eventually be able to replace a tooth without having to compromise any others.

Once we prepare the teeth, an impression is taken, a Jadestone cast poured and the teeth are once again waxed up.The tooth being replaced is known as the pontic. In our case, #19 is our pontic. We create a heart-shaped/conical pontic, with a point contact on the mucosa to allow for cleansability. The teeth are waxed together as one unit by connectors placed in the interproximal region. Our connectors were made to be 3mm x 2.5mm, but this can vary. Ideally we also want the teeth to contact in the same places that they do on the contralateral side. In this case, I created contacts on the Buccal cusp inclines, and distal marginal ridges of #20, #19 and #18. Tricky, but all the more satisfying once complete.

Next step - investing, in our phosphate investment material - Formula One. Then casting. This time around, our rings are being cast by the lab  technicians. More fun to come!