In the preclinic the occlusion rims are 18mm and 22mm long. This is an unusual length. Generally speaking occlusion rims are about the size of teeth. (There is a thin layer of wax that extends to the fold area. This gingival portion makes the occlusion rim longer.)
How long is a maxillary central? 11mm? How wide is a molar? 10-11mm? The anterior section of the occlusion rim should be thinner (facio-lingually) than the posterior. A thick occlusion rim anteriorly will affect the patient's speech.
Of course you can make the occlusion rim any length because you can add or subtract the wax.
Occlusion rims should be made of wax that is hard. Remember they have to maintain the vertical. You can buy premade soft wax rims. Don't use them.
Do NOT make your occlusion rim out of layers of baseplate wax. When cutting into the occlusion rim the layers will separate. To make your rim use one sheet of baseplate wax...warm, and tightly fold it into the shape of a cigar. Sear it to your recording base and shape as necessary.
Before you take the facebow it is not critical to perfect the maxillary rim. If it looks reasonable it's fine. At this point all you need is something to attach your fork to. Later on you can perfect it. (Some instructors will want the rims to be gorgeous right now. So make it gorgeous.) We will talk more about adjusting the rims when doing the vertical.
Ridges are usually (not always) parallel to each other when the vertical is correct.
Trim your cast bases parallel to the remaining ridges. Now all you need do is look at the base of the cast to visualize the position of the ridges when it is hidden by the recording base.
Make the mandibular occlusion rim first. Half way up the pad, centered over the crest of the ridge in the bicuspid, molar area.. About 10mm wide posteriorly, thinner anteriorly, about the height of a mandibular central.
Then make the maxillary rim. While it is still soft, occlude it with the lower such that the bases of the master casts are approximately parallel to each other. These are your starting occlusion rims.
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©1999 by Julius Rosen, D.D.S.