Arch Open_Base (used to replace the conventional stone base):
Medium (green) Open_Base shown (OPEN-8).
There is a set of index marks for each cuspid and each first molar location. This is necessary because Open_Bases can be used as either an upper or lower. The lower cuspid and lower first molar in a normal mouth is usually anterior of the upper cuspid and upper first molar. Aligning teeth to the correct index marks will insure a better relationship between upper and lower models when articulated.
Using the Open_Base has several advantages over the conventional stone base:
1. Uses less stone and allows less shrinkage
(dimensionally more stable).
The numerous small pins sticking up adjacent to the inside and outside walls are there to prevent the plastic wall from pulling away from the stone when the saw blade starts cutting into the plastic while sawing out dies.