Main Measuring methods
Many things have been said about the IPG classifications, but up to this moment it is more and more confusing. For instance what does it mean model based Surgical Guide? If we scan the model and import it into the imaging software and CAD software, is it model based IPG? Probably yes. Does a guide made from linear markers is a model base? Probably yes too.
So what is the right way to differentiate and to classify the guides?
Well, no matter the technique the common milestone in the process of creating a guide, is linking the model to the image of the CBCT. That link can be done by using two different ways.
The first way is to link separately each implant location by using linear markers that were prepared from drillings of the model (SGLA, Guide Right). In that technique each marker defined as a new X, Y, Z, having value 0 while the common foothold is the apical end of the marker on the CBCT equal to the mucosal end of the model drilling (fig.1 and fig.2)
The fact that there is a discrepancy between the CBCT and the stone model, resulting serious issues of accuracy in both these methods. However in the first method having resetting the foothold to zero with every new location of the implant preventing the error from being dragged all over the model. Another advantage of the first method is the fact that we actually transfer from the CBCT the angles only and not the locations. The locations of the osteotomy in the first method are linked exclusively to the stone model.
The (CNC) method allows working in a relatively simple algorithm that is much easier for 3D printing manufacturing. In cases where there is an abundant amount of bone (more then 3mm of bone from each side of the implant) the (CNC) method may be applicable.