Clinical Application - Are there problems with these techniques? How are they solved?

Automatically found contours (prior to adjustment and correction). Blue: outer contours; red: inner contours.

The type of model is assessed prior to contour definition because this process is adjusted to the limitations of the model.

Adjustment of above contours for stereolithography.

This means, that for milling models, one can get rid of inner contours which the drills of the milling system cannot reach, whereas for stereolithography, one might even want to add some contours (e.g. within the sinusoidal cavities; see image) which otherwise are neglected by the semiautomated process because they are subject to partial volume effect, or the bone structure in question is very thin.

The techniques in itself do not pose a problem, once the data are converted. However, their application depends on the requirements for the surgeon. In the first place, stereolithography models are more detailed than milling models: this method allows rendering of inner contours (e.g. sinuses). Furthermore the layer interpolation ranges from .1 to .2 mm (.5 - .7 mm in milling models). Thus, stereolithography is asked for when dealing with complex defects which also involve inner contours.
Clear disadvantages of this method are the considerably high costs, and such a model cannot be cut apart easily.

Adjustment of above contours for CNC milling.

Milling model: Right half shell of a skull.

Whenever possible, a milling model is favored: when dealing with a complete skull, prior to contour definition the planning volume is split approximately along the sagittal suture so that the inside of the skull is rendered while two half-shells are produced.
In midface cases, it is advisable to omit the skull base so that the drill has a posterior approach to the maxilla.

The sole application of stereolithography models at our clinic is in severe craniofacial defects, the main issue being the high costs of this technique.

Back to the table of contents

[General] [Team] [Services] [Equipment] [Projects] [Partners]
[Informations] [Office Hours] [Appointments] [Site Plan]
[Home] [Email]