Accuracy of facial plaster casts.

OBJECTIVE

The aim of this study was to evaluate the accuracy of facial plaster casts and their suitability for 3-D mapping.

MATERIALS AND METHODS

All measurements were carried out on 15 adult probands (seven female and eight male; age range 19-31 years, mean 24.7 years). A plaster cast of the facial surface was prepared for all probands using alginate impressions. The plaster casts and the probands faces were digitized using a three-dimensional laser-scanner operating with structured light. The resulting point clouds were matched in a virtual environment to analyze the deviations between the cast and the facial surfaces, both qualitatively and quantitatively.

RESULTS

The average deviations depended on the facial area and lay between 0.95 and 3.55 mm. Marked differences between the plaster cast and the facial surface were found, particularly in the area of the lips, at the roof of the nose, at the cheeks, and in the entire lower facial area.

CONCLUSIONS

The regionally exacerbated soft tissue deformations that occur during impression of the facial surface lead to inaccuracies in the resulting plaster cast that forbids any use for morphometric analysis. Documentation of pathological findings in cleft lip and palate using facial plaster casts does appear to be justifiable.