Influence of width and depth of palatal vault on rigidity of palatal strap: a finite element study.
OBJECTIVE
The purpose of this study was to develop design criteria for palatal straps according to palatal shape.


METHODS
The palatal shapes of 60 dentate maxillary stone casts were measured using a contact-type three-dimensional measuring instrument. Based on the average of the 60 palatal shapes, 5 three-dimensional finite element models (FE models) were constructed: a basic FE model, a wide palatal FE model, a narrow palatal FE model, a deep palatal FE model and a shallow palatal FE model. The FE models were simulated unilateral free-end saddle dentures with the maxillary left second premolar and first and second molars missing. The FE models included a denture base, two rests and a palatal strap. The mechanical properties of Co-Cr alloy, Ti-6Al-7Nb alloy and type IV gold alloy were given to the FE models. A vertical load of 50 N was loaded onto the occlusal surface of the left first molar. Vertical displacement of the distal edge of the denture base was then compared between models.


RESULTS
Compared to the basic FE model, displacement in the wide FE palatal model and shallow palatal FE model was larger, and displacement in the narrow palatal FE model was smaller. The difference in displacement between the deep palatal FE model and basic FE model was small.


CONCLUSIONS
With a wide and shallow palate, it is necessary to design a reinforced palatal strap. With a narrow palate, the anteroposterior width of the palatal strap can be narrower. With a deep palate, it is not necessary to change the palatal strap design according to the palatal shape.
Takanashi
Takuya
T
Department of Removable Prosthodontics and Gerodontology, Tokyo Dental Collage, Mihama-ku, Chiba 261-8502, Japan. ttakana@tdc.ac.jp
Shimamura
Ichiro
I
Sakurai
Kaoru
K