Three-dimensional photoelastic stress analysis of the ferrule effect in cast post and cores.

The effect of a metal collar on stress distribution with cast post and cores was studied by using three-dimensional photoelastic models of maxillary canine teeth of average dimensions. Standardized parallel post and cores were cemented into the models, with half of the samples incorporating a 1.5 mm metal collar. A 400 gm load was applied to the cingulum of the cores and stresses were frozen in the models. The posts were removed, the teeth were sectioned, and stresses were measured with a circular polariscope. In both groups the greatest stress concentration was found at the lingual apex of the post. On a point by point basis, stresses were higher in the collared specimens. Variation in stress magnitude among five preselected points was greater within the noncollared group.

The University of Michigan School of Dentistry, Ann Arbor.

A pilot study has been described in which edentulous subjects were examined for their ability to reproduce lateral border movements, as measured by the PRI. The results of this study suggest that edentulous subjects, utilizing stabilized baseplates to support a pantograph, are capable of making reproducible lateral border movements as measured by the PRI.

Clinical procedures in precision attachment removable partial denture construction.

A technique has been outlined for construction of a metal base precision attachment. The technique emphasizes the need for an accurate impression of the edentulous ridge and construction of a metal base. The metal base is related intraorally to the abutment restorations and fixed via a strut with autopolymerizing acrylic resin. When the relationship has been determined the replacement dentition is added to the base.