RPD Manual 11 - Removable Prosthodontics - Dalhousie University

Surveying, Path of Insertion, Guiding Planes - 20
Selection and Preparation of Guiding Planes:
a. A path of insertion is selected.
b. The number and position of guiding planes is selected.
c. With the diagnostic cast as a guide, parallel surfaces are prepared intraorally with straight
cylindrical burs (#1156 or #557L or equivalent cylindrical bur). The surveyed cast should
be nearby for comparison, so that the bur can be placed in the same relationship to the
tooth as the analyzing rod makes with the diagnostic cast.
The bur should be placed at the same
angulation as the surveying rod. The
triangular space below the height of
contour should appear to be the same.
d. Guiding planes should be at least 1/2 to 1/3 of the axial height of the tooth (generally a
minimum of 2 mm in height). Use a light sweeping stroke continuing past the bucco- and
the linguo proximal line angles. Reduction should follow the bucco-lingual curvature of
the tooth, rather than slicing straight across the tooth. Guide planes for distal-extension
cases should be slightly shorter to avoid torquing of the abutment teeth. Lingual guiding
planes for bracing or reciprocal arms should be 2-4 mm and ideally be located in the
middle third of the crown, occluso-gingivally. Use a good finger rest to establish parallel
planes.
e. If tooth surfaces selected for guiding planes are already parallel to the path of insertion,
little if any tooth modification may be necessary.
f. The prepared surfaces are polished rubber wheels or points.
g. Guiding planes are the first features prepared intraorally. If occlusal rest seats are prepared
initially, placement of a proximal guiding plane will remove some of the rest seat
preparation, and result in a narrowed rest with a sharp occluso-proximal angle.