Minor Connectors &
Rests
Rola M. Shadid, BDS, MSc
Lecture Outline
 Discuss functions of minor
connector
 Discuss types of minor
connectors
 Discuss functions of rests
 Discuss forms of rests & prep
of rest seats
Minor Connectors
 Connects components to the major
connector
– Direct retainer
– Indirect retainer
– Denture base
Functions of Minor
Connectors
 Unification and rigidity
 Stress distribution *
 Bracing through contact with
guiding planes
 Maintain a path of insertion
via contact with guiding
planes
Types of Minor Connectors
 Embrasure Minor Connectors
– Between two adjacent teeth
Embrasure Minor Connectors
 Should have sufficient
bulk to be rigid but in
the same time
unobjectionable as
possible
 Should be located in an
embrasure not be
located on a convex
surface
 Should be tapering
toward the contact area
Embrasure Minor Connectors
– Joins major connector at right angles
– Relief placed so connector not directly on
soft tissue
Embrasure Minor Connectors
 It should be thickest
toward the lingual
surface, tapering
toward the contact
area
 Triangular shaped in
cross section
Embrasure Minor
Connectors
– Contact teeth
above height of
contour
– Prevents wedging
& tooth mobility
Gridwork Minor Connectors
 Connect the denture base and teeth
to the major connector
Gridwork Minor Connectors
 Adjacent edentulous spaces
 Usually connect major connector
to direct retainers
 Open lattice work or mesh types
Gridwork Minor Connectors
Minor connector for
mandibular distal
extension base
should extend
posteriorly about
2/3 the length of the
edentulous ridge
Never on the
ascending portion
of the ridge
Gridwork Minor Connectors
Minor connectors
for maxillary
distal extension
denture bases
should extend the
entire length of
the residual ridge
Gridwork Minor Connectors
 Mesh type
– Flatter
– Potentially more rigid
– Less retention for acrylic
if openings are small
Gridwork Minor Connectors
 Lattice Type
• Potentially superior retention
• Interferes with setting of teeth, if
struts are too thick
– Both types are acceptable if correctly
designed
Gridwork Relief
 Mechanical retention of denture
base resin
 Allows the acrylic resin to flow
under the gridwork
Gridwork Relief
 Relief wax is placed in the
edentulous areas
 1 mm of relief
Relief Under the Gridwork
 Should begin 1.5 - 2 mm
from the abutment tooth
Relief Under the Gridwork
 Creates a metal to tissue contact
– Preferable since it wears less
– Less porous, (hygiene)
Junction With Major Connector
 Butt joint with slight undercut in metal
 Maximum bulk of the acrylic resin
 Prevents thin, weak edges fracturing
e de ntu lou s rid ge
m a jo r con ne ctor
b utt j oin t
slig h t u nd er cut
in c or re c t (> 9 0° jo in t)
Gridwork Design
Facially just over the crest of the
residual ridge
Position of Major Connector Junction
 Should be ≈ 2 mm medial to lingual
surface of denture teeth
 Ensures bulk of resin around teeth
Mandibular Tissue Stops
 Contact of metal with
cast at posterior of
distal extension
gridwork
 Prevents distortion at
free end during
hydraulic pressure of
processing
No Tissue Stops In Maxilla
 Maxillary major
connector acts as a
tissue stop (no relief)
Proximal Plates
 Minor connectors originating from the
gridwork in an edentulous area
 Broad contact with guiding planes
 May or may not terminate in an occlusal rest
Proximal Plates
Proximal Plates
 Shifted slightly lingually
– Increases rigidity
– Enhances reciprocation
– Improves esthetics
 Often a triangular space below the
guiding plane (an undercut)
Proximal Plates
 Rigid, cannot be
placed in undercut
 Block-out placed in
undercuts prior to
waxing and casting
the framework
Rests & Rest Seats
o The most effective
resistance can be
provided if the
tooth is stressed
along its long axis
o Prosthesis should
engage the tooth in
a manner that
encourages axial
loading
Rest
 A rigid component of RPD resting in
a recessed preparation on the
occlusal, lingual or incisal surface of
a tooth.
 Provides vertical support
Rest Seat
 Portion of a tooth prepared to
receive a rest *
Functions
 Direct occlusal forces along
long axis of abutment
Functions
 SUPPORT - Prevents
impingement of soft tissue *
Fractured abutment, no
rest seat
Slides down incline
Major connector imbeds into tissue
Functions
 Maintains established
occlusal relationships by
preventing settling of the
denture *
Functions
 Maintain components in their
planned positions (maintains
a clasp -tooth relationship)
Functions
 Provide reference for relines or
impressions
Functions
 Act as indirect retainer
– Prevents rotation (Class I or II
RPD’s only)
Form of Occlusal Rest
 Rounded
triangular shape
with the apex
toward center of
occlusal surface
 As long as it is
wide
Occlusal Rest Seat Form
 Base of triangle should be one
third the bucco-lingual width
of the tooth *
Rest Seat Form
 Smooth flowing outline form
(i.e. no sharp line angles)
Occlusal Rest Seat
 Deepest portion is central
Occlusal Rest Seat
 Floor should be
apical to marginal
ridge
 Angle formed by
occlusal rest &
vertical minor
connector from
which it originates
should be less than
90°
“Positive” Rest Seats
 An explorer tip will not slide
off the rest seat
Occlusal Rest Seat
 Directs the occlusal forces along the
long axis of the tooth
 Prevent orthodontic movement
Occlusal Rest Seat
 Floor should be concave or
spoon shaped (ball-&-socket
joint)
 Prevents horizontal stresses
& torque
Occlusal Rest Seat
 Marginal ridge must be lowered
and rounded 1-1.5mm
– Bulk of metal to prevent
fracture *
Occlusal Rest Seat
 Adjacent Tooth
– Rest not flared to facial line
angle
– Lingual flared more - space for
minor connector
Secondary Occlusal Rest *
 To prevent slippage of
the primary rest
 To prevent
orthodontic movement
of abutment tooth
 To direct forces over
greatest root mass of
abutment
Extended Occlusal Rest *
 To minimize further
tipping of the abutment
 To ensure that forces are
directed down the long
axis of abutment
Extended Occlusal Rest
 Extends more than
one half mesiodistal
width of tooth
 One third the
buccolingual width
of the tooth
 Allow for minimum
of 1 mm thickness of
metal
 Rounded with no
undercuts
Extended Occlusal Rest
(Onlay)
If the abutment is
severely tilted, the
extended occlusal rest
may take the form of
an onlay to restore
the occlusal plane
Extended Occlusal Rest
(Onlay) *
 Provide
stabilization
 Restore the
contour &
occlusion of
natural tooth
 Directs forces
down the long axis
of tooth
Double Embrasure
(Interproximal) Rest Seat
 Adjacent rests
are used to
prevent
interproximal
wedging by
framework
 Joined rests are
designed to shunt
food away from
contact points
Double Embrasure
(Interproximal) Rest Seat Form
 Flared more dramatically on facial
and lingual line angles *
Interproximal Rest Seat Prep.
 Avoid reducing or
eliminating contact
points of abutment
teeth
 Sufficient tooth
structure must be
removed *
 Ensure all line
angles are smoothed
Prep. For Rest Seats
 Rests may be placed on sound
enamel or on any restoration
material
 Rests placed on sound enamel are
not conducive to caries in mouth
with a low-caries index provided
that good oral hygiene is
maintained
Prep. for Rest Seats
 Patient should be advised that
future susceptibility to caries
is not predictable and that
much depends on oral
hygiene and possible future
changes in caries
susceptibility.
Prep. For Rest Seats
 A fluoride gel should be applied
to abutment teeth following
enamel recontouring
 If the master cast will be
fabricated from an irreversible
hydrocolloid impression,
application of the gel should be
delayed until after impressions
are made.
Prep. For Rest Seats




Light pressure
High-speed handpiece
+/- Waterspray
Minimal heat is generated
Prep. For Rest Seats
 Keep in enamel
 No anesthesia
Prep. for Occlusal Rest Seats
The larger round bur is
used first to lower the
marginal ridge and to
establish the outline
form of rest seat
A slightly smaller round
bur is then used to
deepen floor of rest seat
The preparation is
smoothed by polishing
point
Prep. for Occlusal Rest Seats
When a small enamel defect is
encountered in the
preparation of an occlusal
rest seat, it is usually best to
ignore it until the rest
preparation has been
completed.
Prep. for Occlusal Rest Seats
 When perforation in
restoration does occur, it may
be repaired, but occasionally
the making of a new
restoration is unavoidable.
Occlusal Rest Seats in Crowns
Occlusal rest seats in
crowns and inlays
are generally made
somewhat larger
and deeper than
those in enamel *
Lingual Rests on Canines &
Incisor Teeth
 A canine is much preferred
over incisor *
 When a canine is not present,
multiple rests that are spread
over several incisors are
preferable to the use of
single incisor
Cingulum Rest Seat Form
 Inverted “V” at junction of gingival
& middle one third of tooth
 < 900
Cingulum Rest Seat Form
Rest seat prep. broadest
at most lingual aspect
of canine
As preparation
approaches proximal
surfaces of tooth, it is
less broad than at any
other areas
Cingulum Rest Seat Form
 Slightly rounded to avoid
sharp line angles
 Test as ‘positive’ with
explorer tip (floor of
rest seat should be toward
cingulum rather than
axial wall)
Cingulum Rest Seat
2.5 to 3 mm
mesiodistal length
2 mm
labiolingual width
1. 5 mm
incisal-apical depth *
Correct Preparation
Preparation Too High
Preparation Too Low
Cingulum Rest Prep.
 Do not create an enamel
undercut
 Cylindrical bur along the
long axis of the tooth
Maxillary Cingulum Rest
Seats
 Avoid opposing occlusion
Maxillary Cingulum Rest
Seats
 1.5 - 2.0 mm clearance for
metal
 Check with articulated
models *
Cingulum Rest Seat Placement
 Place in sound tooth structure*
 Not on amalgam restorations
 If cingulun not prominent or large
pulp
– Use different tooth
– Composite restoration
– Onlay or crown
– Bonded rest seat
Bonded Rest Seat
 Cast chromiumcobalt alloy rest
seat forms
 Attached to
lingual surfaces of
anterior teeth by
use of composite
resin cements with
acid-etched tooth
prep.
Ball (Round) Lingual Rest
 Mesial of the canine teeth when
typical cingulum rest contraindicated
– Large restoration
– Lack of clearance
with the opposing teeth
– Poor cingulum
Ball (Round) Lingual Rest
 Spoon shaped, similar to occlusal rest seat
 More difficult due to the incline of the
lingual surface
 Easily incorporated into crowns
Ball (Round) Lingual Rests
 Rest seats prep. in
-tooth surface if sufficient
enamel thickness exists
-restorations placed in teeth where
enamel thickness is inadequate
 More conservative than cingulum
lingual rest seats
Incisal Rest
 The least desirable placement of
a rest seat
 Incisal rests are used
predominantly as
- Auxiliary rests
- Indirect retainers
Incisal Rest
Lingual Rest Preferable to
Incisal Rest
 Lingual rest placed nearer
horizontal axis of rotation
(tipping axis) of abutment
- Less tendency to tip the tooth *
 More esthetically acceptable
than incisal rest
Incisal rest
 More applicable to
mandibular canine
-Definite support with little loss of
tooth structure
-Little display of metal
Incisal Rest Prep.
2. 5 mm wide
1. 5 mm deep
Incisal Rest Prep.
 Rounded notch
at the incisal
angle with the
deepest portion
apical to the
incisal edge
 The notch
should be
beveled labially
& lingually *
Multiple Incisal Rests
o Take advantage of natural
incisal faceting.
o Tooth morphology does not
permit other designs.
o Can restore defective or
abraded tooth anatomy.
o Provide stabilization.
o May restore or provide
anterior guidance.
References
1. McCracken’s Removable
Prosthodontics, 11th Edition
2005 by McGivney GP, Carr
AB. Chapter 5 and 6
2. Dalhousie continual
education