to entirely cover the rugae region.
• Borders of the connectors should be either 6 mm from the gingival
margin or extend onto the lingual surface of the teeth.
• All borders should be curved and well rounded.
FIGURE 16-4 Horseshoe-shaped or U-shaped major
• In case of class IV situations
• In cases on inoperable tori extending onto the soft palate
• In cases of hard median suture
• These can derive little vertical support.
• In patients with large overbite, this connector can be suitable to
support the replacement teeth even in thin sections.
• The connector has a tendency to spread apart when vertical force is
• These are not used in distal extension cases.
• The patient may complain about speech problems.
Closed horseshoe or anteroposterior palatal strap (fig. 16-5)
• It is rigid and has adequate strength.
• It can be used in most of the partial denture situations.
• It is mostly used when there are large maxillary tori with more
• Border of the connector is kept 6 mm from the free gingival margin.
• It should be ensured that the borders are made smooth and
FIGURE 16-5 Closed horseshoe-shaped major connector.
• It is rigid and derives good vertical support from bony palate.
• It resists torquing and bending stresses better, as it provides L-beam
• This provides excellent support, rigidity and retention.
• The anterior border is kept 6 mm away from the gingival margin or
should cover the cingula of all anterior teeth.
• There are three designs for this type of connector, which are as
(i) All acrylic resins: Connectors are made entirely
(ii) Combination of cast metal and acrylic resin:
Anterior portion of the denture is made up of
metal and the posterior portion of the denture is
(iii) All cast metal: Entire palate is covered with
• In class I and class II situations
• In cases of missing anterior as well as bilateral edentulous spaces
• In cases of poor ridge support or flabby tissues
• When opposing all mandibular teeth are present
• Cleft palate cases with a high-arched palate
• Excellent rigidity and support
• In cases of metal base, better perception of temperature changes
• Chances of papillary hyperplasia
Mandibular major connectors are one of the essential components of
mandibular partial denture. Unlike the maxillary major connectors,
mandibular connectors have limitation of space due to height of the
floor of the mouth, vestibular depth, location of the lingual frenum or
Desirable features of mandibular major connectors
• Rigidity of the major connector is the most important requirement.
• Relief is routinely required between the mandibular major
• Amount of relief required is determined by the type of RPD and the
lingual slope of the residual ridge.
• Minimum relief is given in tooth-supported partial denture,
whereas considerable relief is given in distal extension cases.
• If the lingual slope of residual ridge is almost vertical, minimum
relief is provided and if it slopes towards the tongue horizontally,
• In mandibular major connectors, beading is never given.
There are commonly five types of mandibular major connectors,
(iv) Kennedy’s bar or double lingual bar or continuous bar
• This is the most commonly used mandibular major connector.
• It is half pear-shaped in cross-section with the bulkiest portion placed
at the inferior border of the bar whereas the superior border is
• Thickness of the bar is 6 gauge half pear-shaped wax or plastic
pattern to ensure adequate rigidity.
• A minimum of 8 mm vertical space (space between the gingival
margin of the tooth and the active tissues of the floor of the mouth)
is required for the fabrication of lingual bar.
• The minimum thickness of lingual bar is 5 mm and the remaining 3
mm of space is essential to be left between the gingival margin and
• Active vertical space is best determined using a periodontal probe
when the patient is asked to protrude the tongue and make
• Lingual bar should be fabricated as inferior as the patient can
tolerate, as this increases the amount of space available for the
• For all partial denture designs, if adequate vertical space is
• As there is no contact with the teeth, no decalcification of tooth
• It is the simplest design with ease of fabrication.
• It results in minimal tissue contact.
• It is not used in cases with mandibular tori.
• It cannot be used where the vestibular depth is less.
• Insufficient available space can result in fabrication of flexible
• It is a modification of the lingual bar, as it is located more inferiorly
and is horizontally placed over the anterior floor of the mouth.
• Specialized impression is needed to record the depth and width of
• It can be used along with lingual plate in the presence of anterior
• In cases where the lingual sulcus is shallow or the available vertical
• Severe lingual tilt of remaining anterior teeth
• Decreased active vertical space
• It has same basic design as the pear-shaped lingual bar with an
added feature of thin metal plate extending onto the lingual surface
• Adequate relief is provided for soft tissue and bony undercuts.
• Also, the free gingival margin and the sulcus area should be
• Lingual plate has a scalloped design with the metal margin covering
the entire embrasure space extending up to the contact area.
• Chrome metal is the most preferred material for this type of
connector, as it can be used in thin sections.
• In cases of diastema between anterior teeth, cut backs or step back is
given in the design so as to hide the metal covering the cingula.
• In class I situation when there is excessive resorption of the residual
• When remaining teeth are periodontally compromised and require
• When there is insufficient space for the lingual bar
• When additional indirect retention is required
• Future replacement of one or more anterior teeth
• This is the most rigid mandibular major connector.
• It provides maximum support and stabilization.
• It helps in stabilizing periodontally compromised dentition.
• It prevents overeruption of mandibular anterior teeth.
• It has a better patient acceptability.
Chances of decalcification of tooth surface due to extensive coverage
of the teeth and soft tissues are there.
Double lingual bar or Kennedy’s Bar or ccontinuous Bar (fig. 16-
• It differs from the lingual plate in that there is no metal extension
below the superior margin of the plate and the lingual bar, thereby
exposing the lingual surface of the teeth and the interproximal soft
• It consists of a pear-shaped lingual bar attached to the thin metal bar
which is half oval in cross-section and is 2–3 mm high and 1 mm
thick at the greatest diameter.
• In case of diastema between anterior teeth, step back design is given
so as to avoid metal visibility.
• It is supported by rests on the either side of the connector on the
FIGURE 16-9 Double lingual bar.
• When there are large interproximal embrasure spaces
• When some degree of indirect retention is required
• It provides horizontal stabilization of the prosthesis.
• It provides indirect retention.
• It provides natural stimulation to the gingival tissues, as it is not
• Difficulty in accurate insertion of the prosthesis
• This is the only major connector which is located labially to the
• Its half pear-shaped design is similar to that of the lingual bar.
• Because of the arc, the labial bar is greater in length than the lingual
• When there is excessive lingual inclination of the mandibular
• Presence of large mandibular tori
• Presence of severe lingual tissue undercut
• It is uncomfortable to the patient.
• Bulk of the labial bar distorts the lower lip.
• It results in poor aesthetics.
Swing-lock partial denture was first described by Dr Joe J. Simmons in
1963. It consists of a hinged buccal or labial bar which can permit open
and close movements (Fig. 16-10).
• It has a small vertical projection arm that contacts the labial and
buccal surfaces of the teeth gingival to the height of contour.
• Labial bar can also be attached to acrylic resin components in those
cases where there is extensive loss of gingival tissues.
FIGURE 16-10 Swing-lock design.
• All the remaining teeth are used for retention and stabilization of
• It is relatively inexpensive treatment.
• It has questionable aesthetics.
• It puts excessive pressure on the distal most abutment teeth.
• In cases where remaining teeth are less in number and are mobile.
• In cases where teeth are lingually inclined.
• It provides retention and stabilization in cases where large number
of teeth and alveolar ridge are lost due to trauma.
• Chrome is the material of choice for fabricating metallic framework
of the swing-lock partial denture framework, as it provides
adequate rigidity and strength.
• Gold and gold alloys are not preferred, as they show considerable
Minor connectors are one of the components of the RPD, which are
connected to the major connector.
They are defined as ‘the connecting link between the major connector or
base of a removable dental prosthesis and the other units of the prosthesis,
such as the clasp assembly, indirect retainers, occlusal rests, or cingulum
• These connect the major connector with other parts of the denture
such as clasps, rest and indirect retainers.
• These transfer stresses to other components of the prosthesis.
• These transfer stress from the prosthesis to the abutment teeth and
• Minor connector should be rigid so that it can withstand functional
• It should be positioned in the embrasure areas between two teeth.
• It should be thickest lingually and should taper towards the contact
• There should be 5 mm (minimum) space between the two vertical
• These should contact the guiding planes of the abutment tooth or
teeth to facilitate its path of placement.
• These should provide enough space for teeth arrangement.
There are four types of minor connectors:
(i) Connector which connects the direct retainers (clasp assembly) to
(ii) Connector which connects the indirect retainers to the major
(iii) Connector which joins the denture base to the major connector
(iv) Connector which acts as an approach arm in bar-type clasp
Minor connector which connects the direct retainers to the major
• Design should be rigid and have adequate bulk to withstand
• Minor connector should lie interproximally.
• It should be broad buccolingually and thin mesiodistally to help in
arranging teeth in proper position.
• Minor connector is never placed on the convex lingual surface of the
Minor connector which connects the indirect retainers to the
• It should connect at right angle but the junction should be rounded.
• It should be designed in such a way that it lies in the embrasure
between the teeth so as to disguise the bulk.
Minor connector which joins the denture base to the major
• This type consists of two metal struts 12–16 gauge in thickness,
which extend longitudinally over the edentulous ridge.
• In the lower arch, one strut is placed buccally to the crest of the
ridge, whereas the other is placed lingual to it.
• In the upper arch, one strut is placed buccally to the crest, while the
other forms the border of the major connector.
• Smaller struts of 16-gauge thickness are placed in between the struts
and form a lattice-type design.
• One cross strut is placed for each tooth to be replaced.
• This type of design is used when multiple teeth are replaced.
• It provides the strongest retention of acrylic denture base to
• It is easy to reline the denture base in case of ridge resorption.
• Tissue stop is required in distal extension cases.
FIGURE 16-11 Lattice type minor connector.
• It consists of a thin metal sheet with multiple holes.
• It can be used in cases of multiple missing teeth.
• It is difficult to pack acrylic resin, as excessive pressure is required
to flow the resin dough through the holes.
• It does not provide as strong attachment to the denture base as the
• Tissue stop is required in distal extension cases.
• This type of design is used with metal denture base which directly
contacts the edentulous ridge.
• Projections on the metal denture base in the form of metal nail head
or beads are provided for direct attachment of acrylic resin and the
• It should be used on well-rounded and healed ridges.
• It is indicated in tooth-supported class III cases.
• Hygienic design and better soft tissue response are its advantages.
• Its disadvantage is that the resin attachment is weakest of all the
• Relining of the metal base is not possible.
Minor connector which acts as approach arm in bar clasp design
• This is the only minor connector which is not rigid.
• It should taper from origin to terminus.
• It should not cross the tissue undercut.
Internal and external finish lines in
Finish lines are essential in the type of minor connectors which join
the denture base to the major connectors. It is a definite line on the
cast framework where acrylic resin blends evenly with the major
connectors. Often a butt joint is given so that adequate space is
provided for acrylic resin. Also, it reduces the amount of stress at the
junction of metal and acrylic resin. Two types of finish lines are seen
in the cast framework, namely, internal and external finish lines.
• It is formed by relief wax given over the ridge area of the master
cast before duplication of the cast.
• This relief wax is 24–26 gauge thick and provides sufficient space for
acrylic resin to flow below the lattice-type or mesh-type minor
• Margins of the relief wax become the internal finish line which is
• This type of finish line is produced during the wax-up procedure
• It is sharp and well defined and forms an acute angle to produce
• This undercut is important to retain acrylic resin sufficiently
adjacent to the major connector.
FIGURE 16-12 External finish line in cast framework.
Rests are components of partial denture which transfer the forces
along the long axis of the abutment teeth and thus provide support.
They fit into the prepared tooth surface or restoration called the rest
Rest is defined as ‘a rigid extension of a fixed or removable dental
prosthesis that prevents movement towards the mucosa and transmits
functional forces to the teeth or dental implant’. (GPT 8th Ed)
Rest seat is defined as ‘the prepared recess in a tooth or restoration
created to receive the occlusal, incisal, cingulum, or lingual rest’. (GPT 8th
• These act as a vertical stop and prevent injury to the soft tissues.
• These direct the functional forces along the long axis of the tooth.
• These help to maintain the components of the partial denture in the
• Secondary or auxiliary rests serve as indirect retainer for distal
• These can provide reciprocation to the retentive clasp of the direct
• This is the part of the clasp assembly through which the fulcrum
• Primary rests fulfil most of the above-mentioned functions.
• These are also called auxiliary rests.
• These additional rests can provide indirect retention in distal
• These are placed as far anterior or posterior as possible to the
fulcrum line in order to prevent rotation of the prosthesis.
• For best mechanical advantage, the primary rest is located next to the
edentulous ridge and the secondary rest is located as far away from
the edentulous ridge as possible.
Types of rests used in partial dentures
Rests can be classified as follows:
(i) On the basis of location on the abutment (Fig. 16-13)
• Occlusal rest: Located on occlusal surface of the
• Cingulum or lingual rest: Located on the lingual area
• Incisal rest: Located on the incisal edge of the teeth
(ii) On the basis of its relation to the direct retainer
FIGURE 16-13 Diagram showing three forms of rests: (A)
occlusal rest; (B) canine rest; (C) incisal rest.
• This is located on the occlusal surface of the posterior teeth.
• Outline form of the rest is triangular with base of the triangle
towards the marginal ridge and rounded apex towards the centre.
• Size of occlusal rest is one-half of the buccolingual width measured
from cusp tip-to-cusp tip and one-third to one-half the mesiodistal
• Floor of the occlusal rest should be directed towards the centre of
the tooth and should form an acute angle to effectively transmit the
• If the angle is more than 90°, the forces are not transmitted vertically
but are subjected to inclined plane effect.
• This effect tends to slide the prosthesis away from the abutment
tooth and thus compromising the retention and stability of the
• The marginal ridge should be sufficiently reduced to avoid breakage
• The rest should be at least 1.0–1.5 mm thick at the marginal ridge
region and at least 0.5 mm thick at the thinnest point.
• It is usually placed on the maxillary canines.
• It is not preferred on the mandibular canine, as the thickness of
enamel is not adequate and has steeper lingual slope.
• It is always preferred to the incisal rest, as it is closer to the centre of
rotation and the proper cingulum rest directs the forces along the
• Rest seat of the cingulum rest is an inverted V-shape and the apex is
• All the line angles should be rounded and the cingulum rest is placed
• The outline form is crescent or half moon shaped.
• Occlusal rest is preferred to the cingulum rest, as it has better
• Quasicingulum rest is given on the mandibular first bicuspid which
• It is usually placed on the mandibular canines.
• Incisal rest is not preferred to the incisors, as this may tend to tip the
• It is a V-shaped notch located 1.5–2.0 mm from the proximoincisal
angle of the tooth with its deepest part located towards the centre.
• It is placed on the incisor teeth to provide stabilization and splinting
• The incisal rest is placed on the distoincisal angle on the lingual
surface because of aesthetic reasons.
Direct retainers and intracoronal
Direct retainer is defined as ‘that component of a partial removable dental
prosthesis used to retain and prevent dislodgement consisting of a clasp
assembly or precision attachment’. (GPT 8th Ed)
Direct retainers can be classified as follows:
(i) Extracoronal retainers: Retentive clasp assembly or external
(ii) Intracoronal retainers: Internal or precision attachment
• The principle of internal attachment was first given by Dr Herman
• The retainer consists of male and female components (key and
keyway) which are either custom made or prefabricated (Fig. 16-14).
• Female part acts as a receptacle and is located within the crown and
the male component is attached to the RPD.
• Retention is achieved by wedging or binding action of the prosthesis
against the vertical dislodging forces.
FIGURE 16-14 Diagram showing intracoronal retainer.
• Aesthetically superior to the extracoronal attachments, as visible
• Provides horizontal stabilization
• Prone to wearing of the component parts
• Costly and requires precision in fabrication
• Complicated laboratory procedure
• Young patients with large pulp horns
Clasp assembly is defined as ‘the part of a removable dental prosthesis that
acts as a direct retainer and/or stabilizer for a prosthesis by partially
encompassing or contacting an abutment tooth-usage: Components of the
clasp assembly include the clasp, the reciprocal clasp, the cingulum, incisal or
occlusal rest, and the minor connector clasp’. (GPT 8th Ed)
Parts of the clasp assembly (Fig. 16-15):
• Rest: It provides vertical support.
• Body: It connects rest and shoulder of clasp to minor connectors.
• Shoulder: It connects body to clasp terminal.
• Reciprocal arm: It must be rigid and should lie above the height of
• Retentive arm: It consists of shoulder and retentive terminal; it lies
• Retentive terminal: It lies below the height of contour and provides
• Minor connector: It connects body of the clasp to other parts of the
• Approach arm: It is a component of the bar clasp; it is the only minor
connector which can be flexible.
FIGURE 16-15 Diagram showing parts of clasp assembly.
Requirements of the clasp assembly
The clasp assembly should satisfy the following requirements:
Retention: Retentive terminal of the retentive arm is flexible and lies in
the undercut region and provides retention to the prosthesis.
• The amount of retention depends on the flexibility
of clasp arm, depth of the undercut and the length
of the clasp arm below the height of contour.
• Retentive undercut for cast chrome metal is 0.010 inch,
for wrought metal it is 0.020 inch and for cast gold it is
• Clasp flexibility depends on length, diameter, taper,
cross-sectional diameter and the material.
• Clasp flexibility is directly proportional to the cube of
• It is inversely proportional to the diameter of the
• Round clasp has greater flexibility, as it can flex in
all the spatial planes in comparison to the halfround clasp which can flex only in single plane.
Stability: All components of the clasp, except the retentive terminal,
provide stability to the prosthesis.
• Circumferential clasp provides the maximum
stability because of its rigid shoulder.
Support: Rests (occlusal, cingulum or incisal) provide the vertical
Reciprocation: It is provided by the reciprocal arm which is positioned
opposite to the retentive arm.
• The reciprocal arm should be rigid and should
always lie above the height of contour.
• It should touch before the retentive arm touches
• It stabilizes the denture against the horizontal
Encirclement: Each clasp should encircle more than 180° of the
• Continuous encirclement, as in the case of
• Discontinuous or broken encirclement, as in the
case of bar clasp which must have at least threepoint contact on the tooth surface.
Passivity: Clasp should be passive when seated completely.
• It should not exert any pressure onto the tooth
unless dislodging force is applied during removal
Circumferential clasp or Akers’ clasp is defined as ‘a retainer that
encircles a tooth by more than 180°, including opposite angles, and which
generally contacts the tooth throughout the extent of the clasp, with at least
one terminal located in an undercut area’. (GPT 8th Ed)
It is indicated in tooth-supported RPDs (class III and class IV).
• It is easy to fabricate and design.
• It has less chances of food lodgement.
• It provides excellent support, bracing and reciprocation.
• It covers a large surface of the abutment tooth, and there are more
chances of decalcification of tooth structure.
• It can change the morphology of the abutment tooth.
• It is difficult to adjust with pliers because of its half-round
• It always originates above the height of contour.
• The retentive arm should extent cervically and circumferentially in a
• The retentive terminus should pass over the height of contour and
enter the infrabulge portion of the abutment to engage in the desired
• Reciprocal arm should be located on the opposite surface of the tooth
and should be located above the height of contour.
• Retentive terminus should always be directed towards the occlusal
surface and never towards the gingiva.
• Retentive arm should be directed as apically as possible on the
• It should terminate at the mesial line angle or distal line angle and
never at the midfacial or midlingual surfaces.
• The retentive clasp should be kept as low on the tooth as possible
because in this position, it provides better mechanical advantage
Types of circumferential clasp:
(iv) Embrasure clasp or modified crib clasp
(vi) Fishhook or hairpin clasp
FIGURE 16-16 Design features of circumferential clasp.
Types of circumferential clasp
Types of circumferential clasp are described in the following
• It is the most simple and versatile clasp design.
• It is mostly indicated for tooth-supported partial dentures.
• The clasp approaches the undercut from the edentulous area.
• The retentive undercut is located away from the edentulous area
FIGURE 16-17 Simple circlet clasp.
• It provides satisfactory support, stabilization, reciprocation,
• It cannot be used in the anterior region owing to aesthetic reasons.
• It cannot be used in distal extension cases.
• It covers greater surface area of the tooth.
• It can be adjusted only buccolingually and not occlusogingivally.
• It is also called reverse approach circlet clasp.
• The retentive undercut is located next to the edentulous area, i.e. the
• Mesio-occlusal rest is provided and retentive terminal terminates in
• It is used in distal extension cases where the bar clasp is
• Bar clasp is contraindicated when there is soft tissue undercut due to
buccoversion of the abutment tooth or when there is an undercut
• It resists the torsional forces better.
• It can be used in distal extension cases where bar clasp is
• It provides better retention and stability because of location of the
• In cases where the occlusal clearance is not sufficient, the thickness
of the clasp is reduced and this may compromise the strength of the
clasp. An additional occlusal rest is needed next to the edentulous
area in order to protect the marginal ridges of the abutment tooth
and prevent food lodgement between the tooth and the denture.
• As the clasp runs from the mesial to the distal surface, it gives poor
aesthetics and is not used in premolars.
• Wedging may occur between the abutment and the adjacent tooth, if
the occlusal rests are not prepared properly.
Multiple circlet clasp (fig. 16-18)
• This is a combination of two simple circlet clasps joined at the
terminal ends of the reciprocal arms.
• It is primarily used to share retention between multiple teeth.
• It is indicated when the primary abutment has compromised
• Mode of splinting periodontally compromised teeth by RPD.
• Its disadvantages are similar to the simple circlet and reverse circlet
FIGURE 16-18 Multiple circlet clasp.
• It is also called modified crib clasp.
• It consists of two simple circlet clasps joined at the body (Fig. 16-19).
• It is mostly used on the side of the arch where there is no edentulous
• This type of clasp crosses the marginal ridges of two teeth and
engages the undercut on the opposing line angles on both the teeth.
• Adequate tooth structure is removed from the buccal inclines of
both the teeth to provide adequate space for metal thickness of the
• It is indicated in unmodified Kennedy class II and class III cases.
• It has two retentive arms and two reciprocal arms either bilaterally
• It may be possible to close a small edentulous space by a modified
embrasure clasp called the pontic clasp.
• Frequent fracture of clasp may occur because of insufficient metal
• Two occlusal rests are necessary; otherwise, there will be tendency
for food lodgement or even separation of the teeth.
• This type of clasp encircles nearly all the tooth surface from its point
• It is indicated on the tilted molars (maxillary molars tilt
mesiobuccally and mandibular molars tilt mesiolingually).
• The ring clasp is used when the proximal undercut cannot be
• It engages the proximal undercut by encircling the entire tooth from
point of origin. Like in tilted mandibular molars, it approaches from
the mesiobuccal surface and terminates in the infrabulge region of
the mesiolingual surface. Reverse is seen in cases of tilted maxillary
• Because of its greater length, the clasp requires an additional
support in the form of additional bracing arm (minor connector)
FIGURE 16-20 Ring clasp with auxiliary bracing arm for
• When buccinator muscle attachment is close to the lower molar
• In cases of soft tissue undercut which must be crossed by the
• Large surface area of tooth is covered.
• It is difficult to adjust and repair.
• Contour of the crown is drastically altered.
Fishhook or ‘C’ or Hairpin clasp
This type of ‘C’ clasp is a form of simple circlet clasp which after
crossing the tooth surface loops back into the retentive undercut
below the point of its origin (Fig. 16-21).
• Upper part of the clasp is rigid and the lower part is flexible.
• This clasp design is used on the tooth with sufficient clinical crown
FIGURE 16-21 Hairpin or fishhook clasp.
• Retentive undercut is located next to the edentulous area or adjacent
• In cases where bar clasp cannot be used because of soft tissue
• In cases where reverse circlet clasp cannot be used because of
insufficient occlusal clearance.
• Large surface area of tooth is covered.
• It is prone to food lodgement.
• It results in poor aesthetics.
• It is an extended occlusal rest with buccal and lingual clasp arms.
• Indicated where the occlusal surface of one or more teeth is below
occlusal plane and is restored with an onlay.
• Onlay clasps are indicated in caries-resistant mouth.
• It covers a large surface area of tooth and may lead to enamel
• If the onlay is made of cobalt–chrome alloy, the opposing occlusion
should be fabricated with acrylic resin or gold crown.
• It consists of flexible retentive arm made of wrought wire and cast
• A cast circumferential clasp should not be used to engage the
mesiobuccal undercut adjacent to the distal edentulous space
because it tends to produce damaging torsional forces on the
• In such cases, the retentive arm is made of wrought wire which
• It can be placed in deeper undercuts.
• It has higher flexibility, as it can flex in all the planes.
• It has a thin line contact rather than surface contact and is, therefore,
• It requires additional steps in laboratory procedure.
• It has a tendency to break or distort.
• It has poor stability or bracing property.
• It consists of retentive arm originating from one direction and the
reciprocal arm originating from the other (Fig. 16-22).
• The retentive arm is joined to the occlusal rest by a minor connector
on one side and the reciprocal arm is joined by another minor
• In order to avoid large coverage of tooth surface, the reciprocal arm
can be made in the form of short bar or auxiliary occlusal rest.
• Thus, clasp design provides dual retention and is indicated in
unilateral partial denture designs.
FIGURE 16-22 Half and half clasp.
• It is a modification of ring clasp.
• In this design, the occlusal rest is left unsupported and the minor
connector is given at the end of the clasp arm.
• Its greatest disadvantage is that the occlusal rest is left unsupported
and thus this design cannot provide adequate support to the
Gingivally approaching clasp or bar clasp is defined as ‘a clasp retainer
whose body extends from a major connector or denture base, passing adjacent
to the soft tissues and approaching the tooth from a gingivo-occlusal
Bar clasp is also called vertical projection clasp, infrabulge clasp
• It approaches the undercut or retentive area from the gingival
• ‘Push’ type of retention is seen here, whereas ‘pull’ type of retention is
provided by the circumferential clasp.
• Push type of retention is more effective than the pull type of
• It has a flexible minor connector called the approach arm.
• It provides limited bracing action because of limited three-point
• The approach arm should cross the free gingival margin at 90° and
should not impinge the soft tissues and should uniformly taper
from the origin to the clasp terminus.
• The bar clasp should be placed as low on the tooth surface as
• This type of clasp is used when the retentive undercut is adjacent to
FIGURE 16-23 Gingivally approaching clasp.
• Push-type retention is more effective than pull-type retention of the
• This type of clasp is easier for the patient to insert but difficult to
• It is aesthetically superior to circumferential clasp, as it approaches
• It is less prone to caries, as it has limited three-point contact on the
• It has a tendency of food lodgement.
• It provides less bracing action and stability due to increased
flexibility of the retentive arm.
• Additional stabilizing units are needed.
• It cannot be used when there is a shallow vestibule.
• It cannot be used in cases of excessive buccal or lingual tilt of the
• In case of small undercut (0.01 inch) which exists in the cervical
third of the abutment tooth and is approached from the gingival
• In tooth-supported partial dentures or modification areas
• In distal extension cases where use of cast circumferential clasp is
contraindicated due to aesthetic reasons
• In cases of deep cervical undercut or soft tissue undercut which
• If the retentive undercut lies away from the edentulous space in the
• It is mostly used in combination of cast circumferential reciprocal
• It is usually used in distal extension cases where retentive undercut
is present towards the edentulous ridge (distobuccal undercut) (Fig.
• The nonretentive arm of the ‘T’ clasp lies above the height of
contour and the retentive arm lies into the retentive undercut. But
both the arms should point towards the occlusal surface.
• It should not be used in cases where the undercut is located away
• It can be used in tooth-supported partial denture cases with natural
undercuts. As natural undercuts are used without creating new
ones, it is referred to as the clasping for convenience.
• This type of clasp should not be used where the soft tissue
• Also, ‘T’ clasp should not be used, if the retentive undercut is
located close to the occlusal surface. This will encourage food
lodgement and will be unaesthetic in appearance.
• It is similar to the ‘T’ clasp, except the removal of nonretentive arm.
• It is mostly used on canine and premolar for aesthetic reasons.
• It normally does not provide the 180° encirclement of the abutment
• This type of clasp design is similar to the ‘T’ clasp.
• It is indicated when the survey line is high in the mesial and distal
line angles but low in the middle of the facial surface.
• It is mostly used on the distobuccal surface of the upper canines
• As only the tip of the retentive clasp contacts 2–3 mm of the area,
the horizontal stability and encirclement is diminished.
• It is a modified I type bar clasp which was first introduced by F.J.
• It consists of ‘I’ bar retainer, long guide plane and the mesial rest.
• Rest should be of sufficient bulk to provide maximum vertical
• In distal extension cases, rests are placed on the mesial aspect of the
abutment tooth because tipping forces are directed mesially and the
prosthesis moves into firm contact with support of anterior teeth.
• Also, anterior placement of the rest helps in verticalizing the force
• The long guide plane (proximal plate) provides horizontal stability
and reciprocation and helps in distributing the functional forces
• Proximal plate helps in distributing the forces throughout the arch
and helps in improving the retention of the prosthesis.
• The ‘I’ bar retainer should engage the undercut passively and help
in resisting vertical displacement.
• However, this type of clasp design provides less horizontal stability
and retention than other retentive elements.
• As the tooth contour is not altered, chances of food lodgement are
• RPI concept is the modification of ‘I’ bar retainer system proposed
• It was first developed by A.J. Kroll in 1973.
• This design concept was based on the principle of minimizing stress
by minimal tooth and gingival coverage.
• It consists of mesial rest, proximal plate and ‘I’ bar (Fig. 16-25).
• The mesial rest extends only into the triangular fossa even in the
• In the canine region, it is confined to the mesial marginal ridge in
the form of concave circular depressions and not to the entire
• The guide plane is prepared about 2–3 mm high occlusogingivally
and the proximal plate contact only 1 mm of the guide plane in the
• The reduction of the proximal plate is believed to improve the
• ‘I’ bar is designed as pod shaped to allow more tooth coverage.
• It is placed more towards the mesial embrasure space so as to
• Functional forces on the distal extension base tend to disengage the
retentive tip into the mesial embrasure space.
• It is also called the self-releasing clasp.
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