Swing lock partial denture/ oral surgery courses

SWING LOCK
PARTIAL DENTURE
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Introduction
This denture was first described and documented by
Simmon’s in 1963.
The concept was recommended for maximizing stability
and retention by gaining access to many more teeth surfaces
with the unique clasping mechanisms offered by incorporation
of the lock, hinge and gate assembly, allowing all teeth to
become primary abutments.
This denture has a labial bar in addition to the lingual
major connector. The labial bar extends labially all along the
arch and is attached to the remaining parts of the denture by a

Indications
There are a number of indications for use of the swing-lock design in
the treatment of partially edentulous patients
• Too few remaining natural teeth for a removable partial denture of
conventional design.
• Remaining teeth too mobile to serve as abutment teeth for
conventional design.
• Position of remaining teeth not favorable for a conventional design.
• Retention and stabilization needed for maxillofacial prostheses such
as obturators for post surgical patients.
• To retain prosthesis for patients who have lost large segments of
teeth and alveolar ridge through traumatic injury.

Contraindications
Shallow vestibule
Depth of labial vestibule should be 6 to 8 mm to accommodate the
labial bar. A zone of attached gingiva between 2 and 4 mm apical to
the gingival sulcus is advisable for a favourable long term prognosis.
A shallow vestibule can be surgically modified with a vestibular
extension and a free gingival graft. The lack of attached gingiva can
be corrected with a free gingival graft or an apically repositioned flap
procedure.
Extended frenum
A frenum that extends to a shallow zone of attached gingiva has the
potential of future irritation by the labial bar. An. extended frenum
should be removed surgically and a free gingival graft placed at the
site of the frenum.

Esthetic requirements
Some patients have a prominent lip line, thus, showing gingiva at the
necks of the teeth when smiling or speaking. In these situations, the
occasional display of metal may be unacceptable to the patient. Some
authors have suggested that a veneer of acrylic resin be processed to
the labial bar of the swing lock to improve the esthetics.
Poor plaque control
Regardless of the type of removable partial denture placed, retention
of plaque may become a problem. This is especially true for a swing
lock removable partial denture, since a great deal of tooth surface is
contacted by partial denture. Thus... patients with poor hygiene
maintenance are poor candidates for a swing lock removable partial
denture.

Advantages
The primary advantage of the swing-lock concept of treatment is
that it provides a relatively inexpensive method of using all or most
of the remaining teeth for the retention and stabilization of a
prosthesis. Alternatives to this type of treatment include:
1. Removal of the remaining teeth and
2. Fixed splinting of the remaining teeth and con-struction of a
conventional removable partial denture.
The latter is relatively time consuming and expensive and presents
problems if one of the splinted teeth fails. Loss of a splinted tooth
could necessitate removal and reconstruction of a fixed splint,
whereas a tooth can be removed and added to the major connector
of swing-lock prosthesis through a simple laboratory pro-cedure.
Because the construction of a swing-lock remov-able partial denture
is relatively simple and inexpen-sive, it can be used in situations for
which more con-ventional types of treatment may appear hopeless.www.indiandentalacademy.com

Disadvantages
• A swing-lock prosthesis can produce a relatively poor esthetic result
for patients with short or extremely mobile lips.
• Obtaining perfect adaptation of a resin veneer is difficult because the
path of insertion is dictated by the hinge movement of the labial bar.
• The remaining teeth are grasped firmly by the prosthesis.
• A long distal extension base is likely to move toward the tissue under
the forces of occlusion. This movement can tip the teeth grasped by
the prosthesis.

TREATMENT PLANNING
When the swing lock removable partial denture is considered the
position of the lips during smiling is recorded and transferred to the
primary diagnostic casts. A facial sulcus depth of 6 to 8 mm is
recommended for placement of the retentive gate element. A high
frenal attachment and / or shallow sulcus requires surgical
correction prior to making a working impression.
Periodontal health is a prerequisite to therapy unless the prosthesis
is considered an interim measure for the informed patient or is used
as a provisional/ definitive prosthesis as periodontal therapy is
provided.

The diagnostic cast is surveyed to plan further tooth
preparation, including guide planes and rest seat and to
establish clasp placement.
The desired tooth modifications may be achieved by
reshaping the teeth, or when castings are indicated by
incorporating the desired contours, into the restorations.
Following mouth preparation a working impression is
made.
Irreversible hydrocolloid in a selected rimlock tray has
often proved adequate .Mobile teeth indicate the use of
reversible hydrocolloid to avoid any tooth displacement.

Conventional laboratory procedures are followed. The cast is
poured with a compatible vacuum mixed dental stone. A wax
occlusal rim with an acrylic resin base can be fabricated on the
working cast, a facebow transfer and occlusal registration record are
obtained, and casts are mounted on a semiadjustable articulator.
The tooth mold and lock are established according to the patient's
preference to use a finger/ thumb of the left or right hand.

Fabrication of a swing lock partial denture
It includes the following steps :
• Selection of Metal for Swing-lock Framework
• Surveying and Design
• Selection of Impression Material
• Tray selection
• Making the Impression
• framework fabrication
• fitting the framework
• jaw relations
• occlusal development
• insertion
• post insertion care

Selection of Metal
Chrome alloy is chosen instead of gold alloy. This is because gold
alloy shows wear (due to constant movement of the hinge) after a
short time of use. If gold alloy is to be used a greater deal of metal
has to be incorporated into the framework to increase rigidity and
strength.
Surveying and Design
The cast is mounted on a surveyor with the occlusal plane parallel
to the base and surveyed . The path of insertion is from a lingual
direction with the labial arm open..

Design considerations to be followed
for each part of the denture :
Lingual plate: It should be designed to end above the survey line
and hence it prevents the tissue ward displacement of the denture.
Occlusal rest : The occlusal rests also help to prevent tissue
ward displacement of the denture.
Major connector: The mandibular major connector of choice is a
lingual plate. It extends above the survey line with scallops
extending up to contact points. The maxillary major connector of
choice is a complete palate or a closed horseshoe with borders
extending up to or above the survey line.

Labial arm design :The vertical projections of the labial bar should
be designed to touch the teeth below the height of contour. Hence,
they prevent occlusal movement.
The design of the labial arm can be of two types:
Conventional design: It consists of a labial bar with metallic vertical I-
bar or T-bars attached to it. They contact the teeth below the survey
line.
Using acrylic resin retention loops: It is indicated for patients with
short or hypermobile lips and where aesthetics is of concern. The
acrylic loops are translucent or tooth colored hence, they are more
aesthetic.
Rests are placed on teeth adjacent to the edentulous ridge.
Placement of hinge is determined by the patient comfort.

Selection of Impression Material :
Alginate is the impression material of choice. Large gingival
embrasures and gingival recession will usually be present in these
cases, the impression material should tear in the interproximal areas
during removal. This will allow easy removal of the impression without
any damage to the teeth. This is not possible in rubber base impression
materials. Heavy bodied Alginate is preferred.

Making the Impression.
Impression procedure for swing lock dentures is similar to
conventional dentures.
Dual impressions may be required for distal extension cases.
Framework Fabrication
A master cast is poured from the secondary impression. The
master cast is waxed and undercuts are blocked out before
duplication. The master cast is duplicated to form the refractory
cast. The design of the denture is transferred to the refractory cast.
After design transfer, the wax pattern is fabricated on the refractory
cast .
The refractory cast is invested, wax is burned out and casting is
done. The resultant framework is trimmed, finished and polished.

Tray Selection:
A custom tray is essential for recording maximum labial
and buccal vestibular depths.
Secondary impression procedures should be carried out.
About 5 to 6 mm spacing should be present between the
teeth and the tray when placed in the mouth.
Holes should be made in the tray to help retain the
alginate.

Fitting the Framework.
A framework is tried in the patient before arranging the artificial
teeth.
The procedure is similar to that done for conventional removable
partial dentures except that the fit of the labial bar and the rest of the
framework are checked separately.
Jaw Relations
After framework try-in, a temporary denture base is fabricated using
the framework. Occlusal rims are fabricated over the temporary
denture base.The framework with the temporary denture base and
occlusal rim is inserted into the patient's mouth and all the three jaw
relations are recorded After jaw relation, the casts with the jaw
relation records are mounted in an articulator.

Arranging Artificial Teeth to Occlusion
Occlusion should be such that no lateral forces act on the prosthesis
during occlusion.
Simultaneous contact between natural and artificial teeth should be
present.
These factors are checked during denture try in.
After arranging the artificial teeth, the modelling wax that is to form
the denture base is contoured and polished .
Consecutively the trial denture is flasked and acrylized as usual.

Insertion
A lingual path of insertion is used.
Pressure indicator paste is used to detect pressure areas.
Occlusion is evaluated in centric and eccentric relations.
In case of distal extension RPD, the vertical projections
should be bent away from the teeth so that the anterior teeth are not
tipped lingually by the labial bar under occlusal load.
Post-insertion Care
Oral hygiene measures must be emphasized.
Distal extension RPD has to be frequently relined.
Loosened lock mechanisms should be tightened.
Teeth can be added to the frame work at later stages after the
removal of any tooth .www.indiandentalacademy.com

SWING LOCK PARTIAL DENTURE

Swing lock partial denture/ oral surgery courses

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