A removable partial denture is a removable prosthetic appliance which replaces one or more missing natural teeth. It is also called an RPD.
What Does a Removable Partial Denture Do?
A removable partial denture is meant to do the following.
- A partial denture restores the aesthetics or appearance of the face.
- RPD preserves the space of the missing teeth by preventing overeruption or tilting of neighboring teeth.
- Helps in improving speech in people with few missing teeth, especially the front ones.
- Improves function by aiding in the eating process.
- Helps the individual to transit easily from partially edentulous to completely edentulous stage.
- Helps in the distribution of occlusal loads or the bite load evenly.
Removable Partial Denture Drawbacks
Due to the design of the removable partial denture, there are certain disadvantages to its use. Following are some of the most common ones which may occur due to poor oral hygiene practices and due to the design limitations of the partial denture.
- Use of a removable partial denture may increase the risk of dental caries beneath the clasp components.
- It also increases the chance of plaque accumulation
- May result in the development of Gingivitis or periodontitis if oral hygiene isn’t maintained properly.
- Gingival recession in the tooth with the clasps
- Clasps can be unaesthetic when placed on visible tooth surfaces.
- RPDs may also increase the occlusal load on the abutment teeth.
Design of a Removable Partial Denture
The dentist designs the partial denture depending on certain factors, available edentulous (toothless) space being the important one.
Dr. Edward Kennedy has put forward a classification based on the different types of edentulous spaces present.
- Class I – Bilateral free end saddles(saddle=edentulous space)
- Class II – Unilateral free end saddle
- Class III – Unilateral bounded saddle
- Class IV – Anterior bounded saddle(across the midline)
Except for class IV, any other additional saddles are referred to as modifications, which were put forth by Applegate.
This classification helps the dentist in choosing the type of edentulous space present in that individual.
The dentist must also look for a well-motivated patient, who can maintain good oral hygiene.
Components of the Removable Partial Denture
A removable partial denture has different components. The design of the prosthesis will vary according to the individual’s need.
This is the part of the alveolar ridge from which the teeth are missing.
The saddle area can either be
- Mucosa borne
- Tooth borne
- Tooth and mucosa borne.
The saddle area is either made with a completely acrylic base or has a framework of metal with an acrylic covering on which the artificial teeth will be placed.
The major connector is the part which connects the parts of the denture together.
A major connector should have the following features.
- It should not impinge gingival tissues.
- During the placement and removal, there should be no bony or soft tissue prominences.
- It should be made from a biocompatible alloy.
- It should not interfere with the movement of the tongue.
- It should not cause any food trap.
- It should support and stabilize the prosthesis.
Major Connector Types
There are types of major connectors for the upper and lower arch.
- For the upper arch(maxilla)
- Anterior palatal bar
- Mid palatal bar
- Posterior palatal bar
- Palatal horseshoe connector
- Full coverage palatal plate
- For lower arch(mandible)
- Lingual bar
- Lingual plate
- Continuous clasp
- Buccal bar
- Sublingual bar
The minor connector is a small part which joins the clasp assembly, indirect retainers or rests, to the main denture framework or the major connector.
Tissue stops are part of the minor connector designed for retention of the acrylic resin bases. They provide stability to the framework and also prevent any distortion during the processing of the denture.
These stops are usually placed on the buccal or lingual slopes of the residual ridges and have a mesh-like design.
A retainer is part of the prosthesis like an attachment or clasp used to fix or retain the prosthesis and resist displacement away from the alveolar ridge.
There are two types of retainers.
Direct and indirect.
Direct retainers are of two types.
- Intracoronal retainer
- Extracoronal retainer
Intracoronal retainers are attached within the natural contours of an abutment tooth (tooth which supports the partial denture). This type is usually composed of prefabricated retainers.
Extracoronal retainers use mechanical resistance to displacement by the parts placed on or attached to the external surfaces of an abutment tooth.
- Dalbo attachment or spring-loaded plunger
- Flexible clips or rings that are attached to the abutment tooth.
- Clasp type of retainer which engages the external surface of an abutment tooth.
The terminal tip of the clasp arm is either placed in depression prepared on the abutment or below the greatest convexity of the tooth.
Claps type is the most commonly used retainer. The clasp assembly consists of
One or more minor connectors from which the clasp unit originates a rest,
a retentive arm which engages the undercut at its terminal area and a
Types of clasps
- Circumferential clasp
- Ring Clasp
- Back action clasp
- Multiple clasps
- Embrasure clasp
- Half and half clasp
- Reverse action clasp
- Bar Clasp
- Combination clasp
An indirect retainer consists of one or more rests and the minor connectors.
It prevents the movement of a distal extension base away from the tissues.
The rest is a part of the denture that is placed on an abutment tooth to provide vertical support. The rest seats are prepared on the abutment teeth according to the design.
The rest limits the movement of the denture vertically and distributes the functional forces of the tooth.
There are types of rests depending on the location.
- Occlusal rest
- Lingual rest
- Incisal rest
Artificial teeth may be acrylic or porcelain.
Clinical Steps Involved in RPD Fabrication
Following are the clinical steps involved in the fabrication of an RPD.
History Taking and Clinical Examination
History taking and complete oral examination will be done by the dentist.
The oral examination is done for detecting the presence of dental caries. The condition of existing fillings will be examined by the dentist. The periodontal condition of the remaining teeth will also be assessed by the dentist.
The type of ridge, occlusal relations, the inter-arch space needs to be evaluated at this stage by the dentist, as the design of the partial denture needs to be planned.
The dentist also carries out a vitality test of the remaining teeth.
Impression for a diagnostic cast will be made using irreversible hydrocolloid material (alginate)in a perforated impression tray.
Diagnostic casts are made with stone. These casts help in diagnosis and treatment planning. Casts may be mounted for better analysis.
A dental cast surveyor is used by the dentist for determining the path of insertion and removal of the partial denture prosthesis. A dental cast surveyor is an instrument used to determine the relative parallelism of two or more axial surfaces of teeth or other parts of a cast of the dental arches.
The Mouth Preparation
The dentist will attend to any issues regarding the other teeth or oral tissues before the patient receives the partial denture.
Extraction of the grossly non-restorable tooth, residual root or mobile tooth may be done at this stage. Any impacted teeth may need surgical removal.
Bony enlargements or tori which may hinder the framework may need to be removed priorly. Sharp bony ridges or spicules may need rounding off or smoothening.
Scaling and root planning may be needed. The dentist may restore the abutment tooth by repairing or refilling.
Abutment Teeth Preparation
The dentist will plan the design of the framework with the help of diagnostic casts.
The dentist will plan the location of the rest seats, the path of insertion, blocking of undercuts, alteration in the contours of the teeth, and the type of framework.
The abutment teeth with or without fillings are then prepared as follows.
- The proximal surfaces should be prepared parallel to the path of insertion.
- The contours of the teeth may need modification to receive the clasp tip and the arm.
- Before preparation of the rest seat, impressions are made and casts are done.
- These casts are then placed on the surveyor to determine the adequacy of axial alterations.
- If needed, axial alterations are done.
- The occlusal rest seats should be prepared such that the occlusal forces should be along the long axis of the abutment teeth.
There are different types of preparation depending on the case.
- Inlay preparation
- Crown preparation
- Crowns with ledge or shoulder
- Veneer crowns
- Spark erosion
Primary Impression for the Removable Partial Denture
The dentist selects a suitable sterilized perforated impression tray using elastomeric impression material to make an impression of the prepared mouth.
The impression is sterilized and the cast is poured immediately. Then it is sent over to the laboratory for making special trays for master impression.
The special trays are then used to record a master impression. The occlusal relationship has to be recorded using record blocks to obtain a balanced bite on both sides and enhance the stability of the denture.
Artificial teeth selection will be done at this stage. Then it is sent over to the laboratory for fabrication of a trial denture.
Chairside try in is done by the dentist to confirm the occlusal registrations done in jaw relation. The adjustments of occlusion of artificial teeth versus normal teeth are done.
The path of insertion and removal are evaluated. The speech is assessed. Once the dentist is satisfied with the outcome, the trial dentures are sent to the lab for fabrication of the final prosthesis.
The final fabricated prosthesis is placed in the patient’s mouth and all the records are reconfirmed.
Finally, post insertion advice is given by the dentist.
Post Insertion Care
The individual may need time to get adapted to the new prosthesis. The process of placing the removable partial denture inside the mouth and taking it out may need practice.
Also, there may be discomfort while speaking with the prosthesis which may eventually disappear.
There may be some amount of discomfort or soreness for a few days initially.
If there is pain or ulceration please visit the dentist.
Keeping the denture and the mouth clean is very important.
The denture needs to be cleaned after every time you eat (rinsing may also suffice) and also every day before sleeping using a brush, soap, and water.
But remember not to brush vigorously the inside of the denture. And also keep a separate brush for this purpose. The denture needs to be placed in a box of water every night before sleeping.
The abutment teeth need regular follow up to check for any cavities or other issues.
The denture may need repair or relining in the future. So following up with your dentist on a regular basis is vital.