Lec. 10 .زينب دالجمالي

Initial Placement, Adjustment, and Servicing of the RPDInitial placement of the completed removable partial denture, the fifth of six essential phases

of removable partial denture service, the insertion visit is include :

1. Final inspection of the prosthesis before insertion.2. Verifying the RPD framework fit.3. Assessment of acrylic resin denture base adaptation.4. Assessment of peripheral extension of the denture base.5. Evaluating occlusion.6. Adjusting retentive clasp assembly.7. Providing instructions for the patient in the use &care of the prosthesis.

Final inspection of the prosthesis:

Prior to the insertion appointment, the dentist should check &adjust the following:

1. Nodules of acrylic resin on the tissue surface of the prosthesis: the simplest way to locate these nodule is to run a finger over the intagllio surface(tissue surface) of the prosthesis. Once identified &marked, the nodules can then be removed with a small, acrylic bur mounted in a slow-speed hand piece. When the nodule removed do not polished the tissue surface.

2. Surface and internal porosity in the acrylic resin reduces both the quality &ultimate strength of the completed RPD. A porous surface will be difficult to keep free of dental plague. A rebase of the RPD is recommended.

3. Evaluate the denture- tooth acrylic resin junction. If the junction of the denture- tooth &acrylic resin denture base is improperly contoured &finished after processing, any crevices left in this area will become a potential site of food entrapment or staining.

4. Examine the acrylic resin/metal framework junction. The junction should be abut (900) joint with no overlap of the acrylic resin onto the metal framework. All the acrylic resin flash should be removed so there is a smooth, continuous exactly duplicate the borders recorded in the transition between the materials.

5. examine denture teeth for fractures that may have occurred during the processing or finishing procedures. Replace fractured teeth before the RPD is inserted.

6. Finally ,inspect the finish and polish of the RPD. A poorly finished prosthesis may unfavorably affect the patient's attitude toward the dentist &diminish patient-dentist rapport.

The polished surface contours should have a smooth, high-luster appearance without surface blemishes; that is a new appearance.

Store the RPD until the insertion appointment in a plastic bag partly filled with mouth wash &then heat sealed. This will keep the prosthesis moist to prevent dehydration &possible distortion of the acrylic resin base until the prosthesis is inserted.

Seating of the RPD framework

It is highly recommended to fit the cast metal framework intra-orally before the insertion appointment. Regardless, the completed RPD should be carefully inserted into position on the abutment teeth. If there is considerable resistance to seating, stop &check for the following problems:

1. Clasp or other components of the framework may have been bent or distorted.

2. A layer of acrylic resin flash may be covering part of the metal casting. Remove the acrylic resin before seating the RPD .A sharp dental explorer or dental floss can be used to check for the complete seating of the occlusal rests. There should be intimate fit between the teeth &retentive clasp assembly.

3. Acrylic resin may have been cured into undercuts adjacent to the abutment teeth, preventing the uniform seating of the prosthesis.

If the occlusal rests on the prosthesis do not seat completely in their respective rest seat preparations, a minor discrepancy in the cast metal framework can be identified &corrected.

4. Evaluation of the denture base adaptation. When the cast metal framework has been fully seated, fit the acrylic resin portions of the prosthesis. An accurately fitting acrylic resin denture base is a primary consideration in the comfort & acceptance of an RPD. Excessive pressure may lead to discomfort, pain, &soft tissue damage. A common contributor to excessive pressure is the dimensional changes that occur in the acrylic resin denture base during processing. Apply pressure indicating paste (PIP) evenly on the intagillo (tissue) surface of the prosthesis with a stiff, short, coarse-haired brush. A coarse brush will leave thin brush marks on the acrylic resin surface that displace under pressure. Apply an even, thin layer of PIP to register pressure areas. Then by acrylic bur we can remove the pressure areas, reapply PIP &reseat under finger pressure or the patient biting on cotton rolls. Adjustment are made until displacement of PIP appears only in the primary stress-bearing areas. There should be little or no paste distortion in areas that required relief or is not stress bearing (incisive papilla, tori, mylohyiod ridge, crest of the mandibular residual ridge, median raphe,..etc.)

5. Assessment of denture base peripheral extensions: the peripheral borders of the denture

base have a direct bearing on retention, stability, &patient comfort. Overextension of the

prosthesis denture borders may cause the followings:

1.The muscles &frena will tend to dislodge the RPD during function. The resultant

dislodging force may be transferred to the abutment teeth by the retentive clasp assemblies.

These forces may be especially destructive when the denture base borders of a bilateral

distal extension RPD are overextended. The longer the distal extension base, the longer the

lever arms, &the greater the potential for transmitting destructive forces to the supporting

structures of the abutment teeth.

2.Denture base overextension may cause ulceration, pain, &swelling of the vestibular

tissues. If this is not corrected, over an extended period of time, redundant tissue may form

in the vestibular as a response to chronic irritation.

3.Impingement on the muscles of mastication may interfere with muscle function during

mastication &speech.

4. Denture border extensions of modification spaces may interfere with the complete

seating of the RPD.

Under extension of the prosthesis denture borders may cause the followings:

1. Inadequate distribution of the masticatory force. The denture base should cover the

retromolar pads &buccal shelf area to the external oblique ridges to obtain maximal support

for the RPD.

2. Food may collect under tissue surface of an RPD &be an annoyance and/or an irritation.

3. The prosthesis may lack stability. Under-extended denture borders will not satisfactorily

resist lateral or horizontal stresses.

1. Observe intra-orally the denture borders of the RPD. Have the patient open the mouth

just wide enough to observe the denture borders. Overextension is usually easily detectable,

because the mucosal tissues will be displaced by the denture borders pressing into the soft

tissues. Under-extension can be observed by very lightly deflecting the border tissues with

the fingers &then letting the tissues return slowly to their relaxed position.

2. Use external palpation with the index finger. This is an especially effective method that

uses applied pressure on the outside of the face over the region of the external oblique

ridge. When the buccal flange of a mandibular RPD is over-extended in this area, the

dentist can feel that border extending out beyond the external oblique ridge.

3. Where it is difficult to observe border extensions, apply PIP or disclosing wax to the

RPD border. The prosthesis is then placed in the mouth, several drops of water are placed

on the patient's tongue, and the patient is asked to swallow. Any areas of over extension

will be visible where the wax or paste has been flattened or displaced by muscle action. The

use of disclosing wax or PIP is especially effective on the distobuccal border of a

mandibular RPD, which is controlled by the masseter muscle. The most common areas of

over-extension of a maxillary RPD are the tissue side of the distobuccal flange &continuing

through the pterygomaxillary notch area.

Common undercut areas are located inferior to the mylohyiod ridge, in the canine

&premolar fossae, &in the retromylohyiod space. Recent extraction of either maxillary or

mandibular anterior teeth will leave bony undercuts at the incisive &canine fossae. Relieve

denture bases to allow the prosthesis to be inserted & withdrawn over undercuts without

injury to underlying tissues. Adjustments can be done in two ways: the first is by

selective grinding of the tissue-fitting surface of the denture base over the undercut area; the

second is by compression of the mucoperiosteum &its subsequent relaxation when the RPD

is inserted. If either of these methods fails to allow the prosthesis to be inserted &withdrawn

in an a traumatic manner, vertical reduction of the denture flange may be indicated.

Evaluation of the denture base extension:

To properly contour a denture base in an anterior modification space, retract the lip &move

it to the left &right while observing the movement of the frenum into the acrylic resin

notch. The acrylic resin notch may need additional width and/or more commonly depth

modification to accommodate the labial frenum.

Denture teeth arrangement for the prosthesis should be accomplished to provide bilateral

simultaneous contact at the maximal intercuspal position(MIP). At the try-in visit, the

maxilla-mandibular relationships &the esthetic &phonetic, the arrangement of the denture

teeth are verified. Therefore, the occlusal adjustment of the RPD following processing

changes. Processing changes can be corrected with a laboratory remount of the prosthesis

before removal of the master cast. Minor interceptive occlusal contacts can be corrected by

selective grinding adjustments, which are made after the contacts are marked with

articulating paper. If gross premature occlusal contacts are noted, a new interocclusal record

should be made. Remount the RPD on a dental articulator &make method the necessary

occlusal corrections by selective grinding at an acceptable vertical dimension of occlusion.

This accomplished outside of the patient mouth &away from the patient. The same is used

for opposing prosthesis. The clinical remount is the most efficient method of adjusting

occlusion because it allows direct observation during adjustment.

The master cast is usually destroyed when the RPD is finished &polished. To obtain an

accurate remount cast to correct occlusal disharmonies, make an intra-oral irreversible

hydrocolloid (alginate) impression of the prosthesis correctly positioned on the supporting

tissues; that is , a pickup impression.

Occlusal adjustment:

A pickup impression in alginate impression may be used to fabricate a remount cast for

more extensive occlusal corrections.

Instructions to the patient:

1. The patient should advised that some discomfort that may be experienced initially.

2. The patient should advised of the possibility of soreness developing despite every attempt

on the part of the dentist to prevent its occurrences.

3. Discuss the problem of speech with the patient in regard to the new dentures.

4. The possibility of gagging or the tongue's reaction to a foreign object.

5. The mouth &the denture should be cleaned after eating &before retiring, by brushing by

small stiff-bristle brush.

6. The tissues should be allowed to rest by removing the denture at night.

7. The denture should be placed in a container &covered with water to prevent its

dehydration.