Adjustment of framework of clasp prosthesis

Adjustment of framework of clasp prosthesis.

Overlay of clasp prosthesis.

Removable Partial Denture Framework Fabrication

After fabrication of the master cast, the laboratory will perform the following steps in the fabrication of the removable partial denture framework:

1. Place wax blockout in undercuts on the master cast:

- below heights of contour

- minor connector & lingual plate embrasures

- soft tissue undercuts (if necessary)

2. Place relief on the master cast:

- under gridwork

- over free gingival margin

- under mandibular major connector

3. Duplicate master cast in refractory material, which will withstand casting temperatures

4. Wax-up framework according to design on secondary cast using prefabricated patterns

5. Invest refractory cast, solder wrought wire clasps

6. Burnout wax, cast in a chrome cobalt or other alloy

7. Finish & polish, return to dentist

Partial Denture Framework Adjustment

Even the best partial denture frameworks do not fit perfectly in the mouth. Stewart Rudd and Kuebker have stated that up to 75% of all frameworks may not fit the mouth on the day of insertion. Since clasp tips are designed to fit passively into a specified undercut, any discrepancy in seating of the partial denture framework will cause the direct retainers to become active, thereby causing orthodontic movement of the teeth. For this reason, frameworks must be adjusted intraorally. This is accomplished most easily when the denture base is not attached to the framework. Metal framework try-in should be accomplished as soon after the framework is

returned from the laboratory to minimize changes that occur due to tooth migration.

Pre-clinical Inspection and Adjustment

Ensure that the partial denture has been fabricated as designed. The dental laboratory should never change the framework design without consulting the dentist. Conversely, errors in framework design caused by inaccurate drawing on casts or omissions in laboratory prescriptions are the fault of the dentist. The framework should fit the master cast. If it does not, it will probably not fit intraorally. Replace the framework on master cast as little as possible to prevent abrasion (in case a remake is necessary). The framework should be assessed using the following

criteria:

1. Rest seats should be fully seated (adequate support)

2. Reciprocal arms and proximal plates should be contacting the cast

3. Linguoplates and maxillary palatal major connectors should be in intimate contact

with the cast (food impaction)

4. Major and minor connectors should be an adequate distance from abutment

teeth (hygiene). Adjust, if possible, or have lab adjust or remake framework

5. Major and minor connectors should be of proper proportions (rigidity, hygiene).

Note especially that cingulum rests should not be carried into embrasures and that

embrasure minor connectors for distal extensions should not be in contact with the

more anterior tooth (unless it has a rest seat preparation). Adjust, if possible, or

have lab adjust or remake framework.

6. Butt joints should be adequate for acrylic resin (slightly undercut). Adjust, if

possible, or have lab adjust or remake framework

7. Clasps should be of uniform taper

8. Proper gridwork should have adequate relief

9. Finish and polish of the framework should be adequate - no evidence of pits,

nodules and scratches in the metal. Eliminate sharp edges that might impinge on

the oral mucosa.

Check framework with an instructor prior to making adjustments. These adjustments should proceed the patient's clinical appointment for framework adjustment. Heatless stones, diamond burs, Brasseler E-Cutter burs, carborundum disks and coarse stones may be used to make adjustments to the major and minor connectors. Remove and replace the framework on the master casts as few times as possible. In this way, it will not be severely abraded should a remake of the framework be necessary.

Clinical Adjustment (Fit)

Binding against one or more of the abutment teeth can cause inadequate seating of a framework. The area(s) of binding cannot be located without the use of an indicating

medium. Several media can be used for this purpose:

1. Spray type Powders (Occlude): A small amount is sprayed in an even continuous layer over ALL tooth-contacting portions of the framework. The advantage of this medium is that it is thin and accurate and is not easily displaced from the framework. The material can get quite thick if over-sprayed. Teeth, tissues and the framework must be dry to prevent the pigment bleeding and making reading of the indicator difficult. A disadvantage of this technique is that it provides only two-dimensional assessment of fit.

2. Disclosing wax (Kerr): A small amount of wax is removed from the jar and placed on a mixing pad. A warmed instrument (#7 wax spatula, PKT waxing

instrument, etc.) is used to pick up and melt a portion of the wax. The melted wax is applied in an even coat over ALL tooth-contacting portions of the

framework. The wax is allowed to gel prior to placement in the mouth. The advantage of this medium is that it provides three-dimensional assessment of fit.

Areas of burn-through indicate possible areas of binding, and the thickness of the remaining wax indicates how far the rest of the framework is from contact with

the teeth. A disadvantage of wax is that it can stick to teeth or be wiped away easily if the framework is seated improperly.

3. Silicone impression materials or indicating medium:

These materials can also be used as three-dimensional indicators. A disadvantage of elastic materials is that they can tear or pull off the framework. In addition,

time is required for set of the materials. In this regard the silicone fit-checking media are more useful since they have shorter working times.

Use of Indicating Media

1. Attempt to place framework intraorally. If gross resistance to placement is felt, remove and coat with indicating medium. If the framework seats, ask the patient

if they feel the framework pulling on any teeth. The latter sensation will be caused by active engagement of abutment teeth. Inquire as to the overall comfort

of the framework.

2. Remove the framework and coat it with indicating medium. Align the framework over the abutment teeth and use finger pressure over rest seats along

the path of insertion. DO NOT PLACE PRESSURE OVER GRIDWORK OF DISTAL EXTENSIONS as this will fulcrum the framework. If gross resistance

to seating is encountered, remove and inspect for areas of burn-through. Have an instructor inspect the framework. Relieve areas of binding as indicated.

Repeat until seating is achieved. The master cast can be inspected for areas of abrasion that may indicate areas of gross binding as well.

3. Once the denture can be seated, coat with media and seat along the path of insertion again. Use firm even pressure over the rest seats and or indirect

retainers. A mirror handle can be used for seating purposes. Use care in removing the framework, as removal along the wrong path of insertion will

change the markings with displaceable media (wax & spray media).

4. Use caution in adjusting the framework. The clinician must differentiate between normal and abnormal contacts. Guiding planes normally will exhibit long

vertical areas of contact, but broad areas of complete burn-through may indicate a binding contact on the guiding plane. Similarly, the retentive tip of direct

retainers will normally exhibit burn-through, but active clasp retention must be eliminated after the framework is fully seated. Therefore, the first step in

adjustment is to ensure complete seating. The most common areas that interfere with seating are:

1. under rests

2. rigid portions of direct retainers (e.g. above the survey line)

3. interproximal portions of linguoplate major connectors

4. interproximal minor connectors

5. shoulder areas of embrasure clasps

Experience is required to differentiate between normal and excessive marking of the indicator medium. Therefore it is wise to consult with an instructor regarding

proposed changes prior to adjustment. Adjustments can be made with small round diamond burs, white stones or rubber abrasive points, depending on the

position and extent of binding. Do not use excessive force or the framework may be bent. Heat generation is one of the reasons major adjustments are made prior to acrylic placement (i.e. the heat would melt the acrylic).

5. Completely remove any media contaminated with metal grindings and place fresh media. Repeat this procedure until full seating is achieved. At this point a thin,

even film of media should be observed under rests and indirect retainers. The wax or silicon media will have a greyish hue from the underlying metal. The feel

of the denture upon seating will change from a grating or snapping sensation to one of a gliding sensation. Normal adjustment of a framework should take no

longer than 20 minutes.

6. Check for soft tissue impingements using pressure-indicating paste. Remove a small portion from the jar, and place it on a mixing pad. Use a stiff-bristled brush

to spread a thin layer over the tissue surfaces of the major connector, and infrabulge clasps. Leave streaks in the paste. Place intraorally with moderate

pressure and remove. Relieve any areas of marked burn-through. If streaks are left in the paste, this indicates no contact with the tissues. Adjust or leave accordingly. Maxillary palatal connectors should exhibit broad even contact with the palate.

7. If the framework cannot be adequately adjusted, it should be remade. In some cases this decision may be made at the pre-clinical inspection stage. Make this

determination early, so that time will allow for a new impression to be made. Determine if the casting fits similarly on the cast and in the mouth. If it does not, the final impression was most likely inaccurate and should be remade. If the casting does fit similarly, the discrepancy may be due to laboratory errors. In many cases abrasion of the master cast will require re-making of the final impression as well. If the pre-clinical inspection leads the dentist to believe a remake is a possibility, a new custom tray should be made prior to the patient appointment in anticipation of the need for a new impression.

Occlusal Adjustments to the Framework

Since most frameworks are be fabricated on unmounted casts there are usually occlusal interferences present on rests and indirect retainers. These should be adjusted at this time.

Vertical dimension should remain unchanged by a removable partial denture in almost all instances. The framework should not interfere with normal centric and eccentric contacts of the maxillary and mandibular teeth. Contacts should be identical with and without the framework in the mouth.

Mark occlusal contacts with thin articulating paper and remove the framework for

adjustment. The highly polished metal surfaces do not mark well with articulating paper so that the opposing occlusion should be checked for heavy contacts. Diamond burs, heatless stones, Shofu coral stones or cross cut Brasseler lab burs will most readily remove interferences. DO NOT FORGET TO LOCATE AND ADJUST EXCURSIVE INTERFERENCES.

When maxillary and mandibular frameworks are being adjusted, they should be adjusted individually, then placed in the mouth together to eliminate interferences between the frameworks. Occlusal rests or indirect retainers that have inadequate thickness (< 1.5 mm) after adjustment will be subject to fatigue and possible fracture. The latter situation may occur due to inadequate preparation (i.e. not considering opposing occlusion) or subsequent extrusion of teeth. If the teeth have extruded, the entire framework will most likely not fit. If occlusal interferences exist that will excessively thin the rests, the rest seat preparation may have to be deepened and a new impression taken, or an opposing cusp or framework element may have to be reduced. Reduction of opposing cusps should be performed as a last resort to save an otherwise acceptable framework.

Occlusal interferences should not normally occur on retentive clasp arms if proper

treatment planning has been followed. However, if the opposing occlusion is not

considered at the time of mouth preparations, it is possible that occlusal contact may occur on a retentive arm. If this contact is minor, the opposing cusp may be reduced. Again, reduction of opposing cusps should be performed as a last resort to save an otherwise acceptable framework. If the interference is gross, the tooth surface should be recontoured (i.e. lower height of contour) and a new impression taken. IN NO INSTANCE SHOULD A RETENTIVE ARM BE RELIEVED, since this will affect its flexibility and resistance to fracture.

Special Adjustments for Distal Extension Cases:

In most cases distal extension cases will be designed with relatively short occluso-gingival guiding planes to allow for release of the abutments during tissueward movement of the denture base. However, there are some cases where teeth are tipped and a long guiding plane is the only type of guiding plane that can be placed. In these instances, "physiologic relief" of the framework should be used to provide release. With this technique the distal guiding planes, minor connectors and linguoplates are coated with alcohol and rouge (not wax or silicone). The framework is placed intraorally and placed under hyperfunction by pressing over the distal extension gridwork. The framework is removed and the guideplanes and other rigid metal contacts, which could torque the tooth, are relieved in areas of burn-through. Relief should be provided so that marks remain in only the occlusal one third of the guiding planes.

Finishing and Polishing of Adjusted Surfaces

All adjusted surfaces should be smoothed and brought to a high polish. This is imperative, since even well finished frameworks have been shown to enhance intraoral plaque adhesion. Dedco green knife-edge wheels for chrome cobalt alloys will remove scratches and bring the adjusted surface to a high shine quickly. Additionally, Dedco blue clasp polishers or any other carborundum-impregnated points can be used to finish the chrome cobalt alloy. A final polish can be placed using a tripoli on a bristle brush and rouge on a small diameter cloth wheel. Use care not to snag the cloth wheel on sharp edges of the framework (to prevent injury to yourself). Remove traces of the polishing compounds with soap and water and a toothbrush.

Preclinical Inspectationof frmework

1. Check accuracy of the framework as designed

2. Framework should fit master cast If it does not, probably will not fit Intraorally

3. Rest seats should be fully seated

4. Contacting Cast:

a) Superior portion of lingual plates

b) All maxillary major connectors

c) Minor connectors

5.Adequate distance from abutments (hygiene)

6. Butt joint junction slightly undercut for acrylic resin (FINISH LINE)

7.Direct Retainers

1– Retentive arms • Clasps have uniform taper

2– Reciprocal arms,

3– Proximal plates

8.Finish and Polish

Highly polished

• No pits, nodules, scratches

• No sharp edges -injure mucosa

Solution:

Adjust or have lab adjust or remake framework

Clinical adjustment

No tissue contact

The metal framework tried in the mouth to verify the fit. Notice that the underside of the framework in the areas where teeth are to be placed is not in contact with the tissue.

1. Incomplete seating

Most common interferences:

– Under rests

– Rigid portions of direct retainers

– Interproximal portions of lingual plates

– Interproximal minor connectors

– Shoulder areas of embrasure clasps

Indicating Medium

Rouge & Alcohol

Aerosol • Sprays

 Disclosing Wax

Silicone

Rouge & Alcohol

Advantages

Thin & accurate

Disadvantages

– Not easily displaced

– Can dissolve in saliva

– Difficult to remove

– Can’t tell how far from seating

Disclosing Wax

Advantages

Sets immediately

Inexpensive

Shows how far from seating

Disadvantages

Can stick to teeth

Silicone

Advantages

Minimal distortion

Disadvantages

• More expensive

• Sets relatively slowly (2 min)

• Can tear or pull off the framework

Prior to imposing clasp dentures in the mouth it is necessary to look at it carefully, paying attention to the surface that is adjacent to the mucosa, which should be smooth and polished.

Often, denture on grafted is not imposed as plastic base is limited by defect of the dentition from aproximal side, at gum edge is wider and comes in the niche under the tooth equator. It can be explained by the following- the parallelity of aproximal sides is artificially created on the working models when casting frame. When the skeleton has been casted, it is set on a working model in occludars and have retention points on the teeth. Base plastic fills them when casting and prevents the imposition of denture on the jaw. These plots are removed with mill.

When the prosthesis has been applied to abutment teeth correlation of artificial teeth and antagonists is checked. If an increase of bite or second violation of articulation is observed, they are eliminated by general rules. Prosthesis mustn't cause pain, and if it does the prosthesis correction must be done..

Preferably,first day the patient removes the prosthesis only for oral cavity hygienic examination. This regime is possible only by industrious hygienic care of mouth and dentures. Not less than 2 times a year the patient should contact a doctor to check the status of the remaining teeth and mucosa. It is known that clasp dental prostheses, held on teeth, which are not covered by artificial crowns, require careful hygienic examination to prevent teeth from caries in areas of base attachment from the proximal side of the tooth. Because of this each day after meals they should be thoroughly cleaned with a toothbrush and toothpaste - teeth and clasp dental prosthesis.

Patients with periodontal disease and general organism disease with their manifestations in the mucous membrane of the mouth should not use the prosthesis every day, and must take them off at night to reduce the load on the supporting tissue. Often such patients' mucous membrane becomes inflamed, injured by prosthesis, often ulcers appear. In such cases, if the prosthesis usage regulation does not address complications it should be along with the general treatment to change the design of prosthesis.

Prosthesis in the mouth causes to a range of subjective sensations with the patient. As usual in its fixing day only gross defects in prosthesis design are eliminated - improving occlusion with occlusive pads or the other frame parts and artificial teeth. Only on the second day one may conduct more diligent preparation of clasp dental prosthesis. Often on the prosthesis fixing day the frame do not precisely embraces teeth,there is a gap between occlusive pads and clamps shoulders . After daily use such frame begins to be exactly adjacent to the prosthetic bed. It is explained by tooth physiological mobility.

The patient must know that in the early days clasp dental prostheses can lead to nausea, vomiting, enhanced salivation, speech impaired and disorder of taste sensations, polluted nibble and food chewing . All of this suggests that the prosthesis causes local and general tissue and nerve endings irritation.

Adaptation of the patient to clasp dental prosthesis occurs gradually. Note the three phases of adaptation to the denture. The first phase - irritation. It is observed on a fixing day of clasp dental prosthesis in the patient mouth. Phase II - partial inhibition: salivation comes to standards, the purity of the language is restored, the nausea disappears, increasing of chewing efficiency. The second period is short and takes 2-3 days. The third phase -full braking phase, it comes from the time when the patient ceases to feel the prosthesis as foreign body. Chewing efficiency is at maximum. This period, depending on the type of nervous activity continues 1-2 weeks.

For faster patients adaptation to clasp dental prostheses is advised not to take off them at night for 3-4 days, limiting only to hygienic care.

Adaptation period when using the clasp dental prostheses twenty-four-hour is shorter. Good adaptation promotes rapid restoration of masticatory efficiency.

Looking After your Dentures

You need to care for complete and partial dentures as carefully as you would look after natural teeth.

Clean them every day. Plaque and tartar can build up on false teeth, just like they do on natural teeth.

Take them out every night. Brush your teeth and gums carefully, using a soft toothbrush. Be sure to clean and massage your gums. If your toothbrush hurts you, run it under warm water to make it softer OR try using a finger wrapped in a clean, damp cloth.

Soak them overnight. They can be soaked in a special cleaner for false teeth (denture cleanser), in warm water or in a mix of warm water and vinegar (half and half). If your denture has metal clasps, use warm water only for soaking. Soaking will loosen plaque and tartar. They will then come off more easily when you brush.

Fitting the clasp dental prosthesis

Prior to imposing clasp dentures in the mouth it is necessary to look at it carefully, paying attention to the surface that is adjacent to the mucosa, which should be smooth and polished.

For faster patients adaptation to clasp dental prostheses is advised not to take off them at night for 3-4 days, limiting only to hygienic care.

Adaptation period when using the clasp dental prostheses twenty-four-hour is shorter. Good adaptation promotes rapid restoration of masticatory efficiency.

Common Metal Framework Problems

The following are common metal framework problems and possible solutions:

• Frame fits cast but not the oral cavity

- Distorted master impression. Remake case.

- Abutment teeth have drifted. Place self-cure resin blocks into the mesh area for temporary occlusion and have the patient wear the frame for several days. Hope

for orthodontic-like positional movement.

• Frame pops up before a complete insertion is accomplished

- Too much retention. Reduce height of contour on teeth.

- Inflexible retentive clasps. Thin and taper the clasp toward the tip.

- Rigid parts of the framework, i.e., major connector, bracing clasp, or guide plate are in harsh premature contact with teeth. Reduce frame thickness and/or height

of contour of teeth. Also, check the cast for signs of abrasion and adjust the framework accordingly. • Teeter-totter of framework

- Locate the fulcrum point with rouge-chloroform and reduce frame and/or tooth.

- Distal extensions only. Expect a slight posterior downward rock on a distal extension frame. Essentially, you are usually observing mucosal compression

under the small tissue stop. If your impression was accurate, the resin saddle will not allow this rocking after processing. If the posterior downward rock persists at

delivery, then consider a reline. If the downward rock at framework try-in is gross, make an altered cast impression.

• Bent major connector

- Section the major connector (usually a lingual bar) at the bend. Replace each part into the oral cavity properly and make a full arch over impression. Pour a stone

cast and send to the laboratory for a weld repair.

- Distorted master impression. Remake case.

• Broken cast-type clasp

- Place clasp part and framework correctly in the mouth. Dura-lay the parts together. Take a full arch impression pulling the framework with it. Pour cast

and send it to the laboratory for weld.

- Consider the above except have the laboratory place a retentive wrought clasp into the adjacent resin base or weld the wrought clasp to the framework.

- Remake the case if the above fail.

Adhesion is the use of two identical surfaces when there is a thin sublayer of fluid between them.

The adhesion fixation force is 100g/cm², the denture of the upper jaw with an area of 20 cm² is fixed with force of 2 kg. During the masticatory function the denture withstands pressure of 15-20 kg in force. Therefore, adhesion for fixation of the partial plate denture is insufficient.

Anatomical retention points

The so-called clasp-free dentures are fixed with the aid of the anatomical retention points. This kind of dentures is satisfactory as to the cosmetic appearance. Although denture fixation becomes weaker in some period of time as the base loosens the abutment teeth. Clasp-free dentures are justifiable in using elastic plastic.

Plastic dentoalveolar clasps by Kemeni.

The Hungarian dentist I.Kemeni proposed to use dentoalveolar clasps made of plastic for fixation of the partial plate dentures. These dentures are called retention ones. The dentoalveolar clasps may be constructed in case when the vestibular surface of the alveolar process has a straight or sloping structure and the teeth are positioned in conformity with the alveolar crest. When the vestibular surface of the alveolar process is thread-like or the teeth are inclined vestibularly, retention dentures cannot be constructed.

Fixation of the removable plate dentures with the help of telescopic crowns

This kind of dentures is widely applied in the Western countries. The singly standing or separate groups of the teeth are constructed metal crowns-caps that are fixed on the teeth by phosphate cement. Other crowns are constructed to be placed on these crowns that are, in their turn, fixed in the denture. While placing the denture the external crowns are applied on the internal ones, thus achieving satisfactory fixation of the dentures. But the masticatory load falling on the whole denture is transferred to a small number of the teeth resulting in overload of the parodont of these teeth with different consequences.

Fixation of the dentures by Rumpel

The singly standing teeth or separate groups of the teeth are covered with crowns with soldered metal bar that passes in the middle of the alveolar process. A long slot is made in the denture base where the bar fit. The masticatory load is transferred on the bar via the denture, and in this way on the abutment teeth resulting in the fast loosening due to overload.

Fixation of the partial plate dentures with the help of vestibularly-directed clasps

To strengthen the single teeth or separate groups of the teeth and to fix plate dentures V.I.Kulazhenko proposed a construction of the continuous vestibular clasp in 1962. The vestibular clasp is a metal bar that connects natural teeth from the vestibular side at the neck. Such construction of dentures contributes to strengthening of the loosen teeth and provides good fixation of the plate dentures.

Clasp fixation

A clasp is a hook that fixes the denture. Natural teeth where the clasps are placed are called the abutment teeth.

To obtain the best fixation of the denture the following should be taken into consideration: mobility of the abutment teeth, their number, choice and solution of the problem of the kind of the clasp strengthening.

There are three kinds of clasp fixation:

- Point fixation – only one tooth is used for abutment. In such fixation the abutment tooth becomes loosen rapidly because of lever-like force of the clasp and denture base on the abutment tooth.

- Linear fixation – two teeth are used for abutment. The clasp line may be sagittal, diagonal and transversal. When there is a free choice, it is better to construct a diagonal one on the upper jaw and transversal clasp fixation – on the lower jaw. The sagittal fixation is the least fitting for both jaws.

- Plane strengthening is the most rational strengthening as 3-4 teeth are used as abutment teeth.

Clasps are divided into:

1. By the method of making – wire (labile) and cast (stable).

2. By the shape: circular, semicircular and strip.

3. By the degree of coverage – one-chain, multichain and continuous

4. By the number of arms – one-arm and two- arm.

5. By the fixation – retaining, tooth-supported, molar clasper

The retainer is composed of the arm, body and process (anchor part). The arm covers the abutment tooth from the vestibular side between the equator and the tooth neck. The body is located on the equator with approximal surface of the tooth; and the process connects the clasp with the denture base.

Even the clasp of the most rational construction is not safe for the abutment teeth. The more flexible the clasp, the less it loosens the abutment teeth. Clasp flexibility depends on the method of its making and the arm of length. Cast clasps do not have flexibility, which is characteristic of the flexible ones.

Indications and constructive features of crown construction for clasps of the plate dentures

As it was said, the crown construction in prosthesis with partial denture is not obligatory.

The crowns are indicated 1) in defects of the hard tissues of the tooth; 2) in devitalization of the teeth; 3) for strengthening of the loosen teeth by soldering several crowns; 4) for leveling of the occlusion plane.

The abutment teeth, on which the crowns are constructed, are prepared in such a way that their sides are equilateral. In restoration of the anatomical shape of the prepared teeth on the model, the equator is formed only on the vestibular side that has an adjacent tooth. The lateral sides are modeled as equilateral ones.

How do you wear a removable partial denture

Removable partial dentures usually consist of replacement teeth attached to pink or gum-colored plastic bases, which are connected by metal framework. Removable partial dentures attach to your natural teeth with metal clasps or devices called precision attachments. Precision attachments are generally more esthetic than metal clasps and they are nearly invisible. Crowns on your natural teeth may improve the fit of a removable partial denture and they are usually required with attachments. Dentures with precision attachments generally cost more than those with metal clasps. Consult with your dentist to find out which type is right for you.

How long will it take to get used to wearing a partial denture

For the first few weeks, your new partial denture may feel awkward or bulky. However, your mouth will eventually become accustomed to wearing it. Inserting and removing the denture will require some practice. Never force the partial denture into position by biting down. This could bend or break the clasps.

How long should I wear the partial denture

You may be asked to wear your partial denture all the time. Although this may be temporarily uncomfortable, it is the quickest way to identify those denture parts that may need adjustment. If the denture puts too much pressure on a particular area, that spot will become sore. Your dentist will adjust the denture to fit more comfortably. After making adjustments, the dentist will probably recommend that you take the denture out of your mouth before going to bed and replace it in the morning.

Will it be difficult to eat with a partial denture

Having a partial denture should make eating a more pleasant experience. Start out by eating soft foods that are cut into small pieces. Chew on both sides of the mouth to keep even pressure on the denture. Avoid foods that are extremely sticky or hard. When having partial dentures you may want to avoid chewing gum while you adjust to the denture.

Will the partial denture change how I speak

It can be difficult to speak clearly when you are missing teeth but wearing a partial denture may help. With time, you will become accustomed to speaking properly with your denture.

How do I take care of my partial denture

Handling a partial denture requires care. It's a good idea to stand over a folded towel or a sink of water just in case you accidentally drop the denture. Brush the denture each day to remove food deposits and plaque. Brushing your denture helps prevent the appliance from becoming permanently stained. It's best to use a brush that is designed for cleaning dentures. A denture brush has bristles that are arranged to fit the shape of the denture. A regular, soft-bristled toothbrush is also ok to use. Avoid using a brush with hard bristles, which can damage the denture.
We recommend any denture cleaner with the American Dental Association (ADA) Seal of Acceptance.
Some people use hand soap or mild dishwashing liquid to clean their dentures, which are both acceptable. Other types of household cleaners and many toothpastes are too abrasive and should not be used for cleaning dentures.
Clean your dentures by thoroughly rinsing off loose food particles. Moisten the brush and apply the denture cleaner. Brush all denture surfaces gently to avoid damaging the plastic or bending the attachments.
A denture could lose its shape if it is not kept moist. At night, the denture should be placed in soaking solution or water. However, if the appliance has metal attachments, they could be tarnished if placed in soaking solution. The dentist will recommend the proper method for keeping your dentures in good shape.
Brushing twice a day and cleaning between your teeth daily help prevent tooth decay and gum disease that can lead to tooth loss. Pay special attention to cleaning teeth that fit under the denture's metal clasps. Plaque that becomes trapped under the clasps will increase the risk of tooth decay.

Will my partial denture need adjusting

Over time, adjusting the partial denture may be necessary. As you age, your mouth naturally changes, which can affect the fit of the denture. Your bone and gum ridges can recede or shrink, resulting in a loose-fitting denture. Partial Dentures that do not fit properly should be adjusted by the dentist. Loose partial dentures can cause various problems, including sores or infections. Contact the dentist if your denture becomes loose.

Can I make minor adjustments or repairs to my partial denture

You can do serious harm to your partial denture and to your health by trying to adjust or repair your denture. We recommend that you do not try to attempt to fix dentures yourself and instead go see you dentist.

Removable partial or full dentures require proper denture care to keep them clean, free from stains and looking their best. For good denture care:

What's the best way to care for removable dentures

Remove and rinse dentures after eating. Run water over your dentures to remove food debris and other loose particles. You may want to place a towel on the counter or in the sink so that the dentures won't break if you drop them.
Clean your mouth after removing your dentures. Use a soft-bristled toothbrush on natural teeth and gauze or a soft toothbrush to clean your tongue and palate.
Scrub your dentures at least daily. Gently scrub your dentures using a denture cleaner, mild soap or dishwashing liquid and a denture brush or soft toothbrush to remove food, plaque and other deposits. Avoid stiff-bristled brushes, strong cleansers and harsh toothpaste, as these are too abrasive and can damage your dentures. Toothpastes advertised as whitening pastes are especially abrasive and should be avoided with removable dentures.
Handle your dentures carefully. Be sure you don't bend or damage the plastic or the clasps when cleaning.
Soak dentures overnight. Most types of dentures need to remain moist to keep their shape. Place the dentures in water or a mild denture-soaking solution overnight. Don't soak dentures with metal attachments in solutions that contain chlorine because it can tarnish the metal. Check with your dentist about properly storing your dentures overnight.
Rinse dentures before putting them back in your mouth, especially if using a denture-soaking solution. These solutions can contain harmful chemicals that cause vomiting, pain or burns if swallowed.
Schedule regular dental checkups. Your dentist will advise you about how often to visit to have your dentures examined and professionally cleaned. Your dentist can help ensure a proper fit to prevent slippage and discomfort. See your dentist promptly if your dentures become loose. Loose dentures can cause irritation, sores and infection.

Denture Insertion

· Examine the dentures and check there are no sharp edges or acrylic 'pearls' on the fitting surface of the saddle areas.

· Insert denture into the mouth. Occasionally the denture cannot be seated because acrylic has been processed into an undercut area on the cast; this is due to inadequate blocking out of the undercuts. If the area of acrylic to be removed is not immediately apparent, use pressure relief cream. Always remove the acrylic by approaching with the bur from the fitting surface. The seal between denture and tooth in the non-undercut

area should never be touched.
· In the mouth, check:-
i. Adaptation of components
ii. Retention and stability
iii. Occlusion

· Occlusal contact is checked by asking for the patient's comments, by visual inspection, and by the use of articulating paper. Articulating paper should be inserted bilaterally and not unilaterally. In the latter instance, the patient may tend to deviate the mandible to the side on which the paper is placed.

Occlusal adjustment should be continued until both the patient's comments and visual inspection confirm that even contact has been achieved in the chosen jaw position.

Attention should be given to occlusal contacts in lateral and protrusive positions. In many cases the dentures will be adjusted so that they conform to the occlusal guidance provided by the remaining natural teeth.

Advice to the Patient

· Insertion and removal of denture. The patient must be taught the correct way to handle the denture. Vulnerable components must be pointed out.

· A printed sheet of instructions is provided for the patient. This will mention in particular aspects such as cleaning/eating/wearing at night/pain/need for regular recall - including recall with the hygienist.

· It is important to discuss these points verbally with the patient first of all. The purpose of the sheet is simply to act as an aide-memoir.

· Finally you should ensure that the patient knows who to contact (i.e. you) in the event of problems arising with the denture. You are responsible for the prosthetic care of the patient which does not end with the insertion of a denture. Where problems arise, an appointment MUST be made to see the patient at your next available opportunity.

REVIEW APPOINTMENT

The patient should be asked for comments on the first week or fortnight of wearing the dentures.

A history must be taken of any complaint. Subsequent examination must be directed to diagnosing the cause of the complaint before making any adjustments. Whether or not there are any problems reported by the patient, the denture-bearing tissues must be examined and the occlusion must be checked. At times a patient may claim to be perfectly comfortable even though extensive ulceration is present.

Any inflammation of the denture-bearing tissues, which is not related to the peripheral area, is most likely due to occlusal causes. Therefore a careful inspection must be made of occlusal contact in tooth position and excursive movements, and the necessary adjustments made. The impression surface of the denture must not be 'eased' empirically. Should attention of the impression surface be required, a disclosing material such as pressure indicator paste should be used.

A check must be made on the patient's oral and denture hygiene with the use of disclosing solution. Steps to reinforce plaque control must be taken if appropriate.

Sore Areas With Partial Dentures

An appointment will be made for you 24 to 48 hours after insertion of your new partial dentures. Sore areas may develop within this time period and it is important to find and adjust the cause of the sores. Your new partial is made of two parts. The first is the framework made of cobalt-chromium. The teeth and gums are made of an acrylic material.

Do not attempt to adjust the partial dentures yourself because they can very easily be made worthless by a do-ityourself adjustment. As patients use the partials, they will settle on the soft tissues and remaining teeth. This will necessitate additional adjustment appointments, as the occurrence of new sores is certainly possible. If you find it necessary to remove your partial because of excessive soreness, reinsert it 24 hours preceding your appointment for the adjustment. This will make it possible to see the pressure areas on the tissue and pinpoint accurately where to adjust the partial.

Speaking With Partials

Learning to talk with your partial in place requires practice and perseverance. Reading aloud is a very helpful method of learning to pronounce words distinctly. Practice those words or sounds that seen to give you the most difficulty. It

takes time for the tongue to learn the different positions necessary to make good speech sounds with new dentures.

Chewing With Partials

Learning to chew with partials will probably take six to eight weeks. Patience is required to learn to eat with your dentures. At first, limit your diet to soft foods that are easy to chew. Gradually learn to eat foods that are more difficult.

Cut food into small pieces. Take small bites and chew slowly, trying to overcome the difficulties as they appear. If possible, learn to chew on both sides of your partial. Since the muscles of the cheeks, lips, and tongue will tend to

displace your dentures, do not develop the habit of displacing them with these muscles. Rather, train these muscles to assist in keeping your partial dentures in place.

Increased Saliva With Partials

Do not be alarmed at the greater amounts of saliva in your mouth during the first few weeks of wearing your partial.

This condition will correct itself, as you become accustomed to wearing them.

Oral Hygiene With Partials

Your partial should be left out of your mouth at least eight of every twenty-four hours to allow the tissues to rest from the pressures placed on them by the partial. Failure to allow the tissues to rest can result in chronic irritation to the

tissues, the development of certain fungal infections and more rapid loss of bone. (Remember that this bone is desperately needed to provide support for the dentures in future years so it must be conserved.)

It is important to clean your partial and rinse your mouth after every meal. The tissues of the mouth and tongue should be brushed daily with a soft bristle toothbrush. This provides stimulation for increased circulation and removes debris

that could cause irritation and offensive odors.

Good oral hygiene is a must to save the remaining teeth and prevent further bone loss. Brush twice daily and floss at least once a day.

Longevity of Partials

The assumption that partials will last a lifetime is incorrect. Take into consideration that both the partial and tissues will change over a period of time. It is suggested that your mouth is examined and the fit of your partial be evaluated by a dentist on a yearly basis.

Shrinkage or resorption of your ridges is a normal occurrence. This results in a loosening of your dentures and perhaps a change in facial expression due to a settling of the partial on the ridges. Sometimes you will notice these changes within a few weeks. In some people it may not occur for many months or even years. Never try to repair, reline, or adjust the partial yourself. This could be destructive to the tissue and underlying bone on which the partial rests.

Limitation of Partials

Do not expect your partial to function as your natural teeth once did. Learn to know the limitations of your partials and adjust your living habits accordingly.

How To Care For Your Partials

It is important that your partials be kept clean. Accumulation of food debris around the teeth and under the partial can result in irritation to the tissue and unpleasant odors.

Insert and remove the partial as instructed. Do not bend the clasps. Even though the metal is strong, it is still brittle.

Grabbing hold of the metal wires while trying to remove the partial may cause a stress fracture of the framework.

Partials should be cleaned after every meal by rinsing them thoroughly under running water and rinsing your mouth.

Different commercial denture cleansers are available for cleaning your partial dentures. It’s preferable to use a nonabrasive cleanser, as you do not want to alter the surface of the dentures. Never use bleach or any products containing

corrosive material which could ruin the surface of the metal framework. If you choose to use a commercial cleanser it is important to closely follow the instructions given with the product. These cleansers are not designed for use in the

mouth. Typically, the denture should be soaked in the rinse for a maximum of 15 minutes and rinsed thoroughly before placing the denture back in the mouth. Dentures should only be soaked overnight in clean water.

Post-Op Period

Any follow-up appointments or adjustments to your new partial will be done at no charge to you for three months from the date of delivery. After this period, office visits will incur an additional charge.

How to Care for Your Denture or Partial

1. Rinse the denture/partial and brush away plaque and food debris regularly (once to twice a day). Place denture/partial into container of cleaning solution to continue the cleansing and disinfection process. Denture tablets for soaking are available at many stores and any brand will work, does not have to be expensive. (follow directions on container)
2. While denture is soaking, use a dampened washcloth or very soft toothbrush, dampened with warm water (or salt water solution) to wipe the inside of the mouth. Making sure to wipe the ridges (where dentures sit), tongue, lips, cheeks and roof of the mouth. If you wear a partial, use a soft toothbrush and make sure to clean all the teeth and tissues in your mouth thoroughly. This should be done at least once or twice each day.
3. After denture/partial soaking, remove from solution. Using a moistened denture brush or regular soft bristled toothbrush with toothpaste, gently clean inside of denture, outside of denture and teeth. Use a mouthwash to give fresh taste and clean feeling.
4. Next, thoroughly rinse the denture/partial with water and re-insert into the mouth.
5. At night, we recommend that you remove the denture/partial. This allows the tissue to breathe and heal by removing the pressure that is placed on the gums and tissues. Dentures/partials should be kept in water or mouthwash when out of the mouth to prevent drying out of the materials, which can cause distortion. We understand that some are uncomfortable leaving them out at night. In those instances, making sure to keep the mouth and denture/partial extremely clean is very important to maintain healthy tissue.
Remember that the gum tissue is in constant state of change, but the dentures are not. Over time your dentures may loosen and need to be professionally adjusted or relined. We recommend that you have a dentist check your dentures annually, as well as having an oral cancer screening examination.

FITTING AND ADJUSTING THE RPD TO THE MOUTH

Error: Failing to evaluate the denture border when first evaluating the completed RPD intraorally.

Problem: An undercut in the soft tissue denture base area can be very difficult to locate and judge for adjustment.

If the RPD is seated too rapidly or firmly, the patient may experience pain.

Solution: The plastic part of the denture base is the only concern at this time. The framework should have already been evaluated and fitted to the patient’s mouth. Flow a bead of white disclosing wax around the resin borders of the RPD. Carefully seat the RPD in the mouth until the patient can feel pressure caused by the borders, and then remove the RPD and look at the areas where pink plastic shows through the white wax. These areas of the border should be trimmed.

Error: Excessively trimming the denture base where pink resin shows through the disclosing wax.

Problem: Grinding more or less of the denture base than necessary will not give the desired results. Failing to identify the correct areas will prolong the fitting

process. Removing too much resin will leave spaces under the denture base or shorten the borders, thus reducing tissue support and contributing to food

collection under the denture base.

Solution: Remove only the denture base border that shows through the wax. The denture base will show through the white wax only where the base is binding

on the ridge. It is very specific. Add more disclosing wax to the area and continue the procedure until the RPD can be seated without wiping off the wax or hurting the patient. Several repetitions of the procedure usually are needed to seat the base properly. The inside (sharp) edge must be rounded slightly before each application of wax to prevent injury to the patient.

Error: Failing to determine that the denture borders are overextended.

Problem: An overextended RPD border may not make the patient’s mouth sore, but it may place constant pressure on the teeth in contact with the RPD.

Just as with an orthodontic appliance, light steady pressure can move these teeth.

Solution: Flow a bead of disclosing wax around the borders of the RPD base, and hold the base in place intraorally while manually muscle trimming the borders by pulling on the cheeks. On the lingual aspect of the mandibular RPD, have the patient protrude the tongue and extend it into each cheek. All movements should be made to the maximum extent. Trim the borders until the plastic denture base does not show

through the disclosing wax.

Error: Not polishing areas that have been adjusted.

Problem: If the borders are not polished, they may abrade and injure the soft tissue.

Solution: Take time to smooth and highly polish the edges of the denture base.

Error: Failing to adjust the occlusion intraorally.

Problem: Even if the RPD was remounted after processing and the occlusion was adjusted to remove processing errors, the occlusion must be adjusted intraorally. Mounting inaccuracies or flaws in the casts may cause errors in the final occlusion.

If the occlusion is left high on an RPD, the patient will keep biting the RPD until it seats, thereby damaging the teeth and supporting tissues.

Solution: Adjust the occlusion first in the centric relation position, then in protrusive, right lateral, and left lateral excursions. Use 0.0005-in. thick shim stock to finalize the occlusal contacts.

Error: Failing to show the patient how to seat and remove the RPD.

Problem: If the patient does not seat the RPD correctly, he/she may warp the RPD or be injured by it.

Solution: Demonstrate how to place the RPD in the patient’s mouth so that it is centered on top of the teeth and how to push the RPD into place with the fingers. Warn the patient about the destruction that may result if he/she bites on the RPD to seat it.

Error: Failing to tell the patient how to care for the RPD.

Problem: Studies have shown that more clasps are bent and RPDs distorted from being dropped in an unprotected washbasin than from any other cause. The second most common reason for loss of RPD use is accidental disposal of the RPD.

Solution: Instruct the patient to partially fill his/her sink basin with water when cleaning the RPD; if the RPD slips out of his/her grasp, the water will break its

fall. Also instruct the patient to place the RPD, when it is out of the mouth, in a special and easily recognizable container filled with an appropriate cleansing

solution. A drinking glass is not recommended because someone may discard the contents of the glass without realizing that it is being used for RPD storage.

Error: Failing to make a follow-up appointment for the patient.

Problem: If the patient is allowed to decide when afollow-up appointment is needed, he/she may postpone it for as long as possible. Patients often wait until something really hurts before coming in for a followup appointment. By this point, irreversible damage may have occurred.

Solution: Schedule the first follow-up appointment for the day after the patient receives the RPD. When the patient returns for that visit, thoroughly examine

the entire mouth, both with the RPD in place and with it out of the mouth. Look for red spots or cuts in the soft tissues. Move each tooth contacted by the RPD to determine whether any teeth are sore. Use white disclosing wax inside the clasps and on the intaglio of the denture base to find areas of the denture that require correction. Most potential problems can be eliminated before the patient is aware that a problem exists.

PROCESSING AND FINISHING DENTURES

DEFINITION:

A process that substitutes acrylic resin for the baseplate material and wax that makes up the denture base. The contours of the basal seat and the external surface will be accurately reproduced and the denture teeth will be retained in their correct position.

PURPOSE:

To produce an acrylic resin denture base containing teeth.

INSTRUMENTS AND SUPPLIES:

1. Upper and lower investing and processing flasks

2. Plaster bowl and spatula

3. Waxed denture on master casts.

4. Glass jar and metal spatula

5. Vaseline and applicator brush

6. Dental Plaster

7. Dental Stone

8. Water

9. Acrylic resin - monomer and polymer

10. Measuring vials

11. Tin foil substitutes

12. Brush

13. Flask press

14. Plaster saw

15. Buffalo knife

16. Acrylic trimmers - burs and stones

17. Rag wheel

18. Felt wheel

19. Felt cone

20. Pumice

21. Kreshine

PROCEDURE:

Suggested Quality Procedures

1. Make sure the laboratory prescription is easy to read, easy to understand, and completely filled out before sending it to the lab.

2. Make sure the denture wax-up accurately represents the proper gingival and arch form, following guidelines for accepted oral anatomy. Wax the denture to the full contour and properly seal it to the master model.

3. If mechanical retention is desired to secure teeth, prepare the teeth after removing wax and cleaning the denture mould. Use minimal drilling and grinding to minimize weakening of teeth. A chemical bonding agent may be used on plastic teeth if desired.

4. When packing, prepare and process the acrylic resin exactly to the manufacturer's directions for use. Thorough cleanliness is essential during the mixing and packing of the acrylic resin.

Quality Standards

1. Processed denture base is free of porosity and contaminants such as investment debris.

2. Processed dentures do not have excessive increase in vertical dimension as confirmed when remounted on the articulator.

3. Processed dentures are free of visible flaws or defects.

Quality Failures

1. Processed denture has internal porosity and/or large voids.

2. Processed denture has excessive increase in vertical dimension (more than1.5-mm).

3. Tooth movement causes improper articulation.

4. Excess melting of wax during boil-out penetrates investment making devesting difficult or discoloring acrylic.

5. Note: There are no ways to check for ‘disasters’ during pack, pour, or injection procedures. Following the directions for use is the best way to avoid remakes.

1. Investing:

The investing procedure is the placing of the waxed denture bases and teeth in suitable investing media in preparation for wax elimination and packing of acrylic resin in its place. Plaster and stone, contained within a split metal flask, are the investing materials because of their hardness and ability to reproduce surface detail.

Place the upper and lower sections of the flask together and ensure that they fit flush (so that there is no gap between the two sections that would allow the stone to leak out). Place the casts in their respective flasks (the lower part of the maxillary flask's rim will be parallel with its base and the mandibular flask's rim will be inclined from back to front). Note that most processing flasks contain a lid, an upper and lower component (divided according to whether it is used for an upper or lower denture) and a bottom knock out disc. According to the Boucher textbook, the cast with the completed denture wax-up should not be closer than 3 mm (1/8 inch) from the top of the assembled flask. I believe a minimum of one half-inch clearance from the top of the flask to the teeth is essential. If it is closer than this it could cause the teeth to shift during the packing process. The base of the cast must be reduced if it is too thick. This destroys the mounting index, thus preventing a laboratory remount to correct for processing error.

Lubricate the casts properly with petrolatum or separating agent to assist in cleaner, easier devestment and less finishing labor. (At this stage the wax form should be sealed to the stone base around the entire periphery.) A piece of tinfoil can be adapted to the base to provide easy separation when deflasking the processed denture. Prepare the appropriate flask by lubricating all internal surfaces with Vaseline. This will also facilitate the deflasking process.

Each denture is first invested in the lower half of the respective flask. Make a mix of plaster and place it into the flask. Position the cast into the plaster allowing the excess plaster to squeeze upward around the periphery. Trim off excess plaster so that it is flush with the land area of the casts and clear of the flask lip. The depth to which the cast is placed into the plaster is determined by the height of the teeth in relation to the top of the flask. Therefore it is advisable to place the upper half on the flask, without the lid, to make this determination. No difficulty will be experienced if the cast thickness is correct as described in the procedure for pouring and trimming the master cast. The cast may be further pressed into the plaster until the correct height is achieved. This must be accomplished while the plaster is still soft and all excess should be removed after each manipulation. Allow plaster to set a minimum of 20 minutes. Trim and smooth all plaster surfaces. Remove excess plaster edges so that the halves of the flask can be placed in opposition without leaving a gap between the two sections.

Apply tin foil substitute to the exposed plaster and stone surfaces. The separator is painted on with a brush until a shiny surface is attained. Avoid pooling of the separator but make sure all the exposed plaster and stone surfaces are covered. Allow the separator to dry. Place the upper half of the flask in place without the lid. Vacuum mix investment stone for best results. Make a 1:1 mix of stone/plaster and vibrate it into the flask up to just over the occlusal surfaces of the teeth. The amount of investment needed depends upon the size of the denture. In most cases the amount normally used for 2 models is sufficient. Pour investment properly to minimize bubbles by filling the flask from one side to the other allowing air to escape. This is the same technique as pouring an impression.

Smooth the investment back down to the occlusal surfaces of the teeth with a wet finger. Allow the mix to dry until it is hard to the touch, then paint it with Vaseline or tin foil substitute. Allow the tinfoil substitute to dry if it is used.

Clean off the edge of the flask so that the cap will fit flush with this surface. Vacuum mix enough stone to fill the remaining portion of the flask (enough for 1 model) and carefully apply it to the occlusal portions of the teeth. Vibrate additional stone into the flask to slightly overfill it. Place the lid on and press completely to place, allowing excess stone to squeeze out of the lid holes. Clear excess stone and place the flask in a press under light pressure. Artificial stone is used over the teeth because its greater strength will better resist pressures against the teeth during packing. Allow the stone to set for 45 minutes.

2. Wax Elimination:

Thoroughly boil-out and flush wax residue from invested case with clean boiling water. This prevents contamination of the processed denture base resin. Immerse the flask in boiling water for 5 minutes to soften the wax. Remove from water and carefully pry open the flask halves. Peel away the baseplate and unmelted portions of wax. Note that if Triad was used as a baseplate it will not soften under heat and will need to be carefully lifted off the cast to avoid marring the cast's surface. Also note that the teeth are retained in the upper half of the flask. Clear all traces of wax from all surfaces and teeth by flushing repeatedly with clean boiling water.

3. Packing:

Allow the flasks to cool to room temperature and paint all surfaces. EXCEPT THE TEETH, with tin foil substitute until shiny.

Prepare a mix of acrylic resin sufficient for a denture (30 gr. polymer to 30 cc monomer is enough for the average case). Follow manufacturers' directions for proper mixing and packing consistency. See dental materials section at the end for characteristics of polymerization.

There are 2 methods of packing: trial pack closure and single pack closure.

For trial pack closure, acrylic is placed into each half of the flask in slight excess and two sheets of plastic are placed between the halves before closure. The flask is slowly compressed in a (pneumatic) press allowing excess acrylic to slowly squeeze out between flask halves. More acrylic can be added if necessary and the process repeated until the flash is seen expressed around the entire border of the flask. The flash is carefully removed and the process is repeated with one layer of plastic until no flash is seen. When the acrylic is sufficiently dense and feels rubbery to the touch, all flash is removed and complete closure is made. The final closure will not contain a plastic sheet. When applying the acrylic to the molds, care should be exercised so that the teeth are not lifted or moved. The packing pressure should be moderate and applied gradually as the excess acrylic escapes. Great pressure can be directed at the teeth during closure and this can displace or intrude them into the investing material.

4. Curing:

The flasks should remain under pressure for at least 15 minutes. This is known as bench curing and lets the acrylic equalize its flow before curing. If 2 dentures are to be cured, they may be transferred to a double processing press.

The manufacturer's directions should be followed for curing. Most acrylic resins are cured in water at 160 F for 1 hour, followed by another hour at boiling. An alternative method is 160 F for 10 hours. The flasks are removed and allowed to bench cool. Bench cooling is very important as separating the denture while is too hot may cause fracture and/or distortion.

5. Recovery (Deflasking):

Remove the flask lid by wedging an instrument (Buffalo knife) in the notch that is provided on the flat end of the flask. Use a mallet to tap the insert disc at the bottom of the flask until the investment is dislodged from the flask. Use plaster shears or nippers, chip the plaster from around the periphery of the stone cast until the base is exposed. Using plaster saw and shears remove all plaster until the denture is exposed. The plaster should be removed in small increments so that none of the acrylic, the cast or the teeth is fractured. You should recover a processed denture base containing teeth attached to a stone master cast.

6. Occlusal Correction (a.k.a., Laboratory Remount):

The recovered dentures are luted to their original mountings with sticky wax or compound and then replaced on the articulator. It is important to note that if the flasking and packing method is used to process dentures there can be no decrease in pin height. For this reason it is imperative that the pin be set at the zero-mark when the casts are mounted and maintained at this point throughout the remount process. The lab remount procedure will be outlined in detail in a following section.

7. Finish:

After equilibration is completed, the denture is removed from the stone casts using a plaster saw and shears. Acrylic may crack or fracture if excess pressure or wedging force is exerted. Do not use a hammer to break out the stone! Remember that parts of the ridge configuration may contain undercuts that will hold the denture fast. These areas must be chipped away carefully.

1. Use care when removing investment from the restoration, especially when using power devices. Remove investment starting at the posterior section and moving toward the anterior section. Avoid using force.

2. If available, use walnut shell abrasive to remove gross investment. If not, use ultrasonic stone and plaster remover in an ultrasonic unit for thirty (30) minutes. Do not use a sand blaster!

Trim all gross excess acrylic down to the original waxed denture form, being careful not to remove the following:

- Buccal, facial and lingual fold contour (remember you should have established these areas by border-molding and muscle-trimming!)

- Post-dam area

- Gingival festooning around the teeth

- Surface contour and root eminences

Minor alteration of these areas may be made with acrylic burs, small burs and stones.

- Inspect the tissue side of the dentures for small blebs due to voids in the casts. Remove these with burs and/or a denture scraper. A piece of 2x2 gauze rubbed lightly over the tissue surface will pull a string if there are any small blebs.

- Check for flash on the teeth. Remove these carefully with a discoid or other small instrument and a mounted rubber point but do not over-polish acrylic denture teeth.

- Finish the external surface and peripheral fold with rubber wheels to remove gross defects and to impart final contour. Use light pressure on the restoration when using a lathe or handpiece.

- Use wet rag wheels and wet felt cones mounted on a lathe to polish the external surfaces up to the peripheral fold. Use coarse abrasives and burs first, if needed for gross reduction. Use finer abrasives to finish. Start with medium pumice followed by fine flour of pumice until all scratches are removed. It is advisable to use the low speed on the lathe and copious amounts of pumice in order to better control the amount of polish. Maneuver the denture so that the depressed or concave areas are polished. Maintain the surface contour during this procedure. Finally, impart a high shine on the same areas using a felt wheel and Kreshine. Note that the basal seat surfaces are not altered or shined.

Quality Standards

ACRYLIC APPEARANCE

1. Denture base is clean without traces of investment or polishing media present on denture base surface.

2. Contours mimic nature and follow the desired criteria of the restoring clinical professional and patient.

3. All edges are rounded and smooth, but not over-polished.

4. Stippling and festooning, if desired, is subtle and follows accepted criteria for appearance and contour.

5. Tissue bearing surface of denture base must be free of sharp edges and positive or negative defects (bubbles and voids).

OCCLUSION / TEETH

1. There should be minimal pin opening on the articulator when the restorations are remounted.

2. The appliance should have even contact on all occlusal surfaces.

3. Premature tooth contacts are removed carefully with selected grinding procedures; care must be taken to maintain an aesthetic appearance of the teeth.

4. Labial, buccal and lingual surfaces of denture teeth should not require polishing.

Quality Failures

1. Denture breaks when investment is removed.

2. An over-polished tooth surface shows loss of labial, buccal and lingual anatomy.

3. Tissue surface of denture base inadvertently polished, creating loss of retention and fit.

4. The denture base is burned or discolored from heavy pressure or extended polishing with a lathe and/or handpiece.

5. Sharp denture borders or sharp areas on the tissue surface remain.

6. Teeth broken during cast retrieval or polishing.

7. Notches for frenuli are over-relieved.

The dentist's role does not end with the delivery of a meticulously planned and fabricated removable partial denture. Occasional breakage is inevitable due to various mishaps that may befall the prosthesis, thereby causing loss of retention, instability and discomfort to the patient.

Maintenance of the partial denture is therefore required and involves repair, replacement or modification of the components of the framework.

Among the common types of metal framework repairs associated with cast partial dentures is the repair of clasp components. Though repair procedures can be time consuming and expensive, these are sometimes the most feasible solution to a broken prosthesis. The fit, function and esthetics of the partial denture should be sufficient to warrant a restoration of the clasp assembly rather than fabricating a new prosthesis.¹

The cause of breakage of a clasp has to be evaluated prior to commencing the repair procedure. If the reason is poor design or construction and inadequate mouth preparation, appropriate corrections have to be made to prevent repeated fracture. If the thickness of metal at the fracture site is less than 1.2 mm, mouth preparation should be accomplished; either by modifying tooth contours or by reducing severe undercuts by accurate survey of the cast.²

Repairs of a broken clasp can be grouped as:

§ Repair with wrought wire clasp

§ Replacement with cast clasp

§ Repair with a cast clasp while patient retains the denture

§ Repair of broken occlusal rest (which is a part of the clasp assembly)

§ Laser welding.

REPAIR WITH WROUGHT WIRE CLASP

This method is commonly used for broken retentive arms of circumferential type of clasps. It is quick and relatively simple but may not yield the best result.

Procedure

A prerequisite for repair is an accurate impression of the prosthesis in its proper position in the mouth, without altering the relationship of the framework to the abutment tooth.

A soft impression material, such as alginate can be used for a pick-up impression after maintaining the partial denture in its ideal relation to the supporting structures. U-shaped paper clips can be attached to the denture base with sticky wax to help lock the denture in the impression.A complete-arch cast is poured with dental stone following the block out of soft tissue undercuts in the denture base with modeling clay and application of a thin coat of petroleum jelly to the exposed metallic portions.A cast of the opposing arch may be required to evaluate occlusal contact during the repair. The cast and the denture are carefully separated and the repair area is evaluated. The contours of the stone abutment tooth are surveyed and a pencil line is used to indicate the exact position of the clasp to ensure correct contour and retention.

A groove is made in the rest-minor connector area adjacent to the repair area.³ The groove may originate at the remnant of the broken clasp on the buccal aspect of the minor connector (if not contraindicated by occlusal interference) and should pass under the mesioproximal edge of the replacement tooth nearest to the abutment. The remaining broken wire may be removed with a carborundum disk.

Repair of Extracoronal Direct Retainers

Groove cut in the rest-minor connector area

Millersuggests making of an opening in the resin of the lingual flange which passes through the base just below the occlusal surface of the denture tooth immediately adjacent to the minor connector. Wrought wire (18 gauge) is contoured and adapted to the precise line of clasp contact. In case an opening is made to house the wire as mentioned previously, the wire is contoured to enter the opening on the lingual side of the denture and emerge on the buccal aspect.

The wire is secured to the denture base by either of the two methods:

§ Using autopolymerizing acrylic resin

§ Electric soldering.

A box-like preparation can be made in the resin of the lingual flange to house an anchorage for the new clasp arm and the wire can then be anchored within the resin. The wire can be held in place with sticky wax while the resin is applied.Curing of the resin should take place in a heated pressure pot or in a closed container for best results.

The new clasp arm can also be secured to the denture by soldering it to the junction of the rest and minor connector. If the clasp is to be soldered to the frame, a precious metal high fusing wire (about 18 gauge) should be used. The clasp is extended 3 to 4 mm lingual to the minor connector. Soldering should be done electrically to prevent overheating of the wire. A low fusing triple thick gold solder should be used.The soldering tip should remain in position for 1 to 2 seconds. The soldered joint should then be finished and polished.

Repair of Extracoronal Direct Retainers

Opening made in the resin of the lingual flange which passes through the base just below the occlusal surface of the denture tooth immediately adjacent to the minor connector

Repair of Extracoronal Direct Retainers

Box-like preparation made in the resin of the lingual flange to anchor the clasp with autopolymerizing resin

Infrabulge clasps can also be repaired using wrought wire and are always retained in resin. A trough can be cut in the buccolabial flange to accept the base of the wire. To provide retention against rotation within the resin, a bend can be incorporated at the distal end.

REPAIR WITH CAST CLASP

In this technique, a pattern for the replacement clasp is fabricated either in wax or autopolymerizing acrylic resin directly on the stone cast and then reproduced either in chrome-cobalt alloy. It is a more definitive method of repairing broken clasps and is useful in cases where rigidity is needed due to fracture of an occlusal rest or other type of supporting area. Embrasure clasps and clasps associated with single tooth replacements can be replaced more conveniently in this manner than by forming them in wrought wire.

Brudvik recommends replacing a broken circumferential clasp with an infrabulge clasp since the replacement clasp will be contained entirely in the resin of the denture base and not involve occlusal surfaces. If the adjacent acrylic flange is not of suitable proportion to allow I-bar placement, the repair requires a circumferential clasp. Reciprocal clasp arms, if broken, require refabrication of the entire clasp.

Procedure

The partial denture is positioned so that the exact frame-totooth relationship is reproduced on the repair cast. A pickup impression is made with irreversible hydrocolloid. Undercuts in the denture base are blocked out with modeling clay and exposed metallic portions are lubricated with petroleum jelly. A complete-arch cast is poured to allow reseating of the denture and survey of the cast for modifications. A cast of the opposing arch is helpful for evaluation of occlusion. The partial denture and cast are separated and the clasp design is determined. The denture is reseated on the repair cast and evaluated.

A lingual keyway is cut in the major connector where the clasp is fractured. Millersuggests the use of a buccal matrix made on the denture base area on the side to be repaired to aid in repositioning of the teeth after

Repair of Extracoronal Direct Retainers

Replacement of a broken circumferential clasp with I-bar. Trough is created in the buccolabial flange for the base of the wire

Repair of Extracoronal Direct Retainers

Keyway cut in the major connector lingually

casting of the clasp and soldering in case the teeth and base need to be removed prior to the repair. Clasp addition can be waxed and sprued on the repair cast in certain situations. A small amount of investment suitable for the alloy to be used is painted on the wax to strengthen the repair segment before removing it from the cast.The repair cast could otherwise be duplicated to form a refractory cast on which the wax repair components are added. The completed wax-up can be sprued in a nonfunctioning area and added to a routine framework casting as a 'rider'.

Smith has suggested a technique using cold cure resin to form a clasp pattern. Here, a tin foil substitute is applied on the cast surface. Using the brush technique, the desired clasp pattern is painted on with cold curing acrylic resin. When the resin has hardened, the acrylic clasp is removed and refined. The fit is verified by replacing on the cast. The pattern is then removed from the cast, sprued and cast with an appropriate metal alloy. The cast clasp is then returned to position and attached to the major connector with an electric soldering apparatus and polished. The solder joint between the clasp and framework must be placed such that the joint is not involved in clasp flexure.

Livaditis has also reported an etched metal to etched metal connection with composite resin. Adhesive resins like 4-META have been described for use in metal-metal connections. This technique requires a broader interface between components and is more technique sensitive.

Repair of Extracoronal Direct Retainers

Acrylic clasp pattern painted on the cast using brush technique. Undercuts blocked out with wax (denoted in red)

Repair of Extracoronal Direct Retainers

Cast clasp fits in the keyway

Repair of Extracoronal Direct Retainers

Buccal view of the casting positioned on the cast

REPAIR WITH SURVEYED CAST CLASP WHILE PATIENT RETAINS DENTURE

Another approach for repair of a gingivally approaching clasp with broken adjacent denture flange described by Livaditis¹ is to cut a groove into the denture base 2 to 3 mm deep, 4 to 5 mm wide and 10 to 15 mm in length below the necks of the denture teeth on the buccal surface. At least 2 raised resin index islands are maintained for retention and precise transfer from the working cast to the prosthesis and abutment. After taking an impression, the grooved area is filled with wax and returned to the patient. The cast is poured; undercuts are blocked out and replicated in refractory investment material. The clasp assembly is then waxed and cast. The framework is refined and relieved from the walls of the groove but contact is maintained with the raised resin index areas. Temporary stabilizing arms are incorporated on to the clasp. An acrylic resin finish line is given onto the casting where the clasp emerges from the denture base to facilitate finishing of the repair resin. The clasp is polished, its position is verified intraorally and it is attached with autopolymerizing resin.

In order to simplify this sophisticated procedure described by Livaditis,¹ Sato et al¹⁰ described a simple, quick and accurate method to replace a broken bar type cast clasp with a new cast clasp of the same design using a close fitting resin matrix which enables accurate positioning of the new clasp arm and eliminates the need for stabilizing arms recommended by Livaditis. The initial steps of making a groove in the denture, fabrication of the working cast and casting of the clasp are the same. The denture is returned to the patient after filling the groove in the denture with tissue conditioner. The new cast clasp is fixed in position on the working cast with sticky wax. A resin separating medium is applied on the cast, undercuts are blocked out with utility wax and a matrix is made out of autopolymerizing acrylic resin. The matrix covers the abutment, anterior part of the I-bar clasp arm and adjacent anterior teeth. The incisal surfaces of the stone teeth and the occlusal surfaces of the denture teeth are not covered to prevent interference in intercuspation. The set matrix is then removed from the working cast with the clasp arm connected to the matrix. The removable partial denture is seated in the mouth and the resin matrix with the new clasp arm is positioned in place. The space between the retentive segment of the new clasp arm and the resin in the groove of the denture is examined and additional space is created if required. The new clasp arm is then attached to the denture base with autopolymerizing acrylic resin and the matrix is removed once the resin sets.

REPAIR OF A FRACTURED OCCLUSAL REST

A fractured occlusal rest is a result of thin metal over the marginal ridge of the abutment tooth due to inadequate tooth preparation. Therefore, the first step in repair is to provide the required space for the rest by reducing the marginal ridge. The lingual minor connector is then sectioned a few millimeters below the occlusal surface before making the pick-up impression so that the weld is not placed in an area of occlusal load. The replacement rest is waxed on the lubricated repair cast and is sprued with a small round wax sprue lead. To prevent distortion, a small amount of refractory material is painted around the wax-up and when it is set, the entire segment is freed from the repair cast. The repair is joined by the sprue lead to a sprue base of a complete removable partial denture wax-up as a 'rider' and cast in a normal fashion. The recovered repair segment is evaluated for fit on the repair cast and soldered.

LASER WELDING

Laser welding is an attractive alternative method to join dental casting alloys and is proving to be superior to soldering due to various advantages offered. Pulsed lasers (commonly Nd:YAG dental lasers) are often used for metal repairs and can be set for variable parameters like pulse power, pulse duration, pulse energy and spot diameter.Advantages of this technique include:

§ High reproducible strength for all metals, consistent with that of the substrate alloy.

§ Localized heat production.

§ Accurate fit of the framework (since all the inaccuracies in the assembly caused by transfers from the master cast along with investment and heat distortions are reduced).

§ Possibility of welding in close proximity to acrylic resin or ceramic with little damage (cracking or color damage) due to pin point heat produced.

§ Reduced working time, ease of operation and no need for investment and soldering alloy.

§ Potentially all metals can be joined, particularly titanium, which is difficult to solder due to its high melting point and high reactivity. It helps to overcome the disadvantages of highly reactive titanium by providing a shielding gas (argon) during the welding process. A high rate of laser beam absorption and low thermal conductivity makes it easier to weld broken titanium clasps.Air particle abrasion with alumina particles (50 µ) prior

to the procedure increases the absorption coefficient of laser energy. Welding is carried out under an argon shielding atmosphere to decrease oxidation contamination.Laser welding requires a contact overlap the components. The standard procedures consist of tack welding in four widely separated places followed by continued welding all around the circumference using an overlap of approximately 70%.The parent metal is placed at an angle of 45° and the laser beam is positioned such that one-third of it is directed at the parent metal and two-thirds is directed at the work piece to be welded. When small gaps exist between overlapped components, filler materials must be inserted into the joint space to achieve contact of the components (e.g. Co-Cr wire). The resulting welds are not as strong or as dependable as those with component contact. After definitive welding; the clasp is finished and polished conventionally.

Disadvantages of laser welding include technique sensitivity and increased equipment cost.Success of the welding procedure depends on operator's dexterity and choice of welding parameters.