Substituting for the partial defects of dental rows by RPDs. Constructing of RPDs
Reliminary impressions of a patient’s mouth are obtained in stock, ‘off-the-peg’, impression trays. The resulting study casts are needed for planning treatment, including the
designing of RPDs, and for the construction of individual trays which will be used to obtain the more accurate working impressions required for the construction of the RPDs.
Stock trays are available in a variety of sizes and shapes. They may be perforated or imperforated, metal or plastic, of simple box design or shaped to fit bilateral distal extension saddles.
A size of tray is selected so that the teeth sit centrally within the trough of the tray. If possible there should be a space of about 4mm between the flange of the tray and the buccal and labial surfaces of the teeth.A clinical guide to removable partial dentures
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Because the range of stock trays is limited it will commonly be found that an ideal size and shape of stock tray is not available. In this example, the maxillary stock tray does not cover the labial surfaces of the teeth sufficiently, neither does it include the most posterior teeth.
There may also be regions where the tray is poorly adapted to the underlying structures such as the palate or a saddle area.
In each case the dead space should be filled by placing a high-viscosity material, such as impression compound, in the appropriate area. Silicone putty is a suitable alternative material for this tray correction (Figure 8.16). The material is then moulded in the mouth.
Preliminary impressions
Lingual border moulding of the compound is achieved by the patient first pushing the tongue to contact the upper lip — and then thrusting the tongue into each corner of the mouth in turn.
Any areas of the impression compound which are over-extended should be corrected by trimming away the excess material, resoftening in a flame and tempering in warm water before repeating the border moulding.
Compound that has contacted the teeth should be cut away as it may prevent accurate re-insertion of the impression tray and will eliminate space around the teeth necessary for a sufficient thickness of the alginate used to complete the preliminary impression.
Under-extension in the labial region can be corrected by the addition of impression compound to the deficient areas of the tray to form a slightly over-extended flange. A clinical guide to removable partial dentures
The tray is then seated in the mouth while the compound is still soft and border moulding is carried out. Buccal and labial moulding of both maxillary and mandibular impressions is achieved by supporting the tray with one hand while manipulating the cheeks and lips with the other.
When a water bath is not available for softening the impression compound, alternative materials, such as silicone putty or pink modelling wax, may be used to modify the tray.
Once modification of the stock tray has been completed any additions of compound or wax are thoroughly chilled and the tray is dried. A thin layer of adhesive is applied and allowed to dry before the tray is loaded with alginate. The tray is then seated in the mouth and the impression material border-moulded.
The completed impression is assessed by considering three aspects.
1 Those sulcus areas which will be related to the denture borders.
2 The edentulous areas.
3 The teeth.
The impression on the left is satisfactory, the one on the right shows a number of faults: the tray has been positioned too far to the patient’s right; the borders of the alginate are unsupported; the impression is under- extended in the post-dam region. If on inspection the impression is found to be satisfactory, it fected. The impression should be shaken to remove any excess is rinsed thoroughly to remove all traces of saliva and is disin- moisture. Preliminary impressions
An indelible pencil line may be drawn on the impression to indicate to the dental technician the required extension of the individual tray.
The completed impression must be prevented from drying out by covering it with a damp napkin and placing it in a plastic bag.
While the impression is waiting to be cast the tray should be supported so that its own weight is not applied to the borders of the impression. If this is not done, permanent deformation of the impression will occur.
The impression must be cast as soon as possible to avoid inaccuracies developing as a result of the dimensional instability of alginate.
Instructions to the laboratory
In order to obtain the best results from RPD treatment, it is essential that the dentist and the dental technician work efficiently together as a team. Each should understand the role and requirements of the other so that they can collaborate effectively. An essential part of this process is efficient communication. There must be an exchange of accurate and comprehensive information.
When sending work to the dental technician, the dentist must produce a written, detailed work authorisation supplemented, where necessary, by verbal communication. The contents of this authorisation will vary to a certain extent according to the clinical stage and local requirements.
The authorisation sent with the preliminary impressions should include the following.
1. Details of the patient and the dental practice.
2. Confirmation that the clinical items have been disinfected.
3. Date of the next appointment.
4. A request for the study casts to be surveyed if required.
5. A request for wax occlusal rims where necessary, if mounting of the study casts on an articulator is required to assist in the RPD design stage.
6. Specification of the material and design of the individual impression trays.
7. Size and location of any stops to be preformed in the tray.
Recording the jaw relationship
he objective of this stage of clinical treatment is to record a specific jaw relationship, such as the intercuspal position or the retruded position, so that the casts can be mounted on an articulator. This will permit correct positioning of the artificial teeth.
The casts must be mounted on the articulator in exactly the same occluding relationship as occurs in the patient. The complexity of the task is related to the number and occlusal relationship of the remaining teeth and may be categorised as follows.
Sufficient teeth may be present to enable the casts to be placed together accurately in a stable intercuspal position at the desired vertical and horizontal jaw relationship. Thus no additional visit by the patient is required to record the jaw relationship. The use of any interocclusal record, such as a wax wafer, in this situation increases the chance of introducing inaccuracies.
Often the desired jaw relationship cannot be so easily reproduced outside the mouth even in the presence of an occlusal stop, because there may be insufficient occluding teeth to produce a stable position of the casts.
Alternatively, the occlusal stop may produce an intercuspal position at an unacceptable horizontal and vertical jaw relationship. Tilting or drifting of teeth, or loss of tooth substance by abrasion, attrition or erosion, may be contributory factors resulting in mandibular deviation or reduced occlusal vertical dimension.
On occasion the remaining teeth may be so placed in the jaws that they do not provide an occlusal stop, let alone a stable cast relationship.
For these last three situations, occlusal rims are adjusted in the mouth to record the desired jaw relationship so that it can be transferred to the casts.
The wax occlusal rims may be placed on temporary bases of shellac or acrylic resin, or on the definitive cast metal frameworks. These must be tried in the mouth and their stability checked. If the stability is poor, yet the baseplate fits the cast accurately, consideration must
If an anterior saddle replaces only one or two teeth, there will be sufficient guidance from the remaining teeth to determine the position of the artificial replacements.
be given to the possibility that the problem is due to an inaccurate impression. If this is confirmed the working impression must be retaken. The retention of the occlusal rim must be sufficient to maintain the rim in position during subsequent recording procedures.
The anterior inferior border of the rim should be adjusted to indicate the desired incisal level. This is decided by reference to any adjacent teeth and to the resting level of the upper lip. A line may also be scribed on the labial face of the rim to indicate the projected midline of the incisors.
Where many anterior teeth are missing the rim should be carved until its incisal level is parallel to the imaginary horizontal line joining the pupils of the eyes (interpupillary line).
Adjustment of the rims
When maxillary anterior teeth are present, the mid-incisal point will generally be located about
Adjustment of the rims
The anterior inferior border of the rim should be adjusted to indicate the desired incisal level. This is decided by reference to any adjacent teeth and to the resting level of the upper lip. A line may also be scribed on the labial face of the rim to indicate the projected midline of the incisors.
Adjustment of the rims
Wheatural mandibular anterior teeth oppose an edentulous area in the anterior maxillary region, the maxillary rim may need to be thinned from the palatal aspect to accommodate these teeth in order to achieve the correct jaw relationship. The inferior border and labial face of the maxillary anterior wax rim should be preserved to indicate the desired position of the artificial teeth.
The maxillary wax rims in any posterior edentulous areas are trimmed until they indicate the desired position of the occlusal plane.
Adjustment of the rims
Sufficient posterior teeth may be present to indicate the approximate level of the occlusal plane.
Adjustment of the rims
Where opposing natural teeth are present these will normally be the determining factor in finalising the position of the occlusal surface of the rim. Here the rim has been modified to accommodate a mandibular tooth that has erupted beyond the projected occlusal plane.
If many posterior teeth are missing, the maxillary rim should be carved until it is parallel to the line joining the inferior border of the ala of the nose to the midpoint of the tragus of the ear with the aid, if desired, of an occlusal plane guide.
Adjustment of the rims
The wax occlusal rims may be placed on temporary bases of shellac or acrylic resin, or on the definitive cast metal frameworks. These must be tried in the mouth and their stability checked. If the stability is poor, yet the baseplate fits the cast accurately
Adjustment of the rims
The width of the rim should also be adjusted until it indicates the desired bucco-lingual positioning of the teeth. The rim (1) is too bulky, whilst rim (2) has been corrected.
In the absence of a posterior abutment tooth to act as a guide, the buccal side of the maxillary rim should just contact the cheek mucosa when the mouth is half open.
Adjustment of the rims
The mandibular occlusal rim is inserted and adjusted until it meets the maxillary rim or teeth evenly under minimal pressure in the desired jaw relationship. The rim should not then tilt away from the denture-bearing mucosa (1) or compress the mucosa or the wax of the rim (2). Tilting or compression will result in the casts not being articulated in the same relationship as the patient’s jaws.
Where opposing natural teeth are present these will normally be the determining factor in finalising the position of the occlusal surface of the rim. Here the rim has been modified to accommodate a mandibular tooth that has erupted beyond the projected occlusal plane.
If many posterior teeth are missing, the maxillary rim should be carved until it is parallel to the line joining the inferior border of the ala of the nose to the midpoint of the tragus of the ear with the aid, if desired, of an occlusal plane guide.
Adjustment of the rims
The mandibular rim is also adjusted until it indicates the position of the teeth in the neutral zone. This rim is encroaching on the tongue space and needs to be reduced on its lingual aspect.
The jaw relationship may be indicated by intercuspation of some of the remaining teeth. Where the existing jaw relationship is not acceptable or there is no positive occlusal stop, the resting vertical dimension (1) should be assessed. The occlusal vertical dimension of the rims (2) must then be adjusted so that an adequate freeway space (3) is provided.
When guidance from posterior teeth has been lost, the jaw relationship in the horizontal plane should be recorded with the mandible in the retruded position as this is reproducible and close to an acceptable intercuspal position.
Finalising the registration with an acceptable occlusal stop
Finalising the registration with an acceptable occlusal stop
The mandibular rim is also adjusted until it indicates the position of the teeth in the neutral zone. This rim is encroaching on the tongue space and needs to be reduced on its lingual aspect.
The jaw relationship may be indicated by intercuspation of some of the remaining teeth. Where the existing jaw relationship is not acceptable or there is no positive occlusal stop, the resting vertical dimension (1) should be assessed. The occlusal vertical dimension of the rims (2) must then be adjusted so that an adequate freeway space (3) is provided.
When guidance from posterior teeth has been lost, the jaw relationship in the horizontal plane should be recorded with the mandible in the retruded position as this is reproducible and close to an acceptable intercuspal position.
Finalising the registration with an acceptable occlusal stop
The jaw relationship may be indicated by intercuspation of some of the remaining teeth. Where the existing jaw relationship is not acceptable or there is no positive occlusal stop, the resting vertical dimension (1) should be assessed. The occlusal vertical dimension of the rims (2) must then be adjusted so that an adequate freeway space (3) is provided.
Finalising the registration with an acceptable occlusal stop
A further millimetre of wax is removed from the occlusal surface of the rims to provide a slight gap between opposing rims or teeth, thus avoiding the possibility of occlusal pressure distorting either wax or mucosa. To permit subsequent separation of the occlusal rims, one of the rims (usually the maxillary) and its associated teeth are lightly coated with petroleum jelly.
Finalising the registration
The space between the rims is then taken up by a recording medium that should be of uniformly low initial viscosity to avoid compression of the wax or mucosa, and that sets rigidly to provide a positive and reliable registration. Impression plaster or a modified zinc oxide/eugenol paste fulfils these conditions; softened wax does not.
Finalising the registration without an acceptable occlusal stop
Once the correct occlusal vertical dimension has been achieved, no more wax is removed from the rims. If this were done the occlusal vertical dimension would be decreased; otherwise the registration procedure is as above.
The patient must close into the retruded jaw relationship and maintain that position while the recording medium sets under minimal pressure.Checking the registration
Any recording medium that has flowed beyond the tips of the opposing cusps or edge of the opposing rims is carefully trimmed so that only shallow indentations remain. This aids direct visual assessment of the accuracy of the record in the mouth.
The casts are now placed in occlusion using the occlusal rims. Trimming of the casts may be necessary to permit their accurate location in the registration. The heels of the casts may touch each other, as shown here, or portions of the opposing rim or baseplate and thus prevent the casts from seating fully in the occlusal record.
It is important to remember that it is the clinician’s responsibility to ensure that the desired jaw relationship has been transferred accurately from the mouth to the casts. The relationship of the natural teeth to each other must thus be inspected; if they are further apart on the casts (a) than they are in the mouth (b), compression of the wax or mucosa must be suspected.
The mandibular rim is also adjusted until it indicates the position of the teeth in the neutral zone. This rim is encroaching on the tongue space and needs to be reduced on its lingual aspect.
The jaw relationship may be indicated by intercuspation of some of the remaining teeth. Where the existing jaw relationship is not acceptable or there is no positive occlusal stop, the resting vertical dimension (1) should be assessed. The occlusal vertical dimension of the rims (2) must then be adjusted so that an adequate freeway space (3) is provided.
When guidance from posterior teeth has been lost, the jaw relationship in the horizontal plane should be recorded with the mandible in the retruded position as this is reproducible and close to an acceptable intercuspal position.
Finalising the registration with an acceptable occlusal stop
The jaw relationship may be indicated by intercuspation of some of the remaining teeth. Where the existing jaw relationship is not acceptable or there is no positive occlusal stop, the resting vertical dimension (1) should be assessed. The occlusal vertical dimension of the rims (2) must then be adjusted so that an adequate freeway space (3) is provided.
Checking the registration
It is important to remember that it is the clinician’s responsibility to ensure that the desired jaw relationship has been transferred accurately from the mouth to the casts. The relationship of the natural teeth to each other must thus be inspected; if they are further apart on the casts (a) than they are in the mouth (b), compression of the wax or mucosa must be suspected.
Metal backings
Metal backings are likely to be required for artificial maxillary anterior teeth when opposing natural teeth are virtually contacting the mucosa of the edentulous area.
If this is the case the dentist should ask the laboratory to produce a wax trial insertion of the teeth on a shellac or acrylic resin baseplate so that the appearance of the denture can be assessed. It is essential for the patient and dentist to agree on the definitive position of the artificial teeth before the metal framework is cast. As only limited modification of the position of the anterior teeth is possible once the framework with backings has been produced, a new framework would be required if subsequent significant alteration of the teeth proved to be necessary. Instructions to the laboratory
Care must be taken when sending the completed jaw registration to the laboratory as wax readily distorts if it becomes warm or is placed under pressure.
Beside general information about the patient, dental practice, date of next appointment and confirmation that the clinical items have been disinfected, the following requests and information should be included on the laboratory prescription sheet.
4 The unwanted undercuts that need to be blocked out on the cast. These undercuts will have beeoted when the denture was designed on an articulated surveyed study cast.
5 The definitive design for any metal framework in the form of an annotated diagram, supplemented wherever possible by an outline drawn on the study cast.
6 If the altered cast technique (chapter 19) is to be employed at the next appointment, the work authorisation should request the addition of acrylic resin tray material to the framework to cover the distal extension edentulous areas.
7 The inclusion of palatal relief when indicated.
If artificial teeth are to be set up for trial insertion at the next
appointment, the following additional information is required.
8 The shade, mould and material to be used for the artificial teeth.
9 The desired arrangement (rotation, inclination, spacing, etc.) of any anterior teeth. An impression of the existing RPD may be indicated to give accurate information on this aspect if the patient is happy with the appearance.
10 The material to be used for the base to hold the artificial teeth. If the base is not to be the metal framework it must be shellac or acrylic resin. Wax bases distort readily at mouth temperature.
11 The type of articulator to be used. When a semi-adjustable articulator is required, the laboratory should be supplied with the necessary facebow and occlusal records (chapter 9).
If the type of articulator needs to be changed at any subsequent stage appropriate instructions will need to be given at that time.
Trial insertion of the metal framework
Іt is recommended that the trial insertion of the metal framework should initially be undertaken without the addition of any wax rims or artificial teeth. If the casting does not fit into place at once, the presence of wax hinders the search for interferences and additionally, if the casting needs adjustment with stones, the heat generated may melt the wax.
If desired, the framework in a distal extension edentulous area may have a close-fitting temporary acrylic resin base attached to it to permit the recording of an altered cast impression.
Trial insertion of the metal framework
The framework is first examined on the cast to ensure that the prescribed design has been followed. Any wrought clasps should have been included and attached to the cast-metal framework by solder or cold-curing acrylic resin. All components should be checked to ensure that the fit is accurate, that they are of adequate dimensions and are correctly positioned.
Trial insertion of the metal framework
These components are not correctly positioned, being too close to the gingival margins or failing to cross the margins at an angle of at least 90°.This component is not correctly positioned, being too close to the gingival margins.
Trial insertion of the metal framework
The stability of the casting should be checked under finger pressure. Kennedy Class I and II frameworks (A Clinical Guide To Removable Partial Denture Design chapter 2 ) with a spaced mesh will rock if pressure is applied to the saddle area unless a stop or foot (arrowed) is provided to support the mesh. Fully tooth-supported frameworks should not rock.
Trial insertion of the metal framework
These components are correctly positioned.
The fitting surface of major connectors covering the gingival margin should be inspected. Any sharp metal entering the gingival crevice should be removed. This must be done with care however, as excessive stoning will create a space beneath the connector into which the gingivae will proliferate.
The framework is now tried in the mouth, utilising the intended path of insertion. If the framework does not seat fully, no attempt should be made to force it into place, as subsequent removal from the mouth may be extremely difficult. A systematic search must be undertaken to discover what is preventing complete seating. Any areas of abrasion on the cast may indicate the location of inaccuracies in the framework. Clinical examination with a mouth mirror may reveal interfering contacts between framework and teeth. Gentle rocking of the framework may reveal a discrepancy of fit acting as a fulcrum.
Trial insertion of the metal framework
More precise location of any interference may be achieved by the use of disclosing aids such as this soft wax which is melted and flowed on to the suspect area of the framework. The framework is then seated as far as it will go, withdrawn and inspected to see if initial contacts between the framework and teeth are visible as areas where the disclosing wax has
Once the framework is fully seated in the mouth, its stability is assessed. A decision as to whether an altered cast impression is required must then be made before obtaining the definitive recording of the jaw relationship.
The fit and positioning of all the component parts of the framework are again assessed, including the extension of the mandibular major connector in relation to the functional depth of the sulcus. If unsatisfactory, a new impression and casting are required.
been displaced, exposing the metal. These contacts can then be eliminated.
Trial insertion of the metal framework
Care must be taken to avoid adjusting those portions of connectors that are occlusal to the survey lines. If material is removed from these areas a space will be created between denture and tooth surface into which food can pack. Anything other than relatively minor adjustments to the framework indicates a generally poor fit, and consideration must be given to retaking the master impression and obtaining a new framework.
When opposing natural teeth provide an occlusal stop, care must be taken to check that the framework does not alter this occlusal relationship, eg by separating the teeth. The patient’s comments are valuable in detecting the presence and location of occlusal prematurities. Such comments must be supplemented by visual assessment, the use of articulating paper to mark occlusal contacts, and testing the ability of any teeth providing an occlusal stop to grip a strip of thin metal foil (shimstock). Premature occlusal contacts must be eliminated by selective grinding until the desired jaw relationship is established.
Altered cast technique
When a distal extension saddle is constructed on a cast poured from a mucostatic impression, the differential in the support offered by the abutment tooth in its relatively incompressible periodontal ligament and the more displaceable denture-bearing mucosa is greatest. As a result, the tendency for the distal extension saddle to sink under occlusal load and pivot about the rest on the abutment tooth is increased.
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The objective of the altered cast technique is to reduce the support differential for a distal extension saddle by obtaining a compressive impression of the edentulous area under conditions which mimic functional loading. The distribution of load from the denture to the residual ridge is thus improved and the denture is more stable.
Acrylic resin tray material is added to the framework to form a base that covers the relevant edentulous area. It must be of sufficient thickness to be rigid. At the chairside the periphery of the base is inspected for under- or over-extension and adjusted accordingly. Any undercuts in the impression surface are removed. This surface is dried and zinc oxide impression paste or medium-viscosity silicone impression material applied.
The framework is placed in the mouth and great care must be taken to ensure that it is seated on the teeth by pressure on the occlusal rests and indirect retainers only. There must be no finger pressure applied to the base area, nor must the opposing teeth be allowed to occlude on any part of the framework. Once the framework is fully seated, border moulding is carried out.
When the impression material has set, the framework is removed from the mouth and the impression inspected. Any errors must be corrected by appropriate modification or by retaking the impression.
In the original approach to the altered cast technique the impression is developed using a specially formulated wax that flows readily at mouth temperature. This technique has the advantage of allowing progressive modification of the impression until an ideal result is achieved. However, it requires significantly more chairside time than the technique described and employs a commercial wax (Kerr’s Korrecta Wax No 4) that is not readily obtainable, or a mixture of waxes (75% paraffin wax, 25% yellow beeswax) that needs to be specifically prepared.
Once a satisfactory impression has been obtained the need for an extra clinical stage to record the jaw relationship can be avoided by adding wax rims to the framework at the chairside and proceeding with the recording at the same appointment.
When the completed impression has been conveyed to the laboratory, the relevant edentulous areas are cut from the original master cast. The framework is carefully and accurately seated on the teeth.
Finally, a new composite cast is produced by pouring artificial stone into the saddle impression.
When the acrylic tray is removed from the framework it will usually be seen that the metal ‘foot’ attached to the spaced mesh has lost contact with the underlying ridge. If this is the case a small portion of cold-curing acrylic resin should be added to the mesh at this point to re-establish the contact and to support the framework on the cast.
Rebasing the completed RPD is an alternative approach to the altered cast impression for reducing the support differential between mucosa and abutment tooth. A suitable impression material, such as zinc oxide/eugenol impression paste, is applied to the acrylic fitting surface of the relevant saddles after removing any undercuts, and an impression taken with the denture being seated by pressure on the occlusal rests and indirect retainers only. Pressure is not applied to the occlusal surfaces of the artificial teeth. The resulting impression is used to rebase the saddle
A disadvantage of this method is that it will usually disrupt the evenness of occlusal contact in the saddle area by creating premature contacts posteriorly. The occlusal correction required can be quite considerable.
Instructions to the laboratory
Beside general information about the patient, the dental practice and confirmation that the clinical items have been disinfected, the following information and requests should be entered on the laboratory prescription sheet.
12 The distal extension edentulous areas should be trimmed from the cast, the framework accurately seated and new model material poured into the altered cast impressions.
13 If the metal ‘foot’ beneath the distal extension saddle has lost contact with the ridge, cold-curing acrylic resin should be added to re-establish the contact.
14 The casts should be re-articulated on the chosen articulator using the definitive recording of the jaw relationship if this was obtained after the altered cast impression was taken. Otherwise the addition of wax rims to the framework should be requested so that the recording can be made at the next visit. If teeth are to be added to the framework for the next appointment the following additional information will be required.
15 The shade, mould and material to be used for the artificial teeth.
16 The desired arrangement (rotation, inclination, spacing, etc.) of any anterior teeth.
Trial insertion of waxed-up dentures
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his is the last stage at which modifications can be made before the wax is replaced by acrylic resin. A careful routine must be followed to prevent any errors from continuing through to the finished dentures.
Wax try-in for metal dentures
Each denture should first be examined on the articulated casts.
Wax try-in for metal dentures
The positioning of any posterior teeth is compared with the position of the remaining natural teeth and with the prescription supplied to the laboratory via the occlusal rim if this is available. For example, teeth on bounded saddles (e.g. 25 and 26) should be in line with the buccal surfaces of the natural teeth. Palatally placed teeth (e.g. 15 and 14) will encroach on the space for the tongue. Tooth positions will need to be confirmed on intra-oral examination.
Wax try-in for metal dentures
The arrangement of the anterior teeth should be pleasing to the eye and conform to any requests on the laboratory card. The labial surfaces and incisal edges should harmonise with the abutment teeth. If incisal wear is present on the natural teeth it should be simulated on the denture.
The appearance of the incisors in (a) is less acceptable than that in (b). The appearance may need to be modified after both the patient and the dentist have had the opportunity to view the denture in the mouth.
The intercuspation of the teeth should be even, and in order to reduce the magnitude of the potentially damaging lateral forces, as much balanced occlusion and articulation as possible should be provided within the constraints imposed by the remaining natural teeth. The natural teeth should, wherever possible, act as a guide.
Wax try-in for metal dentures
Wax flanges should be of a thickness and extension corresponding to the amount of bone resorption in the area so that they only replace the tissue that has been lost, restoring the former contour of the alveolar ridge. Mesial and distal borders should be thin so that the flange blends with the adjacent mucosa, thus avoiding food trapping and promoting patient comfort.
Wax try-in for metal dentures
If the path of insertion and withdrawal permits, the lateral borders of any anterior flange should be thinned and should terminate over the convexities produced by the roots of the abutment teeth. This arrangement should also permit the labial flange to restore the papilla of the abutment tooth next to the edentulous space. The positioning and contour of papillae and gingival margins around the artificial teeth should harmonise with those of the adjacent natural teeth.
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Wax try-in for metal dentures
A common error, which creates a poor appearance, is to place the gum margin of the artificial maxillary premolars at a lower level than that of the adjacent natural teeth (a). This may be overcome by careful waxing up and by the selection of an artificial tooth of appropriate crown length (b).
Wax try-in for metal dentures
The borders of mucosa, or partially mucosa-supported saddles, should extend to the full depth of the sulci recorded on the cast. This is so that the occlusal forces may be distributed as widely as possible and so that the adjacent musculature may be utilised to reinforce the retention and stability of the prosthesis.
Wax try-in for metal dentures
If the chosen path of insertion and withdrawal for the denture does not eliminate undercuts on the labial or buccal sides of the ridge, the flanges should be thinned as they pass over the survey line and end approximately 1mm beyond it.
The dentures are now seated in the mouth along their planned path of insertion so that the fit, positioning of all components and flange extension can be checked by visual inspection. Functional movements of the lips, cheeks and tongue should not displace the denture. The relationship of the artificial teeth to the soft tissues should be assessed to determine whether the prescription supplied by the occlusal rims has been followed. The vertical and horizontal jaw relationships are checked utilising the patient’s comments, visual assessment and shimstock. If natural teeth provide an acceptable occlusal stop it is important to ensure that these and the artificial teeth are in even contact. If natural teeth are not determining the jaw relationship, it is important to ensure that there is even contact in the retruded jaw relationship at the desired occlusal vertical dimension.
Wax try-in for metal dentures
The patient must maintain only the lightest possible occlusal contact while the occlusion is being checked, otherwise any premature occlusal contact may be masked by distortion of the denture base, by displacement of the mucosa or, as shown here, by movement of the trial denture away from the tissues.
Correction of significant occlusal errors will require the replacement of the artificial teeth with wax rims so that the jaw relationship can be re-recorded.
Wax try-in for metal dentures
The shade, mould and arrangement of the artificial teeth should harmonise with the natural teeth.
The incisal edges of the natural anterior teeth tend to follow the curve formed by the lower lip when smiling. Reproduction of this relationship when positioning artificial anterior teeth can contribute significantly to a pleasing appearance.
The patient may be able to recall distinguishing features of the missing natural teeth or may be in possession of suitable photographs. Remember that a totally regular arrangement of artificial teeth almost always looks artificial.
Wax try-in for metal dentures
On occasion, seemingly bizarre requests from the patient may be accepted, provided that they do not compromise the stability, retention and function of the denture. If the request is not met, the denture may be totally rejected by the patient. Indeed, tooth arrangements that appear exaggerated out of the mouth are often acceptable in vivo as seen on this completed denture.
Wax try-in for metal dentures
The smooth surface of the flange shown here should be avoided if the flange is likely to be visible during function as it produces an artificial appearance. Instead, the flange should be stippled and contoured to mimic the mucosal surface and break up reflected light in a more natural manner.
The unsatisfactory appearance is also due to the difference in shade between 11 and 21 and to the slight discrepancy in the incisal level.
Wax try-in for metal dentures
Any stains to be incorporated in the teeth or acrylic resin flange should be indicated on a drawing attached to the laboratory prescription card.
Wax try-in for metal dentures
These instructions are particularly important where there is pigmentation of the mucosa. Failure to tint the flange to match the adjacent mucosa will result in the highly unsatisfactory appearance shown here.
Wax try-in for metal dentures
Carefully planned and executed tinting of the labial flange can create this convincingly natural result.
The appearance of the trial denture must always be discussed with the patient, using a mirror (preferably wall-mounted to ensure that viewing takes place at conversation distance) to view the situation before and after any modification. Approval of the appearance must be obtained before the denture is processed.
Wax try-in for acrylic dentures
Each denture should first be examined on the articulated casts.
Wax try-in for acrylic dentures
The designs should be checked against the prescription supplied to the laboratory. Wrought rests and clasps should be omitted at this stage as they cannot be securely attached to the trial denture. They are therefore liable to move during insertion of the try-in so that their contribution to retention and stability cannot be assessed.
Wax try-in for acrylic dentures
In situations where the gingival margin is to be left uncovered, the border of the trial denture is examined to ensure that it is at least
Wax try-in for acrylic dentures
Where the wax contacts natural teeth, it must do so at or above the survey lines (*). If it ends below the line, a gap between acrylic and tooth will result when the completed denture is inserted which permits denture movement and food packing. Where the tooth surface is not undercut, relief should not be provided for the gingival margins.
The positioning of the teeth, the contouring of the wax flanges and stability of the denture on the cast are checked as described previously.
It is important to ensure that unwanted undercuts have been blocked out as requested on the laboratory card. If, as in the illustration, wax has been used for this purpose, the cast must be duplicated prior to the processing of the denture.
The dentures are now seated in the mouth along their planned paths of insertion. Fit and stability are carefully assessed. Allowance must be made for the inexact fit of the baseplate. The flange extension is checked and appropriate corrective measures undertaken.
Wax try-in for acrylic dentures
When an acrylic connector is to be fully extended posteriorly, it should terminate just anterior to the vibrating line where movement of the soft palate begins (here marked with indelible pencil). A groove, the post- dam, is cut into the cast in this position, extending through each hamular notch. The depth and width of the groove depends on the tissue compressibility as determined by palpation. The groove is generally deeper and wider laterally in the palate than in the midline.
Wax try-in for acrylic dentures
The post-dam has a vertical posterior wall and is chamfered anteriorly. This permits the posterior border of the palatal connector to be thinned and turned into the tissues, adding to patient comfort and creating a posterior seal.
Narrower grooves, their depth again determined by clinical assessment of tissue compressibility, are also cut into the mucosal areas of the cast along the other proposed borders of palatal acrylic connectors. These ‘pin-dams’ produce close adaptation of the borders, reducing the ingress of food.
The positioning of the posterior teeth, the jaw relationships, and the appearance are checked as described previously.
Instructions to the laboratory
Beside general information about the patient, the dental practice, date of the next appointment and confirmation that the clinical items have been disinfected, the laboratory prescription sheet should include a list of any modifications to be carried out to the waxed-up dentures or casts. It is advisable to have another trial insertion appointment after anything but the most minor modifications, and this is mandatory after re-recording the jaw relationship.
If the dentures are to be finished, request the following. 1. Duplication of the cast if the unwanted undercuts are currently blocked out in wax, or if the finished denture is to bt fitted back onto a duplicate cast in the laboratory. This latter step is recommended as it helps to ensure trouble-free insertion of the completed denture at the next appointment.
2. The addition of any wrought clasps or rests omitted from the trial denture.
3. Corrections of any errors noted in the trial dentures, eg failure of any waxwork contacting the teeth to extend to the survey lines.
In certain situations where the aesthetic requirements require it the following may also be included.
4. The shade to be used for the pink acrylic resin.
5. Any special finish (eg stippling) to be applied to the surface of the acrylic resin.
6. A diagram of any stains to be incorporated into the pink resin or teeth.
Instructions to the laboratory
Beside the general information about patient, dental practice, date of the next appointment and confirmation of disinfection of clinical items, the following information should be provided on the laboratory prescription sheet.
17 If the altered cast technique is to be employed at the next appointment, the work authorisation should request the addition of acrylic resin tray material to the framework to cover the distal extension edentulous areas.
18 Any additional laboratory alterations of the framework that are required. If teeth are to be set up on the framework for the trial insertion of the waxed-up denture the following additional information will be required:
19 The shade, mould and material to be used for the artificial teeth.
20 The desired arrangement (rotation, inclination, spacing, etc.) of any anterior teeth.
Valplast Partial Denture, a flexible, biocompatible, thermoplastic nylon with unique physical and esthetic properties. Its translucency allows the patients natural tissue color to appear through the material. It has the advantage of not showing any metal and as a natural look. Valplast can be used with metal to increase strength and esthetics.
Precision Attachment Partial Dentures, similar to a key fitting into a keyhole. A crown that is placed over your tooth contains the “keyhole.” The denture contains the “key.” When you put in your denture, the “key” fits into the “keyhole” in the crown. This type of denture looks better because no clasps are visible. It also fits tighter. However, it does take more skill to place in the mouth because the “key” must fit exactly into the “keyhole.”
Conventional Partial Dentures, consists of metal clasps that are C-shaped, I-shaped and Y-shaped 9parts of the denture framework). They fit around neighboring natural teeth. These teeth may require shaping to help hold the clasps and keep the denture securely in place.
