Anatomic setting on the glass

Anatomic setting on the glass. Test structures of full dentures.

Laboratory stages of complete dentures making..

Clinical stages

First visit

obtaining anatomical impressions (alginate material is usually used for making impressions ). Similar impressions are taken at partial defects of dentition

Second visit:

Obtaining functional impression (with thermoplastic or silicone mass). Is obtained by special samples

Third visit:

Determination of the central relationship of the jaws, the choice of form and color of teeth, prosthetic plane determination, drawing landmarks for setting the teeth

Fourth visit:

Check of  prosthesis structures in the mouth

Fifth visit:

Fitting the prosthesis to the patient jaw and its correction

Laboratory stages

1.                  Getting a model from plaster, defining the boundaries of the denture base and making an individual spoon

2.                  Production of a model(better use highly strong varieties of gypsum). Manufacture of wax patterns with bite rollers

3.                  Strengthening plaster models in an occludor or articulator, torus and exostosis isolation, setting artificial teeth in wax basis

4.                  Final modeling of a denture base, denture plastering in a flask, replacing wax on plastics, polymerization, grinding and polishing the prosthesis

5.                  The final polishing of prosthesis

          

Devices that recreate movements of the mandible:

1. Occludors.

2. Articulators universal (Ghanau, Hite).

3. Articulators medium (Sorokin, Giza)

 

Methods of making individual spoons:

• individual spoon from standard base plates (AKR-P) •
• individual plastic spoon with hot wax immediate polymerization
• Cyto method of single-stage spoon
• photopolymerplastic spoon
• fast-hardening plastic spoon
• fast-hardening plastic spoon with bite rollers

 

Settingteethmethodsduringcomplete removable denturesmanufacture:

• teethsettingontoothlessupperjawatpresence of lowerdentition
• classicteethsettingon toothless jaws
• anatomic teeth setting after Gizi
• teethsettingafter Vasiliev
• teethsetting after Ganau
• teethsettingat anterior jaw relationship  
• teeth settingat prognathic jaw relationship
• teeth settingafter Sazur
• teeth settingon spheres

Gerber’s (1979) minimum requirements for complete dentures must be met when arranging artificial teeth. They are as follows:

• “Complete dentures should restore the facial appearance with a personalized and natural look.”
• “Complete dentures should preserve the residual tissue structures of the gnathodynamic system.”
• “Complete dentures should attempt to ensure adequate masticatory function and enhance clear phonation.”

Establishing Tooth Width

In keeping with Gerber’s requirements, the esthetic components of the anterior tooth arrangement must not be dissonant with a patient’s facial appearance.

Establishing maxillary anterior tooth width can be aided by observing the relative widths of the base (ala) and the bridge of the nose. For tooth selection that is harmonious with a patient’s facial appearance, the incisal width of the central incisor should reflect the width of the base of the nose, and the width of the lateral incisor should reflect the width of the bridge of the nose. That is, when the base of the nose is wide, the width of the maxillary central incisor should be wide. If the bridge of the nose is narrow, the lateral incisors should be narrow.

The line joining the distoincisobuccal corners of the central incisors and the base of the nose must be parallel.

Symmetry of the face should be considered in determining the vertical tooth axes, particularly the central incisors.

Selecting Tooth Forms

The shape and form of teeth should be selected in harmony with facial forms:

• Square face with square forms
• Oval face with oval forms
• Triangular face with tapered forms

Identification of facial form may be impaired in the edentulous patient due to inadequate soft tissue support and loss of vertical dimension of occlusion. For this reason, determination of facial shape should occur only when the occlusion rims are in the mouth and the appropriate vertical dimension and the patient is in centric relation.

Arranging Artificial Teeth

To assist compliance with Gerber’s requirements, there are seven anatomic landmark guidelines that should be followed when placing teeth:

1.     The incisive papilla is an invaluable reference point for correct placement of the maxillary anterior teeth and the anterior arch form. The maxillary anterior teeth lie to the facial of the incisive papilla. In the young, the line connecting the tips of the canines transverses the incisive papilla. As the alveolar ridge is increasingly resorbed with increasing years since loss of the teeth, the line moves posteriorly and may eventually pass through the posteriorly extent of the papilla.

2.     The distance from the middle of the incisive papilla to the labial surface of the maxillary central incisor is typically 8 mm. Because this distance is fixed, the apparent curvature of the anterior arch form will increase as a person experiences more alveolar ridge resorption.

3.     The labial surface of the canine is normally 10.5 mm from the lateral aspect of the anterior rugae.

 

4.     The distance between the tips of the canines is the same as the width of the base of the nose.

5.     Canines are immediately inferior to the side of the nose. They must not be positioned directly at the corners of the mouth when the patient smiles, so the “buccal corridor”—the facial surfaces of the premolars and first molar—can be visualized between the cuspid and the corners of the mouth.

6.     The width of the central incisor approximates the width of the philtrum.

7.     First premolars appear at the head of the “buccal corridor” and behind the canine.

Arranging Anterior Teeth

The buccal and facial surfaces of the prosthetic teeth should follow the facial contour established by the wax rim. In many cases it may be helpful to employ small amounts of either cream or powder denture adhesive during the try-in appointment to prevent the possible displacement of a baseplate that may be non-retentive due to distortion of the baseplate material, blocked-out undercuts, or the absence of a posterior palatal seal. Adhesive product should always be removed from the fitting surface of a baseplate before it is reseated on the master cast.

Selecting Tooth Shade, Form, and Alignment

Selecting tooth shade, form, and alignment is best accomplished prior to setting posterior teeth. Once the anterior teeth have been selected and set, the dentist needs to evaluate the midline in the mouth to ensure acceptable tooth placement.

The Smile Line

Once the midline is established as correct, the length, contour, and position of the incisal edges can be checked. The final evaluation of the anterior arrangement, which will include the gingival contours and margins, will be completed at the last try-in.

Final evaluation at last try-in

In this example, the central incisors appear too short and the canines appear too long.

Maxillary Anterior Teeth

A lifetime of gravity leads to slightly different soft tissue positions in older persons’ lips and faces. In the younger patient, approximately 1 mm of the incisal edge of the maxillary anterior teeth should be visible when the upper lip is relaxed. In an older patient, the maxillary incisal edge is likely right at the edge of the upper lip, and the mandibular anterior teeth will be more visible than one expects in a younger person.

Principles of Posterior Tooth Arrangement

The following are the general principles of tooth arrangement:

• Denture teeth must be within muscular balance between tongue, lips, and cheeks.
• The occlusal plane should be at or below the height of contour of the tongue.
• Proper mastication and effective occlusion requires at least three pairs of antagonistic teeth on each side.
• A cusp-to-fossa relationship should be established whenever possible.
• During function, the forces on each tooth should have a stabilizing effect on the denture (independent of cross-arch equilibration).

Arranging Posterior Teeth

Proper selection of tooth forms and careful execution of the chosen occlusal arrangement can compensate for an unfavorable residual ridge. Cross-tooth/cross-arch balanced articulation is required during empty mouth movements, such as swallowing and speaking. Canine guidance is not advised for complete denture occlusion.

Balanced Occlusion

Shown is an example of the harmonious arrangement of the maxillary and mandibular denture teeth in a balanced occlusion relationship. Shown as well is an occlusal view of the maxillary posterior teeth. Note the mesial fossa of the first premolar and the palatal cusps of the posterior teeth lie along the line describing the alveolar ridge crest.

Facial View of Mandibular Posterior Teeth

Shown is an occlusal view of the mandibular posterior teeth in a balanced occlusion relationship. Note the buccal cusp tip of the first premolar and the central fossae of the posterior teeth lie directly over the line describing the alveolar ridge crest (which can be approximated by the line connecting the mandibular cuspid cusp tip to the medio-lateral center of the retromolar pad).

Lingual View of Teeth in Balanced Occlusion

Note the dominant cusp-to-fossa relationships of the maxillary palatal cusp and the mandibular central fossae in this balanced setup. An observation of the setup from the facial would reveal a similarly tight intercuspation between mandibular buccal cusps and the maxillary fossae. With an arrangement such as this, both cross-tooth and cross-arch contacts are maintained during eccentric movements:

• On the working (discluding) side, the maxillary buccal cusps rise on the facial surfaces of the mandibular teeth as the palatal cusps are contacting the facial cusp inclines of the mandibular lingual cusps, providing the cross-tooth contact.
• On the balancing (non-working) side, the maxillary palatal cusps rise along the lingual cusp inclines of the mandibular facial cusps, providing the cross-arch contact.

A variation on the balanced occlusion is the lingualized occlusion. This arrangement is preferable for patients with severely resorbed alveolar ridges because the displacive forces between the opposing dentures in excursive motions are minimized. In lingualized occlusion, the cross-arch balance of the traditional balanced arrangement is preserved; but the “cross-tooth” relationship of balanced occlusion in which the palatal cusp/mandibular central fossae relationship is paired with a mandibular facial cusp/maxillary mesial fossae relationship is reduced to only include the former.

In a lingualized set-up, the mesial fossa of the maxillary first premolar and the palatal cusps of the maxillary posterior teeth lie along or lingual to the crest of the ridge, just as in a balanced denture setup. In some cases it may be advantageous for the orientation of the maxillary posterior teeth to slightly splay away from the palatal midline.

Mandibular Teeth

In the mandibular arch of a lingualized setup, the buccal cusp tip of the first premolar lies over the crest of the ridge as with a balanced setup. But the fossae of the remaining posterior teeth are lingually displaced. This results in the buccal cusps of the maxillary second premolar and maxillary molars being placed out of contact. The resulting intercuspation is restricted to the more lingual cusp/fossa pair; the occlusion is “lingualized.”

 

Lingualized Occlusion, Lingual View

Note the distinct lingualization of the cusp-to-fossa relationship.

The final try-in is an important step in the fabrication of a complete denture and must not be overlooked. At this stage, while the teeth are still set in wax and adjustments to the setup can be easily made, the patient and the dentist can evaluate the trial denture and make corrections if necessary.

The final try-in may take multiple appointments, depending on the patient’s esthetic and emotional needs.

Evaluating the trial denture at the final try-in includes:

• Inspecting the trial denture on the master cast
• Positioning the teeth on the articulator
• Checking anterior teeth for shape, form, color, and function
• Checking posterior teeth for shape, form, color, and function
• Checking the denture base form
• Evaluating function

Each of these steps will now be discussed in greater detail.

To inspect the trial dentures on the master cast, the dentist should:

Once these characteristics have been verified, the dentist needs to position the trial dentures on the articulator and evaluate the:

The general esthetic impression is best judged when the patient is standing or is sitting in an upright position. Once the articulated casts and the trial dentures on the articulator have been found acceptable, the dentist should insert the trial denture and evaluate the anterior teeth to be sure they display the correct:

When the anterior set-up is deemed acceptable, the dentist then evaluates the posterior teeth for:

To check the denture base form, the dentist then:

Evaluating Function

Once the dentist is satisfied with the appearance and characteristics of the trial dentures under static conditions (with the patient at rest), many of the features just described must be assessed while the patient undergoes modest functional movements.

For instance, during the final try-in stage, the dentist must evaluate the vertical dimension for adequate space for the tongue during swallowing.

Additional aspects of the functional appraisal of the prosthesis will now be described.

Use of small amount of denture adhesive powder is helpful in building patient confidence at try-in stage

It is essential at this stage of prosthesis assessment that the patient build confidence iot only the esthetics but the function of the new denture as well. The inconvenience and embarrassment of a dropping maxillary denture or a floating mandibular interferes with the dentist’s appraisal of the trial prosthesis, and compromises the patient’s confidence in the likely successful performance of the new appliance. A small amount of denture adhesive can be used to help judge the appearance and speaking and other interocclusal functions, even as it dispels possible patient misgivings about the denture. Powdered adhesive, rather than cream adhesive, is advisable at this stage because the greater initial cohesion (“hold”) of cream-type adhesive may cause the operator to inadvertently distort the final wax try-in during removal.

Observing Facial Proportions

Observe the patient from every angle

To accurately appraise the quality of the prosthesis in function, the patient should be in a sitting position and should be observed from all angles. The dentist carefully watches the patient to check that the correct amount of the vermillion border is being displayed during speech, licking of the lips, and swallowing.

Maximum Intercuspation

Centric occlusion should correspond to articulator

Centric occlusion in the mouth and centric occlusion on the articulator must be identical. Should any discrepancy be evident at any stage of the trial denture appraisal, the following steps become necessary:

• A new bite registration is obtained;
• The mandibular cast is remounted;
• A second bite registration confirms the new mounting; and
• The teeth are reset according to the new interocclusal relationship and the intraoral and esthetic assessments are repeated.

Anterior Teeth

The dentist instructs patient to open the mouth slightly. The vermillion border should be supported by the denture teeth and not by the denture base. Younger patients should show more vermilion border and maxillary incisal edge than the older patient. When asked to pronounce “f” and “v” sounds, the patient’s lower lip should approximate the maxillary incisal edge effortlessly, and the enunciation should be distinct.

Mandibular Teeth

 

The mandibular teeth should be in contact with the lower lip, adjacent to the wet/dry border in a younger patient and extending superiorly about 1 mm in an older patient.

The dentist rechecks the vertical axis of the anterior teeth relative to the base of the denture to ensure the dominant angles of the face are in symmetry with the orientation of the incisors.

 

Lip Support

 

The labial surfaces of the flange and the anterior teeth provide lip support, but there are limitations to what can be accomplished with a denture.

 

For instance, thickening the maxillary anterior flange will not successfully remove vertical wrinkles in the upper lip and will distort the philtrum, giving it a “plumped” and unnatural appearance.

 

The facial surfaces of both the maxillary and mandibular denture should ideally feature subtle depressions to accommodate the orbicularis oris muscle, which will contribute to the retention of the prostheses. In the maxillary arch, the depression should be located entirely within the denture base, superiorly to the prosthetic teeth. In contrast, the depression in the mandibular prosthesis should be created between the teeth and the denture base.

Cheek Contact

The cheeks and the tongue play key roles in positioning food onto the “occlusal table” formed by the mandibular teeth. As such, the proper amount and location of cheek contact is important for satisfactory function. The mandibular posterior teeth should be in a zone between the cheek and the tongue, impinging oeither.

Positioning Mandibular Teeth Relative to the Tongue

Difficult to evaluate

Chewing cannot be evaluated during the trial denture try-in. However, evaluating for adequate tongue space can be accomplished. The dorsum of the tongue should be approximately level with the occlusal plane.

When all of the preceding criteria have been checked and adjusted as necessary, the posterior palatal seal should be located prior to terminating the try-in appointment.

The maxillary denture should terminate at the most posterior extent of the hard palate, where it transitions into the moveable tissues of the velum or soft palate. This location can be determined by having the patient say Aah! (which elevates the soft palate) or by blowing through their obstructed nose (which forces it downward). The palatal tissues that do not move during either of the preceding actions are underlain by osseous tissue; the tissues that do move mark the extent of the soft palate. The line between them—the “vibrating line”—will correspond to the most posterior extent of the denture base.

The vibrating line is gently wiped with gauze to remove mucus secretions and then marked with an indelible pencil.

Shortening the Record Base Border

The dentist then reinserts the maxillary trial denture. The patient is once again directed to blow through the obstructed nose; this will bring the marking on the palate into contact with the maxillary trial denture base.

The dentist then shortens the base to the indicated length and watches the soft palate as the patient says Aah. The movement of the soft palate should originate at the most posterior extent of the trial denture base. The dentist can further verify the border length in the mouth by palpating the soft palate with a finger or the end of the intraoral mirror handle. The hard palate should not be evident as the finger moves posteriorly.

The trial denture is then removed. The dentist should then gently palpate the mucosal tissues just anterior to the vibrating line to ascertain the degree to which they will tolerate the deliberate distortion introduced by the posterior palatal seal. This palpation should continue laterally to the pterygomaxillary area; the region immediately posterior of the tuberosities. This area is best palpated with the edge of the intraoral mirror.

Designing the Posterior Palatal Seal

Compensation for polymerization shrinkage

The posterior palatal seal will ensure the posterior extent of the maxillary denture, which has a tendency to move away from the master cast during the shrinkage that accompanies the heat curing of methylmethacrylate resin, remains in contact with the palatal tissues. If this contact is not maintained, the peripheral seal of the maxillary denture will be broken and the denture will be non-retentive. To maintain that contact despite the shrinkage of the denture, the tissue surface of the posterior portion of the denture is deliberately extended slightly into displaceable glandular and areolar tissue overlying the hard palate and the pterygopalatline notches. This is accomplished by removing a discrete amount of stone in the maxillary master cast when palpation has demonstrated the patient will tolerate it without discomfort.

Carving the Palatal Seal

A groove is carved and beveled anteriorly

While the patient is still present and the tissue consistency of the posterior palatal seal area fresh in the dentist’s memory, the posterior palatal seal should be carved into the master cast.

The shape of the posterior palatal seal will differ from patient to patient, according to the relative tautness or flaccid nature of the tissues. The groove that is carved into the master cast should be deepest in its most posterior extent (where the tissue is transitioning into the soft palate and is therefore most displaceable) and then beveled anteriorly, as guided by the findings of the intraoral palpation. The depth of the dam is typically 0.5-1.5 mm deep at its most posterior extent. Consistent with the findings from the intraoral palpation, the carving of the posterior palatal seal should continue into the tissues posterior to the tuberosities.

Patient Approval

The goal of the final try-in is to gain patient approval. Once the patient and dentist are satisfied with the product, the trial denture is ready to be processed.

An esthetic result in complete denture treatment is achieved through a deliberate combination of color, arrangement, and orientation of prosthetic teeth. Rather than a precise science, development of the trial denture requires a blending of qualitative and quantitative factors, each weighted according to patient’s preference and dentist’s experience. The occlusal scheme that is developed, in contrast, must adhere to certain clear principles of form and function in order to provide the patient with a result that is both esthetic and effective. Finally, the trial denture is generally evaluated at the same appointment at which the posterior palatal seal is designed. This course will review the factors that have been found to be most useful in selecting and arranging teeth, developing the occlusal scheme, and designing the post-dam.

The Construction of Complete Dentures

Complete dentures are constructed to restore normal speech, provide occlusal and facial support and adequate masticatory function.  They should have a pleasing appearance, be comfortable to wear, and not prejudice the health of the supporting tissues.  There can, however, be no guarantee that they will satisfy all these criteria for patients who have poor denture control skills, poor motivation, inadequate foundations, or intolerance to prostheses. 

Preparation of the mouth prior to treatment and the design of complete dentures is the responsibility of the clinician.

A)  CLINICAL PROCEDURES

Diagnosis and treatment plan

In order to formulate the treatment plan a medical and dental history should be taken and a clinical examination carried out, together with any appropriate investigations. Radiographs should only be taken when there are clear clinical indications. Previous dentures should be examined in conjunction with any complaints from the patient.  Any pathological conditions should be investigated and appropriate treatment provided in order to render the oral tissues healthy before final impressions are made.  Any elective surgery should be carried out at an appropriate stage.

There should be a clear treatment plan and expected outcome put to the patient, ideally in writing, so that they are able to make an informed decision of accepting the treatment proposed and related costs. It is well to remember that dentures are seen as goods and therefore subject to the Sale of Goods Act. This means that that they are suitable for the purpose for which they were made (i.e. to replace missing teeth) or according to the contract with explanation of any possible shortcomings.

 

 

Primary impressions

The requirements of the primary impressions are that they should accurately record clinically relevant landmarks of the edentulous mouth without excessive tissue distortion.  They should be made in rigid stock trays modified as necessary to fit the form of the denture bearing area.

Maxillary impressions should record the following:

i)          The residual ridge, tuberosities and hamular notches.

ii)        Functional labial and buccal sulci, including the fraena

iii)      The hard palate and its junction with the soft palate.

 

Mandibular impressions should record the following:

i)          The residual ridge and retromolar pads.

ii)        Functional labial and buccal sulci, fraena and the external oblique ridges.

iii)      The lingual sulcus, lingual fraenum, mylohyoid ridge and retromylohyoid area.  The impression should be recorded with the mylohyoid muscle in a functional raised position.

 

Where the impression is over-extended in relation to the functional depth of the sulcus, a clear indication should be made on the impression or resultant cast to help the technician in the construction of special trays.

Appropriate spaced or close fitting rigid trays should be requested in the laboratory prescription, depending on the type of impression material and technique to be used and the anatomy of the denture bearing area.  The site for any stops, the type and position of the handle, as well as the amount of spacing should be stipulated by the clinician.

Working impressions

These should record the entire functional denture bearing area to ensure maximum support, retention and stability for the denture during use.  Each special tray should be examined in the mouth and adjusted as necessary to satisfy the above requirements.

To ensure adequate lip and cheek support the maxillary impression should show an intact rounded record of the labial and buccal sulci, together with the fraena.  It should extend posteriorly to the hamular notches and just beyond the junction of hard and soft palates.  The mandibular impression should show an intact rounded record of the labial, buccal and lingual sulci, including the fraena.  It should extend posteriorly to cover the retromolar pads. 

Impressions should be boxed or the borders marked appropriately before the casts are poured in order to preserve an accurate record of the functional depth and width of the sulci.

 

Recording jaw relations (maxillo-mandibular relations)

The bases which carry the occlusal rims should be rigid and stable.  The upper rim is modified to give correct lip support, which will vary from patient to patient.  The incisive papilla provides a useful biometric guide to the prominence of the rim, its centre lying 8-10 mm palatal to the labial surfaces of the maxillary central incisors (in the natural dentition).  Patients’ wishes, or previous satisfactory dentures, may sometimes dictate otherwise.

 

The length of the upper rim should be adjusted to indicate the level  for  the  upper  anterior  denture  teeth  and  the  antero-posterior (occlusal) plane made parallel to the interpupillary and alar-tragal lines (unless facial asymmetry warrants an alternative).  A centre line should be marked on the upper rim.  This will usually be coincident with the midline of the face. High and low smile lines, and the corners of the mouth may also be indicated. It may also be advantageous to mark the centre line of the lower rim.

The occlusal vertical dimension should provide for most patients a minimum inter-occlusal clearance (freeway space) of 2-4 mm in the premolar region.   It is established by adjustment of the lower occlusal rim and verified using various techniques of clinical measurement.

Failure to provide sufficient freeway space may lead to muscular discomfort, pain involving the denture bearing areas, and possible increased bone resorption. Excessive freeway space may lead to cheek biting, angular cheilitis, poor appearance and contribute to discomfort from the temporomandibular joints. Progressive incremental additions of acrylic resin to the occlusal surfaces of existing or diagnostic dentures may be necessary before a satisfactory occlusal vertical dimension can be established. It is essential to obtain a patient’s consent before making modifications to their existing dentures.

The horizontal jaw relationship to be recorded at the established occlusal vertical dimension is retruded contact position (RCP).  This is a reproducible position at which the denture teeth are placed in intercuspal position (ICP).  Once this position can be reproduced, the bucco-lingual width of the occlusal rims should be adjusted to identify the “denture space” (neutral zone).  This is important in order to provide tongue space, facial soft tissue support, and denture stability.  In some instances functional recording of the mandibular denture space may be appropriate using a suitable impression material on a stable base.

 

The occlusal rims must be located securely together in RCP in the mouth using an accepted technique. Small V-shaped notches may be cut bilaterally in the occlusal surfaces of the rims prior to the use of a suitable registration material. Wax as a recording medium in these circumstances is not generally recommended. Zinc oxide/Eugenol impression paste or rigid silicone registrations have the advantage of relocation if the rims become detached during transportation. The use of a face-bow may be desirable with a semi-adjustable articulator, although in the majority of situations an average value articulator will suffice.  In this latter case, any change in occlusal vertical dimension will require new records to be made.

The prescription accompanying the registration should give details of mould, shade, material, and manufacturer’s brand of chosen teeth.  A diagram may help the technician with the arrangement.  The cusp form, material, and size of posterior teeth should be selected.  The number of teeth to be used and their anatomical type should be recorded.

 

When setting up the teeth it is usual to limit the lower occlusal table to the horizontal part of the ridge and to avoid placing teeth over an inclined plane of the ascending ramus. Where patients have extremely resorbed lower ridges, and have had problems with previous lower dentures, the use of premolars rather than molars for the lower set up is suggested.

An impression of a previous denture may be helpful to the technician where a particular form of anterior tooth arrangement is to be repeated.

Photographs which show the patients natural teeth and facial appearance may also be helpful.

The trial insertion

The occlusal plane, occlusal vertical dimension, and RCP should be verified as correct.  Tooth position and arrangement should provide adequate lip and cheek support and tongue space, allow clear speech, and give a pleasing appearance to the patient.  Where alterations are required to the horizontal or vertical jaw relationship, a new recording will be required and a re-try necessary.

The position of the posterior palatal border of the maxillary base should be examined to ensure it is correctly extended just beyond the junction of hard and soft palate lying on displaceable but non-moving tissue.  The foveae palati act as a useful landmark, lying 2-3 mm behind the posterior margin of the hard palate.  It is the clinician’s responsibility to cut a post dam on the master cast in the appropriate position unless a functional post dam was incorporated into the final impression.  The patient should be given the opportunity to see the trial dentures in place at this stage.  It is wise for them to agree verbally (and ideally in writing) that the appearance is satisfactory.

The extension of the lower base onto the retromolar pad should be clearly indicated on the cast for the technician.

Insertion of the dentures

The denture bases should be inspected and any remaining surface blemishes or defects removed.  Each denture should be inserted and assessed for retention, extension, appearance, and stability.  Factors assessed at the trial stage such as lip support, speech, and horizontal and vertical jaw relationships should be reconfirmed as correct.  Articulating paper or foil may be used to examine occlusion and articulation in the mouth, although this should be carried out with caution to avoid errors.

A pressure indicating paste or other suitable recording material may be used on the fitting surfaces of the dentures to indicate excessive tissue displacement.

A check record is a useful method for refining the occlusion, the dentures being re-mounted on the original articulator and adjustments carried out to provide correct articulation.  It is strongly recommended that the processed dentures are routinely remounted on the articulator following deflasking  (using the split-cast method), and the occlusion adjusted and ground in to overcome processing inaccuracies before returning to the clinic/surgery. 

A check record may not then be necessary at the insertion stage, but could be valuable at the review appointment after the dentures have been worn for a period and the supporting tissues have adapted to them.

Instructions (both verbal and written) on the use and care of dentures should be given to the patient, and a review appointment made approximately one week later.

Inspection and review

At the review appointment, any adjustments should be made to the dentures in the light of the patient’s experiences or complaints.  The denture bearing areas should be examined for signs of trauma even in the absence of patient complaints.  The occlusion and articulation should be examined at this stage.

The importance of attending for regular review should be explained to the patient.

Addendum

The above guidelines are meant to cover techniques used in the different stages of complete denture construction.  However, it is accepted that variations may occur, some of which are listed below:

·        Copy/duplication techniques are extremely valuable for many patients, particularly the elderly. The techniques have been well documented^2-5 and enable reasonably similar copies of previous satisfactory dentures to be made with a minimum of clinical visits.

·        Making working impressions in a patient’s existing dentures may eliminate the need for primary impressions, special tray construction and occasionally jaw registration rims.

·        Using appropriate impression materials, and by modifying stock trays, acceptable working impressions can be made without the need for special trays in some situations.

Disinfection

In all cases due regard should be given to the disinfection of all materials/prostheses which pass from clinician to laboratory and vice versa, according to health and safety requirements. This can be accessed from the following address:

Current practice and disinfection agents are subject to change and it is a clinician’s responsibility to keep up to date on such matters.

B)  TECHNICAL PROCEDURES

The clinician is responsible for the provision of complete dentures.  At each stage the dentist should provide a clear prescription for the laboratory.  If the technical quality of the dentures is inadequate it is the clinician’s responsibility to have the problem remedied.

Primary casts and special trays

Surface moisture should be removed from the impressions after rinsing and before casting.  Plaster of Paris and dental stone (50/50 w/w) are vacuum mixed with water.  The impressions are cast using vibration to eliminate air bubbles and separated from the cast after 40 minutes.  The cast should record the depth and width of the sulci and be surrounded by a “land” width of at least 3mm.  The base should be 10 mm thicker than the deepest part of the impression.  The “land” area should always be recorded unless the extent of the special tray has been indicated on the impression by the clinician.

Special trays are made according to the clinical prescription, which will stipulate the amount of spacing (if any) and stops.  Handles must be designed to avoid distortion of the tongue or lips and finger rests are required in the premolar region on the mandibular tray to prevent the operator’s fingers distorting the soft tissues.  The borders of the tray should normally extend to the deepest part (or slightly short if border moulding techniques are to be used) of the functionally recorded sulcus, or to an outline on the cast made by the clinician.  In the maxilla it should extend posteriorly to the hamular notches and fovea palati ; in the mandible to the distal aspect of the retromolar pads.

Working casts and registration rims

Surface moisture should be removed from the impressions after rinsing and before casting.  Dental stone in the correct measure is vacuum mixed with water and the impression cast.  The thickness of the base and the width of the “land” is the same as for primary casts.

The base of the registration block should normally be made of a rigid material.  Close adaptation of the base to the working cast is essential for stability in the mouth and accurate registration of jaw relations.

Registration rims are usually made of wax.  The upper block should measure approximately 22 mm in height from the deepest part of the sulcus adjacent to the midline fraenum.  The equivalent dimension of the lower block should measure approximately 19 mm anteriorly

Wax rims are positioned bucco-lingually in the same place as the lost teeth, according to the amount of resorption that has taken place.  The occlusal surface of the lower rim passes posteriorly from its anterior edge to a point 2/3 up the retromolar pads.  The upper rim should be created using an occlusal rim inclinator so that in the mouth it can easily be adjusted to be parallel to the alar-tragal line antero-posteriorly.

 

Mounting and setting up

The registration rims are mounted on a semi-adjustable or average value articulator (according to clinical requirements), preferably using the split cast technique.  After noting the prescription for tooth arrangement, the maxillary anterior teeth are set up in accordance with the marked centre line, always conforming to the contour of the wax rim.

Unless the prescription says otherwise, or a neutral zone (piezograph) technique has been used, the mandibular posterior teeth are placed to conform to the buccal contour of the wax rim.  It is wise, particularly with flat lower ridges, to avoid the most posterior tooth being positioned over an inclined plane, and to achieve this, the last tooth should be at the posterior extremity of the horizontal part of the ridge.

The teeth are adjusted to allow balanced articulation in lateral and protrusive excursions.  Any part of the try-in base which was removed to facilitate registration is replaced unless this interferes with occlusal balance.

Processing and finishing

While in ICP on the articulator, the try-in is sealed to the casts with wax around the denture borders.  Following processing, the dentures (still on casts) should be replaced on the articulator, by means of the split cast, and any processing errors removed by occlusal adjustment.

Finishing and polishing is carried out carefully to preserve the full width and depth of the recorded borders.  Apart from the removal of imperfections, the fitting surface remains untouched.  The completed dentures should be stored in clean water (with antiseptic as appropriate) after removal of traces of polish.  Denture identification is a desirable option with complete dentures.

Check record

Where this is requested, it is preferably carried out on the original casts if possible.  Failing this, the dentures may be remounted on an articulator using quick setting plaster and occlusal adjustments carried out.

Miraculous advancements in dentistry have been made since the inception of organized and intentional dental therapeutic intervention. Most recently, the advent and clinical refinement of dental implant therapy using root-form endosseous implants¹ is an example of one such advancement that has revolutionized the profession’s approach to prosthetic replacement of missing teeth. Additional revolutionary advancements ride on the heels of the ever-progressive digital world, making once cumbersome procedures (eg, radiology, treatment planning, impression making, prosthetic design, and prosthesis fabrication) more readily available, and in some cases, more accurate and precise. In fact, advances in the modern dental world are occurring at such rapid rates that the challenge for practicing dentists is to keep up with the latest materials, devices, and procedures, as well as the evidence basis for their clinical implementation.

Despite the remarkable advances impacting so many facets of modern dentistry, pockets of routine treatment seem to have remained relatively stagnant over time. For many practitioners, the routine provision of complete denture therapy includes procedures that seem to have escaped the progresses of modern dentistry. When considering today’s conventional complete denture treatment, it is interesting to note that many of the clinical and laboratory materials and procedures used remain essentially unchanged from their historical inceptions. A glance at key aspects of dental history^2-28 (Table 1) illustrates this point.

While today’s complete denture therapy incorporates several significant improvements, fundamental concepts and techniques remain remarkably similar to historical treatment approaches. Positive advancements have been made in the area of materials and a resurgence of useful therapeutic devices results in improved complete denture outcomes. In order to achieve the fabrication of successful, well-accepted conventional complete dentures, practitioners should thoughtfully combine historically proven concepts with modern materials and devices. This article provides a brief overview of several clinical concepts and new materials that have been used to enhance modern complete denture therapy.

Edentulous Impressions

The number of available edentulous impression procedures is a varied as practitioners interested in treating edentulous patients.^29-35 Subtle variations in the material or design of impression trays, impression material handling, border molding, management of the denture-bearing foundation, perceived delivery of pressure during impression making, patient-induced functional activity during the procedure, etc, will undoubtedly influence the resulting edentulous impression. Though most of these clinical procedures have enjoyed at least reasonable success, the relatively recent appearance of materials and devices unique to complete denture therapy may prove beneficial. New materials and new anatomically designed stock impression tray systems may facilitating accurate, pressure-controlled, definitive impressions without the need to develop primary casts and custom impression trays.

Practitioners should appreciate the following basic principles of impression making for edentulous patients³⁶:

• Impressions should extend to include the entire denture foundation within the health and functional tolerance of the supporting and limiting tissues.
• Impression borders should be in harmony with the anatomic and functional limits of the denture foundation and adjacent tissues. Therefore, impression borders should be identified using functional movements.
• Adequate space for impression material within the impression tray must be available.
• A guiding mechanism, or stop, should be available to accommodate the correct positioning of the impression tray relative to the edentulous ridge and associated tissues, particularly if multiple insertions of the impression tray are required.
• The impression tray and impression material should be made of dimensionally accurate and stable materials.
• Impression contours and dimensions should replicate intended contours and dimensions of the planned prosthesis.

A recently described method for edentulous impression making abides by these basic principles, uses readily available and anatomically designed stock impression trays (Figure 1 and Figure 2), incorporates familiar vinyl polysiloxane (VPS) impression materials, and is a relatively time-conservative procedure. This modern edentulous impression system has been previously been described in great detail.

The unique anatomically designed stock edentulous impression trays used in this impression procedure permit several advantages. The trays come in an acceptable variety of sizes, can readily be subtractively adjusted using standard acrylic resin burs, and permit thermoplastic manipulations with shape-stable results. Additionally, the impression system incorporates a wide range of viscosity-specific VPS impression materials that are typically very familiar to most practitioners.

Again, readers are encouraged to review previously published descriptive literature³⁷ for procedural suggestions for making edentulous impressions.

A variety of VPS impression material viscosities are available. Thoughtful application of viscosity-specific materials during the impression procedure and in different areas of the tray permits predictable tissue placement and control. VPS offers several potential advantages for making edentulous impression, including:

• Availability of different viscosities. For example, Aquasil Ultra Smart Wetting® Impression Materials (DENTSPLY Caulk, www.caulk.com) is provided in five viscosities (ie, extra low, low, medium, medium-high, and high).
• Convenient delivery system (ie, automix cartridges).
• Predictable material adhesion between sequential layers of different material viscosities.
• Materials with various working times are available to satisfy operator preference. For example, use of a fast-set material permits the operator approximately 30 seconds to dispense the material into the impression tray, 1 minute to insert the tray into the patient’s mouth and perform tissue manipulations, and then 1 minute to final cure.
• The material is sufficiently elastic with clinically acceptable tear strength.
• Newer VPS materials have been chemically modified to improve wettability and hydrophilicity.^38-41
• The material is generally biocompatible and does not possess an offensive taste or odor.

Steps used to make these modern edentulous impressions include: (1) develop stops in properly adjusted stock impression trays using a high-viscosity VPS; (2) complete border molding procedures using a high- or medium-viscosity VPS; (3) trim tray overextensions using an acrylic resin carbide bur; (4) reduce border molding and tray stops by 1 mm to 2 mm in all dimensions and according to the dictates of selective pressure impression making to provide adequate space for the final wash of the impression material; and (5) introduce medium-, low-, and extra-low–viscosity VPS materials into the tray and make the definitive impression (Figure 3, Figure 4, Figure 5, Figure 6). Again, readers are encouraged to visit previously published detailed descriptions of this procedure³⁷ for predictable clinical implementation.

The Central Bearing Device

The most appropriate relationship of the edentulous maxilla to the edentulous mandible when fabricating conventional complete dentures may be debated. However, most agree that achieving anatomically and physiologically optimal vertical and horizontal jaw relationships is important to successful therapy. It is the opinion of the authors that most clinicians skilled in modern complete denture therapy rely on centric relation as a physiologically stable and repeatable mandibular treatment position.⁴² Unfortunately, the ability to reliably record this interarch relationship is in part determined by the clinician’s detailed understanding of the anatomy and physiology of temporomandibular joint function, effective handling of clinical materials and devices, patient cooperation, and his or her skill and experience.

Historically, a number of techniques have been suggested for registering interarch relationships during complete denture therapy. These clinical techniques can be broadly classified as direct interocclusal records, graphic recordings, and functional records.⁴³ A graphic recording method dating to the turn of the 20th century,^44,45 but recently updated, involves use of a central bearing device. This device can aid the practitioner in the clinical achievement and registration of both horizontal and vertical jaw relationships and is particularly useful when muscle deprogramming of habitual mandibular closure is indicated.⁴⁶

Use of a central bearing device has been shown to be very precise.⁴⁷ The concept has recently enjoyed a resurgence of interest due in part to newly developed instrumentation (Massad Jaw Recorder System, Global Dental Impression Trays, Inc., www.gdit.us). Advantages of this new central-bearing device include: ease of attachment to record bases using conventional light-activated laboratory resin and a unique pivoting central bearing pin for adjustment in all dimensions during the recording process.

This new central-bearing device comes complete with all of the elements necessary to assist in the registration of centric relation in various clinical situations, including dentulism, partial edentulism, full edentulism, small-arch diameter, and large-arch diameter (Figure 7, Figure 8, Figure 9, Figure 10). All components are disposable and setting the device up on record bases or paraocclusal bases is straightforward and time-conservative (Figure 11, Figure 12, Figure 13, Figure 14, Figure 15, Figure 16). The steps required to incorporate the new central bearing device into edentulous record bases are presented in great detail elsewhere (Figure 17, Figure 18, Figure 19, Figure 20).⁴⁸

Conclusion

While today’s complete denture therapy relies heavily on procedures and materials steeped in historic significance, incorporation of modern materials and processes can facilitate predictable and successful outcomes. Clinicians who make complete denture therapy a substantial portion of their daily practice must keep an eye out for procedural modifications that aid in improved patient service. The procedures and materials detailed in the present article have been offered for consideration in modern complete denture therapy.

 

 

 

 

 

 

 

 

 

Complete Dentures

Complete dentures cover your entire jaw, either upper or lower. Some people call them “plates.” Complete dentures rest directly on the gum that covers the bone.

Complete dentures are custom made for you. The process involves multiple appointments, usually about five. The dentist first takes impressions of your mouth. At later visits, you and the dentist select the size, shape and color of the artificial teeth.

Learning to chew food with complete dentures takes patience and practice. You might have to cut your food into smaller pieces than you did when you had your natural teeth.

On occasion, one or more natural teeth are kept when a denture is made. These teeth usually have root canal treatment and are shortened to fit under the denture. This type of denture is known as an overdenture.

Dentists like to maintain a few natural teeth and replace the missing teeth with an overdenture if possible. This has several advantages:

• Your natural teeth help preserve bone.
• Your natural teeth bear some of the chewing pressure. This reduces pressure on other areas of the jaw.
• Your remaining teeth make the denture more stable and less likely to shift in your mouth.
• You feel a better sense of where your jaw is in space and the pressure you are placing on the denture if you have not lost all of your teeth.
• You may find it easier to accept wearing dentures if you have kept some teeth.

Lower dentures tend to be more difficult to keep in your mouth than upper dentures. That’s because the surface area of the lower jaw is much smaller than the top jaw. An upper denture covers the entire palate, which helps it stay in place. Therefore, an overdenture can be most helpful for the lower jaw. However, it is an option for almost anyone who has a few teeth remaining.

Teeth that will be preserved with an overdenture must meet certain standards of health. Canines and premolars are the most common teeth selected because of their root length and position in the jaw.

The teeth will have to be shaped to fit the denture. Shaping may expose the tooth’s living pulp. For this reason, the teeth usually need root canal treatment. This removes the pulp (the nerve of the tooth) and replaces it with filling material.

The teeth that will remain are covered with thin metal castings called copings. They fit into openings in the denture. Attachments also can be put on the copings to help retain the denture in the mouth. On occasion, a natural tooth can be kept in the mouth without a metal coping. If this is done, the dentist will prescribe fluoride drops. These should be used in the overdenture to prevent decay of the tooth.

Overdentures also can fit over implants instead of natural teeth. In fact, implants were first developed to give people “artificial roots” for bridges or dentures in the lower jaw. The denture can fit onto the implants directly, or onto a metal bar between implants.