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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5523_Библиотеки_им_академика_М_И_Перельмана.pdf
Anterior mandible
35
25
(mm)(mm)(mm)(mm)
15
4 • Prosthodontics
Labial
5
117
Posterior mandible
Anterior maxilla
10
20
15
25
5
0
5 10
(mm)
5
(mm)
(mm)
15
010
VIVIIIII VI
Buccal
VIVIIIII VI
VIVIIIII VI
Posterior maxilla
10
0
010
(mm)
Fig. 4.1 A classification system for edentulous jaws. (Reprinted from Cawood JI, Howell RA. Reconstructive preprosthetic surgery I. Anatomical consider-
ations.
Int J Oral Maxillofac Surg.
Close-fitting (0.6 mm spacer) light-cured trays for use
with zinc oxide/eugenol paste can be requested. If extensive
undercuts are present, a spaced tray for alginate or silicone
may be required.
borders. The peripheral border of all trays should finish
2 mm short of the depth of the sulcus recorded by the primary impression, when the spacer is in place. This is an
estimate of the position of the mucogingival line and will
assist the clinician in recording the functional sulcus depth
in the master impression.
1991;20:75–82 with permission from Elsevier.)
Visit 2: Master Impressions
The master impression should record detail of the
denture-bearing area together with the depth and width of
the functional sulcus so that the finished denture maintains
an effective facial or border seal. In some cases, the tray will
require modification to its peripheral border and this
should be carried out using a material of sufficient viscosity
to be mouldable and self-supporting such as medium body
silicone, silicone putty or greenstick compound prior to the
impression being recorded.
VIVIIIII VI
118
Ribbon wax
Master Dentistry
Greenstick may also be used to create functional postdam recording. A layer of greenstick is placed along the
posterior 2–3 mm of the fitting surface aligning with the
vibrating line of the hard soft palate junction. This differentially compresses the tissues in this area. Care is
then taken to remove any excess material extending beyond the vibrating line. An advantage of this thermoplastic material is that it can be modified without the
need to re-take areas which have failed to adequately
capture the functional sulcus, as would be the case with
any of the set elastomers. The final impression is taken
with the material selected, ideally those with hydrophilic
low viscosity properties which will record surface detail.
Low viscosity silicones are often used, but alginate may
also be effective.
These impressions are not to be considered complete
until ribbon wax is placed approximately 2 mm from the
periphery of the impression in order to provide a land area
and protect the width of the sulcus on the resultant master cast. This placement of ribbon wax is called beading
(Fig. 4.2). In the cases where alginate is used, a line must
be drawn with indelible pencil on the facial surface of the
impression 2 mm from the periphery for the same reason.
This area must not be removed!
It is always advisable after pouring the master casts
to retain the individual trays until all treatment has been
completed.
Laboratory Prescription
Casts should be poured in dental stone and a prescription
provided regarding the construction of occlusal rims. The
material to be used for the occlusal rim bases must be
specified. This may be temporary, but sufficiently stable
and robust as to avoid distortion during any of the future
clinical and laboratory stages; for this reason wax only
bases and occlusal rims are best avoided. A temporary
base is discarded before final processing of the denture.
Alternatively, permanent acrylic bases offer the advantage
of allowing a check of the comfort and retention of the
final denture to be assessed at an early stage, as well as
optimising the accuracy of recording jaw relations. Where
problems are identified and new impressions indicated
these are undertaken without involving unnecessary use
of additional clinical time. The disadvantages are additional cost and the small possibility of distortion (about
1%) of the permanent base during a second cure when the
denture is flasked and packed (Fenlon et al, 2008). This
can largely be avoided, however, by use of stone capping
during processing.
Fig. 4.2 Positioning of red ribbon wax for beading to create a land area
on a master model.
Visit 3: Recording Jaw Relations
Before embarking on this stage it is important to refer back
to the treatment plan and to verify with the patient that
what you are doing meets their requirements.
Clinical Procedure
Wax rims should ideally be provided on heat-cured bases, or
failing that an alternative rigid temporary base. If the occlusal rims are constructed on acrylic bases, the fitting
surfaces should be examined for sharp edges and excessive
undercuts. A permanent heat-cured base offers the opportunity to effectively check and modify the retention and
stability of the base, and to determine if a second master
impression is required. If the acrylic resin has been extended into bony undercuts, disclosing wax or pressure relief cream may be used to locate any area requiring adjustment. To minimise any distortion of the wax, the use of a
rigid base is important, as is ensuring it does not become too
warm in the oral environment; removing it regularly and
gentle cooling will assist with this.
The upper record rim is adjusted so that:
n
lip support is correct
n
incisal height is correct
n
occlusal plane is correct (parallel to the lower ridge,
alar-tragus and interpupillary lines)
n
labial and buccal contour is correct (allowing for buccal
corridors to be present)
n
the centre line is marked and lateral check marks to
verify reproducibility of the path of closure.
The presence of dentures in the mouth will modify the
rest position of the mandible. Measurements of the resting
face height should normally be made with the upper rim in
place.
The lower rim should be adjusted to correct the buccolingual contour posteriorly and correct the labial contour
anteriorly. The rim should sit in the neutral zone. It should
be trimmed to establish even, bilateral contact along the
retruded arc of closure (centric relation). In this respect,
the patient should be asked to close until the rims first contact. Excessive pressure may cause them to tilt or be displaced into the alveolar mucosa, giving the appearance of
even contact when, in fact, it does not exist. In some cases,
the patient may be helped to find the retruded arc by asking them to curl the tongue back to contact the posterior
border of the upper occlusal rim. An assessment should be
made of both resting vertical dimension and occlusal vertical dimension. This may be assessed from facial appearance and confirmed from an estimation made using some
kind of measurement from two facial reference points,
commonly using a Willis gauge. This should identify an
adequate interocclusal clearance or freeway space. In an
elderly patient who has been a denture wearer for many
years, often providing slightly more freeway space can be
beneficial.
When satisfied that the patient is consistently occluding
on the retruded arc of closure at the correct vertical dimension of occlusion, make locating marks in the midline and
buccally in the canine region. Remove the rims and place
them together outside the mouth using the locating marks.
The jaw relation is now ready to be recorded: locating
4 • Prosthodontics
119
indices are cut into the occlusal rims to aid rearticulating
once the record blocks are removed from the mouth.
The rims are placed in the mouth and a thin layer of
silicone jaw registration material or a similar recording
material is applied along the entirety of the lower rim. Stabilise the rims with fingers and encourage the patient to
close into retruded jaw relation (check locating marks are
coincident) and wait until the material has set. After removing rims from the mouth, check that casts can be
placed into the rims without any premature contacts distally, either between the heels of the casts or between the
posterior extensions of the denture bases (avoidance of
heel clash). Also ensure that the rims can be separated and
relocated accurately.
Select teeth that are an appropriate shade and mould for
the patient. Reference may be made to previous dentures if
the patient was happy with their appearance.
If a functional impression of the posterior extension of
the upper denture has not been used, a post dam is cut into
the master cast prior to final processing. If the patient has
consistently had problems with complete dentures or had a
gross skeletal abnormality, it may be worth considering using a face-bow registration of the upper rim to allow for a
more reliable location of the cast on the articulator in the
laboratory, although there is little evidence to show this is
of benefit. Use of permanent bases to optimise stability and
retention of the record blocks should also be considered.
Laboratory Prescription
Record the shade, mould and material to be used for the artificial teeth on the laboratory card. Indicate the type of articulator (average movement or semi-adjustable) on which the
dentures are to be set up and indicate any aspects of the anterior tooth setup that are to be copied in the trial dentures.
Indicate the type of bases required for the trial dentures. All
casts should be mounted using a split-cast technique.
Visit 4: Trial Dentures
An examination of the completed setup on the articulator
should be carried out before trying in the mouth, and any
discrepancies noted. If the trial dentures are not correct on
the articulator, this must be evaluated before a decision to
proceed to place these trial dentures in the patient’s mouth.
If some technical or occlusal fault is evident a decision
about how to effectively rectify this is required.
In the mouth, carry out a complete assessment of the
trial dentures including the following:
n
Stability and retention, more difficult to assess when using temporary bases. When using a permanent base this
should verify that the retention and stability are consistent with your finding during recoding of jaw relations.
n
Peripheral extension.
n
Positioning of teeth in relation to neutral zone and shape
of polished surfaces.
n
Occlusion should be assessed visually (articulating paper
is not necessary at this stage, but care must be taken to
stabilise the bases on their respective supporting tissues).
Occlusal interferences may displace denture bases away
from the tissues disguising occlusal errors.
n
Verify with the patient that the contact feels even and
simultaneous.
n
Interocclusal clearance to give a satisfactory freeway
space. Speech sounds and mouth feel give clues as to the
appropriateness of this.
n
Appearance including the shade, mould and position of
the anterior teeth and the contour of the labial flanges;
check that the appearance is natural (a completely even
arrangement of teeth usually looks unnatural), and modify if necessary.
n
Recheck occlusion if the positions of the anterior teeth
have been modified as this may result in occlusal interference.
After carrying out any necessary corrections, obtain the
patient’s comments. Do not proceed to finish unless the patient
is satisfied, especially with the appearance (record this in the
notes).
Anything other than minor localised discrepancies of
occlusion and vertical dimension will require a new jaw
registration using the trial denture as an occlusal rim. A
decision about what has caused the error will determine
which teeth will need to be removed and replaced with
wax, before once more sealing them together using occlusal registration paste prior to rearticulating the casts and
resetting the teeth.
The dentures would then proceed to being reset and tried
in again at the next visit. It is important to have an approach which uses the ‘try in’ stage as an opportunity to
confirm that all of the planned treatment objectives have
either been achieved or that those which conflict with other
objectives have been agreed and discussed with the patient.
Any such discussion should highlight that compromises
have been agreed between both clinician and patient.
Final Laboratory Prescription
The prescription should state definitely whether dentures
can be finished or if a further trial is required. If the jaw
relationship has been re-recorded, the casts are remounted
on the articulator and a second trial stage is carried out.
When the dentures are processed, use of the split-cast technique will minimise occlusal errors during processing.
Porosity
One of the possible faults that can occur in the laboratory is
porosity within the acrylic resin or tooth movement during
the processing cycle.
Contraction porosity results when insufficient acrylic
dough has been placed to create an excess or flash. Alternatively, the application of insufficient pressure during curing
can lead to porosity voids dispersed throughout the whole
mass of the denture base.
Gaseous porosity results when the temperature of the
dough is raised significantly above the boiling point of the
monomer (100 degrees Celsius), producing spherical voids
in the hottest part of the curing dough. This occurs most
commonly in the lingual flanges of a lower denture.
Granular porosity results from evaporation of the monomer during preparation. Proportioning of the powder to
liquid ratio is dependent on allowing each powder particle
to become wetted by the monomer. The mixture is left to
stand until it reaches the right consistency suitable for
packing into the gypsum mould. During this standing period, a lid should be placed on the mixing vessel to prevent
120
Master Dentistry
evaporation of the monomer. Loss of monomer during this
stage can produce granular porosity in the set material,
which is characterised by a blotchy opaque surface.
Visit 5: Final Dentures
The processed dentures should be checked for any sharp
edges, acrylic ‘pearls’ or excessive undercuts on the fitting
surface. Insert each denture separately and check on fit and
comfort to the patient. An examination of the occlusion in
the mouth can be done either visually or using articulating
paper.
Visual assessment is made by observing and by asking
the patient if the teeth are meeting with equal pressure on
both sides of the mouth when the mouth is closed gently.
Articulating paper is used to confirm these findings and
to precisely locate any premature contacts. A heavy mark
made by the paper may indicate where the initial contact is
being made. Fossa rather than cusp tips should be ground
at this stage only. Beware of artefacts, such as those produced by tilting of the dentures. This would produce marks
from the articulating paper on both sides of the mouth,
whereas initial observations may have indicated that the
first occlusal contact is only on one side.
If any occlusal faults are diagnosed, it is liable to be a
clinical and not a laboratory error providing that the splitcast technique has been used. Relatively minor occlusal
discrepancies may be adjusted at the chair side until:
n
the occlusal pressure on both sides of the mouth is the same
n
the occlusal contacts indicated by articulating paper are
primarily on the premolar and first molar teeth; heavy
contacts distally or anteriorly should be avoided as these
may cause tipping of the dentures
n
lateral and protrusive movement is possible without cuspal interference causing displacement of the dentures.
Significant chair-side occlusal adjustments are particularly difficult; where there is any doubt, a check record
should be obtained. This often saves time if a large occlusal
error is found at the initial insertion stage.
Check Record
A check record is advisable for the correction of occlusal errors that are too large to adjust easily at the chair side. This
technique is also more reliable and accurate than major
adjustment made at the chair side using articulating paper.
Narrowed wax wafers, constructed from one thickness of
pink modelling wax, are sealed to the occlusal surfaces of
the lower posterior teeth and adjusted so that the patient
occludes evenly on the wafers in retruded jaw relation with
the teeth separated by a distance less than the freeway space.
The teeth should not penetrate through the wax; otherwise
tooth contact may cause displacement of the dentures and/
or the mandible. This occlusal registration may be refined
using registration paste. The dentures are then remounted
on an articulator.
The articulator is closed with the incisal pin removed,
and the occlusal contacts are checked visually and with
articulating paper. Adjustments are carried out until an
even occlusion is obtained. The dentures are reinserted and
the occlusion checked in the mouth.
evidence base for this clinical approach to complete denture
construction. As with lots of areas of clinical dentistry,
there is little evidence to support clinical approaches recommended; however, the following does suggest that master impressions may not be required to provide the same
degree of patient satisfaction.
simple complete denture techniques can provide patient
satisfaction. When complete dentures are required, are
simplified techniques as effective as complex traditional
ones for their manufacture? A randomised controlled trial
(RCT) was carried out in a hospital environment by Kawai
et al (2005). A total of 122 edentulous individuals, aged
45–75 years, were randomly allocated into groups to receive dentures made using either traditional or simplified
techniques. Individuals allocated to the traditional arm had
a final impression taken in a custom-made tray and a facebow recording and a semi-adjustable articulator were used,
with articulator remount after delivery. Those in the simplified technique group had impressions taken in stock trays
and no face-bow recording and a monoplane articulator
were used, with no articulator remount after delivery. There
were no significant differences between the two groups in
patient ratings for overall satisfaction at 3 or 6 months.
These results suggest the use of simplified techniques,
which are easier to master and which should reduce treatment costs.
critical review of some dogmas in prosthodontics
(carlsson 2009)
n
A scrutiny of the prosthodontic literature indicates that
many common clinical procedures lack scientific support. In the era of evidence-based dentistry, ineffective
interventions should be eliminated and decisions should
be made on best available evidence.
n
Studies have demonstrated that dentists’ and patients’
interpersonal appraisals of each other were most significant factors, accounting for patients’ evaluation of treatment outcome.
n
Reviews of the literature on this topic have suggested
that the creation of a good relationship with the patient
seems to be more important than a technically perfect
denture construction for achieving patient satisfaction.
ADVICE TO PATIENTS
Instructions in respect of new dentures should be discussed
with your patient after the final dentures have been inserted, preferably using a printed leaflet. In particular, the
importance of good denture hygiene should be emphasised.
If an immersion cleaner is recommended, a hypochlorite
type is the most suitable. Any mechanical cleaning should
be done with a brush that allows access and has good
adaptability to all surfaces of the denture.
If the patient has to leave the new dentures out because
of pain or soreness, request that the dentures be worn for
24 hours before the review appointment, in order that the
cause of the discomfort may be more readily detected. Under no circumstances should the patient attempt adjustment of the dentures.
Denture Maintenance
Unfortunately, evidence-based guidelines for the care and
maintenance of removable complete denture prostheses do
4 • Prosthodontics
121
not exist. Based on the best available evidence, the following
are guidelines for the care and maintenance of dentures
(Felton et al 2011):
1. Careful daily removal of the bacterial biofilm present in
the oral cavity and on complete dentures is of paramount importance to minimise denture stomatitis and
to help contribute to good oral and general health.
2. To reduce levels of biofilm and potentially harmful
bacteria and fungi, patients who wear dentures should
do the following:
a. Dentures should be cleaned daily by soaking and
brushing with an effective, non-abrasive denture
cleanser.
b. Denture cleansers should ONLY be used to clean
dentures outside of the mouth.
c. Dentures should always be thoroughly rinsed after
soaking and brushing with denture-cleansing solutions prior to reinsertion into the oral cavity. Always
follow the product usage instructions.
3. Although the evidence is weak, dentures should be
cleaned annually by a dentist or dental professional by
using ultrasonic cleansers to minimise biofilm accumulation over time.
4. Dentures should never be placed in boiling water.
5. Dentures should not be soaked in sodium hypochlorite
bleach, or in products containing sodium hypochlorite,
for periods that exceed 10 minutes. Placement of dentures in sodium hypochlorite solutions for periods longer than 10 minutes may damage dentures.
6. Dentures should be stored and immersed in water after
cleaning, when not replaced in the oral cavity, to avoid
warping.
7. Denture adhesives, when properly used, can improve
the retention and stability of dentures and help seal
out the accumulation of food particles beneath the
8. In a quality-of-life study, patient ratings showed that
denture adhesives may improve the denture wearer’s
perceptions of retention, stability and quality of life;
however, there is insufficient evidence that adhesives
improve masticatory function.
9. Evidence regarding the effects of denture adhesives
on the oral tissues when used for periods longer than
6 months is lacking. Thus, extended use of denture
adhesives should not be considered without periodic
assessment of denture quality and health of the supporting tissues by a dentist, prosthodontist or dental
professional.
10. Improper use of zinc-containing denture adhesives
may have adverse systemic effects. Therefore, as a precautionary measure, zinc-containing denture adhesives should be avoided.
11. Denture adhesives should be used only in sufficient
quantities on each denture to provide sufficient added
retention and stability to the prostheses.
12. Denture adhesives should be completely removed from
the prosthesis and the oral cavity on a daily basis.
13. If increasing amounts of adhesives are required to
achieve the same level of denture retention, the patient
should see a dentist or dental professional to evaluate
the fit and stability of the dentures.
14. While existing studies provide conflicting results, it is
not recommended that dentures be worn continuously
(24 hours per day) in an effort to reduce or minimise
denture stomatitis.
15. Patients who wear dentures should be checked annually by the dentist, prosthodontist or dental professional for maintenance of optimum denture fit and
function, for evaluation for oral lesions and bone loss
and for assessment of oral health status.
COMMON COMPLAINTS OF THE EDENTULOUS PATIENT
Most prosthetic complaints can be prevented or minimised by
adequate diagnosis, treatment planning and treatment plus
attention to detail during the construction phase. A preprosthetic radiographic investigation can prevent the finding
of retained roots, unerupted teeth and bone pathology after
the new dentures have been constructed; however, this
should not be done as a matter of course. Pretreatment case
history and clinical investigation with a detailed assessment
of any existing dentures should aid the resolution of such
problems as correct face height, tooth position and polished
contour. However, problems and complaints will still occur
with new dentures. Table 4.2 lists some of the more common
complaints, their probable causes and suggested treatment.
RELINES OR REBASES
A reline involves the addition of a material to the fitting
surface of a denture base. A rebase involves the removal
and replacement of virtually all the denture base, namely
the fitting and polished surface of the denture. There are
always risks with both relining and rebasing that the resultant denture may be made worse. There are few indications
these days for a full rebase as it is often more satisfactory to
consider a copy technique of the denture that would have
been rebased. This will not necessitate the removal of the
denture from the patient.
Advantages of a Reline
n
Can be done at the chair side or in the laboratory
n
Can be permanent or temporary
n
Will improve the retention of an ill-fitting denture
n
A resilient lining can be added to a previous denture base
Advantages of a Rebase
n
Will not increase the thickness of the palate
n
Will remove the majority of the previous denture base if,
for example, bleaching has occurred
4.2 Copy/Duplicate Dentures
LEARNING OBJECTIVES
You should:
• understand the indications and advantages of a copy/
duplicate denture technique over a more conventional
approach to complete denture construction
• appreciate the clinical and technical stages involved in
such a technique.
122
Master Dentistry
Table 4.2 Common Complaints of Patients With Dentures.
Complaint Probable Cause Treatment
Generalised discomfort over
the denture-bearing areas
Lack of chewing pressure,
‘collapsed face’, generalised
facial discomfort
Angular cheilitis Lack of facial support (rarely occlusal face height). Maceration
Pain over crest of ridge (especially lower anterior region)
Localised pain Irregular soft tissue following socketed immediate dentures Relieve/reline. Consider pre-prosthetic surgery
Pain in sulcus
Ulcer Overextension Relieve
Denture-induced hyperplasia Overextension Severe relief; may not resolve, then surgery
Localised pain in lower
premolar region
Pain on one side Premature contact, poor articulation Analyse occlusion (check record) and articula-
Pain from cheek and tongue Teeth not set in neutral zone; especially if no horizontal
Denture displaces on opening
or in speech
Upper denture Inadequate post dam Trace and reprocess or cold cure
Lower denture Incorrect shape of polished surfaces Recontour
Speech defect New F/F Encouragement and perseverance
Poor mastication Worn teeth increase in freeway space Correct OVD-remake
Dry mouth Systemic factors and medication Salivary substitute
General inability to
accommodate
Increased occlusal face height Occlusal adjustment or, more commonly, remake
Occlusal interference in lateral and protrusive movements Balanced articulation with free sliding contact
Movement of denture bases over basal tissues Reline/remake using copy technique
Incorrect anteroposterior relationship of dentures (i.e.
non-coincidence of tooth and muscular positions)
Increased free monomer Remake with correct curing cycle
Decreased occlusal face height Use cold-cure acrylic (occlusal pivots) or splint
of cutaneous tissues by repeated wetting of angular folds
This may lead to superinfection with
Irregular bony contour following abnormal healing pattern X-ray for diagnostic and treatment planning,
Irregularities on fitting surface Adjustment
Premature contact Occlusal adjustment
Buried roots, unerupted teeth, cysts, etc. X-ray, surgery
Excess undercut utilised Partial blocking out of undercut. Localised use
Pressure on superficial mental nerve Relieve denture, surgery: repositioning only to
overlap
Overextension of border Reduce border, develop new border and re-
Underextension of border Develop new border and replace in acrylic resin
Anterior teeth too far forward of ridge Reposition anterior teeth, F/F will probably
Excessively deep post dam Remove excess and polish post-dam area
Interference of coronoid process on opening Reduce thickness of flange
Bulky flange Reduce thickness of flange
Excessive thickness of flange in region of modiolus Reduce
Posterior teeth outside neutral zone Reduce width of teeth or remake
Insufficient room for tongue Increase/remake
Lack of freeway space Correct OVD-remake
Adaptive capacity: age, oral dryness, high oral awareness Meticulous attention to detail and encouragement
Errors in occlusal vertical dimension Correct errors in OVD
Psychological factors
Change in denture shape Consider copy technique
Staphylococcus aureus
Occlusal adjustment
to build up occlusal face height then remake
one or both dentures
Build up canine prominence or move anterior
teeth forward; use antifungal cream; increase
denture hygiene
osteoplastic surgery
of soft lining material
be used in exceptional cases
Resilient lining
Viability of implant supported denture
tion, then adjust
Reduce width of teeth and provide horizontal
overlap
place in acrylic resin
have to be remade
Reduce thickness of denture to provide more
tongue space
Speech analysis and adjustment
Table 4.2 Common Complaints of Patients With Dentures.—cont’d
Complaint Probable Cause Treatment
Nausea Denture extended onto soft palate Reduce
Lack of retention Correct
Reduced tongue space Recontour polished surface
Inability to accept such a large amount of acrylic Horseshoe design for upper
‘Teeth meet too soon’, ‘can’t
open mouth far enough for
food’
Appearance Insufficient attention at try-in Correct
Denture stomatitis Ill-fitting denture Reline/remake
Midline fracture Ill-fitting dentures Reline/remake
OVD
, Occlusal vertical dimension.
Increased occlusal face height Reduce or remake F/F
Unwillingness of patient to put function before aesthetics Attempt to reach understanding
Fungal infection Denture hygiene; antifungal cream
Increased free monomer Remake: correct curing cycle
Teeth set excessively off the ridge Remake
F/– against lower standing teeth Metal palate/sufficient overjet
Fatigue Rebase
4 • Prosthodontics
123
The process of history taking and examination of the patient and their existing dentures presents valuable information about the patients’ previous denture-wearing success.
Recognising the limitations of an existing denture whilst
noting any successful aspects may inform the choice of a
conventional technique of denture construction, which incorporates some of the beneficial features of the existing
denture. Patients who have worn dentures satisfactorily
over a long period of time and have developed a neuromuscular feedback in relationship to the spatial relationship of
the denture to the surrounding tissues may benefit from a
copy denture technique. In this respect, however, it is important to realise that the copy denture does not simply replicate the current dentures worn by the patient. It is designed
specifically to reproduce the favourable aspects of the current prosthesis such as tooth position and polished surfaces,
while improving the adaptation and occlusion. Copy dentures are particularly useful for elderly patients with good
denture-wearing experience. There are numerous ways to
reproduce beneficial features of existing dentures incorporating both conventional remake and copy techniques.
These range from the use of impressions to create models of
anterior tooth setup, shape and size of teeth, to using an
Alma gauge to measure the incisal height and labial position
of anterior teeth to reproduce lip support and aesthetics.
INDICATIONS
There are a number of situations where copy dentures are
advisable:
n
Correct position of teeth in the neutral zone or correct
zone of adaptation and the polished surfaces are satisfactory
n
Loss of retention in otherwise favourable dentures requiring replacement
n
Wear of the occlusal surfaces
n
Replacement of immediate dentures
n
Spare set of dentures. This might be a consideration for
patients who live in care homes and who have cognitive
impairment.
Typical dental history that would suggest an indication
for copy dentures:
n
Elderly patients presenting with satisfactory complete
dentures
n
Worn occlusal surfaces, indicating long-term acceptability without significant loss of occlusal vertical dimension and change in the horizontal jaw relationship
n
Deterioration of denture base materials
n
Patient requests ‘spare set’ of dentures
n
Patients with a history of denture problems make controlled
modifications to copy previously most successful dentures.
Clinical Advantages
n
No alteration or mutilation of existing dentures
n
No period for the patient without their dentures (as compared to a reline or rebase)
n
Three clinical stages
n
Simple duplication procedure, less time than conventional impressions
Technical Advantages
n
No individual trays or record blocks required
n
Infrequent rearticulation of teeth for try-in necessary
n
Elimination of repolishing after border adjustments
n
No thickening of palate in the finished denture, as occurs in some reline procedures
ALGINATE COPY BOX/SILICONE COPY TECHNIQUE
First Clinical Stage
Any modifications are made at the first clinical stage
(Box 4.1).
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Master Dentistry
Box 4.1 Technique for Copying Existing Denture.
1. Correct any under- or overextension using greenstick or acrylic
border moulding material.
2. Add labial flange (if required) to open face denture using
impression compound.
3. Use a wax wafer to provide desired occlusal face height and
decide whether increase to be on F/ alone or /F alone or
shared between the two.
4. Choose shade.
5. Copy denture utilising alginate and copy boxes (Fig. 4.3).
6. Send copy boxes to laboratory with prescription.
Laboratory Stage
Wax-acrylic replicas are poured by adding wax into the
mould to 1 mm past the gingival margins of the teeth and
allowed to set. The base of the wax is then scored and selfcured acrylic is poured into the closed mould through previously cut sprue holes and allowed to polymerise. A stone
duplicate is cast into the mould once the wax and acrylic
copy has been removed. This stone mould can be used for
comparison of the copy try-in. The denture templates are
then removed from the moulds and articulated using the
wax wafer provided. The wax teeth are then removed and
replaced by acrylic denture teeth of appropriate shade and
mould. This will provide trial dentures for the second clinical stage. Grooves are cut in the palate and filled in with
wax (Fig. 4.4) to allow removal of the palate at a later stage.
Second Clinical Stage
At the second clinical stage, the trial dentures are assessed by
the clinician and the patient and any errors in occlusion or
tooth position are corrected, necessitating a retry. When the
trial dentures are satisfactory, they should be prepared for
impression taking. This involves removing any undercuts,
reduction of the peripheral border and modification using
greenstick or a border-moulding self-cured acrylic resin. The
polished surfaces of the replica are coated with yellow petroleum jelly. Wash impressions are recorded using zinc oxide/
eugenol or low-viscosity elastomer (if hard tissue undercuts
are present in the mouth) using the closed-mouth technique.
Occlusal relationships should be maintained. The position,
width and depth of the required post dam are determined.
A
B
C
Fig. 4.3 Denture copied by insertion in a copy box. (A) Coating the polished surface with alginate to avoid air inclusion. (B) Seating the denture to be
copied, aligning it with the sprue holes and ensuring slow seating to exclude air. (C) Excess alginate extruded above the level of the flange periphery
should be trimmed back.
4 • Prosthodontics
4.3 Immediate Replacement Dentures
LEARNING OBJECTIVES
You should:
• understand the concept of immediate replacement
dentures
• comprehend the clinical stages involved in immediate
denture construction.
125
Fig. 4.4 Grooves cut in the palate to allow its removal later.
Final Laboratory Stage
The functional borders are preserved and stone casts are
poured. The acrylic palate is removed and an even-thickness palate is waxed up.
Third Clinical Stage
The new dentures are checked for fit, extension and occlusion. A subsequent review is arranged.
COMMON PROBLEMS
The dentist may have several problems:
n
Unfamiliarity with technique leading to failure to use
closed-mouth technique with light and even occlusal
contact
n
Attempting a copy denture technique in a patient for
whom it is clearly not indicated
n
Copy flasks; some flasks are costly, but if they are used
frequently and repeatedly the cost is minimal
n
Forgetting to take the shade
n
Finding a laboratory that is comfortable with the technique, fees additional to conventional complete denture
construction charged by the laboratory
n
Inadequate information on the prescription.
Similarly, certain problems are encountered by techni-
cians:
n
Duplicating the dentures; many laboratories duplicate
the denture completely in wax or self-cured acrylic.
Wax will distort especially at the stage of closed-mouth
impressions
n
Articulating the copy
n
Setting up, copying the previous arrangement
n
Waxing up
n
Finishing, removing the palate and replacing a wax
palate
n
Grinding of denture teeth to fit acrylic base
n
Registration problems
n
Fees in comparison to the laboratory fee and the time
taken to provide treatment.
There is no published evidence base available comparing
conventional techniques to this approach to suggest that a
copy/duplicate denture technique is superior.
An immediate denture is defined as a denture that is made
prior to the extraction of the natural teeth and which is
inserted into the mouth immediately after the extraction of
those teeth. It may involve total or partial replacement.
Generally it is unacceptable to patients that they should be
rendered edentulous without replacement of teeth for functional and aesthetic reasons. As overall dental health has
generally improved, the total removal of teeth followed by
the provision of complete dentures has become less common. It is now more usual to provide simple immediate additions to existing dentures or to provide an immediate
partial denture which then transitions gradual tooth loss
with future additions. A transitional denture may therefore
be considered one which is designed as a partial denture, to
which teeth of doubtful prognosis might be added, as they
fail; the ultimate prognosis is for complete tooth loss within
that arch.
Over the last 10 years we have seen a shift in the delivery
of removable immediate dentures to immediate loaded
implant-retained prostheses, in situations where good primary stability of implants has been achieved. These are
generally a fixed alternative to the traditional removable
immediate denture. However, whilst this represents a treatment option which may be beyond the affordability of
many patients, it nevertheless offers significant advantages
in terms of psychosocial adaptation, quality of life, bone
preservation and functionality. Treatment planning for
tooth loss, final restoration, long-term maintenance and
optimisation of implant placement requires specialised clinical skills beyond the scope of this chapter.
ADVANTAGES OF IMMEDIATE DENTURES
There are several advantages for the patient:
n
Maintenance of the soft tissue contour of the face:
n
dentures will support the soft tissues around the face
in their correct position once teeth are lost and
thereby prevent collapse of facial tissues
n
Maintenance of mental and physical wellbeing:
n
the patient is not seen to be edentulous; this is important for business, domestic and social purposes
n
aesthetics are maintained by placing the artificial
teeth in a position similar to natural teeth or improved
by changing the position.
n
The advantage of a more seamless adaptation to dentures is aided by:
n
maintenance of tooth position
n
maintenance of muscle balance
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Master Dentistry
n
prevention of the formation of abnormal mandibular
movements
n
aiding chewing and mastication.
n
Patients are likely to adapt to immediate dentures rather
than waiting several months until healing and postextraction resorption is complete. Subsequently a copy
denture technique may then be utilised to reproduce
successful design features and maintain some continuity, where desirable, to the patients’ original dentition.
There are also advantages for the dentist:
n
The use of existing dentition to reproduce occlusal relationship: teeth may act as occlusal stops, which will
provide the intercuspal position and the correct occlusal
vertical dimension.
n
Aesthetic consideration: shape and size of the teeth are
known, which will assist selection (this may prove to be
a problem rather than an advantage if teeth have drifted
owing to periodontal disease).
n
Haemorrhage control.
DISADVANTAGES OF IMMEDIATE DENTURES
Immediate dentures do have a number of disadvantages:
n
Good cooperation is required, with the need for several
follow-up appointments. Aftercare may require many
visits including relines/rebases/new dentures.
n
As alveolar bone resorption occurs rapidly, there is loss
of tissue adaptation and retention.
n
Increased cost: the provision of relines and further denture provision makes the treatment costly.
n
A trial denture stage is not always possible: this is a big
disadvantage as it is not possible to show the patient
what the teeth will eventually look like.
n
Gross irregularities of teeth make processing difficult
(e.g. class II division 2, bulbous tuberosities/tori).
n
Surgical challenges may present difficulties Special care
for infective endocarditis/diabetes/coronary heart disease/risk of medication related osteonecrosis of the jaws.
Types of Immediate Denture
Immediate dentures can be flanged or socket fit.
Flanged dentures:
n
are retentive
n
are easier to reline and rebase
n
may be difficult to place where there is an undercut –
use of partial flange.
Socket-fit dentures:
n
are contraindicated in mandible
n
the necks of the teeth sit into extraction sockets and
are aesthetically good initially
n
are prone to loss of aesthetics as resorption progresses
n
are difficult to reline/rebase or to add flange
n
have poorer retention
n
are technically easier to provide, though unless
strongly indicated are suboptimal.
Diagnosis
The decision to render a patient edentulous should not be
undertaken lightly, and a clear understandable discussion
about the risks and benefits of treatment and alternatives
should be entered into. A record of the patients’ decisions to
accede to being rendered edentulous should be noted. The
difficulties involved with immediate denture provision must
be explained to patients. The patient needs:
n
clear explanation of the technique
n
visits to be planned
n
the staging of planned extractions
n
appropriate cooperation.
The health of the oral and facial tissues must be assessed:
n
Soft tissues: basic periodontal evaluation, probing depths
give an indication of the initial collapse/retraction of soft
tissues; pre-extraction scaling and polishing
n
Hard tissues: edentulous areas, charting of teeth, use of
appropriate justified radiographic images.
Treatment Planning
For a one-tooth immediate denture when no denture is
present:
1. Preliminary and/or master impressions, usually in alginate. Impression of opposing arch and suitable interocclusal record
2. Select shape and shade of tooth
3. Extraction of tooth/teeth and delivery of dentures.
For a one-tooth addition to an existing denture:
1. Impression of mouth with denture in situ. Impression of
opposing arch and suitable interocclusal record
2. Addition of denture tooth/teeth as soon as possible
3. Extraction of tooth/teeth and delivery of denture.
For multiple-teeth immediate denture, one of the three
options is possible:
1. Extract all the teeth at one time and insert immediate
dentures.
or:
2. Extract posterior teeth prior to making immediate dentures to replace anterior teeth.
or:
3. Post-immediate dentures – difficulties can arise because
of ongoing resorption of ridges during denture construction.
Clinical Stages
The clinical stages are the following:
1. Preliminary impressions in alginate with or without
impression compound
2. Master impressions in alginate
3. Occlusal record rims for existing edentulous areas
4. Trial stage
5. Delivery of dentures and extraction of teeth
6. Review appointments.
Laboratory Stage
Trimming of casts occurs between try-in and before processing of dentures. The cast should ideally be prepared by
the dental surgeon as they alone have seen the patient and
undertaken the clinical examination. The cast is marked
with a pencil to show the gingival margin, the long axis of
the teeth and the length of the teeth. The teeth are removed