Mouth preparation

Mouth preparation
10/21/2019 Dr.Sherif sultan,BDS,MSc,PhD,Fixed prosthodontics 1

Definition
• Mouth preparation refers to procedures that must be
accomplished before fixed prosthodontic treatment can be
properly undertaken.
• Planning a logical treatment sequence should precede any
fixed prosthodontic intervention.
• Mouth preparation is normally multidisciplinary: It
incorporates oral surgery; operative dentistry; and
endodontic, periodontic, orthodontic, or occlusal therapies,
or a combination of these.
• Mouth preparation is particularly important for fixed
prosthodontics, which, like all dental disciplines, is
facilitated and enhanced by meticulous preparatory
treatment.
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Dr.Sherif sultan,BDS,MSc,PhD,Fixed
prosthodontics
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Typical treatment sequence
• The following list describes a typical sequence in the
treatment of a patient with extensive dental disease,
including missing teeth, retained roots, caries, and
defective restorations:
• Preliminary assessment .
• Emergency treatment of presenting symptoms.
• Oral surgery .
• Caries control and replacement of existing restorations
• Endodontic treatment
• Definitive periodontal treatment
• Orthodontic treatment
• Definitive occlusal treatment
• Fixed prosthodontics
• Removable prosthodontics
• Follow-up care
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• However, the sequence of preparatory treatment
should be flexible. Two or more of these phases
are often performed concurrently.
• For example, If caries control results in a pulpal
exposure or exacerbates an existing chronic
pulpitis, endodontic treatment may be needed
earlier than anticipated.
• When the primary symptoms have been
eliminated, the occlusal needs of the patient are
carefully evaluated through clinical examination
and the study of centric relation articulated
diagnostic casts.
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ORAL SURGERY
• Soft Tissue Procedures
• Alteration of muscle attachments
• Removal of a wedge of soft tissue distal to the
molars to enable access during tooth
preparation
• Modification of the shape of edentulous
spaces.
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Hard Tissue Procedures
• Tooth extraction is the most common surgical
procedure involving hard tissue.
• Removal of Buccal torus that may interfere
with oral hygiene
• Impacted or unerupted supernumerary teeth
often should be removed to avoid damage to
adjacent structures.
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Implant-Supported Fixed Prostheses
A team approach to treatment is strongly recommended, with
close cooperation between the specialists
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CARIES AND EXISTING RESTORATIONS
• In general, when a crown is needed, the dentist
should plan to replace any existing restorations.
This is because,
• Studies have shown that accurately detecting
caries beneath a restoration without its complete
removal is difficult.
• Crowns and fixed dental prostheses are definitive
restorations. They are time-consuming and
expensive treatment options and should not be
recommended unless the restoration will last a
long time.
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• Although most teeth in need of crowns require
foundation restorations, small defects resulting
from less extensive lesions can often be
incorporated in the design of a cast restoration
or can be blocked out with cement. The latter is
recommended on axial walls where an
undercut would otherwise result. If a small
defect is present on the occlusal surface,
however, it may be better to incorporate it into
the definitive restoration than to block it out.
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FOUNDATION RESTORATIONS
• A foundation restoration, or core, is used to build a
damaged tooth to ideal anatomic form before the
tooth is prepared for a crown.
• Foundations may have to serve for an extended time
before fabrication of the definitive prosthesis and
should provide the patient with adequate function.
• They should be contoured and finished to facilitate oral
hygiene. Subsequent tooth preparation is greatly
simplified if the tooth is built up to ideal contour.
• It can then be prepared as if the tooth were intact.
Depth grooves can be used to enable precise
evaluation of occlusal and axial reduction.
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Composite resin core
• It should be used when ever possible in all cases
provided that good technique is performed.
• Many dentists prefer to use a special colored
core material rather than conventional tooth-
colored composite resin as a foundation
because it allows them to more easily discern
the composite-tooth junction.
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DEFINITIVE PERIODONTAL TREATMENT
Unless a patient’s existing
periodontal disease has been
properly diagnosed and treated,
fixed prosthodontic
treatment will fail.
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Keratinized Gingival Tissue
• For a tooth or implant to be treated with a
restoration extending into the gingival
sulcus(subgingival margin), approximately 5
mm of keratinized gingiva, at least 3 mm of
which is attached gingiva, is recommended.
Where less keratinized gingiva is present, or in
areas of localized gingival recession, a grafting
or other gingival augmentation procedure
should be considered.
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A minimum of 3 mm of attached keratinized
tissue must be present when a restorative margin is placed
subgingivally. On the facial aspect of the maxillary left anterior
teeth, the sulcus depth is 2 mm. Therefore, 5 mm of keratinized
tissue must be present
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The laterally positioned pedicle graft
• Is used for an area
of recession or lack
of attached gingiva
on a single tooth
when amounts of
keratinized gingiva
in adjacent teeth or
edentulous spaces
are adequate.
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A coronally positioned (advanced)
pedicle graft
• is used when a single
tooth or multiple teeth
exhibit gingival recession.
If the width of the
attached keratinized
gingiva is inadequate, a
free gingival graft may be
placed to increase it
before the coronal
positioning
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The connective tissue graft
• The most common gingival augmentation
technique
• This technique involves the use of a subepithelial
connective tissue graft harvested from the palate
in a split thickness manner, which allows the
wound to be closed after removal of the graft.
• Connective tissue grafts can be utilized to cover
exposed roots, to augment deficient ridges, and
to attempt to rebuild papillas
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Crown-Lengthening Procedures

• when the clinical crown is too short to provide
adequate retention without the restoration
impinging on the normal soft tissue attachment
(biologic width)
• Improve appearance of multiple short teeth.
• extensive subgingival caries, a subgingival
fracture, or root perforation
• Surgical crown lengthening increases the crown-
to-root ratio and results in a loss of gingiva and
bone from adjacent teeth.
• may be accomplished either surgically or with
combined orthodontic-periodontic techniques,
depending on the patient and the dental
situation.
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Surgical Crown Lengthening
• gingivectomy or removal of gingiva by
electrosurgery alone, although osseous
recontouring is most often needed to prevent
encroachment of the prosthesis on the biologic
width.
• a full-thickness mucoperiosteal flap is reflected,
and the osseous resection creates 3.5 to 4.0 mm
of space between the gingival crest and the
margin of the existing restoration or carious
lesion.
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The following factors should be considered:
• 1. Esthetics. When surgical crown lengthening is indicated, it may
be difficult to achieve a harmonious transition from the tissue
around the lengthened tooth to that around adjacent teeth.
Alternatives include orthodontic extrusion or removal and
replacement with a prosthesis. If surgery is undertaken, most of the
osseous reduction should be on the lingual or palatal side, where
there is usually no esthetic problem, with blending on the labial or
buccal side only as necessary.
• 2. Root length within bone. If osseous support is limited, it may be
better to remove the tooth and replace it with a prosthesis than to
have the patient undergo surgery on a tooth with a doubtful
prognosis.
• Restoration of a tooth that has undergone surgical crown
lengthening is commonly initiated 4 to 6 weeks after the surgical
procedure.
• it is advisable to provisionally restore the tooth in question, either
before or immediately after surgical crown lengthening, and
subsequently fabricate the definitive restoration after 3 months.
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Maintenance and Reconstruction
of the Interdental Papilla
• The presence or absence of the interproximal papilla,
especially in the maxillary anterior area, is of concern to
the restorative dentist, the periodontist, and the patient.
• The reconstruction of a papilla is dependent on multiple
factors, such as the amount of attachment loss in the area,
the blood supply available for the newly created papilla,
and the distance from the contact area to the crest of the
interproximal bone.
• The majority of the techniques used for reconstruction of
the interdental papilla are both surgical and restorative,
and they therefore involve careful coordination and
planning of the surgical and restorative procedures. It is
more predictable to preserve an existing papilla than to
regenerate a lost papilla.
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Socket preservation
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ORTHODONTIC TREATMENT
• In general practice, it is often possible to perform minor
orthodontic tooth movements (uprighting molars, closing diastamas
and or extruding of an abutment tooth) before fixed prosthodontic
treatment without referral to an orthodontist. However, a specialist
should be consulted if treatment is more complex than
straightforward tipping, uprighting, or extruding of an abutment
tooth.
• Attempts to correct abnormal tooth relationships or malpositioned
tooth contours with fixed prosthodontic treatment alone are rarely
successful; orthodontic realignment as part of the mouth
preparation is preferred and far more likely to lead to a successful
result.
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1-Uprighting malpositioned abutment
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• improve axial alignment which will lead to
1. direct occlusal forces more favorably, parallel
to the long axes of the teeth
2. conservation of tooth structure as the teeth
will be prepared with more ideal preparation
geometry.
• create more favorable pontic spaces,
• improve embrasure form in the definitive
prosthesis.
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Advantages of uprighting

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DEFINITIVE OCCLUSAL TREATMENT
• Mouth preparation often involves reorganization of the patient’s occlusion,
typically to make maximum intercuspation co-occurrent with centric relation
and concurrently remove eccentric interferences.
• This treatment may be therapeutic, principally to relieve myofascial
symptoms, or performed as a prerequisite to extensive restorative
treatment(e.g:- complete oral rehabilitation), ensuring a reproducible stable
orthopedic position (centric relation) throughout the course of prosthodontic
treatment.
• Occlusal problems that have led to development of pathologic processes
should be diagnosed and alleviated before definitive fixed prosthodontic
treatment is undertaken.
• When selective reshaping of the natural dentition is being considered, it is
important to remember that this is a purely subtractive procedure (tissue is
removed), and it is limited by the thickness of the enamel.
• Before any irreversible changes are made to the dentition, a careful diagnostic
process must establish whether restorations are possibly needed in
conjunction with occlusal reshaping.
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Diagnostic Reshaping(on the cast by
discoid cleoid carver)
• Two sets of articulated diagnostic casts in centric relation are required for diagnostic occlusal
reshaping. One set serves as a reference; the second is used to perform a trial adjustment
and to evaluate how much tooth structure has been removed.
• Alternatively, this diagnostic reshaping may reveal that certain teeth must be built up through
fabrication of crowns in order to achieve an orthopedically stable endpoint.
• The occlusal surfaces of the casts that are to be adjusted are painted with poster paint (which
does not soak into the stone) to demonstrate the extent of any planned corrective reshaping.
• The pin setting on the articulator is recorded at the initial point of occlusal contact in centric
relation before reshaping so that the operator can judge the amount of enamel that must be
removed.
• It can be helpful to also record the pin setting at the maximum intercuspation position.
• The casts are then modified with suitable hand instruments; a discoid-cleoid carver is useful
in achieving the desired result in an efficient manner.
• Each step of the adjustment can be recorded sequentially on a reshaping list or marked on
the side of the casts
• Areas where enamel is likely to be penetrated are identified so that the patient can be
advised of the potential need for additional restorations on those teeth.
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objectives of selective occlusal
reshaping
• To redistribute forces parallel to the long axes of
the teeth by eliminating contacts on inclined planes
and creating cusp-fossa occlusion
• To eliminate deflective occlusal contacts so that,
on completion, centric relation coincides with
maximum intercuspation
• To improve worn occlusal anatomy, enhance
cuspal form, narrow occlusal tables, and
reemphasize proper developmental and
supplemental grooves in otherwise flat surfaces
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contraindications to definitive occlusal
reshaping
1. A patient with bruxism whose habit cannot be
(partially) controlled
2. A diagnostic adjustment that shows that too much
tooth structure will be removed
3. Angle class II occlusion or skeletal class III occlusion)
4. Contact between maxillary lingual cusps and
mandibular buccal cusps (cross bite).
5. An anterior open bite
6. Excessive wear
7. A jaw whose movements cannot be manipulated easily
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Clinical Occlusal Reshaping(on the
patient by pear shaped bur)
• Careful analysis of the diagnostic occlusal reshaping is
necessary to determine whether the patient is a good
candidate for such irreversible subtractive treatment.
• In general, if initial contact occurs relatively close to the
central fossae, adjustment is more predictable than if
such contact occurs on the cusp slopes or even close to
the location of opposing cusps.
• Occlusal reshaping needs to be undertaken in a logical
sequence (elimination of centric interferences then
eccentric interferences) to avoid repetition and
improve the efficacy of treatment.
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Elimination of Centric Relation
Interferences
• As the mandible rotates around the terminal
hinge axis each mandibular tooth follows its
own arc of closure. If the intercuspal and
centric relation positions do not coincide,
premature contacts in centric relation are
unavoidable. Such contacts are removed first.
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Step-by-Step Procedure
• 1. Hinge the mandible, and first mark the teeth throughout the pathway of
any slide that is present: Both the initial contact in centric relation and the
extent and direction of jaw movement to maximum intercuspation should
be marked. The movement, or slide, can be in either an anterior or a
lateral direction. Mark the initial point of contact next in a contrasting
color (black on top of red works well).
• 2. Find any interferences that cause the condylar processes to be
displaced anteriorly (protrusive interferences). These are usually between
the mesial inclines of maxillary teeth and the distal inclines of mandibular
teeth .
• 3. Continue reshaping until all teeth contact evenly (except possibly the
incisors). If excursive movements are guided adequately by the canines, it
may be best to stop reshaping when bilateral canine-to-canine contact has
been reestablished, even if some teeth remain out of contact. (It may be
preferable to build those up with appropriate restorations.)
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• 4. When a laterally displacing prematurity is present, adjust
the buccally facing inclines of the maxillary teeth and the
lingually facing inclines of the mandibular teeth. The
premature contact is usually on either the laterotrusive or
the mediotrusive side of the mandible (lateral slide or
medial slide).
• 5. When dealing with a lateral slide, adjust the buccal
inclines of the maxillary lingual cusps and the lingual
inclines of the mandibular buccal cusps until there is
contact on the cusp tips.
• 6. When dealing with a medial slide, adjust the buccal
inclines of the mandibular buccal cusps or the lingual
inclines of the maxillary lingual cusps until there is contact
on the cusp tips. At this time, any further refinements can
be made through widening of the opposing central grooves
by reduction of the internal inclines of the maxillary buccal
and mandibular lingual cusps.
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Evaluation
• When the discrepancy between
centric relation and maximum
intercuspation has been
corrected, uniform occlusal
contact between all posterior
teeth should be present. This can
be verified with thin Mylar shim
stock held in a forceps .
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Elimination of Lateral and
Protrusive Interferences
• The second phase of occlusal reshaping concentrates on laterotrusive,
mediotrusive, and protrusive interferences. The dentist uses red and blue
marking ribbons to distinguish between centric and eccentric contacts.
• The goals of this second phase of reshaping are to eliminate contact
between all posterior teeth during protrusive movements and to eliminate
any interferences on the nonworking (mediotrusive) side, as well as on the
working (laterotrusive) side.
• In certain patients, group function of the working side contacts should be
considered rather than the more ideal mutually protected occlusion (e.g.,
when there is mobility or poor bone support of the canines).
• In other patients, group function may be retained because of wear or
malpositioning of the canine. During this phase of reshaping, it is essential
that no centric contacts be removed.
• In general, lateral and protrusive interferences are eliminated by the
creation of a groove that enables escape of the functional cusp during
eccentric movement.
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