Post on 24-Aug-2020
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi
Wax pattern for Posterior teeth
-: The following sequence is recommended for waxing posterior teeth
1. Internal surface. 2. Wax pattern removal and evaluation.
3. Proximal surfaces. 4. Axial surfaces.
5. Occlusal surfaces. 6. Margin finishing.
Internal surface (coping or thimble fabrication) (First layer)
Objective Forming a closely adapted internal surface that the wax must reproduce all retention
features of the restoration.
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Apply die lubricant
(By addition method)
Where pinholes have been prepared, fit in plastic pins that
match the bur used to sink the hole.
Flow wax onto the die from a well-heated, large
waxing instrument (full melting)
Dipping the lubricated die in a pot of melted wax is an
alternative method for making well-adapted internal
surfaces
Give the proximal areas extra bulk to help grip the
coping and prevent its distortion when it is removed
from the die.
Trim the wax back to the margin
If excess bulk carver
If only a thin excess layer burnisher
Pin retained restoration crown pin restoration Partial coverage restoration Increase retention
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi
Wax coping removal Should be allowed to cool thoroughly before the coping is removed from the die
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A sheet of washed rubber dam increases friction and aids
removal.
The fingers of the left hand hold the die.
The right hand holds the pattern.
The die is pulled from the pattern by bending the fingers of the
left hand.
If the pattern fails to move, there may be excess wax beyond the margin, locking the pattern in place.
Evaluation
Objective Perfectly adapted reproduction of the prepared tooth surfaces.
How
Rotate the pattern under a bright light and look for shadows formed
by folds or creases
A binocular microscope or high-quality magnifying loupe (Ten-
power magnification) are helpful
Well-adapted pattern
Poor adaptation
Folds and creases (arrows) indicate that the wax
was not hot enough when applied.
Proximal surfaces
Proximal surfaces gingival to the contact area are normally flat or slightly concave to accommodate
the triangular shape of the posterior embrasures.
Overcontouring Often makes maintaining good periodontal health difficult
Excessively concave or
undercontoured Also make flossing ineffective and must be avoided
Contact areas Reference is made to the size and location of contacts between the contralateral teeth and knowledge of
anatomic form.
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi Size
Large Large proximal contact areas make plaque control more difficult and can lead to
periodontal disease.
Small Very small (point) contacts may be unstable and cause drifting.
Deficient contacts can also lead to food impaction.
Occlusogingival dimension of proximal
contacts:
A Correct
B Too large
C Too small.
Faciolingual dimension of proximal
contacts:
A Correct
B Too broad
C Too narrow.
Location
All maxillary posterior teeth buccal and
occlusal
Except between first and second molar
centralized
All mandibular posterior teeth middle and
occlusal
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Replace the wax coping on the lubricated definitive
cast or removable die.
Note
When a removable die system is used, extreme
care must be taken to ensure that the locating pin
and stone surfaces are absolutely free of excess
wax or other debris that could prevent complete
seating of the die.
To ensure that proximal contacts are not deficient,
a slight amount of stone is scraped from the
adjacent tooth prior to waxing
Wax is added to the contact area (wax additive
technique) to establish a correctly located
proximal contact
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi
Eva
lua
tio
n
The size and location of the contact area are checked
once again by comparing it with the adjacent and the
contralateral teeth.
The proximal surfaces should be flat or slightly concave.
The cervical contour of the restoration should be
continuous with the contour of the unprepared tooth
structure immediately cervical to the preparation margin.
Axial surfaces by ( Addition not dipping ) The buccal and lingual surfaces should be shaped to follow the contours of the adjacent teeth
A Correct
B Incorrect.
The location of the height of contour is generally in the gingival third of most teeth, although on
mandibular molars it is usually in the middle third of the lingual surface.
Em
erg
ence
pro
file
The part of the axial contour that extends from the base of the gingival sulcus
pass through the free margin of the gingiva and extends to the height of
contour producing a straight profile in the gingival third of the axial surface.
A straight emergence profile allows tooth brush bristles to reach into the gingival sulcus.
سؤال مهم جدا
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi
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1. Establish the location, position, and overall outline of the contour, using the
adjacent and contralateral teeth as a guide.
2. Wax the axial surfaces gingivally to form a smooth, flat emergence profile.
3. Add wax to join the axial and proximal surfaces and smooth them, paying
particular attention to the location and shape of the mesial and distal
transitional line angles.
The line angles should correspond to those on the contralateral teeth if those
are intact.
Evalu
ati
on
Evaluate the shape of the tooth at its greatest convexity by looking at the wax
pattern and comparing its shape with that of the contralateral tooth.
Each contact area has four embrasures: gingival, buccal, lingual, and occlusal.
All but the occlusal will have been completed by this stage.
Over contouring
Accumulation of food debris difficult plaque control
inflammatory and hyperplastic changes in the marginal
gingiva.
Under contouring Forced food deflection gingival recession.
Axial contours of full veneer crowns on mandibular molars:
A Correct
B Overcontoured.
We can evaluate the buccolingual dimension with a Boley gauge.
This instrument is also helpful in assessing axial shape and height of contour.
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi
Occlusal surfaces O
bje
ctiv
es
1. The cusps and ridges of the occlusal surfaces should be shaped to allow even
contact with the opposing teeth while stabilizing the teeth and directing forces along
their long axes.
2. Nonfunctional cusps (buccal cusps of the maxillary teeth, lingual cusps of the
mandibular teeth) should overlap vertically and horizontally, preventing accidental
biting of the cheek or tongue and keeping food on the occlusal table.
3. Point contacts between opposing teeth are preferable to broad, flat occlusal
contacts because wear of the restorations is minimized and mastication of tough or
fibrous foods is improved.
Occlusal Scheme
Two occlusal schemes are generally recognized Cusp- marginal ridge Cusp- fossa scheme
The buccal cusps of the mandibular
premolars and the mesiobuccal cusps of the
mandibular molars contact the embrasures
between the maxillary teeth
Mandibular centric cusps contact farther
distally into the fossa of the maxillary tooth
Most adults with a Class I occlusion and unworn teeth will have a cusp- marginal
ridge scheme.
In natural dentitions, the cusp- fossa arrangement is found only when a slight Class 2
malocclusion is present.
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi
Step-by-step
(1)
Cu
sp h
eig
ht
an
d l
oca
tio
n
A, adding wax cones to determine cusp height and location.
B, the cusp’s height is determined by the anteroposterior curve
(curve of Spee).
Cones should follow the anteroposterior curve (curve of Spee) and
the mediolateral curve (curve of Wilson).
C, marking the central fossae of opposing teeth helps position the
functional cusps correctly.
D, all cones are positioned and tested for interferences in all
excursions.
(2)
Com
ple
tion
of
axia
l co
nto
urs
Marginal ridges and cuspal ridges
When viewed from the buccal perspective, each cusp should have a distinct
profile, with the cusp tip highest and a gentle slope down to the marginal
ridges.
Adjacent marginal ridges should be of the same height.
(3)
Tri
an
gu
lar
rid
ges
Give each cusp a triangular ridge.
The apex (or point) of the triangle should be at the cusp tip, and the base should
be in the center of the occlusal surface.
Make the bases of the buccal and lingual triangular ridges convex mesiodistally
and buccolingually.
The triangular ridges are dusted with zinc stearate or powdered wax for
evaluating occlusal contacts.
(4)
Sec
on
dary
rid
ges
All cusps should have a single triangular ridge and two secondary ridges.
Make the secondary ridges convex with grooves where they meet the
convexities of the triangular ridges.
The most mesial and most distal secondary ridges are often contiguous with the
marginal ridges.
(6) Margin finishing ( مهمة جدا )
Ob
ject
ive
To optimize the adaptation of the wax pattern (and the cast restoration) to the die,
the margins must be reflowed and refinished immediately before investing the wax
pattern.
The principal objectives are
(1) Minimizing dissolution of the luting agent.
(2) Keeping metal finishing procedures to a minimum near the margin.
(3) Facilitating plaque control.
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi
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1. Reflowing the margins to create a well adapted1-mm zone
2. A depression (arrows) remains near the margin
3. Wax is added to the margin with a beavertail burnisher
4. Excess wax is removed with a PKT no. 4
5. Margins are finished with a beavertail burnisher
6. Finished margin is viewed from an apical direction
7. Magnification is the most practical way to finish margins
properly.
8. Grooves are finished with a cotton pellet
9. Axial surfaces are smoothed with a cotton roll dipped in die
lubricant
Wax pattern for anterior Teeth
The approach to waxing anterior teeth is slightly different than the approach to waxing posterior teeth.
Labial surfaces Lingual and incisal surfaces
the mesiolabial and distolabial line The location of -1
ines the appearance of anterior , determangles
teeth.
, plaque control may be too bulbouslabial surface is If the -2
difficult, and there may be lingual tilting of the tooth caused
by the force exerted by the upper lip.
When individual anterior teeth are waxed, careful study of -3
can be particularly the embrasure form of adjacent teeth
helpful.
1- The position of the incisal edges is determined by the
and the functional arch form of the anterior teeth overall
occlusal requirements.
can cones ior occlusal surfaces, As with waxing of poster -2
position of be used to initially delineate the approximate
. Additional wax can then be applied as the incisal edge
necessary.
Symmetry can be judged by placing a straight edge near the incisal edge and exactly perpendicular to the
palatal midline.
Fixed II Lecture ( 4 ) Dr Mahy Dr SaGeD LoAi Waxing Connectors
The connectors that join the separate components of a fixed dental prosthesis are created in wax just
before the margins are finalized.
rolled by forming them in waxThe shape, size, and location of connectors can be cont
.Considerations for anterior connector placement
1. Mechanically, the connector should be as large as possible for strength.
2. From a biologic perspective, the connector is most effectively placed in the incisal half of the
proximal wall (at least 1 mm above the crest of the interproximal soft tissue).
3. For esthetics, the connector should be placed in the lingual (palatal) half of the proximal wall (hidden
behind the esthetic ceramic veneer).