fixed ii lecture ( 4 ) dr mahy dr saged...

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.

Ste

p-b

y-s

tep

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


Wax coping removal Should be allowed to cool thoroughly before the coping is removed from the die

Ste

p b

y s

tep

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

Ste

p-b

y-s

tep

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


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


Ste

p-b

y-s

tep

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.


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.


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.


Ste

p-b

y-s

tep

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).

fixed ii lecture ( 4 ) dr mahy dr saged...

Documents