Assist.lec. Ahmed Basim Complete Denture 3rd Year 1

Assist.lec. Ahmed Basim Complete Denture 3rd Year

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Impression material

Week 1

A dental impression : is defined as the negative record of the tissues of the mouth . It

is used to reproduce the form of the teeth and surrounding tissues.

Complete denture impression : A complete denture impression is a negative

registration of the entire denture bearing, stabilizing and border seal areas present in

the edentulous mouth.

Diagnostic impression :The negative replica of the oral tissues used to prepare a

diagnostic cast. used for study purposes like measuring the undercuts, locating the path

of insertion. Is made as a part of treatment plan and to estimate the amount of pre-

prosthetic surgery.

Preliminary impression (primary impression) :A preliminary impression is an impression

made for the purpose of diagnosis or for the construction of a tray final impression.

Final impression is an impression for making the master cast.

Impression material: Any substance or combination of substances used for making an

impression or negative reproduction

Requirements of impression materials:

1. Must be a semi-liquid material that will flow and adapt itself around the structure

of interest.

2. It must set and harden into a solid that is rigid enough to be removed from the

mouth without becoming deformed.

3. Copy details accurately.

4. Dimensional stability after removal from the mouth appropriate working time

(from the start of mix).

5. Appropriate time to harden in the mouth (setting time).

6. Bio-compatibility/Aesthetic, odor/taste acceptable.

7. Chemically compatible with material used to pour cast.

8. Can be disinfected without any changes of properties.

9. Economic or not expensive.

10. Adequate shelf life for storage.


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Impressions (classification)

There are many types of classification, the most common classification used in

complete denture construction is based on type of impression and area of use :

1. Primary :Impression compound and Alginate.

2. Secondary: Zinc Oxide Eugenol (ZOE) , Elastomers for CD and Plaster of paris.

Primary impression

The primary impression, taken in an edentulous stock tray, is needed to record enough

detail for a special tray to be made. The primary impression should reproduce Certain

anatomical landmark which indicates the correct extension of the special tray (eg

maxillary tuberosity and retromolar pads. It is usually taken in impression compound

or impression plaster (not suitable if undercuts present).

Final impression Objectives

To obtain an impression from which a retentive, stable and comfortable denture base

can be constructed. To record as accurately as possible the shape of the mucosa

overlying the alveolar ridges and hard palate together with functional depth and width

of sulci.

Classification of impression materials

1- Non-elastic impression

a. Plaster of Paris

b. Impression Compound

c. Zinc oxide eugenol and.

d.Wax. Must not have undercuts

2. Elastic: can be used in undercut (Hydrocolloids)

Hydrocolloids (Hydro=water kola=glue Oid=like)


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a. Reversible (agar)……solution ↔ gel (temperature) physical reaction

b. Irreversible (alginate)…..solution.→ gel Chemical reaction

c. Elastomers Polysulfide (PS) set by polymerization Silicon rubber (AS and CS)

Polyethers (PE).

Impression plaster

Impression plaster: Rarely used these days because it’s brittle and fractures very easily.

advantages

1- Easy to mix Working time 2-3 min Setting time 2-3 min

2- Good dimensional stability and accuracy

3- Cheap

Impression plaster Disadvantages

1- Low strength

2- Rough surface

3- Poor abrasion resistance

4- Rigid once set

5- Dry sensation in the mouth .

Impression compound they are thermoplastic materials softened to their working

consistency by immersion in hot water or by warming over the flame (reversible

impression material sets by physical change) Rigid after setting and has poor elastic

properties supplied as sheets, sticks, cakes and cones.


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Advantages of Impression compound

1- Cheap and reusable.

2- Does not produce irritation to patient.

3- Can be remodify and resoften again till the accurate impression is obtain.

Disadvantages of Impression compound

1- Difficult to record details because of high density.

2- Distortion due to poor dimensional stability.

3- Difficult to remove from severe undercuts.

4- Does not have pleasant taste.

Zinc oxide eugenol impression

Available as: base paste(white in colour) Accelerator or reactor or catalyst paste(red in

colour.


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Properties:

1. Good consistency and flow.

2. Detail reproduction.

3. Rigid and having good strength

4. Good dimensional stability.

Advantages:

1. It has enough working time to complete border moulding.

2. It can be checked in mouth repeatedly without deforming.

3. It registers accurate surface details.

4. It is dimensionally stable.

Disadvantages:

1. Requires special tray for impression making.

2. Sticky in nature and adheres to tissues.

3. Burning sensation of eugenol causes tissue irritation.

4. Highly inelastic in nature.

Non-eugenol pastes are developed to overcome the burning sensation caused by

eugenol used in eugenol irritant patients.

Impression waxes

Impression waxes are rarely used to record complete impressions but are normally

used to correct small imperfections in other impressions.

Elastomeric impression material

Polysulfide rubber impression material has a polysulfide polymer base that reacts

with sulfur with the help of a catalyst. This impression material has good elastic

property and excellent tear strength. However, this impression material has

unpleasant smell. It is available in different consistencies. Condensation-cured

silicones consist of a base material and a catalyst. The base material is a dimethyl

siloxane with 35-70% silica filler.

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Alginate: Alginate is an elastic, irreversible hydrocolloid impression material that

transfer from the solution phase to the sold phase by chemical reaction. It is one of

the most frequently used dental materials.

Advantages of alginate over other impression materials

1- Ease of mixing and manipulation.

2- Minimum equipment.

3- Flexibility of the set impression material.

4- Accuracy if properly handled.

5- Cost effectiveness.

Alginate Disadvantages

1- It cannot be corrected

2- Poor dimension stability

3- Poor tear strength

4- Distortion may occur if not properly handelled.


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Anatomical landmarks

Week 2

The anatomy of edentulous ridges in the maxilla and mandible is very important

for the design of the complete denture, the total area of support from the

mandible is significantly less than from the maxilla.

Important terms:

Limiting structures-they determine and confine extent of dentures .

Supporting structures- these are the load bearing areas- They show minimal

ridge resorption even under constant load.

Relief areas- these areas resorb under constant load or contain fragile structures

within

The anatomical landmarks in the maxilla are:


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Limiting structures:

1. Labial frenum

2. Labial vestibule

3.Buccal frenum

4. Buccal vestibule

5.Hamular notch

6.Posterior palatal seal area

Supporting Structures

Primary stress bearing areas:

1∙ Hard palate

2 ∙ Postero- lateral slopes of residual alveolar ridge.

Secondary stress bearing areas

1.Rugae

2 .Maxillary tuberosity

3. Alveolar ridge.

Relief areas:

1.Incisive papilla

2.Cuspid eminence

3.Mid- palatine raphe

4.Fovea palatina.


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SUPPORT FORTHE MAXILLARY DENTURE The ultimate support for the maxillary denture is the bone of the two maxillae and the palatine bone. The palatine processes of the maxillae are joined together at the midline in the median suture.

RESIDUAL RIDGE: The shape and size of the alveolar ridges change when the

natural teeth are removed. The alveoli become mere holes in the jawbone and

begin to fill up with new bone, but at the same time the bone around the margins

of the tooth sockets begin to shrink away. This shrinkage, or resorption, is rapid

at first, but it continues at a resorbed rate throughout life.

Labial frenum: The maxillary labial frenum is a fold of mucous membrane at the

median line. (No muscle attachment). This band of tissue starts superiorly in a fan

shape and converges as it descends to its terminal attachment on the labial side

of ridge.

Labial Vestibule: This anterior region of maxillary basal seat extends from one

buccal frenum to the other on the labial side. The major muscle in this area is(

orbicularis oris). Three objectives are apparent: The impression must supply

sufficient support to the upper lip to restore the relaxed contour. The labial

flange of the impression must have sufficient height to reach the reflecting

mucous membrane of the labial vestibular space. There must be no interference

of the labial flange with the action of lip in function.

Buccal Frenum: The buccal frenum is sometimes a single fold of mucous

membrane, sometimes double, and in some mouths, broad and fan shaped.

Associated muscles are: ∙ Buccinator , Orbicularis oris and Levator anguli oris.

Buccal Vestibule: The buccal vestibule extends from the buccal frenum to the

hamular notch. It is influenced by the buccinator and the modiolus. And distally

by the coronoid process of mandible.

Hamular Notch: Is a displaceable area about 2mm wide , between the

tuberosity of the maxilla and the hamulus of the pterygoid plate.


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Vibrating line of the palate: This is an area at or distal to the junction of hard and

soft palate where movement occurs when patient says “ah”. The area may also

be identified by “Valsalva maneuver ” by asking the patient to close his nose using

his fingers and asking him to blow gently through the nose . Posterior vibrating

line That is 4-12mm or on an average is 8.2 mm dorsally to the hard and soft

palate junction. In most instances the denture should end 1 or 2mm posterior to

the vibratory line.

Maxillary Tuberosity: The maxillary tuberosities are the distal aspects of the

posterior ridges.


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Anatomical land mark of mandibular arch

Limiting structures:

Limiting structures

Labial frenum

Labial vestibule

Buccal frenum

Buccal vestibule

Lingual frenum

Alveolingual sulcus

Retromolar pad

Pterygomandibular raphe

Labial frenum: This is single narrow band but may consist of 2 or more bands.

The activity of this area tends to be vertical so the labial notch on the denture

should be narrow.

Labial vestibule: It is the sulcus between the buccal frenums.


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Buccal frenum: This is usually in the area of 1st pre molar. The oral activities in

these area are horizontal as well as vertical (ex. Grinning and puckering) thus

needing wider clearance.

Buccal vestibule: The buccal vestibule extends from the buccal frenum posteriorly

to the outside back corner of the retromolar pad and from the crest of the

residual alveolar ridge to the cheek.

Lingual frenum: It is a fold of mucous membrane existing when the tip of the

tongue is elevated.

Alveololingual sulcus: Extends from lingual frenum to retromylohyoid curtain

Divided into 3 parts:- anterior, middle and posterior

Anterior region- from lingual frenum to premylohyoid fossa Flange is shorter

anteriorly and should touch the floor of the mouth when tip of tongue touches

upper incisors.

Middle- extends from premylohyoid fossa to distal end of mylohyoid ridge

Shallower due to prominence of mylohyoid ridge and action of mylohyoid muscle

Posterior- retromylohyoid fossa Typical S form of lingual sulcus .

Retromolar pad: Pear shaped of triangular keratinized soft pad of tissue at distal

end of ridge, bounded posteriorly by tendons of temporalis, laterally by

buccinators and medially by pterygomandibular raphe and superior constrictor,

its the posterior seal of mandibular denture.

Supporting structures

Buccal shelf area

Residual alveolar ridge

Buccal shelf area: The area between the mandibular buccal frenum and the

anterior edge of the masseter is known as the buccal shelf . It is bounded

medially by the crest of the residual ridge , anteriorly by the buccal frenum ,

laterally by the external oblique line and distally by retromolar pad. The buccal


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shelf forms the primary support for the mandibular denture as it is made

primarily of cortical type of bone(dense bone type) and lies at right angles to

occlusal forces.

Residual alveolar ridge: edentulous mandible may become flat with concave

denture bearing surface in such cases, structures attaching on lingual side of ridge

attach over the ridge due to resorption mandible inclines outwards and becomes

progressively wider.

Relief area:

Mental foramen

Genial tubercle

Mylohyoid ridge

Mandibular tori

Mental foramen: It lies between the 1st and 2nd premolar region. Due to ridge

resorption, it may lie close to the ridge. It should be relieved in these areas as

pressure over the nerve passing through it can get compressed by denture base

leading to paraesthesia (numbness) of lower lip.

Genial tubercle: the genial tubercle are a pair of dense prominences at the

inferior border of the mandible at the lingual midline.

Mylohyoid ridge: the mylohyoid ridge is a bony prominence along the lingual

aspect of the mandible Soft tissue usually hides the sharpness of the mylohyoid

ridge anteriorly, this ridge with mylohyoid muscle is close to the inferior surface

of the mandible Posteriorly, after resorption, it often flushes with the residual

ridge.The mucosa membrane overlying the sharp or irregular mylohyoid ridge

needs to be relieved because denture base might easily traumatize it.

Mandibular tori : These are the abnormal bony prominence found bilaterally on

the lingual side, near the premolar region but they may extend posteriorly to the

molar area, It is covered by thin mucosa.


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Special tray

A special tray is a custom made device prepared for a particular patient which is

used to carry, confine and control an impression material while making an

impression.

Ideal Requirement

It should be well adapted to the primary cast.

It should be dimensionally stable on the cast and in the mouth.

The tissue surface should be free of voids or projections.

It should be at least 2 mm thick in the palatal area and lingual flange for

adequate rigidity.

It should be rigid even in thin sections.

It should be easy to remove.

It should not react with the impression material.

It should have a contrasting color to make its margins appear prominent.

Customized tray materials

1. Light-cure resins.

2. Auto polymerizing acrylic resin.

3. Vacuum-form poly vinyl.

4. Thermoplastic materials.

Types of Special Tray Design

1. Close-fitting special tray.

2. Spaced special tray.


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1) Close-fitting trays

Where the majority of the denture-

bearing area is free from large undercuts,

closefitting trays should be used. They allow

pressure to be exerted on the denture-

bearing area during the impression-taking

procedure. Usually used with impression

materials that are non elastic or rigid once

set, typically zinc oxide eugenol paste.

2) Spaced trays

When a large undercut areas prohibit the use of close-fitting trays as removal

from the mouth without causing distortion would be difficult and removal from

the cast model would cause fracture of the cast. This type of custom tray can be

used with alginate, elastomeric and impression plaster impression materials.

The spacing between the tray and the tissues should be increased according to

the depth of undercut, tear strength and elastic limit of the impression material.

Alginate has low tear strength and requires adequate bulk to remain intact on

removal. Trays for alginate are

perforated to allow mechanical retention

to retain alginate in the tray. It is

important not to place the perforations

too close to the edge of the tray. If the

clinician needs to adjust any

overextension of the tray they may grind

into the perforations.

An extraoral handle is placed anteriorly

and includes a step to ensure that it exits the mouth between the lips without

displacing them.


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Fabrication of the Special tray

Firstly should be determine the peripheral extension made by using the primary

model.

Maxilla extension identification:

identify the junction between the hard and soft palate (fovea palatinae)

and use this landmark as the periphery of the tray

ensuring that the entire tuberosities are included

the distal extension of maxillary impression trays should extend to the

fovea palatine and extend beyond the tuberosities to the hamular notches.

Mandible extension identification:

include the retromolar pad

extend into the lingual sulcus such that the periphery is just short of the mylohyoid ridge

buccally to be just short of the external oblique ridge.

Step 1 – model preparation

1. Draw the extent of the tray 2 mm

toward the alveolar ridge from the

deepest part of the sulcus.

2. The borders of the special tray should be marked using a pencil.

3. The cast should be soaked in slurry water.


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4. For close-fitting custom trays, any undercuts should be filled with modeling wax. This ensures that the tray can be removed from the model after casting without fracture of the study model.

5. If the tray is to be spaced, adapt the

appropriate thickness of modeling wax (1.5-

2mm) to the model and trim short of the

required extension of the tray.

6. Spacers should be cut out in 2-4 places so that the special tray touches the

ridge in these areas.

The part of the special tray that

extends into the cut out of the

spacer is called stopper.Four

stoppers are placed, two on the

canine eminences on either side

and two on the posterior parts of

the ridge for stabilize the tray during impression making. The stopper can

be a (2 mm) square, or (2 x 4) mm rectangle over the crest of the ridge.

7. The separating medium is applied to avoid the special tray from binding to the

cast.


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Step 2– Tray construction

Using Light cure acrylic material

1.Adapt the light-curing blank to the model, or over the wax spacer, taking care to

avoid thinning the material.

2.Trim the excess material with a wax knife to the required peripheral extension.

3.the material is cured by placing in an ultraviolet (UV) light box.

4.The curing process usually takes approximately 2 minutes; however the light

source may not cure the full depth of the material, particularly underneath the

handle. Therefore it should be removed carefully and the curing cycle repeated

with the tray inverted and any wax removed.

5.The final extension can be ground using a tungsten carbide bur and micromotor.

Using Cold cure Acrylic – Dough Technique

The powder and liquid should be mixed in a mixing jar in the ratio of 3:1 by volume.

1. sandy stage, where the polymer is soaked in monomer.

2. stringy stage – where if the material is touched sticking to the finger.

3.Dough stage – In this stage, the material is very workable.

4.Rubbery stage – where the material cannot be manipulated any more..

5.Stiff stage – The material loses its elasticity and becomes more plastic. After the

stiff stage, the polymerization is almost complete.


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Procedure:

Manipulation is done in the late stringy and the dough stages. The material is kneaded in the hand, to achieve a homogenous mix.

Then the material is shaped into a 2 mm thick sheet. Flattening the dough can be done using a roller or a plaster mould or by pressing the material between two glass slabs.

The rolled sheet of acrylic is adapted over the cast from the center to the periphery. This prevents the formation of wrinkles.

Care should be taken not to apply excessive pressure on the ridge areas as it might lead to the thinning of the tray.

The excess material should be cut out with a wax knife before the material

sets.

The set material is then trimmed to obtain a smooth surface with smooth

margins.

The handle is fabricated using the excess dough material.

Step 3 – Finishing the tray

Finishing the special tray with acrylic bur by micromotor.

Final smoothing may be achieved using a sandpaper mandrel.

Base plate

base plate, record base: Is a temporary substance representing the base of the

denture which is used for making maxillo-mandibular relation record and for

arrangement of the teeth.


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Ideal Requirement of Base Plate

A base plate should be rigid.

Dimensionally stable at working temperatures.

Extend over the entire denture-bearing area.

Allow adjustment to the periphery chairside.

Materials Used for the Fabrication of Base Plate

Light-cured acrylic

Cold cure acrylic

Heat cure acrylic

Wax

Shellac base plate is the most suitable material. If wax or shellac are used, consideration should be given to the possible distortion in the mouth due to an increase in temperature.

Fabrication of a Denture Base

The method of making a denture base is similar to the special tray but it is made without spacer and without handle.

The difference between fabricating the base of the special tray and the denture base is where the border for base plate should extend till the depth of sulcus.

Occlusal Rim

Occlusal Rim Occluding surface built on temporary denture base for the purpose of making maxillo-mandibular relation and for arranging artificial teeth to form the trial denture. They usually fabricated to larger size so that they can be reduced as needed.After the fabrication of denture base, it is followed by the formation of occlusal rim.


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Purpose of Occlusal Rim

1. To record various maxillo-mandibular relationship.

2. To record lip line.

3. To record horizontal and vertical overlaps.

Dimensions used to fabricate a standard occlusal rim

A) Maxillary Occlusal Rim

It should be 22 mm high from the depth of the sulcus at the region of the canine eminence.

It should be 4 to 6 mm wide in the anterior region

The occlusal table should be 18mm high when measured from the depth of the sulcus in the posterior region.

The occlusal table should be 8 to 12 mm wide in the posterior region.


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B) Mandibular Occlusal Rim

It should be 6 to 8 mm high when measured from the crest of the ridge in the anterior region.

It should be 18 mm high when measured from the depth of the sulcus in the canine eminence region.

The occlusal plane should flush to anterior two-third height of the retromolar pad in the posterior region.

The width of the occlusal table should be 4 to 6 mm in the anterior region and 8 to 12 mm in the posterior region.

Technique of fabrication

Rolled wax technique

1. sheet of base plate wax is taken and one end of the sheet is softened over the flame and rolled to a width of 4 mm.

2. The wax should be softened adequately and rolled carefully to avoid the entry of air bubbles.

3. The roll is again heated over the flame and consecutive rolls are made to form a single thick cylinder of wax.

4. The rolled cylinder of wax is adapted over the base plate such that it follows the arch curvature.

5. Maxillary occlusal rims are usually ‘U’ shaped.

6. Mandibular occlusal rims are ‘V’ shaped or a less wider ‘U’.

7. The adapted wax is sealed to the base plate on the lingual/palatal surface using a hot wax knife. Molten sticky wax can also be used for the same purpose.


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8. The outer surfaces of the occlusal rim are shaped with the aid of the tail end of a hot wax knife. The lingual surface is also shaped similarly.

9. The occlusal rim should be shaped such that it tapers towards the occlusal plane with a trapezoidal cross-section.


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Week 4

Maxillo-mandibular relationship

any spatial relationship of the mandible to the maxilla. Also called jaw relations.

Three types of maxillomandibular relations:

1. Orientation relation

2. Vertical relation

3. Horizontal relation.

Classification of Jaw Relation

Orientation Relation

Vertical Relation

a.Vertical dimension at rest

b. Vertical dimension at occlusion

Horizontal Relation

a.Centric Relation

b.Eccentric Relation

Orientation relation: Relations of the jaws to references in the cranium.

Physiologic rest position

The postural position of the mandible when an individual is resting

comfortably in an upright position and the associated muscles are in a state of

minimal contractual activity.


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Vertical dimension: The distance between two selected anatomic or marked

points (usually one on the tip of the nose and the other upon the chin).

Rest vertical dimension (RVD): The distance between two selected points (one

of which is on the middle of the face or nose and the other of which is on the

lower face or chin) measured when the mandible is in the physiologic rest

position.

Occlusal vertical dimension (OVD): The distance measured between two points

when the occluding members are in contact.

Interocclusal rest space: The difference between the vertical dimension of rest

and the vertical dimension while in occlusion. Also called Freeway Space. The

freeway Space, the Space between wax rims at physiologic rest position usually

2-8 mm.

Free way space = RVD - OVD

Centric relation: is the relationship between the maxilla and mandible when

the lower jaw is in its optimal position (when the condyle heads seat uppermost

and rearmost position of the glenoid fossa).


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The most commonly used method to position the mandible in centric

relation is to ask the patient to curl the tip of the tongue to the soft palate,

encouraging the condyles to seat.

Importance of centric jaw relation:

1. It is learnable, repeatable, and recordable position which remains

constant throughout life.

2. It is a reference position from which the mandible can move to any

eccentric position and return back involuntarily.

3. It is the start point for developing occlusion.

4. Functional movements like chewing and swallowing are performed in this

position, because it is the most unstrained position.

5. It is a reliable jaw relation, because it is bone to bone relation.

Centric occlusion: The occlusion of opposing teeth when the mandible is in

centric relation, when the teeth in maximum intercuspation.


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Eccentric relation: It’s any relationship of the mandible to the maxilla other

than centric relation. Eccentric jaw relation two type:

a-Protruded or forward relation.

b-Left or right lateral relation.

Protrusive relation: The relation of the mandible to the maxillae when the

mandible is thrust forward.

Lateral relation: The relation of the mandible to the maxilla when the lower

jaw is in a position to either side of centric relation.

While the working side the side towards which the mandible moves in a

lateral excursion, and nonworking side that side of the mandible that moves

toward the median line in a lateral excursion. The condyle on that side is

referred to as the nonworking side condyle.

Occlusal plane: The average plane established by the incisal and occlusal

surfaces of the teeth. the surface of wax occlusion rims contoured to guide

in the arrangement of denture teeth.

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Week 5

Mounting: It is the procedure of attaching the maxillary and mandibular casts

to the articulator in their recorded jaw relation. It is also called articulation.

The maxillary cast is first articulated, and then the mandibular cast is

articulated after recording the vertical and centric jaw relations.

Zeroing or resetting the articulator before the mounting

1. The articulator should be clean from any remnant of previous plaster.

2. The movable surfaces of the articulator should move freely without any

hindrance.

3. The incisal pin should be flushed with the top of upper member of articulator

to give zero reading.

4. The mounting table should be properly fixed to the articulator.

Prepration the casts for mounting

1. Determine the midline of the cast according to the midline of incisive papilla

and continue this line posteriorly all around the cast.

2. The casts should be placed in slurry water for better adhesion of the casts to

the mounting plaster.

3. With wax knife or hand piece , three V-shape

cuts on the base of upper and lower casts, so as

to facilitate the laboratory remounting.

4. Lightly coated the base of the casts with Vaseline or any separating medium.

5. The base plate with occlusion rim should be sealed to the cast by wax.


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Mounting of the maxillary cast

The maxillary cast is first attached to the upper member of the articulator after

orientation jaw relation by using the face-bow with adjustable type of

articulators, while for the mean value articulator use the mounting table to

support the maxillary occlusion rim in its position during mounting. The

mandibular cast is articulated after recording the vertical and centric jaw

relations .After recording the orientation jaw relation.

The following steps are carried out:

1. Enough space should be present between the base of the cast and the upper

member of the articulator to accommodate for the plaster material over the

cast. If there is not enough space trimming should be done to the base of the

cast.

2. Alignment of the midline of the maxillary occlusion rim to the center of the

cross midline which found on the mounting table anteriorly and posteriorly, so

that the cast will be centralized to the mounting table and the occlusal rim fixed

to the mounting table by wax.

3. Plaster is mixed, then the plaster is poured over the base of the cast and the

upper member is closed until the incisal pin touches the incisal table.

4. Smoothing and polishing of the plaster is done. The mounting should be

cleaned and any debris removed from the articulator and mounting table.


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Mounting the mandibular cast

The mandibular cast is mounted after recording the tentative vertical and

centric jaw relations.

1.The mandibular occlusion rim should be well secured to the mandibular cast

with it record base by using wax, also sealing should be done between the

maxillary and mandibular rims after making tentative centric jaw relation.

2. Care should be taken that there is no posterior interference between the

maxillary and mandibular casts.

3. The articulator with the mounted maxillary cast is inverted to aid in the

mounting the mandibular cast.

4. The maxillary occlusal rim with mandibular occlusal rim (centric record) placed

on the maxillary cast.

5. The mandibular cast is placed on the mandibular occlusal rim (It should be

soaked in slurry water before mounting).

6.The plaster is mixed and poured over the base of the mandibular cast and the

articulator is closed until the incisal table touch the incisal pin, then the plaster

should be smoothed and polished.

Mandibular cast mounting

Maxillary cast mounting


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Checking the mounting

1. The midline of maxillary cast should be coincided with the midline of

mandibular cast and midline of articulator.

2. Centralization of maxillary cast with upper member of articulator then the

centralization of lower cast which depend on accuracy of the maxillary cast.

3. Incisal pin checked if it does not touch the incisal table.

Errors may be occurred during mounting

1. The record base not properly secured to the cast.

2. Checked if there is any contact between the maxillary and mandibular casts

Interference of the casts posteriorly.

3. The incisal pin does not touch the incisal table.

4. The incisal pin is not properly screwed.

5. Wrong transference of the midline of the articulator with that of the casts

(shifting of the midline).

6. Movement of the casts during mounting.

7. Maxillary and mandibular rims are not properly fixed after making centric

record.

8. Dimensional changes in the plaster material.


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Articulator: It is a mechanical instrument that represents the temporomandibular

joints and jaw members, to which maxillary and mandibular casts may be attached

to simulate some or all- mandibular movements.

Functions

1. It allows most of the prosthetic work to be done in the absence of the patient

(diagnosis, treatment planning, setting –up of teeth and development of balanced

articulation and waxing-up of dentures).

2. Maintain jaw relation record during setting-up of teeth.

3. Denture remounting after processing for correction of occlusal disharmony

Types of articulators

1-Simple hinge articulators.

2-Fixed or mean value condylar path articulators.

3-Adjustable condylar path articulators.

a.Semi-adjustable condylar path articulators.

b.Fully-adjustable condylar path articulators.

Simple Hinge Articulators

It consists of upper and lower members held apart at a certain distance by a

screw which acts at the back. The screw can increased or decrease the

distance between the two members, and permits only a hinge like

movement.

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Possible movements: This type of articulators gives only opening and closing

movements.

Records required:

a. Vertical dimension of occlusion.

b. Centric relation records.

Disadvantages: These articulators do not represent the temporomandibular

joint and the dynamic mandibular movements.

Mean value or fixed condylar path articulators

It is non-adjustable articulator. Designed using fixed dimensions,

which are derived from average distance between the incisal and condylar

guidance of the population. Condylar guidance equivalent to glenoid fossa is

attached to the lower member and condylar element equivalent to

mandibular condyle is attached to the upper member, hence it is a non acron

articulator.


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Components of articulator

1. Upper member: It is a triangular frame with the base of the triangle placed

posteriorly. The apex of triangle contains a provision to accommodate the

incisal pin. Two condylar elements are seen projecting on either side of the

base of the triangle. They articulate with the condylar guidance of the lower

member. The maxillary cast is attached to the upper member during

articulation.

2. Lower member: L shaped frame with horizontal and vertical arm.The

horizontal arm is triangular in shape and corresponds to the upper member.

The apex of the triangle of the horizontal arm contains the incisal guide table.

The vertical arm is rectangular containing the condylar guidance slot at the

upper position.

3. Incisal guide table: It is defined as „that part of the articulator which

maintians the incisal guide angle.

4. Incisal pin: It helps to keep a fixed distance between the upper and lower

members at the anterior end. The vertical rod has a pointed tip, which should

rest on the centre of the incisal guide table during articulation.

Possible movements

1-Opening and closing.

2-Protrusive movement at a fixed horizontal condylar path angle.

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Adjustable Condylar Path- 3 Articulators

A- Semi Adjustable Condylar Path Articulators

have adjustable horizontal condylar

paths, adjustable lateral condylar path,

adjustable incisal guide table and adjustable

inter-condylar distance.

Possible movements

1-Opening and closing.

2-Protrusive movement to an angle

recorded from the patient.

3-Lateral movement to an angle calculated

from the Hanau’s formula:

L=H/8+12.

Where; L = the lateral condylar path

H = the horizontal condylar path angle which is recorded from the patient.

B- Fully adjustable articulators

An articulator that allows

replication of 3-dimentional

movement of recorded mandibular

motion. They differ from the semi-

adjustable articulators in that the

lateral condylar path inclinations are

adjusted according to records taken

from the patient.


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Week 7

Face-bow: The face-bow is a caliper- like device that is used to record the

relationship of the maxilla to the temporomandibular joints or the opening axis of

the jaws and to orient the casts in this same relationship to the opening axis of the

articulators.

The face-bow consist of :

1. U -shaped frame It forms the main frame of the face bow. All other components

are attached to this frame It extends from the region of TMJ on one side to the

other side without contacting the face.

2. Condylar rods Two small metallic rods on either side of the free end of the U

shaped frame that contact the skin over the TMJ .They are used to locate the hinge

axis and transfer it to the articulator Some face bows have ear piece that fit into

the external auditory meatus instead of condylar rods.

3. Bite fork “U” shaped plate, which is attached to the occlusal rims, while recording

the orientation relation. It is attached to the frame with the help of a rod called the

stem.

4. Locking device This part of the face bow helps to fix the bite fork to the U-shaped

frame firmly after recording the orientation jaw relation.


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5. Third reference point It is used to orient the face bow assembly to an anatomical

reference point on the face along with the two condylar reference points. It varies

in the different face bows, example orbital pointer-orbitale, Nose piece – Nasion

etc.

Types of face-bow

There are two basic types of face-bow;

1. The kinematic, and

2. The maxillary.

1. The kinematic ( mandibular, hinge axis locator) face-bow: It is used to locate

the kinematic (true or terminal) transverse hinge axis. The transverse hinge axis is

an imaginary line, in which the mandible rotates during opening and closing for

about 20 mm.

2. The maxillary face-bow: It is used to record the position of the upper jaw in

relation to the hinge axis and transferring the relation to the articulator. The

maxillary face-bow is oriented to the kinematic or arbitrary hinge axis. The arbitrary

axis is positioned on a line extending from the outer canthus of the eye to the

middle of the tragus of the ear and approximately 13 mm in front of the external

auditory meatus. The ear face-bows are designed to utilize an arbitrary axis by

fitting into the external auditory meatus.


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Important of the face-bow:

1. An arbitrary mounting of the maxillary cast without a face-bow transfer can

introduce errors in the occlusion of the finished denture.

2. A face-bow transfer allows minor changes in the occlusal vertical dimension on

the articulator without having to make new maxillomandibular records.

3. It is helpful in supporting maxillary cast while it is being mounted on the

articulator.


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Week 8

Occlusion

Occlusion is a concept that is pertinent to all dental patients whether they have

their own teeth or not.

Occlusion: It is a term used to describe the contact relationship between the upper

and lower teeth, when the teeth contact, they exert forces that are either

distributed via the periodontal membrane, for those with natural teeth, or through

the supporting mucosa for those with removable type prosthesis.

So occlusion is bringing the mandibular teeth up into contact with the

maxillary teeth. This is a static position when the jaws are centrically or

eccentrically related. The occlusal schemes provided for complete dentures differ

significantly from those found in most natural

dentitions. The dentate occlusion is often canine

guided or demonstrates group function. In each case

the teeth contact on the working side but usually

disclude on the non-working side in lateral

excursions. Similarly, the posterior teeth disclude in

protrusive excursions (Christensen's phenomenon).

Dentures are different; the occlusion is designed to provide stability.

Therefore the non-working side teeth also contact in lateral excursions to prevent

the denture from tipping, giving rise to the term balancing side. The posterior teeth

also contact in protrusive excursions.

Centric occlusion: is the occlusion of opposing teeth when the mandible is in centric

relation. This may or may not coincide with the

maximal intercuspal position.

Centric jaw relation: is the most posterior relation of the lower to the upper jaw

from which lateral movements can be made at a given vertical dimension.


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Goals of complete denture occlusion

1. Minimize trauma to the supporting structures.

2. Preserve remaining structures.

3. Enhance stability of the denture.

4. Facilitate esthetic and speech.

5. Restore masticatory efficiency to a reasonable level.

Types of complete denture occlusion:

1. Bilateral balance occlusion.

2. neutro centric occlusion (monoplane occlusion).

3. lingualized occlusion.

Bilateral balance occlusion

Concept means the simultaneous contacting of the upper and lower teeth on the

right and left sides and in the interior and posterior occlusal surfaces. It’s a

modification of the balanced occlusion.

In centric and eccentric positions. Teeth should be arrange tightly in centric

occlusion that the facial cusps of the mandibular teeth contact the central fossae

of the maxillary teeth while the lingual cusps of maxillary teeth fit into the central

fossa of the mandibular teeth, this facial overlap prevents check biting when the

dentures are completed. There two types of balance occlousion:

1. Protrusive balanced Occlusion This type of

balanced occlusion is present when mandible

moves in a forward direction and the occlusal

contacts are smooth and simultaneous anteriorly

and posteriorly. There should be at least three

points of contact in the occlusal plane. Two

located posteriorly and one anteriorly. Absent in

natural dentition. Posterior contact during protrusion to maintain balance.


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2. Lateral Balanced Occlusion In lateral balance there

will be a minimal simultaneous three point contact

present during lateral movement of mandible.

This is absent in natural dentition. Teeth should be

arranged such that there is simultaneous tooth

contact in balancing side and working side.

The importance of balance occlusion in complete denture:

1. It avoids displacement of denture during functional movements.

2. It assist in earlier repositioning of denture which become displaced during

mastication.

3. During swallowing of saliva, teeth come in contact and this contact demand

equal pressure with satisfactory position of the cusp in the opposing fossae.

If there is no balanced occlusion the cusp will hit in the opposing fossa result

shifting of the denture base which lead to unstable denture also lead to trauma to

the supporting tissue and discomfortable and then resorbtion. Balanced occlusion

will minimize the period that required for adaptation of patient to the denture. So

bilateral balanced denture occlusion lead to stable simultaneous contact of

opposing upper and lower teeth in centric relation position with smooth bilateral

gilding contact to any eccentric position within the normal range of mandibular

function developed to lessen or limit tipping structures.

Neutro centric occlusion (Monoplane occlusion)

This concept of occlusion assumes that the interior- posterior plane of

occlusion should be parallel to the denture foundation area and not dictated by

condylar inclination. The plane of occlusion in this concept is completely flat and

level there is no curve of Wilson or compensating curve.


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Lingualized occlusion concept

The lingual cusp tips of maxillary teeth should be in contact with the central fossae

of the opposing mandibular teeth. The cuspal inclines in of the mandibular teeth

are relatively flat resulting in potentially less lateral forces and displacement during

function. Lingualized occlusion indicated in:

1. Sever mandibular ridge atrophy.

2. Displaceable supporting tissues.

3. Malocclusion.

4. High aesthetic demands and in patients with previous successful dentures with

lingualized occlusion.


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Week 9

Temporo-mandibular join t(TMJ): It is the articulation between the temporal

bone and the mandible. It is a bilateral joint. It is the articulation between

the mandible and the cranium .

The TMJ consists of:

1. Condyle

2. Glenoid fossa: A deep concavity in

the temporal bone at the root of the

zygomatic arch that receives the

condyle of the mandible.

3. Articular disc: The disc is thick all around its rim and thin in the center.

thick anterior band (2.0mm thick), intermediate avascular and non-

innervated thin zone (1.0 mm thick).

4. Temporomandibular ligaments: The synovial membrane articular fossa.

Many different mandibular movements occur during:

1. Mastication

2. Speech

3. Swallowing

4. Respiration

5. Facial expression

6. Parafunctional movements bruxism

These mandibular movements should be understood:

1. To understand various aspects of occlusion.

2. To arrange artificial teeth properly.

3. To select and adjust recording devices and articulators.


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Basic Mandibular Movements

Understanding mandibular movements is of great importance in complete

denture occlusion and service when balanced occlusion with cuspid or noncuspid

teeth is desirable. The starting position is the centric relation from which the

mandible can move into:

1. Opening and Closing

From a position of centric relation, pure

hinge movements are possible in opening

and closing. In a hinge movement, the

condyles rotate within the glenoid fossa.

It is the opening movement of the mandible from the habitual intercuspal

position to maximum opening of the jaws. It can be divided into:

a. Pure Terminal Hinge Movement: The mandible will open along the hinge axis.

With the condyles rotating within the glenoid fossa. The rotational movement

will terminate at the Terminal Hinge Axis Position. It occurs at the lower

compartment.

b. Translatory Opening Movement: The opening that occurs beyond the

terminal hinge opening. to the maximum opening position. The condyles

translate downward and forward from their most posterior position. It occurs at

the upper compartment.

Opening and closing movements, where the measured distance between

maxillary and mandibular incisors is between 20-25mm and is called rotation

,more than 25mm, result in combined rotation and translation of the condyles.

(Rotational movement=hinge movement) Translation occurs whenever a

condyle leaves the glenoid fossa.


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2. Protrusion and Retrusion

Protrusion is when the mandible moves forward and both condyles leave their

respective fossae and move down their eminences. The opposite process is called

Retrusion. Protrusion and retrusion are translatory movement. Protrusive

Movement the incline of the articular eminence Occurs while incising and grasping

food.

3. Lateral movement (right and left direction)

When the mandible moves laterally. one condyle moves forward and inward,

while the other condyle) will shift slightly in a lateroposterior (or rotate in vertical

axis) direction:

a.The side to which the mandible is moving is called the

working side.

b.The side that is opposite to the working side is called

balancing or non working side.


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Types of mandibular movement

A. ROTATIONAL: when an opening of 20-25mm measured at the central incisors.

1-Horizontal axis of rotation (HINGE AXIS)

Hinge axis:-defined as an imaginary line passsing through the two mandibular

condyles around which the mandible rotates without translatory movement.

This line stable, recordable, reproducible and repeatable

2-Around vertical axis (frontal)

3-Around sagittal axis

B-Translational movement: if the opening of the mandible continues beyond 20-

25mm then translation of the mandible occurred. The condyle and articular disc

leave glenoid fossa anteriorly.


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C. Bennett’s movements

(Laterotrusion) It is the lateral bodily shift of the mandible during lateral

excursive movement on the working side. ( at the working side in the previous

resulting from movements of the condyles along the lateral inclines of the

mandibular fossae in lateral jaw movement.


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Compensating curve Week 10

The determination of the occlusal plane is one of the most important

steps in prosthodontic rehabilitation of edentulous patients. The position of

the occlusal plane forms the basis for ideal tooth arrangement.

The three dimensional arrangements of dental cusps and incisal edges

in the natural human dentition are classically described as spherical, with the

occlusal surfaces of all teeth touching a segment of the surface of a sphere,

called the curve of Monson. It is divided into an anteroposterior curve called

the curve of Spee and a mediolateral curve called the curve of Wilson.

Reestablishment of these curves of natural dentition is essential during

rehabilitation of a patient in prosthodontics. Replacement of natural occlusal

curves with artificial teeth are collectively known as compensating curves.

Compensating curve: The anteroposterior curving (in the median plane) and

the mediolateral curving (in the frontal plane) within the alignment of the

occluding surfaces and incisal edges of artificial teeth that is used to develop

balanced occlusion.


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The arc introduced in the construction of complete removable dental

prostheses to compensate for the opening influences produced by the

condylar and incisal guidance’s during lateral and protrusive mandibular.

Compensating Curves artificial curves introduced into complete denture

occlusion to achieve balanced occlusion.

* It is incorporated into artificial occlusion raising the distal portions of first

and second molars to conform to a curve. This curve compensates for the

christensen’s phenomenon. The curve is obtained by tilting the upper molars

such that the buccal cusps are higher than the palatal cusps. Consequently,

the lower molars are tilted lingually. It compensates for wedge like opening

formed in nonworking side when the mandible is moved laterally.

*The primary function thus of compensating curve is to provide balancing

contacts for protrusive mandibular movements.

Types of compensating curves

Anterioposterior: ( Curve of spee )

Mediolateral: (Wilson’s curve)


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Curve of spee

The anatomical curve established by the occlusal alignment of the

teeth, as projected onto the median plane, beginning with the cusp tip of the

mandibular canine and following the buccal cusp tips of the premolar and

molar teeth, continuing through the anterior border of the mandibular

ramus and ending at the anterior aspect of the mandibular condyle

Curve of wilson

In the theory that occlusion should be spherical, the curvature of the

cusps as projected on the frontal plane expressed in both arches; the curve

in the mandibular arch being concave and the one in the maxillary arch being

convex. The curve of Wilson also permits lateral mandibular excursions free

from posterior interferences.


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The curve of Wilson results from lingual inclination of the mandibular

posterior teeth, making the lingual cusps lower than buccal cusps on the

mandibular arch; the buccal cusps are higher than palatal cusps on the

maxillary arch because of the buccal inclination of maxillary posterior teeth.


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Arrangement of the artificial teeth (Class I) week 11

It’s the placement of the teeth on a denture with definite objective in mind or it’s the setting of teeth on temporary bases.

Guide lines of arrangement artificial teeth

Maxillary cast

1. A line is drawn parallel to the frontal plane that through the incisive papilla aids in the positioning of the upper central incisors.

2. The midline follows the mid palatal suture and bisects the incisive papilla this line is perpendicular to line 1.

3. The canine eminence line is recorded on the cast when its present.

Mandibular cast

1. A line is drawn parallel to the frontal plane bisecting the residual ridge aids in positioning of the mandibular central incisors.

2. A point designates the distal of the mandibular canine.

3. A line follow the crest of the residual ridge from the canine point to the middle of the retromolar pad aids in the buccolingual position of the mandibular posterior teeth.

4. A line that bisects the vertical height of the retromolar pad aids in establishing the vertical position of the occlusal surfaces of the posterior teeth.

Arrangement of anterior teeth

The anterior teeth should be arranged to provide:

1. Proper lip support

2. Permit satisfactory phonetic 3. Pleasing esthetic


2

A. arrangement of the upper anterior teeth

1. Upper central incisor

-In the frontal view: the contact points

between right and left central incisors

should coincide with the midline of the

cast. The incisal edge of each one should

touch the occlusal plane. The long axis is perpendicular to the occlusal plane.

-In the sagittal view: should have slight labial inclination

-In the occlusal plane (horizontal): The two central incisors should be placed to give

the beginning of the curvature of the

arch. Generally, the labial surfaces of the

two central incisors will be 8-10 mm

anterior to the center of incisive papilla.

2. Upper lateral incisor

-In frontal view: The incisal edge is 1 mm above the occlusal plane and the long axis

show little distal inclination.

-In the sagittal view: The upper lateral incisor should have slight labial inclination.

-In the horizontal view: The cervical area is depressed more than the central incisors

and the distal edge should be rotated to form the arch curvature.

3. Upper canine:

-In frontal view: The tip of the canine should touch the occlusal plane and the

long axis is perpendicular to the plane.

-In the sagittal view: The long axis is vertical.

-In the horizontal view: The upper canine represents the

upper corner of the mouth and the turning point of upper

arch also it forms the transition from the anterior teeth to

posterior teeth.


3

B. Arrangement of the lower anterior teeth

1. Lower central incisor

-In frontal view: The long axis is vertical and the midline of

the lower centrals should coincide with the maxillary mid

line.

-In sagittal view: should have slight labial inclination. The incisal edge should have

1 mm of vertical overlap (overbite) and 1mm of horizontal overlap (overjet) in

respect to maxillary central incisor.

Overbite (vertical overlap): It is the extension of the upper

anterior teeth over the lower teeth in a vertical direction

when the opposing posterior teeth are in contact in centric

occlusion.

Overjet (horizontal overlap): It is the projection of upper

anterior teeth beyond their antagonists in a horizontal

direction.

2. Lower lateral inciso:

- In frontal view: The long axis has slight distal inclination to the occlusal plane.

- In sagittal view: Is fairly upright and the incisal edge should be 1 mm of horizontal

and vertical overlap in respect to central incisor.

-In horizontal view: The distal edge rotated lingually to have the arch curvature

3. Lower canine:

-In frontal view: The long axis has slight distal inclination

and the tip of lower canine should be placed in the

embrasure between upper lateral and upper canine.

- In sagittal view: The long axis has slight lingual

inclination.

- In horizontal view: The cervical area is prominent.


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*The arrangement of anterior teeth should follow the form of the arch which

is either square, tapered or ovoid.

** Lower anterior teeth should be positioned to create an arbitrary 1-2mm overjet

and Overbite where possible.

Arrangement of the posterior teeth

Correct placement of posterior teeth is important for the retention and stability of

both dentures. In arrangement of the posterior teeth we must understand and

applied the Compensating curve (Curve of spee and Curve of Wilson) which is

related to posterior teeth arrangement.

1. Arrangement of maxillary posterior teeth

a. Maxillary premolars

1. Premolars are set vertically to occlusal.

2. Buccal cusp of maxillary 1st premolar touch the occlusal plane while the palatal

cusp is raised from occlusal plane approximately 0.5 mm.

3. Buccal and palatal cusp of maxillary 2nd premolar touch the occlusal plane.

4. The buccal cusp of maxillary 1st premolar

should be seat into the embrasure between

the mandibular 1st and 2nd premolars.

5. palatal cusp should be over the crest of the

ridge.

b. Maxillary molars

1. The inclination of maxillary molars are mesially and slightly palatally.

2. Mesiopalatal cusp of maxillary 1st molar should touch the occlusal plane and the

lingual cusps are over the crest of the mandibular ridge.

3. The mesiobuccal cusp of upper 1st molar should rest in the buccal groove

of the lower 1st molar, and the Mesiopalatal cusp should seat into the central


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fossa of lower 1st molar.

4. Maxillary 2nd molar is set with no cusp touches the

occlusal plane. All the

palatal cusps are over the crest of the mandibular

ridge.

5. Buccal cusps of maxillary teeth form a gentle curve,

while the palatal cusps form a similar curve about 0,5

mm below the buccal cusps.

2. Arrangement of the lower posterior teeth

The lower posterior teeth will be arranged before the upper posterior

because there are more anatomical landmarks

to locate the guide lines a

1. The Mandibular 1st molar is first set into

centric occlusion.

2. Mesio-buccal cusp of maxillary 1st molar fit

into the buccal groove of mandibular first

molar.

3. The mesiolingual cusp of Mandibular 1st molar fit into the central fossa of the

maxillary first molar.

4. Set the mandibular 2nd molar the mesio-buccal cusp of maxillary 2nd molar

fit in to the buccal groove of mandibular 2nd molar.

5. Then set mandibular 2nd premolar, its cusp tip should be positioned in the

embrasure between maxillary 1st and 2nd premolars.

6. The last tooth are mandibular 1st premolar which should be position in the

embrasure between maxillary canine and maxillary 1st premolar.

7. Mandibular premolars follow the curvature of the canine.

8. Mandibular posterior teeth are set on or slightly lingual to the crest of the

ridge.


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Arrangement of artificial teeth (class II) week 12

Criteria of class II

The overjet increases up to 5 mm.

The stability of the denture base supported by

such a ridge is a primary concern in the class-2

patient because the lower ridge is already

compromised in size, compared with the upper

ridge.

In the class-II relation the lower ridge is smaller & markedly lingual in relation

to the upper ridge.

One must not attempt to place the teeth more labially as this may cause

instability of the denture.

The anterior teeth exhibit a pronounced horizontal overlap when they are

arranged properly for esthetics. The vertical overlap should be kept as small as

esthetics and phonetics will allow in order to establish and incisal guidance as

shallow as possible. Class-II problems can be due to insufficient growth of the

lower jaw, an over growth of the upper jaw, or a combination of the two. Class-II

problems are treated via growth redirection to bring the upper and lower teeth

and jaw into harmony.


2

Features of the class-II arrangement

1. A pronounced horizontal overlap.

2. Canine relation more posterior and lingual when compared to that of class-

I relationship.

3. Because of the reduced space on the lower ridge, the premolars may be

ground mesiodistally or one premolar on either side may be removed

entirely.

4. Nonanatomic teeth or teeth with shallow inclines are selected to reduce the

stress on the weaker.

5. The buccal cusp of the upper and lower premolars are flattened to provide a

stable centric occlusal contact.

6. The molars are not affected much usually and the normal functional and

nonfunctional cusp relations are maintained.

Maxillary Protrusion Problems Faced & Arrangement of Teeth

A) Changes in anterior arrangement

1) Increased over jet: Due to maxillary prognathism, there will be increased overjet.

It leads to abnormal upper and lower canine tooth relationship. No attempt should

be made to reduce it by moving upper teeth palatally or lower teeth labially.


3

2) Changes in canine relationship: Normally, the distal surface of lower canine tooth

(located at) tip of the cusp of upper canine, whereas in maxillary prognathism it

leads to the lower canine tooth finishing anywhere from the tip to distal surface of

upper canine. Excessive prognathism leads to distal incline of cusp of lower canine

posterior to distal surface of upper canine tooth.

Setting Upper Posterior Teeth in Class-II Relation

Upper first premolar setting

If necessary, the palatal cusps of the 1st premolar is flattened.

This is done to get good intercuspation with lower premolar.

Upper second premolar setting

Upper 2nd premolar is set with its flattened lingual cusp occluding with the

flattened buccal cusp of the lower second premolar.

There is less buccal overlap and a larger area of contact is possible between

this teeth.

Setting upper molars

Upper molars are set in normal relation as done in (class I) teeth

arrangement.

Setting Lower Anterior Teeth in Class 2 Relation

Lower anteriors are set according to normal principles. The overbite is maintained

at 2mm. However, there will be increased overjet (4-5mm).


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Setting of Lower Posteriors

The lower first molar in Class I relation. (Key of Occlusion).

The remaining space for premolar is assessed. Usually there will be space for

only 1 premolar. The lower premolar is set in the remaining space. The buccal

cusp of lower premolar occludes with the palatal cusp of upper second

premolar.

The lower second molar is set in normal relation with the upper second

molar.


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Criteria of Class III relationship week 13

This is an anterior relationship of the mandible

to the maxilla.

In natural teeth the mesiobuccal cusp of the

upper first permanent molar occludes distal to

the mesiobuccal groove of the lower first

permanent molar.

In class III complete denture cases, the lower arch is usually wider than the upper

arch because of the anterior relationship of the mandible to the maxilla.

In complete denture class Ill cases a normal

relationship between the posterior teeth is

maintained (if there is no crossbite).

However, a crossbite situation frequently occurs in

this classification. When crossbites occur, the buccal

cusps of the upper teeth are used to occlude with

the central fossae of the lower teeth.

Types of class III crossbite

1. Unilateral cross bite: one side posteriorly (either left

or right).

2. Bilateral cross bite: both sides without anterion

crossbite due to atrophy of maxillary arch, the lower

arch larger than upper (usually cross bite begin at 2nd

premolar region).


2

3. Bilateral cross bite include an anterior cross bite (due

to over growth of mandible in comparison with

maxilla).

Problems associated with class III arrangement

1. The relation between the ridges may vary from edge to edge relationship to

extreme prognathism of the lower arch.

2. Wider lower arch leads to problems in selecting the size of the teeth as

selecting the same mold size for both arches leads to spacing between lower

anterior teeth which reduce aesthetics.

3. The Crest of the lower arch is located further buccally than that of the upper

one, leading to problems in obtaining an adequate occlusal relation between

upper and lower teeth.

Anterior teeth arrangement:

1. Edge to edge relationship

2. Inclining the mandibular anteriors lingually as possible without encroaching

the tongue space.

3. Inclining the maxillary anteriors more anterior to the crest of the ridge than

usual, with their incisal edges being inclined more.

4. Addition of lower lateral or central incisor. It is better to have seven

proportionally matching teeth than to place six larger teeth.

5. Wider lower anteriors.

6. Slight crowding in upper anteriors.


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Posterior teeth arrangement:

1. Monoplane posterior teeth or cuspless teeth (preferred)

2. Upper posterior teeth can be placed slightly buccal to the crest of the upper

ridge.

3. Cross-bite is accomplished to avoid unfavorable leverage that compromises

denture stability

4. Larger sized upper posteriors + Medium sized lower posteriors

Common errors in arrangement of teeth

1- Setting mandibular anterior teeth too forward in order to meet maxillary

teeth (in class II).

2- Failure to make the canine turning point of the arch.

3- Failure to establish the occlusal plane at the proper level and inclination.

4- Establishing the occlusal plane by an arbitrary line on the face.

5- Lack of rotation of anterior teeth to give a narrower effect.

6- Setting the mandibular posterior teeth too far to the lingual side in the 2nd

molar region which cause tongue interference and mandibular denture

displacement.


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Week 14

Waxing: It is the contouring of the wax base of trial denture into the desired form.

Festooning: Is the process of carving the denture base to simulate the contour of the natural tissues which are being replaced by the denture.

Objective to:

1. Produce natural contour and aid in retention.

2. Restore the anatomy of that which is missing.

3. The entire size, shape and contour of upper and lower denture.

Polished surface: The outer surfaces which will be in contact with oral tissues and developed by contouring the wax.

The form of polished surface of a denture influences its: 1- Retention and stability of the denture. 2- Esthetic values of the denture: the esthetic of complete denture is not related to arrangement of teeth alone, we attempt to simulate natural anatomy of patient mouth which include size, shape, and contour of missing oral tissues during construction of complete upper and lower dentures. 3- Tissue tolerance of the denture. There are three principal surfaces concerned in functional stability of the denture 1- The basal or impression surface. 2- The leverage position and occlusal surfaces of the teeth. 3- The location and form of the polished surfaces.

The polished surface is determined by: 1- The width of the border of the denture. 2- The buccolingual position of the teeth. 3- The fullness given to the wax to obtain convexity or concavity both facially and lingually.


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The inclined plane action of the muscles of the check and tongue, this horizontal force exert in the direction of the occlusal plane by the tongue and cheek can act either a placing or displacing agent, depending on the shape of the polished surface. When the lingual and buccal borders of a mandibular denture are being shaped, they can be made concave so that the tongue and cheek will grip and tend to seat the denture. In the opposite case where the lingual and the buccal surfaces are made convex by waxing and a narrow impression base used, the inclined plane forces resulting from pressures of the tongue and cheeks will tend to unseat the denture. The buccolingual position of the teeth is important because a buccal position of the teeth would necessity shaping the surface of the denture base in such a manner that the muscle action of the cheeks would tend to unseat the mandibular denture. Requirements of waxing the polished surface 1- They should duplicate the covered soft tissues as accurately as possible realistic, not exaggerated. 2- The borders, both labial and buccal should full the vestibules. 3- Notches should be provided to accommodate the mucous membrane attachment (frenum), both in size and direction. 4- The contour of the facial flanges should be compatible with the cheek and lips. 5- The contour of the lingual flanges should be compatible with the tongue. 6- The palatal section of the maxillary denture should be nearly a reproduction of the patient palate and rugae. 7- Avoid a bulky wax-up. The additional bulk of acrylic resin may contribute to porosity and dimensional processing error.

The procedure of waxing

Contour the wax carefully to prevent movement of teeth. Avoid a bulky wax-up. The additional bulk of acrylic resin may contribute to porosity and dimensional processing error. Place strips of base plate wax along the facial surface of the trail denture so that they extend from the gingival third of the teeth to the edge of the cast. With a hot spatula lute the strips to the underlying wax at ¼ inch intervals, and melt the wax into contact with the necks of the teeth.


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After the wax has cooled, carve the interdental papillae. They vary with the age of patient. Develop the margin by the carving with a lacron carver at 45º angle to the neck of the teeth. The posterior area should have a marked fullness. Wax the lingual flange of the mandible denture thickly enough to full all depressions and to slop down from the necks of the teeth and inward toward the tongue. The slop of the flange should be free from the undercuts and very slightly concave at or near the lower border.

Contour the wax around the necks of the maxillary posterior artificial teeth to form part of clinical crowns and to make these teeth more natural in size and more compatible to the toungue the palatal surface of maxillary denture should be waxed to a uniform thickness of 2.5mm, when the processed resin is smoothed and polished, the palate will be as thin as possible and yet sufficiently thick to provide adequate strength.

Stippling of the wax: an alternative to gingival contouring some people stipple the wax and this procedure a finished denture, whose surface shows an (orange-peal) effect, produces a very pleasing result. This may be produced by tapping the surface of the wax with a bristles of a tooth brush after first warming the surface soften the wax or by running over the surface of the wax with a small burnishing bur rotating in a hand piece.

Disadvantages of stippling is that it produced a denture which is more liable to contamination by calculus deposits. If it done it should be confined to the area of the denture which can be seen when the patient grains broadly. After the wax has been contoured, smooth it by flaming and then polished it with we cotton.


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Establishing the posterior palatal seal Posterior palatal seal area: it is the soft tissues along the junction of the movable and non-movable part of the soft palates on which pressure within physiologic limits of the tissues can be applied by a denture to aid in the retention of the denture. The posterior border of the denture is determined in the mouth and its location is transferred onto the cast. The locations of right and left hamular notches are marked with an indelible pencil. Then the location of fovea palatinae near the median palat suture is marked. The vibrating line of the soft palate normally used as a guide to the ideal posterior border of the denture, it may be slightly posterior to the fovea palatinae.

Procedure for carving of posterior palat seal area a V-shaped groove (1-1.5) mm deep is carved into the cast at the location of the bead. A large sharp scraper is used to carve it passing through the hamular notches and cross the palate of the cast. The groove will form a bead on the denture that provides the posterior palatal seal area (pps). The bead will be 1-1.5mm high and 1.5 wide at its base.

Advantages of posterior palatal seal

1. its helps to determine the posterior border of maxillary denture.

2. It helps to compensate for the shrinkage of the acrylic resin in this area during processing.

3. Provide a good seal in the posterior area of the maxillary arch which increase retention.

4. It prevents food to enter under the maxillary denture.

5. Reduces the tendency for gag reflex.


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Flasking

is the process of investing the cast with the waxed denture in a flask to make a sectional mold that is used to form the acrylic resin denture base. Therefore it is also known as investing.

Components of a Flask

The flask is a metallic mold that supports the models and the try in denture during the flasking procedure.

It is composed of 3 parts:

1. The base in which the model & the try-in denture will be placed.

2. The mid-part in which the teeth will be located. 3. The cover

Flasking Procedure

1. Flask must close fully and accurately without resistance. If a flask fails to do this, air-blows, distortion or excess increase in vertical dimension may occur.

2. The model with the sealed try in denture must be covered with very thin layer of Vaseline.

3. Any undercut should be covered by wax. 4. All parts of the flask must be clean and covered by thin layer of Vaseline from

inside. 5. Models with the sealed (try in) are to be placed

in cold water for 10 min. before flasking. 6. Thin mixture of Plaster poured in the base of

the flask, place the model, teeth should be vertical.

7. All the parts of the model should be covered with Plaster and all the wax and teeth must be uncovered.


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8. After setting of Plaster cover it by thin layer of cold mold seal or Vaseline. 9. Prepare a mixture of gypsum, put the mid part in its correct place and pour

the gypsum. 10. Fill the flask with gypsum, cover it, put the flask under mild pressure to

prevent gypsum from expanding, wait for complete setting.

Wax Elimination Procedure

1. After setting of gypsum, wax elimination procedure is to be done.

2. Put the flask in boiling water for 5-7 minutes. 3. Separate the 2 parts of the flask. 4. Remove the shellac base plate and the wax using

the boiled water and detergent. 5. Place the clean flask in open air to dry and cool it.

*Note: Remove all wax residue since acrylic resin will not adhere to a surface coated with wax. Any residual wax will contaminate the acrylic resin and prevent bonding between teeth and the denture base.

Packing of acrylic

It is the procedure of application of acrylic resin into the mold and pressing the flask by using sufficient pressure to compensate for the contraction of the acrylic after polymerization to prevent shrinkage and porosity.

Acrylic Packing Procedure

1. Isolate the gypsum of the flasking by using one of these systems of isolation:

Physical separator or isolator: tin foil.

Chemical isolator: solution of alginate (cold mold seal). It reacts with the calcium of the gypsum to form a film of insoluble calcium alginate.

2. Use the brush, move it in one direction to spread the cold mold seal.

3. The cold mold seal should be thin and even on all the parts of the mold except the teeth which should not be separated. If the teeth covered by cold mold seal, they will not adhere to the denture base.


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4. Mixing: Acrylic resin is a resinous plastic material of various esters of acrylic acid. It is used as a denture base material. It is formed of a powder and liquid.

Powder: polymethyl methacrylate PMMA (polymer) + Benzoyl peroxide (initiator) +pigments.

Liquid: methyl methacrylate (monomer) + hydroquinone (inhibitor)

Powder and liquid are mixed in a ratio of 3 to 1 by volume for an average sized denture.

5. Put dough acrylic in the mold, press in a clamp, do curing immediately.

Note: *Too early– ( Sandy Stage) – acrylic resin has too low viscosity to densely fill the mold. Results in porosity in the final prosthesis.

** Too late– ( Rubber Stage) – inability to close the flask, loss of detail and increase in vertical dimension of occlusion in final prosthesis, as well as, movement and/or fracture of teeth.

Curing of Acrylic

The packed mold is heated (cured) in an oven or in water bath. Temperature and time should be controlled.

Two water bath heating techniques may be used:

a) Heating the flask in a special bath of water, beginning from the room temperature until reaching 72°C for 16 hours.

b) Heating the flask in an ordinary water bath beginning from the room temperature, until reaching 72°C, lasting for 2 hours, then the temperature is raised to boiling for another 1 hour.

This technique takes shorter time but there is a likelihood to be distorted during de-flasking. Also, the free monomer is more.


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Cooling of the flask / Bench Cooling

After curing, the flask is to be cooled slowly on the bench in its water bath.The slow cooling will permit the relief of the internal stresses caused by the difference in contraction between the acrylic and the mold material.

De-flasking Procedure

It is the procedure of opening the flask after curing of acrylic resin. It should be done carefully to prevent the breakage of the denture.

It includes the following steps:

Remove the flask from the clamp.

Remove the upper and lower lids.

Separate the 2 parts of the flask with attention using the plaster knife.

Liberate the denture with its model, then try to remove the model carefully. If there is undercut, split the model into 2 or 3 parts to remove them easily.

After gaining the denture, remove the excess of acrylic using the acrylic bur.


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Finishing and Polishing

Is the process of perfecting the final form

of the denture by removing any flash, plaster

remaining around the teeth, and any nodules of

acrylic resin on the surfaces of the denture base

resulting from processing.

Flash: It is the excess of acrylic resin at the denture border, the acrylic resin that

was forced out between the two halves of the flask by

the pressure applied during the processing

procedure.

Finishing procedure

Take care to preserve the border and contour of the

denture during the finishing process. If the impression was correcting molded and

boxed, and the trial denture was carefully waxed contoured into the form desired

in the finished denture, little finishing will be necessary.

1. Carefully remove remaining plaster around the neck

of teeth with a small sharp knife.

2. To remove the flash of acrylic resin from the

denture border, use a large acrylic bur or stone bur

mounted in a straight hand piece to remove the

flash. Take care not to change the form of the

denture border but only remove the excess resin on the border of denture.

3. Remove nodules of acrylic with small stone or

acrylic carbide burs.

4. The posterior area of the palate has been

thinned to its proper thickness.

5. Smoothing the denture with sand paper (used

mandrel) with low speed hand piece.


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Polishing: is a process of removing scratches. Polishing consists of making the

dentures smooth and glossy without changing the contours.

Principles of polishing

1- The tissue surface of a denture is never polished as a polishing destroys the details

necessary for good fit and retention.

2- The polished surface extends just over the border, but the borders are not

reduced in height and width during polishing.

3- Care must be taken when using pumice (it should be used as wet slurry) as this

material is very abrasive and may obliterate the details placed on the denture

when they were waxes (festooned).

4- Resin teeth have approximately the same hardness as the denture base, so

polishing a denture with resin teeth requires some precautions not necessary with

porcelain teeth.

5- When polishing, only the denture base and not the teeth are polished.

6- During the finishing and polishing we should minimize the reduction of bulk

because this cause warpage.


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Procedure of polishing

1. Polish labial, buccal, lingual, and palatal external surfaces of the denture with wet

pumice on rag wheel attached to dental lathe running at slow speed. Keep plenty

of pumice on the denture surface and keep the

denture moving at all times; press the denture

lightly against the wheel.

2. Polish acrylic around the teeth with wet pumice

and a brush wheel attached to dental lathe

moving at slow speed. Be careful not remove

previously developed contours.

3. Polish the border, lateral and palatal surfaces of denture by using wet buffing

wheel attached to dental lathe.

4. Use Rouge (greasy material) this material is applied to dry muslin buffing wheel,

this differ in that the polishing compound is applied to the wheel not as pumice

to the piece of work being polished. After the denture completely polished with

rouge, it is scrubbed thoroughly.

5. Final polish is obtained by placing high shine material on the denture. Store the

polished dentures in water until they have been delivered to the patient.

6. Store the dentures in water all the times otherwise they will undergo dimensional

changes and shrinkage.


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Relining: It is the procedures used to resurface the tissue-side of a denture with

new material layer, thus producing an accurate adaptation to the denture

foundation area.

It is usually carried out when the fitness of the denture has been deteriorated and

it is not necessary to construct a new one. The jaw relation should maintain intact

with vertical dimension.

Rebasing: Is the process of refitting a denture by

the replacement of the denture base material. Is

the process of replacing the entire denture base

material on an existing prosthesis. Only the

original teeth and their arrangement remain.

The main objectives of relining or rebasing

1. Reestablish the correct relation of the denture to basal tissue.

2. Restore lost occlusal and maxilla-mandibular relationship.

3. Restore stability and retention.

Indication for rebasing and relining

1. Patient with immediate denture (3-6month) following the replacement of an

immediate denture.

2. Patient with poor retention and stability due to resorption of the supporting

tissue When the residual alveolar ridge has resorped and the adaptation of the

denture bases to the ridges.

3. poor Chronically ill patient.

4. Porous denture or discolored.

5. Poor occlusal relationship with opposite arch.

6. If the patient cannot afford the cost to having new dentures.


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Contra indication

1. If the dentures have poor esthetic or unsatisfactory jaw relationship.

2. When an excessive amount of resorption has taken place making it difficult to

Position the denture properly on the ridge.

3. If the dentures create a major Speech problem due to in correct vertical

dimension.

4. When abused soft tissue are present. The relining is delayed until the tissues

recover and return as closely as possible to normal form.

Advantage of the reline and rebasing

1-Economical for the patient.

2-Improve fit of the denture

Disadvantage

1. Cannot correct occlusal or jaw relation.

2. Cannot correct occlusal arrangement.

3. Cannot be used when excessive resorption has occurred.

4. Likelihood of altering the jaw relationship during the process.

Materials used in relining and rebasing

1-PMMA Heat cured acrylic resin. Cold cured acrylic resin.

2-Modification of PMMA. -Butyl meth acrylate.

3-Soft liners\tissue conditioners.

Procedure of relining

There are two methods for relining

1. Direct (chair side): its done inside clinic by cold cure acrylic.

2. In direct (laboratory).


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Procedure of indirect relining

1. The fitting surface is cleaned, the undercuts are removed and the flanges are

shortened.

2. Minor defects and extensions can be corrected.

3. A wash impression by zinc oxide eugenol is making with the old denture, with

the patient in light occlusal contact……..(This three steps done inside clinic)

Labrotory work

1. The denture and the cast are not

separated, but any excess

impression on the teeth or facial

surfaces of the base is removed,

then the denture flasked in the usual

manner.

2. Beading and boxing of the

impression, then pouring the boxed

impression with stone material.

3. (Zinc oxide eugenol) elimination in hot water for 5 minutes; then separated and

all the impression material is cleaned from the cast and the denture base.

4. Painting the cast with a separating medium.

5. Paint the surface of the denture with cotton pellet moistened with monomer.

6. Mix the heat acrylic resin and place it in the flask (the new relining material

should be compatible with the old denture base material chemically and

esthetically).

7. Curing the heat cured resin.

8. The denture deflasked and the cast removed from the denture then finish and

polish the denture; the relined denture is ready to be inserted in the patient mouth.


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Rebasing procedure

Rebasing procedure is the same as those for relining with some differences:

1. Impression is made and a cast is poured in the denture as in relining procedure.

2. The denture with the cast is mounted on an instrument as Hooper duplicator or

Hanau articulator with mounting jig that maintains the relationship of teeth to the

cast.

3. The old denture base is cut and removed.

4. The original teeth are re-waxed in their previous positions on the cast.

5. The denture is then processed in the laboratory as for relining.

6 The denture deflasked and the cast removed from the denture then finished and

polish the denture; the rebased denture is ready to be inserted in the patient

mouth.

Assist.lec. Ahmed Basim Complete Denture 3rd Year 1

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