VII. Aesthetic requirements for the arrangement of artificial teeth for complete dentures. Cross bite, prognathic and progenic arrangement. VIII. Waxing, flasking, polymerization, cleaning and polishing of the complete dentures.

Aesthetic requirements for the arrangement of artificial teeth for complete

dentures.

• Gerber's (1979) minimum requirements for complete dentures must be met when arranging artificial teeth. They are as follows: "Complete dentures should restore the facial appearance with a personalized and natural look."

• "Complete dentures should preserve the residual tissue structures of the gnathodynamic system."

• "Complete dentures should attempt to ensure adequate masticatory function and enhance clear phonation."

In keeping with Gerber’s requirements, the aesthetic components of the anterior tooth arrangement must not be dissonant with a

patient’s facial appearance.

• Establishing maxillary anterior tooth width can be aided by observing the relative widths of the base (ala) and the bridge of the nose. For tooth selection that is harmonious with a patient’s facial appearance, the incisal width of the central incisor should reflect the width of the base of the nose, and the width of the lateral incisor should reflect the width of the bridge of the nose. That is, when the base of the nose is wide, the width of the maxillary central incisor should be wide. If the bridge of the nose is narrow, the lateral incisors should be narrow.

Selecting Tooth Forms

face with square forms

face with tapered forms

face with oval forms

in harmony with facial forms:

•Square face with square forms

•Oval face with oval forms

•Triangular face with tapered forms

Sagittal and frontal considerations

• The incisive papilla is an invaluable reference point for correct placement of the maxillary anterior teeth and the anterior arch form. The maxillary anterior teeth lie to the facial of the incisive papilla. In the young, the line connecting the tips of the canines transverses the incisive papilla. As the alveolar ridge is increasingly resorbed with increasing years since loss of the teeth, the line moves posteriorly and may eventually pass through the posteriorly extent of the papilla.

• The distance from the middle of the

incisive papilla to the labial surface of the

maxillary central incisor is typically 8

mm. Because this distance is fixed, the

apparent curvature of the anterior arch

form will increase as a person

experiences more alveolar ridge

resorption.

• The labial surface of the canine is

normally 10.5 mm from the lateral aspect

of the anterior rugae.

• The distance between the tips of the canines is the same as the width of the base of the nose.

• Canines are immediately inferior to the side of the nose. They must not be positioned directly at the corners of the mouth when the patient smiles, so the "buccal corridor"—the facial surfaces of the premolars and first molar—can be visualized between the cuspid and the corners of the mouth.

• The width of the central incisor approximates the width of the philtrum.

• First premolars appear at the head of the "buccal corridor" and behind the canine.

Tips of canines = width of nose

Width of centrals = width of

philtrum

• Selecting Tooth Shade, Form, and Alignment

• Selecting tooth shade, form, and alignment is best accomplished prior to setting posterior teeth. Once the anterior teeth have been selected and set, the dentist needs to evaluate the midline in the mouth to ensure acceptable tooth placement.

• The Smile Line Once the midline is established as correct, the length, contour, and position of the incisal edges can be checked. The final evaluation of the anterior arrangement, which will include the gingival contours and margins, will be completed at the last try-in.

• Final evaluation at last try-in In this example, the central incisors appear too short and the canines appear too long.

Orthognathic ratio in the side sections

Medio-posterior shortening of the upper dentition

In retainer upper alveolar ridge-Pelo Weights and

order at the front

Maxillary progeny Malocclusion I

1. Overdeveloped frontal area of the

upper jaw.

2. Highly protruding upper lip

3. Positive lip scale

• Arrangement of the upper teeth

• “ Midline”,

• Anterior elliptic curve

• Bilaterally symmetrical arrangement of

the masticatory teeth,

• Functional masticatory center

• Pillars of the tooth rows

Upper anterior teeth – most Inside, advocated crest of the alveolar ridge OPISTOGNATIC SLOPE

LOWER frontal teeth – from out to the contact with lingual canine surfaces.

HORIZONTAL plane- behind the lingual slope of the upper canines

Not required contact between the front teeth - canines

overdeveloped and protruding lower jaw

1. Overdeveloped frontal area of the mandible.

2. HIGHLY protruding lower lip

3. NEGATIVE ORAL tiered ladder

Progeny of Mandible Malocclusion III

Retention prosthetic area

bilaterally

Remove retainer part of the tuber maxillae

Weakly and strongly developed

Tuber maxillae

Upper Total Denture

Pterygoid processes

Elastic deformation

• Two stabilization pterygoid tuberoses

• Midline incision of the palate plate

• Power decomposition

• 1-1,5 мм

• Gap between the two pterygoid processes

• Prosthetic edges - retention paratuber space

Slightly developed tuber maxillae

Total denture

Two paratuber plastic pellets

Horizontal positioning as

drawer

Highly developed tuberculosis

Elastic impressions

Extended base - plate

Wax Pelo prototypes

Acrylic resin Denture

Pelo are cut in supra tuber

spaces

Rules

Shape of the alveolar

ridge

Type of the atrophy

Intraalveolar spaces

Border occlusions

Occlusal curves

Interalveolar angle under

80°

Changed interjaw

relationships

Masticatory region is changed

• The frontal teeth have to be ordered

• Bilaterally arrangement of the masticatory teeth

• Lower premolar – antagonists lower first and second premolars are

changed their position

• medial segment on vestibular cusp has to overlap the distal

segment of the lower first premolar

• distal segment must go behind the medial segment of the second

premolar

• all subsequent upper teeth come in masticatory furrow of the ower

their antagonists

• Slightly lowering upper vestibular cusps

Cross – bite arrangement

Unilaterally cross- bite

Exchange of the upper teeth with the lower in one side only has to be done in interalveolar angle below 80 ° unilaterally? On the opposite side -

orthognathic order

LONGITUDINAL CENTRAL

FISSURE OF THE LOWER

TEETH

Upper vestibular cusps

Processing the denture

1) Flasking. 2) Wax

elimination.

3) Mixing. 4 ) Packing and curing

5) De - packing

6) Shaping and

Polishing.

Flask: Is a metal case or tube

used in investing procedures.

The flask is made of 3 major parts, (1) lower half (which contains the cast), (2)

upper half and (3) the cover or lid. The lower half may have a round plate, covering a

round hole in the base of the lower half.

Flasking: The process of investing the cast and a waxed denture in a flask to make a

sectional mould used to form the acrylic resin denture base.

• Molding or flasking Techniques:

• 1- Compression technique:

• The stone cast with the record denture base, wax and teeth are secured to the lower half

of the flask with gypsum investment material (plaster or stone). Then the upper half of the

• flask is put in place and gypsum is poured to the occlusal surfaces of the teeth. Finally the

top portion of the flask is poured with investment and the lid is placed on the flask.

1) Flasking:

• It is a complicated procedure requiring special

flask and equipment. In this technique

• the wax pattern is sprued and the material is

injected into the mold. This process allows

• injection of further material during

polymerization to compensate for the

polymerization

• shrinkage.

2- Injection moulding technique:

The procedure of flasking a denture in compression technique is as follows:

• 1) The master cast and the wax dentures are

placed in the flask, to insure that the cast fit in

the flask.

• 2) The Inner surface of the flask is coated with

Vaseline, while the base of the cast is painted with separating medium (cold mold seal). To prevent the investment material (plaster of Paris) from attaching to the cast.

3) The first layer of gypsum investment is

poured in the lower half and the cast is placed on top of the investment.

• 4) After the set of the first gypsum investment

layer, a plaster separating medium is painted on it, to prevent the sticking of the second layer of gypsum investment to the first layer.

5) A mix of dental stone is placed over the surface of the teeth in

the invested trial denture , which is referred to as coring.

• 6) The upper half of the flask is put in place,

then the second mix of gypsum investment is placed on the first layer and covers the wax, denture base and teeth.

• 7) Before the second layer sets the lid or flask cover is put in place and tapped to sit properly allowing the excess gypsum to flow out of the holes in the lid.

2- Wax elimination:

• After the complete set of the gypsum the flask is

ready for the next step which is "Wax

elimination", in which the flask is placed in

boiling water for 4 to 6 minutes. Then it is

removed from the water and opened. Then the

wax is washed away with boiling water. After

that the mold is washed with boiling water

containing detergent, then finally washing it with

clean boiling water.

2- Wax elimination:

• After the stone of the flask is dry, the inner side of the mold and the cast are painted with a separating medium by a camel's hair brush and allowed to dry. The separating medium must not come in contact with the teeth because wax residue on the teeth is

contaminant and causes adhesion failure with the denture resin. A second layer of separating medium is applied on the inside of the mold and the flask is allowed to cool to room temperature.

3- Mixing:

• Acrylic resin dough is made by mixing the powder (polymer) and liquid (monomer) to form 'dough' which is packed into a gypsum mold for curing. The ratio of powder to liquid is important since it controls the workability of the mix as well as the dimensional changes on setting.

• The mixing should be done in a clean jar which should be covered to prevent evaporation of the monomer.

4- Packing:

• It should be done when the mixture reaches dough stage, as the dough is rolled into a rod-like form and placed in the upper half of the flask then polyethelen (nylon sheet) is placed over the dough in the upper half and then the two halves of the flask are closed until they are almost in approximation, this is done to spread the dough evenly throughout the

• mold.

4- Packing:

• Then the two halves of the flask are separated,

the excess material at the borders of the denture

is removed by a wax knife, and additional resin is

added at any places that are deficient. At least

two trial closures are done and before the final

closure a thin layer separating medium is applied

on the cast and the polyethelen sheet is removed

and then the two halves of the flask are closed

under pressure by bench press of about 100

Kg/cm2. Then the flask is put in a spring clamp

and the clamp is closed tightly.

5- Curing:

• It is polymerization of the hot cure acrylic to produce the final denture. The material is cured by heating in a water bath; pressure is applied during curing for the following reasons:

• 1- To decrease the effect of thermal expansion.

• 2- To decrease the polymerization shrinkage.

• 3- To increase the evaporation of monomer thus decreases porosity.

Types of curing cycles for heat

cure acrylic:

• 1- Short curing cycle: The denture is placed in water at room temperature and the curing temperature is programmed to 74 ° C for one and half hour followed by 100 ° C for one hour.

Types of curing cycles for heat cure

acrylic: • 2- Long curing cycle:

• The curing temperature is programmed to 100 oC for 8 hours. Polymerization can occur at any temperature but it is very slow at temperature below 70oC,the best curing cycle is the long curing cycle because most of the conversion of monomer to

• polymer occurs during the period at 70oC and during this time the dough itself may approach

• 100oC because the polymerization reaction exothermic. The monomer boils at 100.3oC so the

• dough must be kept below this temperature to avoid boiling of the monomer; on the other

• hand rapid curing cycle usually results in some gaseous porosity.

6- Deflasking:

• Deflasking is the process of removal of the processed denture from the flask and investment mold. Before deflasking of the processed denture begins the flask is left to cool to room temperature. If not, increased distortion of the acrylic may occur.

Laboratory remount

• The denture should be remounted on the articulator as dictated by the indices with sticky wax. The incisal pin discrepancy should be noted. If the discrepancy is less than 2mm, it is acceptable. If the discrepancy is between 2-5 mm, occlusal correction can be accomplished.

• If the discrepancy is more than 5mm, the entire treatment should by repeated.

7- Shaping and Polishing:

• In this step any excess acrylic is removed from the processed denture by the use of stone wheel burs, stone burs, and steel burs. Care must be taken not to heat the denture during grinding, because this may cause distortion of the denture base. Finally, the denture should be smooth and clean, as no plaster and no deep scratches should remain after the preparation for polishing.

• In polishing a rag wheel with pumice is used for smoothing the denture. Then a final high

• polish is given to the denture with a rag wheel and polishing material (Rouge).