Denture 2

7/30/2019 Denture 2

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Complete Denture

Impression

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What’s our job?

• Create a 3-Dimensional representation

of the patient’s tissues that the denture

will be sitting on!

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Impression

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What’s our job?

• All tissues in the mouth ?

• Hard - Soft

– Residual ridges - palate - any boney areas ?

– Cheeks - mucosa - tongue - lips ?

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What’s our job?

• All tissues in the mouth ?

• Movable

– Soft palate - frenum - vestibules

– Stretched - at rest - somewhere in between ?

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What’s our job?

• The denture sits on the oral tissue.

• When the denture contacts an opposing

prosthesis - or natural teeth - what

happens to the tissue under thedenture?

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What’s our job?

• What type of tissue would be capable of taking the force? Soft - Hard?

• Big surface area - or small?

• Who cares - we’ll tell the patient to justeat water!

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The amount of biting force an edentulous ridge will tolerate

is directly proportional

to the amount of surface area covered

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Force directed to a large bearing area is more equally

distributed and much less per sq. mm. than the same force

directed against a smaller area.

F F

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Consequently, if we hope to assist a patient to achieve

maximum biting force and preserve the supporting

structure over a longer period of time,

The maximum amount of denture bearing

area must be covered.

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Macroscopically (palate, mandibular ridge)

Microscopically (submucosa)

Are all the tissues the same ?

NO !

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Buccal Shelf

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Impression Retromylohyoid

Space - LateralThroat Form

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Are these tissues all equalin their capability tosupport a denture under

pressure?

NO !

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(1) Primary stress bearing area,

(2) Relief area

(3) Peripheral seal area

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Primary stress bearing area

Best to resist vertical forces of occlusion

Base of cortical bone

Protected by firmly attached epithelial type tissue

Sufficient thickness to form a cushion against the forcesof occlusion.

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Pressure causes discomfort to the patient

Pressure causes instability of the denture base

Relief area

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Peripheral seal area

Soft tissue border areas, which the periphery of thedenture must contact in order for the factors of retention

to be effective.

The peripheral seal area is divided into two parts:

(1) Resistant peripheral area

(2) Nonresistant peripheral area

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Impression Stress

Bearing

Ridge Crest

Lateral Hard Palate

Ridge Crest

Buccal Shelf

Retromolar Pads

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Impression Relief

Areas

Papilla

ZygomaticaSuture

Mylohyoid RidgeMental Foramen

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Impression Resistant Peripheral Areas

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Impression

Hamular Notch Alveolar

Bone

Mucosa

LipTuberosity

Pterygomandibular

Raphe

Hamular Process of theMedial Pterygoid Plate

Resistant Peripheral Areas

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It is imperative that all maxillary denturebases terminate in this notch.

Bases short of the hamular notch will

end on the thin - nonflexible - tissue

of the tuberosity and will

consequently lack retention.


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Impression Non-Resistant Peripheral Areas

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Impression

Alveolar Process

Hard Palate

Posterior Limitof Hard Palate

Soft Palate

Vibrating LineMucosaLabialVestibule

Lip

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Impression

Classifications of Throat Form

CLASS I

6 - 8 mm of soft palate extends beyond the hard

palate before dropping downward or registering

movement when the patient speaks

CLASS II

3 - 4 mm

CLASS III

0 mm

Non-Resistant Peripheral Areas

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Impression

Vibrating LineLip

Non-Resistant Peripheral Areas

CLASS III

For the Class III throat form where the movement of the softpalate starts immediately at the posterior border of the hard

palate, problems may be encountered in establishing a goodseal. 40

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Impression Peripheral Areas


1.Labial frenum

2.Lingual frenum

3.Buccal frenum

4.Distobuccal arch

5.Pterygomandibular raphe

6.Retromylohyoid curtain

7.Alveolo-lingual fold

Nonresistant border areas

8.Labial vestibule

9.Buccal vestibule

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Impression 4.Distobuccal arch




The distobuccal arch is under the control of the masseter musclewhich has its origin at the zygomatic arch. It is attached to thelateral border of the mandibular ramus. Dentures, which areoverextended in this area, interfere with the contraction of themasseter muscle, which pushes forward against the buccinatormuscle creating discomfort when the patient closes. Thedistobuccal arch flange, if properly shaped, will usually run at a45-degree angle from the mesiobuccal arch to the apex of theretromolar pad.

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Posterior Limit of the Lower Denture

The pterygomandibular raphe forms the attachmentof the superior constrictor to the buccinator muscle.It runs from the posterior border of the hamularnotch downward to the apex of the retromolar pad.The raphe stretches when the mouth is opened,pulling the distal edge of the pad upward. Denturesshould not extend beyond this line of movement.

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Distolingual Extension of the Lower Denture

The retromylohyoid curtain lies lingual and inferior to the retromolar

pad. It is formed by the mucous membrane of the lingual lateral border

of the mandible and is attached to the posterior sides of the tongue. Its

size, shape, and position vary with tongue movements. The curtain

moves upward and backward as the tongue moves upward and

backward in swallowing. It moves upward and forward during

protrusive and lateral movements of the tongue. The amount of

upward and forward movement of the curtain during these protrusive

and lateral movements is referred to as the lateral throat form of the

mandibular denture. If this movement is slight and the angle formed by

the posterior part of the curtain to the retromolar pad is approximately

90 degrees, it is a Class I throat form. Extreme forward movement of

the curtain resulting in an angle of 45 degrees or less in Class III throat

form and in between the two is Class II throat from 44

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The amount of posterior lingual extension of the base is controlled by the

movement of this curtain. Overextension of the denture flange results in

the patient complaining of a sore throat or unseating of the denture.

Underextension handicaps the tongue in controlling the lower denture

and allows ingress of food under the denture. This tissue offers very little

resistance to pressure so the operator must be careful not to create a

false undercut by displacing it when making the impression.

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4.Distobuccal arch




Lingual Extension of the Denture

The alveololingual fold is formed by the mucous

membrane's attachment to the lingual side of the mandiblelaterally and its attachment to the lateral borders of the

tongue lingually. Because of this attachment, the fold iselevated when the tongue is protruded or when the tongue

is moved laterally. Supporting the mucous membrane andforming the floor of the mouth is the mylohyoid muscle

posteriorly and the sublingual gland anteriorly.

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The mylohyoid muscle originates at the mylohyoid ridge.

Its fibers pass downward and inward and are inserted

posteriorly to the hyoid bone and anteriorly, with its

neighbor, form the opposite side at the median raphe.

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Mylohyoid

3rd Molar Region

1st Molar Region

Premolar Region

Canine Region

Mandible

Buccinator

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The mylohyoid muscle, along with the mucous membrane can be

easily displaced by pressure. Overextended bases in this lingual

area will cause the denture to either lift out of position or result in a

denture injury.

For this reason it is necessary that an accurate non!pressure

impression be obtained of the functional range of the fold.

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Below the sublingual gland are the mylohyoid muscles, and when

this muscle raise upon swallowing it forces the gland and the floor

of the mouth upward. Therefore, this is a resistant border area,

and extension of the base is limited to the functional position of

these tissues.

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What’s our job?

Denture 2

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