Preparations for Severely Debilitated Teeth

Peripheral

__________ destruction may require an extensive restoration such as a full crown because of the wide expanses of enamel that have been affected.

Amalgam

A large central lesion that has undermined much of the enamel may require the placement of an _______ core followed by a crown.

Core

Combined destruction of severe dimensions may also require the placement of a ____ or foundation restoration followed by a crown.

Principle of Substitution

A preparation may be modified by squaring the walls of defects left by caries and old restorations and by adding features to enhance retention and resistance.

Boxes

_____ may be substituted where grooves might ordinarily be used.

Grooves

May be used to augment retention and resistance where axial walls have been shortened.

Pins

May be employed where much of the supragingival tooth structure has been destroyed

Core

The central “____” must not be invaded in vital teeth.

1.5 mm

No retentive features should extend farther into the tooth than __ mm from the central fossa.

Dentin

No wall of ______ should be reduced to a thickness less than its height for the sake of retention.

Box Form

Small to moderate interproximal caries lesions or prior restorations can be incorporated into a preparation as a ___ ____.

Box Forms

This substitute for grooves serves the dual purpose of caries removal and form retention.

1

Grooves placed in vertical walls of bulk tooth structure must be well formed, at least _ mm wide and deep, and as long as possible to improve retention and resistance.

Grooves

Multiple _______ are as effective as box forms in providing resistance, and they can be placed in axial walls without excessive destruction of tooth structure.

Grooves

However, too many _______ in a crown preparation can adversely affect the seating of a full veneer crown.

Pins

Retention ____ effectively increase by generating additional length internally and apically rather than externally.

Externally

Retention pins effectively increase by generating additional length internally and apically rather than __________.

Pins

They do not require vertical, supragingival tooth structure for their placement, and they can be used where there is insufficient axial wall length.

Yes

Can pins extend apically beyond the gingival attachment without harming it?

Pinholes

________ parallel the path of insertion of the preparations, receiving pins that are an integral part of the cast restoration.

Non-parallel

___________ pins are placed in the tooth to retain an amalgam or composite resin core.

Corners

The safest locations for pinholes are the _______ of the teeth.

Corners

The least desirable area for placing pinholes is midway between the _______, regions overlying the furcations.

Pulp - Periodontal Membrane

If bleeding occurs during drilling of a pinhole, it should be determined whether the misdirected drill has gone into the ____ or the ___________ ________.

Cement Bases

Are used only to protect the pulp and to eliminate undercuts in defects in tooth structure produced by the removal of caries or old restorations.

Cement Bases

They are used if there is adequate bulk of tooth structure to resist occlusal forces.

GIC - Polycarboxylate

Are excellent materials as cement bases (2).

No

Do cement bases have sufficient strength to effectively replace weakened dentinal walls?

Amalgam - Composite Resin

If one-half or more of the clinical crown has been destroyed, an _______ or _________ _____ core should be placed in the tooth.

Full Coverage

The core is then treated as though it were tooth structure, and a classic ____ ________ preparation is used.

Bleaching

For a tooth that has become discolored following devitalization, _________ is preferable to crown placement if the tooth is relatively intact.

Dowel Core

If a metal-ceramic crown is required because of extensive coronal destruction, a _____ ____ probably is needed.

Resin

Cementing the dowel with bonded _____ cement strengthens the weakened coronal dentin around the dowel.

Crown

If a dowel is used, its extension into the root must at least equal the length of the _____ for optimum distribution stress and maximum retention

4

A minimum length of _ mm of gutta-percha, and more, if possible, should remain at the apex to prevent dislodgment and subsequent leakage.

Premolars

A dowel core should be used on _________ only if the roots are adequately long, bulky, and straight.

Ferrule

The encirclement of 1.0 to 2.0 mm of vertical axial tooth structure within the walls of fracture, a crown creates a _______ effect around the tooth to protect it from fracture.

Fracture

If a tooth is flush with the gingiva, fabrication of a dowel core and a crown without encirclement of tooth structure could result in root ________.

Orthodontic Extrusion

___________ _________ and crown lengthening surgery may be needed to prevent encroachment on periodontal tissues.

Post Crown

A fixed restoration which replaces the coronal part of the tooth completely and is retained by a post (dowel) which is extended and completely cemented into the root canal.

Post - Core - Crown

Components of post crown (3).

Crown

Ideally the length of post should be equal to, at least , the length of the estimated clinical _____.

Occlusal

The post must have an ________ stop to prevent displacement apically resulting in fracture of the prepared root.

Keyway

Is prepared in the canal orifice where there is the greatest bulk. It is cut to the depth of the bur diameter, 0.6 to 1mm. and up to 4mm. into the canal

Ferrule

An encircling band of cast metal around the coronal surface of the tooth. Provides bracing or casing action to protect the integrity of the root.

Ferrule Effect

360 metal collar of the crown surrounding the parallel walls of the dentine extending coronal to the shoulder of the preparation.

Ferrule Effect

Having 1.0 mm of vertical tooth wall between the margin of the core and the shoulder of the preparation to provide a _______ ______.

Amalgam - Composite Resin

Prefabricated dowels with _______ or _________ _____ cores are the most commonly used dowel cores today and there is a wide variety of dowel systems available.

Passive (Cemented) - Active (Threaded)

Dowel systems can be classified by their mechanism of retention (2).

Threaded

The ________ dowels are more retentive than the cemented, but they also produce more stress in the tooth.

Parallel-sided Post

(Post) Are made up of platinum-gold-palladium (Pt-Au-Pa or PGP), nickel-chromium (Ni-Cr) or stainless steel (SS) clasp wire.

Serrated Post

(Post) Come in SS, titanium or non-oxidizing noble alloy.

Tapered Post

(Post) Are available in Au-Pt, Ni-Cr, and titanium alloy.

Peeso Reamer

Is measured against a radiograph of the tooth being restored to determine the length to which the instrument will be inserted into the canal.

Largest

Enlargement of the canal begins with the _______ Peeso reamer or Gates Glidden drill that will fit into the canal.

Composite Resin

If the core is to be _________ _____, a copper band can be used, but it is easier and faster to use a crown form.

Light Activated - Polycarbonate

A clear crown form permits the use of a _____ _________ resin, while a _____________ form can be used with autopolymerizing resins.