Fundamentals in Tooth Preparation

These flashcards provide a comprehensive review of fundamental principles in tooth preparation, covering definitions, classifications, stages, and specific restorative techniques based on the provided lecture notes.

What is the definition of tooth preparation?

The mechanical alteration of a defective, injured, or diseased tooth in order to best receive a restorative material which will re-establish the healthy state of the tooth including esthetics correction when indicated along with normal form and function.

What is an intracoronal restoration?

A restoration placed within a preparation made in the crown of a tooth.

What is an extracoronal restoration?

A restoration placed outside the tooth which uses an indirect technique.

Which material used in restoration is specifically noted for its ability to bond to tooth tissue and release fluoride ions?

Glass Ionomer Cement (GIC)

How is a simple tooth preparation defined?

A preparation where only one tooth surface is involved.

What is a compound tooth preparation?

A preparation where two surfaces are involved, such as mesio-occlusal ($MO$) or disto-occlusal ($DO$).

What is a complex tooth preparation?

A preparation that involves more than two surfaces, such as Mesio-occlusodistal ($MOD$).

What is an internal wall in tooth preparation?

A prepared surface that does not extend to the external tooth surface.

Define the axial wall.

An internal wall that is parallel to the long axis of the tooth.

Define the pulpal wall.

An internal wall that is perpendicular to the long axis of the tooth and is located occlusal to the pulp.

What defines an external wall?

A wall that extends to the external tooth surface and takes the name of the tooth surface towards which it is situated.

What is a floor in tooth preparation?

A prepared wall which is usually flat and perpendicular to the occlusal forces directed occlusogingivally.

What is the cavosurface angle?

The junction of a prepared wall and the external surface of the tooth.

What constitutes enamel margin strength?

It is formed by full-length enamel rods whose inner ends are on sound dentin and supported on the preparation side by shorter rods.

How many line angles and point angles does a Class I tooth preparation have?

$8$ line angles and $4$ point angles.

How many line angles and point angles does a Class II tooth preparation have?

$11$ line angles and $6$ point angles.

How many line angles and point angles does a Class III tooth preparation have?

$6$ line angles and $3$ point angles.

How many line angles and point angles does a Class IV tooth preparation have?

$11$ line angles and $6$ point angles.

How many line angles and point angles does a Class V tooth preparation have?

$8$ line angles and $4$ point angles.

Where do Class I pit and fissure preparations occur?

On the occlusal surfaces of premolars and molars, the occlusal two-third of buccal and lingual surface of molars, and the lingual surface of incisors.

What characterizes a Class II preparation?

Preparations on the proximal surface of premolars and molars.

What characterizes a Class III preparation?

Preparations on the proximal surface of anterior teeth and not involving the incisal angles.

What characterizes a Class IV preparation?

Preparations on the proximal surface of anterior teeth also involving the incisal angle.

What characterizes a Class V preparation?

Preparations on the gingival third of facial and lingual or palatal surfaces of all teeth.

What characterizes a Class VI preparation?

Preparations on incisal edges of anterior and cusp tips of posterior teeth without involving any other surface.

What are the three characteristics of a conventional design preparation typified by amalgam?

$1.$ Uniform pulpal and/or axial wall depths, $2.$ Cavosurface margin design resulting in a $90^{\circ}$ restoration margin, and $3.$ Primary retention form from occlusally converging vertical walls.

What are the two stages of tooth preparation?

Initial Tooth Preparation Stage and Final Tooth Preparation Stage.

What is the focus of the initial tooth preparation stage?

Essentially a superficial surgical incision through enamel caries to the depth of the DEJ followed by lateral extension to fully expose the carious dentin lesion.

How deep should the preparation be extended internally for pit and fissure lesions?

No deeper than $2.0\,mm$ ($0.5\,mm$ when restoring with direct gold).

How deep should the preparation be extended internally for smooth surface lesions?

$0.2$ to $0.8\,mm$ into dentin.

What is Step 1 of the tooth preparation process?

Initial depth and outline form.

What is Step 2 of the tooth preparation process?

Primary resistance form.

What is Step 3 of the tooth preparation process?

Primary retention form.

What is Step 4 of the tooth preparation process?

Convenience form.

What is Step 5 of the tooth preparation process?

Removal of defective restorative material and/or soft dentin.

What is Step 6 of the tooth preparation process?

Pulp protection.

What is Step 7 of the tooth preparation process?

Secondary resistance and retention forms.

What is Step 8 of the tooth preparation process?

External wall finishing.

What is Step 9 of the tooth preparation process?

Final procedures: debridement and inspection.

What is the recommended internal depth of the DEJ for established initial depth?

$0.2\,mm$.

What is the recommended internal depth to the normal root surface?

$0.8\,mm$.

Define Outline Form.

The overall outline of the preparation placing margins in the position they will occupy in the final preparation.

What is the logic behind 'Extension for Prevention'?

Including extensions to remove enamel imperfections to prevent recurrence of decay and result in self-cleaning embrasure areas.

What allows for 'Prevention of Extension' in modern dentistry?

Natural and fluoride-induced remineralization, advancements in instrumentation, restorative materials, and preparation designs.

How far must two faults be apart to keep them separate preparations?

At least $0.5\,mm$; if the distance is less, they should be connected.

What is Enameloplasty?

The removal of sharp and irregular enamel margins by rounding or saucering to convert them into a smooth, cleansable groove.

What is the maximum axial depth for Class V cavities?

$0.8$ to $1.25\,mm$ pulpally.

Define Primary Resistance Form.

The shape and placement of walls to best enable both the tooth and restoration to withstand masticatory forces without fracture.

What is the minimum occlusal thickness for an Amalgam restoration?

$1.5\,mm$.

What is the minimum occlusal thickness for a Ceramic restoration?

$2\,mm$.

What is the minimum occlusal thickness for Cast Metal and Composite?

$1$ to $2\,mm$.

What is 'Cusp Capping'?

Cusp reduction and coverage used to provide resistance against forces in the long axis and oblique directions.

When is cusp reduction considered mandatory?

When the outline form has extended $2/3$ the distance from a primary groove to a cusp tip.

Define Primary Retention Form.

The shape and configuration of the preparation that resists the displacement of restoration under lifting and tipping masticatory forces.

What provides the primary retention form in Amalgam Class I and II preparations?

Occlusal convergence of external walls (about $2^{\circ}$ to $5^{\circ}$).

What is an occlusal dovetail?

A feature used in Amalgam Class I, II and Cast Metals to provide retention.

How is retention achieved for Composites?

Micromechanical bonding between etched and primed surfaces with composites.

Define Convenience Form.

The form which facilitates and provides adequate visibility, accessibility, and ease of operation during preparation and restoration.

In Class II preparations, how is access typically made for convenience form?

Through the occlusal surface.

What tools are used to remove a small amount of remaining carious lesion?

A low speed handpiece with a round bur or a spoon excavator with light force.

What is 'Infected Dentin'?

A superficial layer of demineralized dentin contaminated with bacteria that cannot be remineralized and is soft.

What is 'Affected Dentin'?

A deeper layer not yet invaded by bacteria that is firm or leathery and can be remineralized.

Which substances can stain infected dentin?

$0.2\%$ propylene glycol, $10\%$ acid red solution, or $0.5\%$ basic fuschin.

How much bulk is generally desirable between the pulp and metallic restorative materials?

A $2\,mm$ dimension.

When is a liner indicated in tooth preparation?

When the excavation extends to within $0.5\,mm$ of the pulp.

What is the function of a Liner?

Applied directly to exposed dentin to stimulate reparative dentin, provide dentin sealing, and pulpal protection.

What is the function of a Base?

A thicker layer providing bulk and additional strength to the restoration along with pulpal protection.

What is the purpose of a Sealer?

A thin layer applied to the internal surface to seal dentin and prevent microleakage.

What is Varnish specifically used for in amalgam restorations?

Reducing sensitivity and protecting the tooth from moisture; it is contraindicated in composites.

What effect does Zinc oxide eugenol have on the pulp?

A sedative effect.

Why is Zinc oxide eugenol contraindicated in composite restorations?

It interferes with the polymerization or hardening of the composite.

Define Secondary Retention and Resistance forms.

Added preparation features used in complex preparations to improve mechanical locking and prevent dislodgement.

What are 'Grooves' in secondary retention?

Shallow channels prepared within dentin, typically along axiogingival or axiofacial line angles.

What are 'Coves' in secondary retention?

Rounded depressions prepared within dentin at the junction of two surfaces, like the incisal and facial walls.

What is a 'Slot' or internal box?

Small, box-shaped depressions typically $1.0$ to $1.5\,mm$ deep, used to increase surface area for bonding.

Why are Slots not placed in enamel?

Because enamel is brittle and prone to fracture.

How do 'Locks' work in secondary retention?

They create a tight fit in a vertical direction when tooth height is reduced, similar to a key in a lock.

What are 'Pins' in tooth preparation?

Small, tapered cylinders of metal or composite inserted into holes drilled into dentin for reinforcement.

What are 'Collars' in secondary retention?

Raised areas of tooth structure surrounding a pin hole that create a positive lock.

What are 'Skirts' and what is their typical depth?

Features that encircle the tooth structure to resist occlusal forces, with a depth and width usually around $1\,mm$.

What are 'Amalgam Pins'?

Features that act like anchors by mechanically interlocking the restoration with the dentin.

What does enamel etching consist of?

Etching the enamel with an acid to result in a microscopically roughened surface for mechanical bonding.

What is the objective of External Wall Finishing?

To achieve a better marginal seal, increased strength at the margins, and increased smoothness.

What is Step 9, also known as the 'toilet of the cavity'?

Final procedures: cleaning, inspecting, and sealing.

What does 'Debridement' involve?

Using an air/water syringe to remove debris and then excess moisture.

Why should desiccation be avoided during final procedures?

Excessive drying may cause odontoblasts to be aspirated into dentinal tubules.

How should a tooth preparation be dried correctly?

Using light bursts of air and/or dry cotton pellets to avoid desiccation.

What factor determines whether a preparation is 'Simple', 'Compound', or 'Complex'?

The number of surfaces involved.

Which wall is perpendicular to the long axis and occlusal to the pulp?

The pulpal wall.

What is the term for the acute junction formed by the cavity wall and external tooth surface?

Cavosurface margin.

How many line angles are in a Class III preparation?

$6$.

Where are retention grooves or coves the primary form of retention?

In Amalgam Class III and IV restorations because external walls diverge.

In Class II restorations, where is the gingival seat placed?

Apical to the contact but occlusal to the gingival margin, with a clearance of $0.5\,mm$ from the adjacent tooth.

What is the rule for the axial wall's orientation?

It should be parallel to the external surface of the tooth.

What is the purpose of rounding internal line angles?

To reduce stress concentration points in the tooth preparation.

What is the function of Calcium Hydroxide?

It is a biocompatible liner that stimulates tertiary dentin.

What are 'Altered preparation designs'?

Beveled conventional preparations and modified preparations that may lack uniform depth or converging walls.

What defines the 'extension for prevention' practice in outline form?

Placing margins in self-cleansing areas to prevent future decay.

What is the final step in establishing a proper outline form regarding depth?

Limiting the depth of preparation to $0.2$ to $0.8\,mm$ into dentin.

What is the secondary retention feature for Cast Metal restorations?

Coves, skirts, and dentin slots.