Dental Cavity Preparation Techniques

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Questions and Answers

What are the three types of restorative materials mentioned for cavity preparation?

Composite resin, amalgam, and GIC.

Why is preparation of natural teeth recommended over plastic teeth in skill development?

Natural teeth provide a realistic experience for cutting enamel and dentin, which is essential for skill acquisition.

What solution is used to preserve natural teeth before preparation, and how often should it be changed?

Sodium hypochlorite 0.5%, and it should be changed every 2 weeks.

What is the main influence on the shape of the cavity in clinical situations?

The spread of caries and previously placed restorations. Signup and view all the answers

What is the primary goal during the outline phase of tooth preparation?

To remove carious dentin and unsupported enamel while preserving sound dentin. Signup and view all the answers

What should be avoided when terminating the margin of a cavity preparation?

Terminating the margin on cusp heights or ridge crests. Signup and view all the answers

What does the term 'minimally invasive preparation' refer to?

It refers to a technique that conserves as much healthy tooth structure as possible. Signup and view all the answers

What factors are considered when determining the outline form of a cavity preparation?

The extent of caries and the retention of sound tooth structure. Signup and view all the answers

What measurement indicates that cusp reduction and capping must be considered?

<blockquote> 1/3 of the distance between cusp tips </blockquote> Signup and view all the answers

What is the minimum thickness for a marginal ridge to maintain structural integrity?

1.5 mm Signup and view all the answers

What should the cavity outline resemble to avoid unnecessary weakening of the tooth?

Rounded without sharp angles Signup and view all the answers

What is an important aspect of cavity preparation to ensure adequate access for caries excavation?

Convenience form Signup and view all the answers

When preparing a Class I cavity, under what condition should it be treated as Class II instead?

If the marginal ridge minimum of 1.5 mm is not preserved Signup and view all the answers

What design feature helps enhance the primary resistance of a cavity?

Rounded internal angles Signup and view all the answers

What position of the bur is essential to achieve strong walls in dental cavities?

Correct position of the bur Signup and view all the answers

What type of dentin can be left behind when excavating carious dentin?

Dark, but hard dentin Signup and view all the answers

What angle should enamel margins be prepared at to enhance their resistance to fracture?

90° with the enamel rods resting on sound dentin. Signup and view all the answers

Why is it recommended not to have a bevel on the enamel margins during preparation?

Bevels are not recommended because unsupported thin enamel is typically removed. Signup and view all the answers

What is the significance of keeping the cavity preparations as narrow as possible?

Narrow preparations result in smaller fillings, which experience less masticatory force and have increased longevity. Signup and view all the answers

When should a slot preparation be made instead of an occlusal and proximal preparation for small class II cavities?

A slot preparation should be made if the fissures are free of caries. Signup and view all the answers

What is the potential risk associated with marginal ridge preservation in tunnel preparation?

There is a high failure rate due to the risk of fracture from unsupported marginal ridge. Signup and view all the answers

What approach should be taken to minimize damage to adjacent proximal surfaces during tooth preparation?

The proximal enamel plate should be thinned and fractured with a hand instrument. Signup and view all the answers

What is the rationale behind using a narrow bur during the initial cut in class II cavity preparation?

The narrow bur allows for precision in penetrating to carious dentin while minimizing damage. Signup and view all the answers

How does the nature of the restorative material affect the preparation technique in Class I cavities?

For resin composite material, no retention form is necessary, emphasizing a conservative outline. Signup and view all the answers

What is the purpose of a wedge placement before preparing a dental cavity?

A wedge provides tooth separation and helps prevent damage to the adjacent tooth. Signup and view all the answers

Why is it important to widen the slot faciolingually during cavity preparation?

Widening the slot faciolingually ensures that caries-free areas are obtained. Signup and view all the answers

What should be achieved regarding margin separation during amalgam preparation?

The margins should be at least 0.5 mm away from adjacent teeth. Signup and view all the answers

What is the preferred location for the gingival margin during cavity preparation?

The gingival margin should ideally be situated supragingivally. Signup and view all the answers

How should unsupported, demineralized enamel be handled during preparation?

It should be removed using a gingival margin trimmer or bur. Signup and view all the answers

What is the significance of beveling the axiopulpal line angle?

Beveling the axiopulpal line angle helps resist amalgam fracture at the junction. Signup and view all the answers

What is the maximum acceptable faciolingual width of a preparation in relation to the cusps?

The width should ideally not exceed one-third the distance between the tips of the facial and lingual cusps. Signup and view all the answers

How does including occlusal fissure preparation affect cavity retention?

Including occlusal fissure preparation improves retention of the restoration. Signup and view all the answers

What is the purpose of adding retention grooves in a slot preparation for amalgam restorations?

Retention grooves increase resistance to displacement of the amalgam during mastication. Signup and view all the answers

Describe the recommended dimensions for retention grooves in a slot preparation.

Retention grooves should be 0.5 mm wide and 0.5 mm deep. Signup and view all the answers

What is the recommended amount to reduce the occlusal surface in complex preparations?

The occlusal surface should be reduced by 2.5 mm to fit the anatomy. Signup and view all the answers

How does a pear-shaped class 2 preparation benefit tissue preservation?

It allows for a more conservative outline, saving more dental tissue. Signup and view all the answers

When preparing for composite restorations, how should enamel be treated on the buccal or lingual walls?

Enamel on these walls can be beveled to improve adaptation and seal of the composite. Signup and view all the answers

What is the benefit of refining a preparation to create an inverse bevel?

It exposes enamel rods, providing better adhesion to the gingival margin. Signup and view all the answers

What is the preferred approach for cavity preparation in class III restorations?

The lingual approach is more preferable and aesthetic. Signup and view all the answers

What separation methods should be used prior to preparation for interproximal protection?

Utilize a rubber dam, wedge, metal strip, or special WedgeGuards. Signup and view all the answers

What is the recommended tool for soft dentin excavation?

A round carbide bur at low speed is recommended for soft dentin excavation. Signup and view all the answers

How does bonding with cementum and dentin differ from bonding to enamel?

Bonding to cementum and dentin is more problematic due to their different structural properties compared to enamel. Signup and view all the answers

What technique can help reduce microleakage in dentin bonding?

Creating a groove of 0.5 mm width and depth near the external surface can help reduce microleakage. Signup and view all the answers

What is the purpose of creating enamel bevels in cavity preparations?

Enamel bevels enhance the aesthetics and retention of the restoration. Signup and view all the answers

When preparing a Class IV restoration, what is the significance of the enamel width on the bevel?

An enamel bevel of 1-2 mm width at a 45° angle is significant for retention in fractures and caries preparations. Signup and view all the answers

What shape should Class V preparations generally follow?

Class V preparations should be rounded and limited to the demineralized area, with specific shapes for different teeth. Signup and view all the answers

What is the suggested retention form for Class V preparations using resin composite materials?

Class V preparations using resin composite should have an enamel bevel occlusally, relying on acid etch retention. Signup and view all the answers

What is the minimal preservation required for mesial/distal marginal ridges in Class I composite preparations?

At least 1.5 mm of mesial/distal marginal ridge should be preserved in Class I composite preparations. Signup and view all the answers

Study Notes

Cavity Preparation (I-V)

Students and listeners are reminded that lecture/seminar information cannot be copied, recorded, or distributed without the author's consent.
Preparation rules and recommendations exist for each cavity class (I-V), with different restorative materials used.
- Composite resin
- Amalgam
- GIC
Initial teeth preparation skills are practiced on phantom teeth. This simulates experience with real teeth, allowing practice of cutting enamel and dentine, and composite bonding techniques
Natural teeth need cleaning and placing in sodium hypochlorite 0.5% for preparation.
The teeth are placed in hermetically sealed containers, and solution should be changed every two weeks.
Cavities on models are prepared following recommendations and theoretical rules of resistance for restoring the tooth.
In clinical practice, cavity shape may differ from models, based on caries spread and previous restorations.
The models depict the process clearly, and theoretical recommendations are followed during preparation.
There are different types of cavity preparations.
- Conventional preparation (retention form, special requirements)
- Conventional with bevels (amalgam restoration replaced by composite).
- Modified preparation (for composite resins)
- Minimally invasive preparation (biomimetic restorative technique)
Rules for establishing outline form include.
- Extending margins until sound enamel is reached
- Avoiding margin on cusp heights or ridge crests
- Minimizing reduction in cases of grooves extending more than one-third of cusp tip distance
The theoretical recommendations for preparation are to ensure a consistent structure as cavities can be imagined in the models.
Typical outlines for preparation should be rounded without sharp angles, keeping two occlusal cavities separate unless necessary, and preserving the transverse ridge between cusps. Extending the outline must consider efficient access for restorative work.
outlines are further described on buccal and palatal surfaces.
If the marginal ridge does not meet the 1.5 mm standard, class II preparation is considered.
The depth must be minimal 1.5 mm if amalgam needed, for support when there's load from opposing tooth.
The preparation width should not exceed ⅓ of the distance between facial and lingual cusp tips to avoid fracture.
A correct bur position is essential, enabling preparation of parallel or converging walls.
Retention is achieved through a slight convergence of axial walls.
Cavity excavation requires a low-speed round carbide bur, with hard dentin left if the cavity is deep.
Enamel margins are prepared at a 90° angle to enamel rods with sound dentin underneath.
Unsupported enamel is not resistant.
Class I preparation is to be as narrow as possible without enamel beveling in the occlusal fissure area, with the removal of unsupported enamel. General preparation requirements are similar to amalgam preparation but not relying on retention form.
Small cavities with masticatory forces result in small fillings, with increased longevity compared to large fillings
Cavity preparations for resin composite materials differ from amalgam preparations with different outlines and no retention form.
Class II preparation involves occlusal and proximal preparation, or slot, with the removal of the lesion from caries or old restorations from the occlusal surface. (slots are usually preferable)
Initial Class II cuts are made through the marginal ridge with a narrow bur; widen the slot faciolingually to remove the dentin and thinning of the proximal enamel.
Proximal surfaces of adjacent teeth may be damaged during Class II preparation. Using hand instruments to prevent damage is crucial, along with planning fractured margins.
Wedges are placed to separate teeth and prevent damage.
Slot widening is directed faciolingually until caries-free areas are reached.
The final cavity outline is determined after removing carious structures, providing a minimum of 0.5 mm margin separation from the adjacent tooth for amalgam, extending to the contact area
The gingival margin is ideally placed supragingivally, with as much healthy enamel preserved as possible
Unsupported or demineralized enamel is removed with a gingival margin trimmer or bur.
Occlusal part preparations should be limited to the demineralized area following a conservative outline to save as much structure as possible, with ridges and cusps maintained.
To resist amalgam fracture the occlusal/interproximal box junction is beveled and cavities are 1.5mm deep. Caries in the fissures extending preparation into the occlusal surface increases retention. The width buccolingually should not exceed 1/3 the distance between the tips of the facial and lingual cusps.
Faciolingual width of preparation should not exceed a third of the distance between the facial and lingual cusps to avoid fracturing. Cavity excavation of soft dentin follows.
Retention forms that include occlusal fissure cavities increase retention using walls that converge occlusally and a gingival wall directed axially.
Secondary retention grooves in the slot preparation are 0.5mm wide and 0.5mm deep and oriented parallel to the DEJ. This is usually done in low-speed situations.
Large cavities use an alternative restoration to avoid fractures, minimizing the occlusal surface to 2.5mm following its anatomy, including all cusps and covering with amalgam.
Tissue-saving preparations with pear shapes are used in Class 2 composite restorations to preserve more tissue and have a more conservative outline.
Step-by-step use of burs for preparation are further explored in image sequences (Class I).
Clinical example is to place rubber dam, wedge, and metal strip prior to cavity preparation.
Separating teeth using a WedgeGuard (e.g., Palodent) or a retaining ring facilitates interproximal protection during preparation.
Enamel preparation on buccal or lingual walls can be beveled for composite restorations.
Enamel on the gingival wall, if not close to the cervical line, can be beveled for improved composite adaptation and sealing.
Enamel bevels for Class II (composite) include bevels on buccal and lingual/gingival walls. Adequate enamel may not be present on gingival walls.
Proximal lesion excavation, with refining preparation and an inverse bevel, enhances enamel rod exposure and gingival margin adhesion.
Final composite resin preparation stages are described with images.
Class III cavities are beneath the contact point, often in the middle of the proximal surface. Class III preparation follows a similar outline to Class II, using a facial or lingual approach as appropriate. A rounded form and maintaining sound structure away from adjacent teeth is a key concern.
Caries extending to dentin cementum requires extra preparation to prevent microleakage, using 0.5-0.7mm depth grooves away from the surface of the root (technically difficult). An adhesive composite restoration is recommended in this type of preparation.
Enamel bevels for Class III (using glass ionomer cement) do not require grooves or bevels.
Class IV preparation (fractures or caries spreading to incisal edges) requires sufficient enamel width and preparation at 45-degree angles to allow for retention.
In the cases of caries, the margins of Class III caries extending to incisoral edges, is prepared with wider bevels onto the vestibular and palatal sides as well.
Class V preparation has a rounded outline, limited to the demineralized area, shaped as kidney shapes (premolars) or sausage shapes (molars).
Grooves may be placed to reduce microleakage on gingival walls but doing so is technically difficult and does not retain all healthy dentin.
Class V for composite preparation prepares with enamel bevel occlusally and then uses acid-etch retention in enamel.
Minimal preparation is needed for Glass Ionomer cements.
Summary highlights various considerations for different cavity classes (Class I composite preparation, Class II composite, Class III-IV, Class V for GIC). Key factors include faciolingual width limits, preserving marginal ridges, ensuring adequate enamel width, and appropriate bevels considerations based on whether for Amalgam/Composite or glass-ionomer cements.

Sequence of Burs

Key anatomical burs and instruments related to cavity preparation are also visually presented.

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Description

This quiz focuses on essential techniques and principles of dental cavity preparation. Explore the types of restorative materials and various considerations for effective tooth preparation, including minimally invasive approaches and cavity outline formation. Test your understanding of best practices in dental skill development.