51. Single crown requirements. Teeth preparation for single crowns.

whats in it

• when is crown used

• what is dental crown

• steps in single crown fabrication

• then describe each step obvi

when is crown used

Crownlargest tooth restoration. It covers all the supragingival sides of the tooth. It is used when there is a limited tooth structure left due to caries lesion that cannot be restored with onlay, or when an existing crown must be replaced.

what is the dental crown

Dental crown – is a fixed extra-coronal artificial restoration of the coronal portion of the natural tooth. It must restore the anatomic shape, size, contour, colour and function of the tooth, protecting the underlying structures from further damage.

Steps in a single crown fabrication (classic method):

• prep the crown

• final impression

• temporisation

• pouring a working model /working cast

• wax up

• investing

• casting

• cleaning, finishing, polishin

• cemenration

tooth prep

instrumenttation proceduers that drives tooth into final shape and size

• eliminate undercuts from axial walls of the tooth (slightly inward dents on the walls of vertical side of the tooth are flattened/smoothened out)

• to create a finishing line (prep junction) (border between the prepared tooth surface and the unprepared natural tooth.)

• to provided minimum required space for crown to withstand mastication forces

2. Final impression

All the procedures that leads to acquiring a negative copy of the prepared tooth.

Objectives:
1. To acquire CLEAR and ACCURATE impression.
2. To capture the MINIMUM REQUIRED amount objects, that are necessary for the construction of the model.

3.Temporization— All the procedures for achieving a temporary crown.

Objectives:

1. To cover and protect the open dental tubules from thermal and chemical irritation and bacterial invasion.
2. To fix and secure the already prepared tooth into the same position as it was before the preparation.

4. A working cast fabrication

conversion of negative impression into a positive model

1) to reproduce clear and accurate details

to restore minmum required objects that are necessary for the constructuon of the crown

wax up

• wax pattern is created in working cast

• To reproduce the shape, size and all the details of the future crown.

investing

casting

cleaning, finishing and polishing

• produce negative copy of details of wax pattern

• creates path of elimination of wax and secure a path for replacement material into the mold (sprues)

• wax is burnt out in burning out process

casting: A method for filling of the wax mold with any liquid material (metal or ceramics).

Objectives:
1. To fill all the details of the mold with the replacement material.

Cleaning, finishing and polishing

auxiliary procedures that are used in the course of casting and elimination of the investing material.

Objectives:
1. To remove all the remnants of the investing material and the sprues.
2. To bring the cast into the desired shape and size of the future restoration. 3. To finish and polish the outer surface of the crown

.

try in proecudure

cementation

— To try the final restoration into the patient’s mouth. Objectives:

1. To check the marginal fit.
2. To check the a proximal contacts with the adjacent teeth.
3. To check the occlusion (the contacts with the opposing dentition).

cementation - fix crown on prepped tooth with help of dental cement