PRINCIPLE OF TOOTH REDUCTION l Fixed prosthodontics ( tooth crown ) MCQs

principle of tooth reduction l Fixed prosthodontics ( tooth crown ) MCQs (Multiple choice question) for preclinical dental student.

 

Introduction to Fixed Prosthodontics and dental prothesis

Objectives

•   Provide an overview on fixed prosthodontics.
•   List important terms related to fixed prosthodontics.

 

An overview on fixed prosthodontics

 

Prosthesis:

• It is an artificial replacement of an absent part of the human body.

 

Dental prosthesis:

• It is an artificial replacement of one or more teeth (up to the entire dentition) and associated structures.

 

Prosthodontics: It is subdivided into:

•      - Removable prosthodontics.
•      - Fixed prosthodontics: The branch of prosthodontics concerned with the replacement and/or restoration of teeth by artificial substitutes that not readily removed from the mouth.

Crown

• An artificial replacement that restores missing tooth structure by surrounding part or all of the remaining structure with a material such as cast metal, porcelain, or a combination of materials such as metal and porcelain.

 

Fixed partial denture

• Any dental prosthesis that is luted, screwed or mechanically attached or otherwise securely retained to natural teeth, tooth roots, and/or dental implant abutments that furnish the primary support for the dental prosthesis.
• Components of the fixed partial denture:

   o Pontic:

• It that part which acts as the actual substitute for the lost tooth and is suspended between the retainers replacing the lost natural tooth functionally and esthetically.

 

   o Retainer:

It is that part which rebuilding the prepared tooth and by the means of which the pontic is attached to the abutment tooth.

 

   o Connector:

 

• It is that part uniting the pontic with retainer (i.e. joining the component parts). It may be rigid (cast, soldered or welded) or non-rigid connector.
• Abutment tooth: It is the natural tooth which supports and retains the fixed partial denture.

Resin-bonded restorations

• A fixed dental prosthesis that is luted to tooth structures which has been etched to provide mechanical retention for the resin cement.

 

Radicular retained restoration

• It consists of a post with an attached core that obtains its retention and resistance from prepared root portion of an endodontically treated tooth.
• While the root preparation retains the post, the core establishes retention and resistance for a crown that restores the tooth to normal form and function.
• This post and core may be custom-made or prefabricated.

 

Occlusion examination

Occlusal problems can lead to :

• 1- Tooth wear [Attrition, abfraction]
• 2- Fracture of tooth or a restoration
• 3- Restoration de bonding
• 4- Bone resorption + gingival recession + tooth mobility
• 5- PDL sensitivity and pain

 

Ideal bite :

                         

A. In static occlusion - ICP / MI :

• you ask the pt to tap down on the articulating paper
• There should be equal contacts on all cusp tips and fossa – heavier contacts posteriorly - pre mature contacts will be heavily stained with less stain on adjacent points
• Premature contacts are caused by high cusps – deflective contacts are caused by large cusps they will cause the tooth or mandible to deflect in ICP [ more harmful]
• To examine location of contact points → use articulating paper [ 40 um]
• To examine how heavy the contact is → use shimstock

B. In dynamic occlusion – lateral excursion:

• You ask the pt to slide their jaw to the right and to the left side
• Ideally there should not be any interference on working or non- working side [ non working side interference is needed in complete denture pts]

 

C. In protrusion:

• ideally you should have Even contacts on all anterior teeth and no posterior interference.
• Occlusal analysis should be done before any restoration. – if the pt has an interference [do not adjust it because the patient is already accustomed to it]
• Do not create an interference yourself !
• Place the articulating paper [ red facing the arch being examined ] then ask the pt to move their jaw to the right or the left then use the blue side to record ICP . Any pure red mark [ not over lapped by blue ] is an excursive mark [ can be guidance or interference]