. He stated : “Resistance form is that shape given to a cavity intended to afford such a seat for the filling as will best enable it to withstand the stress brought upon it in mastication.
Retention form is the provision for preventing it from being dislodged
.”
What is retention and resistance?
Retention and resistance form are
the properties of a preparation that prevent castings from becoming uncemented
, which is one of the top three reasons for the replacement of castings [1,2]. Resistance form is the quality of a preparation shape that prevents rotational movement of the casting about a fixed point [3].
What is retention form in cavity preparation?
Primary retention form is the
shape or form of the conventional preparation that resists displacement or removal of the restoration by tipping or lifting forces
. For amalgam Class I and II preparations , the material is retained in the tooth by developing external tooth walls that converge occlusally.
What are the stages of final tooth preparation?
First phase: axial and occlusal reduction depths. Second phase: reduction. Third phase:
finishing line preparation
. Fourth phase: tooth surface refining.
What is primary resistance form of cavity preparation?
Primary Resistance Form. Definition:
The shape and placement of the cavity walls that best enable both the restoration and the tooth to withstand
, without fracture, masticatory forces delivered principally in the long axis of the the tooth.
What is Enameloplasty dental?
Enameloplasty is a
cosmetic dentistry treatment option
where the size and shape of an existing tooth’s enamel surface is removed or “shaved” permanently to reshape the contours of the tooth for improved appearance or as a preparation for further treatment, such as veneers or Lumineers.
What is the purpose of retention and resistance?
He stated : “Resistance form is that shape given to a cavity intended to afford such a seat for the filling as will best enable it to withstand the stress brought upon it in mastication.
Retention form is the provision for preventing it from being dislodged
.”
What is dental cusp capping?
Cusp capping is
the process of using composite fillings to replace the cusps in teeth
. A cusp is a hard protrusion on a tooth. The cusp sits higher than the rest of the tooth and therefore is the first point of contact when biting.
Why should Pulpal floor be flat?
1- Flat pulpal
floor will resist the restoration movement
, if pulpal floor is rounded, so any force exerted on the restoration will produce a wedging action on the tooth cause a splitting or shearing of the remaining tooth structure. 2- Internal line angles should be slightly curved (rounded).
Do cavities prepare?
Cavity preparation is essentially a
box in form with
floor (pulpal) and four walls. When the cavity is shallow, it is recommended to use resin composite since it does not carry the same risk of fracture under occlusal loads when used in thin sections as does amalgam.
What is the objective of tooth preparation?
OBJECTIVES OF TOOTH PREPARATION
Remove all defects and provide necessary protection to the pulp 2
. Extend the restoration as conservatively as possible 3. Form the tooth preparation so that under the force of mastication the tooth or the restoration or both will not fracture and the restoration will not be displaced 4.
What is proximal box?
A recently described technique, proximal box elevation (PBE), offers the possibility of
a stepwise relocation of deep proximal margins to uplift cavity outlines for direct
or indirect restorations.
5 , 6
. Step one (PBE) involves a meticulous layering technique for margin relocation above the CEJ.
What is a Class 2 cavity?
Class II. These cavities
occur on the surfaces between the molars and premolars
and are not visible to the human eye.
Why Axiopulpal line angle is rounded?
—Slightly round the axiopulpal line angle
to increase the amalgam bulk in that area and thereby decrease the internal stress
. -—Decrease the width of the isthmus and the depth of the isthmus and the depth of the preparation to decrease the internal stress within the tooth.
What should be the depth of the cavity?
The dimensions of the cavity preparation: occlusal cavity depth:
1.5 mm
, occlusal cavity floor mediodistal width: 2 mm; proximal box mediodistal width: 1 mm, axial wall height: 1 mm.
