dental matrices Flashcards
What is matrix?
that thing which contains & gives form to anything
What is dental matrix?
a piece of metal or other material which is used to support and give form to the restoration during its packing & hardening
What are the uses of different types of matrices according to?
cavity preparation design and the type of restorative material used
What are the functions of matrices?
- matrices serve as temporary wall or walls during condensation of plastic
restorative materials (build up of missing wall) - to give shape and contour to the restoration and maintain it till hardening
- prevent marginal overhangs (intercontact between gingival seats)
- to keep the gingival tissues away from the cavity margins
- to protect the adjacent hard and soft tissues
What are the requirements of matrix materials?
- easily adapted to teeth and maintain this adaptation during condensation
- easily introduced and removed
- easily contoured
- strong enough to resist force of condensation
- thin enough to preserve the contact between teeth (0.002 inch)
- smooth and highly polished –> smooth surface texture of restoration
- compatible with the restorative materials
What are the parts of the matrix system?
- matrix retainer (holder): holds a band in desired position and shape
- matrix band: a piece of metal or polymeric material, intended to give support and form to the restoration during its insertion and setting
- matrix band should extend 2mm above the marginal ridge height and 1mm below gingival margin of the preparation
What is the classification of matrices according to mode of application?
- with retainer
- without retainer
What is the classification of matrices according to material of band?
- metallic (non-transport)
- non-metallic (transparent)
What is the classification of matrices according to type of cavity?
- matrix for class I (compound/complex) during extension: double banded tofflemire matrix
- matrix for class II: sectional matrix system, saddle matrix, automatrix, Ivory no. 1 and Ivory no. 8
- matrix for class III: Myler strip (most known), S shaped matrix and Unica matrix
- matrix for class IV: mylar strip, transparent crown former, custom lingual matrix, modified S shaped, Unica
What is the classification of matrices according to shape of band?
- contoured
- not contoured
What is the classification of matrices according to extension of matrix?
- circumferential matrix
- sectional matrix
What is the classification of matrices according to dentition?
- anterior matrix
- posterior matrix
What is ivory matrix no.1?
- provides only one proximal wall (sectional matrix)
- used in occluso-mesial or distal cavities (compound class II cavities) for amalgam restorations
- contains retainer
- metallic
what type of restorations use circumferential band?
amalgam and glass ionomer
What type of restoration uses sectional band?
composite
What is ivory matrix no.8
- can encircle the whole crown of the tooth (circumferential matrix)
- used in all compound and complex cavities for amalgam restorations
- metallic
- with retainer
What is the tofflemire or universal matrix?
- considered the best one in its stability and anatomic adaptation
- suitable for all cases; compound or complex cavities (circumferential matrix)
- the matrix band is available in two thicknesses (0.0015 and 0.002 inch)
and in different occluso-gingival width - the proper width of the band should be selected so the band is extended 2mm above the height of the marginal ridge to be restored
- not contoured
- has a retainer and bnd
What are the fnctions of ring?
- adaptation of band in place
- stabilise band in place
- separation
Is it possible to use composite with circumferential band and how?
yes, if there is a contact former
are all sectional bands contoured?
yes
What is the automatrix?
- consists of a ready-made band that encircles the tooth (circumferential matrix)
- it is tightened by a special device
- suitable for compound and complex cavities especially extensive cavity preparations
- bands are supplied in different widths and thicknesses
- considered as a retainerless matrix as the matrix band is placed without a retainer
- advantages: convenient, improved visibility and saves time
What is omni matrix?
- consists of a ready-made band and retainer attached to each other
- it encircles the tooth (circumferential matrix)
- suitable for compound and complex cavities
- it is color coded matrix according to the size
- has retainer
- one-time use
What classes can sectional bands be used in?
class II, III and IV
What is Unica anterior matrix?
- simple and ideal matrix for anterior restorations such as class III, IV, V, direct composite veneers, and shape modifications
- makes it possible to restore interproximal and cervical margins at once, reducing chair time significantly
