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
WHat are cervical matrices?
- used in class V restorations
- advantage: excellent cervical contour
- disadvantage: expensive
What is mylar strip matrix?
- used in class III and IV
- advantage: easy to use and inexpensive
- also called celluloid strip
- transparent
What is the gold standard of dental wedges?
wooden wedges
What are the functions of dental wedges?
- stabilize the matrix band in its place during condensation, packing and
hardening of the restorative material - prevent marginal overhang
- prevent seepage of the restorative material from the matrix during packing
- maintain adequate teeth separation to compensate for the thickness of the matrix band (this is essential for proper and tight contact)
What is the indication of round wooden wedge?
conservative class II preparations
What is the indicatopn of triangular wooden wedge?
preparation with deep gingival margin
What is the indication of plastic wedge?
preparation with deep gingival margin
What is the indication of light transmitting wedge?
cervical portion of class II composite
What are wooden wedges?
- most commonly used and preferred
- can be easily trimmed and fitted in gingival embrasure
- adapt well in the gingival embrasure
- easy to use
- absorbs water, thus increase the interproximal retention
- stabilize the matrix band
What does prewedging compensates for?
- thickness for matrix band
- polymerization shrinkage of composite (expansion takes place)
- exposed tooth margin and push gingiva downward
What are the contacts location of teeth?
- maxillary and mandibular anteriors: in incisal third
- maxillary and mandibular posteriors: in the middle third
What are the consequences of not restoring proximal areas?
- food impaction
- recurrent caries
- trauma to the periodontium (pocket formation)
- gingival inflammation
- rotation and drifting of teeth
What is another name for retainer?
ring
What is the functon of a retainer?
holds band in place
