Class II Ag Matrices Flashcards
Who invented the matrix for Ag restos?
Dr. Tofflemire
Qualities of good proximal restorations
- ideal contact position and dimension occluso-gingivally and bucco-llingually
- proper proximal contours
- proper establishment of embrasures
- flush margins
Purpose of condensation
- ensure adaptation of the Ag to the walls of the prep and the matrix
- to produce a final restoration free of voids
- to remove and eliminate excess mercury
Why do we want to remove excess mercury?
Hg increases the rate of corrosion and increases risk of marginal fracture
Poor condensation leads mainly to:
marginal leakage/recurrent decay
height of Ag matrix?
1-2mm higher than the marginal ridge or tooth structure being replaced.
Depth of Ag matrix?
0.5-1mm gingival to the gingival margin of the preparation
What prevents excess Ag from flowing beyond the gingival margin of the preparation?
wedge
How to recreate contour of the tooth with matrix band?
by using a ball burnisher against the adjacent tooth to replicate the convex surface of the proximal surface
wedge functions!
- separates teeth
- stabilizes band (prevents movement)
- prevents overhang
What occurs if the wedge is positioned too occlusally?
- the band will not be kept tight against the tooth
- poor proximal contour
- poor contact
- OVERHANG
What occurs if wedge is positioned too gingivally?
- will not keep band against tooth
- will not provide separation of teeth
- may damage soft tissue
- OVERCONTOURING OF RESTO
- GINGIVAL OVERHANG
An ideally placed wedge accomplishes 3 main goals:
- prevents overhang by keeping the band tight against the tooth
- stabilizes the band
- provides separation of the two teeth to compensate for the thickness of the band
How to check for adequate wedging?
Check band and wedge placement with an explorer. If the band can be pushed from the tooth with the explorer, the wedge is either in the wrong position and/or not placed forcefully enough
Two types of wedges
- Anatomic:
- wood (premier sycmore wedges)
- plastic (flexiwedges) - Triangular:
- Wizard wedges
When choosing a wedge, choose the one that:
- fits the embrasure completely
2. provides separation of teeth
Which retainer do you use for lingual placement and which for vestibular placement?
CONTRAANGLE - lingual
STRAIGHT - vestibular
What does the contraangle retainer accomodate for?
the incisal edges of anterior teeth (it goes over them)
Which way should you orient the open portion of the retainer?
towards gingiva
Role of outer knob
tightening the band against the screw
Role of inner knob
adjust diameter of the band. Increase or decrease band size
Types of matrix bands
- conventional (flat) - must be contoured by operator
- Pre-contoured
- Dead soft or Ho Bands - matrix band has no memory
Caution for precontoured bands:
take extra care removing the band since marginal ridges may break as the band is slid out from the contact
What is the name of the system which is similar to a Tofflemire matrix system, but it is disposable/one-time-use?
Omni-matrix system. Developed for infection control, but not eco-friendly
What are the possible consequences of having a band that extends more than 2mm occlusally?
- bending or moving band with condenser
- loss of visibility
- loss of access to cavity preparation
