Dental matrices.pdf

DENTAL MATRICES Definition: is a piece of metal or non-metal which is used to support and give form to the restoration during its packing and hardening. A matrix system provides and takes the place of the proximal tooth surface that removed during preparation. Importance of matrices: 1. serve as...

DENTAL MATRICES Definition: is a piece of metal or non-metal which is used to support and give form to the restoration during its packing and hardening. A matrix system provides and takes the place of the proximal tooth surface that removed during preparation. Importance of matrices: 1. serve as a temporary wall during condensation of any restorative material. 2. give shape and contour to the restoration and prevent marginal overhangs. 3. maintain the form of the restoration until hardening. 4. keep the gingival tissues and rubber dam away from the cavity margins during the whole procedures. Requirements: 1. easy to adapt to the teeth. 2. rigid enough to resist condensation pressure. 3. compatible with the restorative material. 4. smooth and highly polished. 5. easy to contour. 6. easy to introduce and remove. 7. thin enough to not interfere with the tightness of contact. Types of matrices: Patented Non-patented Matrix (ready-made) matrix (specially constructed)  PATENTED: 1. Ivory Matrix Holder No.1. 2. Tofflemire/ Universal Matrix System. Ivory Matrix Holder No.1 provide one proximal wall. used in compound class ii cavity preparation.  Universal (Tofflemire) Matrix: indicated for compound or complex Class II restoration. provide good stability, anatomic adaptation and ease of insertion and removal. Components: Matrix Bands: made of flexible stainless steel  available in 2 thicknesses: 0.0015 and 0.002 inch available in various occluso-gingival widths. Burnishing Matrix Band: 1. With band on pad, use small burnisher to deform band. 2. Use large burnisher to smooth band contour. 3. Burnished matrix band for MOD tooth preparation. Rules of application: 1. when the matrix band is folded, the loop will have two circumferences: the larger circumference of the band is the occlusal edge and is always placed toward the occlusal surface. the smaller circumference of the band is the gingival edge and it is always placed toward the gingiva. The matrix band placed in the slotted side of the retainer is placed gingivally.  The straight retainer placed on the buccal side.  The loop of the band could be placed: 1. Centralized 2. From right 3. From left depending on the location of the tooth so that the retainer be parallel to buccal surfaces of teeth and not disturbed by cheek movement. The contra-angled placed on the buccal or lingual side.  NON-PATENTED MATRICES 1. the wedged matrix. 2. the compound wedged matrix. 3. window matrix. The Wedged Matrix: a piece of well-contoured band material is cut to slightly extend past the cavity margins buccally and lingually and then stabilized in place by means of wooden wedge. The Compound Wedged Matrix: The same as with the wedged type, but with further stabilization using modeling compound. Advantages: 1. provides better contact and contour in restoring Class II tooth preparation. 2. adequate rigid and stable than other matrix system 3. easy to remove 4. little proximal carrving is required 5. recontouring can be easily done after compound placement Disadvantage : 1. Time consuming Window Matrix: is universal matrix with the band having custom made trapezoidal hole related to the position of class V as it is suitable for wide class V cavities with amalgam restoration. Dental Wedges (Rapid Tooth Separation Method): devices that stabilize the matrix band in place during: # condensation and hardening of the restorative material # prevent marginal overhangs # maintain adequate teeth separation to compensate for the thickness of the matrix to provide tight contact. 1.Wooden Wedge: made of orange wood, absorbs saliva and increases in size. provide more stabilization to the matrix band with adequate temporary separation of adjacent teeth. could be rounded, triangular, or anatomical. color-coded has different sizes. Wooden wedges better than plastic as it absorb water and increase in size which potentiate its function. 2.Plastic Wedge: similar to wooden wedge but made of plastic. color-coded. Placement of wedges: 1. length of the wedge should be in the range of 1-1.2 cm. 2. it should not irritate tongue, cheek and gingival tissue. 3. wedge should be inserted beneath the contact area in the gingival embrasure 4. usually inserted from lingual embrasure area as it is wider than buccal area.  A A, Correct wedge position. B, Incorrect wedge positions Modified Wedging Techniques: 1. double wedging 2. wedge wedging 3. piggy back wedging 1. Double Wedging: - 2 wedges are used, one is inserted from buccal embrasure and another is inserted from lingual embrasure. - this technique is indicated in: spacing between adjacent teeth where single wedge is not sufficient widening of proximal box in bucco-lingual dimension. 2. Wedge Wedging: - 2 wedges are used, one wedge is inserted from lingual embrasure area while another is inserted between the wedge and matrix band at right angle to first wedge. - indicated while treating mesial aspect of maxillary first premolar because of presence of flutes in root near the gingival area. 3. piggyback wedging: - 2 wedges are used, one (larger) wedge is inserted as used normally, while the other smaller wedge (piggyback) is inserted above the larger one. - it is indicated in cases of shallow proximal box with gingival recession. - this technique provides closer adaptation and contour of the matrix band