the matrix 1 depicted in fig1 within its central area , is provided with a positioning portion 2 which , on both sides , is followed by two terminal areas 3 which , with respect to the positioning part 2 , are stepped in such a way that the positioning part 2 projects with a section from the plane formed by the upper edges of the two terminal areas 3 . the matrix 1 is provided with two stamped - out windows 5 ; it is preferably constructed in two layers , in which case the one supporting layer comprises a thin steel band of e . g . 0 . 05 mm thickness , upon which an equally thin , transparent strip of plastic , by way of preference of cellulose acetate , is attached . the two layers may be bonded to each other , be thermally sealed by warmth or heat or be joined together in some other way ; when in use , they form a unit , in which case the plastic strip rests against the dental filling and the steel band is at a distance from said filling , as is illustrated e . g . in fig5 . the fig2 and 3 show , in a top view and in a side view , a dental group 7 comprising three teeth , of which the center tooth has a cavity 8 which has to be filled with a plastic while the original shape of the tooth is adhered to . within the area of the dental neck 9 , as is apparent from fig3 the circumference of the tooth decreases . it is for this reason that the matrix , when engaging around the tooth to be treated and when the matrix is contracted at its two ends 3 , has to produce a conical shape in order to encircle the dental configuration tightly which , at the point of contact , is broader . that is why the wall edge towards the cervical area is shorten than the edge which faces the marginal strip of the filling , as is disclosed by fig3 . the matrix 1 reproduces the anatomical configuration of the tooth within the cervical area , i . e . within the area of the dental neck , as accurately as possible . it thereby prevents the excessive filling with filling material within this area and thus protects the marginal parodontium . in order to resist the lateral forces occurring during the insertion of the filling material , the matrix 1 is equipped with the steel band . the fig4 to 6 depict analogous representations as do the fig1 to 3 , but of closely set teeth and with a small diameter of the dental neck of the tooth to be tretaed . in this embodiment , the matrix band should likewise project cervically only a little above the approximal box in order to be wedged there . this wedging is shown particularly in fig7 on an enlarged scale . the fig4 shows a matrix 12 having a curvature 13 which is greater than that of the matrix 1 according to fig1 as well as with two windows 5 , 5 &# 39 ; and a pronounced conical stepping 15 which corresponds to the smaller circumference of the dental neck . this matrix 12 is intended to be used on a dental group 18 in which the center tooth has a cavity and a , in diameter , relatively small dental neck 20 . the matrix according to fig4 allows for this configuration by the relatively large conical stepping 15 . in fig7 two teeth are illustrated in a side view , viz . a sound tooth 25 and a tooth 26 with a cavity provided with a plastic filling 27 which is indicated in a dash - dotted manner . a matrix 28 of the type described has an externally located steel band 30 with one or several windows 31 and a plastic band 32 resting against the tooth to be treated 26 . an illuminating wedge 34 is inserted between the dental necks of the teeth 25 and 26 . the fig8 shows the top view of the teeth according to the arrangement according to fig7 in which case the two matrix ends 35 of the matrix laid around the tooth to be treated 26 are tightened with the aid of a matrix tightener 36 around the tooth by the matrix ends being seized and whereby the filling is imparted the shape desired in the fig7 and 8 . the lighting of the illuminating wedge 34 by means of an external light source permits , in this position of the parts , to cure the critical area where plastic and dental material meet as the first within the primary curing area 37 and to thereby prevent the feared shrinkage interstices between the plastic and the dental material . the areas of the plastic material which are located at the top are cured subsequently in such a way that the shrinkage of the curing manifests itself only on the free areas of the plastic and , basically , the entire plastic material can be cured so as to be devoid of the formation of any cracks or interstices . the matrix has , dependent upon the application indication , one ( for single approximal fillings ) or two windows ( for double approximal fillings ) of cellulose acetate within the approximal area . the windows make a perfect light curing within the approximal area possible . the action of the light is not restricted . the matric band is retained in position with the aid of matrix tighteners , such as the toffel wire system , the uhm system or the nystrom i and ii system . the fig9 a to 9e and 10 , 10a to 10e show premolar matrix bands , while the fig1 , 12a to 12k show molar matrix bands . the bulges 40 are clearly perceptible . the fig1 and 14 show the basic form of double - bulge matrix bands , while fig1 discloses a single - bulge embodiment . in this case the window sizes of molar bands are approximately 5 × 10 mm and the premolar bands possess a window size of approximately 4 × 8 mm . the fig1 shows a cellulose acetate strip 42 , such as is applied prior to the stamping out of the matrix with the steel band and subsequent to the windows being stamped out . fig1 shows a tooth 45 in perspective representation provided with a filling 46 which is schematically boldly framed and identified with zones 48 , 49 and 50 . an illuminating wedge 52 is acted upon by a light source with light beams 55 which , owing to the construction of the wedge , are deflected and thus cure the lowermost zone 48 when light is incident . subsequently the two zones 49 and 50 , as is apparent in a diagrammatically shown manner , are finally cured , in which case the matrices shown in the various figures appropriately encircle the plastic filling 46 so that the same can be subjected to the curing process in a geometrically correct manner . in fig1 , a device 60 for the fabrication of matrix bands is diagrammatically illustrated which comprises a plastic band roll 61 and a metal band roll 161 . the metal band of the steel band roll 161 is passed through a stamping means , by means 64 of which the pertinent number of windows is stamped out . the plastic band is removed from the roll and the stamped - out metal bands are laminated to each other in the joining station 65 by heat , adhesive or suchlike so that they are able to form an inseparable unit . the two combined bands are conveyed into a matrix punch 67 , with the aid of which the matrices 68 are fabricated and ejected possesing a form in which they are ready for use . the metal band imparts the requisite rigidity to the window matrices , which again is of advantage when the band is laid as well as in the shaping the filling . according to one of the embodiments , the matrix 1 is comprised of a thin band - shaped blank of steel or some other suitable material , it being also possible to employ plastics which do not react with the dental filling . in this band - like metallic blank , one or several window - like perforations 5 are formed which , by means of a strip - shaped blank , are covered by means of a transparent , more particularly , crystal - clear plastic , said plastic strip possessing a design which corresponds to the shape and dimensions of the steel band of the matrix 1 so that the plastic strip coincides fully with the steel band . however , the possibility also exists of disposing blanks of transparent plastic solely within the area of the window 5 in the steel band , in which case these plastic bands are dimensioned in such a way that the windows 5 are covered and that they rest with a section against the wall area of the steel band so as to make it possible to attach the plastic blanks to the steel band . as covering for the windows 5 , transparent plastic are employed , such as e . g . plastics having a cellulose base , such as cellulose acetate , or vinyl polymerisates , ps , pmma and pc . according to a further embodiment , the matrix provided with at least one window 5 is comprised of a blank constructed according to the configuration of the matrix fabricated from a transparent , crystal - clear plastic , e . g . possessing a cellulose base , such as cellulose acetate , or a vinyl polymerisate , ps , pmma and pc , in which case especially such plastics are employed as are used for optical purposes , in which a certain elasticity has to be present so as to enable one to lay the matrix around a tooth . for the formation of windows 5 , the matrix of the plastic strip is provided with a metallic coating which may e . g . be vapor - deposited while window - like areas are formed . metallized plastics of this type are produced by non - galvanic or by galvanic processes . consequently , the fabrication may be effected in accordance with the metallization process , in which low - melting metals are applied to the plastic in the form of a mist or according to the metal reduction method , in which metal salt solutions , e . g . gold , silver or copper salt solutions are reduced with the aid of formaldehyde . the materials then precipitate onto the plastic . a metal coating is also possible to effect in accordance with the vacuum deposition method . in the present case , as plastics are employed those which neither combine with the dental fillings nor are partially or completely dissolved by the latter . the advantage of using metal coated matrices resides in the simplified fabrication . large - surface blanks of a suitable plastic are coated with the aid of metals while , at the same time , a number of uncoated surface sections are formed whose number corresponds to that of the matrices then to be stamped out from the blank , which subsequently form the windows 5 . following the coating , the matrices are then stamped out of the metal - coated blank , in which case each matrix is provided with a window - like area that - is transparent . if it is intended that every matrix is to possess several windows 5 , in that case the coating process , per matrix to be stamped out , a corresponding number of transparent areas are left blank . the fig1 shows a matrix 1 of a carrier or supporting material 80 of a transparent plastic which is provided with a metallic coating 81 in which one window 5 has been left blank . it is furthermore possible for the matrix 1 to be comprised of a glass metal which is inserted in the form of a thin band or film or sheet , from which the matrix 1 is fabricated while windows 5 are produced . the number of the windows 5 constructed in the matrix 1 may be arbitrarily selected , in which case , apart from one window , the matrix 1 may be provided with two or even more than two windows disposed in side - by - side - arrangement . especially advantageous in this connection is also a latticed construction of the metallic part of the matrix so that a plurality of windows 5 is formed which are disposed in a side - by - side arrangement or on top of each other . the inherent stability of the matrix 1 is improved by means of this design while an adequate flexibility is maintained at the same time . the windows 5 possess a square , rectangular , circular or some other geometric configuration .
the dental matrix has at least one transparent region and its design is such that the marginal adaptation of approximal edge regions of light - cured mo , od and mod composite restorations is optimized .