. Principles and practice of filling teeth. ewhat moredisastrous to plugger points than the latter, the serrations beingmore rapidly battered down when coming in contact with steel thanwith dentine or enamel. IXTEODUCTIOX A^D FINISHING OF GOLD FILLINGS. 199 The Kind of M<ifi-ix.—Xo one form of matrix may be deemedavailable for all cases, and in some instances it will be found desir-able to improWse a matrix specially for the case in hand. Theband matrices made of thin steel, such as the Brophy matrix (), serve an excellent purpose for ordinary work, though they arenot universally appl
. Principles and practice of filling teeth. ewhat moredisastrous to plugger points than the latter, the serrations beingmore rapidly battered down when coming in contact with steel thanwith dentine or enamel. IXTEODUCTIOX A^D FINISHING OF GOLD FILLINGS. 199 The Kind of M<ifi-ix.—Xo one form of matrix may be deemedavailable for all cases, and in some instances it will be found desir-able to improWse a matrix specially for the case in hand. Theband matrices made of thin steel, such as the Brophy matrix (), serve an excellent purpose for ordinary work, though they arenot universally applicable. The material of which these matricesare made is almost ideal for the purpose. The steel is sufficientlyrigid to sustain the gold against thorough malleting, and yet itsspringy nature admits of it being forced away from the cavity-margins by pressure of the plugger. There are some objections tothese matrices which occasionally assert themselves, chief of whichmay be mentioned the fact that in bell-crowned teeth the matrix Fig. embraces the tooth tightly near the occlusal surface and standssome distance away from the neck along the gingival half of thecavity. This objection may readily be overcome by packing somegutta-percha into the interproximal space between the matrix andthe proximating tooth, so as to force the matrix up to the gingivalmargin of the cavity. Wooden wedges have sometimes been advo-cated for this purpose, but the danger with these is that the wedgeis likely to force the matrix too close to the margin, and the woodis so unyielding that the plugger cannot press the matrix back toallow the gold between it and the margin. With gutta-percha thematrix may be carried as close to the cavity as desired, and thematerial will be found sufficiently yielding to admit of manipula-tion by the plugger .so as to .secure perfect protection to the cavity-margins. Another difficnltv sometimes encountered with the band nuitrix 200 PKINCIPLES AND PRACTICE OF FILLING T
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