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Artificial tooth crowns
Orthodontic
Abstracts
und
Reviews
91
only metals and alloys of great hardness which will not easily give off particles, and also to use only such alloys as will best resist corrosion. Of special interest to the orthodontist is the chapter on soldering and welding. It is advised to use solders whose composition and melting point are close to those of the precious metal because in this manner a more thorough penetration of metal and solder can take place. If the solder starts flowing at a much lower temperature than the melting point of the alloy, the alloy will not yet be in condition to receive the solder properly. The heat should not immediately be stopped at the moment the solder BOWS, but should be continued for a few seconds. Lat,er on, heat treatment will further improve the strength of the soldered joint. The welded joint is superior to the soldered one. The second part of the book deals with non-metallic materials: plaster of Paris, its origin and chemical reactions together with suggestions for practical use ; investment materials, studied by means of temperature-expansion charts ; impression materials-beeswax, gutta-percha, compound, dentocoll (the problems of sterilization or disinfection of these materials after use is given consideration ; from experiments and investigations it becomes evident that it is practically impossible to sterilize them sufficiently for repeated use in the mouth) ; materials for grinding and polishing; India rubber and the process of vulcanization ; porcelain and porcelain substitutes ; zinc phosphate and silicate cements. The germicidal value of these cements, even if they contain copper, is questionable; neither is their role in the injury and death of underlying pulps sufficiently clarified. The adhesive quality of all cements is not due to stickiness, like that of glue, but to friction created by minute irregularities on the surface of both tooth and inlay (or band). The adhesion is the greater the closer the adaptation of the two surfaces and the thinner the layer of cement between them. In his presentation Dr. Falk has succeeded in rendering a rather abstract subject readable and interesting. The chapters dealing with the crystalline structure of metals are not only instructive but also fascinating to read. Many materials which the dentist uses every day are brought closer to his understanding by a knowledge of their origin, manufacture, and properties. Artificial Tooth Crowns (Kuenstliche Zahnkronen). By Dr. Albert Werkenthin. Third part of the author’s “Textbook of Dentistry in Five Parts.” Gersbach und Sohn Verlag, 1937, Berlin, Germany. This volume is primarily intended to be a textbook, and the illustrations are arranged in a manner which makes them instructive in themselves. The text is descriptive and the details of construction are easily understood. The book deals with the toothrest left in the mouth after loss of the natural tooth crown ; with the technical parts of artificial crowns ; with the jacket crown and other porcelain crowns; with Crowns consisting of porcelain and metal, and those consisting only of metal ; with pin and pivot crowns. It is the author’s objective to make the book complete and uniform in character despite the variety of elements composing it. He uses the historic-
92
Orthodontic
Abstracts
and
Reviews
comparative method in his descriptions, acquainting the reader not only with the present status of crown technique but also with the developments which have taken place in this highly limited field within the last fifty to eighty years. The nomenclature suggested by Dr. Werkenthin is unique and original. He divides the artificial crown in several parts: a;, the crown body; b, the pin or pivot; etc. In the same manner, the material used for the construction of the various parts is marked: a, porcelain; /3, porcelain plus metal; y, metal only, etc. The classification derived from this nomenclature is simple (1) a+a,a+b,a+ccrowns; (2) ,8+a,P and at the same time descriptive: + b, p + c crowns ; (3) a + a, a + ,8, a + y crowns ; and so forth. This eliminates the cumbersome descriptions which are necessary if old names (like Richmond crown with gold crown body) are used, complicated by the fact that the meaning of these terms is not universally uniform. The scientific character of the presentation is evident in the chapter dealing with the physical properties of crowns and their anchorage to their supporting roots. Careful mathematical calculations are used to determine the force of mastication and the pressure exerted at the various parts of the artificial tooth surface. In conjunction with these calculations, a thorough study is made of the properties of those materials which are used in the construction of the crowns. A generous number of diagrams, tables, and mathematical formulas is provided to take all guesswork out of technical procedures and to supply scientific data and explanation, An unusually beautiful cover of blue leather distinguishes this volume, The illustrations and diagrams are abundant and clear, and the paper and type are excellent. Egon Neustadt.
Abstracts
und
Reviews
91
only metals and alloys of great hardness which will not easily give off particles, and also to use only such alloys as will best resist corrosion. Of special interest to the orthodontist is the chapter on soldering and welding. It is advised to use solders whose composition and melting point are close to those of the precious metal because in this manner a more thorough penetration of metal and solder can take place. If the solder starts flowing at a much lower temperature than the melting point of the alloy, the alloy will not yet be in condition to receive the solder properly. The heat should not immediately be stopped at the moment the solder BOWS, but should be continued for a few seconds. Lat,er on, heat treatment will further improve the strength of the soldered joint. The welded joint is superior to the soldered one. The second part of the book deals with non-metallic materials: plaster of Paris, its origin and chemical reactions together with suggestions for practical use ; investment materials, studied by means of temperature-expansion charts ; impression materials-beeswax, gutta-percha, compound, dentocoll (the problems of sterilization or disinfection of these materials after use is given consideration ; from experiments and investigations it becomes evident that it is practically impossible to sterilize them sufficiently for repeated use in the mouth) ; materials for grinding and polishing; India rubber and the process of vulcanization ; porcelain and porcelain substitutes ; zinc phosphate and silicate cements. The germicidal value of these cements, even if they contain copper, is questionable; neither is their role in the injury and death of underlying pulps sufficiently clarified. The adhesive quality of all cements is not due to stickiness, like that of glue, but to friction created by minute irregularities on the surface of both tooth and inlay (or band). The adhesion is the greater the closer the adaptation of the two surfaces and the thinner the layer of cement between them. In his presentation Dr. Falk has succeeded in rendering a rather abstract subject readable and interesting. The chapters dealing with the crystalline structure of metals are not only instructive but also fascinating to read. Many materials which the dentist uses every day are brought closer to his understanding by a knowledge of their origin, manufacture, and properties. Artificial Tooth Crowns (Kuenstliche Zahnkronen). By Dr. Albert Werkenthin. Third part of the author’s “Textbook of Dentistry in Five Parts.” Gersbach und Sohn Verlag, 1937, Berlin, Germany. This volume is primarily intended to be a textbook, and the illustrations are arranged in a manner which makes them instructive in themselves. The text is descriptive and the details of construction are easily understood. The book deals with the toothrest left in the mouth after loss of the natural tooth crown ; with the technical parts of artificial crowns ; with the jacket crown and other porcelain crowns; with Crowns consisting of porcelain and metal, and those consisting only of metal ; with pin and pivot crowns. It is the author’s objective to make the book complete and uniform in character despite the variety of elements composing it. He uses the historic-
92
Orthodontic
Abstracts
and
Reviews
comparative method in his descriptions, acquainting the reader not only with the present status of crown technique but also with the developments which have taken place in this highly limited field within the last fifty to eighty years. The nomenclature suggested by Dr. Werkenthin is unique and original. He divides the artificial crown in several parts: a;, the crown body; b, the pin or pivot; etc. In the same manner, the material used for the construction of the various parts is marked: a, porcelain; /3, porcelain plus metal; y, metal only, etc. The classification derived from this nomenclature is simple (1) a+a,a+b,a+ccrowns; (2) ,8+a,P and at the same time descriptive: + b, p + c crowns ; (3) a + a, a + ,8, a + y crowns ; and so forth. This eliminates the cumbersome descriptions which are necessary if old names (like Richmond crown with gold crown body) are used, complicated by the fact that the meaning of these terms is not universally uniform. The scientific character of the presentation is evident in the chapter dealing with the physical properties of crowns and their anchorage to their supporting roots. Careful mathematical calculations are used to determine the force of mastication and the pressure exerted at the various parts of the artificial tooth surface. In conjunction with these calculations, a thorough study is made of the properties of those materials which are used in the construction of the crowns. A generous number of diagrams, tables, and mathematical formulas is provided to take all guesswork out of technical procedures and to supply scientific data and explanation, An unusually beautiful cover of blue leather distinguishes this volume, The illustrations and diagrams are abundant and clear, and the paper and type are excellent. Egon Neustadt.