Microstructure and Adhesive Properties of Copal Composite in Dental Incrustations
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Microstructure and Adhesive Properties of Copal Composite in Dental Incrustations M. N. Orta-Amaro, J. A. Rodríguez-Chávez2, I. A. Belío-Reyes1, L. Bucio, J. Arenas-Alatorre, J.L. Espinoza3 and M. C. Flores-Grajeda1 Instituto de Física UNAM, Apartado Postal 20-364, 01000 México D. F., México. 1 Facultad de Odontología, Universidad Autónoma de Sinaloa, Blvd. de las Américas y Universitarios, 80010 Culiacán, Sinaloa, México. 2 Facultad de Odontología, Universidad de Guadalajara, Sierra Morena 950, Guadalajara, Jalisco, Mexico. 3 Coordinación Estatal de Salud Bucal, Secretaria de Salud del Estado de Sinaloa, Culiacán, Sinaloa, México. ABSTRACT There are evidences that in ancient cultures in Mexico, copal was probably used for gluing precious stones in teeth cavities and for dental restorations as well. This is an important reason for making experiments using copal and copal-based composites in order to have more information for the potential applications of this material in modern dentistry. In our experiments concerning with dental incrustations of turquoise, we have practiced round cavities (about 1 mm depth) in the middle of incisive teeth by using a low-speed air turbine. Turquoise was cut in such a way that fits exactly on the tooth cavity. Copal and powdered apatite were used to glue the stone into the cavity. With Scanning electron microscopy we have observed that the composite copal-powdered apatite, penetrates the dentin tubules in the tooth tissue (depth of penetration from 5.6 to 41 micrometers), suggesting the existence of a micromechanical adherence. Concerning to the characterization of the adhesive properties, we have applied the ASTM D2095-72 test considering the adhesion of two cylinders of bone, and the copal composite as the adhesive. A maximum cohesive tensile strength around 0.1 MPa for elastic response was measured for hydroxyapatite compositions of 0, 25 and 75 wt%. We will discuss these results considering the reports of dental incrustations in ancient Mexico. INTRODUCTION Among the gums and resins in the American and European markets today, copal refers in general to a very wide group of resins characterized by their hardness and relatively high melting point. Copal is a term used for the description of some terpenoid resins which becomes amber with the loss of their essential oils hardening by polymerization and oxidation. Amber typically dates from the Triassic to Tertiary Periods. Fresh copal, usually intended for incense, should not be confused with sub-fossil copal (‘‘copalite’’ from the Quaternary Period) that is incorrectly sold as Colombian, Dominican, Mexican, or Baltic ‘‘amber’’ [1]. Most of these resins which originate in Mexico are from the tropical Burseraceae family [2]. These natural resins have been employed in varnishes, paints, and as binders in pressed and stamped articles [1]. Apparently copal was the basis of the sticky-materials employed in ancient Mexico to elaborate several wonderful pieces such as the granite mask discovered in Malinaltepec, Guerrero, Mexico, w
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