Effect of firing protocols on cohesive failure of all-ceramic crowns

Efecto del liner en la resistencia adhesiva de cerámica feldespática a la zirconia utilizando protocolo de enfriamiento lento

“…8,9,[19][20][21] In evaluating failure type among all the samples in the present study, we found out that all showed a combined type of failure (adhesive/cohesive). This result may be connected with the ceramic veneer thickness (4 mm) used in this study, since it is bigger than suggested by the manufacturer (1.5-2 mm).…”

“…17,18 The present study evaluated and compared a ceramic veneer bond strength to zirconia blocks by different manufacturers (Ecco Amann Girrbach Zirconia -Ivoclar e.max ZirCAD) and the convenience of using a liner through a slow cooling protocol as suggested by some authors. 8,9,[19][20][21] The use of liners has been proposed to improve the aesthetic characteristics of restorations with zirconia structures. 11 However, some authors suggest that using a liner can affect the bond strength of the ceramic veneer to zirconia.…”

“…8,9,[19][20][21] El manejo de estos protocolos disminuyen significativamente la tensión residual que se genera en la cerámica de recubrimiento con estructuras en zirconia. 24,25 Algunos autores sugieren que una tensión residual excesiva en la cerámica de recubrimiento sometida a cargas oclusales podría ser uno de los factores que propician la aparición de chipping o delaminación de la cerámica de recubrimiento con estructuras a base de zirconia.…”

“…8,9,[19][20][21] La utilización del liner se ha propuesto para mejorar las características estéticas de las restauraciones con estructuras en zirconia. 11 Sin embargo, algunos autores sugieren que al utilizar un liner se puede afectar la resistencia adhesiva de la cerámica de recubrimiento a la zirconia.…”

“…4 Concerning the causes of such complications, the authors suggest that inappropriate structure design, 5 differences in the ceramic material's coefficient of thermal expansion, 6 and rapid cooling of the ceramic veneer cause excessive residual tension of it, generating micro-fissures or detachment of the ceramic veneer in the presence of masticatory forces. 7 In order to control this residual pressure, it has been suggested to conduct slow cooling protocols during the firing process, 8 as well as ceramic coatings measuring less than 1.5 mm in thickness. 9 However, the high opacity of zirconia reduces its use in restorations in the anterior sector, where it would affect appearance when se utilicen espesores de cerámica de recubrimiento menores a los descritos anteriormente.…”