Correlation between clinical performance and degree of conversion of resin cements: a literature review

Abstract

Resin-based cements have been frequently employed in clinical practice to lute indirect restorations. However, there are numerous factors that may compromise the clinical performance of those cements. The aim of this literature review is to present and discuss some of the clinical factors that may affect the performance of current resin-based luting systems. Resin cements may have three different curing mechanisms: chemical curing, photo curing or a combination of both. Chemically cured systems are recommended to be used under opaque or thick restorations, due to the reduced access of the light. Photo-cured cements are mainly indicated for translucent veneers, due to the possibility of light transmission through the restoration. Dual-cured are more versatile systems and, theoretically, can be used in either situation, since the presence of both curing mechanisms might guarantee a high degree of conversion (DC) under every condition. However, it has been demonstrated that clinical procedures and characteristics of the materials may have many different implications in the DC of currently available resin cements, affecting their mechanical properties, bond strength to the substrate and the esthetic results of the restoration. Factors such as curing mechanism, choice of adhesive system, indirect restorative material and light-curing device may affect the degree of conversion of the cement and, therefore, have an effect on the clinical performance of resin-based cements. Specific measures are to be taken to ensure a higher DC of the luting system to be used.

Influence of monolithic lithium disilicate and zirconia thickness on polymerization efficiency of dual‐cure resin cements

“…However, former studies have provided evidence that the activation time generally recommended by the manufacturer is not sufficient to achieve the maximum degree of conversion . Therefore, prolonged light exposure is recommended when highly opaque or thicker restorations are required, because a gradual increase in the light‐curing time and, consequently, light transmission results in a gradual increase in the hardness of resin‐based luting systems . The degree of conversion of a dual‐cure resin cement may vary from 37% when light cured for 20 seconds to 58% when light cured for 40 seconds; this confirms the aforementioned direct correlation between the light intensity received by a photoactivated dual‐cure material and its degree of conversion …”

“…It is expected that the tertiary amine will interact with benzoyl peroxide to secure adequate curing in areas with inadequate light exposure. However, it has been reported that dual‐cure resin cements may perform decreased hardness when not properly photoactivated, which implies a reduced degree of conversion . In this study, it was observed that Panavia F 2.0 was not polymerized under 2.5‐mm‐thick monolithic zirconia and 3‐mm‐thick monolithic lithium disilicate, whereas the other two cements were polymerized under all ceramic thicknesses.…”

“…However, it has been reported that dual-cure resin cements may perform decreased hardness when not properly photoactivated, which implies a reduced degree of conversion. [31][32][33] In this study, it was observed cements. Previous studies reported that Panavia F 2.0 is more dependent on light activation and may not polymerize completely without adequate light irradiation.…”

“…In this study, the hardness tests were performed following a 24‐hours storage and 12‐hours specimen preparation period. Even though the degree of conversion is maximized during the first 30 minutes after light activation, some dual‐cure resin cements were reported to present a gradual increase in the degree of conversion for up to 24 hours . In addition, it has been speculated that a delay in the light activation of dual‐cure materials would enhance their properties by allowing the self‐polymerization promoters to react to some extent before getting entrapped by the polymeric chains as soon as photoactivation begins .…”

Fracture Resistance of Endodontically Treated Teeth Restored with Lithium Disilicate Crowns Retained with Fiber Posts Compared to Lithium Disilicate and Cerasmart Endocrowns: In Vitro Study

“…It must be considered that the adhesion of the restoration is dependent on the type of cement used moreover, it can be expected that the greater the adhesion of the restoration, the better the stress distribution within the system, thus resulting in higher fracture resistance. Not less important, premolars and molars may receive similar forces during oral function, contributing for the similar results when considering only posterior teeth [53]. Forberger et al [54] endocrowns resulted in similar fracture strength when compared to groups restored with posts based on ceramic (zirconia), gold or glass fiber.…”