Luting indirect restorations with resin cements versus composite resins: Effects of preheating and ultrasound energy on film thickness

Abstract

Objective This study aims to evaluate and compare the film thickness obtained with a resin cement and two composite resins, preheated and/or ultrasonically vibrated, as luting agents. Materials and methods One hundred and twenty‐six (126) pairs of resin discs were randomly assigned to six experimental groups (n = 21) according to luting agent (Variolink Esthetic LC, IPS Empress Direct or Estelite Omega) and cementation technique (preheating at 68°C and/or ultrasonic vibration). Specimens were luted by applying a controlled force. Following sectioning and film thickness measurement through field emission gun scanning electron microscopy, statistical analysis was carried out considering a 5% significance level. Results Statistically significant lower film thickness was observed in Variolink Esthetic LC group when compared to all composite resin groups (p < 0.001), except IPS Empress Direct preheated and ultrasonically vibrated group (p = 0.073). IPS Empress Direct with ultrasonic vibration yielded statistically lower film thickness values than Estelite Omega groups, regardless of luting technique (p < 0.05). Ultrasonically vibrated Estelite Omega groups showed statistically lower film thickness values than solely preheated groups (p < 0.05). Conclusions Both Variolink Esthetic LC and IPS Empress Direct preheated and ultrasonically vibrated provided the lowest film thickness. The addition of ultrasonic vibration during cementation proved to be effective in reducing film thickness of both tested composite resins. Clinical significance The cementation technique will have variable results depending on the luting material. Adhesive cementation protocols with composite resins should mainly consider ultrasonic vibration, but also preheating, as strategies for reducing film thickness. The tested resin cement, alongside with IPS Empress Direct composite resin preheated and ultrasonically vibrated, provided the lowest film thickness among the tested materials and techniques.

Update on Dental Luting Materials

“…Recently, there have been studies looking into the possibility of using restorative composite resin as an alternative luting material due to it having a lower cost, better strength properties, lower marginal deterioration, and greater range of shade selections [ 134 ]. As a restorative material, composite resin differs from resin cements by having a higher percentage of filler particles, resulting in it having a higher viscosity, greater film thickness and lower flowability [ 135 ].…”

“…Both of the techniques were shown to be effective in reducing the film thickness of the material. However, not all of the tested composite resins after preheating and ultrasonic vibration were able to reach a film thickness of less than 50 μm [ 134 ], which is specified in ISO standard 4049:2019 [ 137 ]. When a thin film thickness and a high viscosity cannot be achieved, the fracture resistance of the restoration and marginal adaptation will be drastically jeopardized [ 138 , 139 , 140 ].…”

Is There a Correlation Between Physical Properties and Film Thickness of Dual- and Photo- polymerized Luting Resins and CAD/CAM-Dentin Micro-Tensile Bond Strength?

“…When the assembly (CAD/CAM composite/luting cement/dentin) is loaded in tension defects can act as stress zones [38], initiating crack propagation, inducing failure at low bond strength values. In addition, when the FT is high, as in the case of VB, higher volumetric polymerization shrinkage is expected, which will lead to high polymerization shrinkage stresses [39]. it was reported previously that preheating increased the tendency of increasing the shrinkage stress rate, which could lead to lowering the bond strength of luting resins [40].…”

Selective adhesive luting: A novel technique for improving adhesion achieved by universal resin cements

“…Such optimal clinical performance is directly related to the formation of a reliable and durable bond between the tooth structure and ceramic material. To this end, the choice of luting material, as well as strictly following the adhesive procedure steps as recommended by the manufacturer, is fundamental 3 …”

“…To this end, the choice of luting material, as well as strictly following the adhesive procedure steps as recommended by the manufacturer, is fundamental. 3 Resin-based composite cements are considered the materials of choice for luting of partial and full-coverage indirect restorations made of LiSi ceramics. 4 Current dental market offers a great variety of resin cements, mainly classified according to their polymerization mechanism (light-, self-, and dual-cure) 5 or the number of clinical steps and adhesive mechanism used during luting procedures (multi-step/adhesive and one-step/self-adhesive resin cements).…”