Effect of Thermomechanical and Static Loading on the Load to Fracture of Metal‐Ceramic, Monolithic, and Veneered Zirconia Posterior Fixed Partial Dentures

Abstract

Purpose To evaluate the influence of static (not preloaded) and thermomechanical loading on the load to fracture of metal‐ceramic, monolithic and veneered zirconia computer‐aided design/computer‐aided manufacturing (CAD/CAM) posterior fixed partial dentures (FPDs). Materials and Methods One hundred standardized specimens with 2 abutments screwed onto a platform were prepared from stainless steel to receive a posterior 3‐unit FPD with an intermediate pontic. Specimens were randomly divided into 5 groups (n = 20): Metal‐ceramic (control group), Lava Zirconia system, Vita In‐Ceram YZ, IPS e.max ZirCAD, and Lava Plus. Half of the specimens of each group (n = 10) underwent no preloading, and the other half were subjected to thermomechanical loading in a masticatory simulator, and then all FPDs were loaded until fracture using a universal testing machine at a 1 mm/min crosshead speed. The load to fracture of the veneering ceramic and the load to fracture of framework (total fracture) were recorded for each specimen. Data were statistically analyzed using 2‐way ANOVA, Tukey's HSD post‐hoc test, Student's t test, and Weibull statistics, α = 0.05. Results Significant differences were recorded between the metal‐ceramic and veneered zirconia groups for the veneering ceramic load (p < 0.001; f = 36.62; f = 57.76) in no preloading and thermomechanical loading subgroups, respectively, but no differences were observed between the static and thermomechanical loading conditions. No differences were observed among the veneered zirconia groups. For the total load to fracture, significant differences were observed according to the material (p < 0.001; f = 500.8), between the metal‐ceramic and Lava Plus group and the other zirconia groups in no preloading subgroup, and between metal‐ceramic and the other groups (p < 0.001; f = 303.33) in thermomechanical loading subgroup. For the type of preloading, significant differences were observed (p = 0.02; f = 5.24) between the Lava Plus group and the other groups. Thermomechanical loading significantly decreased the fracture load of the Lava Plus group (p = 0.005). The Weibull statistics corroborated the results. Conclusions Monolithic zirconia restorations provided the highest load to fracture values among the zirconia groups tested; however, the results indicate that they must be used in the oral environment with caution, because their load to fracture was influenced by the aging simulation.

Comparison of Fracture Resistance Between Two Monolithic and One Veneered Zirconia Materials on Molar Crowns After Thermomechanical Fatigue

“…The abutment material plays a crucial role in evaluating the strength of dental restorative materials as it affects the mechanical properties and fracture resistance. The literature data emphasize the clear advantageous effect of phosphate monomers on bond strength zirconia/luting cements associated with mechanical pretreatments (airborne particle) in order to achieve enduring bond values (18,19).…”

Prospective Clinical Evaluation of Posterior Monolithic Zirconia Fixed Partial Dentures Using a Complete Digital Workflow: Two‐Year Follow‐Up

“…However, significantly lower survival rates were reported on implant‐supported FPDs 22 . The main clinical complication of veneered zirconia restorations is the chipping of the veneering ceramic, 1,6,9,15,17,19–29 indicating medium and long‐term clinical studies a chipping prevalence of 0% to 54% in FPDs 4,6,10,16–18,21,22,29 . Monolithic zirconia restorations have been recently introduced to solve the chipping problem 13,30–33 .…”

Are Metal-Free Monolithic Crowns the Present of Prosthesis? Study of Mechanical Behaviour

“…The present study used metal-ceramic full coverage crowns as its control group, as according to the literature is the most supported [1,2,3,4,5,10]. The trial compared the control crowns with crowns made from other monolithic and non-monolithic materials with ceramic coverings [2,3,4,5,6,7,8,11], including PMMA doped with graphene nanoparticles, a recently launched dental material [15]. Monolithic zirconia crowns are made with CAD/CAM techniques and allow more conservative dental preparation [13,16,17].…”

“…The load applied was 80 N with vertical displacement of 2 mm and protrusive displacement of 2 mm and 2 Hz frequency. In static load testing, a load cell of 5000 N was used at a crosshead speed of 0.5 mm/min until fracture, a procedure used in many other similar trials [2,3,8,11,12].…”

“…However, the metal-free restorations are developed more popular in last years for supply the disadvantages in its esthetic appearance and biocompatibility [1,2,3,4,5]. In this context, porcelain-veneered crowns with zirconia cores have been introduced and are supported by some studies that confirm the good resistance of this material [2,6,7,8], although its main disadvantage is caused by a cohesive failure between both components and is known in the literature as chipping is seen in 10%–15% of crowns [6,7,8,9,10,11]. This problem has generated some doubt as to the prognosis of these materials in the long term.…”