Lithium Disilicate Restorations Fatigue Testing Parameters: A Systematic Review

Abstract

The studies reviewed showed a level of heterogeneity, as testing parameters were considered through different setups. The current study demonstrated that various setting of the testing parameters and having a lack of testing standardization has likely led to inconsistency in the reported results. The obvious heterogeneity in the setting of testing variables-especially the magnitude of load and number of cycles applied-made it impractical to run direct comparisons between the reviewed studies. Therefore, specific international standardization of fatigue testing of dental restorations is urgently needed to ensure the delivery of consistent, indicative, and comparable data.

“Digitally Oriented Materials”: Focus on Lithium Disilicate Ceramics

“…Differently, as regards FDPs, the cumulative survival rates at 5 years ranged from 75% to 100% in vitro [28, 29] while the equivalent clinical rate was 78.1% [26]; long-term laboratory investigations simulating more than 10 years of service showed 70% survival rate [30], comparable to the in vivo cumulative survival rate of 70.9% after 10 years of function [26]. The sound level of agreement between in vitro and in vivo data confirmed that laboratory investigations could represent a good simulation of the clinical scenario; nonetheless, this conclusion has to be considered only indicative, since the amount of data is not large enough to indicate consolidated clinical guidelines [24]. …”

“…Several laboratory studies investigated the fatigue resistance of lithium disilicate single crowns (SCs) and fixed dental prostheses (FDPs) to evaluate experimental designs and testing parameters [20–24]. Different laboratory variables were proved to influence the fatigue resistance of lithium disilicate restorations, such as magnitude of load, number of cycles, abutment and antagonist material, wet environment, and thermocycling; conversely, chewing frequency, lateral movements, and aging technique were considered not influential factors [23].…”

“…Different laboratory variables were proved to influence the fatigue resistance of lithium disilicate restorations, such as magnitude of load, number of cycles, abutment and antagonist material, wet environment, and thermocycling; conversely, chewing frequency, lateral movements, and aging technique were considered not influential factors [23]. Single load to fracture after fatigue tests (i.e., combination of dynamic and static loading until fracture) reported highly variable ultimate strength values for this material: from 980.8 N to 4173 N for monolithic SCs and from 390 N to 1713 N for posterior FDPs [23, 24]. Significant comparisons between data were not possible because of the heterogeneity of research designs and testing modalities [24].…”

“…Single load to fracture after fatigue tests (i.e., combination of dynamic and static loading until fracture) reported highly variable ultimate strength values for this material: from 980.8 N to 4173 N for monolithic SCs and from 390 N to 1713 N for posterior FDPs [23, 24]. Significant comparisons between data were not possible because of the heterogeneity of research designs and testing modalities [24]. …”

“…The lack of testing standardization made it almost impossible to perform consistent comparisons between laboratory studies. Consequently, to date, indicative and comparable data about dynamic mechanical testing of lithium disilicate restorations remain still controversial; further investigations with specific standardization criteria are needed [24]. …”