Three- to nine-year survival estimates and fracture mechanisms of zirconia- and alumina-based restorations using standardized criteria to distinguish the severity of ceramic fractures

Abstract

Objectives The aims of this study were set as follows:1. To provide verifiable criteria to categorize the ceramic fractures into non-critical (i.e., amenable to polishing) or critical (i.e., in need of replacement) 2. To establish the corresponding survival rates for alumina and zirconia restorations 3. To establish the mechanism of fracture using fractography Materials and methods Fifty-eight patients restored with 115 alumina-/zirconia-based crowns and 26 zirconia-based fixed dental prostheses (FDPs) were included. Ceramic fractures were classified into four types and further subclassified into "critical" or "non-critical." Kaplan-Meier survival estimates were calculated for "critical fractures only" and "all fractures." Intra-oral replicas were taken for fractographic analyses. Results Kaplan-Meier survival estimates for "critical fractures only" and "all fractures" were respectively: Alumina single crowns: 90.9 and 68.3 % after 9.5 years (mean 5.71 ± 2.6 years). Zirconia single crowns: 89.4 and 80.9 % after 6.3 years (mean 3.88±1.2 years). Zirconia FDPs: 68.6 % (critical fractures) and 24.6 % (all fractures) after 7.2 and 4.6 years respectively (FDP mean observation time 3.02±1.4 years). No core/framework fractures were detected. Conclusions Survival estimates varied significantly depending on whether "all" fractures were considered as failures or only those deemed as "critical". For all restorations, fractographic analyses of failed veneering ceramics systematically demonstrated heavy occlusal wear at the failure origin. Therefore, the relief of local contact pressures on unsupported ceramic is recommended. Occlusal contacts on mesial or distal ridges should systematically be eliminated. Clinical relevance A classification standard for ceramic fractures into four categories with subtypes "critical" and "noncritical" provides a differentiated view of the survival of ceramic restorations.

Short‐Term Prospective Clinical Evaluation of Monolithic and Partially Veneered Zirconia Single Crowns

“…The annual incidence of complications for ceramic chipping has been estimated to be 0.64%; loss of another 0.64% of the crowns per year because of ceramic fractures was also estimated . Apart from inherent flaws as origins of ceramic failure, zones of occlusal contact wear have been identified as primary starting points of chipping fracture . Posterior crowns were, accordingly, found to be particularly vulnerable to chipping .…”

“…2 Apart from inherent flaws as origins of ceramic failure, zones of occlusal contact wear have been identified as primary starting points of chipping fracture. 16 Posterior crowns were, accordingly, found to be particularly vulnerable to chipping. 17 Rinke and colleagues confirmed this; they evaluated 323 single crowns (96 incisors, 89 premolars, and 138 molars) over a mean period of 79.7 6 14.2 months and found that placing a crown on a molar doubled the risk of chipping (hazard ratio 2.15, p 5 0.034).…”

ADM guidance-Ceramics: all-ceramic multilayer interfaces in dentistry

“…Similarly, Moraguez et al classified the chipping of the veneering ceramic on zirconia and alumina into critical and non-critical. A critical fracture was defined as an irretrievable loss of morphology whereas non-critical meant a fracture that did not compromise esthetics or function [62]. For single-unit crowns, the Kaplan-Meier survival estimates for critical fractures (all veneering ceramic failures) were 89.4% for an observation time of 6.3 years (mean 3.88 years).…”

Survival Predictions of Ceramic Crowns Using Statistical Fracture Mechanics

“…The application of fractographic analysis to determine the fracture origins of crowns that have failed in service has been reported in numerous publications (Kelly et al 1990; Thompson et al 1994;Quinn et al 2005;Øilo and Gjerdet 2013;Moráguez et al 2015;Øilo and Quinn 2016). These analyses identified a number of fatigue fracture modes and the mechanisms that lead to these failures are well summarized (Zhang et al 2013).…”

“…These analyses identified a number of fatigue fracture modes and the mechanisms that lead to these failures are well summarized (Zhang et al 2013). Fractures of the outer porcelain layer resulting from contact fatigue with opposing teeth have been observed in some failed crown specimens (Moráguez et al 2015;Sailer et al 2015). The application of monolithic ceramic structures reduces or eliminates the potential for failures associated with porcelain layering.…”