The effect of zirconia framework design on the failure of all-ceramic crown under static loading

Abstract

PURPOSEThis in vitro study aimed to compare the failure load and failure characteristics of two different zirconia framework designs of premolar crowns when subjected to static loading.MATERIALS AND METHODSTwo types of zirconia frameworks, conventional 0.5 mm even thickness framework design (EV) and 0.8 mm cutback of full contour crown anatomy design (CB), were made for 10 samples each. The veneer porcelain was added on under polycarbonate shell crown made by vacuum of full contour crown to obtain the same total thickness of the experiment crowns. The crowns were cemented onto the Cobalt-Chromium die. The dies were tilted 45 degrees from the vertical plane to obtain the shear force to the cusp when loading. All crowns were loaded at the lingual incline of the buccal cusp until fracture using a universal testing machine with cross-head speed 0.5 mm/min. The load to fracture values (N) was recorded and statistically analyzed by independent sample t-test.RESULTSThe mean and standard deviations of the failure load were 1,170.1 ± 90.9 N for EV design and 1,450.4 ± 175.7 N for CB design. A significant difference in the compressive failure load was found (P<.05). For the failure characteristic, the EV design was found only cohesive failures within veneering porcelain, while the CB design found more failures through the zirconia framework (8 from 10 samples).CONCLUSIONThere was a significant difference in the failure load between two designs, and the design of the framework influences failure characteristic of zirconia crown.

Veneered Zirconia‐Based Restorations Fracture Resistance Analysis

“…In previous studies, zirconia‐based restorations have recorded a wide range of single cycle load to failure (346 to 6263 N). This can be attributed primarily to the variability of loading protocols including: the abutment material, the luting cement, the diameter of the loading indenter, and the loading angle . In the present study, zirconia‐based crowns recorded relatively low mean failure load values (638 to 1200 N) compared with previous studies.…”

Effect of screw access hole design on the fracture resistance of implant‐supported zirconia‐based restorations

“…Urapepon and Taenguthai evaluated the fracture resistance of zirconia‐based crown with two designs including conventional 0.5 mm even thickness framework design, and 0.8 mm cutback of full‐contour‐crown anatomic design and showed a higher fracture resistance for the crowns with anatomic design. Accordingly, in the current investigation all crowns had the anatomic design.…”

“…Silicon putty indexes (Speedex, Coltène, Altstatten, Switzerland) were molded to the wax patterns to be used as guides for veneering porcelain application. The wax patterns were cut back (0.8 ± 0.02 mm) to create and an even thickness for the veneering porcelain and an anatomic design for zirconia frameworks . The wax patterns were formed according to intended designs for the studied groups.…”

Assessment of All-Ceramic Dental Restorations Behavior by Development of Simulation-Based Experimental Methods

“…The main reason for zirconia restoration failures is veneering ceramic fracture and chipping. These are caused by an inappropriate framework design, which cannot provide a proper support and thickness for porcelain veneer layer [10][11][12].…”

“…The improvement of the framework design, by creating an appropriate support, allows a proper thickness of the veneer proved to reduce the chipping rates [16]. The cutback design of the zirconia framework for all-ceramic crowns is thus a promising way to reduce veneer chipping failures [10].…”