Partial Ceramic Crowns: Influence of Ceramic Thickness, Preparation Design and Luting Material on Fracture Resistance and Marginal Integrity In Vitro

Abstract

SUMMARYThis in vitro study tested the effects of two different ceramic thicknesses, two preparation designs and two different luting agents on the marginal integrity and fracture resistance of partial ceramic crowns (PCC). Eighty extracted human molars were prepared according to the following preparation designs: a) Coverage of functional cusps/butt joint (n=40), b) Horizontal reduction of functional cusps (n=40). PCC (Vita Mark II, Cerec3 System) were fabricated and the ceramic thickness of the functional cusps was adjusted to 1): 0.5-1.0 mm and 2): 1.5-2.0 mm. PCC were adhesively luted to the cavities with either Excite/VariolinkII (VL) or RelyX Unicem (RX). The specimens were exposed to thermocycling and central mechanical loading (5000 x 5°C-55°C; 30 second/cycle; 50,0000 x 72.5N, 1.6Hz). For fracture resistance and the marginal integrity of adhesively bonded partial ceramic crowns (PCC), the choice of ceramic thickness and luting material are more important than preparation design. PCC fabricated from industrially sintered feldspathic ceramic should have at least a thickness of 1.5-2.0 mm in stress bearing areas. -test. Dye penetration data indicated that ceramic thickness and luting agent had a statistically significant influence upon marginal integrity in general, irrespective of all other parameters (ERM): RX showed significantly lower microleakage along the RL interface than VL. VL revealed significantly lower microleakage at the TL interface than RX. Fifteen PCC of group 1 (0.5-1.0 mm) and two PCC of group 2 (1.5-2.0 mm) were fractured after thermocycling and central mechanical loading, with the difference being statistically significant. PCC fabricated from industrially sintered feldspathic ceramic should have at least a thickness of 1.5-2.0 mm in stress-bearing areas.

Influence of material thickness on fractural strength of CAD/CAM fabricated ceramic crowns

“…There are several factors influencing the fracture resistance of ceramic restorations 5,[8][9][10] . The fracture resistance of all-ceramic restorations can be increased by an ideal combination of these factors.…”

“…The material characteristics of ceramics have been shown to significantly depend on prior thermal and mechanical fatigue loading 4) . Four factors have been identified to mainly influence the fracture resistance of all-ceramic restorations: restoration design, tooth preparation, cementation and material thickness [5][6][7][8][9] . The fracture resistance can be increased by an ideal combination of these four factors, however, the factors restoration material and material thickness have been reported to be of primary importance 10) .…”

A 3-dimensional accuracy analysis of chairside CAD/CAM milling processes

“…31,32 Larger gaps are associated with accelerated plaque accumulation, secondary caries, marginal discoloration, exposure of the luting resin, dissolution of the cement, and increased risk of microleakage and microcracks. [33][34][35] When the marginal gap is greater than 100 mm, removing excess cement is more difficult. 36 A restoration with inadequate fit may lead to marginal chipping, and even small chips can result in the later clinical failure of ceramic restorations.…”

Marginal Integrity of Partial Ceramic Crowns Within Dentin With Different Luting Techniques and Materials

“…11 No temporary restorations were applied in order to avoid possible additional influence of the temporary cement on the adhesive bond between the resin-coat or dentin and luting agent in this investigation.…”