Influence of Occlusal Thickness and Radicular Extension on the Fracture Resistance of Premolar Endocrowns from Different All-Ceramic Materials

Abstract

Endocrowns are primarily recommended in a molar region with a standardized preparation design. The aim of the study was to evaluate the effect of different occlusal preparation depths, pulp chamber-radicular extension, and all-ceramic materials on the fracture resistance of premolar endocrowns. Ninety human premolar teeth were root canal treated, randomly divided into three main groups according to all-ceramic material used for fabrication as Lithium Disilicate (LD) ceramic, Polymer infiltrated ceramic (PIC) and High translucency zirconia (HTZ). They were further subdivided into three subgroups (n = 10) according to preparation design of 2 mm occlusal reduction, 4.5 mm occlusal reduction and 4.5 mm occlusal reduction with 2 mm radicular extension. The endocrowns from respective restorative materials were fabricated, surface conditioned, and cemented with self-adhesive resin cement. All samples were thermocycled for 5000 cycles and subjected to compressive static load at 45° angluation with the cross-head speed of 0.5 mm/minute until the fracture. The mean fracture resistance of LD ceramic at 2 mm, 4.5 mm thickness and radicular extension was 62.55 MPa, 45.80 MPa, 74.27 MPa respectively. The corresponding values for the PIC and HTZ ceramics were 26.30 MPa, 21.65 MPa, 25.66 Mpa and 23.47 MPa, 27.30 MPa, 37.29 MPa respectively. The LD ceramic and greater extension inside the pulp chamber had higher fracture resistance.

Comparison of retention and fracture load of endocrowns made from zirconia and zirconium lithium silicate after aging: an in vitro study

“…The seat of restorations was assessed using Vinyl Polyether Silicone (Fit checker; GC, Tokyo, Japan), and passive fit was confirmed by two impartial observers. Restorations in Zr group were prepared by air-abrasion with 50 µm alumina particles and cleaned using an ultrasonic device [ 35 ], while ZLS restorations were prepared using 9% hydrofluoric acid (Cera-Etch; Morvabon, Tehran, Iran) for 30 s and silane (Master-Dent Porcelain Primer; Dentonics, Charlotte, United States). The specimens were cemented by a dual-cure resin cement (Panavia F2.0; Kuraray, Tokyo, Japan) according to the manufacturer’s instructions.…”

Effect of Preparation Design on Marginal Integrity and Fracture Resistance of Endocrowns: A Systematic Review

“…One study was excluded due to the specimens’ type which were central theeth [ 2 ]. In addition, the references of the accepted articles were searched and 8 articles were added to the eligible full texts [ 9 , 12 , 22 - 27 ]. Therefore, 16 articles were selected for extracting the quantitative data [ 9 , 12 , 14 - 27 ].…”

“…In addition, the references of the accepted articles were searched and 8 articles were added to the eligible full texts [ 9 , 12 , 22 - 27 ]. Therefore, 16 articles were selected for extracting the quantitative data [ 9 , 12 , 14 - 27 ]. The results of data extraction for each study are presented in Table 2 .…”

“…In reviewing the preparation design for endocrown, important items include: occlusal reduction, type of finish line, cavity depth, internal divergence, presence of ferrule and intra radicular extension. Principal preparation for endocrown has been suggested as following: 2 to 3mm cuspal reduction, butt joint finish line, round internal angles, 6-degree divergence of pulpal walls, even pulpal floor with sealed radicular orifice, and supragingival enamel margins if possible[ 9 ]. However, in some cases the typical preparation could not be performed and some modifications are needed [ 10 - 12 ].…”

Comparison of Retention and Fracture Load of Endocrowns Made from Zirconia and Zirconium Lithium Silicate After Aging: An in-Vitro Study

“…The seat of restorations was assessed using Fit checker (GC, Tokyo, Japan) and the passive t of restorations was con rmed by two impartial observers. Restorations in ZLS group were prepared using 9% hydro uoric acid (Cera-Etch; Morvabon, Tehran, Iran) and silane (Master-Dent Porcelain Primer; Dentonics, Charlotte, NC) while Zr restorations were sandblasted with 50 µm alumina particles and cleaned using ultrasonic device [30]. The specimens were cemented by Panavia F2.0 (Kuraray, Tokyo, Japan) dual cure resin cement, which contains 10-MDP, according to the manufacturer's instructions.…”