J Adv Prosthodont.  2016 Dec;8(6):489-493. 10.4047/jap.2016.8.6.489.

A comparison of the fracture resistances of endodontically treated mandibular premolars restored with endocrowns and glass fiber post-core retained conventional crowns

• Guo J
• Wang Z
• Li X
• Sun C
• Gao E
• Li H

• KMID: 2382595
• DOI: http://doi.org/10.4047/jap.2016.8.6.489

Abstract

PURPOSE
This in-vitro study aimed to evaluate the fracture resistances and failure modes of endodontically treated mandibular premolars restored with endocrowns and conventional post-core retained crowns.
MATERIALS AND METHODS
Thirty mandibular premolars were assigned into three groups (n=10): GI, intact teeth; GE, teeth with endocrowns; GC, teeth with conventional post-core supported crowns. Except for the teeth in group GI, all specimens were cut to 1.5 mm above the cementoenamel junction and endodontically treated. Both endocrowns and conventional crowns were fabricated from lithium-disilicate blocks using a CEREC 3D CAD/CAM unit. All specimens were subjected to thermocycling and then to 45° oblique compressive load until fracture occurred. The fracture resistance and failure mode of each specimen were recorded. Data were analyzed with one-way ANOVA and LSD Post Hoc Test (α=.05).
RESULTS
The fracture resistances of GE and GC were significantly lower than that of GI (P<.01), while no significant difference was found between GE and GC (P=.702). As of the failure mode, most of the specimens in GE and GC were unfavorable while a higher occurrence of favorable failure mode was presented in GI.
CONCLUSION
For the restoration of mandibular premolar, endocrown shows no advantage in fracture resistance when compared with the conventional method. Both of the two methods cannot rehabilitate endodontically treated teeth with the same fracture resistances that intact mandibular premolars have.

Keyword

Endocrown; Mandibular premolar; Intact tooth; Fracture resistance; Failure mode

MeSH Terms

Bicuspid*
Crowns*
Glass*
Lysergic Acid Diethylamide
Methods
Tooth
Tooth Cervix
Lysergic Acid Diethylamide

Figure

• 

  Fig. 1 Schematic representation of the tooth preparation. Schematic representation of the tooth preparation. (A) Group GE: endocrown preparation: the depth of central retention cavity was 5 mm from the cervical margin, margin width was 2 mm; (B) Group GC: conventional preparation with core height of 3 mm, height ferrule of 1.5 mm, shoulder width of 1 mm, and apical sealing of 5 mm.

• 

  Fig. 2 Scheme of the fracture resistance test for the specimen.

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