Abstract
Objective: To evaluate the effect of different occlusal preparation designs and CAD/CAM materials on the fracture resistance of maxillary premolars endcrowns. Materials and Methods: sixty-four endodontically treated upper first premolars were randomly divided into four groups according to ceramic materials (Vita Enamic and IPS emax CAD) and occlusal preparation designs (Anatomical and horizontal butt joint). After teeth preparation, the restorations were all made by CAD/CAM system (Cerec MCXL). Half of each group had undergone cyclic fatigue testing of 105 cycles with 50N loading force at a frequency of 0.5Hz in a mechatronic chewing simulator machine, and then all samples were loaded to fracture using a universal testing machine with a cross head speed of 0.5mm/min recording the fracture resistance values in N . The specimens were measured and statistically analyzed using using three-way analyses of variance (ANOVA), followed by serial two-way and one-way ANOVAs at each level of the study. P-values were adjusted for multiple comparisons using BENFORRONI correction and the significance level was set at P ? 0.05 for all tests. Results: Vita Enamic endocrowns showed higher fracture resistance values than IPS e max specimens. Conclusions: Vita Enamic endocrowns with anatomical preparations were found to be more favourable restoring endodontically treated maxillary premolars. KEYWORDSEndocrowns; All-Ceramic; Fracture; Cyclic loading; CAD/CAM
Highlights
Restoring endodontically treated teeth continues to be a challenge in reconstructive dentistry
The purpose of this study was to assess the effect of two CAD/CAM materials:(Lithium disilicate ceramic and Polymer infiltrated ceramic network, two occlusal preparation designs
While for aged samples, only type of material had a significant effect on fracture resistance with Vita Enamic (775.06 ± 71.61) having a significantly higher value than Emax samples (710.91 ± 48.22) (p = 0.014)
Summary
Restoring endodontically treated teeth continues to be a challenge in reconstructive dentistry. Endocrowns have been proved by many authors to be a viable restorative alternative to conventional crowns for endodontically treated molars [1,2]. The endocrown is a “one-piece ceramic construction comprising a circumferential butt margin and a central retention cavity inside the pulp chamber and constructs both the crown and core as a single unit”. The main advantages of such approach are utilizing the available surface in the pulp chamber to improve retention through adhesive bonding in addition to conservatism by following the concept of decay-orientated design [3,4]. Cusp elongation in maxillary premolars due to pulp chamber deroofing in the process of endodontic access cavity preparation tends to separate the buccal and palatal cusps under occlusal load [9]
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