Effect of connector height and retainer occlusal thickness on the fracture resistance of posterior 4-unit monolithic 5Y-TZP fixed partial dentures after thermomechanical aging

The connector height and retainer occlusal thickness of fixed partial dentures (FPDs) may affect restoration longevity. The purpose of this in vitro study was to determine and compare the fracture resistance of 4-unit monolithic 5% yttria tetragonal zirconia polycrystal (5Y-TZP) FPDs made with diffe...

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Bibliographic Details
Published in:The Journal of prosthetic dentistry 2024-05, Vol.131 (5), p.933.e1-933.e7
Main Authors: ElShamoty, Yousef Khaled, Sadeqi, Haneen Adnan, Baig, Mirza Rustum
Format: Article
Language:English
Subjects:
Dental Abutments
Dental Materials - chemistry
Dental Restoration Failure
Dental Stress Analysis
Denture Design
Denture, Partial, Fixed
Humans
In Vitro Techniques
Materials Testing
Yttrium - chemistry
Zirconium - chemistry
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Summary:The connector height and retainer occlusal thickness of fixed partial dentures (FPDs) may affect restoration longevity. The purpose of this in vitro study was to determine and compare the fracture resistance of 4-unit monolithic 5% yttria tetragonal zirconia polycrystal (5Y-TZP) FPDs made with different connector heights and retainer occlusal thicknesses after thermomechanical aging. Forty test metal dies were duplicated from a master metal die containing 2 anatomic abutment preparations of the mandibular right first premolar and second molar for a 4-unit FPD. The dies were divided into 2 groups of 20 each for the fabrication of 4-unit FPDs, with 2-mm and 4-mm uniform connector heights at all 3 connectors, resulting in 6.3-mm2 and 12.6-mm2 connector areas. Each of these groups was further divided into 2 subgroups based on the occlusal thickness of the 2 retainers of 1 mm and 2 mm (n=10). Polyvinyl siloxane impressions of the test metal dies were made and poured in Type V dental stone. Laboratory scans were performed on all the stone dies, and 40 5Y-TZP FPDs (Ceramill Zolid FX) were designed and fabricated. Subsequently, all the FPDs were luted on to the metal dies with a self-adhesive resin cement. The FPDs were preloaded (400 000 mechanical cycles; 4000 thermocycles) using a mastication simulator and tested for axial compressive strength. Two-way analysis of variance (ANOVA) was used to examine the effect of connector and occlusal thicknesses on the fracture load (α=.05). The data were further assessed using the post hoc Tukey HSD multiple comparison test (α=.05). The mean fracture load values were between 737 N and 1563 N. Significant differences in the mean fracture load were found between the connector heights (601 N; P
ISSN:0022-3913
1097-6841
DOI:10.1016/j.prosdent.2024.01.033