Fracture resistance of cement-retained and screw-cement-retained milled posterior crowns with screw-access hole preparations before and after firing: An in vitro study
| Autor: | Jesus Enrique Cabrera, Joe C. Ontiveros, Ruben A. Sauceda, Dianna M. Arriaga, Donald M Belles |
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| Rok vydání: | 2019 |
| Předmět: |
Dental Stress Analysis
Ceramics Materials science medicine.medical_treatment Perforation (oil well) Bone Screws Dental Cements Composite Resins Crown (dentistry) 03 medical and health sciences Dental Materials 0302 clinical medicine Flexural strength Materials Testing medicine Ceramic Dental Restoration Failure Composite material Acrylic resin Universal testing machine Crowns 030206 dentistry Dental Porcelain visual_art Fracture (geology) visual_art.visual_art_medium Computer-Aided Design Oral Surgery Abutment Screw |
| Zdroj: | The Journal of prosthetic dentistry. 127(5) |
| ISSN: | 1097-6841 |
| Popis: | Statement of problem When a cement-retained lithium disilicate crown needs to be removed, perforation is needed to reach the abutment screw. How this process affects its strength is unclear. Purpose The purpose of this in vitro study was to evaluate the fracture strength of milled lithium disilicate implant crowns with screw-access holes created before and after the firing stages. Material and methods Nine implant replicas with stock abutments were embedded in acrylic resin. Forty-five lithium disilicate (IPS e.max CAD) crowns were designed, milled, and divided into groups. The control group had no screw access, the blue state group had the screw access created in the intermediate phase of the ceramic, and the postfiring group had the screw access created after firing. The crowns were cemented with a self-adhesive resin cement, placed in an incubator for 24 hours and then thermocycled. The screw-access holes were sealed with composite resin. The crowns were loaded to failure with a universal testing machine using a 1- mm-diameter ball at a crosshead speed of 0.5 mm/min and a 5-kN cell load. Data were analyzed by ANOVA and the Tukey post hoc test (α=.05). Results Screw-access holes created before and after firing stages had a significant effect on the fracture resistance of lithium disilicate crowns (P=.002). No difference in fracture resistance was observed between the control group and the blue state group (P>.05), while the fracture resistance of the postfiring group was significantly lower than that of the control group and the blue state group (P Conclusions The fracture strength of lithium disilicate crowns was not affected by a screw-access hole created during the blue state of the ceramic followed by repair with composite resin. Creating a screw-access hole after firing the ceramic reduced fracture strength. |
| Databáze: | OpenAIRE |
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