An in vitro comparison of fractural strength of zirconia custom abutments with different angulations and thicknesses.
Abstract: Statement of the problem: The strength of zirconia custom abutments could be affected by the thickness of the abutments¡¦ walls and/or abutments¡¦ angulations, leading to internal stress build-up, and consequently affecting restoration¡¦s life-span. Purpose: The purpose of this in vitro study was to compare the fractural strength of zirconia custom abutments with different thicknesses ... read moreand angulations. Materials and methods: Eighty zirconia custom abutments were divided into two main groups (group I & group II). Each group was divided further into four subgroups. Groups I-A-1, I-B-1, II-A-1, and II-B-1 simulated a clinical situation with an ideal implant position from a prosthetic point of view, which allows for the use of a straight zirconia custom abutments with two different thicknesses (.7 mm and 1 mm). Whereas groups I-A-2, I-B-2, II-A-2, and II-B-2 Simulated a situation with a compromised implant position requiring 15 degree angulated abutments with different thicknesses (.7 mm and 1 mm). Implant replicas were placed in cubic self cure acrylic jigs to support the abutments in all groups. The zirconia custom abutments were engaged to the implant replicas into the cubic acrylic jigs by using a manual torque wrench. Each jig was secured and mounted in metallic vice. All groups were subjected to shear stress till failure with a crosshead speed of .5 mm/min with the force transferred to the lingual surface of the zirconia custom abutments 2 mm below the incisal edge by using universal testing machine. The universal testing machine was controlled via a computer software system which also completed the stress-strain diagram and recorded the breaking fractural strength. Results: The mean fractural strength of zirconia custom abutments in group I (A-1 through B-2) ranged from 162.49 ¡Ó 63.21 N to 231.14 ¡Ó 95.21 N, whereas in group II (A-I through B-2) ranged from 431.83 ¡Ó 96.74 N to 745.93 ¡Ó 274.79 N. Group II-B-2 exhibited the highest fractural strength among all the groups, which was statistically significant p= .005. Conclusions: ,,X Zirconia custom abutments in group II exhibited the highest fractural strength especially with angulated abutments. ,,X Zirconia custom abutments in group I exhibited the lowest fractural strength especially the angulated abutments. ,,X The thickness of zirconia custom abutments in group II had a positive influence on the fractural strength, but in group I had no influence.
Thesis (M.S.)--Tufts University, 2012.
Submitted to the Dept. of Posthodontics.
Advisor: Roya Zandparsa.
Keyword: Dentistry.read less