All ETDs from UAB

Advisory Committee Chair

Nathaniel Lawson

Advisory Committee Members

Daniel Givan

Perng-Ru Liu

Keith Kinderknecht

Document Type

Thesis

Date of Award

2018

Degree Name by School

Master of Science in Dentistry (MScD) School of Dentistry

Abstract

ABSTRACT Objectives: To measure and compare crown fracture load of a new translucent zirconia. Methods: 72 Standarized crown preparations were designed with AutoCAD software with a 0.8mm shoulder margin and 1 mm incisal-cervical marginal curvature. A stylized crown with a 1mm thickness and 0.8mm minimum thickness in the central pit was designed in 3shape software. Tooth dies were milled out of a resin composite (Crystal Ultra) that has a similar modulus as dentin (Modulus 10 GPa). Crowns were fabricated and prepared into the following groups: 24 crowns of translucent zirconia (Lava Esthetic, 3M), 8 bonded with resin cement (Group 1), 8 alumina particle abraded bonded with a resin cement (Group 4) and 8 cemented with resin-modified glass ionomer (Group 7); 24 crowns out of traditional zirconia (Lava Plus, 3M) 8 bonded with resin cement (Group 2), 8 alumina particle abraded bonded with a resin cement (Group 5) and 8 cemented with resin-modified glass ionomer (Group 8); 24 crowns out of lithium disilicate (e.max CAD, Ivoclar Vivadent), 8 bonded with resin cement (Group 3), 8 etched with 5% hydrofluoric acid and silane application bonded with a resin cement (Group 6) and 8 cemented with resin-modified glass ionomer (Group 9). All the crowns were load cycled for 100,000 cycles at 100 N force in a custom fatigue device. Specimens were loaded against a stainless steel ball that made contact with the stylized crowns on each of the four cusps. All fatiguing was performed in 24 C water. The crowns were then fractured in a universal testing machine (MTS). The load was applied with a stainless steel indenter (7mm radius) with a loading rate of 1 mm/min. A 1.5mm rubber sheet was placed between the indenter and the crown to be distributed the load and simulate a food bolus. Results: Lava Plus bonded with self-adhesive resin cement (Group 2) showed the highest values 5383.5 +/- 713.0, followed by Lava Plus with sandblast treatment and bonded with a self-adhesive resin cement (Group 5) 5272.2 +/- 383.2. The lowest value was shown by Lava Esthetic cemented with a RMGI (Group 7) 3007.4 +/- 320.8c. The crowns milled out of e.max CAD (Group 9) failed the during the load cycle test. Conclusions: The strength of Lava Esthetic and e.max CAD are about 2/3 that of Lava Plus when bonded with a resin cement. All materials are strengthened when bonded with a resin cement. When bonded with a resin cement, Lava Esthetic is not weakened with sandblasting. When cemented with a RMGI cement, Lava Esthetic shows a lower fatigue resistance when sandblasted than when sandblasting is omitted. When cemented with a RMGI cement, Lava Esthetic showed a better fatigue resistance than e.max CAD.

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