In- vitro Wear of Four CAD- CAM Materials in the UAB Wear Simulating Device

• Main Author: Bansal, Ritika
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01.01.2015
• Subjects: Dentistry
• ISBN: 1321994087; 9781321994087

Hybrid ceramic/polymer blocks represent a new category of CAD/CAM materials that do not require heat treatment following milled fabrication and limited clinically relevant mechanical properties of these materials are available. Purpose: This study measures the hardness, flexural strength, modulus, and wear of 3 ceramic/polymer hybrid materials (LAVA Ultimate, Enamic, and Cerasmart), 2 reference glass ceramics (IPS e.max and Celtra Duo), and 1 reference composite material (Paradigm MZ100). Methods: Flexural strength specimens (n=10) (2.5 × 2.5 × 16 mm) were prepared using a sectioning saw. After 24 hours in aqueous storage (37ºC), the specimens were loaded to failure at 1 mm/min. Microhardness specimens (n=2) (2 mm thick) were prepared by a sectioning saw. After mounting and polishing, the specimens were stored in water for 24 hours (37ºC). Five indentations were made in each specimen with a Berkovich indentor using 1 kgF and 15 seconds dwell time. Indentations were measured with a digital microscope. Wear speciemns (n=8) (2 mm thick) were sectioned, mounted, polished, and stored in water for 24 hours. Wear specimens were positioned in the UAB wear device opposite mounted cusps of extracted human premolars. The device produced 20N force at 1 Hz for 400,000 cycles using a 33% glycerine lubricant which was circulated. Following wear simulation, the volumetric wear of the specimens and opposing enamel was measured with a non-contact profilometer. Results: All of the ceramic/polymer hybrid materials showed a significantly lower flexural strength than lithium disilicate glass ceramic. The two nano-filled hybrid materials (Cerasmart and LavaUltimate) showed statistically similar flexural strength values. The flexural strength of Enamic was nominally lower than Cerasmart and Lava Ultimate. Celtra Duo was found to have significantly greater flexural strength following heat treatment.All of the resin-based materials (Paradigm MZ100, Cerasmart, and LAVA Ultimate) demonstrated lower modulus than the predominantly ceramic materials. Cerasmart showed a nominally lower modulus of elasticity than LAVA Ultimate, while Enamic showed a higher modulus than the other resin-containing materials. Paradigm MZ100, Cerasmart, and LAVA Ultimate showed lower hardness than the predominantly ceramic materials. Enamic behaved intermediate to a ceramic material and resin-based hybrid material. The hybrid materials demonstrated less material wear and less opposing enamel wear than lithium disilicate. Conclusions: Ceramic/polymer materials showed lower flexural strength (Paradigm MZ100- 189.7 ± 28.2, Cerasmart- 234.5 ± 24.8, LAVA Ultimate- 248.4 ± 24.5, Enamic- 202.1 ± 17.9) than the commonly used lithium disilicate material (IPS e.max CAD- 376.9 ± 76.2). The flexural strength of Celtra Duo (Celtra Duo- 300.1 ± 16.8) significantly improved with the heat treatment (Celtra Duo fired- 451.4 ± 58.9). Resin-based hybrid materials (Lava Ultimate and Cerasmart) showed a lower modulus (Cerasmart- 12,122 ± 750, LAVA Ultimate- 16,013 ± 4,586) than mostly ceramic materials (IPS e.max CAD- 37,157 ± 275). Enamic had a higher modulus (Enamic- 21,549 ± 1,593) than the other hybrid materials (Paradigm MZ100- 14,128 ± 854, Cerasmart- 12,122 ± 750, LAVA Ultimate- 16,013 ± 4,586). All of the resin-based materials (Paradigm MZ100- 103.49 ± 3.21, Cerasmart- 63.25 ± 10.99, and LAVA Ultimate- 102.26 ± 14.52) demonstrated lower hardness than the predominantly ceramic materials (IPS e.max CAD- 452.94 ± 16.21). Cerasmart showed the lowest hardness values (Cerasmart- 63.25 ± 10.99). Enamic (157.58 ± 13.94) behaved intermediate to a ceramic material and resin-based hybrid material achieving a relatively higher hardness value than other resin-based materials. The hybrid materials showed less material wear (Paradigm MZ100- 0.182±0.06, Cerasmart- 0.196±0.09, and LAVA Ultimate- 0.152±0.04) and less opposing enamel wear (Paradigm MZ100- 0.133±0.08, Cerasmart- 0.054±0.02, and LAVA Ultimate- 0.066±0.027) than lithium disilicate (IPS e.max CAD- 0.289±0.08 and 0.469±0.12). The hybrid materials demonstrated more fatigue wear and the lithium disilicate experienced abrasive wear.