Whisker‐reinforced dental core buildup composites: Effect of filler level on mechanical properties

Abstract

The strength and toughness of dental core buildup composites in large stress-bearing restorations need to be improved to reduce the incidence of fracture due to stresses from chewing and clenching. The aims of the present study were to develop novel core buildup composites reinforced with ceramic whiskers, to examine the effect of filler level, and to investigate the reinforcement mechanisms. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whisker surface for improved retention in the matrix. Filler level was varied from 0 to 70%. Flexural strength, compressive strength, and fracture toughness of the composites were measured. A nanoindentation system was used to measure elastic modulus and hardness. Scanning electron microscopy (SEM) was used to examine the fracture surfaces of specimens. Whisker filler level had significant effects on composite properties. The flexural strength in MPa (mean ± SD; n = 6) increased from (95 ± 15) for the unfilled resin to (193 ± 8) for the composite with 50% filler level, then slightly decreased to (176 ± 12) at 70% filler level. The compressive strength increased from (149 ± 33) for the unfilled resin to (282 ± 48) at 10% filler level, and remained equivalent from 10 to 70% filler level. Both the modulus and hardness increased monotonically with filler level. In conclusion, silica particle-fused ceramic single-crystalline whiskers significantly reinforced dental core buildup composites. The reinforcement mechanisms appeared to be crack deflection and bridging by the whiskers. Whisker filler level had significant effects on the flexural strength, compressive strength, elastic modulus, and hardness of composites.

The reinforcement effect of nano and microfillers on fracture toughness of two provisional resin materials

“…The fracture toughness of two popular commercial core build-up composites have been reported to be 0.9 and 1.15 MPa m 1/2 [20]. According to Jandt et al [21], a clinically relevant fracture toughness value may be based on the fracture toughness of natural mineralized tissues.…”

Effects of incorporating nanosized calcium phosphate particles on properties of whisker‐reinforced dental composites

“…34 (3) Core-buildup composites possessed flexural strengths of 97-120 MPa. 35 (4) A glass fiber-reinforced composite had a flexural strength of 110 6 10 MPa. (Jeneric/Pentron manufacturer's data is available at www.jeneric.com.)…”

Whisker-reinforced bioactive composites containing calcium phosphate cement fillers: Effects of filler ratio and surface treatments on mechanical properties

“…40,43,45 The specimens were tested in air at a relative humidity of approximately 40% and a temperature of 22°C. The flexural strength, flexural modulus, and work-of-fracture (the energy required to fracture the specimen, obtained from the area under the load-displacement curve divided by the specimen's cross-sectional area) were measured.…”

“…20,22,24 Recent studies have used ceramic whiskers to reinforce Bis-GMA-based dental resin composites to extend their use to large stress-bearing restorations. [39][40][41][42][43] The whiskers possess a high structural perfection and hence superior strength values. 39,40 In pilot studies, the whiskers were mixed with silica particles as fillers for reinforcement, resulting in novel composites with strength and toughness substantially higher than the currently available dental resin composites.…”

“…39,40 In pilot studies, the whiskers were mixed with silica particles as fillers for reinforcement, resulting in novel composites with strength and toughness substantially higher than the currently available dental resin composites. [40][41][42][43] However, the whiskers have not been coupled with bioactive fillers for the development of strong and bioactive composites.…”