Preparation time and surface roughness of core foundation resins and dentin

It is unclear if the preparation of core foundation resins is similar to that of dentin.

The purpose of this in vitro study was to compare the preparation time and resulting roughness of 5 core foundation resins and dentin.

Standardized preparations (10 mm length, 5 mm height) were made of 5 specimens of 5 core materials with a device-mounted dental handpiece (150 000 rpm, water-cooling) with weight-controlled contact pressure (50 g). To assess the cutting time of 100 μm grit cylindrical diamond rotary cutting instruments, 2 mm and 4 mm depths were cut 3 times (n=15). Afterwards surface roughness Ra and Rz were measured. Blocks of dentin were used as a control. Both preparation time and surface roughness data were statistically analyzed (1-way ANOVA, Scheffé correction, α=.05).

The average preparation times for dentin were 7 seconds for a 2 mm preparation depth and 22 seconds for a 4 mm depth with an average Ra of 5.4 μm or Rz of 30 μm. For a 4 mm depth, preparation times for Build-It, Rebilda LC, and Ti-Core ranged from 24 to 27 seconds. The preparation times of these 3 core foundation materials did not differ significantly from dentin for a 4 mm depth. The results of Core Paste and Luxacore were significantly lower (10 and 11 seconds, P<.001). For a 2 mm cutting depth, Core Paste and Luxacore showed similar preparation times compared to dentin (7 seconds, P>.05). Build-It (12 seconds) and Rebilda LC (10 seconds) showed greater preparation times compared to dentin, whereas Ti-Core preparation (5 seconds) was less. ANOVA revealed significantly lower Ra (5.0 μm) and Rz values (23-26 μm) after preparation of Core Paste, Luxacore, and Ti-Core than those of dentin (P<.05).

The preparation times of only some core foundation materials were comparable to dentin. Regarding the cutting depths, different materials provided a dentin-like preparation ability. The surface roughness values of core resins were comparable with or significantly lower than those of dentin.