Color, Wear Resistance of Preheated Conventional and Bulk-fill Composite Resins

Objectives: To determine the effect of preheating on color stability and wear resistance of conventional versus bulk-fill composite resins.
Methods: Forty disk-shaped (10×1mm) specimens were prepared of a conventional nano-filled composite resin (Filtek Supreme Ultra-FSU, 3M) and a bulk-fill composite resin (Filtek One-FO, 3M). Another forty disks were prepared after preheating each composite type (68°C, 10 minutes). Color stability according to the CIEDE2000 was evaluated to distal water, coffee (55°C), grape juice and thermocycling (5-55°C, 30 second dwell time) storage for 1, 7 and 14 days (n=8/group). Color differences (ΔE₀₀) were compared to the 50:50% acceptability threshold (1.8). Two-body volumetric wear measurement was calculated after masticatory simulation (120000 cycles, 30 N force) via a chewing simulator (n=8/group).
Results: Preheated FSU was more color stable than FSU (P>0.05). Coffee and grape juice storage showed color changes beyond the acceptability threshold for FSU, and coffee only for preheated FSU. FO was more color stable than preheated FO in coffee and thermocycling (except for 14 days), and less stable in grape juice (P>0.05). Coffee showed color change beyond the acceptability threshold for FO and preheated FO, and grape juice (day 14) for FO. Preheated FSU is more color stable than preheated FO (P>0.05) in all mediums. While FSU was more color stable than FO in distal water (P>0.05) (Table 1). Preheating increased wear for both composite types (P>0.05). FO was more wear resistant than FSU (non- and pre-heated) (Table 2).
Conclusions: Coffee has a significant effect on the color stability of both composite types, especially bulk-fill composite resin. Bulk-fill is more resistant to wear than conventional composite resins. Preheating may increase susceptibility to wear for both composite types.