Objectives . Lucirin-TPO (L) has been introduced in some dental resin composites for aesthetic reasons as well as to increase polymerization efficiency. However, its efficiency and potential use in photoactive resin composites has not been fully described. The aim of the present work was to compare the polymerization efficiency of L with the commonly used camphorquinone/amine (CQ) photoinitiation system and to assess its potential to allow reduction of curing time.

Materials and methods . A 50/50 wt% Bis-GMA/TEGDMA resin was prepared with two equimolar photoinitiator contents: CQ/DMAEMA (0.20/0.80 wt%) or L (0.42 wt%). Resins were tested either unfilled (U) or loaded (F) with silanated fillers (0.7 μm) and fumed silica (40 nm) to 65/10 wt%, respectively. Specimens were cured in a cylindrical Teflon mould (12 × 1.4 mm) with a halogen Swiss Master Light (EMS, Switzerland), chosen for specific spectral emission/photoinitiator absorption characteristics. Three different curing protocols were applied: 3000 mW/cm ² for 3 s (9 J/cm ² ), 3000 mW/cm ² for 6 s (18 J/cm ² ) and 400 mW/cm ² for 45 s (18 J/cm ² ) as the reference regimen. Degree of conversion (DC) and curing kinetics were analyzed by FT-NIRS in real time for 70 s.

Results

Material	400 mW/cm 2 – 45 s (18 J/cm 2 )			3000 mW/cm 2 – 6 s (18 J/cm 2 )			3000 mW/cm 2 – 3 s (9 J/cm 2 )
	DC (±sd) (%)	Rmaxp R p max (s −1 )	Time to Rmaxp R p max (s)	DC (±sd) (%)	Rmaxp R p max (s −1 )	Time to Rmaxp R p max (s)	DC (±sd) (%)	Rmaxp R p max (s −1 )	Time to Rmaxp R p max (s)
UCQ	72 (0.7) 1,b	0.024	21.9	44 (1.4) 2,d	0.040	7.7	26 (1.3) 3,d	0.027	4.6
FCQ	58 (0.7) 1,d	0.021	14.2	51 (0.2) 2,c	0.056	6.6	33 (1.0) 3,c	0.042	4.3
UL	76 (0.1) 3,a	0.058	10.1	85 (0.3) 1,a	0.186	3.8	82 (0.2) 2,a	0.173	4.1
FL	63 (0.5) 2,c	0.027	8.9	68 (0.3) 1,b	0.103	4.6	59 (1.7) 3,b	0.108	4.0

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