Objectives: Aim of this  study was to evaluate the monomer conversion of post luting cements and the real efficacy of different mechanisms of polymerization in various depths (1 mm, 4 mm, 7 mm) along post surface, analysing how curing lamp power and exposure time could influence these data. Materials and Methods: Twenty- four translucent posts were luted (FRC Postec Plus, Ivoclar Vivadent) in an ideal standard root canal made into glass blocks. Four cementing systems were tested: Tetric Flow (Ivoclar Vivadent, light-curing material), Variolink II (Ivoclar Vivadent dual-curing material), Calibra (Dentsply, dual-curing material) and Multilink Automix (Ivoclar Vivadent, self-curing material with light-curing if needed); two polymerizing methods were used for the experiment: 60 sec. with a power of 800 mW/cm²/sec and 3000 mW/cm²/sec for 12 sec. (Swiss Master Light,EMS, Nyon, Switzerland, high-energy halogen lamp). Samples have been analysed with the technique of Micro-Raman spectrophotometry, that allows evaluating materials conversion rate, comparing the intensity variations of the aliphatic peak at 1638 cm¹ (C=C), characteristic of all materials containing Bis-Gma, in relationship to a second peak, positioned in 1608 cm¹ (the carbon single bond C-C of the aromatic ring), constant during the passage from monomer to polymer. Total data were 288 and they have been statisticaly analyzed (ANOVA and Student Newman Keuls). Results: Results have been analyzed basing on power of polymerization, materials and depht. The percentage of conversion of Bis-GMA into polymer is been evaluated for each material. Data obtained

800 mW	1 mm	4 mm	7 mm		3000 mW	1 mm	4 mm	7 mm
MULTILINK	86,8%	68%	54,9%		MULTILINK	77,4%	59,3%	53,1%
CALIBRA	83,3%	71,4%	55,3%		CALIBRA	64,8%	54%	47%
VARIOLINK II	89,2%	68,7%	32,6%		VARIOLINK II	85,6%	65,6%	31,5%
TETRIC	87,2%	44%	32,3%		TETRIC	84,1%	46,9%	24,2%

Conclusions: Our research highlights the need of a dual luting material in post cementation to guarantee an acceptable conversion rate at high depths. Better results can be achieved with less light power (800 mW/cm²/sec) increasing curing time in all experimental groups.

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