In vitro assessment of polymerization procedures in Class II restorations: sealing, FTIR, and microhardness evaluations.
OBJECTIVE
This study was undertaken to evaluate several polymerization and filling procedures (incremental, bulk, light-tip, soft-cured, plasma devices) in Class II restorations through (1) a sealing evaluation of restorations filled with Tetric Ceram (TC) and Bisfil 2B (B2B, self-cured composite used as a control), (2) a FTIR analysis measuring the variations of the degree of conversion in terms of area unit ratio of the relevant resin composites and (3) a microhardness test to corroborate the FTIR analysis.


METHODS
The length of the tracer penetration was measured from the gingival margin up to the cavity wall with an episcope on sectioned teeth. A ceramic mould, simulating a Class II, was filled according to the different groups and the samples were analyzed with a Bruker IFS 55 spectrometer on ultrathin sections (3 mu). The results were analyzed in terms of area unit ratio and total exposed energy. Under the same conditions, a microhardness test was run with a Frank Weihem machine.


RESULTS
The results of the sealing evaluation for light-tip, incremental and self-cured techniques did not differ. The plasma procedure failed in this evaluation as the bottom increment was not polymerized. The smallest area unit ratio (the best degree of conversion) was observed in 2 groups: one, the combination of the light-tip and soft process, and two, the self-cured resin composite (B2B). The distance at which the plasma procedure failed to cure the resin composite was between 3.5 and 4.5 mm. The microhardness test confirmed the FTIR analysis except for the group G2 (TC + light-tip). As also shown by FTIR analysis, no difference between the two relevant levels was observed with the hardness test.


CONCLUSIONS
The dentin marginal sealing efficiency of Tetric Ceram restorations was increased with the light-tip technique, but was not better than the self-cured resin composite (B2B). For Tetric Ceram, the combination of the light-tip and soft process leads to a higher degree of conversion than the other groups. There is no linear relationship between the degree of conversion, the microhardness and the total exposed energy. The combination of the soft polymerization and the light-tip device might be an alternative restorative technique to the current incremental technique.
Tassery
H
H
Department of Operative Dentistry, UFR d'Odontologie de Marseille, Université de la Méditerranée, Marseille, France. dominique.tassery@wanadoo.fr
de Donato
P
P
Barrès
O
O
Déjou
J
J
D000179:Acrylates; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D017220:Dentin-Bonding Agents; D006245:Hardness Tests; D006801:Humans; D008027:Light; D008298:Maleates; D011108:Polymers / Q000737:chemistry; D011897:Random Allocation; D017550:Spectroscopy, Fourier Transform Infrared; D018709:Statistics, Nonparametric; D013674:Technology, Dental / Q000379:methods*
D000179:Acrylates; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008298:Maleates; D011108:Polymers; C443859:Syntac Sprint; C121818:Tetric ceram; C078905:Bisfil