Effect of light curing units on marginal adaptation and hardness of Class II composite resin restorations.
OBJECTIVE
The aim of this study was to test the influence of different curing protocols on dentin marginal adaptation and the hardness of two composites.


METHODS
Three light-curing-units (LCUs): Quartz-Tungsten-Halogen (QTH: 541 mW/cm2), Argon-Ion-Laser (AL: 277 mW/cm2), and Plasma-Arc-Curing (PAC: 1818 mW/cm2) and two composites FiltekZ250 (F) and Tetric Ceram HB (TC) were tested. Sixty standardized "vertical-slot-Class II-cavities" were prepared at the mesial surface of bovine incisors and divided into six groups (n=10). Composites were placed using the Single Bond adhesive system and cured in 2 mm increments according to the manufacturers' instructions. After polishing, epoxy replicas were processed for scanning electron microscopy (SEM) marginal adaptation analysis at 500x magnification. The specimens were then sectioned transversally to the dental long axis, embedded in polyester resin, then polished and submitted to the Knoop hardness test at gingival and occlusal portions of the restoration. Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's test (p=0.05).


RESULTS
The gap margins ranged between 4.3 to 5.8 microm, and no statistically significant differences were revealed in marginal adaptation for LCUs or for composites (p>0.05). Location influenced hardness (p=0.01). The occlusal portion presented significantly higher KHN than the gingival portion for all composite-LCU combinations. Regardless of the LCU used, TC produced statistically significant lower hardness values (ranging between 82.8 to 110.7 KHN) than F (ranging between 105.9 to 117.3 KHN).


CONCLUSIONS
Hardness and gap formation were not dependent on the LCUs tested in this study. Different resin composite was found to be a significant factor with regards to hardness but not gap formation.
Cavalcante
Larissa Maria
LM
Department of Restorative Dentistry Clinical Dentistry, Piracicaba School of Dentistry, University of Campinas, Piracicaba, SP, Brazil. lara_cavalcante@yahoo.com.br
Peris
Alessandra Resende
AR
Silikas
Nick
N
Pimenta
Luiz André Freire
LA
D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000528:radiation effects*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000145:classification / Q000379:methods; D006219:Halogens; D006244:Hardness / Q000528:radiation effects; D054020:Lasers, Gas; D008027:Light; D044367:Phase Transition; D011897:Random Allocation; D018709:Statistics, Nonparametric; D014978:Xenon
D003188:Composite Resins; C444701:Filtek Z250; D006219:Halogens; C121818:Tetric ceram; D014978:Xenon