Influence of photoactivation source on restorative materials and enamel demineralization.
OBJECTIVE
The objective of this study was to evaluate the influence of the photoactivation source on the polymerization depth of restorative materials and its effects on resistance to enamel demineralization.


BACKGROUND
Argon-ion laser (AL) irradiation itself provides a reduced depth of caries lesions in sound enamel.


METHODS
Eighteen human teeth were sectioned into 36 blocks and distributed into two groups according to the respective restorative material: resin-modified glass ionomer material (RMGI) (Vitremer-3M ESPE; A3; n=18) and composite resin (CR) (Z350-3M ESPE; n=18). Each group was subdivided into three subgroups and activated by a quartz-tungsten-halogen (QTH) lamp, an AL, or a light-emitting diode (LED) (n=6). Knoop microhardness (KHN) analysis of the materials was evaluated at two different depths: 0 and 1.6 mm from the enamel surface. The blocks were thermocycled and submitted to five demineralization-remineralization cycles at 37°C. The KHN values of the enamel surface (0 mm) were evaluated. The specimens were longitudinally sectioned, and the restorative material was evaluated at a depth of 1.6 mm. Data were evaluated by two way analysis of variance (ANOVA) and Tukey tests (p<0.05). The evaluation of subsuperficial enamel demineralization by KHN analysis was conducted by seven indentations located at 100 μm from the restored cavity. Data were evaluated by three way ANOVA and Tukey tests (p<0.05).


RESULTS
Comparing the two restorative materials, the KHN values at the surface (0 mm) were greater for CR, whereas at 1.6 mm, they were greater for RMGI. In addition, there was less development of enamel demineralization around RMGI restorations than CR restorations. Moreover, there were statistically significant differences on subsuperficial enamel demineralization between the two restorative materials and between the three photoactivation methods (p<0.05); RMGI presented the highest KHN values, and QTH and AL presented the lowest.


CONCLUSIONS
The photoactivation source did not influence superficial enamel demineralization, but LED activation positively influenced the subsuperficial microhardness of enamel.
1 Department of Restorative Dentistry, School of Dentistry, Guarulhos University , São Paulo, Brazil .
Josiane Marques de Sena
JM
Popoff
José Augusto
JA
Rodrigues
Wanessa Maria De Freitas
WM
Aras
Alessandra
A
Cassoni
D003188:Composite Resins / Q000528:radiation effects; D003743:Dental Enamel / Q000528:radiation effects*; D003793:Dental Restoration, Permanent / Q000295:instrumentation*; D006801:Humans; D066298:In Vitro Techniques; D008027:Light; D055668:Photochemical Processes; D058105:Polymerization; D017001:Tooth Demineralization / Q000209:etiology*
D003188:Composite Resins