Send to

Choose Destination
See comment in PubMed Commons below
Acta Odontol Scand. 2013 Sep;71(5):1341-7. doi: 10.3109/00016357.2013.764575. Epub 2013 Feb 28.

Thermo-mechanical degradation of composite restoration photoactivated by modulated methods-a SEM study of marginal and internal gap formation.

Author information

Biomaterials, Bandeirante University of São Paulo (ANHANGUERA UNIBAN), São Paulo, SP, Brazil.



To evaluate the influence of thermal-mechanical degradation on superficial and internal gap formation of composite restorations photoactivated using modulated methods.


An experimental composite was prepared using a resin matrix containing 65wt% Bis-GMA and 35wt% TEGDMA. Camphorquinone (0.5wt%) and dimethylaminoethyl-methacrylate (0.5wt%) were dissolved in the resin as a photo-initiator system and 65wt.% silanized glass fillers were added to the matrix. Ground buccal surfaces of bovine lower incisors were used to make 160 preparations (3 mm × 3 mm × 2 mm in depth). An adhesive system (Adper Single Bond 2) was applied and the specimens were assigned into 16 groups (n = 10), according to the photoactivation method [high intensity (HI), low intensity (LI), soft-start (SS) and pulse-delay (PD)] and the degradation protocol [(control/no degradation; thermal cycling (TC); mechanical loading (ML); thermo-mechanical loading (TC+ML)]. Marginal and internal interfaces of bonded restorations were replicated in epoxy resin and analyzed by SEM. Gaps were expressed as a percentage of the total length of the margins. Data were submitted to 2-way ANOVA and Tukey's test (α = 0.05).


For the control group no significance was noted among the photoactivation methods. TC had no effect in gap formation. ML and TC+ML increased the incidence of superficial gaps for both HI and SS groups as well as increased the internal gaps for all groups.


Although photoactivation methods do not influence gap formation at first, composite restoration photoactivated by low intensity or modulated methods showed improved resistance to thermo-mechanical degradation. Mechanical loading is determinant for interfacial degradation of composite restorations, while thermal cycling has no effect on gap formation.

[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Taylor & Francis
    Loading ...
    Support Center