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Updated: Dec 2, 2025

Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives
Published on: May 17, 2020
Influence of beam homogenization on bond strength of adhesives to dentin
Jorge Soto-Montero1, Gabriel Nima2, Carlos T S Dias3
1Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, Avenida Limeira 901, 13414-903 Piracicaba, SP, Brazil; Department of Restorative Dentistry, Faculty of Dentistry, University of Costa Rica, Instalaciones Deportivas, 11501-2060, Montes de Oca, San José, Costa Rica.
Objective:
This study evaluated the effect of beam homogeneity on the microtensile bond strength (μTBS) of two adhesive resins to dentin.
Methods:
One polywave light-emitting-diode (LED) LCU (Bluephase Style, Ivoclar Vivadent AG) was used with two different light guides: a regular tip (RT, 1010 mW/cm2 emittance) and a homogenizer tip (HT, 946 mW/cm2 emittance). The emission spectra and beam profiles were measured from both light guides. Extracted third molars were prepared for μTBS evaluation using two adhesive systems: Excite F (EXF) and Adhese Universal (ADU). Bond strength was calculated for each specimen (n = 10) at locations that correlated with the output of the two LED chips emitting blue (455 nm) and the one chip that emitted violet light (409 nm) after 24-hs and after one-year water-storage. The μTBS was analyzed using a four-way analysis of variance (factors: adhesive system, light guide, LED wavelength, and storage time) and post-hoc Tukey test (α = 0.05).
Results:
EXF always delivered a higher μTBS than ADU (p < 0.0001), with the μTBS of ADU being about 20% lower than EXF. The light guide (p = 0.0259) and storage time (p = 0.0009) significantly influenced the μTBS. The LED wavelengths had no influence on the μTBS (p > 0.05).
Significance:
Homogeneity of the emitted light beam was associated with higher 24-h μTBS to dentin, regardless of the adhesive tested. Also, differences in the composition of adhesives can affect their compatibility with restorative composites and their ability to maintain bonding over one year.
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