OCT-assessment of Etching Protocols of a Universal Adhesive In Vivo

Objectives: To assess the initial quality of restorations of non-carious cervical lesions and the composite-tooth bond by optical coherence tomography (OCT) in vivo.
Methods: 22 patients with four non-carious cervical lesions each received composite restorations (Filtek Supreme^TM XTE, 3M Espe). The universal adhesive Scotchbond Universal^TM (SBU; 3M Espe) was applied with three different etching protocols: self-etch (SE), selective-enamel-etch (SEE) and total-etch with phosphoric acid (TE). One group restored with the etch-and-rinse adhesive OptiBond^TM FL (OFL; Kerr) served as a control. The fillings were imaged by spectral domain OCT (Telesto II, Thorlabs, 1310nm) directly after application (t₀). After 14 days (t₁) OCT imaging was repeated together with a clinical assessment (Hickel et al., 2007). Per restoration 25 equally distributed B-scans were examined out of 200-400 per OCT-image stack. The signal indicating “adhesive defect” at the enamel/dentin/cement-composite interface was quantified (length, %; Park et al. 2013). Groups were statistically compared by McNemar and Friedman-/Wilcoxon-Test (a=0.05).
Results: The clinical criteria showed no differences between groups (t₁). OCT assessment revealed more adhesive defects at the enamel interface with SBU/SE at t₀ and t₁ compared to all other groups (p_i ≤ 0.016). At t₁ OFL showed more defects than SBU/TE (p = 0.01). At the dentin and cementum interface OFL exhibited more adhesive defects than SBU in all etching modes (p_i ≤ 0.003). At t₁ adhesive defects with SBU were detected more frequently in the SE and SEE modes compared to TE (p_i ≤ 0.037).
Conclusions: In contrast to clinical evaluation OCT already revealed differences in the tooth composite bond directly after application of the restoration. Phosphoric acid etching does not decrease the initial adhesion of SBU to dentin. Prospective clinical relevance of these initial findings has to be verified during the further course of this clinical study.