Cause Recurrence Doesn’t Influence Nd:YAG-Irradiation Improvement on Bond-Strength to Simulated-Hypersensitive-Dentin

Objectives: Non- or minimally invasive desensitizing strategies as former treatment alternatives, as well as cause recurrence, may influence quality of the restoration of hypersensitive dentin. Thus, role of the persistence of the etiological factor on immediate and medium-term bond strength (BS) of an adhesive plus a composite to Nd:YAG laser-irradiated simulated hypersensitive dentin was evaluated.
Methods: Superficial occlusal dentin of third-molars (n=28) was submitted to a 600-grit SiC paper (1min) and to a challenge with citric acid (6%/1min; simulated hypersensitive dentin). Then, it was, or was not (C:control/n=14), irradiated with Nd:YAG laser (1.0W/10Hz/100mJ/4 irradiations of 50-60s; L:laser/n=14), and resubmitted, or not (L-/n=7; C-/n=7), to the challenge with citric acid (6%/1min; A:citric acid; LA/n=7; CA/n=7). Clearfil-SE-Bond was applied and composite buildups were constructed (Filtek Z350). After 24h (distilled water/37 C), specimens were sectioned in beams, which were tested (µTBS; 0.5mm/min) immediately (I) or after 6-months aging (6m). An extra tooth for each group was treated exactly as the others, but rhodamine-B was previously added (0.02mg/mL) to Clearfil-SE-Bond to allow a qualitative evaluation of the adhesive interface by Confocal Microscopy. BS data were analyzed by three-way ANOVA and Tukey test (α=0.05).
Results: Mean BS values (MPa±sd; I/6m) were: L-(56.30±12.99^Aa†/48.86±11.38^Aa‡); C-(38.03±10.24^Ba†/32.02±12.94^Ba‡); LA(44.74±13.08^Aa†/39.85±11.71^Aa‡); CA(42.40±11.57^Ba†/28.46±10.09^Ba‡). Both the irradiation (p<0.001) and the aging (p=0.014) exerted significant influence on the results, contrary to what happened to the persistence of the etiological factor (p=0.124). There was no interaction between factors studied (p>0.05). Laser irradiation favored, thus, regardless of the persistence or not of the etiological factor, both immediately and after 6 months, bond strength to simulated hypersensitive dentin, which considerably reduced, in any case, over time.
Conclusions: Nd:YAG laser-irradiation of hypersensitive dentin as a treatment alternative former to its restoration can favor, even when the cause persists, and relatively lastingly, establishment of satisfactory adhesive interfaces on this substrate.