_applied sciences_  
_Apticle_  
**Does Adhesive Layer Thickness and Tag Length Influence Short/Long-Term Bond Strength of Universal Adhesive Systems? An In-Vitro Study**  
**[PERSON] 1,2,*,** **[PERSON] 3, [PERSON] 4, [PERSON] 2, [PERSON] 5,6, [PERSON] 7, [PERSON] 8(c), [PERSON] 8(c), [PERSON] 9,10(c), [PERSON] 1,2 and [PERSON] 1,2**  
1 Department of Endodontics, Faculty of Dental Medicine, Strasbourg University, 67000 Strasbourg, France; [EMAIL_ADDRESS] (Y.H.); [EMAIL_ADDRESS] (D.M.)  
2 Unitte Mixte de Recherche 1121, Institut National de la Sante et de la Recherche Medicale, 11 rue [PERSON], CEDEX, 67085 Strasbourg, France; [EMAIL_ADDRESS]  
3 Private Practice, Zahharzterpraxis Ashi, Bahnhoftstr 2, 09419 Thum, Germany; [EMAIL_ADDRESS]  
4 Department of Endodontics, Faculty of Dental Medicine, Damascus University, Damascus 0100, Syria; ammanredo@[EMAIL_ADDRESS]  
5 Ccube Laboratory, UMR 7357 CNRS, Mechanics Department, University of Strasbourg, 67000 Strasbourg, France; [EMAIL_ADDRESS]  
6 Laboratoire Energiugteo Mecanique Electromagnetisme, University of Paris Ouest, 50 rue de Sevres, 92410 Ville d'Avray, France  
7 Department of Conservative Denitstry, Loma Linda University, 11092 Anderson St., Loma Linda, CA 92305, USA; [EMAIL_ADDRESS]  
8 Department of Restorative Dentistry, Saint-Joseph University, Beirut 11072180, Lebanon; [EMAIL_ADDRESS] (R.B.); [EMAIL_ADDRESS] (L.H.)  
9 Dental Biomaterials and Minimally Invasive Dentistry, Department of Dentistry, Cardenal Herrera-CEU University, CEU Universities, C/Santiago Ramon y Cajal, s/n., Alfara del Patriarca, 46115 Valencia, Spain; [EMAIL_ADDRESS]  
10 Department of Therapeutic Dentistry, I.M. Sechenov First Moscow State Medical University, 119146 Moscow, Russia  
11 Department of Therapeutic Dentistry, [PERSON] First Moscow State Medical University, 119146 Moscow, Russia  
12 Department of Therapeutic Dentistry, [PERSON] First Moscow State Medical University, 119146 Moscow, Russia  
13 Department of Therapeutic Dentistry, [PERSON] First Moscow State Medical University, 119146 Moscow, Russia  
14 Correspondence: [EMAIL_ADDRESS]; Tel.: +33-66752-2841  
**Abstract** (1) Background: This study investigated the effect of the adhesive layer thickness and the length of resin tags on dentin bond strength of five universal adhesives applied in self-etch mode. (2) Methods: One hundred and fifty extracted human third molars were used. Five different universal adhesives were applied in self-etch mode on the dentin surface. Half of the specimens were subjected to an aging procedure for six months. A shear bond strength (SBS) test was performed and the results were statistically analyzed with a \(t\)-test and one-way ANOVA test. Scanning electron microscopy (SEM) was executed to measure the adhesive layer thickness and tag depth. (3) Results: No statistical differences were found between the five adhesive systems after a 24 h storage period, regardless of layer thickness and tag depth (\(p<0.05\)). After 6 months of aging in water at 37 \({}^{\circ}\)C, Iperbond Max and Scotchbond Universal preserved the bond strength over time (\(p<0.05\)), whilst the SBS of Iperbond Ultra, FuturaBond M+, and Ibond Universal decreased significantly after the aging period. No relation was observed between the adhesive thickness or tags' length on SBS. (4) Conclusions: Within the limitation of this study, the stability over time of the bond strength of universal adhesives depends on their compositions regardless of the adhesive layer thickness and/or tags' length.  
**Keywords: universal adhesives; layer thickness; self-etch; dentin bonding; shear bond strength**