Evaluation of Bond Strength of Self-Etch and Universal Adhesives to Primary Teeth Dentine

Background: A microtensile bond strength (µTBS) study was conducted to determine if 1-step self-etch adhesives, 2-step self-etch adhesives or universal adhesives with functional monomers is the best protocol for primary teeth dentine adhesion.

Methods: 65 primary teeth (n=5) were restored with Filtek Z250, 3M Oral Care and the following adhesives; control: Prime and Bond NT, Dentsply Sirona (Control); 2-step: Clearfil SE Bond, Kuraray / Optibond XTR, Kerr Dental; 1-step: Adper Easy Bond, 3M Oral Care / Adhese One F, Ivoclar Vivadent / ibond Self Etch, Heraeus Kulzer / Xeno V+, Dentsply Sirona / Gaenial Bond, GC / Beautibond, Shofu; universal: One Coat 7 Universal, Coltene / Futurabond U, Voco / Prime and Bond active, Dentsply Sirona / i-bond Universal, Heraeus Kulzer. After 24-h storage in water, 999 sticks with 0,37 mm² adhesive area were formed and were loaded at 1 mm/min in microtensile mode (TC-550 Syndicad) until fracture.

Results: Most of the tested adhesives exhibited better bond strength than the control (p<0.05, Bonferroni). 2-step adhesives with different solvents (water vs alcohol) and different pH do not exhibit different μΤΒS values (p>0.05). Bond strength of 1-step self-etch adhesives varies. Acetone-based mild self-etch adhesives exhibit significantly higher μTBS values compared to alcohol-based adhesives (p<0.05, Bonferroni). Water/ethanol mixture exhibits better values than alcohol alone (p<0.05, Bonferroni) and comparable results to water/acetone (p>0.05, Bonferroni), even when acidity differs. Regarding universal adhesives, same-acidity and same-solvent adhesives may exhibit different μTBS values (p<0.05, Bonferroni). Mild universal adhesives show same bond strength as mild acetone-based 1-step adhesives (p>0.05, Bonferroni). Low pH universal adhesive exhibited lower μTBS compared to mild or ultra-mild universal adhesives, to 2-step self-etch and to most of 1-step self-etch adhesives (p<0.05, Bonferroni).

Conclusions: 2-step acetone-based self-etch adhesives bond better to primary teeth dentine than alcohol-based. Mild universal adhesives show same behavior as mild acetone-based 1-step adhesives.