25 June 2021

---

Preheating and bioactive development of a unidose 3-step etch-and-rinse dentin adhesive

Co-authors: A. Comba, F. Florenzano

Lorenzo Breschi

---

Nowadays, the resin-dentin bond remains an issue for the durability of  the adhesive direct restorations . 

The pre-heating of restorative materials   is a recurrent tendency to increase theirs physical and mechanical properties. 

In the present laboratory work Prof. Magne and Dr Ubaldini evaluated the influence of pre-heating  together with the inclusion of a bioactive glass   in a unidose 3-step etch-and-rinse adhesive system on adhesive strength.

Material and methods

The authors prepared dentin disks from 80 molars and assigned them to 8 groups (n=10): in CG-T1 and CG-T2 the adhesive system was used without any modification, in PG- T1 and PC-T2 both the components were preheated at 68°C just before the application. In BG-T1 and BG-T2 a bioactive glass was added to the primer. In PBG-T1 and PBG-T2, the adhesive system received both modifications, its primer was modified by adding 0.05 mg of BAG, and both primer and bond components were preheated as previously indicated.

The dentin surfaces were treated with 35% phosphoric acid (Ultra Etch 35%; Ultradent Products, Inc) for 15 seconds and rinsed for 1 minute. Primer was lightly rubbed on the dentin for 30 seconds and air dried for 5 seconds. Adhesive was applied with a light brushing motion for 30 seconds and polymerized for 20 seconds at 1000 mW/cm2 by using a light-emitting diode unit (VALO Curing Light; Ultradent Products, Inc). Then a direct restoration was performed (Filtek Z100; 3M) covering the entire dentin. All restored specimens were stored in distilled water at room temperature for 1 week (T1) or 6 months (T2, water replaced weekly) before testing.

TBS  data were analyzed by the authors and scanning electron microscopy was added to analyze the failure mode. Attenuated total reflection Fourier transform infrared spectroscopy was used to quantitatively analyze the modifications to the chemical structure of the group tested.

Results

From the collected results, the two authors found that TBS results reveald significant differences for the different pretreatment   but not for the variable storage time. The preheated group (PG-T1) provided significantly stronger bond strength when compared with the other groups . Failure modes were mostly adhesive. Attenuated total reflection Fourier transform infrared spectroscopy performed by the researchers showed that   preheating the bonding agent promoted the condensation reaction between the silane and adhesive fillers   .

Conclusion.

Considering the results obtained with the present in vitro research Prof. Magne and Dr Mori Ubaldini concluded no decrease in mTBS was observed for any group after 6 months. In  addition, preheating the adhesive system (primer and bonding resin) significantly increased the 1-week and 6-month mTBS. Finally, the inclusion of bioglass did not affect the bond strength.

(Photocredit: Dr. Allegra Comba)

For more information: Thermal and bioactive optimization of a unidose 3-step etch-and-rinse dentin adhesive.