“Choosing the right adhesive system can make all the difference—it’s not just about the surface, but how you bond to it”, says Mina Aker Sagen, scientist at NIOM.
In collaboration with other researchers, she has investigated how to achieve the best possible bond between composite resin and feldspathic porcelain during dental repairs. These materials are often used in restorations such as crowns and bridges, which can sometimes chip, especially when zirconia is used underneath the porcelain.
To fix small chips with composite resin, a strong bond between the two materials is crucial. The researchers tested two surface treatments—hydrofluoric acid (HF) etching and mechanical roughening with a diamond disc—and two bonding methods: a universal adhesive and a system with a separate silane primer and adhesive.
What did the researchers find out?
Bond strength was tested by applying force until the repaired material broke. Specimens that used the silane primer and adhesive had much higher bond strength than those using the universal adhesive.
Importantly, whether the surface was etched with HF or just roughened mechanically didn’t significantly affect the bond strength—what mattered more was the bonding method.
Fracture analysis showed that samples with better bonding (using the separate silane system) often fractured within the porcelain itself, not at the bond, suggesting the adhesive held firm. Conversely, samples with universal adhesive often failed at the bonding site.
Key results
- Surface treatment type (etching with HF or roughening) had little effect on bond strength when the same adhesive system was used.
- Bonding method played the biggest role: using a separate silane primer and adhesive resulted in significantly higher bond strength than using a universal adhesive.
- 70% and 50% cohesive fractures (within the porcelain) occurred in the groups using the separate primer system, indicating a strong bond.
- HF etching, while effective, may be avoidable due to toxicity—mechanical roughening may suffice when combined with the correct adhesive system.
- The results suggest a shift in clinical practice could improve safety and efficiency in minor porcelain repair procedures.