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Origin of interfacial droplets with one-step adhesives
K L Van Landuyt1, J Snauwaert, J De Munck
1Leuven BIOMAT Research Cluster, Department of Conservative Dentistry, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, B-3000 Leuven, Belgium.
Journal of Dental Research
|July 27, 2007
Summary
Interfacial droplets in one-step self-etch adhesives originate from phase separation in HEMA-free types and water absorption in HEMA-rich types. Only water-induced droplets significantly reduce bond strength.
Area of Science:
- Dental Materials Science
- Polymer Chemistry
- Biomaterials Engineering
Background:
- One-step self-etch adhesives are widely used in dental restorations.
- Interfacial droplets are a common observation with these adhesives.
- Understanding droplet origin is crucial for improving adhesive performance.
Purpose of the Study:
- To investigate the origin of interfacial droplets in one-step self-etch adhesives.
- To differentiate droplet formation mechanisms based on adhesive composition (HEMA-rich vs. HEMA-free).
- To correlate droplet presence and type with bond strength outcomes.
Main Methods:
- Application of two HEMA-rich and one HEMA-free adhesive to enamel and dentin.
- Varied curing protocols: immediate composite cure vs. delayed (20 min) cure.
- Microscopic observation of interfacial droplet formation and distribution.
- Assessment of bond strength after delayed curing.
Main Results:
- All tested one-step adhesives formed interfacial droplets.
- HEMA-free adhesives showed stable droplets throughout the adhesive layer, attributed to phase separation.
- HEMA-rich adhesives exhibited droplets at the resin/composite interface, increasing with delayed curing, originating from water absorption.
- Delayed curing with HEMA-rich adhesives led to a significant decrease in bond strength.
Conclusions:
- Droplet formation mechanisms differ between HEMA-free (phase separation) and HEMA-rich (water absorption) one-step self-etch adhesives.
- Water absorption-induced droplets in HEMA-rich adhesives negatively impact bond strength, particularly with delayed composite curing.
- Adhesive formulation and curing strategy are critical factors influencing interfacial integrity and bond durability.
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