Abstract
Antioxidants are known for their potential of strengthening the collagen network when applied to dentin. They establish new intra-/intermolecular bonds in the collagen, rendering it less perceptive to enzymatic hydrolysis. The study evaluated the benefit on shear bond strength (SBS) of a resin–composite to dentin when antioxidants with different biomolecular mechanisms or a known inhibitor of enzymatic activity are introduced to the bonding process in a clinically inspired protocol. Specimens (900) were prepared consistent with the requirements for a macro SBS-test. Four agents (Epigallocatechingallate (EGCG), Chlorhexidindigluconate (CHX), Proanthocyanidin (PA), and Hesperidin (HPN)) were applied on dentin, either incorporated in the primer of a two-step self-etch adhesive or as an aqueous solution before applying the adhesive. Bonding protocol executed according to the manufacturer’s information served as control. Groups (n = 20) were tested after one week, one month, three months, six months, or one year immersion times (37 °C, distilled water). After six-month immersion, superior SBS were identified in PA compared to all other agents (p < 0.01) and a higher reliability in both primer and solution application when compared to control. After one year, both PA incorporated test groups demonstrated the most reliable outcome. SBS can benefit from the application of antioxidants. The use of PA in clinics might help extending the lifespan of resin-based restorations.
Highlights
In the past, different authors presented evidence that the risk of replacement in posterior teeth is still higher for resin-based composite restorations than for amalgam fillings [1,2,3]
The dentin–resin hybrid layer is considered the weak link in resin-based restorations [5], as dentin presents a very complex structure and morphology being streaked with microscopic tubules (~1–2 μm in diameter) dividing it into intertubular—rich in organic matter—and hypermineralized peritubular dentin [6,7]
Definitive occurrence and proteolytic activity in both carious and intact dentin was only determined for cysteine cathepsin B (CC-B) and cystein cathepsin K (CC-K) [28,62,63], while the most abundantly found metalloproteinases in dentin are matrix metalloproteinases (MMPs)-2, -8, -9, and -20 [64,65,66]
Summary
Different authors presented evidence that the risk of replacement in posterior teeth is still higher for resin-based composite restorations than for amalgam fillings [1,2,3]. The dentin–resin hybrid layer is considered the weak link in resin-based restorations [5], as dentin presents a very complex structure and morphology being streaked with microscopic tubules (~1–2 μm in diameter) dividing it into intertubular—rich in organic matter—and hypermineralized peritubular dentin [6,7]. Pashley [13] described intact dentin as a dynamic substrate as related to its differing distribution of minerals, organic network, water content, and permeability dependent on dentin depth, creating a unique bonding substrate dependent on the given distance to the pulp [14]. Age-related or pathologic changes in dentin structure and morphology as induced by sclerosis or caries pose additional challenges for dentin bonding [15,16]
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