Guided Tissue Remineralization of Resin-dentin Interfaces. II. Intentional Dry Bonding

Objectives: The application of Guided Tissue Remineralization (Tay and Pashley, 2008) to dentin bonding provides a fresh, positive outlook on bridging the gap between deficiencies associated with moist bonding of hydrophilic etch-and-rinse adhesives and the longevity of resin-dentin bonds. In this work, we continued to challenge the limits of Guided Tissue Remineralization in severely compromised resin-dentin interfaces created intentionally by the application of etch-and-rinse adhesives on extensively air-dried phosphoric acid-etched dentin. Methods: Flat dentin surfaces were prepared from twenty extracted human molars and bonded with One-Step (Bisco) or Single Bond Plus (3M ESPE) after the acid-etched dentin was intentionally air-dried with strong moisture-free air blasts for 1 min. Baseline silver nanoleakage was characterized using TEM. One-mm thick slabs of resin-dentin interfaces were prepared and immersed in a Portland cement/simulated body fluid system containing polycarboxylic acid and polyphosphonic acid biomimetic analogs of dentin noncollagenous proteins. Unstained, undemineralized sections were examined using TEM and selected-area electron diffraction after 1-3 months of Guided Tissue Remineralization. Results: Remineralization of collapsed hybrid layers that re-expanded during Guided Tissue Remineralization was readily apparent after 1 month. By 2-3 months, hybrid layers were remineralized to 80-90% of their entire thickness except for a thin basal portion which appeared well-infiltrated. A hypermineralized layer was also apparent on the hybrid layer surface. Tubular orifices were occluded with mineral deposits that resembled those present in sclerotic dentin. Gaps between the surface hypermineralized layer and adhesive were also filled with minerals. Conclusion: Although extensive air-drying of acid-etched dentin is far removed from clinical practice, the model demonstrates the immense potential of Guided Tissue Remineralization in dentin bonding. It highlights that denatured collagen is unlikely to be remineralized to the same order and dimension as seen in intact collagen matrices. The model also sheds light on the etiology of sclerotic dentin formation.