A Method to Bond Vital Dentin With a Microleakage-Free Hybrid Layer

To investigate the dye penetration distance at Class V tooth-restoration margins/interfaces prepared in the labora-tory and orally using a primerless wet technique and MMA-TBB bonding resin with or without 4-META monomer promoter.

A box-form cavity at the cementoenamel junction was prepared on extracted human premolars and vital teeth scheduled for extraction for in-vitro and in-vivo studies, respectively. For each vital cavity, 1% citric acid and 1% ferric chloride aqueous (1-1) conditioner was applied for 10 s, 30 s, or 60 s, rinsed off and blot-dried, and was then bonded with either 4-META/MMA-TBB or MMA-TBB resin and bulk-filled with light-cured composite resin (n = 10). Restored vital teeth continued to function in the oral cavity for seven days before extraction. Restorations were stored in water at 37°C and 0.5% basic fuchsin dye solution for 24 h each before dye penetration measurement under a microscope, while a hybrid layer was observed using a scanning electron microscope (SEM).

No hypersensitivity or pain occurred in any vital teeth. For all 1-1 groups, no dye penetration was detected at any margins of the in- vitro restorations. Dye penetration (0.13 mm) was only observed in one intraoral restoration of 60 s etching with MMA-TBB resin at the cementum/dentin margin. A consistent hybrid layer after chemical modification was observed in leakage-free specimens.

The results suggest that the 1-3 µm 1-1 demineralized substrate clinically provides sufficient permeability to form a microleakage-free hybrid layer using a primerless wet technique with MMA-TBB or 4-META/MMA-TBB resin. Intraoral microleakage-free restorations may lead to longer-term restored-tooth survival.