Repair Technique for Fluoride-releasing Core Build-up Material Containing S-PRG Filler

Objectives: Reflecting the widespread recognition of MI concept and growing needs of esthetic restorations, the resin core materials for core build-up is becoming prevalent. We have developed new core build-up composite system, consisting of one-step dual-cure self-etching adhesive (BDB) and fluoride-releasing dual-cure composite containing S-PRG filler (BC), which employs Pre-Reacted Glass-ionomer (PRG) technology.This study aimed to evaluate repair technique in abutment tooth prepared with S-PRG filler-containing core build-up composite.

Methods: S-PRG filler having three layers (glass core, glass-ionomer phase, surface-modified layer) was prepared by reaction between fluoride-containing acid-reactive glass filler having  surface-modified layer and polyacrylic acid solution. With S-PRG filler incorporated into Bis-GMA/TEGDMA resin, BC was prepared.BDB containing adhesive monomer was also prepared.Bonding was applied on the polished surface of cured BC (1.BDB; 2.SHOFU PORCELAIN PRIMER(SPP)+BDB; or 3.non-treatment), then BC was applied on each treated surface and dual-cured. Likewise, BC was bonded to bovine dentin by using BDB.The test specimens were immersed (37ºC water, 24h), tested for shear bond strength (SBS), and statistically analyzed (two-way ANOVA, Tukey's test).

Results: BC-1 treated with BDB showed significantly higher SBS than untreated BC-3. BC-1 also exhibited high SBS, which is equivalent to that of BC-2 treated with combination of SPP and BDB, as well as that of BC-4 in which bovine dentin was treated with BDB.

 

 

Conclusion: The repair technique using BDB alone for bonding showed high SBS comparable to that achieved by the combined use of SPP and BDB. Such high bond strength was considered to be due to chelate bond occurring between ion species (Sr²⁺, Al³⁺) in S-PRG Filler and acidic monomer in BDB. Since BDB showed high SBS to both tooth substance and to BC, it was suggested that in the case of repairing abutment tooth prepared with BC, BDB allows for bonding treatment on both dentin and BC simultaneously.