1. Performance of Universal Adhesives in Composite Resin Repair
Hyemin Yin, Sumin Kwon, Shin Hye Chung, Ryan Jin Young Kim Biomed Res Int. 2022 May 9;2022:7663490. doi: 10.1155/2022/7663490. eCollection 2022.
Aim: The objective of this in vitro study was to evaluate the bond strength of universal adhesive systems in self-etch and etch-and-rinse modes at the repair interface between aged and new composite resins. Materials and methods: Composite resin (Filtek Z250) was thermocycled to represent aged composite resin to be repaired. New composite resin was placed over the aged substrate after surface conditioning: NC (negative control, no surface treatment), A (adhesive only), SBM (Scotchbond Multi-Purpose in etch-and-rinse mode), CSE (Clearfil SE Bond in self-etch mode), SBU (Single Bond Universal), ABU (All Bond Universal), and TBU (Tetric N-Bond Universal). Universal adhesives (SBU, ABU, and TBU) were applied both in etch-and-rinse and self-etch modes. 1 mm × 1 mm × 8 mm beams were sectioned, and microtensile bond strength was measured after 24 hours of water storage and 10,000 thermocycling processes (n = 20/group). The fracture surfaces were observed with a scanning electron microscope to evaluate the failure pattern. Results: The repair bond strength between the old and new composite resins was material-dependent. Universal adhesives significantly improved the repair bond strength (p < 0.05), while no significant difference was observed between the etch modes (self-etch or etch-and-rinse) for each universal adhesive (p > 0.05). Thermocycling significantly reduced the bond strength in all groups (p < 0.05). Conclusion: Universal adhesives in both etch-and-rinse and self-etch modes outperformed the conventional 3-step etch-and-rinse and 2-step self-etch adhesive systems in terms of resin repair bond strength.
2. Understanding Tetrahydropyranyl as a Protecting Group in Peptide Chemistry
Anamika Sharma, Iván Ramos-Tomillero, Ayman El-Faham, Ernesto Nicolas, Hortensia Rodriguez, Beatriz G de la Torre, Fernando Albericio ChemistryOpen. 2017 Mar 8;6(2):168-177. doi: 10.1002/open.201600156. eCollection 2017 Apr.
Tetrahydropyranyl (Thp) is recognized as a useful protecting group for alcohols in organic synthesis. It has several advantages, including low cost, ease of introduction, general stability to most non-acidic reagents, it confers good solubility, and the ease with which it can be removed if the functional group it protects requires manipulation. However, little attention has been paid to Thp in peptide chemistry. Provided here is a concise analysis of the Thp protection of various amino acid functionalities (OH, SH, NH and COOH) and its application to peptide synthesis. Thp is a useful moiety for the side-chain protection of serine, threonine and cysteine and is suitable for the Fmoc/tBu solid-phase peptide synthesis strategy. The immobilized version of 3,4-dihydro-2H-pyran, the so-called Ellman resin, is also discussed as a useful solid support for anchoring the side chains of serine, threonine and tryptophan residues.
3. Bond strength of self-adhesive resin cements to a high transparency zirconia crown and dentin
Jeng-Fen Liu, Chun-Chuan Yang, Jun-Liang Luo, Yu-Ching Liu, Min Yan, Shinn-Jyh Ding J Dent Sci. 2022 Apr;17(2):973-983. doi: 10.1016/j.jds.2021.12.008. Epub 2021 Dec 20.
Background/purpose: The bond strength and durability of highly translucent zirconia ceramics to dentin is still unclear. The purpose of this study was to investigate the effect of various surface treatments on the bond strength of self-adhesive resin cements to high-translucent zirconia crowns and dentin. Materials and methods: A high-transparent zirconia and three self-adhesive resin cements (G-CEM LinkAce (GCL), RelyX U200 (RXU) and TotalCem (TTC)) were used. The zirconia surface was sandblasted with 50 μm alumina particles or coated with an SR Link primer, while a dentin primer (Tetric N-Bond Universal, TBU) was applied to the surface of the dentin. By using three self-adhesive resin cements, zirconia samples were bonded to the dentin surfaces of human teeth. The shear strength of the specimens was measured before and after 10,000-cycle thermocycling or 90-day aging. Results: When using GCL to bond with the untreated dentin and various zirconia surfaces, the shear bond strength of the sandblasted (ZSB) and RS Link primer-coated (ZLK) groups was significantly higher than that of the untreated control group (Zc). However, in the case of TBU-treated dentin, the shear strength of the ZSB + LK + DTBU group was significantly higher than that of the other groups. After thermocycling and aging, the shear strength of the ZSB + LK + DTBU group using GCL and RXU cements decreased slightly, while the TTC showed no impact. Conclusion: The zirconia surface pretreated by sandblasting and bonding agent, which was sequentially bonded with a primer-treated dentin by using resin cements, can provide excellent shear bond strength and anti-aging performance.
