# A Literature Review of Adhesive Systems in Density: Key Components and Their Clinical Applications
## 6 Resin Adhesive Systems
### Etch-and-Rinse Adhesive Strategy
Thus, the HL is formed by the resin infiltrated surface layer on dentin and enamel. The purpose of the ideal hybridization for these adhesives is to gain high BSs [9], typically in the range of 20 MPa for both enamel and dentin substrates [262]. Figure 16: Classification of bonding systems [9]. Figure 15: Micrographs of an **(a)** etch-and-rinse (ER) and **(b)** a self-etch (SE) adhesive system. Resin tags are clearly detectable in the ER adhesive systems **(a)**, since they infiltrated dentin tubules funneled by the etching agent. SE adhesives often infiltrate no further than the smear layer and smear plugs, revealing a more homogenous morphology that is empty of long resin tags [4]. This system is very sensitive and requires a controlled etching technique, followed by an application of two or more components on both enamel and dentin [33]. However, they are very effective when used correctly, and are the most versatile of all adhesive generations, as they can be used for any bonding protocol (direct, indirect) or photopolymerization (self-cure, dual-cure). These systems are still the standards by which new systems are judged. Nevertheless, they can be very confusing and time-consuming with so many bottles and application steps [9; 10; 33]. Due to the complexity of ER III (All-Bond 2 and All-Bond 3 (Bisco, Inc., Schaumburg, IL, USA), Clearfil Liner Bond (Kuraray, Tokyo, Japan), Scotchbond Multi-Purpose and Adper Scotchbond Multi-Purpose Plus (3M ESPE, St. Paul, MN, USA), OBFL (Kerr Co, Orange, CA, USA), Syntac ClassicBond-it (Ivoclar Vivadent, Schaan, Liechtenstein), Permaquick (Ultradent, South Jordan, UT, USA), Amalgabond (Parkell, Edgewood, NY, USA), Gluma CPS (Heraeus Kulzer, Hanau, Germany), FL Bond (Shofu, Kyoto, Japan)), dentists sought a simpler adhesive solution. It is not just about the timing and number of bottles, but also the etching process, rinsing, and drying durations [9; 33]. This marked a significant turning point in adhesive dentistry [266]. ER II systems were created in the late 1990s with a commercial focus on simplicity and speed of action, hence their general name of \"single-component systems\" or \"one-bottle systems\". Notable products include Admira Bond, Solobond M, Polibond by VOCO (Cuxhaven, Germany); Excite, Excite DSC, Excite F, Single Layer Bond by Ivoclar Vivadent (Schaan, Liechtenstein); Optibond Solo Plus by Kerr (Orange, CA, USA); Prime & Bond 2.0, Prime & Bond 2.1 by Dentsply DeTrey GmbH (Konstanz, Germany); Prime & Bond NT, Prime & Bond XP by Dentsply Sirona (York, PA, USA); One Step, One-Step Plus by Bisco (Schaumburg, IL, USA); Single Bond Adper 2, Scotchbond1 by 3M ESPE (St. Paul, MN, USA); and Clearfil Liner Bond 2 by Kuraray (Tokyo, Japan) [9]. In addition, there was a need to improve the prevention of collagen collapse in demineralized dentin and minimize, if not completely eliminate, postoperative sensitivity. The most common simplification method is therefore the \"one-bottle system\" which combines the hydrophilic primer and the hydrophobic adhesive resin in a single bottle with a solvent, to be applied simultaneously to enamel and dentin after etching with 35 to 37% of H\({}_{3}\)PO\({}_{4}\) (etching on enamel for 15 to 30 s and on dentin for a maximum of 15 s) [268]. Their use is unlikely to be simple due to their low tolerance for handling. Furthermore, their performance is closely related to the moisture of the treated dentinal substrate. All ER II adhesives are incompatible with dual- and self-cured materials. This could be explained by the lower pH of the oxygen-inhibited layer, or the monomers in some simplified products, deactivating the tertiary amine in chemically cured composites [9; 33; 266]. Several long-term studies of ER II dental adhesives have shown high clinical bonding strengths (\(\sim\)25 MPa) [262]. Despite this, the resin-dentin bond is prone to water degradation. ER III adhesives are less prone to water degradation than ER II dental adhesives [9; 266]. This is due to the high concentration of HEMA monomer inside the ER II.