# A Literature Review of Adhesive Systems in Density: Key Components and Their Clinical Applications
## 6 Resin Adhesive Systems
### Functional monomers
#### 6.1.4 Other Components  
Some manufacturers include filler particles in their adhesive formulations to enhance the mechanical features of an adhesive layer (for example, Tetric N Bond Total Etch (Ivoclar Vivadent, Schaan, Liechtenstein), and Gluma 2 Bond, (Kulzer GmbH, Hanau, Germany)). Others incorporate CHX into their adhesive solutions to improve bond stability by reducing adhesive bond deterioration (for example, Peak Universal Bond (Ultradent Products, Inc., South Jordan, UT, USA) and Futurabond U (VOCO GmbH, Cuxhaven, Germany)). Another chemical added by manufacturers to dental adhesives is GA, which helps in minimizing post-operative sensitivity and maintain the collagen fibers in the HL, improving durability (for example, iBond Total Etch (Heraeus Kulzer GmbH, Hanau, Germany)). To avoid secondary caries beneath restorations, companies use antibacterial agents in the adhesive formulation [33]. An example of an antimicrobial component incorporated in some adhesive agents is the Clearfil Protect Bond (Kuraray, Tokyo, Japan), which is MDPB-based. Cetylpyridinium chloride is also an extremely efficient broad-spectrum antibacterial agent. A further example is the use of fluoride inside FL-Bond II (Shofu, Kyoto, Japan) and Futurabond NR (VOCO GmbH, Cuxhaven, Germany). In addition, the use of polymerizing agents (for example, Camphorquinone (CQ)) is necessary to initiate the polymerization of dental adhesives. Certain producers incorporate dyes into their adhesives to facilitate uniform mixing of the ingredients and serve as an indicator throughout the process, with the resulting bond becoming colorless after curing (Universal Bond by Tokuyama company (Tokuyama Dental, Tokyo, Japan)). In general, the influence of these compounds on \begin{table}
\begin{tabular}{l l l} \hline \hline
**Solvent** & **Advantages** & **Disadvantages** \\ \hline Acetone/Ketones [204; 217; 218] & - Low intrinsic viscosity & - Undesired solvent loss \\  & - Easy removal & - Risk of interaction with other components \\ Ethanol/Primary Alcohols [204; 221; 222; 223] & - Sufficient penetration & - Side reactions (e.g., Michael-addition) \\  & - Evaporation/removal & - Low stability with acids \\ Water [204; 230] & - Best dental compatibility & - Lowers evaporation rate \\  & - Essential for etching & - Lowers evaporation rate \\  & - Limited/no side reactions & \\  & - Acrylate compatibility & - Increased matrix viscosity \\  & - High stability with acids & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Solvent overview of common systems used in dental adhesives including the respective pros and cons [204]. the performance of adhesive agents is still uncertain and should be considered in future studies [15; 33]. In addition to the aforementioned components, the use of inorganic-organic additives have garnered significant attention for their ability to enhance bonding performance. These additives, particularly in the form of modifier monomers, have been shown to improve adhesion by creating a HL that reinforces the interface between the restorative material and tooth substrate. For instance, as highlighted in studies such as those by [PERSON] et al. [242] and [PERSON] et al. [243], inorganic-organic compounds contribute to the formation of durable bonds through chemical interactions with both the adhesive and the dentin. The incorporation of these additives results in improved mechanical properties, reduced shrinkage, and enhanced long-term stability of the adhesive interface. Future advancements in adhesive systems will likely continue to explore and optimize the role of these modifiers to further improve clinical outcomes in restorative dentistry. Referencing critical elements, such as the use of fillers, is essential for comprehending their impact on the properties of the adhesive agent. One potential cause of debonding in dental restorations could be the low mechanical properties of the adhesive layer that bonds the dental substrate to the resin composite.