Which generation bonding agent is best?
Introduction
In the field of dentistry, bonding agents play a crucial role in ensuring the success and longevity of various restorative treatments. They are used to create a strong bond between the tooth structure and restorative materials such as composites or ceramics, providing stability and durability. Over the years, different generations of bonding agents have been developed, each with their unique set of advantages and limitations. This article aims to explore the different generations of bonding agents and determine which one is considered the best option in clinical practice.
Generation I Bonding Agents
The first generation of bonding agents, introduced in the 1950s, relied on acid etching to create micromechanical retention on enamel. These agents used phosphoric acid to selectively remove the enamel''s outer layer, creating a rough surface for better adhesion. However, this generation of bonding agents had several limitations. They were not effective on dentin, as acid etching caused the collapse of dentinal tubules, hindering the bonding process. Additionally, their technique sensitivity and lack of long-term stability limited their widespread use.
Generation II Bonding Agents
The second generation, developed in the 1970s, aimed to address the limitations of the first generation. These agents introduced the concept of primers and adhesives, separating the etching and adhesive steps. Primer was applied to the etched enamel surface to wet it and improve the penetration and wettability of the adhesive. Adhesive resin was then applied, which formed a chemical bond with the primer, creating an adhesive interface between the tooth structure and restorative material.
Generation II bonding agents exhibited improved bond strength and durability compared to their predecessors. They provided better adhesion to dentin and were less technique sensitive. However, they still had limitations, such as the inability to bond to moist dentin or contaminated surfaces. Moisture control was crucial during application to achieve optimal bonding.
Generation III Bonding Agents
The third generation of bonding agents emerged in the 1980s and introduced the concept of total-etch systems. These systems involved etching both enamel and dentin with acid, followed by the application of a primer and adhesive. This generation of bonding agents further improved bond strength, particularly on dentin, as the etching process exposed collagen fibrils, enhancing micromechanical retention. They also exhibited better resistance to moisture and contamination.
Generation III bonding agents became widely accepted in clinical practice due to their predictable bond strength and simplified technique. However, they still faced challenges in achieving a long-term durable bond, especially in a moist environment. Sensitivity to technique variations and postoperative sensitivity were reported as well.
Generation IV Bonding Agents
The fourth generation, introduced in the 1990s, aimed to overcome the limitations of previous generations by incorporating hydrophilic monomers into the adhesive system. These hydrophilic monomers had the ability to bond to both moist dentin and enamel, reducing the need for meticulous moisture control during application.
Generation IV bonding agents demonstrated improved bond strength, reduced technique sensitivity, and increased resistance to moisture and contamination. They also offered enhanced marginal sealing and a more reliable bond interface. However, concerns regarding postoperative sensitivity and long-term durability persisted.
Generation V Bonding Agents
The fifth generation of bonding agents emerged in the early 2000s and introduced the concept of self-etching primers. These primers contained acidic monomers that simultaneously etched and primed the tooth surface, simplifying the bonding procedure. They formed a hybrid layer by demineralizing and infiltrating the superficial layer of dentin, resulting in a chemical and micromechanical bond.
Generation V bonding agents provided excellent bond strength to both enamel and dentin, along with reduced postoperative sensitivity. They exhibited improved moisture tolerance and simplified application technique, making them popular among clinicians. However, concerns regarding etching depth control and long-term bond stability were raised.
Generation VI Bonding Agents
The sixth generation of bonding agents, also known as universal bonding agents, were introduced in recent years. These agents aimed to simplify the bonding process further by combining self-etch and etch-and-rinse techniques into a single bottle. They could be used in both self-etch and total-etch modes, depending on the clinical situation and operator preference.
Generation VI bonding agents offered versatility, as they could be used for both direct and indirect restorations. They exhibited excellent bond strength to enamel and dentin, improved moisture tolerance, and reduced postoperative sensitivity. Moreover, they simplified the bonding protocol, saving chairside time.
Conclusion
In conclusion, the evolution of bonding agents over the years has led to significant improvements in adhesive dentistry. Each generation has introduced new techniques and materials, aiming to overcome the limitations of previous generations. While it is challenging to determine the absolute best generation of bonding agents, the sixth generation, with its versatility and simplified application, has gained popularity in recent years. However, it is important to note that the choice of bonding agent depends on various factors, including the clinical situation, operator preference, and the specific needs of the patient. Consulting with dental professionals and keeping up with the latest research is essential to make informed decisions and achieve successful restorative outcomes.