Adhesion is central to many restorative procedures, but choosing a bonding system can be less straightforward. Dentists have to weigh the etch strategy, bond strength data, handling requirements, and the types of cases they see regularly. A system that works well in one practice may not be the most practical choice for another.
Understanding the Different Etch Strategies
Dental adhesive systems generally fall into three categories: total-etch, self-etch, and universal adhesives.
Total-etch, also called etch-and-rinse, involves applying phosphoric acid separately to the enamel and dentin before the primer and bonding resin are applied. The technique can produce strong enamel bonding, but it requires careful rinsing and moisture control. Excessive drying of dentin can also affect the bonding process and may contribute to postoperative sensitivity.
Self-etch systems combine the etching and priming steps in a single product. This reduces the number of separate steps and avoids the need for a separate phosphoric acid application to dentin. Enamel bonding may be lower with some self-etch systems, particularly on intact enamel, which is why some clinicians use selective enamel etching as part of the protocol.
Universal dental adhesives, also known as multi-mode adhesives, are designed for use with more than one bonding strategy. Many contain MDP, a phosphate monomer that can form chemical bonds with tooth structure and, depending on the formulation, materials such as zirconia and certain metals. Their flexibility can be useful in practices that handle a range of restorative materials, but performance still varies between products and substrates.
Interpreting Bond Strength Data
Manufacturers commonly report shear or tensile bond strength in megapascals (MPa), based on laboratory testing with extracted teeth. These figures provide useful information about how products perform under controlled test conditions, but they do not reproduce every factor present in a dental operation.
Moisture, contamination, isolation, application technique, and curing conditions can all affect the clinical result. For that reason, published bond strength should be considered alongside the testing method and the manufacturer’s instructions rather than viewed as a standalone measure of clinical performance.
Consider Technique Sensitivity and Chairside Time
Technique sensitivity describes how much the result depends on carrying out each stage of the adhesive protocol correctly. Factors such as dentin moisture, application time, air-thinning, curing distance, and curing duration can all affect the outcome.
Dental adhesives with fewer application steps may be easier to incorporate into a busy clinical workflow, particularly when several people are involved in preparation and isolation. That does not necessarily mean a shorter protocol is preferable in every case. More involved systems may still be appropriate when the clinical situation places greater demands on the restoration.
The important consideration is whether the adhesive protocol can be followed consistently under the conditions of the practice.
Account for Moisture and Different Tooth Substrates
Dentin presents a different bonding surface from enamel. It contains more moisture and has a more variable structure, while enamel characteristics can also differ depending on whether the surface is intact, prepared, or located near a margin.
Dental bonding agents in restorative dentistry are formulated to manage this variability to a degree, but they cannot compensate for inadequate isolation. Rubber dam or effective relative isolation remains important when contamination needs to be controlled.
The bonding substrate should also be considered before selecting the protocol. A restoration may involve enamel, dentin, or both, and the adhesive strategy may need to account for those surfaces separately.
Match the Adhesive to the Clinical Case Mix
There is no single adhesive system that is necessarily the right choice for every clinical situation. Instead, consider the procedures performed most often in the practice and the materials being bonded.
Anterior restorative work with substantial enamel margins may be well suited to a protocol that includes selective enamel etching. Posterior composite restorations may call for a straightforward adhesive protocol that can be applied consistently within the available chairside time.
Practices that also place indirect restorations or routinely work with zirconia may prefer a universal adhesive containing MDP, depending on the manufacturer’s indications and the materials involved. The aim is not simply to reduce the number of products on the shelf, but to choose a bonding system that fits the restorative procedures performed in the practice.
FAQs
Is a higher bond strength number always the better choice?
Not necessarily. Laboratory bond strength values are obtained under controlled testing conditions and do not capture every factor that affects bonding in clinical practice. Isolation, application technique, operator consistency, and the substrate itself can influence the result. Published MPa values are therefore best considered alongside the testing conditions, clinical indications, and handling requirements of the adhesive.
Do universal adhesives replace the need for selective enamel etching?
Not necessarily. Although many universal adhesives can be used in self-etch mode, selective phosphoric acid etching of enamel may improve enamel bonding with some products. This can be particularly relevant when bonding to intact or unprepared enamel. The appropriate protocol depends on the adhesive and the manufacturer’s instructions.
How often should an adhesive protocol be reviewed or changed?
There is no standard interval for changing an adhesive system. A review may be appropriate when the practice’s case mix changes, when postoperative sensitivity becomes a recurring concern, or when the practice begins placing more indirect restorations or working with materials such as zirconia.
Before changing a protocol, review the manufacturer’s instructions and consider whether the existing system is being used consistently and according to its intended technique.
