Although there are several classifications for the definitive luting agents, they can be, however, classified into two main categories based on the ability to achieve chemical connection to different substrates; conventional (e.g. zinc phosphate, glass-ionomer and resin-modified glass-ionomer cements) and adhesives. Most commonly used and best documented adhesive luting agents are the adhesive composite resin cements.
The choice of whether to use a conventional cement or an adhesive resin cement depends on several factors, the key factors are:
1. Retention and resistance form of the abutment tooth:
Achieving a proper retention form during daily practice is hard to realize and thus conventional cementation in such cases can present clinical problems especially on the long term. Therefore, adhesive luting can be recommended in these cases as an alternative to conventional cementation. For full-coverage restorations with preparation designs featuring at least some mechanical retention, the use of self-adhesive resin cements can be considerate a good alternative as it provides high clinical success rates.
2. Mechanical and optical properties of the restorative material (flexural strength and translucency):
As a general guideline for all-ceramic restorations, ceramics with low and medium flexural strength under 350 MPa should be adhesively luted with composite resin cements, as these restorations rely on resin bonding for reinforcement and support. This includes feldspathic-, glass-, hybrid-ceramics and composite.
Concerning optical properties, the choice of an opaque conventional cement for cementation of high-translucent restoration should not be recommended as it can negatively influence the final esthetic results.
3. Simplicity of the workflow and special requirements of the working environment:
Although the conventional cements are simple and fast in their use, they provide little or no adhesion at all and therefore they are not recommended in several cases. A simple but reliable method can be well accomplished by the use of self-adhesive resin cements as they can be considered the best alternative for full-adhesive adhesive luting in less critical situations that do not rely entirely on adhesion.