The dentin adhesive luting technique is a procedure in which the dentin surface of a cavity (dentin surface of a cavity) is chemically pretreated in such a way that low-viscosity dentin bonding agents can penetrate the surface structures and, after chemical curing, form a micromechanical bond with the dentin on one side and the composite (resin) filling on the other. The bond created in this way acts so effectively that additional macromechanical retentions for wedging the filling, which would have to be created by preparation (by grinding the tooth) at the sacrifice of healthy tooth substance, can be dispensed with – a method that is required, for example, when placing amalgam fillings.
Indications (areas of application)
Filling adhesion to the tooth by means of dentin adhesive systems is always useful when the dentin bonding agent can also form a chemical or micromechanical bond with the filling material, for example in the case of:
- Composite fillings (resin fillings)
- Composite fillings
- Resin inlays
- Cerec inlays
- Ceramic inlays
- Polymer glass inlays
- Veneers (veneers)
- All-ceramic crowns
- Partial ceramic crowns
- Adhesive bridges (adhesive bridges)
- Core build-ups made of composite material before crowning.
- Fixation of root pins
Contraindications
- Allergy to composite material
- Lack of compliance (ability to cooperate) on the part of the patient
- No relative or absolute draining possible, i.e. insufficient possibility, e.g. in case of deep subgingival (reaching below the gingival margin) cavity, to protect it from saliva ingress
Before the procedure
The tooth must be prepared to receive a filling by caries excavation (removal of the caries).
The procedure
To understand the procedure, one must first understand the structure of the dentin (tooth bone). The mineralized hard substance of the dentin is interspersed with 10,000 to 50,000 fluid-filled tubules (tubules) per mm², which communicate with the pulp (tooth pulp). The hard substance itself consists not only of the minerals that make it hard, but also has a network of very fine collagen fibers. Adhesive cementation to dentin basically requires four steps:
- Conditioning
- Priming
- Application of the adhesive
- Application of the composite
1. conditioning
Conditioning is the etching of the dentin surface, which is usually done with 35% phosphoric acid. The acid is allowed to act on dentin of the 2nd dentition for 15 seconds, and on dentin of the 1st dentition (deciduous teeth) for a maximum of 7 seconds. After the exposure time, the acid is thoroughly rinsed off with the air-water spray for approx. 30 seconds. It washes away hard substance dissolved from the surface and the so-called smear layer. What remains is the network of collagen fibers freed of minerals and the pores of the dentinal tubules cleaned of the smear layer. These two structures are the prerequisite for the micromechanical bond that is desired. 2 Priming
A so-called primer prepares the dentin and the collagen fiber network for the absorption of the monomers, the basic building blocks of the resin filling material. It is of decisive importance here that the collagen network is not dried out and thus collapses, but is able to expand like a sponge due to sufficient surface moisture of the dentin. Only in this way can it be penetrated by the monomers. If the adhesive system is not water-based but acetone or alcohol-based, the dentin must be re-wetted, i.e. dentin that has dried out after conditioning must be selectively re-wetted with water (only the dentin, not the enamel) using a mini-brush. 3 Application of the adhesive
The key ingredient of the low-viscosity adhesive is the monomers, the basic building blocks of the composite material. These penetrate the collagen fiber network and also penetrate superficially into the dentinal tubules. After light-induced polymerization (chemical curing stimulated by light), the monomers are crosslinked to form the polymer and thus hardened.This polymer layer is now micromechanically anchored via tags (pegs) in the tubules and in the interpenetrated collagen fiber network. This composite, which is only a few micrometers thin, is called a hybrid layer. 4 Application of the composite
The next step involves chemical bonding to the actual resin filling by applying a layer of thin-flowing composite no more than 1 mm thick, called flow, which lines the entire surface of the cavity and reinforces the hybrid layer after light polymerization.
After the procedure
This is followed by the placement of the plug-resistant composite material using a layering technique.
Possible complications
Adhesive luting systems have now undergone many years of research and further development with the aim of facilitating practical application and saving time on the laborious procedure. Thus, from the classic multiple-bottle systems, in which each work step is carried out with a product equivalent to it, to the so-called single-bottle adhesives, quite a few variants are offered. The different systems are differently sensitive to technology, i.e. they react differently to errors in the process, for example:
- Conditioning for too long: Acid penetrates too deep
- Too short rinsing of the acid: acid residues
- Overdried dentin: collagen sponge has collapsed and cannot be penetrated
- Dentin too wet instead of just moistened: monomer can not penetrate.
- Adhesive layer was not light-polymerized: no solid hybrid layer is formed
- The layers of the flow or further composite were not completely polymerized
It is therefore of crucial importance for the practitioner to consistently adhere to the procedure specified by the manufacturer, because failure is pre-programmed by deviating from time or application specifications. This manifests itself in the form of postoperative hypersensitivity, which is caused by irritation of the pulp (tooth pulp) via the dentinal tubules. Successful dentin-adhesive composite filling depends on careful implementation of the procedural steps.
