Insert systems are prefabricated ceramic inlays (mega-fillers) used to provide the patient with direct (made in the mouth) fillings that are matched in shape and size to special oscillating preparation instruments (sound-activated instruments used to work on the tooth defect). A ceramic insert is adhesively bonded to the tooth with composite (by micro-serration with resin), thus occupying an intermediate position between the composite filling and the ceramic inlay.
Indications (areas of application)
The application possibilities of a composite filling (resin filling) combined with an insert do not differ from those of a composite filling placed using the increment technique (multilayer technique):
- Average expansion of the cavity (of the tooth defect),
- The area in the occlusal region (occlusal surface area) or
- Located in the occlusal and proximal area (occlusal surfaces and interdental surfaces).
The insert technique combines the following advantages:
- Easier and faster work than with the multiple layering approach of the increment technique;
- Reduction of the plastic portion of the finished restoration and thus lower polymerization shrinkage (volume shrinkage of the plastic component during curing);
- Better light-induced curing of the plastic component in the depth of the defect, due to the fact that the ceramic insert material acts as a light guide;
- Standardized approximal surface, i.e. the contact surface of the insert to the adjacent tooth is shaped according to average values, which can be advantageous in many cases;
- Less expensive than a laboratory-made or chairside (milled in one session in the dental office) ceramic inlay.
This results in the following disadvantages in comparison:
- The standardized approximal contact can not meet all individual requirements for the shaping of the interdental space;
- As a supplement to the approximal insert, one cannot do without the increment technique in the occlusal surface area, which results in a significantly higher proportion of composite and thus subject to shrinkage than with the ceramic inlay, where only the joint to the tooth must be supplemented with composite.
Contraindications
- Intolerance to composite;
- Incompatibility with materials of the adhesive system;
- Need to include one or more cusps in the restoration; in this case, consider an onlay, overlay, or partial crown.
The procedure
- Excavation (caries removal);
- Preparation (grinding of the tooth): any preparation must in principle be as gentle on tooth tissue as possible with sufficient water cooling and the least possible removal of substance;
- Occlusal insert: the cavity (the tooth defect) is shaped with a standardized rotary instrument; a form-congruent insert is selected to match the drill;
- Proximal insert: a vertical slit is prepared in the marginal ridge with a small rotating diamond drill, leaving a thin enamel disc towards the interdental space; this is removed with a sound-activated system. Again, there are instruments congruent in shape to an insert system, resulting in a great accuracy of fit.
- Matrix creation (creating a molding band around the tooth);
- Conditioning (etching) the enamel with 35% phosphoric acid gel for at least 30 sec to create a microscopic retentive (holding) surface structure;
- Conditioning the dentin for a maximum of 20 sec to remove the smear layer, which would hinder subsequent bonding;
- Priming the dentin: applying a primer to the slightly moist dentin; the residual moisture maintains the collagen network of the dentin, allowing the primer to disperse within it;
- Bonding of the dentin: the adhesive (adherent), which is the actual chemical bond between the composite (resin) and the tooth, penetrates the prepared collagen network and the dentin tubules (pore system of the dentin). Light polymerization (curing, initiated by light) creates firm peg-like anchors in the tubules.
- Insertion of the insert: if the shape congruence between the cavity and the insert is high, thin-flowing composite is used for the bond to the tooth, otherwise the insert is pressed into normally viscous filling composite with a higher filler content without contact using a special holder; contact-free insertion is important because the inserts are chemically pretreated ex works to optimize the bond to the resin;
- Excess removal;
- Light polymerization (light-initiated curing of the plastic);
- Provision of the residual cavity with the increment technique (multiple application and polymerization of thin layers of composite);
- Fine finishing with polishing diamonds and rubber polishers.
