TBU # 020: Immediate Dentin Sealing Protocols, Benefits, and Applications

Almost every day we deal with at least one case where caries have gone into dentin, and ever since adhesive resin was implemented in dentistry, the number of problems was increased especially the post-operative sensitivity, debonding or failure in the restoration, and secondary caries. These three are the main problems that we face in restorative dentistry. Immediate dentin sealing is an important step in your bonding protocol that will help you increase the bond strength, decrease the bacterial leakage, less gap formation and reduction in the post-operational sensitivity. Immediate dentin sealing is the application of a dentin bonding agent to freshly cut dentin when it is exposed during tooth preparation for indirect restorations (inlays/onlays, crowns). The idea behind it is that when we prepare teeth for any indirect restoration a lot of dentin will get exposed, and that exposed dentin will need to be covered and protected to prevent further problems.

As the name indicated, this procedure involves dentin. Dentin is the fundamental part of the bond is the hybrid layer, which is the infiltration of monomers into the collagen network. After polymerisation, the bond that will be formed is similar to the dentinoenamel junction. In dentin bonding, we try to copy the dentinoenamel junction. In total-etch systems, we can roughen the dentin with a diamond bur because it makes the dentin very rough (at the dentinoenamel junction the dentin is very rough like waves) and we copy that with diamond and that increases the contact surface. The success of the restoration depends mainly on the adhesive procedure. Bonding porcelain/ indirect restoration to dentin has an increased risk for failures, it is mainly because of dentin contamination and the collapse of the hybrid layer until it is polymerised. Therefore dentin should be immediately sealed before the impression taking.

Top seven reasons for implementing immediate dentin sealing:

1. Dentin contamination from saliva, bacterial leakage and provisional cements during provisionalization of the indirect restoration can reduce the bond strength.
2. Pre-curing of the dentin bonding agent leads to improved bond strength in comparison to bonding agent and composite that are cured together which can lead to collapsing and weakening of the hybrid layer.
3. Stress-free bond development: over time the completion of the co-polymerisation occurs allowing a significant increase in bond strength. When the dental bond is allowed to develop without stress (composite layering and shrinkage, occlusal forces), the restoration adaptation is significantly improved.
4. Patient comfort: because of the reduction of postoperative sensitivity, the provisional is more comfortable and less sensitive, and the delivery of the final restoration requires less anesthesia.
5. Preservation of the tooth structure: IDS increases retention (if it's used in full crowns), especially when we are dealing with tapered preparations and short clinical crowns. IDS will allow us to reduce the amount of dental structure that is needed to be removed because it's no longer depending on the retentive/resistance form, it is depending on the adhesive bond! This ultimately allows us to be more conservative with our preparations.
6. Ability to use light-cured dentin bonding agents: Because it is an individual step now, the usage of dual-cured bonding agents is limited.  Dual-cured bonding agents might have a negative effect on the mechanical or aesthetic properties.
7. Separate conditioning of enamel and dentin: This allows the practitioner to focus on the bonding to dentin and perform enamel conditioning later as a separate step on the day of delivery.

Freshly cut dentin is found only at the time of tooth preparation (before impression), it is advised to immediately perform IDS after tooth preparation and before impression taking, that's because the dentin bonding agent will add some thickness to the preparation (about 40 μm ) and it could interfere with the seating of the final restoration. Whenever an area of dentin has been exposed during tooth preparation for indirect bonded restorations, local application of a dentin bonding agent (DBA) is recommended.

How to do Immediate Dentin Sealing 

Before we start performing dentin sealing we need to identify dentin, which can be done by simply etching for 2-3 seconds, then drying properly. Enamel will appear frosty and dentin will appear glossy. After that we need a fresh layer of dentin, so we roughen the glossy area slightly with a diamond bur. If the dentin exposure isn't deep IDS is not recommended because sufficient space is needed for the final restoration and the dentin bonding agent in case of a concave area (margins) could reach up to several hundred micrometers. So it's not recommended in shallow margins. 3 step etch and rinse technique (4th generation) is recommended for immediate dentin sealing.

Immediate dentin sealing steps using total-etch (etch and rinse) systems:

1. Etching for 2-3 seconds to identify dentin (glossy areas)
2. Expose a fresh layer of dentin with a diamond bur
3. Immediately re-etch the freshly cut dentin with phosphoric acid for 5-15 seconds
4. Rinsing and removing the excess water with the suction drying method (negative air pressure)
5. Application of the primer 
6. Light air thinning of the primer to rid the solvents
7. Apply the resin adhesive
8. Light curing with the regular mode for 20 seconds
9. Application of a layer of air blocking material (glycerin gel) to and above the adhesive
10. Light curing with the regular mode for 10 seconds
11. Cavity design optimization (refining) could be performed and gently clean the surface to physically remove the oxygen inhibited layer (air abrasion\pumice)
12. Take Impressions

Delivery / Cementation of Indirect Restoration 

1. Roughening with a round bur at slow speed or micro sandblasting (air abrasion) of the adhesive resin
2. Conditioning of the entire tooth preparation (because dentin exposure is absent): Phosphoric acid etch for 30 seconds.
3. Rinse, dry and apply a coat of the adhesive (do not cure it, it will interfere with the seating of the final restoration)
4. Cementing of the final restoration as normal 

Important notes

• Over drying or excessive wetting of the dentin will cause a collapse of the dentin and nano leakage in the bonding leading to weakening of the bond

• Use caution with air-drying

• Working with 3 steps total-etch system is preferred because the primer comes alone,

  which will allow us to place the adhesive resin accurately

• You can apply the adhesive to the margins using a periodontal probe which allows more

  accuracy

• 3 step system allows us to apply the resin adhesive accurately, unlike the 2 step system

  where excess might get over the margin and into the gingival sulcus which needs to be

  removed by a bur

• In IDS adhesive should not be air thinned, thin layers of adhesive don't polymerise well

• The application of the air block material above the adhesive and light-curing helps

  polymerises the oxygen inhibited layer and prevent it to stick or interact with the

  impression materials (especially when using polyethers)

• Impression materials will interact with IDS. Different adhesives will have different thicknesses of oxygen inhibition.  When you air block the surface with glycerin, it doesn’t eliminate the oxygen inhibition layer completely, but it minimizes it so there is still a thin unpolymerized layer that should be physically removed

• Unfilled bonding agents could be used alongside flowable composite to perform IDS. But never use flowable alone because it does not penetrates well into the hybrid layer

• If you are using a highly filled bonding agent its okay to have a thick layer but if it's not filled you can reinforce the hybrid layer by adding a thin layer of flowable composite (when using SE bond for example)

• Composite could be applied above the IDS to block undercuts and maintain proper restoration thickness allowing for better polymerization of the luting

  After you seal the dentin you can move forward with impression taking, and provisional restoration, however, keep in mind that the sealed dentin surface can bond to the resin-based provisional materials. A separating medium like petroleum jelly could be used during the fabrication of the provisionals, and avoidance of resin-based provisional cements. It is recommended to limit the provisionals usage to a maximum of 2 weeks (to avoid the exposure of cured adhesive to the real fluids as well as water sorption).

  Important notes on Optibond FL by Kerr:

•  Filled adhesive

• Filled adhesives are more viscous and make a more uniform layer and thickness, and

  even if you would air dry gently, the adhesive is still thicker than the oxygen inhibition

  layer

•  Allows the dentin hybridization and the formation of a low elastic modulus liner which act

  as a stress absorber

• Conventional 3 step etch and rinse adhesives still perform most favorably and are

  more reliable in the long term

    

IDS has a positive influence on tooth structure preservation, patient comfort, and long-term survival of indirect bonded restorations.  IDS can be applied in posterior and anterior areas.  It is also helpful to do IDS prior to root canal therapy as it can help prevent dentin from contamination of the endodontic materials.  Immediate dentin sealing should be applied to everyday dentistry.

There are many sources on the topic.  This is just one of them.

https://www.semanticscholar.org/paper/Immediate-dentin-sealing%3A-a-fundamental-procedure-Magne/88887b23471d96ed3d521ad6c1780ddffa550c3c