Jose Antonio Rojas Carvacho
Restorative dentistry has always divided the clinical and lab work into two whole different worlds, with clinicians constantly struggling with the communication issue and lab technicians trying to overcome the lack of empathy and knowledge about the crucial steps that are required from both sides to achieve excellence.
Facing a restorative situation by quadrants that mixes direct and indirect approach is a very common situation. This type of treatment could be, at some point, over absolute control of the dentist if some minimal lab work (and equipment) is incorporated into the practice.
This has several advantages in terms of efficiency and training, and also will improve our whole indirect approach, no matter how extensive, because we will be force to deliver the most delicate and detailed impressions and cast models. Why?
Because any mistake is going to be assumed and resolved by us, cause we will be in charge of the entire process. So that tiny bubble in the margin, that old fashion wax record, among some others typical things that could be of “little importance”, now are going to impact OUR outcome and we have no choice but to get better.
Also this kind of approach will facilitate the use of same material for cavity redesigning, prosthetic and cementation that is a constant philosophy in my practice trying to achieve the best result avoiding the interfaces between different materials and possible interactions.
6th generation bonding agent (2 bottles Self Etch) reports seems to show that the clinical outcome is more than acceptable and could be used safely. They are less controversial than one bottle systems and although i try to use 4th generation anytime that is available, many little tweaks could improve the normal outcome of the self etch bonding agents, and the simplification of the steps should be considered inversely proportional to the prognosis.
1.- A mid twenties female patient seek consultation about paint upon cold beverages, food impaction between molars and esthetic concerns when laughing with an open mouth. Initial situation shows anatomically challenged/fractured amalgams and several infiltrated composite.
2.- A close up look reveals different fractures and secondary caries. There is no possible reparation that could improve biofilm control so the replacement was indicated.
3.-Absolute isolation is more than a century old technique which importance is specially appreciated when we need to control saliva and breathing humidity in the lower arch for adhesive procedures. If restoring by quadrants, there is no other more relevant stress relief action for the operator and that will also save us time.
4.- The removal of amalgams is fast and conservative if specially design burs are used. Secondary caries is removed with low speed carbide burs and any corrosion staining will not be eliminated by rotatory, the same with composite or bases that is not easy differentiated from dentine.
5.- 27 microns aluminum oxide will be the technique of choice on the removal of any corrosion byproducts and also those very thin layers of composite that are left behind by burs or any non adhesive bases. The use of sand traps will facilitate the posterior aluminum oxide cleaning from the rubber dam and avoid its aspiration. Clean and treated surfaces will improve the adhesive outcome.
6.- After removal of failed restorations we should reevaluated our treatment decision. The molars are going to be restored with resin composite onlays and a direct resin composite will be used to rebuilt the second premolar. The extent was not the main reason for going indirect, but my experience with the technique that i consider to surpass the direct method for the improved biomechanics of post-polymerized resins and stress contraction taken to a minimum level.
7.- Any treatment that uses indirect and direct restorations, should be started with the direct techniques so the technician (in this case ourself) could have stable references and the contact areas could be managed through the indirect workpieces. A sectional matrix and separating ring is used and it is of utmost importance to double check the gingival matrix seal.
8.- Selective etching of enamel using 37% phosphoric acid for 20 seconds will compensate the acidic monomer action in an area where excellent bonding is crucial for long term success. A thoroughly, car wash like, spraying of water is mandatory after any acid etch. Always try to use 2% clorhexidine containing phosphoric acid because there is always a possibility of etching dentine next to enamel.
9.- A maleic acid based, moderate ph, 6th generation self etch adhesive system is going to be used through the entire process. Aggressive ph self etch systems should be avoided because of the calcium salts produced that are very unstable in aqueous environments.
10.- The primer is actively rubbed against enamel and dentine and solvent is evaporated until we see a bright surface.
11.- A second application of primer is indicated to improve the infiltration looking for compensate the buffer effect of the conditioning of smear layer and dentine collagen.
12.- A very thin layer of bonding is applied over the primed surfaces, any excess should be carefully removed.
13.- 1 minute polymerization.
14.- After a second layer of the bond is used, remove the excess with a dry adhesive tip. No polymerization.
15.- Selecting a good quality flowable composite is relevant because some brands are plenty of air inclusions that will impact our polymerization by oxygen inhibition.
16.- Covering the uncured bonding with a layer of highly filled flowable resin in 0.2 mm thickness, almost like a third layer of adhesive. They are polymerized together for another minute, so the air inhibition layer remains in the flowable and the adhesive is fully cured.
17.- A simple anatomical layering was used. It is started rebuilding the enamel proximal wall. I always recommend the the use of moderate intensity polymerization and at least 30 seconds per increment. 1 minute polymerization in the deepest areas of the proximal box.
18.- Next, very saturated dentine resin composite stratified in layers.
19.- Bleach shade composite was used as an intensive on the occlusal, before the final layer. Gold tints were applied in the most deep part of sulcus.
20.- The final step is an enamel composite with same refractive index than natural enamel, in one single layer and careful sculpting, trying to avoid posterior adjustments. Brushes are always recommended in this step. Final polishing will be achieved when the entire process is complete.
21.- The indirect restorations always start with Immediate Dentin Sealing. This is a proven method to achieve excellent bonding. It should start with cavity disinfection that can help us to remove any contaminants left by rotatory. Also contains 2% chlorhexidine, a well known MMP´s inhibitor. There is no definitive information in literature about when to use chlorhexidine to achieve the best result, so we saturate dentin with it at different times.
22.- 30 seconds selective etching of enamel using 37% phosphoric acid containing 2% chlorhexidine. This etching time will result in Type 1 enamel patterns. Moderate ph self etch adhesive is not strong enough to condition enamel. In this picture you can also check the dehydrated result of the restoration of the premolar.
23.- Same adhesive technique than the direct restoration is performed, with the only difference of a previous step. After selective acid etching, 2% clorhexidine is applied into dentine for 20 seconds without rinsing it away, and carefully drying the excess. Chlorhexidine will avoid the hybrid layer degradation, considering that recent evidence shows that nano infiltration is a real phenomena in self etch adhesive systems, so enzymatic activity will occur at some level.
24.- 1 minute polymerization.
25.- Second layer of bonding and thin layer of flowable, then 1 minute copolymerization. i want to emphasize how important is using really thin layers in all the adhesive steps to achieve the best results.
26.- The reconfiguration of the cavity towards an expulsive geometry will be achieved with nano hybrid resin composite. For this task we will use a sonic vibration spatula (170 kHz) named Compothixo from Kerr, that incorporates an eccentric oscillation micro engine. This vibration will improve the handling and adaptation of the composite modifying its viscosity. Also the condensation is facilitated and air bubbles are less like to be incorporated.
27.- Small increments of saturated dentine mass of resin composite are vibrated into the walls trying to modify the retentive nature of the previous geometry. Long and moderate intensity polymerization are always important
28.- After the completion of the walls rebuild and the filling of retentive parts we can cover the teeth with glycerine to avoid the contact with air.
29.- Final polymerization for 1 minute per tooth.
30- Fine grained stones can be used to smooth any irregularities and also to uncover the enamel of any composite.