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16872 Views - Nov 2015

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The greatness of high-end aesthetic bonded restorations does not resides only on the aesthetics, but on their bond strength and their intimate adhesion to the healthy remaining structures, many times giving back to the tooth a lot of its original strength. When working additively this effect tends to increase. Cementation is the critical phase of these treatments and must be performed with the greatest care. In this article we will present a simple protocol using modern materials and taking the most of their advantages.

All the laboratory work was done by Mr. Daniele Rondoni, form Savona, a proud Styleitaliano member.

Initial problem, multiple unaesthetic restorations, misaligned teeth and mild discoloration, dark and white.
Lateral view shows cervical defects on the lateral and disproportions over all the anterior teeth.
On the right side we find as well plenty of defects, as the opaque aspect of the 11, previously treated endodontically and reconstructed with a fiver post, proximal stains and disproportions.
Occlusal view is one of the most important protections for analysis when planning veneers, this vision will indicate us how much material are we able to add or how much should we subtract. Working additively is of out-most importance and should be our goal as much as possible. We can appreciate here how much we can add material to both centrals and laterals, where the centrals will need small preparation (especially in the incisal area), the laterals will not need any preparation.
Mock-up from the wax-up stamped in the mouth, the additive material shows us now a very accurate situation of what the project is going to look like at the end of the treatment. Usually, immediately after the project is satisfactory, we can prep over this material. This wax-up is mandatory and it will help us in the following key stages. 1- Case acceptance, 2- Volumetric Guided Preparation (as mentioned above) 3- Provisionals, 4- Final work assessment.
Silicone guide placed and occlusal view of the teeth after being prepared over the mock-up resin. Note how little structure was removed. After this vestibular preparation, we can get rid of the mock-up and finish accordingly our proximal and cervical areas.
Veneers are cemented one by one under complete isolation. In this image, the detail of the isolation of the tooth 11 with a 212 clamp and the other proximal areas accessible through the other holes, note how the enamel surface of the 12 is untouched while the centrals as mentioned above required adjustments at the incisal level. All proximal an cervical margins are located in enamel. Composite build-up is previously treated with 50 microns Aluminium Oxide sandblasting to grant maximum boding levels as well in the old composite.
We decided to follow a total etch technique. The tooth is etched for 30 seconds with orthophosphoric acid.
In any etching technique, the complete elimination of the etching agent is of outmost importance, we recommend to wash generously for about 20 seconds in order to remove all the debris that the acid could left. Dry carefully when performing total etch as the collagen network can collapse if over drying. We can always choose the self-etching technique in case we need or want to dry thoroughly.
The aspect of the etched substrate. Preparation must look opaque and clean.
While preparing the intra-oral field, the feldspatic ceramic veneers are etched. If we etch with a 10% hydrofluoric acid we etch for 1:30 minutes, instead if we use 5% the recommended times is about 3 minutes. Make sure that the internal surface of the veneers look uniform and frosted, without the presence of debris, white spots or shiny areas. If that is the case, clean with phosphoric acid and etch again. If veneers do not remain clean we may consider air abrasion of the internal surface. (For Emax veneers we etch for 20 seconds)
Application of the bonding agent, in this case ScotchBond universal, which can act as a self-etching material or as a total etch. The bonding agent is scrubbed for 20 seconds.
After scrubbing movement the agent has to be thinned with air, assuring that there will be no excess in the surface that can interfere with the veneer passive setting.
Polymerisation should be done properly. Manufacturers recommend generally 20-30 seconds. We suggest to over-polymerize, this will grant us a strong hybrid layer even in areas where the light can not arrive from the intimate contact of the lamp but slightly further.
The internal surface of the veneer should be treated with Silane and then the bonding resin. In this case while using ScotchBond Universal, which has in its composition Phosphate monomers (MDP) and Silane, it has been reported to have similar bond strength values as for those silanised, that is why the use of Silane can be avoided. Both asseverations about Silane use or avoidance are backed with interesting scientific evidence. At this point we have to silanize the veneer before bonding, even if we could avoid this step because of the silane inside scotch bond universal. A lot of dentists still prefer to maintain the use of silane.
Bonding layer must be thinned with air generously in order to avoid a thick film that can interfere with the fitting of the veneer.
Polymerization strategy is exactly the same. An extended polymerization will help to increase the quality of the bonding layer. We recommend to polymerise for one minute only if we have thinned the layer of bonding to the maximum.
The cement is applied in the internal surface of the veneer. We recommend to use veneer cements, these are full light curing materials, which because of its consistency can be denominated as -heavy flowables- or -soft composites-. These kind of materials allow to the clinicians the following things. 1- Passive fitting of the veneer 2- When external light conditions are low, unlimited placement time 3- good stability of the material and less risk of voids due to its consistency 4- Excellent structural and surface properties due to its high filler content. 5- Proper excess removal due to the dense consistency.
The excess of the cement coming out from the margins, initially the gross excess is taken out with a hand instrument.
After removing the big excess a brush is passed to smoothen the margins and finish removing the small excess. After we are sure all the margins are correctly filled and there is no big excess of cement, we can proceed to polymerization.
Light passes properly through the whole veneer, especially in the incisal area. The more intimate the contact of the lamp is with the veneer, the better conversion of the material. Extended polymerization is strongly suggested.
A sharp curette (Eccesso, LM Arte) is used to remove cement and bonding excess from the vestibular and proximal margins.
Fine abrasive strips are used to remove the excess and finish the margins.
Extra-Fine abrasive strips are used to polish the proximal margins.
The final situation after one month. Look how the color is now uniform, proportions are better and the overall surface and texture are pleasing to both clinician and patient. A very small excess was take out from the mesial of the tooth 22, look at the bleeding area. Further controls will be done afterwards.
Lateral view of the excess that was removed.
Lateral view of 11 and 12, look how the sound tissues have healed properly.
Detail of the two centrals.

Conclusions

Conclusions

Of course every single step of a veneer case is fundamental and important. Cementation stage is the culmination of all those efforts. In the dental world we have a very polarized set of opinions where many colleagues complain about how everything debonds and other colleagues which seem to do heroic bondings without any problems. Our opinion is that the keyword is ENAMEL, if we respect the sound tissues and bond to the best of the substrates, we will achieve high clinical success. Respecting and following thoroughly the cementation steps will grant us high clinical success.
 

Bibliography

References
1.- Devoto W. Direct and indirect restorations in the anterior area: a comparison between the procedures. QDT Yearbook 2003;26:127-138.
2- Magne P. Composite resins and bonded porcelain: the postamalgam era? J Calif Dent Assoc 2006;34:135-147.
3- Paolone G., et al. Esthetic direct restorations in endodontically treated anterior teeth. Eur J Esthet Dent. 2013 Spring;8(1):44-67.

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