Enzo Attanasio

Case by Dr. Enzo Attanasio

The selection of the restorative material is a crucial step in prosthodontics. Hybrid ceramics offer a range of properties well-suited for various therapeutic situations, both in the presence of vital teeth and of endodontically treated teeth. Using the example of a clinical case, this article will explore the advantages associated with the use of hybrid ceramics in a cracked tooth syndrome scenario.

INITIAL SITUATION

The affected tooth in this case was a mandibular right second premolar (45 according to the FDI notation) with an old amalgam restoration (Figs. 1 and 2). The patient experienced pain upon chewing (specifically upon release). Clinically, there were visible horizontal and vertical crack lines. The tooth was vital and showed no signs of pulpal pathology. It was decided to replace the amalgam restoration and restore the tooth with an overlay made of the hybrid ceramic KATANA™ AVENCIA™ Block. There were two main reasons for this decision. First, whenever root canal treatment would be necessary in the future, the hybrid ceramic material would facilitate endodontic access cavity preparation (compared to any other ceramic material) and subsequent restoration with composite filling material. Second, hybrid ceramics offer greater resistance and improved mechanical properties compared to composite filling materials applied in an incremental layering technique.

Fig. 1. Initial situation: Occlusal view.

Fig. 2. Initial situation: Buccal view.

PREPARATION AND IMMEDIATE DENTIN SEALING

To remove the amalgam restoration and weakened surrounding tooth structure, the occlusal surface of the tooth was reduced by approximately 2 mm. For a smooth colour transition between the tooth and the restoration, the preparation outline was created at the level of interproximal boxes with a vestibular inclined plane (Fig. 3). Subsequently, Immediate Dentinal Sealing (IDS) was carried out (Figs. 4 to 10). This technique involves the use of a universal adhesive like CLEARFIL™ Universal Bond Quick, which is applied to the preparation without prior etching of the peripheral enamel. In the second step, a highly filled flowable composite is applied. In the present case, the material of choice was CLEARFIL MAJESTY™ ES Flow Super Low, applied in a thickness of just 0.5 mm. The preparation was refined using ultrasonic instrumentation: Sonic tips SFM7 and SFD7 (Komet Dental) for refining the boxes; SFD1F and SFM1F (Komet Dental) for margins and steps. Sharp edges were rounded with abrasive discs and then polished with fine polishers. It is crucial that the residual occlusal thickness (prosthetic space) is 1.5 mm, as required by the selected material.

Fig. 3. Prepared tooth structure prior to immediate dentin sealing.

Fig. 4. IDS: Application of the universal adhesive.

Fig. 5. IDS: Light curing of the adhesive layer.

Fig. 6. Thin layer of flowable composite applied to the preparation.

Fig. 7. Contouring, …

Fig. 8. … rounding off sharp edges …

Fig. 9. … and polishing of the sealed surface with dedicated instruments.

Fig. 10. Sealed tooth preparation ready for impression taking.

FROM SCANNING TO TRY-IN

Following digital scanning with the intraoral scanner Primescan™ (Dentsply Sirona), MDT Daniele Rondoni produced the restoration (Figs. 11 and 12). The cementation process involves an initial try in phase to assess the marginal fit of the overlay and the contact areas. Testing occlusion at this stage could be risky as it may lead to fracture of the restoration in case of excessive premature contacts. After try-in (when carried out without rubber dam), the restoration may be contaminated by blood, saliva, or glycerin gel used for the evaluation of fit and aesthetics. Therefore, it is necessary to clean the restoration before proceeding with adhesive phases. The use of a cotton pellet soaked in alcohol is an option, a cleaning agent like KATANA™ Cleaner may be even better as it chemically cleans the restoration and eliminates the contaminants.

Fig. 11. Hybrid ceramic overlay on the printed model.

Fig. 12. Separate overlay.

CONDITIONING OF THE TOOTH AND THE RESTORATION

Afterwards, the restoration was sandblasted (as recommended for most hybrid ceramics) with 50 μm aluminum oxide using AquaCare (Akura Medical) (Fig. 13), and then immersed in distilled water in an ultrasonic bath for 5 minutes. Meanwhile, rubber dam was placed over the entire sextant, the build-up was sandblasted like the intaglio of the overlay and a phosphoric acid etchant (Ultra Etch, Ultradent) was applied to the enamel, rinsed off and the area dried (Figs. 14 to 17). The clean restoration was subsequently conditioned with a silane containing 10-MDP (CLEARFIL™ Ceramic Primer Plus, Kuraray Noritake Dental Inc.) according to the manufacturer’s instructions (Fig. 18). What followed was the application of the universal adhesive (CLEARFIL™ Universal Bond Quick) to the intaglio of the overlay and to the preparation and light curing on both sites (Figs. 19 and 20). One of the advantages of universal adhesives compared to three-step adhesive systems is their minimal film thickness, which does not compromise the fit of the restoration.

It is important to protect adjacent teeth with metal matrix strips during adhesive phases to provide for proper fitting. These elements do not create operational difficulties, but serve their purpose: After restoration placement, the composite or cement used for placement will be easily removable from the mesial and distal surfaces of the adjacent teeth, as they are free of adhesive.

Fig. 13. Sandblasting of the overlay …

Fig. 14. … and the tooth structure.

Fig. 15. Selective etching of the enamel, …

Fig. 16. … followed by thorough rinsing. Adjacent teeth are protected by a metal matrix strip.

Fig. 17. Tooth structure after selective etching, rinsing and drying.

Fig. 18. Silane application.

Fig. 19. Application of the universal adhesive into the overlay.

Fig. 20. Treatment of the tooth structure with the universal adhesive.

DEFINITIVE PLACEMENT

In the present case, a heated composite paste (heated to a temperature of 55 °C) was extruded into the restoration, which was then placed by applying slow, gradual, and strong pressure (Figs. 21 and 22). Excess composite was removed with a scaler in the buccal and lingual areas and floss (e.g. SuperFloss®, Oral-B) in the interproximal areas. Several pressurization phases were performed until no more composite was observed at the tooth-restoration interface.

Fig. 21. Heated composite paste used for definitive placement.

Fig. 22. Restoration placed under rubber dam isolation.

Then, the composite was polymerized for 30 seconds from the buccal and lingual sides with two curing lights, before applying glycerin gel to the margins and polymerizing from occlusal for another minute (Fig. 23). If thorough attention is given to removing excess composite during placement phases, subsequent finishing steps will be quick and easy (Figs. 24 to 27). Finishing and polishing of the interproximal areas was accomplished with an EVA handpiece and 3M™ Sof-Lex™ Finishing Strips (3M). For finishing of the buccal and lingual areas, a medium-grit, flame-shaped diamond bur (diameter 14/16) was used. Finally, the margins should be polished using composite polishers like TWIST™ DIA for Composite (Kuraray Noritake Dental Inc.). After the local anesthesia wears off, one should observe the cessation of pain symptoms, as seen in the present case. The treatment outcome is displayed in Figures 28 and 29.

Fig. 23. Light curing through a layer of glycerin gel blocking the oxygen.

Fig. 24. Finishing of the buccal and lingual margin with a medium-grid, flame-shaped diamond bur.

Fig. 25. Finishing of the interproximal areas with EVA handpiece (fine grain).

Fig. 26. Checking the occlusal contacts.

Fig. 27. Occlusal polishing.

FINAL SITUATION

Fig. 28. Treatment outcome – buccal view.

Fig. 29. Treatment outcome – occlusal view.

CONCLUSION

For posterior teeth restored with amalgam and a significant level of destruction, restoration replacement with hybrid ceramic overlays can be a great option. Mechanical material properties are usually superior to those of layered composites, processing is possible chairside or labside and comparatively quick (no firing required), while the clinical placement procedure is similar to that involved in placing glass ceramics – with the major difference of sandblasting instead of etching the intaglio of the restoration. One of the most important benefits of hybrid ceramics over glass ceramics, however, is the ability to modify the restoration whenever desired. Endodontic access cavities are easily prepared and closed with composite, contact points are quickly adjusted and the surface is polished or re-polished in next to no time. Moreover, the wear properties are similar to those of tooth structure and patients are happy about a natural touch and feel. The aesthetic properties are quite impressive, too.

Case by Dr. Enzo Attanasio

The introduction of new-generation composites, equipped with nanofillers and highly loaded, has opened doors to new techniques for managing direct and semi-direct restorations. In particular, over the last ten years, there has been a significant revolution in the world of flowable composites. Nowadays, these materials offer a filler percentage very similar to packable composites through precise interventions in resin matrix management. They come in various viscosities, offering numerous advantages both in terms of handling and clinical use, as well as beneficial mechanical and physical characteristics.

FLOWABLE INJECTION TECHNIQUE

This new era of flowable composites has seen the development of a technique known as the Flowable Injection Technique (also referred to as injection moulding). It enables dental practitioners to reproduce anatomical forms created by a dental technician in the laboratory through a diagnostic wax-up. The shapes planned on the model are transferred directly in the patient's mouth using transparent silicone matrices or indexes, into which the composite is injected through specific injection holes.

The main difference compared to traditional mock-ups is that the reproduced dental elements remain separate from each other. This technique provides predictable results identical to those developed on the technician's wax-up, requiring less chair time than direct veneering and offering a longevity similar to traditional composite restorations.

BENEFITS AND CHALLENGES

The major benefit of this technique is the faithful reproduction of morphological details that the technician creates on the diagnostic wax-up, which the clinician can reproduce with minimal effort. The restoration produced through the flowable injection technique, if all steps are followed correctly, requires minimal finishing by the clinican, who only needs to focus on polishing the composite.

However, one limitation is the difficulty in isolating the operative field, often requiring a split-dam technique or labial retractors, with all the associated adhesive challenges. The use of a rubber dam is only feasible if the peripheral dental tissues around the restoration are euchromatic, allowing the technician to create a wax-up with supragingival preparation margins.

Another compromise with the flowable injection technique is the management of the composite as a single mass. This makes it only possible to reproduce natural incisal translucencies typical of young patients by performing complex cutbacks and subsequent incisal painting. Without specific operator skills, the outcomes of this time-consuming manual procedure are unpredictable.

HYBRID TECHNIQUE: BEST.FIT

To leverage the advantages of both classical direct anterior restoration and flowable injection techniques and eliminate the limitations, a hybrid technique known as BEST.FIT (Buccal Enamel Shade Through Flow Injection Technique) has emerged. This technique allows the operator to manage the delicate phase of reproducing the buccal enamel layer of the anterior restoration through the flowable injection technique, keeping certain aspects in mind during the injection phase.

PROCEDURE

The transparent silicone key used for the creation of the buccal enamel layer is similar to the one used in the original flowable injection technique. The initial phase of restoration management follows all the classical steps of direct technique, requiring isolation with rubber dam. The palatal enamel layer is recreated with a highly translucent packable composite, and the palatal portion of the interproximal walls is produced using a suitable matrix system. Then, the core of the restoration is defined with opaque masses, creating mamelons and adding incisal effects. It's crucial to control the residual enamel thickness using a vestibular silicone index, aiming for about 0.3 mm of space. The buccal portion is finally reconstructed during the injection phase. The transparent silicone index created on the wax-up should be tested after each reconstruction phase to ensure passive insertion.

After creating the restoration core, the element to be injected is separated from the contiguous ones with thin PTFE tape. The transparent mask is then inserted, and fluid composite is injected through the injection holes to precisely reconstruct the buccal enamel thickness. The composite tip should be positioned at least halfway through the buccal surface, and the injection should be slow and controlled to avoid air bubbles in the material.

FINISHING

Following a 40-second polymerization vestibularly and occlusally, the transparent matrix is carefully removed, and excess interproximal composite above the PTFE tape as well as any remaining composite cylinder from the injection holes are removed. After completing all restorative elements, the rubber dam is dismantled, and composite excess is finished. After checking the occlusion, the composite is polished, usually requiring no further intervention.

CASE EXAMPLE

Fig. 1. Female patient with discoloured anterior restorations desiring a smile makeover.

Fig. 2. Close-up of her maxillary anterior teeth.

Fig. 3. Restorations in need of replacement: Lateral view from the right.

Fig. 4. Restorations in need of replacement: Lateral view from the left.

Fig. 5. Printed model based on a digital diagnostic wax-up based on a digital impression.

Fig. 6. Palatal silicone index produced for the conventional direct restoration steps.

Fig. 7. Transparent matrix with injection holes produced for the build-up of the buccal enamel layer using the flowable injection technique.

Fig. 8. Operative field isolated with rubber dam.

Fig. 9. Existing restorations removed and tooth surfaces roughened at the start of treatment.

Fig. 10. Palatal silicone index positioned intraorally for the build-up of the palatal wall.

Fig. 11. Checking of the space available in the vestibular area with a second silicone index.

Fig. 12. Etching with phosphoric acid etchant.

Fig. 13. Application of a universal adhesive (CLEARFIL™ Universal Bond Quick, Kuraray Noritake Dental Inc.).

Fig. 14. Palatal walls built up with CLEARFIL MAJESTY™ ES-2 Premium in the shade A1E with the aid of the palatal silicone index.

Fig. 15. Build-up of the interproximal walls with CLEARFIL MAJESTY™ ES-2 Premium in the shade A1D and establishing of the contact points using anatomical sectional matrices for the posterior area placed vertically.

Fig. 16. Dentin core built up with CLEARFIL MAJESTY™ ES-2 Premium in the shade A2D. CLEARFIL MAJESTY™ ES Flow Super Low in the shade XW was applied on the mamelons, while CHROMA ZONE™ COLOR STAIN Blue (Kuraray Noritake Dental Inc.) was used to reproduce incisal translucencies in the spaces not covered by the dentin core.

Fig. 17. Try-in of the transparent matrix for flowable injection.

Fig. 18. Isolation of the adjacent teeth with PTFE tape for a one-by-one injection.

Fig. 19. CLEARFIL MAJESTY™ ES FLOW Low in the shade A2 (Kuraray Noritake Dental Inc.) injected for the anatomical shaping of the maxillary right central incisor.

Fig. 20. Situation after flowable injection for all four anterior teeth, light curing through the matrix, final matrix removal and excess removal.

Fig. 21. Treatment outcome …

Fig. 22. … with visible mamelons, natural incisal translucencies …

Fig. 23. … and a lifelike anatomical shape …

Fig. 24. … of the restorations.

CONCLUSION

Each work phase must be executed with extreme care to lay the foundations for a passive linking of all subsequent steps without creating difficult management situations. The BEST.FIT technique is a convenient and useful method for dental practitioners to manage multiple direct anterior restorations simply and predictably, especially in situations requiring complex rehabilitations with large restorations.