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A powerful team
Close teamwork, optimum preparation and the use of highly esthetic zirconia materials for a successful treatment concept.
Tue. 27 April 2021, 12:00 PM
Teamwork at eye level is our common approach. We have been working very closely and very successfully in this constellation since 2003. In addition to our “daily business”, we also attend training courses together to ensure a better exchange between laboratory and practice. The topic of conflict management is also a matter which we hold in high regard. If something doesn’t work, it has to be communicated in the same way as if something is doing extremely well, and of course, always in a factual and respectful manner.
Our first encounter with Amann Girrbach’s zirconia was in the year 2007. However, at that time still as material for the Ceramill Multi-X copy milling machine. With the digital boom in the dental industry, the CAD/CAM zirconia blanks also found their way into our laboratory. Meanwhile we use the full material variety of the Zolid portfolio to meet individual patient requirements. In the past 11 years we have fabricated and integrated over 5,000 crowns and bridges – with a failure rate of less than 1 %.
Using the right materials
The individual use of the Zolid DNA portfolio delivers a high degree of reliability, esthetics and clinical benefits. Already at the planning stage, a distinction must be made between monolithic and ceramic veneered restorations. Due to their high esthetics, the latest generations of zirconia available on the market can also be used monolithically, particularly in the posterior region. As a result of the good mechanical properties, wall thicknesses of up to 0.5 mm can be achieved and therefore also a preparation that is gentle on the tooth substance. The consideration of minimum wall thicknesses, preparation guidelines and the creation of sufficient space by the clinician influence on the quality and functionality of the dentures. In the following context we would like to show you our preparation scheme using a three-unit Zolid FX Multilayer bridge as example.
Step by step to the perfect preparation of a 3-unit posterior bridge
There are numerous instruments on the market for the preparation of all-ceramic restorations. Due to my many years of experience, I can now resort to only six tools, which lead to a successful preparation.
As a first step, the premolar was prepared after the removal of the old bridge. First a metal matrix is inserted (Fig. 1) to protect the adjacent tooth, then separation begins with a coarse torpedo (12 mm, green ringed) (Fig. 2+3). I use the same tool for pre-preparation (Fig. 4). This is followed by preparation of the crown alignment at a 45° angle and the fine preparation of the chamfer with torpedo (12 mm, red ringed) (Fig. 5). The pearshaped diamond (1 mm, green ringed) is particularly suitable for incisal trimming (Fig. 6). Here, care must be taken to create sufficient space for the esthetic and functional occlusal chewing surface, if the bite situation allows. Then the occlusal finish is accomplished with a fine diamond (red ringed) and final smoothing with the Eva file (red ringed) to avoid sharp edges at the cusp tips (Fig. 7+8). The molar crown is prepared according to the same principle.
Practical tip: as for the terminal abutments, I leave an occlusal stop for finding the correct bite situation (Fig. 9). This way I do not prepare the entire occlusal surface, but leave contact points for bite detection.
In the case of very low stumps, conical retention grooves can be prepared with the conical roller in the premolars as well as in the molars (Fig. 10-13). This significantly increases the surface area and the bridge already has a perfect hold even before actual cementation. Decementation can therefore virtually be ruled out. Then the impression is taken and sent to the laboratory.
Fig. 1 - Separation of the premolar with interdental wedge / adjacent tooth protection
Fig. 2 - Separation with coarse torpedo 12 mm (green ringed)
Fig. 3 - Occlusal view after separation
Fig. 4 - Pre-preparation 12 mm torpedo (green ringed)
Fig. 5 - Preparation of the crown alignment 45° and fine preparation of the chamfer with torpedo 12 mm (red ringed)
Fig. 6 - Incisal trimming with football (green ringed) for optimal esthetic results
Fig. 7 - Occlusal finish with fine football (red ringed)
Fig. 8 - Final smoothing with Eva file (red ringed)
Fig. 9 - Occlusal stop for finding the bite situation
Fig. 10 - Pre-preparation of the posterior crown with 12 mm torpedo (green ringed)
Fig. 11 - Fine preparation of the chamfer with torpedo 12 mm (red ringed)
Fig. 12 - Preparation of the crown alignment 45°
Fig. 13 - Applying the retention groove with conical roller (red ringed)
Design and refinement of the restoration with Zolid FX Multilayer in the dental laboratory
After taking the impression in the laboratory, we first created the saw-cut model on which the retention grooves are already clearly visible (Fig. 14+15). A 3-pontic bridge made of monolithic zirconia was chosen for the restoration in the posterior region. To provide for maximum esthetics, we used the super-highly translucent Zolid FX Multilayer in shade A2/A3 for this case. Due to the high translucency of the material and its use in the posterior region, we can dispense with veneering. The strength of 700 MPa also adds to safety, especially in comparison with other glassceramics.
After designing the bridge using CAD software, milling in HD mode and overnight sintering, the bridge is finished and the occlusal contact points are pre-polished. Due to the high precision of the Ceramill Motion 2, the retention grooves are milled precisely and in great detail (Fig. 16+17).
This was followed by stain firing and further firing with glaze material. Due to the pre-staining of the material including the color gradient, simple stain firing is completely sufficient to create the final highlights. (Fig. 18). The contact points were checked after glaze firing In the articulator, partially rubberized again and finally polished. This creates a polished, smooth surface in the contact area to the opposing jaw – a solution which is gentle on the antagonist!
Due to the prepared retention grooves, the bridge already has a perfect hold during the individual fit (Fig. 19+20) regardless of molar or premolar. This also offers significant advantages during subsequent cementation of the bridge and allows the dentist to find the correct position immediately.
Fig. 14 - Conical retention grooves on the stumps of the saw-cut model
Fig. 15 - Conical retention grooves on the stumps of the saw-cut model
Fig. 16 - Precisely milled retention grooves before and after the sintering process
Fig. 17 - Precisely milled retention grooves before and after the sintering process
Fig. 18 - Restoration after glaze firing
Fig. 19 - Perfect hold due to retention grooves even during the individual fit
Fig. 20 - Perfect hold due to retention grooves even during the individual fit
Choosing the right luting material is critical
In these cases, I use the self-curing glass ionomer cement “Vivaglas CEM” from Ivoclar Vivadent, a translucent, conventional luting material. This material combines highly esthetic results with high efficiency by providing ideal handling through easy excess removal. After insertion, the excess cement is carefully removed and the occlusion is checked.
Shiny surfaces with the 2-stage polishing system
As we have refined our model management by integrating an occlusion protocol, grinding corrections in the occlusion with fine diamonds are rarely necessary (Fig. 21+22). Usually it is sufficient to rework individual contact points first with abrasive and then with the fine, diamond polishers of the 2-stage polishing system (Fig. 23-26). The Zolid Polishing Dent Kit offers all the tools I need for this.
The shade of the bridge blends very well into the patient’s situation. The image was photographed immediately after insertion and the gingiva is not yet completely regenerated (Fig. 27). These results can only be achieved with good preparation, direct coordination with the laboratory and a good technique using highly esthetic zirconia materials.
Fig. 21 - The diamond or the grinding tool is used for small corrections.
Fig. 22 - The diamond or the grinding tool is used for small corrections.
Fig. 23 - First step; the surfaces are polished smooth with different polishing heads e.g. “swivel”
Fig. 24 - Or the polishing head “flame” can also be used for the first polishing
Fig. 25 - Second step; high-gloss polishing of the surfaces for an antagonist-gentle surface
Fig. 26 - Second step; high-gloss polishing of the surfaces for an antagonist-gentle surface
Fig. 27 - The final bridge adapts harmoniously to the patient situation