Immediate implants in the aesthetic zone (Part 2)

This is the second in a series of articles looking at the immediate provisionalisation, impression making and material choices in the aesthetic zone. By Edward O’Reilly BDentSC MDent CH and Ronan Allen BDentSC MSc

The pattern of placement, provisionalisation, impression making and materials chosen in the delivery of an immediate implant has changed over the past 15 to 20 years. We should now be happy that all of these stages can be done predictably in an effort to achieve a high level of aesthetics with long-term stability. With good clinical research and data we know that, by using appropriate care and technique, outstanding clinical outcomes are achievable.

The rationale behind immediate implant placement and its immediate restoration is to deliver a stable aesthetic provisional restoration for our patient but, more importantly, support the soft tissue and emergence profile of the soft tissue while preventing bone loss that is often associated with extraction of a tooth.

In this article, we hope to show a technique for provisionalisation of our anterior implant placements, the importance of good impression technique and how the choice of restoration materials and their emergence profile can influence the delivery of an aesthetic implant restoration predictably. We will show the techniques we like to employ and some of the pitfalls that should be avoided if we are to achieve success.

The immediate provisional implant crown

Sometimes the problem with our patients is their impatience! However, this should not be the motivation driving us towards immediate provisionalisation. The primary aim of this immediate restoration is to support the soft tissue profile that we see in a natural tooth scenario. If we lose this buccal profile then it is lost forever and efforts to ’bulk up’ the buccal area can lead to disappointing outcomes.

There are certain cases where immediate provisionalisation is not a runner. They are outlined opposite, but essentially we cannot compromise the long-term life of the implant and taking risks at this stage is ill advised.

If immediate implant restoration is not possible, then in our clinic we tend to restore initially with an Essix orthodontic retainer which has the missing tooth replaced inside the retainer with Protemp provisional material. If the patient wishes to have a ’fixed’ provisional while waiting for the implant to integrate then we also can provide them with a ’Rochette’-type fixed partial denture that is bonded in the short term to the adjacent teeth (Figure 2).

Once the implant has been placed into the correct three-dimensional position and is of satisfactory primary stability, we can immediately start to restore. A pre-extraction cast or cast with wax-up of the desired tooth shape is required From this model, an Essix retainer is pre-made which clearly delineates the gingival margin position of the proposed final crown. This Essix retainer will provide us with the matrix for fabrication of the provisional crown.

On to the head of the implant we place our temporary plastic cylinder (Nobel Biocare). We aim to make provisional crowns screw retained as excess cement in a two-piece provisional implant crown can compromise healing. Usually, the temporary cylinder is too long and needs to be trimmed back in order to fit within the housing of the Essix retainer.

The matrix is then filled with provisional material (Protemp) and seated. The screw access is protected with the help of the shaft of a cotton bud or microbrush. The Essix matrix should not be overloaded as there is a risk of excess material getting between the implant and extraction socket wall. Excess material may also cause lock-in of the provisional crown beneath the proximal contact points which can make it difficult to remove. We need to be careful in this regard to avoid excessive forces being applied to the implant that has just been placed.

The provisional crown is trimmed initially and then the space between the temporary cylinder and margin of provisional material is filled with a flowable composite material. This allows for a smooth and easily polished transition from the implant to the gingival margin. This emergence must not create too much pressure on the facial tissue and the concave shape from implant head to gingival margin allows for tissue support but not excess pressure.

Final trimming, shaping and polishing can be done with the use of an implant replica out of the mouth. A series of laboratory diamond burs, Soflex discs and polish with flour of pumice can be used .

The final shape and emergence of the implant crown is essentially assessed by replacing the crown on the implant and ensuring that colour, contour and form of both crown and tissue is correct. The crown must support the soft tissue collar and occlusally must be free from contact in maximum intercuspation and excursive movements. Overload occlusally will cause early failure. The patient is instructed to maintain a soft diet and not to brush the area for seven days. The patient can keep the area clean using a chlorhexidine mouthwash for this period.

Impression making after immediate implant restoration and preferred choice of materials

Having tried hard to support the soft tissue around the implant with immediate provisionalisation, we must now transfer this information to the laboratory for fabrication of the definitive crown. The provisional crown is removed for the first time after three months’ healing which was supervised at one week, one month and just before impression making.

A healthy gingival condition is essential for long-term stability. A open tray impression is the preferred method of transfer and we can use acrylic around the impression coping to record the soft tissue profile. From this impression an accurate soft tissue implant model can be fabricated.

It is important that information is well communicated to the laboratory. This includes shade, type of materials used and whether or not the definitive restoration can be screw or cement retained. The implant placed is an immediate placement the angulation of final implant position may predispose it to being a two-piece cement retained restoration.

In the anterior zone, we are very comfortable using zirconium as the material of choice. Zirconium’s biggest advantage is that it offers us a tooth-coloured substrate that does not have that greying effect on the soft tissue, especially where the tissue type is thin. When recession occurs around our implant crowns, we can have immediate aesthetic failure of the restoration. We must endeavour to ’future-proof’ our implant restorations, ensuring that the aesthetic outcome is as good after 10 and 15 years as on the day of fit.

The strong and biocompatible NobelProcera Abutment Zirconia is available for both cement and screw-retained restorations. NobelProcera Abutment Zirconia is available in four shades – white, light, medium and intense.

When using a zirconium abutment, we can use a range of ceramic systems to help achieve our desired result. The types of crown that can be then chosen range from the more opaque zirconium crowns (Procera/Lava) to the more translucent glass-based ceramic systems (Empress/Emax). This choice is made depending on the appearance of the adjacent teeth to the one being replaced.

We must try to give our technicians as much information as possible about the adjacent teeth if we are to expect a really decent aesthetic outcome. It is without doubt imperative that digital photography is required if the laboratory process is to be successful. The use of photos with shade tabs in the image are so helpful as they give our technicians that point of reference and are able to include the subtleties of staining, fracture lines, fluorotic opacities, translucencies and colour. The final try in of the crown ultimately determines how successful we have been and again it may take a couple of attempts to get it to the standard you want.

The crown is returned from the lab and its fit, shape and emergence profile must be delivered upon as requested through the laboratory prescription. As we said earlier, the immediate implant placement may lend itself to having a two-piece cement retained crown on an abutment fabricated. This is to correct the angulation issue created by immediate implant placement.

Try in, assessment of fit, occlusal analysis, adjustment and then fit all need to be carried out with respect for the implant, its integration into the osseous tissue and the soft tissue. Removal of the provisional crown should always be accompanied with the application of chlorhexidine gel/mouthwash in an attempt to keep area healthy. Final torque of the abutment should be done with use of a standardised torque wrench and proper technique.

Cementing crowns on to implants is not without issue. One cause of local tissue inflammation associated with dental implants that has recently come to light is dental cement. Cements have been directly linked with peri-implant diseases and have been blamed for bone loss and implant failure. One aspect of the disease process that is especially concerning is the time between restoring the implant and the disease process. On average, three years pass before dentists discover a problem.

Many clinicians consider implants to be similar to teeth, but they differ in many important ways. A weak adhesion exists between soft tissue, connective tissues and implant surfaces, whereas teeth have a more robustly developed attachment system. The clinician should be aware of the fact that the weaker soft tissue adhesion seen with implants is more susceptible to complications caused by excess cement and the hydrostatic force of cement being pushed into the tissues during crown placement. Clinicians often do not understand that only a very limited amount of cement is needed to fix a restoration to an implant abutment.

It helps if the margin of the abutment/crown is placed just 1mm below the gingival margin to allow access for easier removal of any minor excess. This clearance of cement can be achieved with the use of a sharp probe and dental floss. There are techniques described elsewhere which, by the use of a silicone material, replicate the abutment and thereby allow a trial seating of the crown and extrusion of the excess cement just before final luting. It always is interesting to see how much excess is pushed out even with minimal cement application.

In conclusion, it is only with careful planning and technique that we are able to make the right choices for each individual case. This enables us deliver predictable aesthetic results.

 

Published: 23 July, 2013 at 13:33