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12 Aug 2020, 04:00 PM Berlin
Dr. Karl-Heinz Schnieder
In April 2017, a 52-year-old female patient presented at our dental clinic on her first visit. She exhibited really poor oral hygiene and had not visited a dentist for six years (Figs. 1 & 2). Her medical history was extensive: she had suffered from depression and been hospitalised for about a year. Hence, she desired for her teeth to be fixed permanently so that she could smile again. It is our practice not to propose implant treatment until we see that the patient is able to improve his or her oral hygiene, so we began motivational training to achieve this goal.
The first task we set ourselves was to restore oral health and eliminate all active bacterial outbreaks and remove the teeth affected by periodontal disease. Over the years, several authors have investigated the long-term maintenance of implants in relation to proper oral hygiene,1 and they all agree that there is a high risk of implant loss in the absence of good hygiene. We therefore made sure that the patient was followed up and motivated by our dental hygienist.
We then wanted to see whether the patient would be satisfied with a complete denture. Had that been the case, we would have considered placing four implants restored with a removable prosthesis with button attachments. As she expressed a desire for a fixed solution, we opted for the following treatment plan instead.
For this case, we chose to include the use of platelet-rich fibrin (PRF) membranes because, in our clinical experience, we have observed that this promotes faster and more effective healing. Modern studies2 have shown the benefit and potential of white cells in the inflammatory process in stimulating osteoprogenitor cells. PRF contains all monocytes, making bone graft stimulation more efficient.
We first extracted all the teeth affected by periodontal disease and provided the patient with a removable prosthesis. Shortly thereafter, her oral situation improved significantly. Later, we rehabilitated the mandibular arch with a Toronto prosthesis supported on six implants (Fig. 3).
Since the patient’s oral hygiene was substantially improved, we decided to reward her by delivering a fixed prosthetic solution immediately loaded on six BLX implants.
We started with a Summers’ technique sinus lift in region #16 and placed advanced platelet-rich fibrin (A-PRF) membranes. We also decided to leave in situ teeth #38 and 23, both of which were totally impacted. The latter was horizontally inclined. Since the incisive fossae and incisive foramina were quite wide, we decided to cut off the nasopalatine nerve at the caudal end and regenerate it with a biomaterial (maxgraft, botiss biomaterials) mixed with injectable platelet-rich fibrin (Figs. 4–6).
We placed Straumann Roxolid SLActive ø 4.5 mm implants in positions #13, 11, 21, 24 and 26, and a ø 5.5 mm implant in position #16. All the fixtures were 10 mm long, except for implants #13 and #24, which were 12 mm long (Figs. 7–9). On to the six BLX implants, we screwed six screw-retained abutments and, before closing the flap, we covered the fixtures with autologous A-PRF membranes (Fig. 10).
After the surgical steps, we started with the prosthetic phases. First, we protected the operational field with a rubber dam and took an impression with a polyether impression material (Permadyne, 3M ESPE; Figs. 11 & 12). In order to provide our dental technician with information about the vertical dimension and correct occlusion, we used a pattern resin and then fixed a transparent duplicate of the prosthesis on to the implants inserted in positions #11 and 21 (Figs. 13–15). A few hours after the surgery, the patient received a fixed and protected solution screwed on to six implants (Figs. 16–19).
Six months later, we produced the definitive impression by fixing the implants together with resin, increasing passivity and thus reducing tension (Figs. 20 & 21). The mucosa had healed extremely well and there was a large amount of keratinised tissue around the implants. This was great proof of the patient’s commitment to practising improved oral hygiene (Figs. 22 & 23).
We then proceeded to digital planning. In our full-arch restorations, we usually follow a partial digital workflow (Figs. 24–26). In this case, we chose a multilayer high-translucency zirconium dioxide ceramic (zerion ML, Straumann). We reproduced the vertical dimension with the provisional restoration and duplicated it with a radiopaque polymer (SR Vivo TAC, Ivoclar Vivadent) in order to obtain a digital wax-up (Figs. 27 & 28).
In using the zirconia, we discovered with our technician that the connector thickness in a Toronto prosthesis has to be at least 25 mm to be strong enough (Fig. 29). This material has excellent translucence and is highly resilient (Fig. 30).3
The buccal aesthetic veneers were layered and customised by the dental technician, and the entire monolithic structure was milled (Figs. 31–35). It was important to polish the zirconia perfectly on the occlusal surface in order to minimise abrasions (Fig. 36). Finally, it was extremely important to create sufficient cleaning space to permit use of interproximal brushes (Fig. 37).
We are very happy with the results we achieved, because for us it was not only a technical and clinical challenge, it was also a matter of caring for the patient on her path of personal growth and helping her to regain her self-esteem. Since she proved to have improved her oral hygiene significantly, she satisfied all the conditions for good long-term maintenance of the implants. After one year, she was very happy and satisfied and finally managed to smile again without being ashamed of her appearance (Figs. 38 & 39).
We are aware that, in a full-arch fixed rehabilitation, some chipping can occur of a veneered zirconia prosthesis. However, after a careful postural and chewing analysis, we concluded that, in her case, we could succeed with this solution in both the upper and lower arches. In order to avoid any risk, we also provided a Michigan splint for the patient to wear every night.
With their thread design and bidirectional cutting elements, BLX implants helped us considerably in this full-mouth restoration. The stability they offer is remarkable and they are highly efficient when it comes to immediate loading.