Extraction, implantation and immediate temporisation at the mandible 8 December 2014
A 54 year-old woman is referred for a complete implant-borne rehabilitation at the mandible. The patient does not present any contraindication to an implant treatment.
The patient received a partial prosthesis with a metal framework which she rarely wears due to the inconvenience caused essentially during mastication. Mandibular teeth are the cause of repetitive abscesses treated regularly with antibiotic therapy. Root perforations on some teeth, calcified canals on others and the failure of another endodontic treatment all point towards their extraction.
Figs 1a and 1b: The patient presents a variation in bone height between the symphyseal area and the posterior areas. The residual anterior teeth cannot be preserved due to past carious and endodontic complications.
The panoramic X-ray shows reduced osseous volume in the posterior region in comparison with the anterior region (Fig. 1b). A scan of the mandible shows satisfactory osseous volume in the symphyseal area making the immediate extraction implantation option possible (Fig. 1c and 1d). In the posterior areas, the available bone height is reduced, particularly in sector 4.
The decision was taken to extract all mandibular teeth and put 5 implants in the symphyseal area. Since the patient cannot stand the removable prosthesis, she has directed us towards a fixed and immediate temporisation solution.
Pre-implant prosthetic analysis
Although the implant placement does not present any particular technical difficulties, the prosthetic project requires further analysis. The pre-arrangement prosthetic will guide the position of the implants.
The harmony of the thirds of the face suggests that the vertical dimension is maintained thanks to a passive egression of anterior teeth. This phenomenon associated with abrasion has drastically reduced the prosthetic volume, particularly in height.
The principle behind the preparation of the surgical guide and the provisional bridge is identical to that of the preparation of a complete immediate prosthesis with one exception: the occlusion. We must bear in mind that the occlusion of the provisional bridge meets the specifications for a fixed prosthesis and not that of a complete removable prosthesis.
Preparation of the surgical guide
After the primary impression in alginate and the secondary impression with an individual impression tray in permadyne, the intermaxillary relationship is recorded using a base plate occlusal rim (Fig. 2).
Fig. 2: The recording of intermaxillary relationship using a base plate occlusal rim. The working models come from the secondary impression with an individual impression tray. Note the advanced abrasion of anterior teeth.
Then, the casts were mounted on an articulator with a vertical dimension deliberately augmented by 2mm at the incisors (Fig. 3a). In the event of overestimation of the vertical dimension, it would be easier to reduce it on the provisional than to increase it.
Figs 3a to d: After mounting on the articulator, the different mounting guide production steps involve creating space for the future prosthetic teeth and materialising the bone reduction in the guide. Once the mounting is done, it is duplicated in a reinforced transparent acrylic resin guide on the vestibular areas.
The incisal guidance is taken as a reference point for the teeth arrangement. The prosthetic height needed to put future natural size teeth in place is achieved at the expense of the crestal bone by reducing some of the plaster (Fig. 3b). In the apical part of the future dental necks of the teeth, a 3mm distance is respected to allow some space between the implant abutments and the future anatomic crown of the teeth. It is now possible to finish the aesthetic teeth arrangement.
A mounting duplicate is fabricated in transparent acrylic resin (Fig. 3c). The vestibular jagged side helps the visual control of bone level during surgery to reduce the crestal bone. The guide is hollowed out on the occlusal side from 46 to 36 (Fig. 3d).
After the extraction of the residual anterior teeth and a thorough cleaning of the alveoli, the crestal bone is reduced based on the information given by the surgical guide. Thereafter, in order to ensure good primary stability, 4 cylindrical implants and 1 conical implants are placed in the buccal corridor defined by the guide. They are optimally distributed to reduce extensions and ensure a base for sustentation to the prosthetic project (Fig. 4a).
A conical MUA (Multi Unit Abutment, Nobel Biocare) is screwed onto each implant. The peri-implant spaces are filled with Bio-Oss (Geistlich). Impression copings are fixed on the abutments as the flap is sutured with resorbable thread (Fig. 4b).
Figs 4a and 4b: After teeth extractions and cleaning of the alveoli, the reduction of the crestal bone is performed and 4 Branemark Mk3 4x13mm + 1 Replace 4.3x13mm (Nobel Biocare) implants are placed. Note the optimal distribution of implants on the arch. Impression copings are mounted on MUA abutments. The post-operative panoramic X-ray shows the distal implants inclined posteriorly, thereby reducing the future distal extension.
The same surgical guide will be used as an individual impression tray after its passive placement is checked by grinding the points that come into contact with the copings. Windows are opened in the vestibular area where each of the copings are. A horse-shoe shaped dental dam is used to protect the flap and avoid the tangling of the sutures on the impression material. A silicone dental rim, prepared on the articulator, is used so that the correct positioning of the guide can be easily found. The patient will keep the individual impression tray in place under occlusal pressure. Some autopolymerizable composite is injected with a gun through the openings around the transfers (Fig. 5). It is possible to add some composite on the occlusal surfaces at a later stage if gaps appear. The last step involves recording the centric relation with three Duralay resin dental rims.
It is then unscrewed and removed and the healing caps are quickly screwed on the MUA.
Fig. 5: After some alterations, the surgical guide now serves as an individual impression tray. A silicone dental rim helps find the correct positioning of the guide during the impression. An injectable composite is used as impression material. The centric relation is recorded using a Duralay resin dental rim.
The impression is treated like the impression of a complete removable prosthesis: boxing and plaster casting after filling the undercuts with pink wax and casting the buccal denture flange (Fig. 6a): After removal from the mould, the working model is mounted on the articulator with the help of the Duralay rims against the antagonist arch, itself mounted beforehand. Thus, the vertical dimension and the centric relation are preserved and the individual impression tray also prefigures the aesthetic arrangement.
Figs 6a to c: After boxing of the individual impression tray, the denture flange is cast following a plaster cast. The provisional bridge is mounted in wax and flasking follows. After reduction, occlusion adjustments to the articulator and polishing, the provisional bridge is ready. The clinical photo shows the provisional bridge 4 months after the operation.
The lab technician will produce the provisional bridge with resin teeth and wax. Flasking guarantees good quality resin for the entire bridge (Fig. 6b). The completion of all laboratory steps requires at least 6 hours of incompressible work.
Placement of the immediate provisional bridge
The placement of the provisional bridge is usually planned for the following morning.
After a cold sterilisation of the bridge, the healing caps are unscrewed and the bridge is screwed in at 15 N.cm. Occlusion adjustments are minimal when all the steps have been followed properly. The patient is seen again 2 weeks after and, then, 2 months after for check-ups (removal of sutures, occlusal adjustments, etc.)
The final prosthesis
Four months after the operation (Fig. 6c), the provisional bridge is removed and the angulated and straight MUA are tightened respectively at 15 and 35 N/cm. This step validates the good osseointegration of the implants. The individual impression tray used for the immediate impression (Fig. 7a and 7b) is used again for the impression of the final prosthesis which will be done in plaster. The advantage of the individual impression tray is that it represents the correct vertical dimension.
Figs 7a and b: After validation of the implants' osseointegration, a plaster impression is taken using the same individual impression tray that was used for the immediate impression.
After validation of a plaster core (Fig. 8), the lab technician carries out the aesthetic arrangement and a model of the titanium infrastructure that will be machined by CAD/CAM, which ensures a perfect passive placement. The provisional bridge is used to mount the working model on the articulator. Vestibular and lingual silicone cores record the prosthetic volume of the provisional bridge. Once the teeth mounted on the titanium infrastructure using wax are validated, flasking is performed and the final prosthesis is finished.
Figs 8: Before machined CAD/CAM of the titanium infrastructure (PIB, Procera Implant Bridge, Nobel Biocare), a plaster core validates the impression. Although not technically necessary, this step is important for validating manufacturer's infrastructure guarantee.
The placement consists primarily in cold sterilising the bridge controlling the tightness of the MUA and screwing the bridge at 15 N.Cm (Fig. 9a and 9). Access to the screws is closed with a composite placed on a cotton pellet. A control is planned after one month. Thereafter, maintenance involves removing (or not) the final prosthesis every six months or every year depending on the effectiveness of the patient's plaque control and based on her medical history (periodontitis, tobacco, etc.). At 5 years, the bone level stability is maintained around the implant collars despite a slightly higher bone remodelling of the implant in 45.
Figs. 9a to e: The provisional bridge satisfied the patient in terms of aesthetics and at phonetic and masticatory levels. Therefore, the final prosthesis is only an improved copy of the provisional bridge. Note that on the retroalveolar X-ray, the perfect adaptation of the framework on the pillars is observed
Fig. 10: This approach offered the patient an optimal fixed provisional solution and a natural transition to the final prosthesis without any adjustment period.
The extraction-implantation protocol and immediate temporisation offered this patient an aesthetic and functional, fixed temporary solution without having to go through the removable prosthesis phase which can be very difficult to sell to a patient from a psychological perspective. Moreover, the immediate temporary bridge is an excellent way of increasing the predictability of the immediate prosthesis because it serves as a "support" for all the prosthetic parameters, such as the vertical dimension, phonation, mastication, occlusion and aesthetics.
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Papaspyridakos P, Chen CJ, Chuang SK, Weber HP. Implant loading protocols for edentulous patients with fixed prostheses: a systematic review and meta-analysis.Int J Oral Maxillofac Implants 2014;29 Suppl:256-270.
Private practice limited to Periodontology and Implantology
Paris, Founder of the IFCIA Institute.
Postgraduate degree in surgical and Prosthetic Implantology, Paris University, Paris.