#Edentulous 17. Jul 2020

Clinical case with the use of mini implants with limited bone availability in the lower jaw- A one year follow up

A clinical case report by Alessandro Perucchi, Serena Pedrazzini, Switzerland

The Straumann® Mini Implants with 2,4mm diameter with Optiloc® prosthetic connection have been designed to offer the patient a safe, long-lasting and financially relatively inexpensive cost-effective product; this mini implant system requires allows for a less invasive treatment plan, with faster healing and less post-operative discomfort.

The Straumann® Mini Implant, thanks to its apically tapered shape offers good primary stability, allowing for under-preparation of the site.

Due to its apically tapered design, this implant offers adequate primary stability with minimum site preparation.

The implant body made of Roxolid®, an alloy of zirconium and titanium has excellent resistance properties. In addition to maintaining good bone preservation, the implant surface of the SLA® gives the implant a high bone integration.

It’s a monotype implant composed with an Optiloc® retention system, based on ADLC carbon giving the system an excellent wear resistance, able to remedy divergences or convergences between implants up 40 degrees.

Initial situation

64-year-old, non-smoker and healthy female wears a regular full arch prosthesis in the upper arch for 15 years and in the lower arch for 40 years (Fig.1, Fig. 2.a,b). The causes of edentulism are unknown but premature teeth loss due to periodontal disease and ethnic-cultural factors is assumed. The upper prosthesis needs to be relined and restored in some fracture points, while the lower prosthesis needs more stability.

For several years, the patient has no longer been able to tolerate the adhesive glue for the lower prosthesis and continuous direct and indirect relining have not yielded any positive results.

The amount of bone available in the lower arch is extremely low, with a very narrow and pointed ridge in the front part and an almost non-existent ridge in the posterior zone; moreover, the poor presence of keratinized epithelium is noted.

In the front of the lower jaw the shape of the alveolar processes is presented with a "knife-edged ridge form, adequate in height and inadequate in width" (IV-According Class to the Cawood and Howell's Classification), in the back it is a "depressed ridge form, with some basilar loss evident "(class VI).

Procedure

Treatment planning

The real problem concerning the management of this patient was the anatomical limitation. The patient didn’t want an invasive treatment, as it would be the case with a bone augmentation. To have a complete view of the available anatomy, the conventional open flap surgical procedure was considered as the only viable option.

CBCT was performed to organize the planning and placement of the implants (Fig. 3).

Therefore our proposal was unique and it enabled us to meet all the criteria required by the patient: the insertion of 4 mini implants Optiloc® in the following regions: 34 (10mm), 32 (12mm), 42 (12mm), 44 (10mm) under open flap approach without immediate loading.

Given the knife edge morphology of the anterior cortex and therefore the absence of cancellous bone as well as the risk of high post-insertion fracture, we avoided an immediate loading approach by opting for a 6-weeks healing before loading the implants with the prostheses.

Surgical procedure

Given the minimum amount of crestal bone, as explained above, a surgical approach of bone exposure for the implant bed preparation with the opening of the flaps was chosen (Fig.4). Thanks to a minimally invasive surgical approach, it was possible to preserve the mental nerve by keeping a safe distance.

After preparing the alveolar ridge by rounding and removing the angular parts of the cortex (Fig.5. a,b), we started the preparation of the site with the needle drill. Subsequently, the implants were inserted maintaining an adequate insertion axis, using the paralleling posts (Fig. 6. a,b). The drilling speed was dictated by bone density - D2 (a cortical bone often with a relatively dense cancellous bone).

4 mini implants were inserted on sites 34 (10mm), 32 (12mm), 42 (12mm), 44 (10mm), mounted with vial cap (Fig.7) and with ratchet. As a final result, 4 implants  were successfully placed with a torque of 35 Ncm achieved but were not loaded immediately and finalized with cross-stitched sutures (Fig.8).

We delivered the prosthesis to the patient, creating space in the outlets of the corresponding optiloc abutments.

Prosthetic procedure

After 6 weeks (Fig.9) the patient came for impression taking to identify the position of the Optiloc®; the impression caps were positioned (Fig.10) and the existing prosthesis was used to take the impression and thus pack the master cast with the analogues (Fig.11).

After having created the space for the housings in the existing prosthesis, we have positioning the white mounting collars (Fig.11) on each Optiloc® abutment with the relevant matrix housing and retention insert, the second impression was done. Afterwards, the housings of the matrix in the prosthesis were created and the spaces between the matrices were filled with acrylic resin.

The patient's old prosthesis containing the Optiloc® matrices is therefore maintained.

Final result

We have achieved a good end result (Fig.12).

After one year, the patient had no problems the radiographic overview (Fig.13.)shows stable work over time with a good osseointegration of the implants.

Conclusions

The patient gave us positive feedbacks and her quality of life has definitely improved, while keeping her upper removable prosthesis .

With this System we have been able to avoid performing a bone augmentation while obtaining a good level of bone integration and stability of the implants (Fig. 14).