6 Dental Tribune Middle East & Africa Edition | July - August 2013MEDIA CME

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Since many years, rehabilita-tion according to the Brå-nemark protocol (Toronto-Bridge) has represented the

gold standard in case of full-arch fixed implant hybrid prostheses 1. This approach consists in four to six implants, axially placed in the pre-maxilla or in the interforaminal region of the mandible, supporting a fixed bridge with bilateral distal extensions (cantilevers) 2. Implant and prosthetic success rates were very high also in the long-term, exceeding 20 years of follow-up 3,4. The original protocol entailed a healing period of at least 3 months for the mandible and 6 months for the maxilla, neces-sary for the osseointegration of the implants before the prosthetic phases can start 1. Professor Brånemark, who stated the first protocol for implant dentistry 1, considered that period of time necessary for the integration of the implants. Today, this prerequi-site is no longer fundamental for the final success of the rehabilitation and implants can be loaded immediately after their placement.

In fact, as testified by recent consen-sus reports and systematic reviews 5,6, full-arch rehabilitations and im-mediate function seems to be a pre-dictable approach if precise guideli-nes during surgical and immediate prosthetic phase are followed. In all those papers, authors pointed out that the key factor for the immediate func-tion seems to be a minimum implant primary stability of 30 Newton 7. This can be achieved by using specific implant morphologies and osteocon-ductive surface in combination with a proper preparation of the surgical site that can guarantee a press fit of the implant and a stable bone enga-gement 8. Therefore, a rigid splinting of implants with a fixed bridge is also important to provide a firm fixtures stabilisation under occlusal load 9.

The use of tilted implants

The trend in modern implant den-tistry is the reduction of number of fixtures supporting a full-arch fixed restoration as well as the time elap-sing between surgical phase and pros-thetic loading. The lowest number was proposed with the Brånemark Novum concept 10, in which three implants of 5-mm diameter were in-serted in the interforaminal area with the help of a surgical guide and prefa-bricated components. This approach was not very versatile because of the prefabricated components and it was indicated only in patients with a spe-cific mandibular morphology and oc-clusal relationship. Therefore, the loss of one fixture led to complete failure of the prosthetic structure in a high percentage of patients. These results led to the conclusion that at least four implants, properly distributed, are required to support a fixed prosthesis and ensure long-term success. Earlier studies on immediate loading rehabilitations have included a high number of dental implants 11, spe-cifically when applied in the maxilla because of its poor bone density, but

recent reports have shown good out-comes with the use of only four or six implants.

In a recent technique called All-on-4 ™ (Nobel Biocare AB, Göteborg, Swe-den) 12,13, Paulo Malo proposed the use of two anterior implants placed axially in region of lateral incisors and two posterior fixtures tilted bet-ween 30 to 45 degrees relative to the occlusal plane. A provisional screw-retained prosthesis with 10 teeth can be delivered after fews hours from the surgery, while the final restora-tion will be made after 6 months. Medium-term results are very encou-raging; Malò reported 98.5% implant survival rate for 867 mandibular den-tal implants followed up for 10 years 14, while Agliardi showed 98.36% in the maxilla and 99.73% in the man-dible, respectively, up to 60 months of loading 15.

One of the innovative aspects of this technique is the inclination of the di-stal implant, which offers surgical and prosthetic advantages. By tilting the implants, it is possible to place longer fixtures and achieve higher levels of primary stability because of the gre-ater implant surface in contact with the bone 16. Furthermore, the area of emergence of the inferior alveolar nerve and the anterior wall of the maxillary sinus are characterised by a good bone quality and this enables clinician to find a solid mechanical support. Therefore, when implants are tilted distally, the prosthetic can-tilever is also reduced. Further pros-thetic consequences from implant

inclination consist of an increased interimplant distance, the creation of a more regular prosthetic polygon and an increase in the anteroposteri-or (AP) spread 17 compared with the Toronto-Brânemark rehabilitation, especially in mandibles of a rectangu-lar shape. With the reduction of the number of platforms, it is easier to achieve a passive prosthetic fit, both for the provisional and for the final rehabilitation. Patients can also main-tain optimal levels of oral hygiene because of the fewer number of sur-faces and the wider distance between implants.

Tests on models and by finite element analysis performed on single angula-ted implants showed that tilting im-plants may increase the stress to sur-rounding bone. Tilted fixtures may also be subjected to bending, possibly increasing the marginal bone stress. However, when the implant belongs to a multiple implant-supported pros-thesis, the spread of the implants and the rigidity of the prosthetic structure should reduce the bending 18,19. Furthermore, no difference in the marginal bone loss between tilted and axially placed implants placed either jaw has been reported 20, suggesting that tilting of the implants causes no detrimental effect on the osseointeg-ration process.

Immediate full-arch fixed prosthe-ses

Immediate loading procedures have gained high popularity among cli-nicians. The reduction of total time

of treatment and the possibility to deliver a functional implant bridge few hours after the surgery represent a notable advantages for patients. Therefore, partial edentulous patients with a failing residual dentition can avoid the psychological trauma and discomfort of a transitional removab-le prosthesis 21.

The rehabilitation of edentulous jaws is often complicated by a reduced bone quantity, especially in poster region, because of the pneumati-zation of maxillary sinus or for the superficialization of the inferior alve-olar nerve. To face these limitations, clinicians have different therapeutic options, such as long distal cantilever 22, the use of short fixtures 23, sinus lift and bone augmentation 24 or im-plants placed in specific anatomical areas such as pterygoid region 25, the tuber 26 or the zygoma 27.

Any of these procedures requires sur-gical and prosthetic expertise and has its own advantages, limits, risks and complications, involving sometimes high biological and financial costs. In the last years, different clinical studies assessed tilted implants as a feasible treatment option, with encouraging results in the medium term and no difference in bone loss compared to axially placed fixtures.

Case report

A 62-years old male patient was re-ferral to our office with a precise chief complain: fixing his failing dentition without going through multiple sur-

geries and in a relative short period of time (Fig. 1). His functional and esthetic demand was high, but he has financial limitations. He has re-movable partial prosthesis in both jaws, but now the mobility of the remaining teeth due to an advanced periodontal disease has compromise their stability in the mouth (Fig. 2-6). Therefore, he was not satisfied of his actual smile. After discussing possi-ble treatment options, we decided to exclude extensive bone grafts (sinus lift with lateral approach) and to use the residual bone available, restoring both arches with a hybrid titanium prosthesis supported by two anterior axial and two posterior angled fixtu-res, according to the All-on-4 ™con-cept. Final prosthesis will be realized with titanium CAD/CAM framework with nano-hybrid composite teeth (SR Phonares ® II, Ivoclar Vivadent) and using the IvoBase ® Injector.

Surgical and prosthetic phases

Implant surgery was done under intravenous sedation, starting with the upper jaw. After local anesthesia, compromised teeth were a-trauma-tically extracted and sockets were carefully debrided with sterile saline solution. Mid-crestal incision was done in keratinized gingiva starting from first molar region to controla-teral side and a mucoperiosteal flap was elevated exposing the vestibular bony wall and the palatal mucosa. Bone crest regularization was done with bony forceps and rotary inst-ruments whenever necessary. Distal implants were placed throughout the anterior sinus wall with an inc-lination of 40 degrees relative to the occlusal plane (Fig. 7,8), while two anterior fixtures were placed axially in positions of lateral incisors (Fig. 9). All implants have been inserted with a final torque of 50 Ncm. Angulated multi-unit abutments were connected to the tilted implants, while standard abutments were placed over anterior fixtures (Fig. 10). Sockets were filled with autogenous bone before closing the flap (Fig. 11). Same procedure was done for the mandible, with the place-ment of posterior tilted implants close to the mental nerve foramen and two anterior axial fixtures (Fig.12-17) . A fundamental part of the procedure consists in detecting the mental fora-men, isolating the emergence of the inferior alveolar nerve and evaluating the presence or not of the anterior loop with a periodontal probe. This structure represents the posterior anatomical limit for this type of reha-bilitation.

Once the surgical phase was finished, polyether impressions and vertical dimension registration were taken. Three hours after, full acrylic provisi-onal bridges with 10 teeth were deli-vered, keeping full contacts in maxi-mum intercuspation from canine to canine and avoiding any lateral excur-sion (Fig. 18-20). After six months, fi-nal restorations with titanium CAD/CAM Procera ® titanium frameworks (Nobel Biocare) were made and full occlusion with 12 teeth were given (Fig. 21-29).

By Enrico Agliardi, Matteo Clericò, Matteo Consonni, Davide Romeo________________________

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Immediate Rehabilitations Of Atrophic Jaws Using Tilted Implants

7Dental Tribune Middle East & Africa Edition | July - August 2013 MEDIA CME

ting nerve injury. Implant is placed in an underprepared surgical site to increase primary stability.Fig. 10a and 10b Anterior implants are axially inserted in position of la-teral incisors. Fig. 11 Occlusal view of mandibular implants with abutments.Fig. 12 Provisional acrylic prosthesis containing ten teeth were delivered three hours after the surgeryFig. 13a and 13b Full occlusal con-tacts are limited between canines with no lateral excursions Fig. 14 Verification of passive fit of ti-tanium CAD/CAM frameworksFig. 15a and 15b Final prosthesis will be realized with titanium CAD/CAM framework with nano-hybrid com-posite teeth and using the IvoBase ® Injector. Fig. 16a and 16b Final bridges contai-ning 12 teethFig. 17a and 17b Occlusal view of fi-nal prosthesis with limited posterior cantileversFig. 18 Lateral view of patient’s smile with the final restorationsFig. 19 Panoramic radiograph after one year of loading showing implants distribution and bone level mainte-nance.

References

1. Brånemark PI, Hansson BO, Adell R, Breine U, Lindstrom J, Hallen O, Ohman A. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year peri-od. Scand J Plast Reconstr Surg Suppl. 1977;16:1-132.2. Branemark PI, Svensson B, van Steenberghe D. Ten-year survival rates of fixed prostheses on four or six im-plants ad modum Branemark in full edentulism. Clin Oral Implants Res 1995; 6: 227-231.3. Adell R, Eriksson B, Lekholm U, Bra-nemark PI, Jemt T. Long-term follow-up study of osseointegrated implants in the treatment of totally edentulous jaws. Int J Oral Maxillofac Implants 1990; 5: 347-359.4. Ekelund JA, Lindquist LW, Carlsson GE, Jemt T. Implant treatment in the edentulous mandible: a prospective study on Branemark system implants over more than 20 years. Int J Prostho-dont 2003; 16: 602-608.

5..Esposito M, Grusovin MG, Achille H, Coulthard P, Worthington HV. In-terventions for replacing missing teeth: different times for loading dental im-plants. Cochrane Database Syst Rev 2009: CD003878.

Full list of references is available from the author.

Legends

Fig. 1 This 62-years old patient pre-sented with a clear chief complain: “improve my smile with a fixed resto-ration”Fig. 2a e 2b Intra-oral view showed few remaining teeth in the upper jaw and residual roots on the mandible. Partial removable prosthesis did not provided comfort during mastication and esthetic appearance anymoreFig. 3a e 3b Occlusal view of both arches with an adequate amount of keratinized gingiva Fig. 4 Panoramic x-ray evidenced bone loss in both arches due to chro-nic generalized periodontitis, with horizontal resorption and endo-perio lesions in the mandible. The extensive sinus pneumatization did not allow posterior implants placement without a preliminary sinus augmentation procedure. Fig. 5a and 5b Note the inclination of posterior surgical site compared to the anterior one. Thanks to the incli-nation, the posterior implant can be placed following the anterior sinus wall, getting an high level of primary stability. Fig. 6 Occlusal view showing implants distribution along the anterior maxil-la. All implants have been placed with a 50 Newton torque. 30 degrees abut-ments are positioned in the posterior implants to correct their inclination, while 17 degrees abutments are scre-wed on the anterior fixtures for a fa-vourable emergence of the prosthetic screw on the palatal side. Fig. 7 Post-extraction gaps were filled with autogenous bone before flap closure. The flap is sutured in a way to create a minimum 2 mm collar of keratinized gingiva all around every abutment. This peri-implant seal will be very important for the long-term maintenance of the entire rehabilita-tion. Fig. 8 Four verification pins evidenced the direction of surgical sites and the inclination of posterior osteotomies. Fig. 9a and 9b After isolation of men-tal nerve and verification of a possible anterior loop, the preparation of the surgical site is conducted with a me-sio-distal 30 degrees inclination, try-ing to engage the bone area anterior to the mental foramen without crea-

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Dr. Enrico L. Agliardi obtained his Doctorate in Medicine from the University of Mi-lano (Italy) and he specialized in Maxillofacial surgery and Orthodontics from the same university.

Contacte-mail:info@studioagliardi.it

Contact InformationDr. Davide Romeo graduated in den-tistry at the Uni-versity of Milano, Italy. He received his PhD in new Techniques in Oral Prostheses and Re-habilitation from the same university and he attended the Full time Advanced Program in Periodontics at New York University.

Contact Information

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