Dental Tribune Middle East & Africa Edition

6 Dental Tribune Middle East & Africa Edition | July - August 2013MEDIA CME mCME articles in Dental Tribune have been approved by HAAD as having educational content for CME credit hours. This article has been approved for 2 CME credit hours. Centre for Advanced Professional Practices (CAPP) is an ADA CERP Recognized Provider. ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. CAPP designates this activity for 2 continuing education credits. S ince 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). Immediate Rehabilitations Of Atrophic Jaws Using Tilted Implants By Enrico Agliardi, Matteo Clericò, Matteo Consonni, Davide Romeo ________________________ Fig. 2b Fig. 2a Fig. 1 Fig. 3b Fig. 4 Fig. 5a Fig. 5b Fig. 6 Fig. 7 Fig. 8 Fig. 9a Fig. 9b Fig. 10aFig. 3a

Dental Tribune Middle East & Africa Edition

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