Zygomatic Implant Placement in Conjunction with Sinus Bone Grafting: the “Extended Sinus Elevation Technique.” a Case-Cohort Study

Zygomatic Implant Placement in Conjunction with Sinus Bone Grafting: The “Extended Sinus Elevation Technique.” A Case-Cohort Study

Marc Hinze, DMD1/Luc Vrielinck, DMD2/Tobias Thalmair, DMD1/ Hannes Wachtel, DMD, PhD3/Wolfgang Bolz, DMD1

Purpose: The zygomatic implant is mainly indicated for the rehabilitation of extremely atrophied maxillae when bone augmentation should be avoided. One drawback of zygomatic implants, which typically pass through the sinus, is initial or late bone resorption around the implant neck, which can result in oroantral communications followed by possible infection of the sinus. To decrease the risk of sinus infection, a modified technique was developed to preserve the integrity of the sinus membrane and to regenerate bone around zygomatic implants using an extended sinus grafting approach. Materials and Methods: Patients with extremely atrophied maxillae were provided with one to four zygomatic implants in conjunction with sinus grafting, plus conventional auxiliary implants, for immediate support of a provisional full-arch maxillary prosthesis. Definitive prostheses were delivered at 6 months after implant placement. All patients underwent clinical and radiographic examinations at 6 months. Results: Twenty-two zygomatic and 23 conventional auxiliary implants were placed in 10 patients. The overall 6-month implant survival rate was 90.9% for zygomatic implants and 100% for auxiliary implants placed in the anterior area. Only two minor technical complications were seen, and clinical indicators (including probing pocket depth, keratinized tissue, and plaque and bleeding indices) were good in all patients. A substantial gain of radiographic bone around the zygomatic implants was observed. Conclusion: The proposed technique led to successful prosthetic function for all patients. With the described technique, exposed implant threads within the maxillary antrum are eliminated and the potential for biologic complications is minimized. Oral Craniofac Tissue Eng 2011;1:188–197

Key words: atrophic maxilla, dental implants, maxillary sinus, peri-implant bone loss, sinus elevation, zygomatic implant

dentulous patients with an extremely atrophied sive bone resorption in the posterior region, widening maxilla present an especially difficult situation of the sinuses, and anterior alveolar bone resorption Efor implant-prosthetic rehabilitation. Progres- can dramatically reduce the possibility that a fixed implant-supported prosthetic reconstruction will be possible. Typically, these patients would have to be treated with bone augmentation techniques or onlay 1Private practice, Private Institute of Periodontology and or veneer bone grafting, combined with sinus floor Implantology, Munich, Germany. elevation procedures. Although bone grafting proce- 2 Private practice, Department of Oral and Maxillofacial Surgery, dures show high success rates, these augmentation Hospital East Limburg, Genk, Belgium. 3Clinical Associate Professor, Department of Restorative techniques usually require several months of healing Dentistry, Charité - Medical University Berlin, Germany; Private before implants can be inserted. As a consequence, Institute of Periodontology and Implantology, Munich, Germany. in these clinical situations, simultaneous implant placement is not possible. In addition, these patients Correspondence to: Dr Marc Hinze, Private Institute of Periodontology and Implantology (IPI), Richard-Strauss-Str. 69-71, are often of an advanced age and have medical con- 81677 Munich, Germany. Fax: +49-89-540425819. ditions that prevent repeated surgical interventions Email: [email protected] and time-consuming treatment protocols.

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© 2011 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY.. NO PART OF MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. Hinze et al

The introduction of the zygomatic implant made it • Patients had to be physically and psychologically possible for clinicians to perform immediate implant able to tolerate conventional surgical and restor- placement without bone augmentation for the treat- ative procedures. ment of such patients.1 To date, several reports have • Patients had to provide informed consent. described success with zygomatic implants support- ing fixed prosthetic reconstructions.2–7 Even imme- Exclusion criteria were as follows: diate provisionalization accompanied by immediate functional loading of zygomatic implants has shown • Any general contraindications for implant surgery promising results.8–11 • Any active infection or severe inflammation in the The survival of zygomatic implants is primarily based areas intended for implant placement on adequate bone support derived from the zygomatic • The presence of systemic diseases such as uncon- buttress. Because much of the implant is outside of trolled diabetes the bone tissue and only a short part of it is supported • Any treatment with therapeutic radiation to the by bone, mechanical and biologic stability would seem head within the previous 12 months to be limited. Clinically, therefore, it is necessary to • The presence of any previously unresorbed grafting splint the zygomatic implants with other implants in a material at the implant site rigid reconstruction as the loading protocol begins.4 • Severe parafunctional habits such as bruxing and To increase biomechanical stability over the long clenching term, the development of an extended implant site • Pregnancy at the time of the screening visit surrounding the entire zygomatic implant seems to be • Poor oral hygiene and/or motivation favorable. Therefore, a treatment method to provide a bony housing around the zygomatic implant simul- The nature of the study was explained to each pa- taneous with implant placement would be preferable. tient before he or she provided written informed con- The purpose of the following cohort study is to intro- sent. Randomization of patients/procedures was not duce a modified surgical technique for the placement feasible given the specific treatment protocol. of zygomatic implants that aims to minimize the risk of biologic complications. Presurgical Evaluation All patients underwent preoperative clinical and radiographic evaluation. To determine the residual bone MATERIALS AND METHODS volume and the desired prospective implant positions and lengths, a presurgical cone beam computed to- This case cohort study was performed in a private mography (CBCT) scan was obtained. Consequently, dental clinic in southern Germany (Private Institute of a three-dimensional evaluation of the maxilla and the Periodontology and Implantology). Patients over the sinus cavity was performed. The width, density, and age of 18 (of both sexes and any race) were recruited volume of the zygoma were determined to ensure that for maxillary reconstruction with an immediately loaded placement of a zygomatic implant was a feasible treat- full-arch prosthesis. All patients had extremely atro- ment approach (Figs 1 and 2). A provisional prosthe- phied maxillae and were planned to be treated with one sis was fabricated prior to surgery, in accordance with to four zygomatic implants (Nobel Biocare) in conjunc- a diagnostic setup. tion with sinus bone grafting. To support the fixed prosthesis with a minimum of four implants, conventional Surgical Procedure auxiliary tilted implants (NobelActive, Nobel Biocare) Implant surgery was performed with patients under were placed in the anterior maxilla, when necessary. general anesthesia. One hour prior to surgery, antibi- Other inclusion criteria were as follows: otic prophylaxis was administered as a single injection of clindamycin (600 mg), which was also prescribed • Patients had to be either edentulous in the max- postsurgically (300 mg orally administered three times illa or their remaining teeth had to be hopeless and daily for 7 days). Analgesics were prescribed postsur- planned for extraction. gically if needed for pain. Rinsing with 0.1% chlorhexi- • Atrophy of the maxilla had to be extreme enough to dine was performed for up to 2 weeks after surgery. have required posterior bone augmentation, were After extraction of any remaining hopeless teeth, a mu- it not for the placement of zygomatic and tilted im- coperiosteal flap was raised from the maxillary crest to plants. the zygomatic buttress (Fig 3). The suborbital nerve was • A decision had to have been previously made to identified and avoided to prevent paresthesia and other use dental implants for rehabilitation with a fixed neural injuries. Corresponding to the sinus floor elevation restoration. technique, a lateral sinus window at the facial aspect of

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Fig 1 (Left) CBCT scan of the desired implant site. Note the limited amount of bone below the sinus cavity.

Fig 2 (Right) Preoperative CBCT scan (coronal view) of the proposed zygomatic implant site.

Fig 3 Crestal incision, elevation of a mucoperiosteal flap, and Fig 4 An extended lateral window is prepared from the sinus visualization of the lateral antral wall. floor to the superolateral aspect of the maxilla.

Fig 5 Controlled reflection of the sinus membrane is accom- plished with sinus elevation instruments.

Fig 6 (Right) Schematic drawing of the extended sinus elevation technique. The sinus mucosa (white line) is reflected beyond the proposed zygomatic implant position (bar). The green area repre- sents the future implant site, ie, the augmented sinus cavity.

the maxilla was prepared with rotating burs. The future membrane were extended to the superolateral aspect entrance point of the zygomatic implant at the alveolar of the maxilla to the proposed implant site(s) in the crest (ie, the first molar region) served as a starting point zygomatic bone (Figs 6 and 7). This prolonged lateral in the mesiodistal direction. Special care was given to window was also helpful during surgery for determin- prevent perforation of the sinus membrane. After the ing the orientation of implants within the zygoma and lateral window was established, the sinus membrane the maxillary sinus. was precisely elevated toward the medial aspect of After the sinus membrane was elevated adequately, the maxillary antrum with sinus elevation instruments initial access into the zygomatic bone was obtained (Figs 4 and 5). To enable sinus bone grafting, the lat- with a round bur (Fig 8). Depending on the quantity eral window and the subsequent reflection of the sinus and quality of existing bone, the optimal positions for

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Fig 7 After extended elevation of the sinus mucosa beyond the Fig 8 The access point of the implant into the body of the zygoma future implant site, the integrity of the sinus membrane is confirmed can be viewed easily through the extended lateral window. Note visually. the direct visualization of the posterior antral wall.

Fig 9 Clinical view after preparation of an extended lateral win- Fig 10 The intrasinusal and lateral portions of the zygomatic dow, sinus membrane reflection, and zygomatic implant placement implant are augmented with bone graft material. in the right maxilla. the implants in the regions of the second premolar and The augmented area was covered with a resorb- the first molar were defined. The angulations of the im- able barrier membrane (Osteobiol SoftCorticalLami- plants were checked to confirm that the implants fit na, ADSystems) to prevent soft tissue ingrowth into within the provisional prosthesis. The exact position of the sinus and to enable guided bone regeneration. the tip of the implant in the zygomatic arch was marked Fixation pins (TitanPin, Geistlich) were used when with a round bur after the sinus window had been pre- collapse of the barrier membrane was expected (Fig pared. Next, different drills with increasing diameters 11). A second barrier membrane (Osteobiol Evolution, were used to prepare the sites for the insertion of one ADSystems) was applied on top of the first membrane to four zygomatic implants (Nobel Biocare) in each pa- to allow optimal soft tissue integration (Fig 12). tient. The precise implant lengths were determined by After implant placement and grafting, primary wound the use of a special depth gauge. With the objective closure was obtained. A pickup impression of the im- of immediate loading, definitive abutments were con- plants was made at the conclusion of surgery, and nected to the zygomatic implants (Fig 9). interocclusal registration was performed using a prefab- After the integrity of the sinus membrane was con- ricated provisional prosthesis. Within 4 hours, a screw- firmed, the established sinus cavity was augmented retained full-arch acrylic resin provisional prosthesis with a bone graft material (Osteobiol mp3, ADSys- was delivered to each patient (Fig 13). The prostheses tems) corresponding to a traditional sinus elevation were designed without cantilevers but with a minimum approach (Fig 10). The procedure was performed until of 10 teeth because of the favorable support provided the entire intrasinusal and lateral portions of the zygo- by the posterior zygomatic implants. Postoperatively, matic implant as well as the exposed threads at the the positions of the implants and the amount of bone implant neck had been augmented. augmentation were checked radiographically (Fig 14).

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Fig 11 Covering and stabilization of the augmented area are ac- Fig 12 A second barrier membrane is placed for optimal soft complished with a resorbable barrier membrane and fixation pins. tissue integration.

Fig 13 After primary flap closure and impression taking, a fixed Fig 14 Postoperative panoramic radiograph after implant place- screw-retained full-arch provisional prosthesis is seated. ment and augmentation of the implant site.

Definitive Prosthetic Procedure this was completed, the prosthesis was seated with Definitive reconstructions were delivered to all pa- a torque-control device and the screw access holes tients 6 months postsurgery (Fig 15). Complete full- were closed again. arch prostheses were supported by metal or zirconia frameworks combined with high-density acrylic resin. Follow-up Protocol Cantilevers were extended up to the first molar re- Clinical Examinations. At 6 months after surgery at gions to provide a greater occlusal surface area and the time of definitive prosthesis placement, the follow- improved functional capability. The definitive prosthe- ing clinical parameters were checked at the implant ses were fixed with titanium screws (Torqtite, Nobel level by an independent clinician. Biocare) at 20 Ncm with a torque-control device. • The stability of each implant was assessed by ap- Supportive Implant Therapy plying pressure with two opposing instruments af- All patients were given the opportunity to participate ter removal of the prostheses. in an implant recall program. The supportive care was • The presence of plaque at six sites per implant was performed on an individual basis at 3- or 6-month in- recorded as the percentage of total surfaces (FMPS). tervals. The hour of therapy included removal, clean- • Bleeding on probing (BOP) was measured dichot- ing, and polishing of the fixed prosthesis; examination omously at six sites per implant and was recorded and reevaluation of the implants; motivation and re- as the percentage of total surfaces (FMBS). instruction of the patient; and instrumentation of the • Pocket probing depth (PPD) was measured at six implants using primarily a low abrasive air polishing sites per zygomatic implant and recorded to the powder (Clinpro Prophypowder, 3M ESPE). When nearest millimeter.

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Fig 15 (Left) Clinical view of the definitive fixed reconstruction.

Fig 16 (Below) Linear radiographic bone gain was measured at three different reference levels (Z1, Z2, and Z3) on the buccal and palatal aspects of each zygomatic implant.

Z3 Z2

• The distance between the implant shoulder and the Survival and Complications. For the purposes of mucosal margin (DIM) in millimeters was measured this study, implant and prosthesis survival were de- at six sites per zygomatic implant. fined as the implant and/or prosthesis remaining in • The probing attachment level (PAL) in millimeters situ throughout the observation period, with or without was calculated by subtracting PPD from DIM. modification. All biologic complications were noted, • The height of the keratinized mucosa (KT) was mea- including postoperative bruising, infection, neuropa- sured at the buccal aspect of the zygomatic implants. thy/paresthesia, and/or recurrent and persistent peri- implant infection. Technical complications to be noted All clinical measurements were made by an inde- included fracture of the implants, screws, or abut- pendent examiner using a UNC-15 periodontal probe ments; screw or abutment loosening; framework or (Hu-Friedy), with readings recorded to the nearest veneer fractures; and loss of retention. millimeter. Radiographic Examination. Radiographic as- Data Analysis sessment was done with CBCT scans obtained im- Data were expressed as means ± standard deviations mediately after surgery and at the 6-month follow-up (SDs). The radiographic measurements at the 6-month visit (i-CAT, Imaging Sciences) (exposure time: 20 follow-up were compared to the values obtained imme- seconds; tube voltage: 120 kV; tube current: 3 to 8 diately after surgery by means of a paired t test (α = .05). mA). Measurements were made using a software program (OsiriX 3.9 Imaging Software, Pixmeo SARL) (level = 1,500, window = 5,000, zoom = 400%). RESULTS To perform reproducible measurements at different time points, a multiplanar reconstruction running Between January 2010 and November 2010, 10 through the implant apex, the implant head, and the patients (three men and seven women) were recon- center of the abutment was created for each zygomat- structed with immediately loaded complete full-arch ic implant at each time point. The implant access point prostheses, each supported by a minimum of four of the sinus floor (Z1), the calculated implant center implants. The mean age at surgery was 61.5 years (Z2) (implant length/2), and the implant entrance point (range, 56 to 69 years). Three of the included pa- within the zygomatic buttress (Z3) served as reference tients were smokers (two were light smokers of < 10 levels. Linear radiographic bone height—the distance cigarettes/day, and one was a heavy smoker of about between the implant surface and the external border 20 cigarettes/day). of the augmented area—was measured perpendicu- In all, 22 zygomatic implants and 23 anterior aux- lar to the implant axis within the created plane on the iliary implants were placed. Each patient received buccal and palatal aspects of each zygomatic implant zygomatic implants in conjunction with sinus bone (Fig 16). grafting, as described.

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Table 1 Summary of Patients Treated with Zygomatic Implants in Conjunction with Sinus Bone Grafting Lengths (mm) and locations* of zygomatic implants No. of Age auxiliary Patient no. Sex (y) Smoker? 16 14 24 26 implants Complications 1 M 58 Yes (< 10) 35 – – 40 3 2 F 68 No 30 – – 30 3 Occlusal screw loosening (16) 3 F 56 No – – – 30 3 4 F 68 No 35 – – 35 3 Fracture of acrylic resom veneer material (13) 5 M 59 No 45 – – 40 3 6 F 69 Yes (20) 40 – – 40 2 7 M 57 No 50 40 40 50 0 Removal of zygomatic implant (24) during surgery because implant was within the orbital fat compartment 8 F 58 Yes (< 10) – – – 40 3 Removal of zygomatic implant (26) because of continued pain after 6 months 9 F 62 No 40 50 45 35 0 10 F 60 No 35 – – 40 3 *FDI tooth-numbering system used.

Survival and Complications 3.7 ± 0.3 mm. DIM of 3.3 ± 0.4 mm and PAL of One zygomatic implant had to be removed immedi- 0.4 ± 0.3 mm on average were recorded. Mean KT ately after surgery, because the implant apex slightly height of 3.4 ± 0.2 mm was found. The 6-month out- perforated the orbital floor and was located within the come measures are displayed in Table 2. orbital fat compartment, as detected in the postoperative CBCT scan. A second zygomatic implant was Radiographic Observations removed surgically after 6 months as a consequence Linear measurements of the radiographic bone gain of persistent idiopathic pain in the cheekbone. Both are shown in Table 3. In all treated sites, the grafting implants were removed without compromising pros- material could be visualized as a radiopaque structure thetic function. No implants were lost as a con- in CBCT scans postsurgically and at the 6-month sequence of mobility. The overall 6-month implant evaluation. The differences in average radiographic survival rates were 90.9% for zygomatic implants and bone gain at reference level Z1 between baseline 100% for auxiliary implants. Extensive bruising was and 6 months were statistically significant P( < .0001 observed in two patients. No oroantral communica- and P = .0023, respectively). For reference level Z2, tions or infections of the sinus were observed within the differences between baseline and 6 months were the observation time. statistically significant P( = .0034 and P= .0022, re- None of the 10 fixed prostheses were lost during spectively). For Z3 as well, the differences between the observation period. The technical complications baseline and 6 months were statistically significant included fracture of the acrylic veneer material in one (P = .0018 and P = .0002, respectively). Figure 17 provisional prosthesis and occlusal screw loosening shows new radiographic bone formation around a zy- in one case. All the technical complications were con- gomatic implant after 6 months of healing. sidered minor and could be resolved without detach- ing the prostheses, resulting in an overall prosthetic survival rate of 100%. Main characteristics of each DISCUSSION patient are shown in Table 1. This clinical cohort study demonstrates the procedure, Six-month Clinical Outcomes the clinical outcomes, and the radiologic findings of a The 10 patients presented at the 6-month follow-up novel surgical approach to place zygomatic implants examination with mean FMPS and FMBS of 18.3% in conjunction with sinus bone grafting. The results ± 2.1% and 13.5% ± 2.1%, respectively. All implants preliminarily illustrate the potential benefits of this were clinically stable. The 6-month mean PPD was approach. In fact, a substantial gain of radiographic

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Table 2 Clinical Outcomes at the Table 3 Radiographic Bone Gain Immediately After Surgery 6-month Follow-up Examination and at the 6-month Follow-up Examination Variables Mean ± SD Bone height (mm) FMPS (%) 18.3 ± 2.1 Location Baseline 6 mo Difference P* FMBS (%) 13.5 ± 2.1 Z1 Buccal 2.5 ± 0.2 1.6 ± 0.1 0.9 ± 0.2 < .0001 PPD (mm) 3.7 ± 0.3 Palatal 5.0 ± 0.6 4.2 ± 0.5 0.8 ± 0.2 .0023 DIM (mm) 3.3 ± 0.4 Z2 Buccal 2.5 ± 0.4 1.4 ± 0.5 1.0 ± 0.3 .0034 PAL (mm) 0.4 ± 0.3 Palatal 6.5 ± 0.7 4.3 ± 0.4 2.2 ± 0.5 .0022 KT (mm) 3.4 ± 0.2 Z3 Buccal 3.0 ± 0.3 2.4 ± 0.3 0.5 ± 0.2 .0018 Palatal 3.9 ± 0.5 2.9 ± 0.4 0.9 ± 0.2 .0002 *Paired t test.

Fig 17 CBCT scan 6 months after implant placement according to the modified technique. Note the bony housing that has developed around the entire zygomatic implant. bone around the zygomatic implants (means of 1.4 ± sult in any profound complications in the antrum. With 0.5 mm to 4.3 ± 0.4 mm) was observed at 6 months, the sinuscope technique, Petruson16 assessed the re- accompanied by shallow PPDs (3.7 ± 0.3 mm) and action of the sinus membrane to zygomatic implants minimal attachment loss (PAL = 0.4 ± 0.3 mm). Dur- penetrating the sinus cavity. During the healing pro- ing the observation period, no oroantral communica- cess, the sinus mucosa covered the implants to some tions or infections of the sinus were observed. These extent, and no signs of infection around the implants outcomes were achieved using what the authors have were observed visually. Davo et al17 followed a co- termed the “extended sinus elevation technique.” hort receiving immediately loaded zygomatic implants In general, for the reconstruction of the extremely clinically and radiologically. The authors stated that atrophied maxilla, the zygomatic implant concept of- sinuses penetrated by zygomatic implants seemed fers a very positive benefit. Avoiding bone augmenta- to maintain a normal physiology. No clinical signs or tion procedures and graft maturation prior to implant symptoms of sinusitis could be found, despite the fact placement, which eliminates time-consuming and that in approximately 15% to 20% of patients, early repeated surgical interventions, is considered a ma- radiologic findings of infection were observed. jor benefit of the traditional approach to zygomatic Another possible explanation for the postoperative implant insertion. Additionally, shortening the treat- sinus infections frequently seen might be that oroan- ment through immediate functional loading of zygo- tral communications provoke a severe reaction of the matic implants is regarded as an improved treatment maxillary sinus mucosa. The mechanical and biologic modality, and not only for older patients with unfavor- stability of the zygomatic implant is almost exclusively able medical conditions. limited to the short portion that is incorporated into However, although zygomatic implant insertion has the cheekbone, whereas the crestal bone, with its been shown to have a number of advantages, the often thin sinus floor, displays the weakest point of conventional placement technique may have some implant-bone anchorage. Kahnberg and colleagues4 limitations. Existing clinical data have shown that reported that the thin palatal bone, the widening of the the placement of zygomatic implants increases the drill hole during the surgical procedure, and possible risk of postoperative complications related to the si- micromovement of the zygomatic implants after load- nus.4–7,12–14 Aparicio et al15 reported that sinusitis ing, may together influence sinus-related symptoms occurred in 2.3% to 13.6% of cases; thus the risk for and complications. Furthermore, the authors stated sinusitis should not be underestimated. that the limited maxillary bone volume may have had The fact that the zygomatic implant itself passes an impact and could not be excluded as a possible through the maxillary sinus cavity does not seem to re- cause of implant failure.

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Becktor et al14 observed a 9.7% implant failure rate sinus membrane in conjunction with sinus bone graft- because of recurrent sinusitis in spite of clinical stabil- ing seems to have a high potential to create a bony ity of the implants. They proposed that lack of osseoin- housing, even around zygomatic implants. tegration occurred at the marginal bone level, resulting To perform the proposed technique, the integrity of in transverse mobility of the zygomatic implant. The the sinus membrane must be maintained intrasurgically subsequent pump effect during function may have led, rather than penetrated during drilling. Therefore the via oroantral communications, to the sinus infections. “extended sinus elevation technique” is characterized Crestal bone level alterations, in conjunction with by an enhanced lateral window that is large enough increased PPDs, caused either by the positioning of to allow controlled elevation of the maxillary sinus the zygomatic implant head and abutment or by peri- membrane prior to zygomatic implant placement. To implant infections, may be another factor responsible precisely reflect the membrane beyond the intended for opening a passage between the oral cavity and implant site, it is of the utmost importance that the win- the maxillary sinus. Regarding peri-implant infections, dow of the lateral antral wall is extended to the supero- Al-Nawas and colleagues18 reported that, for 9 of 20 lateral aspect of the maxilla. According to Boyes-Varley implants, both BOP and PPD ≥ 5 mm were seen, re- et al,26 preparation of a buccal access window allows sulting in a success rate of only 55%. Where residual direct visualization of the access point of the implant crestal bone height is minimal, these intraoral soft tis- into the body of the zygoma, and perforation of the sue problems might have the potential to cause se- posterior antral wall can be avoided because of visual vere infections of the sinus and, when present, may control. Hence, the extended lateral window minimizes necessitate removal of the implant. the risk of operative complications and enhances in- Therefore, to reduce the complication rate, the trasurgical control. Furthermore, the visually controlled biomechanical stability of the entire zygomatic im- implant placement facilitates easier and more repro- plant should be increased. In contrast to traditional ducible implant positioning, enabling prosthetically zygomatic implant placement, the objectives of the ideal orientation of the implant platform. proposed “extended sinus elevation technique” are: (1) to preserve the integrity of the sinus membrane when placing the zygomatic implant and (2) to regen- CONCLUSION erate bone around the implant, thereby increasing the bone-to-implant contact, while the new implant site is The proposed “extended sinus elevation technique” created, comparable to a sinus elevation procedure. to place zygomatic implants in conjunction with si- With this technique, the advantages of the conven- nus bone grafting may decrease the risk of biologic tional zygomatic implant concept—namely, the imme- complications, in contrast with traditional zygomatic diate reconstruction of a severely atrophied maxilla implant placement, in the following aspects: and the benefits of a bone grafting procedure—are combined in a single step. It can be assumed that the • Maintenance of the integrity of the sinus membrane simultaneous implant site development, by creating may reduce sinus-related symptoms and complica- more bone volume and improving bone topography tions. along the entire zygomatic implant, enhances biome- • Exposed implant threads within the maxillary an- chanical stability and minimizes any crestal transverse trum are eliminated through the development of a mobility. Communications between the oral cavity and bony housing around the entire zygomatic implant the maxillary antrum can be avoided, while the surgi- by sinus bone grafting. Possible oroantral com- cal technique provides a stable bony housing around munications may be prevented by the grafting ap- the implant. In addition, exposed implant threads with- proach when little crestal bone remains or initial or in the antrum, which may contribute to sinus-related late marginal bone loss occurs. complications, are eliminated a priori. • Biomechanical properties may be improved by in- The traditional sinus elevation procedure is a pre- creased bone-to-implant contact as a new implant dictable treatment method to augment the posterior site is developed. maxilla and has been associated with high implant survival rates and a low incidence of surgical complications.19–21 The success of sinus bone grafting is at- tributable to the high osteogenic potential of the sinus ACKNOWLEDGMENTS membrane. Clinical studies have shown that elevation of the membrane, with or without placement of a This study was not supported by any company. The authors would grafting material, results in bone gain above the sinus like to thank Ole Jensen (Denver, Colorado) for reviewing the manuscript. floor.22–25 Therefore, maintenance of the integrity of the

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