Bone-Added Osteotome Sinus Floor Elevation for the Deficient Maxillary Posterior Implant Site: Case Series

Shilpa Kolhatkar, DDS, MDS;¹ Leyvee Cabanilla, DDS, MSD;² and Monish Bhola, DDS, MSD³

The advent of implants has revolutionized treatment options for patients who desire replacement of missing teeth. Implant therapy can be employed successfully in most clinical situations; however, reduced bone dimension can present a significant challenge. This is especially true in the maxillary posterior region where, following tooth extraction, sinus pneumatization caused by an increase in osteoclastic activity of the periosteum¹ often results in inadequate vertical bone height. In addition, this region has other complicating factors, such as undercuts² and poor bone quality.^3-5

Reports of the successful use of shorter implants to avoid encroachment of pneumatized sinuses are available.^6,7 However, an analysis of longitudinal studies, which included 16,344 implants, demonstrated that along with other risk factors, poor bone quality in connection with short implants seemed to be associated with failure.⁸ Other reports also have shown implants shorter than 10 mm are less successful than longer implants.^3,9-12 Recently, tilted implants also have been suggested as an alternative, although long-term data regarding their success are still limited.^13-15 There is a paucity of data comparing short implants with long implants in grafted sinuses. Thus, sinus floor elevation (SFE) techniques, which allow placement of longer implants in an ideal axial orientation, continue to be an important part of the implant surgeon's repertoire.

Augmentation of the atrophic maxillary ridge can be accomplished by many techniques such as SFE via a lateral window approach,¹⁶ SFE through a crestal approach^7,18 onlay grafting,^19,20 guided bone regeneration,^21,22 appositional bone graft/saddle-graft,²³ or a combination of one or more procedures.²⁴ Boyne and James¹⁶ published the first report on the lateral window SFE technique, although Tatum had presented this concept in 1977.²⁵ Long-term success of this technique is well-established;^26-28 however, a high incidence of intraoperative complications also has been reported.²⁹ Attempts were continually made to find a less invasive approach. The sinus floor elevation technique using a crestal approach was suggested by Tatum in which the sinus floor was fractured, followed by membrane elevation using "socket formers."¹⁷ Summers¹⁸ utilized a crestal approach with use of specific root analog instruments (osteotomes). This technique, called the osteotome sinus floor elevation (OSFE), was described as a conservative alternative to the more traditional lateral window approach. Many authors have reported on advantages of this approach, citing reduced morbidity³⁰ and postoperative discomfort³¹ as well as shortened surgical time.³²

The OSFE technique, as described by Summers,¹⁸ attempted to gain vertical bone height by retaining and relocating all the existing bone. In soft bone (D4-fine trabecular bone),³³ the use of tapered osteotomes with concave tips allowed preparation of the osteotomy without drilling. In D3 bone (thin porous cortical bone on crest and fine trabecular bone within), minimal drilling for ostoetomy preparation may be required. When the osteotome was pushed toward the sinus floor, bone shavings from the lateral walls of the osteotomy were collected in the concave part of the osteotome. This bone mass was pushed upward without intrusion of the osteotome into the sinus cavity. Thus, the sinus floor and membrane were elevated with minimal risk.

Summers³⁴ further modified the OSFE technique by adding bone graft into the osteotomy prior to sinus elevation. This was referred to as the bone-added osteotome sinus floor elevation (BAOSFE) technique. The plug of bone graft was believed to act as a cushion during sinus floor elevation, thus reducing the risk of membrane perforation. He recommended a combination of autogenous bone harvested from the adjacent area mixed with an equal quantity of human demineralized freeze-dried bone (DFDB). Resorbable hydroxyapatite (less than 20% by volume) was added to increase visibility of the graft radiographically.

Using the BAOSFE technique, consistent sinus membrane elevation of 4 mm to 5 mm was described by Summers.³⁴ Other reports have demonstrated a wide variation in the amount of sinus elevation that could be predictably achieved. Fugazotto reported a range of 1 mm to 7 mm of vertical bone gain with a mean of 3.5 mm,³⁵ which is similar to an earlier report.³⁶ In a cadaver study, Reiser et al found predictable sinus floor elevation of 4 mm to 5 mm and up to 6 mm to 8 mm when a 2-mm twist drill was used for osteotomy preparation, ending within 1 mm of the sinus floor.³⁷ Visualization of membrane integrity using an endoscope during the BAOSFE procedure has been recommended by Nkenke et al,³⁸ especially when anticipated sinus elevation is greater than 3 mm. Baumann and Ewers³⁹ reported an impressive bone gain of 13 mm when sinus floor elevation was performed under endoscopic control.

The following grafting materials have been employed for the BAOSFE technique: demineralized freeze-dried bone powder; porous hydroxyapatite; deproteinized bovine bone granules;⁴⁰ freeze-dried bone allograft and autogenous bone;³² anorganic bovine bone;⁴¹ autogenous bone; and collagen sponge.⁴² A meta-analysis of survival of implants placed in grafted maxillary sinuses after functional loading for 18 months or more was performed by Tong et al.²⁶ They reported a survival rate of 90% when only autogenous bone was used, 94% for a combination of hydroxyapatite and autogenous bone, 98% for a combination of DFDBA and hydroxyapatite, and 87% with hydroxyapatite only. This meta-analysis suggests similar implant survival rates for the different grafting materials. A more recent systematic review by Del Fabbro⁴³ reported the following implant survival rates: 87.7% for 100% autogenous bone, 94.88% for autogenous bone with various bone substitutes, and 95.98% for bone substitutes alone. In the second clinical case described in this case series, the patient desired the removal of buccal exostoses. Because implant survival is similar when autogenous bone mixed with bone substitutes is used or when bone substitutes alone are employed,^26,43 the bone particles harvested from the exostoses in the second case were utilized with DFDBA.

Treatment Planning and Technique

Residual bone height (RBH) measurement is a key determinant when choosing the most appropriate approach for sinus elevation.

The Sinus Consensus Conference of 1996²⁷ made several recommendations for the surgical protocol for implant placement. RBH was divided into four categories:

1. Class A, > 10 mm, for which the classic implant protocol could be followed.

2. Class B, 7 mm to 9 mm, for which a BAOSFE could be performed with simultaneous implant placement.

3. Class C, 4 mm to 6 mm, which would require a lateral approach with delayed or immediate implant placement.

4. Class D. When there is only 1 mm to 3 mm of bone, a lateral approach with delayed implant placement is recommended.

Summers³⁴ suggested that the BAOSFE technique should be considered for patients with RBH of 5 mm or more. Some have suggested preoperative RBH from 8 mm to 10 mm²⁷; others have recommend 4 mm.⁴⁴ There is a lack of conclusive evidence relating preoperative RBH to implant survival. However, Rosen et al⁴¹ demonstrated implant success was reduced to 85.7% for implants placed in preoperative RBH of 3 mm to 4 mm compared to 96% for implants put in preoperative bone of > 5 mm.

To accurately assess the height of available bone, a thorough pretreatment clinical and radiographic evaluation must be completed. Although conventional periapical and panoramic radiographs have been used effectively, the advent of advanced imaging techniques, such as cone-beam computed tomography (CBCT), has significantly enhanced the accuracy of bone volume measurements.

When the amount of available bone has been determined, a crestal incision placed slightly toward the palatal aspect of the edentulous area is made. A full-thickness flap is elevated to access the alveolar crest. The crestal approach for the osteotomy is initiated by marking the site with a small round bur, followed by a 2-mm twist drill. The osteotomy is prepared 1 mm short of the sinus floor and verified radiographically with a depth indicator in place. Then, the osteotomy is widened to the final twist drill (Figure 1). In D4 bone, the final enlargement of the osteotomy is accomplished using an osteotome, which expands the lateral osteotomy walls. After radiographic confirmation, a sterile amalgam carrier is used to place the bone graft into the osteotomy (Figure 2). An appropriately sized osteotome is selected and advanced slowly, using gentle mallet strokes until abfracture is achieved. Subsequently, this step is repeated several times until the desired height is attained. An estimated 1-mm sinus floor elevation is anticipated for each load of bone graft occupying 3 mm of the osteotomy space. The sinus floor is elevated entirely by the bone graft without the osteotome encroaching into the confines of the maxillary sinus cavity. This can be ensured by placing a stopper on the osteotome at the established preoperative bone height (Figure 3). The patient should be instructed to perform the Valsalva maneuver multiple times during the procedure to ensure membrane integrity. The final step of the sinus elevation is performed by the implant, and the flap sutured without tension. Membrane perforation during the BAOSFE technique can be minimized using sound clinical planning and accurate determination of available preoperative bone height. Research has found that implants can heal uneventfully if a small perforation without graft dispersion occurs.⁴⁵

Case Reports

Case 1: Bilateral BAOSFE with DFDBA for Implant Placement in the First Molar Region

A 49-year-old woman presented for implant consultation for replacement of maxillary molars. Her medical history was unremarkable. The patient reported a smoking history of 30-pack years but had quit 6 months ago. She was taking levothyroxine and using a nicotine patch. After thorough discussion of various treatment options, the patient opted for replacement of only first molars. Radiographic measurement using periapical, panoramic and CBCT images revealed bone height of approximately 5 mm at implant site No. 3 (Figure 4) and 9 mm at No. 14 (Figure 5). Surgery for implant No. 14 was done in December 2007 and No. 3 was 8 weeks later. The surgical procedure was similar for both sides.

Upon administration of local anesthetic, a crestal incision was made, followed by full-thickness flap elevation. Using a 2.2-mm twist drill, osteotomy for both sites was prepared to a depth 1 mm short of the sinus floor and then widened up to 3.5 mm. Approximately 5 mm to 6 mm of sinus floor elevation was achieved using DynaGraft D^TM Paste demineralized bone matrix (Keystone Dental, Inc, www.keystonedental.com). Implants measuring 4.1 mm x 10 mm (SLActive Straumann^®, Straumann USA LLC, www.straumann.us) were placed on No. 3 (Figure 6) and No. 14 (Figure 7). Postoperative medications included acetaminophen 800 mg q 8 hours prn, 300 mg acetaminophen with 30 mg codeine, amoxicillin 500 mg tid for 7 days. The patient was also asked to take Zyrtec-D^® (McNEIL-PPC, Inc, www.zyrtec.com) every 12 hours for 4 weeks starting 2 weeks before the surgical appointment. She was seen for regular follow-ups, and no complications were observed. Final restoration was placed after a 6-month healing period. The patient was functioning comfortably 1 year after sinus elevation procedure (Figure 8 and Figure 9). Radiographs taken at this visit revealed maturation of augmented bone.

Case 2: The 5-Year Follow-Up of Bilateral BAOSFE Performed with Autogenous Bone and DFDBA

A 64-year-old woman desired replacement of missing maxillary premolars and molars. She did not smoke and had no significant medical problems, yet she had seasonal allergies. Intraorally, the patient presented with multiple exostoses on the right (Figure 10 ) and left sides (Figure 11). A thorough evaluation of implant sites during the clinical examination and radiographic interpretation was performed. Periapical (Figure 12) panoramic films with radiographic markers were taken (Figure 13), and the patient was informed of the need for sinus elevation at sites Nos. 3 and 14. She agreed to use bone harvested from the exostosis with DFDBA for this purpose. The surgical procedures were performed 3 weeks apart in June 2003.

For the maxillary right quadrant, an incision extending from No. 8 to No. 2 allowed reflection of a full-thickness flap with complete visibility and access to the lateral surface of the maxilla. Osteotomy for No. 4 was prepared to 13 mm but only to 7 mm for No. 3, using 2-mm and 2.8-mm twist drills. The exostoses were harvested using a chisel (Figure 14), and the harvested bone was ground to make smaller size particles using a bone mill and mixed with a diameter of 420-μm to 850-μm with DFDBA particles. This bone mix was used for sinus floor elevation, using a 2.8-mm angled osteotome (Figure 15 ). Implants measuring 3.75 mm x 13 mm (Branemark System TiUnite, Nobel BioCare, www.nobelbiocare.com) were placed in Nos. 3 and 4 area. Flaps were sutured with 4-0 VICRYL polyglactin 910 suture (Ethicon, www.ethicon.com), and tension-free closure was ensured. The patient was given written and verbal postoperative instructions with a prescription: 500 mg Augmentin^® (GlaxoSmithKline, www.gsk.com) every 12 hours for 10 days, ibuprofen 800 mg every 8 hours as needed, and Zyrtec-D^® (McNEIL-PPC, Inc) every 12 hours. The patient was asked to gently rinse with 0.12% chlorhexidine gluconate rinse, twice daily for 2 weeks.

Three weeks later a similar procedure was performed on the left maxillary arch with placement of three implants in the area of teeth Nos. 12 to 14. Autogenous bone harvested from the adjacent area was milled and mixed with bioactive glass particles (Biogran^®, BIOMET 3i, www.biomet3i.com). Sinus elevation was required for only one site (No. 14), which received a 5-mm x 13-mm fixture (Brànemark System TiUnite), while a 4-mm x 13-mm fixture (Brànemark System TiUnite) was placed in No. 13, and a 4-mm x 15-mm fixture (Br ànemark System TiUnite) was placed in site No. 12.

A second-stage procedure was performed for both sites in October 2003, and the implants were restored 8 weeks later (Figure 16 and Figure 17). The patient has been seen for regular checks, and after 5 years, the implants continue to function satisfactorily. Radiographs taken at 5 years demonstrate stable crestal bone levels with absence of any pathology (Figure 18).

Case 3: Ridge Preservation with Simultaneous BAOSFE

A 66-year-old woman presented for implant evaluation to replace nonrestorable tooth No. 13 (Figure 19). She had knee replacement 2 years prior and a 15-pack year history of smoking but quit 2 years previously. She had hypertension, high cholesterol, and arthritis for which she was taking Lipitor^® (Pfizer, www.pfizer.com), propoxyphene, triamterene and hydrochlorpthiazide, and nifedipine. Other medications included pantoprazole and clarithromycin. Periapical radiograph of No. 13 (Figure 20) showed close proximity of the maxillary sinus to the apex. The patient was informed of the need for sinus elevation. The treatment plan included osteotome sinus elevation with simultaneous immediate implant placement. She was premedicated with Claritin^® (Schering-Plough, www.merck.com) and clindamycin 150 mg qid. After local anesthesia, a full-thickness flap was elevated from teeth Nos. 11 to 14. Periotomes, straight elevators, and forceps were used to atraumatically extract No. 13 (Figure 21), and no loss of buccal plate was observed (Figure 22). Because minimal bone was between the apex and the sinus floor, a 2.8-mm twist drill was used to widen only the apical portion of the socket. Particulate bovine bone (Bio-Oss^®, Osteohealth, www.osteohealth.com) was placed into the osteotomy and a 2.8-mm osteotome was used to achieve sinus floor abfraction (Figure 23). After adequate elevation, placement of a 3.3-mm x 12-mm implant Straumann^® (Straumann USA) was attempted. However, because of insufficient primary stability, a decision was made to delay implant placement and perform ridge preservation using DFDBA particles (Figure 24). The coronal portion of the socket was sealed, using calcium sulfate (Capset^®, Lifecore Biomedical, www.lifecore.com). Flaps were sutured using 4-0 VICRYL polyglactin 910 suture, and the patient was prescribed 300 mg acetaminophen with 30 mg codeine every 8 hours as needed. At the 1-, 2-, and 4-week postoperative visits, uneventful healing was observed. The patient was reappointed for implant placement approximately 6 months after the ridge preservation procedure. In May 2006, a 3.3-mm x 12-mm Standard Plus Implant (Straumann USA) was placed. A radiograph taken revealed significant gain in vertical dimension in the No. 13 area, with maturation and increased radio-opacity of the sinus graft (Figure 25). The implant was restored in January 2007. When the patient was evaluated for an 8-month follow-up visit (Figure 26), she reported no concerns with the restored implant.

Conclusion

Sinus floor elevation using the BOASFE technique is a minimally invasive procedure that is highly predictable for increasing the amount of available bone in the deficient maxillary implant site. This technique can be used when sinus topography necessitates sinus floor elevation for single- or multiple-implant placement.

Disclosure

Dr. Bhola is a current consultant for Keystone Dental and has received honoraria from Keystone Dental, Straumann, and Zimmer Dental.

About the Authors

Shilpa Kolhatkar, DDS, MDS¹
Clinical Assistant Professor,
Department of Periodontology and Dental Hygiene,
University of Detroit Mercy School of Dentistry,
Detroit, Michigan
Diplomate, American Board of Periodontology;
Private Practice,
Troy, Michigan

Leyvee Cabanilla, DDS, MSD²
Assistant Professor, Department of Periodontology and Dental Hygiene,
University of Detroit Mercy School of Dentistry;
Detroit, Michigan; Diplomate, American Board of Periodontology;
Private Practice,
Trenton, Michigan

Monish Bhola, DDS, MSD³
Associate Professor, Department of Periodontology and Dental Hygiene;
University of Detroit Mercy School of Dentistry,
Detroit, Michigan;
Diplomate, American Board of Periodontology;
Private Practice,
Waterford, Michigan

References

1. Misch C. Contemporary Implant Dentistry. 2nd ed. St. Louis, MO: Mosby;1999:469-495.

2. Bahat O. Treatment planning and placement of implants in the posterior maxillae: report of 732 consecutive Nobelpharma implants. Int J Oral Maxillofac Implants. 1993;8(2):151-161.

3. Sennerby L, Roos J. Surgical determinants of clinical success of osseointegrated oral implants: a review of the literature. Int J Prosthodont. 1998;11(5):408-420.

4. Esposito M, Hirsh JM, Lekholm U, et al. Biological factors contributing to failures of osseointegrated oral implants. (II). Etiopathogenesis. Eur J Oral Sci. 1998;106(3):721-764.

5. Bryant SR. The effects of age, jaw site, and bone condition on oral implant outcomes. Int J Prosthodont. 1998;11(5):470-490.

6. Renouard F, Nisand D. Short implants in the severely resorbed maxilla: a 2-year retrospective clinical study. Clin Implant Dent Relat Res. 2005;7(suppl 1):S104-110.

7. Fugazzotto PA. Shorter implants in clinical practice: rationale and treatment results. Int J Oral Maxillofac Implants. 2008;23(3):487-496.

8. das Neves FD, Fones D, Bernardes SR, et al. Short implants— an analysis of longitudinal studies. Int J Oral Maxillofac Implants. 2006;21(1):86-93.

9. Beschnidt SM, Muche R, Krausse A, et al. Implant survival and success rates in partially edentulous patients—Part I. Schweiz Monatsschr Zahnmed. 2003;113(4):396-403.

10. Buser D, Mericske-Stern R, Bernard JP, et al. Long-term evaluation of non-submerged ITI implants. Part 1: 8-year life table analysis of a prospective multi-center study with 2359 implants. Clin Oral Implants Res. 1997;8(3):161-172.

11. Guttenberg SA. Longitudinal report on hydroxyapatite-coated implants and advanced surgical techniques in a private practice.Compend Suppl.1993;15:S549-S553.

12. Jemt T, Lekholm U. Implant treatment in edentulous maxillae: a 5-year follow-up report on patients with different degrees of jaw resorption. Int J Oral Maxillofac Implants. 1995;10(3):303-311.

13. Krekmanov L, Kahn M, Rangert B, et al. Tilting of posterior mandibular and maxillary implants for improved prosthesis support. Int J Oral Maxillofac Implants. 2000;15(3):405-414.

14. Aparicio C, Perales P, Rangert B. Tilted implants as an alternative to maxillary sinus grafting: a clinical, radiologic, and periotest study. Clin Implant Dent Relat Res. 2001;3(1):39-49.

15. Testori T, Del Fabbro M, Capelli M, et al. Immediate occlusal loading and tilted implants for the rehabilitation of the atrophic edentulous maxilla: 1-year interim results of a multicenter prospective study. Clin Oral Implants Res. 2008;19(3):227-232.

16. Boyne PJ, James RA. Grafting of the maxillary sinus floor with autogenous marrow and bone.J Oral Surg. 1980;38(8):613-616.

17. Tatum H Jr. Maxillary and sinus implant reconstructions. Dent Clin North Am. 1986;30(2):207-229.

18. Summers RB. A new concept inmaxillary implant surgery: the osteotome technique. Compend Contin Educ Dent. 1994;15(2):152-162.

19. Smiler DG. Surgical solutions to prosthetic problems. J Dent Symp. 1993;1:44-49.

20. Jensen J, Sindet-Pedersen S. Autogenous mandibular bone grafts and osseointegrated implants for reconstruction of the severely atrophied maxilla: a preliminary report. J Oral Maxillofac Surg. 1991;49(12):1277-1287.

21. Buser D, Dula K, Belser U, et al. Localized ridge augmentation using guided bone regeneration. 1. Surgical procedure in the maxilla. Int J Periodontics Restorative Dent. 1993;13(1):29-45.

22. Artzi Z. Coronal ridge augmentation in the absence of bilateral bony plates around a pathologically denuded implant surface. Int J Periodontics Restorative Dent. 2000;20(2):191-197.

23. Bahat O, Fontanessi RV. Efficacy of implant placement after bone grafting for three-dimensional reconstruction of the posterior jaw. Int J Periodontics Restorative Dent. 2001;21(3):220-331.

24. McFadden DD. Pre-prosthetic surgery options for fixed dental implant reconstruction of the atrophic maxilla. Ann R Australas Coll Dent Surg. 2000;15:61-64.

25. Smiler DG, Johnson PW, Lozada JL, et al. Sinus lift grafts and endosseous implants. Treatment of the atrophic posterior maxilla. Dent Clin North Am. 1992;36(1):151-186.

26. Tong DC, Rioux K, Dragsholt M, et al. A review of survival rates for implants placed in grafted maxillary sinuses using meta-analysis.Int J Oral Maxillofac Implants. 1998;13(2):175-182.

27. Jensen OT, Shulman LB, Block MS, et al. Report of the Sinus Consensus Conference of 1996. Int J Oral Maxillofac Implants. 1998;13(suppl):11-45.

28. Wallace SS, Froum SJ. Effect of maxillary sinus augmentation on the survival or endosseous dental implants. A systematic review. Ann Periodontol. 2003;8(1):328-343.

29. Schwartz-Arad D, Herzberg R, Dolev E. The prevalence of surgical complications of the sinus graft procedure and their impact on implant survival. J Periodontol. 2004;75(4):511-516.

30. Davarpanah M, Martinez H, Tecucianu JF, et al. The modified osteotome technique. Int J Periodontics Restorative Dent. 2001;21(6):599-607.

31. Zitzmann NU, Schärer P. Sinus elevation procedures in the resorbed posterior maxilla. Comparison of the crestal and lateral approaches. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1998;85(1):8-17.

32. Coatoam GW, Krieger JT. A four-year study examining the results of indirect sinus augmentation procedures. J Oral Implantol. 1997;23(3):117-127.

33. Scortecci GM, Misch CE, Benner, KU, eds. Implants and Restorative Dentistry. London, England: Martin Dunitz Ltd; 2001:79-86.

34. Summers RB. The osteotome technique: Part 3—Less invasive methods of elevating the sinus floor. Compend Contin Educ Dent. 1994;15(6):698-704.

35. Fugazzotto PA. Augmentation of the posterior maxilla: a proposed hierarchy of treatment selection. J Periodontol. 2003;74(11):1682-1691.

36. Komarnyckyj OG, London RM. Osteotome single-stage dental implant placement with and without sinus elevation: a clinical report. Int J Oral Maxillofac Implants. 1998;13(6):799-804

37. Reiser GM, Rabinovitz Z, Bruno J, et al. Evaluation of maxillary sinus membrane response following elevation with the crestal osteotome technique in human cadavers. Int J Oral Maxillofac Implants. 2001;16(6):833-840.

38. Nkenke E, Schlegel A, Schultze-Mosgau S, et al. The endoscopically controlled osteotome sinus floor elevation: a preliminary prospective study. Int J Oral Maxillofac Implants. 2002;17(4):557-566.

39. Baumann A, Ewers R. Minimally invasive sinus lift. Limits and possibilities in the atrophic maxilla. Mund Kiefer Gesichtschir. 1999;3(suppl 1):S70-S73.

40. Karabuda C, Ozdemir O, Tosun T, et al. Histological and clinical evaluation of 3 different grafting materials for sinus lifting procedure based on 8 cases. J Periodontol. 2001;72(10):1436-1442.

41. Deporter D, Todescan R, Caudry S. Simplifying management of the posterior maxilla using short, porous-surfaced dental implants and simultaneous indirect sinus elevation. Int J Periodontics Restorative Dent. 2000;20(5):476-485.

42. Cavicchia F, Bravi F, Petrelli G. Localized augmentation of the maxillary sinus floor through a coronal approach for the placement of implants. Int J Periodontics Restorative Dent. 2001;21(5):475-485.

43. Del Fabbro M, Testori T, Francetti L, et al. Systematic review of survival rates for implants placed in the grafted maxillary sinus. Int J Periodontics Restorative Dent. 2004;24(6):565-577.

44. Rosen PS, Summers R, Mellado JR, et al. The bone-added osteotome sinus floor elevation technique: multicenter retrospective report of consecutively treated patients. Int J Oral Maxillofac Implants. 1999;14(6):853-858.

45. Berengo M, Sivolella S, Majzoub Z, et al. Endoscopic evaluation of the bone-added osteotome sinus floor elevation procedure. Int J Oral Maxillofac Surg. 2004;33(2):189-194.