Recent Trends in Sinus Lift Surgery and Their Clinical Implications Mahmoud Al-Dajani, DDS, MSc, PhD (OMFS), MSc, FRCD(C) (DPH)
ABSTRACT Background: Sinus lift procedures are used to allow residual bone to accommodate functional implants in atrophic posterior maxilla. Numerous anatomical and surgical advancements in sinus lift surgery are still inspiring clinicians. Purpose: The purpose of this study was to describe the recent trends in sinus lift surgery focusing on implant survival, bone grafting, anatomical and surgical considerations, and their clinical implications on the practice of implant dentistry in atrophic posterior maxilla. Materials and Methods: We performed an extensive search in MEDLINE, Embase, Scopus, Web of Science, Trip, Cochrane Oral Health Group’s Trials Register, Cochrane Central Register of Controlled Trials, and ProQuest Dissertations & Theses. Articles were critically reviewed to determine the level of evidence as per the Canadian Task Force on Preventive Health Care. Results: Comprehensive assessment of sinus septa, sinus pathology, and bone quality and quantity using three-dimensional cone beam computed tomography radiographs is important before placing implants in posterior maxilla. With a residual bone height of less than 5 mm, the survival rate of implant decreases substantially. Lateral window approach can increase the vertical bone height to greater than 9 mm, while osteotome approach can increase this height from 3 to 9 mm. The perforation of Schneiderian membrane doubles the risk for the incidence of sinusitis or infection. The use of piezoelectric surgery allows adequate sinus lift while protecting soft tissues and minimizing patient discomfort. Conclusions: Although both osteotome and lateral window procedures can help clinicians in overcoming the challenges of placing implants in atrophic posterior maxilla, pre-implant residual bone height is crucial in determining the survival of these implants. Future research directions should consider study designs grounded on longitudinal randomized controlled trials of large sample size. KEY WORDS: dental implants, lateral window, osteotome intracrestal, sinus augmentation, sinus elevation, sinus lift
INTRODUCTION
the floor of maxillary sinus in an upward direction, creating an appropriate bone height that can accommodate appropriately the placement of functional dental implants. Sinus lift surgery is usually followed by bone grafting in order to fill the compartment created between the osseous floor of the maxillary sinus and the Schneiderian membrane. Recent anatomical and surgical advancements in the understanding and conduct of sinus lift surgery are numerous. These advancements remain the main sources of inspiration that help clinicians to innovate, develop, and maintain a high standard of implant practice outcomes and expectations as well as patient satisfaction. In this article, we will review the literature for the recent scientific trends in sinus lift surgery focusing on implant survival, bone grafting, anatomical and surgical considerations, and their clinical implications on the practice of implant dentistry in atrophic posterior maxilla.
Atrophic posterior maxilla is a challenging anatomical area for the placement of dental implants. Whenever the diagnosis reveals insufficient residual bone height in posterior maxilla, sinus lift procedure (or residual bone augmentation) is indicated. Sinus lift procedure is a surgical intervention aimed at increasing the height of residual bone in the posterior maxilla by repositioning Researcher and instructor, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada Corresponding Author: Dr. Mahmoud Al-Dajani, Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, ON M5G 1G6, Canada; e-mail: [email protected] Conflict of Interest: No potential conflict of interest relevant to this article was reported. © 2014 Wiley Periodicals, Inc. DOI 10.1111/cid.12275
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MATERIALS AND METHODS We performed an extensive search of the literature to identify articles published between 1975 and 2014 dealing with patients managed with pre-implant sinus lift procedure through different surgical approaches. An electronic search was conducted in MEDLINE, Embase, Scopus, Web of Science, Trip, Cochrane Oral Health Group’s Trials Register, Cochrane Central Register of Controlled Trials, and ProQuest Dissertations & Theses. The bibliographies of review articles were also checked. The last electronic search was performed on April 4, 2014, entering the following terms: “dental implant” AND (“sinus augmentation” OR “sinus lift”). Literature was also identified through reference lists of selected articles. Only articles in English were included. Articles were critically reviewed to determine the level of evidence as per the Canadian Task Force on Preventive Health Care. Table 1 shows the key words and their combinations used in the literature search. Thirty-seven articles were included in the review tables, and distributed as follows: 7 retrospective studies, 20 prospective cohort/case series, 4 randomized controlled trials, and 6 systematic reviews with/without meta-analyses. Posterior Maxilla: Anatomical Considerations Limitations for placing an implant in the posterior maxilla are related not only to the residual bone height and width but also to the quality of maxillary bone. Poor bone quantity and quality in posterior maxilla are usually blamed for the decreased primary implant
TABLE 1 Literature Computerized Search Strategy Step
1 2 3 4 5 6 7 8 9
Keywords, search history, and criteria
Number of articles
“dental implant” “sinus augmentation” OR “sinus lift” (1 AND 2) Search limited to humans Search limited to English-language articles Relevant articles at title stage Relevant articles at abstract stage Relevant articles at full copy stage Adding three articles from reference lists of selected articles Articles included in review tables
7,153 1,691 209 184 169 35 35 35 37 37
stability and increased failure rates.1 Several factors enhance the loss of posterior maxillary residual bone after tooth extraction including: long-term tooth loss, trauma, infection, and advanced periodontal disease. Bone loss problem is further complicated with the associated downward movement of the sinus floor.1 This movement could be explained by the post-extraction change in intra-sinus equilibrium associated with increased activity of osteoclasts in the Schneiderian membrane, which fosters the maxillary sinus pneumatization phenomena. The decreased bone density and increased cortical plate porosity in posterior maxilla are additional characteristics that emphasize the need for assessing bone quality as well as quantity before placing implants in posterior maxilla.1 This thorough assessment is essential in planning the future place of dental implants in posterior maxilla, and can be accomplished by the use of three-dimensional cone beam computed tomography (CBCT) radiographs.2 Beside bone characteristics of posterior maxilla, two anatomical structures can importantly interfere with or even complicate bone grafting in sinus lift surgery: maxillary sinus septa and posterior superior alveolar artery (PSAA). Maxillary sinus septa are usually encountered in one out of four sinuses exhibiting a great degree of morphological and structural variability: complete versus partial; single versus multiple; unilateral versus bilateral; and transverse, sagittal versus horizontal.3 CBCT radiography remains the most accurate tool to diagnose and identify these septa in maxillary sinus.3 PSAA is the second important anatomical structure that implantologists need to respect in order to avoid the incidence of severe bleeding during the lateral window sinus lift surgery. PSAA enters the maxillary sinus through the posterior superior alveolar foramen at the posterior wall of maxilla. The intra-osseous branch of PSAA invaginates on the buccal (lateral) wall of sinus following either a straight or U-shaped course,4 and running at an approximate height of 19 mm away from the alveolar bone ridge.5,6 This height is usually shortest in the first molar area.4 We need to keep in our mind that the distance between the intra-osseous branch of PSAA and alveolar bone ridge decreases significantly in edentulous areas over time. The normal anatomy of Schneiderian membrane is structurally affected by the presence of potent
Recent Trends in Sinus Lift Surgery
pathology, which reflects negatively on the outcomes of sinus lift surgery.7 For example, preoperative chronic sinusitis can produce pathological and pathophysiological changes in Schneiderian membrane, hindering the normal ability of injured Schneiderian membrane to recover after surgery, and consequently increasing the risk for complications, bone graft loss, and even implant failure.7,8 Therefore, implantologists should pay special attention to evaluate the anatomical and physiological status of maxillary sinus to ensure the readiness of Schneiderian membrane for sinus lift surgery. The controversy surrounding the minimal necessary distance between the tip of implants and the floor of maxillary sinus has drawn continuous debate. Although there is no clear evidence that implants with tips placed within or with less than 1 mm away from the sinus floor level would fail, the preference among clinicians is to leave 1 to 2 mm of bone before the radiographically estimated sinus floor level. Survival Rates and Pre-Implant Residual Bone Height In general, success rates are used to describe implants that have an ideal quality of health with marginal bone loss of less than 2 mm, while survival rates are used to describe implants that are stable in the mouth even with the presence of 2 to 4 mm of marginal bone loss.9 According to the Implant Quality of Health Scale adopted by the International Congress of Oral Implantologists, Pisa, Italy, Consensus Conference, 2007, implant “satisfactory” survival is defined based on the presence of the following four criteria: (1) absence of pain on function; (2) absence of mobility; (3) less than 4-mm radiographic marginal bone loss; and (4) absence of peri-implant infection with suppuration.9 Therefore, we prefer to use the survival rate as a clinical indicator to describe the practical criterion of implant success. Based on the results of a multicenter retrospective study, whenever the pre-implant residual bone height decreases, the implant survival rate decreases.10 Most of this decrease in survival rate is expected when the preimplant bone height is less than 5 mm.10,11 This observed correlation between pre-implant residual bone height and survival rate reveals an important clinical point that requires further consideration when we develop treatment plans for implants placed in posterior maxilla.
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Surgical Considerations Sinus lift procedure has increasingly become a common practice especially when the insufficient heights of residual bone prevent the placement of dental implants in maxillary posterior alveolar ridge. Sinus lift procedure is usually indicated, whenever the residual bone reveals a height of 10 mm or less in posterior maxilla.12 The two surgical approaches that have been contemporarily used to manage the atrophic posterior maxilla are (1) lateral window/direct approach and (2) osteotome transcrestal/ indirect approach. The first lateral window procedure was performed by Tatum13 in 1975. A window opening is created surgically in the lateral sinus wall followed by elevating the Schneiderian membrane to allow placing implant(s) of appropriate length. The use of lateral approach can increase the vertical bone height greater than 9 mm, which is necessary when we have large bone shortages. To prevent the perforation of Schneiderian membrane, piezoelectric ultrasonic surgery has been introduced to provide safe membrane lifting and to support hand instrumentation during lateral window procedure.14 The piezoelectric handpiece allows adequate bone removal while maintaining the integrity of surrounding soft tissues (i.e., the Schneiderian membrane and PSAA).14,15 Although early results sound promising, further studies are still needed to prove evidently the clinical effectiveness of this innovative technique in sinus lift surgery. On the other hand, osteotome approach was first used by Summers16 in 1994. A transalveolar elevation of the maxillary sinus floor is performed to provide easier surgical intervention, shorter surgical time, lesser complications, and slighter morbidity as well as greater patient satisfaction. The use of osteotome approach can produce an approximate increase in vertical bone height that ranges from 3 to 9 mm (Table 2).12,17–20 Recently, several minimal invasive techniques have been developed to enhance the outcomes of osteotome approach, to provide less invasive surgical intervention, and to maximize patient satisfaction. The antral membrane balloon elevation (AMBE) is a minimally invasive technique used to elevate gradually the Schneiderian membrane while optimally maintaining its integrity. A steady gentle pressure is applied to detach the membrane when the latex balloon is inflated. This technique is relatively safe with less postoperative bleeding, pain, or
Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014
TABLE 3 Sinus Lift Procedures Indicated in Posterior Maxilla according to the Available Residual Bone Height and the Amount of Postsurgical Increase in Bone Height Needed
3.5 mm 10 mm 12.7 mm 9.1 mm * 9.1 1 0.3 mm * 3.2 1 1.5 mm 2.2 1 1.7 mm 2.5 1 1.8 mm 4.4 1 0.2 mm * 8 1 1.5 mm
Intervention indicated
34 (58) * (1,197) 40 (75) 2,830 (4,388) 20 (35) 24 (*) 32 (54) 36 (53) 1,822 (3,131) 53 (68)
Without With and without Without With and without With Without Without Without With and without Without
≈2 years 3 years ≈2 years 3 years 1 year ≈1.5 years 1 year 3 years 5 years 13 years
91.4% 95.7% 97.3% 92.8% 97.1% 100% 100% 94% 95.81% 100%
Sinus lift procedure Osteotome approach Lateral approach
Winter et al. (2002)18 Emmerich et al. (2005)24 Leblebicioglu et al. (2005)19 Tan et al. (2008)25 Diss et al. (2008)56 Schmidlin et al. (2008)57 Nedir et al. (2009)58 Fermergard and Astrand (2012)12 Del Fabbro et al. (2012)20 Bruschi et al. (2013)17
*Number(s) not available or calculated because of data variability.
II-3 I II-3 I II-3 II-3 II-3 II-3 I II-3 Retrospective Systematic review Prospective Systematic review Prospective Retrospective Prospective Prospective Systematic review Prospective
95% 2.5 years With 30 (79) II-3 Prospective
Osteotome Lateral 1 step Lateral 2 steps Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Zitzmann and Schärer (1998)55
Level of evidence Study design Surgical approach Study (year)
TABLE 2 Effects of Sinus Lift Surgery in Vertical Residual Bone Height
Number of patients (implants)
Bone grafting
Follow-up duration
Survival rate
Mean increase in vertical bone height
4
Residual bone height
Required increase in bone height
210 mm >5 mm 25 mm
>3 mm 3–9 mm >9 mm
discomfort.21,22 Longitudinal studies of large sample sizes are still needed to prove the clinical effectiveness and prognosis of the AMBE. Using the piezoelectric ultrasound surgical technology, Intralift™ technique has been developed recently to simplify osteotome approach, allowing adequate sinus lift while minimizing patient discomfort. TKW-5 tip, which is a “trumpet” with non-cutting head, is used to spray sterile irrigation that detach the Schneiderian membrane by microcavitation.23 More importantly, this technique reduces notably the risk of perforation of Schneiderian membrane, because the surgical instruments used in sinus lifting are less aggressive and maintain the least physical contact with Schneiderian membrane.23 Selecting the appropriate sinus lift surgical technique is largely based on the height of pre-implant residual bone. With a residual bone height of more than 5 mm, the transcrestal approach is usually indicated; otherwise, when the residual bone height is 5 mm or less, lateral window approach is indicated (Table 3).16,20,24–26 Placing implants in posterior maxilla using thinner drills can improve the primary implant stability, help in overcoming the poor quality of bone and, more importantly, increase the survival rates of dental implants in posterior maxilla.27 Rough surface implants with membrane coverage of lateral window can provide higher survival rates.28 We advise that sinus lift procedures should remain simple, fast, and safe with low morbidity in order to maintain the highest patient satisfaction. Future studies should be directed toward eliciting patient preferences and their satisfaction following sinus lift surgery when different types of bone grafts or surgical approaches are implemented. Sinus Bone Grafting Autogenous bone graft taken from the same patient has a long track of clinical success in sinus augmentation
Clinical and radiographical
I
I
Systematic review
Prospective randomized controlled trial
Esposito et al. (2010)33 Lindgren et al. (2012)34
Biphasic calcium phosphate versus deproteinized bovine bone
I
Different materials
Clinical
There was no significant difference between the two types of bone graft used. The success of the procedure, its complications, or implant survival is not dependent on the type of bone graft used. No evidence of difference in clinical outcomes between different bone graft materials. Implant success rate was not dependent on the biomaterial used for maxillary sinus augmentation. Histological and histomorphometric Clinical and radiographical Autogenous bone versus beta-tricalcium phosphate graft Different materials I
Prospective multicenter randomized control trial Systematic review Szabo et al. (2005)32 Nkenke and Stelzle (2009)35
Outcome Type of evaluation Type of bone graft Level of evidence Study design Study (year)
due to its unique osteoconductive, osteogenic, and osteoinductive properties.29 Although autogenous bone graft remains the “gold standard,” easier substitutes made of synthetic or bovine-derived bone grafts are available for sinus augmentation.30–33 Neither implant osseointegration nor marginal bone loss is dependent on the type of bone graft used in sinus augmentation (Table 4).32–35 Longitudinal randomized controlled trials of large sample size are still needed to evaluate clinical outcomes and efficacies between the different types of bone grafting materials used in sinus augmentation. Likewise, cost-effectiveness analysis or cost-utility analysis is also needed to determine the most efficient sinus bone graft material with the best implant survival rate. Sinus augmentation can be enhanced by the clinical application of biologic modifiers and growth factors mainly, recombinant human platelet-derived growth factor BB (rhPDGF-BB) and recombinant human bone morphogenetic proteins (rhBMPs).36 Out of the transforming growth factor-β family, rhBMPs (including BMP-2, BMP-7, and growth differentiation factor 5) have been widely used to prepare implant bed for osseointegration, to accelerate wound healing, and to enhance regenerative activities in residual alveolar bone ridge.36 Despite their predictable therapeutic effects, the use of rhBMPs should follow strict clinical guidelines. rhBMPs should be applied in a pharmaceutical form that assures a controlled and sustained release in order to prevent any undesirable side effects, as these proteins in very high doses can induce cancer.37 One of the methods used to control rhBMP release is to have rhBMP molecules contained within an absorbable collagen sponge, which will be placed in the compartment after lifting the Schneiderian membrane. Similar to rhBMPs, the use of rhPDGF-BBs is also suggested to improve the outcomes of sinus lift surgery and to decrease patient morbidity; however, there is still a lack of evidence to support the clinical efficacy and effectiveness of using rhPDGF-BBs in sinus augmentation. Platelet-rich plasma (PRP) has been used as a potential source for growth factors that can accelerate bone healing. Currently, there is no evidence to prove that using PRP in sinus lift surgery has positive enhancements on bone graft healing, especially in terms of clinical outcomes and effectiveness.38,39 Mononuclear stem cells (MSCs), which are isolated from human adult bone marrow, appear as a promising
TABLE 4 The Effect of Using Different Bone Graft Biomaterials on Implant Osseointegration and Marginal Bone Loss Following Sinus Augmentation Surgery
Recent Trends in Sinus Lift Surgery
5
Radiographical
New bone formation occurs with or without grafting, but larger bone gain was recorded with grafting. Osteotome without grafting is sufficient to create new bone formation. II-3
With and without Without Osteotome
Prospective randomized controlled trial Prospective Osteotome
I
Without II-3 Prospective Osteotome
Fermergard and Astrand (2008)45 Pjetursson et al. (2009)46 Nedir et al. (2009)47
Without Prospective Lateral window
II-3
Without II-3 Prospective Lateral window
Clinical and radiographical Radiographical
Bone formation occurs after sinus lift surgery without grafting. Bone formation can occur following sinus membrane elevation without grafting. Bone formation occurs following sinus lift surgery with simultaneously placed dental implants without grafting. Bone formation occurs without grafting. Clinical and radiographical Clinical and radiographical Radiographical Without II-3 Prospective Lateral window
Lundgren et al. (2004)42 Thor et al. (2007)43 Hatano et al. (2007)44
Type of evaluation Bone Grafting Level of evidence Study design
The perforation of Schneiderian membrane is one of the most common sinus lift complications. This perforation has an important impact on sinus integrity and can compromise the bone graft survival. In a recent longitudinal study of 359 sinus lift procedures, 7 out of every 10 failed sinus grafts were accompanied by a perforated Schneiderian membrane during sinus lift surgery.48 The sinus membrane perforation doubled noticeably the risk for the incidence of sinusitis or infection.48 However, both marginal bone loss around implant and sinus bone graft absorption were not increased by the perforation of Schneiderian membrane.49 The management of perforated Schneiderian membrane is performed intraoperatively depending primarily on the location and size of perforation.50 Once the perforation happened, implantologist should avoid applying any unnecessary pressure that could increase the size of perforation. In minor perforations, folding the membrane on itself can be sufficient. Small perforations can be managed using a small collagen tape and a bioabsorbable membrane. In large perforations, careful suturing or application of fibrin adhesive should be considered to close the perforation. Also, a bioabsorbable membrane should be placed only on the surface of sutured Schneiderian membrane.50 The walls of the sinus are not covered in order to maintain continuous blood supply to the bone graft.
Surgical approach
Perforation of Schneiderian Membrane
Study (year)
bioactive material. MSCs induce bone formation in a way that mimics the clinical efficacy of autogenous bone graft.40 In a randomized controlled split-mouth trial, “bovine bone mineral (BioOss®) seeded with MSCs harvested from the posterior iliac crest” improved evidently bone formation after sinus lift surgery.41 On the other hand, several studies have intensified the debate over the necessity of bone grafting after sinus lift procedures, whether these procedures were lateral window approach42–44 or osteotome transcrestal approach45–47 (Table 5). Once the compartment is created between the elevated Schneiderian membrane, implant, and the osseous floor of the sinus, new bone formation will spontaneously fill this compartment. Further histological studies are needed to understand the mechanisms of sinus bone healing without the presence of bone grafting, as well as longitudinal studies to evaluate the clinical prognosis of this newly formed bone.
Outcome
Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014
TABLE 5 Healing and Bone Formation at the Floor of Maxillary Sinus Following Membrane Elevation and Simultaneous Implant Placement Without Grafting in Sinus Lift Procedures
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Recent Trends in Sinus Lift Surgery
To dodge the undesirable complications of sinus lift procedures, several studies explored placing nonconventional tilted, nasal, or zygomatic implants without any bone grafting in atrophic posterior maxilla.51–54 Although the primary outcomes are promising, longitudinal randomized controlled trials with larger sample size are still necessary to prove the efficacy of these innovative interventions.33 Aside from the many benefits associated with the sinus lift surgery, there are also risks to consider from the perforation of Schneiderian membrane. Therefore, an appropriate training on sinus lift surgery is mandatory to increase the clinical outcome and to control the potential of complications. Keeping in mind that implant’s failure is the worst case scenario and the most difficult to treat, dentists should exert every possible effort to assure that their implants, especially in posterior maxilla, are planned and placed to achieve the best possible outcomes esthetically and functionally. CONCLUSIONS Placing implants in atrophic maxillary posterior ridge is a difficult challenge that dentists encounter in their regular implant practice. Whenever indicated, either the osteotome transcrestal approach or the lateral window approach can be effectively used to achieve an appropriate bone height to support the placement of implants. In addition to the current clinical practice guidelines, whenever you face an atrophic posterior maxilla, our advice is to: • • •
• •
•
Assess pre-implant bone quality and quantity using appropriate three-dimensional CBCT radiographs. Leave at least 1 to 2 mm of bone between implant apex and the sinus floor level. Be aware (and acknowledge your patient) of the lower survival rates of implants when pre-implant bone height is less than 5 mm. Use sinus lift procedures only with residual bone height of 10 mm or less. Use the appropriate sinus lift procedure in accordance with the available pre-implant residual bone height as well as the necessary amount of increase in that bone height. Avoid lengthy, invasive, and complex sinus left surgeries. Sinus lift procedures should remain simple, fast, and safe with low morbidity in order to maintain the highest patient satisfaction.
• •
7
Use a combination of autogenous and alternative bone grafts as needed. Exert every effort to avoid the perforation of Schneiderian membrane.
Although both osteotome and lateral window procedures can help clinicians in overcoming the challenges of placing implants in atrophic posterior maxilla, pre-implant residual bone height is crucial in determining the survival of these implants. Future research directions should consider study designs grounded on longitudinal randomized controlled trials of large sample size. REFERENCES 1. Sogo M, Ikebe K, Yang TC, Wada M, Maeda Y. Assessment of bone density in the posterior maxilla based on Hounsfield units to enhance the initial stability of implants. Clin Implant Dent Relat Res 2012; 14(Suppl 1):e183–e187. 2. Nunes LS, Bornstein MM, Sendi P, Buser D. Anatomical characteristics and dimensions of edentulous sites in the posterior maxillae of patients referred for implant therapy. Int J Periodontics Restorative Dent 2013; 33:337–345. 3. Pommer B, Ulm C, Lorenzoni M, et al. Prevalence, location and morphology of maxillary sinus septa: systematic review and meta-analysis. J Clin Periodontol 2012; 39:769– 773. 4. Hur MS, Kim JK, Hu KS, et al. Clinical implications of the topography and distribution of the posterior superior alveolar artery. J Craniofac Surg 2009; 20:551–554. 5. Guncu GN, Yildirim YD, Wang HL, Tozum TF. Location of posterior superior alveolar artery and evaluation of maxillary sinus anatomy with computerized tomography: a clinical study. Clin Oral Implants Res 2011; 22:1164–1167. 6. Solar P, Geyerhofer U, Traxler H, et al. Blood supply to the maxillary sinus relevant to sinus floor elevation procedures. Clin Oral Implants Res 1999; 10:34–44. 7. Manor Y, Mardinger O, Bietlitum I, et al. Late signs and symptoms of maxillary sinusitis after sinus augmentation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 110:e1–e4. 8. Doud Galli SK, Lebowitz RA, Giacchi RJ, Glickman R, Jacobs JB. Chronic sinusitis complicating sinus lift surgery. Am J Rhinol 2001; 15:181–186. 9. Misch CE, Perel ML, Wang HL, et al. Implant success, survival, and failure: the International Congress of Oral Implantologists (ICOI) Pisa Consensus Conference. Implant Dent 2008; 17:5–15. 10. 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; 14:853–858.
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39.
40.
41.
42.
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45.
46.
47.
48.
a controlled prospective 5-year study. Clin Implant Dent Relat Res 2005; 7:209–220. Raghoebar GM, Schortinghuis J, Liem RS, et al. Does platelet-rich plasma promote remodeling of autologous bone grafts used for augmentation of the maxillary sinus floor? Clin Oral Implants Res 2005; 16:349–356. Sauerbier S, Rickert D, Gutwald R, et al. Bone marrow concentrate and bovine bone mineral for sinus floor augmentation: a controlled, randomized, single-blinded clinical and histological trial–per-protocol analysis. Tissue Eng Part A 2011; 17:2187–2197. Rickert D, Sauerbier S, Nagursky H, et al. Maxillary sinus floor elevation with bovine bone mineral combined with either autogenous bone or autogenous stem cells: a prospective randomized clinical trial. Clin Oral Implants Res 2011; 22:251–258. Lundgren S, Andersson S, Gualini F, Sennerby L. Bone reformation with sinus membrane elevation: a new surgical technique for maxillary sinus floor augmentation. Clin Implant Dent Relat Res 2004; 6:165–173. Thor A, Sennerby L, Hirsch JM, Rasmusson L. Bone formation at the maxillary sinus floor following simultaneous elevation of the mucosal lining and implant installation without graft material: an evaluation of 20 patients treated with 44 Astra Tech implants. J Oral Maxillofac Surg 2007; 65(7 Suppl 1):64–72. Hatano N, Sennerby L, Lundgren S. Maxillary sinus augmentation using sinus membrane elevation and peripheral venous blood for implant-supported rehabilitation of the atrophic posterior maxilla: case series. Clin Implant Dent Relat Res 2007; 9:150–155. Fermergard R, Astrand P. Osteotome sinus floor elevation and simultaneous placement of implants–a 1-year retrospective study with Astra Tech implants. Clin Implant Dent Relat Res 2008; 10:62–69. Pjetursson BE, Ignjatovic D, Matuliene G, et al. Transalveolar maxillary sinus floor elevation using osteotomes with or without grafting material. Part II: radiographic tissue remodeling. Clin Oral Implants Res 2009; 20:677–683. Nedir R, Bischof M, Vazquez L, et al. Osteotome sinus floor elevation technique without grafting material: 3-year results of a prospective pilot study. Clin Oral Implants Res 2009; 20:701–707. Nolan PJ, Freeman K, Kraut RA. Correlation between Schneiderian membrane perforation and sinus lift graft
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
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outcome: a retrospective evaluation of 359 augmented sinus. J Oral Maxillofac Surg 2014; 72:47–52. Bae JH, Kim YK, Kim SG, Yun PY, Kim JS. Sinus bone graft using new alloplastic bone graft material (Osteon)-II: clinical evaluation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 109:e14–e20. Fugazzotto PA, Vlassis J. A simplified classification and repair system for sinus membrane perforations. J Periodontol 2003; 74:1534–1541. Malo P, Nobre M, Lopes A. Immediate loading of “All-on-4” maxillary prostheses using trans-sinus tilted implants without sinus bone grafting: a retrospective study reporting the 3-year outcome. Eur J Oral Implantol 2013; 6:273– 283. Malo P, Nobre M, Lopes A, Francischone C, Rigolizzo M. Three-year outcome of a retrospective cohort study on the rehabilitation of completely edentulous atrophic maxillae with immediately loaded extra-maxillary zygomatic implants. Eur J Oral Implantol 2012; 5:37–46. Davo R, Malevez C, Rojas J, Rodriguez J, Regolf J. Clinical outcome of 42 patients treated with 81 immediately loaded zygomatic implants: a 12- to 42-month retrospective study. Eur J Oral Implantol 2008; 1:141–150. Aparicio C, Ouazzani W, Aparicio A, et al. Extrasinus zygomatic implants: three year experience from a new surgical approach for patients with pronounced buccal concavities in the edentulous maxilla. Clin Implant Dent Relat Res 2010; 12:55–61. 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; 85:8–17. Diss A, Dohan DM, Mouhyi J, Mahler P. Osteotome sinus floor elevation using Choukroun’s platelet-rich fibrin as grafting material: a 1-year prospective pilot study with microthreaded implants. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008; 105:572–579. Schmidlin PR, Muller J, Bindl A, Imfeld H. Sinus floor elevation using an osteotome technique without grafting materials or membranes. Int J Periodontics Restorative Dent 2008; 28:401–409. Nedir R, Nurdin N, Szmukler-Moncler S, Bischof M. Placement of tapered implants using an osteotome sinus floor elevation technique without bone grafting: 1-year results. Int J Oral Maxillofac Implants 2009; 24:727–733.
ABSTRACT Background: Sinus lift procedures are used to allow residual bone to accommodate functional implants in atrophic posterior maxilla. Numerous anatomical and surgical advancements in sinus lift surgery are still inspiring clinicians. Purpose: The purpose of this study was to describe the recent trends in sinus lift surgery focusing on implant survival, bone grafting, anatomical and surgical considerations, and their clinical implications on the practice of implant dentistry in atrophic posterior maxilla. Materials and Methods: We performed an extensive search in MEDLINE, Embase, Scopus, Web of Science, Trip, Cochrane Oral Health Group’s Trials Register, Cochrane Central Register of Controlled Trials, and ProQuest Dissertations & Theses. Articles were critically reviewed to determine the level of evidence as per the Canadian Task Force on Preventive Health Care. Results: Comprehensive assessment of sinus septa, sinus pathology, and bone quality and quantity using three-dimensional cone beam computed tomography radiographs is important before placing implants in posterior maxilla. With a residual bone height of less than 5 mm, the survival rate of implant decreases substantially. Lateral window approach can increase the vertical bone height to greater than 9 mm, while osteotome approach can increase this height from 3 to 9 mm. The perforation of Schneiderian membrane doubles the risk for the incidence of sinusitis or infection. The use of piezoelectric surgery allows adequate sinus lift while protecting soft tissues and minimizing patient discomfort. Conclusions: Although both osteotome and lateral window procedures can help clinicians in overcoming the challenges of placing implants in atrophic posterior maxilla, pre-implant residual bone height is crucial in determining the survival of these implants. Future research directions should consider study designs grounded on longitudinal randomized controlled trials of large sample size. KEY WORDS: dental implants, lateral window, osteotome intracrestal, sinus augmentation, sinus elevation, sinus lift
INTRODUCTION
the floor of maxillary sinus in an upward direction, creating an appropriate bone height that can accommodate appropriately the placement of functional dental implants. Sinus lift surgery is usually followed by bone grafting in order to fill the compartment created between the osseous floor of the maxillary sinus and the Schneiderian membrane. Recent anatomical and surgical advancements in the understanding and conduct of sinus lift surgery are numerous. These advancements remain the main sources of inspiration that help clinicians to innovate, develop, and maintain a high standard of implant practice outcomes and expectations as well as patient satisfaction. In this article, we will review the literature for the recent scientific trends in sinus lift surgery focusing on implant survival, bone grafting, anatomical and surgical considerations, and their clinical implications on the practice of implant dentistry in atrophic posterior maxilla.
Atrophic posterior maxilla is a challenging anatomical area for the placement of dental implants. Whenever the diagnosis reveals insufficient residual bone height in posterior maxilla, sinus lift procedure (or residual bone augmentation) is indicated. Sinus lift procedure is a surgical intervention aimed at increasing the height of residual bone in the posterior maxilla by repositioning Researcher and instructor, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada Corresponding Author: Dr. Mahmoud Al-Dajani, Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, ON M5G 1G6, Canada; e-mail: [email protected] Conflict of Interest: No potential conflict of interest relevant to this article was reported. © 2014 Wiley Periodicals, Inc. DOI 10.1111/cid.12275
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MATERIALS AND METHODS We performed an extensive search of the literature to identify articles published between 1975 and 2014 dealing with patients managed with pre-implant sinus lift procedure through different surgical approaches. An electronic search was conducted in MEDLINE, Embase, Scopus, Web of Science, Trip, Cochrane Oral Health Group’s Trials Register, Cochrane Central Register of Controlled Trials, and ProQuest Dissertations & Theses. The bibliographies of review articles were also checked. The last electronic search was performed on April 4, 2014, entering the following terms: “dental implant” AND (“sinus augmentation” OR “sinus lift”). Literature was also identified through reference lists of selected articles. Only articles in English were included. Articles were critically reviewed to determine the level of evidence as per the Canadian Task Force on Preventive Health Care. Table 1 shows the key words and their combinations used in the literature search. Thirty-seven articles were included in the review tables, and distributed as follows: 7 retrospective studies, 20 prospective cohort/case series, 4 randomized controlled trials, and 6 systematic reviews with/without meta-analyses. Posterior Maxilla: Anatomical Considerations Limitations for placing an implant in the posterior maxilla are related not only to the residual bone height and width but also to the quality of maxillary bone. Poor bone quantity and quality in posterior maxilla are usually blamed for the decreased primary implant
TABLE 1 Literature Computerized Search Strategy Step
1 2 3 4 5 6 7 8 9
Keywords, search history, and criteria
Number of articles
“dental implant” “sinus augmentation” OR “sinus lift” (1 AND 2) Search limited to humans Search limited to English-language articles Relevant articles at title stage Relevant articles at abstract stage Relevant articles at full copy stage Adding three articles from reference lists of selected articles Articles included in review tables
7,153 1,691 209 184 169 35 35 35 37 37
stability and increased failure rates.1 Several factors enhance the loss of posterior maxillary residual bone after tooth extraction including: long-term tooth loss, trauma, infection, and advanced periodontal disease. Bone loss problem is further complicated with the associated downward movement of the sinus floor.1 This movement could be explained by the post-extraction change in intra-sinus equilibrium associated with increased activity of osteoclasts in the Schneiderian membrane, which fosters the maxillary sinus pneumatization phenomena. The decreased bone density and increased cortical plate porosity in posterior maxilla are additional characteristics that emphasize the need for assessing bone quality as well as quantity before placing implants in posterior maxilla.1 This thorough assessment is essential in planning the future place of dental implants in posterior maxilla, and can be accomplished by the use of three-dimensional cone beam computed tomography (CBCT) radiographs.2 Beside bone characteristics of posterior maxilla, two anatomical structures can importantly interfere with or even complicate bone grafting in sinus lift surgery: maxillary sinus septa and posterior superior alveolar artery (PSAA). Maxillary sinus septa are usually encountered in one out of four sinuses exhibiting a great degree of morphological and structural variability: complete versus partial; single versus multiple; unilateral versus bilateral; and transverse, sagittal versus horizontal.3 CBCT radiography remains the most accurate tool to diagnose and identify these septa in maxillary sinus.3 PSAA is the second important anatomical structure that implantologists need to respect in order to avoid the incidence of severe bleeding during the lateral window sinus lift surgery. PSAA enters the maxillary sinus through the posterior superior alveolar foramen at the posterior wall of maxilla. The intra-osseous branch of PSAA invaginates on the buccal (lateral) wall of sinus following either a straight or U-shaped course,4 and running at an approximate height of 19 mm away from the alveolar bone ridge.5,6 This height is usually shortest in the first molar area.4 We need to keep in our mind that the distance between the intra-osseous branch of PSAA and alveolar bone ridge decreases significantly in edentulous areas over time. The normal anatomy of Schneiderian membrane is structurally affected by the presence of potent
Recent Trends in Sinus Lift Surgery
pathology, which reflects negatively on the outcomes of sinus lift surgery.7 For example, preoperative chronic sinusitis can produce pathological and pathophysiological changes in Schneiderian membrane, hindering the normal ability of injured Schneiderian membrane to recover after surgery, and consequently increasing the risk for complications, bone graft loss, and even implant failure.7,8 Therefore, implantologists should pay special attention to evaluate the anatomical and physiological status of maxillary sinus to ensure the readiness of Schneiderian membrane for sinus lift surgery. The controversy surrounding the minimal necessary distance between the tip of implants and the floor of maxillary sinus has drawn continuous debate. Although there is no clear evidence that implants with tips placed within or with less than 1 mm away from the sinus floor level would fail, the preference among clinicians is to leave 1 to 2 mm of bone before the radiographically estimated sinus floor level. Survival Rates and Pre-Implant Residual Bone Height In general, success rates are used to describe implants that have an ideal quality of health with marginal bone loss of less than 2 mm, while survival rates are used to describe implants that are stable in the mouth even with the presence of 2 to 4 mm of marginal bone loss.9 According to the Implant Quality of Health Scale adopted by the International Congress of Oral Implantologists, Pisa, Italy, Consensus Conference, 2007, implant “satisfactory” survival is defined based on the presence of the following four criteria: (1) absence of pain on function; (2) absence of mobility; (3) less than 4-mm radiographic marginal bone loss; and (4) absence of peri-implant infection with suppuration.9 Therefore, we prefer to use the survival rate as a clinical indicator to describe the practical criterion of implant success. Based on the results of a multicenter retrospective study, whenever the pre-implant residual bone height decreases, the implant survival rate decreases.10 Most of this decrease in survival rate is expected when the preimplant bone height is less than 5 mm.10,11 This observed correlation between pre-implant residual bone height and survival rate reveals an important clinical point that requires further consideration when we develop treatment plans for implants placed in posterior maxilla.
3
Surgical Considerations Sinus lift procedure has increasingly become a common practice especially when the insufficient heights of residual bone prevent the placement of dental implants in maxillary posterior alveolar ridge. Sinus lift procedure is usually indicated, whenever the residual bone reveals a height of 10 mm or less in posterior maxilla.12 The two surgical approaches that have been contemporarily used to manage the atrophic posterior maxilla are (1) lateral window/direct approach and (2) osteotome transcrestal/ indirect approach. The first lateral window procedure was performed by Tatum13 in 1975. A window opening is created surgically in the lateral sinus wall followed by elevating the Schneiderian membrane to allow placing implant(s) of appropriate length. The use of lateral approach can increase the vertical bone height greater than 9 mm, which is necessary when we have large bone shortages. To prevent the perforation of Schneiderian membrane, piezoelectric ultrasonic surgery has been introduced to provide safe membrane lifting and to support hand instrumentation during lateral window procedure.14 The piezoelectric handpiece allows adequate bone removal while maintaining the integrity of surrounding soft tissues (i.e., the Schneiderian membrane and PSAA).14,15 Although early results sound promising, further studies are still needed to prove evidently the clinical effectiveness of this innovative technique in sinus lift surgery. On the other hand, osteotome approach was first used by Summers16 in 1994. A transalveolar elevation of the maxillary sinus floor is performed to provide easier surgical intervention, shorter surgical time, lesser complications, and slighter morbidity as well as greater patient satisfaction. The use of osteotome approach can produce an approximate increase in vertical bone height that ranges from 3 to 9 mm (Table 2).12,17–20 Recently, several minimal invasive techniques have been developed to enhance the outcomes of osteotome approach, to provide less invasive surgical intervention, and to maximize patient satisfaction. The antral membrane balloon elevation (AMBE) is a minimally invasive technique used to elevate gradually the Schneiderian membrane while optimally maintaining its integrity. A steady gentle pressure is applied to detach the membrane when the latex balloon is inflated. This technique is relatively safe with less postoperative bleeding, pain, or
Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014
TABLE 3 Sinus Lift Procedures Indicated in Posterior Maxilla according to the Available Residual Bone Height and the Amount of Postsurgical Increase in Bone Height Needed
3.5 mm 10 mm 12.7 mm 9.1 mm * 9.1 1 0.3 mm * 3.2 1 1.5 mm 2.2 1 1.7 mm 2.5 1 1.8 mm 4.4 1 0.2 mm * 8 1 1.5 mm
Intervention indicated
34 (58) * (1,197) 40 (75) 2,830 (4,388) 20 (35) 24 (*) 32 (54) 36 (53) 1,822 (3,131) 53 (68)
Without With and without Without With and without With Without Without Without With and without Without
≈2 years 3 years ≈2 years 3 years 1 year ≈1.5 years 1 year 3 years 5 years 13 years
91.4% 95.7% 97.3% 92.8% 97.1% 100% 100% 94% 95.81% 100%
Sinus lift procedure Osteotome approach Lateral approach
Winter et al. (2002)18 Emmerich et al. (2005)24 Leblebicioglu et al. (2005)19 Tan et al. (2008)25 Diss et al. (2008)56 Schmidlin et al. (2008)57 Nedir et al. (2009)58 Fermergard and Astrand (2012)12 Del Fabbro et al. (2012)20 Bruschi et al. (2013)17
*Number(s) not available or calculated because of data variability.
II-3 I II-3 I II-3 II-3 II-3 II-3 I II-3 Retrospective Systematic review Prospective Systematic review Prospective Retrospective Prospective Prospective Systematic review Prospective
95% 2.5 years With 30 (79) II-3 Prospective
Osteotome Lateral 1 step Lateral 2 steps Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Osteotome Zitzmann and Schärer (1998)55
Level of evidence Study design Surgical approach Study (year)
TABLE 2 Effects of Sinus Lift Surgery in Vertical Residual Bone Height
Number of patients (implants)
Bone grafting
Follow-up duration
Survival rate
Mean increase in vertical bone height
4
Residual bone height
Required increase in bone height
210 mm >5 mm 25 mm
>3 mm 3–9 mm >9 mm
discomfort.21,22 Longitudinal studies of large sample sizes are still needed to prove the clinical effectiveness and prognosis of the AMBE. Using the piezoelectric ultrasound surgical technology, Intralift™ technique has been developed recently to simplify osteotome approach, allowing adequate sinus lift while minimizing patient discomfort. TKW-5 tip, which is a “trumpet” with non-cutting head, is used to spray sterile irrigation that detach the Schneiderian membrane by microcavitation.23 More importantly, this technique reduces notably the risk of perforation of Schneiderian membrane, because the surgical instruments used in sinus lifting are less aggressive and maintain the least physical contact with Schneiderian membrane.23 Selecting the appropriate sinus lift surgical technique is largely based on the height of pre-implant residual bone. With a residual bone height of more than 5 mm, the transcrestal approach is usually indicated; otherwise, when the residual bone height is 5 mm or less, lateral window approach is indicated (Table 3).16,20,24–26 Placing implants in posterior maxilla using thinner drills can improve the primary implant stability, help in overcoming the poor quality of bone and, more importantly, increase the survival rates of dental implants in posterior maxilla.27 Rough surface implants with membrane coverage of lateral window can provide higher survival rates.28 We advise that sinus lift procedures should remain simple, fast, and safe with low morbidity in order to maintain the highest patient satisfaction. Future studies should be directed toward eliciting patient preferences and their satisfaction following sinus lift surgery when different types of bone grafts or surgical approaches are implemented. Sinus Bone Grafting Autogenous bone graft taken from the same patient has a long track of clinical success in sinus augmentation
Clinical and radiographical
I
I
Systematic review
Prospective randomized controlled trial
Esposito et al. (2010)33 Lindgren et al. (2012)34
Biphasic calcium phosphate versus deproteinized bovine bone
I
Different materials
Clinical
There was no significant difference between the two types of bone graft used. The success of the procedure, its complications, or implant survival is not dependent on the type of bone graft used. No evidence of difference in clinical outcomes between different bone graft materials. Implant success rate was not dependent on the biomaterial used for maxillary sinus augmentation. Histological and histomorphometric Clinical and radiographical Autogenous bone versus beta-tricalcium phosphate graft Different materials I
Prospective multicenter randomized control trial Systematic review Szabo et al. (2005)32 Nkenke and Stelzle (2009)35
Outcome Type of evaluation Type of bone graft Level of evidence Study design Study (year)
due to its unique osteoconductive, osteogenic, and osteoinductive properties.29 Although autogenous bone graft remains the “gold standard,” easier substitutes made of synthetic or bovine-derived bone grafts are available for sinus augmentation.30–33 Neither implant osseointegration nor marginal bone loss is dependent on the type of bone graft used in sinus augmentation (Table 4).32–35 Longitudinal randomized controlled trials of large sample size are still needed to evaluate clinical outcomes and efficacies between the different types of bone grafting materials used in sinus augmentation. Likewise, cost-effectiveness analysis or cost-utility analysis is also needed to determine the most efficient sinus bone graft material with the best implant survival rate. Sinus augmentation can be enhanced by the clinical application of biologic modifiers and growth factors mainly, recombinant human platelet-derived growth factor BB (rhPDGF-BB) and recombinant human bone morphogenetic proteins (rhBMPs).36 Out of the transforming growth factor-β family, rhBMPs (including BMP-2, BMP-7, and growth differentiation factor 5) have been widely used to prepare implant bed for osseointegration, to accelerate wound healing, and to enhance regenerative activities in residual alveolar bone ridge.36 Despite their predictable therapeutic effects, the use of rhBMPs should follow strict clinical guidelines. rhBMPs should be applied in a pharmaceutical form that assures a controlled and sustained release in order to prevent any undesirable side effects, as these proteins in very high doses can induce cancer.37 One of the methods used to control rhBMP release is to have rhBMP molecules contained within an absorbable collagen sponge, which will be placed in the compartment after lifting the Schneiderian membrane. Similar to rhBMPs, the use of rhPDGF-BBs is also suggested to improve the outcomes of sinus lift surgery and to decrease patient morbidity; however, there is still a lack of evidence to support the clinical efficacy and effectiveness of using rhPDGF-BBs in sinus augmentation. Platelet-rich plasma (PRP) has been used as a potential source for growth factors that can accelerate bone healing. Currently, there is no evidence to prove that using PRP in sinus lift surgery has positive enhancements on bone graft healing, especially in terms of clinical outcomes and effectiveness.38,39 Mononuclear stem cells (MSCs), which are isolated from human adult bone marrow, appear as a promising
TABLE 4 The Effect of Using Different Bone Graft Biomaterials on Implant Osseointegration and Marginal Bone Loss Following Sinus Augmentation Surgery
Recent Trends in Sinus Lift Surgery
5
Radiographical
New bone formation occurs with or without grafting, but larger bone gain was recorded with grafting. Osteotome without grafting is sufficient to create new bone formation. II-3
With and without Without Osteotome
Prospective randomized controlled trial Prospective Osteotome
I
Without II-3 Prospective Osteotome
Fermergard and Astrand (2008)45 Pjetursson et al. (2009)46 Nedir et al. (2009)47
Without Prospective Lateral window
II-3
Without II-3 Prospective Lateral window
Clinical and radiographical Radiographical
Bone formation occurs after sinus lift surgery without grafting. Bone formation can occur following sinus membrane elevation without grafting. Bone formation occurs following sinus lift surgery with simultaneously placed dental implants without grafting. Bone formation occurs without grafting. Clinical and radiographical Clinical and radiographical Radiographical Without II-3 Prospective Lateral window
Lundgren et al. (2004)42 Thor et al. (2007)43 Hatano et al. (2007)44
Type of evaluation Bone Grafting Level of evidence Study design
The perforation of Schneiderian membrane is one of the most common sinus lift complications. This perforation has an important impact on sinus integrity and can compromise the bone graft survival. In a recent longitudinal study of 359 sinus lift procedures, 7 out of every 10 failed sinus grafts were accompanied by a perforated Schneiderian membrane during sinus lift surgery.48 The sinus membrane perforation doubled noticeably the risk for the incidence of sinusitis or infection.48 However, both marginal bone loss around implant and sinus bone graft absorption were not increased by the perforation of Schneiderian membrane.49 The management of perforated Schneiderian membrane is performed intraoperatively depending primarily on the location and size of perforation.50 Once the perforation happened, implantologist should avoid applying any unnecessary pressure that could increase the size of perforation. In minor perforations, folding the membrane on itself can be sufficient. Small perforations can be managed using a small collagen tape and a bioabsorbable membrane. In large perforations, careful suturing or application of fibrin adhesive should be considered to close the perforation. Also, a bioabsorbable membrane should be placed only on the surface of sutured Schneiderian membrane.50 The walls of the sinus are not covered in order to maintain continuous blood supply to the bone graft.
Surgical approach
Perforation of Schneiderian Membrane
Study (year)
bioactive material. MSCs induce bone formation in a way that mimics the clinical efficacy of autogenous bone graft.40 In a randomized controlled split-mouth trial, “bovine bone mineral (BioOss®) seeded with MSCs harvested from the posterior iliac crest” improved evidently bone formation after sinus lift surgery.41 On the other hand, several studies have intensified the debate over the necessity of bone grafting after sinus lift procedures, whether these procedures were lateral window approach42–44 or osteotome transcrestal approach45–47 (Table 5). Once the compartment is created between the elevated Schneiderian membrane, implant, and the osseous floor of the sinus, new bone formation will spontaneously fill this compartment. Further histological studies are needed to understand the mechanisms of sinus bone healing without the presence of bone grafting, as well as longitudinal studies to evaluate the clinical prognosis of this newly formed bone.
Outcome
Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014
TABLE 5 Healing and Bone Formation at the Floor of Maxillary Sinus Following Membrane Elevation and Simultaneous Implant Placement Without Grafting in Sinus Lift Procedures
6
Recent Trends in Sinus Lift Surgery
To dodge the undesirable complications of sinus lift procedures, several studies explored placing nonconventional tilted, nasal, or zygomatic implants without any bone grafting in atrophic posterior maxilla.51–54 Although the primary outcomes are promising, longitudinal randomized controlled trials with larger sample size are still necessary to prove the efficacy of these innovative interventions.33 Aside from the many benefits associated with the sinus lift surgery, there are also risks to consider from the perforation of Schneiderian membrane. Therefore, an appropriate training on sinus lift surgery is mandatory to increase the clinical outcome and to control the potential of complications. Keeping in mind that implant’s failure is the worst case scenario and the most difficult to treat, dentists should exert every possible effort to assure that their implants, especially in posterior maxilla, are planned and placed to achieve the best possible outcomes esthetically and functionally. CONCLUSIONS Placing implants in atrophic maxillary posterior ridge is a difficult challenge that dentists encounter in their regular implant practice. Whenever indicated, either the osteotome transcrestal approach or the lateral window approach can be effectively used to achieve an appropriate bone height to support the placement of implants. In addition to the current clinical practice guidelines, whenever you face an atrophic posterior maxilla, our advice is to: • • •
• •
•
Assess pre-implant bone quality and quantity using appropriate three-dimensional CBCT radiographs. Leave at least 1 to 2 mm of bone between implant apex and the sinus floor level. Be aware (and acknowledge your patient) of the lower survival rates of implants when pre-implant bone height is less than 5 mm. Use sinus lift procedures only with residual bone height of 10 mm or less. Use the appropriate sinus lift procedure in accordance with the available pre-implant residual bone height as well as the necessary amount of increase in that bone height. Avoid lengthy, invasive, and complex sinus left surgeries. Sinus lift procedures should remain simple, fast, and safe with low morbidity in order to maintain the highest patient satisfaction.
• •
7
Use a combination of autogenous and alternative bone grafts as needed. Exert every effort to avoid the perforation of Schneiderian membrane.
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