October 18, 2016
by Hendrik Doering
The sinus lift is a recognized method for augmentation if the bone volume for implantation at first seems inadequate in posterior aspect of the maxilla. When the practitioner plans for such a procedure, the question is often as to whether use a lateral window approach or an indirect, supposedly less invasive, crestal approach. The following article gives an update of the available evidence and highlights findings from the literature relevant for every day practice.
The progressive bone atrophy after tooth loss and tooth extraction with continuing pneumatization of the maxillary sinus is a common finding in patients. Increasingly patients demand fixed restorations expecting long term predictable implant solutions. Hence, the subject sinus lift and bone augmentation plays an important role.
The lateral window and crestal approach are now commonly accepted pre-implant surgical techniques for bone augmentation in the maxillary lateral area prior to implant placement. The lateral window approach was first described by Tatum and Boyne in 1977 and by James in 1980 using a modified Caldwell-Luc Technique. 1 The crestal sinus lift was also presented by Tatum in 1986 refined by Summers in 1994 using osteotomes to elevate the Schneiderian membrane. 2 Therefore we can look back on more than 30 years of accumulated experience of sinus lifts. Numerous studies and review articles in recent years have shown that the sinus lift – lateral window and crestal approach – is a safe, predictable and reliable method for bone augmentation in the maxillary sinus.
Since its initial publication more than 1500 articles have investigated the topic. In order to summarize the information, numerous workshops and consensus conferences were held. Since the first Sinus Consensus Conference in 1996 (the data was collected from the participants) where the sinus lift through a lateral window was deemed no longer experimental to the most recent ITI Consensus Conference in 2009 (59 articles with more than 5000 procedures) some major findings have been identified. 3,4 In cases where a lateral window approach was performed, the implant survival rate is reported at 95%, perforations were observed in 10% of the patients and post-operative complications occurred in 3% of the patients. Regarding the choice of bone grafting material, no significant differences were observed and roughened surface implants performed better than smooth surface implants. Also, the particulate graft was identified to being superior over the block graft. In summary, there is strong evidence that the lateral window approach is successful in regenerating sufficient bone for implant placement. Nevertheless, it was identified that membrane perforations are an issue.
Regarding the crestal approach, numerous variations and innovative modifications of the initial Summers osteotome approach have been described. 5,7 Still, all of these techniques rely on the elevation of the Schneiderian membrane without perforation. The literature shows consistent results in regards to implant survival (95%), choice of material (no difference) and rates of complications (2.5%). 8 Nevertheless, residual crest height of less than 5 mm was identified as a major factor for increased implant complications and loss. Another meta-analysis summarized findings regarding the osteotome technique without the use of bone grafting material and concluded, that 3 mm of height can be gained safely if there is a contraindication against the use of grafting material. 9 In summary, the crestal approach is a valuable alternative for a selected patient collective with sufficient remaining residual bone. On a side note, one article found that patients seem to prefer rotary instruments over the classic malleting of the osteotome technique. 10
When it comes to materials a multitude of different sources are available. Initially the material of choice was an autologous bone block harvested from the iliac crest, but donor site morbidity and limited availability have led to a search for alternatives. Numerous products are available that can be categorized according to their origin, namely Allografts, Xenografts, Alloplasts and Biologicals. A recent meta-analysis of histological studies has concluded that autologous bone still remains the gold standard by the means of histologic new bone formation. 11 Nonetheless, replacement materials show consistent and predictable long term results with no material being superior to another. 12 Probably the most surprising finding was that the mixture of demineralized bovine bone and autologous bone showed no better results than bovine bone alone. In summary, as by the current available knowledge choice of material is more depended on operator and patient preference as all materials show comparable results.
For the majority of dental patients, major surgeries are traumatizing and will be avoided if possible, therefore the search of alternatives to sinus lift procedures is ongoing. Namely short implants (≤8mm) have been in the discussion for many years. A recent systematic review showed that shorter implants seem to have comparable long-term survival to longer implants in grafted sites. 13 Morbidity, cost and surgical time are generally in favour of shorter implants and very limited evidence suggest that patients prefer shorter implants over grafting and longer implants. 14 Further research is needed though to substantiate these findings.
Sinus lift procedures are well researched and strong evidence suggests predictable long term outcome. Nonetheless, several complications and factors have been identified that must be part of the conversation with the patient, explicitly post-operative complications and morbidity. From an operator standpoint, every surgical technique comes with its own learning curve. Every operator that performs sinus lift procedures should be able to manage intraoperative complications such as membrane perforations. Therefore, a proficiency in all available approaches is recommended.
This article was prepared based on the presentation: “Sinus Floor Augmentation History, Techniques, Materials and Alternatives” that was presented at the Canadian Academy of Periodontology Annual Meeting in Calgary, May 2016 and won the Student Literature Review Competition Award. OH
Oral Health welcomes this original article.
1. Boyne, P.J. and R.A. James, Grafting of the maxillary sinus floor with autogenous marrow and bone. J Oral Surg, 1980. 38(8): p. 613-6.
2. Summers, R.B., A new concept in maxillary implant surgery: the osteotome technique. Compendium, 1994. 15(2): p. 152, 154-6, 158 passim; quiz 162.
3. Jensen, O.T., et al., Report of the Sinus Consensus Conference of 1996. Int J Oral Maxillofac Implants, 1998. 13 Suppl: p. 11-45.
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5. T, P., et al., An alternative maxillary sinus lift technique–sinu lift system. J Clin Diagn Res, 2015. 9(3): p. ZC33-7.
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11. Corbella, S., et al., Histomorphometric outcomes after lateral sinus floor elevation procedure: a systematic review of the literature and meta-analysis. Clin Oral Implants Res, 2015.
12. Schmitt, C.M., et al., Histological results after maxillary sinus augmentation with Straumann(R) BoneCeramic, Bio-Oss(R), Puros(R), and autologous bone. A randomized controlled clinical trial. Clin Oral Implants Res, 2013. 24(5): p. 576-85.
13. Esposito, M., P. Felice, and H.V. Worthington, Interventions for replacing missing teeth: augmentation procedures of the maxillary sinus. Cochrane Database Syst Rev, 2014(5): p. CD008397.
14. Thoma, D.S., et al., EAO Supplement Working Group 4–EAO CC 2015 Short implants versus sinus lifting with longer implants to restore the posterior maxilla: a systematic review. Clin Oral Implants Res, 2015. 26 Suppl 11: p. 154-69.