Indirect sinus lift without bone graft material: Systematic review and meta-analysis

A systematic literature review and a meta-analysis of indirect sinus lift without the use of bone graft material was performed. A PubMed search was made from January 2005 to January 2012 with keywords: “sinus lift”, “osteotome”, “graft” and “maxillary sinus elevation”. The inclusion criteria were: maxillary sinus lift technique with osteotomes with a minimum follow-up period of 5 months after surgery without bone graft material. 11 articles were included. The mean gain in residual crestal bone height after maxillary sinus lift without bone graft material was 3,43 mm ± 0,09 (2,5 mm – 4,4 mm). The survival rate ranged from 94% to 100%. Placement of implants with sinus lift without bone graft material, is a valid surgical technique to gain residual crestal height and placed implants in an atrophic posterior maxillary with a crestal height from 5 to 9 mm. Key words:Sinus lift, osteotome, graft, maxillary sinus elevation.


Introduction
An important requirement for the correct placement of the implant is the presence of an adequate quantity and quality of residual bone (1). In 1994 Summers introduced the sinus lift technique with the use of osteotomes combined with graft material around the implant. This technique is a well-validated surgical option for situations with limited residual bone height; ≥ to 5-6 mm (2)(3)(4). The survival rate of implants placed simulta-neously with indirect sinus lift with bone graft material ranges between 93.5% and 100% (5)(6). The bone graft material allows to keep the volume of the sinus membrane after performing indirect elevation (7). The choice of material has been controversial for years to authors. Recently, several studies have reported favorable results when performing indirect sinus lifts without the use of any bone graft (7)(8)(9)(10)(11). The authors agree that graft material is not necessary to promote osseoin-tegration and maintain optimal bone volume around the implant, while the absence of graft reduces the risk of infections (12). The aim of this study was to systematically review the literature regarding the treatment outcome of indirect sinus lift without graft material according to bone height gained after placement of dental implants.

Material and Methods
A systematic search was conducted in the PubMed database for articles published between January 2005 and January 2012 on indirect sinus lift without the use of bone graft material. The following keywords individually or in combination were used: "sinus augmentation" OR "sinus elevation" OR "sinus lift" AND "indirect" OR "transcrestal". Titles and abstracts were reviewed to identify relevant studies.  (8,9,(13)(14)(15)(16)(17)(18)(19)(20). Articles reported by the same research group on the same sample of patients at different follow-up times were grouped; data with the longest follow-up were used for the statistical analysis. Three articles by Nedir et al. (9,13,14) and 2 by Fermergard et al. (15,16) were grouped.
-Statistical analysis A meta-analysis was performed to estimate the overall gain to the maxillary sinus, but it could not be performed for implant survival due to the lack of homogeneity in the follow-up time between studies. The estimate was based on the average weighted by the inverse of the variance, using a confidence interval of 95%. The significance level used in the analysis was 5% (α = 0.05).

Results
The 8 included studies grouped a total of 461 implants in 278 patients.
-Sinus gain Eight of the reviewed articles (8,9,(13)(14)(15)(16)(17)(18) involving 5 different patient samples reported sinus height gained after indirect elevation ( Table 2). The lowest sinus height gained was reported by the three studies on the same patient sample (9,17,18) with 2.5 mm; the greatest height gain was 4.4 mm and it was reported by Fermergard et al. in 2 articles on the same sample (15,16). Nedir et al. (9,13,14) measured the sinus height gained 1, 3 and 5 years after performing indirect sinus lift without graft, In all studies, the gain to the maxillary sinus was significantly non-zero (p <0.001). The mean overall gain calculated for all studies was 3.43 mm, with a standard error of 0.095 and a confidence interval of 95% (3.24 to 3.62).
-Survival rate of implants The survival rate of the implants was studied in all the 12 articles and ranged from 94% to 100%. The lowest survival rates were reported by two studies: Gabbert et al. (19) reported six failures out of 92 implants placed (implant survival rate of 93.5%), all caused by a lack of osseointegration during the first 6 months. Fermergard et al. (15) obtained a survival rate of 94% after a follow up of three years. Some of the articles reviewed, reported the survival rate of the implants and the mean residual bone height, which allowed to study implant survival depending on the residual bone height (8)(9)(10)(11)(13)(14)(15)(16)20). Nedir et al. (9,13,14) recorded a survival rate of 100% after 1, 3 and 5 years, with a residual average height of 5.4 mm. Senyilmaz et al. (11) obtained a survival rate of 100% at 2 years for residual bone heights ranging between 5 and 10 mm. Fermergard et al. (15) reported two failures (survival rate 96%) with a residual bone of 6.3 ± 0.3 mm. After a period of three years, the same authors (16)

Conclusions
The limited evidence available suggests that indirect sinus lift without the use of bone graft material could be a valid technique to treat with implants atrophic posterior maxillae with residual heights between 5 and 9 mm. The reviewed studies reported a mean bone height gain of 3.43 ± 0.09 mm and implant survival rates ranging between 93.5% and 100%. However, more studies, with bigger samples, providing controlled groups treated with bone graft material and involving evaluation with cone beam computed tomographic scans performed at different timepoints are necessary.