The present study aimed to conduct a systematic review and meta-analysis on the effectiveness of maxillary sinus floor elevation and immediate implant installation without the use of grafting material. An electronic search without date or language restriction was performed in PubMed/MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, Embase, and the grey literature, to May 2016. Eligibility criteria encompassed prospective and retrospective cohort studies, controlled clinical trials, and randomized clinical trials. The search and selection process yielded 18 studies, published between 2005 and 2016. A meta-analysis was conducted only for experimental studies comparing sinus floor elevation with and without grafting material; results were expressed as the standardized mean difference (SMD) or risk ratio (RR) with the 95% confidence interval (CI). An average gain in bone height of 4.7 mm over an average 39.4 month period was observed in the sinus elevated without grafting material. Regarding implants, there was a cumulative average survival rate of 97%. On meta-analysis, bone gain ( P = 0.98) and implant survival ( P = 0.13) did not differ significantly between sinuses lifted with or without grafting material, with a SMD of 0.01 (95% CI −0.42 to 0.44) and with a RR of 0.55 (95% CI 0.26 to 1.19), respectively.
The use of osseointegrated implants is currently an efficient and reliable method for the short- and long-term treatment of patients affected by partial or total edentulism. The rate of success and predictability of implant treatment depends on several factors, one of the most important being the quantity of bone. In particular, the posterior maxilla has always been a high-risk area for rehabilitation with implant-supported fixed prostheses due to atrophic alveolar ridges and/or a highly pneumatized maxillary sinus, conditions that imply a limited amount of residual bone. Therefore, in order to obtain the minimum height required for dental implant placement, techniques such as the sinus lift associated with grafts are performed routinely.
Several randomized clinical trials (RCTs) have evaluated the effectiveness of lifting the maxillary sinuses with or without the use of grafting material, through either the lateral bone window or osteotome (crestal approach) surgical technique. Although these studies have reported favourable outcomes in both cases, the need to use bone graft material in sinus lifting procedures remains controversial.
The first report of spontaneous vertical bone formation within the maxillary sinus, which occurred after the removal of a cyst, was published by Lundgren et al. in 2003; this demonstrated the osteogenic potential of the clot within the sinus. This study encouraged additional research, in which it was observed that bone neoformation and implant osseointegration after sinus lifting without grafting material was possible.
The clot presents advantages over grafting materials, one such advantage being the presence of growth factors and bone morphogenetic proteins that are expressed and activated upon tissue injury. Furthermore, the Schneiderian membrane contains osteoprogenitor cells that can also aid in the bone regeneration process. When grafting material is not used, the immediate placement of dental implants is essential in order to provide a framework (support) for the sinus membrane, allowing room for clot stabilization. Moreover, the contact between the clot and the titanium surface generates thrombin, which contributes to osteoblast activation, enhancing the effects of bone growth. The potential benefits of the non-use of graft materials include a shorter treatment time, absence of remaining graft particles, a lower rate of complications, and lower cost of treatment.
Thus, the aim of the present study was to evaluate the effectiveness of sinus floor elevation with immediate implant placement without the use of grafting material via a systematic review and meta-analysis.
Materials and methods
The protocol for this review was based primarily on the PRISMA-P statement ; the review has been registered in PROSPERO (number CDR42016042353). The methodology of this review followed the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions . The PRISMA guidelines and AMSTAR checklists were followed in order to increase the quality and transparency of the search. Clinical questions were separated and organized using the PICOS strategy (population, intervention, comparisons, outcomes, study design).
The focused question was: What is the effectiveness of maxillary sinus floor elevation with simultaneous implant placement without the use of grafting material?
The primary outcome variable was the amount of bone height gained after maxillary sinus lifting without the use of grafting material and with the simultaneous placement of implants. The secondary outcome variables were the implant survival rate and the occurrence of complications during the follow-up period.
An electronic search without date or language restriction was performed in the PubMed/MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, and Embase databases, to May 2016. Furthermore, a specific electronic search was performed in the following periodical journals: Journal of Periodontology , Journal of Clinical Periodontology , International Journal of Periodontics and Restorative Dentistry , Clinical Oral Implants Research , Clinical Implant Dentistry and Related Research , International Journal of Oral and Maxillofacial Implants , International Journal of Oral and Maxillofacial Surgery , and Implant Dentistry . Unpublished studies (grey literature) were identified through a search of the Grey Literature Report and OpenGrey databases. Searches were also conducted in the ClinicalTrials.gov database and in the reference sections of the studies included (cross-referencing). The search strategy for all databases and the PICOS tool can be viewed in Table 1 .