Review question
This review, carried out by the Cochrane Oral Health Group, seeks to determine whether and when it is necessary to increase the thickness of the bone layer at the base of the natural sinus cavity (maxillary sinus) that lies above the upper jaw in order to successfully insert dental implants onto which artificial teeth will be anchored. Also, to find the most effective techniques for doing this.
Background
Missing teeth may cause problems with eating and speaking, and affect how someone looks. Traditionally they have been replaced by loose false teeth (dentures) or bridges fixed between other teeth. Dental implants offer an alternative way of replacing teeth. Implants look like screws; they are made from materials such as titanium, which can fuse with the bone they are placed in (osseointegration) offering a stable base for artificial teeth to be fixed to. However, there needs to be enough depth of bone to successfully insert the implants. Bone thickness towards the back of the upper jaw can sometimes be too thin because of the natural sinus cavity (maxillary sinus) that lies above it. The cavity can also sometimes become larger following tooth loss.
Where the bone is too thin, there are a number of techniques that are used to create a thicker layer of bone at the base of the sinus cavity which are generally known as 'sinus lift' procedures. These methods involve using either bone taken from the patient (autogenous bone) or other materials known as biomaterials, a combination of the two, or sometimes simply using a blood clot as a base for the body to naturally form additional bone.
An alternative to a sinus lift is to use, where possible, short implants (4 to 8.5 mm long).
Study characteristics
The evidence on which this review is based is correct as of 17 January 2014. Eighteen trials with 650 participants were included. Four of the trials, with a total of 102 participants, compared implant-supported prostheses using a sinus lift with prostheses on short implants (5 to 8.5 mm long) without sinus lift. The remaining 14 trials with a total of 548 participants compared different sinus lift techniques.
Key results
There is not enough evidence to show whether sinus lift techniques are more or less successful in reducing the number of failures of dental prostheses (artificial teeth) or dental implants when compared to simply using short implants, up to one year after loading.
However, there is limited evidence that there are fewer complications when short implants are used without surgical lifts. Complications include sinusitis, infection and bleeding, and when bone grafts are taken from the patient complications can also include nerve injury, problems with walking and infection.
Quality of the evidence
The quality of the evidence for whether or not to use a sinus lift procedure was moderate. The evidence for the 14 comparisons of different sinus lift procedures was based on a maximum of two comparisons for each comparison and was low.
There is moderate quality evidence which is insufficient to determine whether sinus lift procedures in bone with residual height between 4 and 9 mm are more or less successful than placing short implants (5 to 8.5 mm) in reducing prosthesis or implant failure up to one year after loading. However, there are more complications at sites treated with sinus lift procedures. Many trials compared different sinus lift procedures and none of these indicated that one procedure reduced prosthetic or implant failures when compared to the other. Based on low quality evidence, patients may prefer rotary instruments over hand malleting for crestal sinus lift.
Insufficient bone volume is a common problem encountered in the rehabilitation of the edentulous posterior maxillae with implant-supported prostheses. Bone volume is limited by the presence of the maxillary sinus together with loss of alveolar bone height. Sinus lift procedures increase bone volume by augmenting the sinus cavity with autogenous bone or commercially available biomaterials, or both. This is an update of a Cochrane review first published in 2010.
To assess the beneficial or harmful effects of bone augmentation compared to no augmentation when undertaking a sinus lift procedure. Secondly, to compare the benefits and harms of different maxillary sinus lift techniques for dental implant rehabilitation.
We searched the Cochrane Oral Health Group's Trials Register (to 17 January 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 12), MEDLINE via OVID (1946 to 17 January 2014) and EMBASE via OVID (1980 to 17 January 2014). There were no language or date restrictions on the searches of the electronic databases.
Randomised controlled trials (RCTs) of different techniques and materials for augmenting the maxillary sinus for rehabilitation with dental implants that report the outcome of implant success or failure at least to four months after initial loading.
Screening of eligible studies, assessment of the risk of bias of the trials, and data extraction were conducted independently and in duplicate. Authors were contacted for any missing information. Results were expressed using fixed-effect models as there were either less than four studies or we used Peto odds ratios (ORs) for dichotomous data when there were zero cells in either the treatment or control or both arms and the number of trials was small. The statistical unit of the analysis was the patient.
Eighteen RCTs out of 64 potentially eligible study reports met the inclusion criteria. They compared undertaking a sinus lift with not doing so, and the use of different sinus lift techniques. There were 650 patients providing data for the outcomes evaluated. Five studies were assessed as low risk of bias, 11 were assessed as high risk of bias, and in two the risk was unclear.
Sinus lift versus no sinus lift
Four trials of moderate quality (three trials at low and one at high risk of bias) with 102 participants evaluated short implants (5 to 8.5 mm long) as an alternative to sinus lift in bone with residual height between 4 and 9 mm. One year after loading there was insufficient evidence to claim differences between the two procedures for prosthesis failure (OR (Peto) 0.37, 95% confidence interval (CI) 0.05 to 2.68; three trials) or implant failure (OR (Peto) 0.44, 95% CI 0.10 to 1.99; four trials). There was however an increase in complications at treated sites when undertaking the sinus lift (OR (Peto) 4.77, 95% CI 1.79 to 12.71, P value = 0.002; four trials).
Different sinus lift techniques
Fourteen trials with 548 participants compared different sinus lift techniques. Only three comparisons included more than one trial (two trials for each). These were bone graft versus no bone graft, autogenous bone versus bone substitute, bone graft with or without platelet-rich plasma (PRP). There was insufficient evidence to claim a benefit for any of these techniques for the primary outcomes of prosthesis and implant failure. For the other reported outcomes, in a single study at high risk of bias, only bone gain was greater for the bone graft site than the site without a graft six months after augmentation, however this was not significant at 18 or 30 months.
The other comparisons with single studies were rotary versus piezosurgery to open a lateral sinus window, two different bone substitutes, use or not of a membrane to seal the lateral window, one- versus two-stage lateral sinus lift, two-stage granular bone versus one-stage autogenous bone blocks, and crestal versus lateral sinus lift; two trials compared three different crestal sinus lifting techniques: rotatory versus hand malleting (patients preferred rotatory instruments over hand malleting) and hand versus electric malleting. There was no evidence of a benefit for any sinus lift procedure compared to any other for the primary outcomes prosthesis or implant failure.