The aim of the present study was to compare the healing of the augmented sinus in large animals, where the antrostomy was covered by a polylactic membrane or a repositioned bone plate, both secured with cyanoacrylate.

No statistically significant differences were found between test and control sites in the bone formation within the augmented space. This outcome is in agreement with a similar study in rabbits, in which sinus augmentation was performed bilaterally using a collagenated cortical cancellous bone [17]. In that study, the antrostomy at the control site was covered with a collagen membrane, while at the test site it was closed with the repositioned bony window. The healing was evaluated after 2, 4, and 8 weeks, and no differences were found at any of the periods assessed.

In the present study, different regions within the elevated area were evaluated. A statistically significant difference was found in the close-to-window region where the new bone was found at higher proportions at the repositioned sites compared with the polylactic membrane sites. This outcome could have limited clinical relevance since implants are positioned in the middle of the augmented area. In the study mentioned above [17], no differences were found in any of the regions examined, including in the close-to-window region. However, remaining defects within the antrostomy were seen at the collagen membrane sites. Similarly, in the present study, a high content of connective tissue was found in the antrostomy in the polylactic membrane group, while the repositioned bone plate protected the antrostomy from soft tissue ingrowth.

The results from the present study are not in complete agreement with those from the other experiments [16, 22, 23]. In an experiment in rabbits [22], sinus augmentation was performed bilaterally. At one site, the elevated volume was filled with DBBM and the antrostomy was covered with a collagen membrane. The other sinus was filled with a clot and the antrostomy closed, with the repositioned bony window secured with a screw. The healing was evaluated after 1, 2, 4, 6, and 8 weeks, and a higher content of the new bone was found at the repositioned sites compared with the collagen membrane sites. No evaluations of specific regions within the sinus were reported. However, it must be considered that no xenograft was placed at the repositioned bone window, so comparisons with the present study may not be suitable. However, in another experiment in rabbits [16], a DBBM graft similar to that used in the present study was placed to augment both sinuses. The antrostomies were covered with either the repositioned bone window or a collagen membrane, and healing was evaluated after 1, 2, 4, and 8 weeks. Statistically significant higher amounts of the new bone were found at the repositioned bone window groups compared with the polylactic membrane groups. In the present study, however, the only statistically significant difference was seen in the close-to-window region. Moreover, the bone window was found connected with bridges to the new bone formed from the central regions and to the edges of the antrostomy, in agreement with the abovementioned experiments [16, 17, 22].