# Effectiveness of Collagen Membrane in the Treatment of Schneiderian Membrane Perforation
## 4 Discussion  
SMP is the most common complication to occur during sinus floor elevation procedures and must be managed to prevent loss of valuable bone graft and bone substitute materials [9]. Various treatments have been proposed for the repair of SMPs. CMs are widely used in the treatment of SMPs. Although fast-resorbing CMs are often used, they possess no rigidity and, as a result, may be not adequate for large membrane perforations [10; 11]. Nevertheless, small membrane repairs using fast-resorbing CMs have been well documented. A fast-resorbing CM is a soft, white, pliable, and nonfriable sponge that is often used in dental surgery. It can be the better choice for the repair of small-to-medium-sized SMPs (<10 mm) for controlling bleeding, stabilizing blood clots, as well as protecting the membrane while accelerating the healing process more predictably than slow-resorbing CMs [12]. As this current study shows, when there is an SMP, the bone graft could still be completed following the CM repair, and the implants could be placed in most of the patients without complications. There were no significant differences in acquired bone heights compared with patients without perforations at the various follow-up time points. Those differences that exist in bone heights at the postoperative time points can be assumed to be due to the fact that further mucosal elevation is more carefully performed when a perforation occurs during the sinus lifting procedure. Large perforations (>10 mm) are the most difficult and challenging to repair during sinus lift surgery. Suturing large SMPs can be difficult because of the limited access and the friability of the maxillary sinus membrane. Also, the membrane edges of the torn mucosa cannot be approximated in the case of large SMPs [11; 13]. Here, a slow-resorbing CM can be placed on the SMP in order to make a pouch [14]. This pouch is meant to surround and isolate the bone graft. However, such isolation  
Figure 5: Graph of Tables 3 and 4. * indicates a significant difference in comparison with variable values at \(p<0.016\). Significance was determined using two-way repeated-measures ANOVA. Significance for pairwise comparison was determined with the Bonferroni post hoc test. Data are presented as means \(\pm\) standard deviations. using a pouch might have an adverse effect on the neovascularization of the torn mucosa healing and graft incorporation. When the membrane perforation is large or cannot be controlled, stopping the procedure and reentering after 6-8 weeks to allow for the regeneration of the sinus membrane is one option [15]. The authors of this study have inserted CPs into cases with large maxillary sinus tears without additional bone graft in cases with large SMPs. There are other studies which have proposed that an isolated space created by the elevated membrane and a simultaneous protruding implant placement without insertion of any bone substitute resulted in new bone formation [16; 17; 18; 19]. A CP can therefore act as additional space-making material between the sinus membrane and sinus floor. In the present study, the authors could observe bone gain after CP repair in cases of large SMPs. However, this was only about 1 mm compared with the preoperative time point. This may be insufficient to allow implant placement with full bone coverage--in other words, impossible without a bone graft. Pathological conditions, which include the presence of sinusitis or inflammatory-induced membrane changes, might be potential risk factors for SMPs during sinus lift procedures [5]. Sometimes the authors have found that these unhealthy membranes are not perforated during the sinus lift procedure but they are weakened, thinned, or irritated. Such weakened membranes can potentially develop later perforations that can lead to bone graft failure after procedure. In order to avoid this, the authors have used CMs for reinforcement of weakened sinus membranes. The use of CMs may prove to be useful for protecting such potentially weakened sinus membranes.