Discussion
Most frequent complications of lateral window approach are perforations
of the Schneiderian membrane and bleeding. Others include the
obstruction of the antral meatal ostium complex, dislocation of the
implant into the sinus cavity, perforations in the buccal flap, and less
frequently, injury to the infra-orbital nerve(Sindel et al. 2018). The
main challenge of the crestal sinus procedure is the uncertainty of a
possible perforation of the Schneiderian membrane because the sinus
lifting procedure is performed blindly due to the impossibility to
visualize the sinus floor(Sindel et al. 2018). The incidence of membrane
perforations in crestal sinus lift has been reported to range between
4-25 percent, while such complication has been described in 25-44
percent of external sinus lifting cases making the crestal approach a
less risk for perforation (Sindel et al. 2018). The benefit from crestal
approach is that it can achieve gain in bone height comparable with the
lateral window approach, while maintaining the benefits of the less
invasive trans alveolar approach(Mazor et al.2013). Great advantages are
reduced chair-side times and minimal graft wastage. In this case review,
a minimal invasive crestal approach for sinus augmentation was conceived
using a new generation putty-graft. The putty is easy to use and because
of its consistency and continuous flow of the biomaterial it results in
a gradual and continuous elevation of the minimizing the chance of
damaging or perforating the Schneiderian membrane(Kotsakis & Mazor 2015). The presented cases show a significant bone formation around the
implants radiographically. Lifting the Schneiderian membrane between 2.4
– 7.3 mm. It has been reported that a gain of up to 10 mm in alveolar
height can be achieved using several modifications of transcrestal
approach, it has commonly been assumed that the Schneiderian membrane
can be safely elevated for 5 mm through the internal sinus
lifting(Sindel et al.2018). The lift stays stable for the first three
months, but then after time the volume decreases due to pneumatization
of the sinus. This is consistent with other studies. The pneumatization
of the maxiallary sinus stabilizes after the initial three years
shrinkage(Qian & Mo 2020)