Cirurgias de levantamento de seio maxilar com e sem membrana de colágeno sobre a janela externa: avaliação anatômica, histomorfométrica e microtomográfica

Abstract

The aim of this study was: a) to verify the histological, histomorphometric and microtomographic features of the regenerated tissue from maxillary sinus augmentation surgery, with and without the use of the collagen membrane on the external osteotomy window, and b) to observe if the incidence of Schneider membrane perforations might be related to the angulations of the anatomical areas of the maxillary sinus and the sinus membrane thickness. The study was a prospective, controlled, randomized, double blind study, in which 16 patients were selected and submitted to bilateral maxillary sinus surgery, in a split-mouth design. On one side of the maxillary sinus lift procedure, Bio-Oss®, biomaterial of bovine bone origin was used with Bio-Gide® collagen membrane on the external osteotomy window. On the contralateral side, only Bio-Oss® was used, without the presence of the membrane. In study 1, after a mean period of 8.5 months, the surgeries for implant installation were performed in a total of 12 patients of the sample. In this surgical phase, specimens of the regenerated tissue were collected and sent to the computerized microtomography (MicroCT) for histological and histomorphometric study. In study 2, the patients were submitted to a preoperative cone beam CT scan, always with the tomographic guide. Some measurements were made in the anatomical regions of the maxillary sinus corresponding to the posterior teeth of the tomographic guide, from the 1st pre-molar to the 2nd molar, bilaterally. These measurements included the angle between the lateral and medial walls of the maxillary sinus, the distances between these walls in 3 different levels of height and the thickness of Schneider's membrane. During the procedure of maxillary sinus survey, in the existence of a sinus membrane perforation, information such as the site and its extension were recorded. In the histomorphometric analysis, the mean percentages of neoformed bone were 43.9% and 40.8% in the groups with and without membrane, respectively. The corresponding values of the microtomographic analysis were 36.6% and 37.2% in the groups with and without membrane, respectively. There was no statistically significant difference between the test and control groups in the two methods. There was no statistically significant difference between the mean percentage of biomaterial remaining between the test and control groups. However, the mean percentage of neoformed bone was significantly higher and the mean percentage of remaining biomaterial was significantly lower in the histomorphometric analysis, as compared to the values obtained through microtomography. Perforation of the maxillary sinus occurred in 17.9% of the surgeries performed, where the Schneider's membrane was significantly thinner than the non-perforated sinuses. In conclusion, the additional use of collagen membranes in maxillary sinus surgery did not offer advantages in terms of bone formation. The main factor that contributed to the perforation of the maxillary sinuses was the thickness of the maxillary sinus membrane.