Histopathological and Bacteriological Evaluation of the Maxillary Sinus after Sinus Lifting Procedure: An Experimental Study in a Rabbit Model

Abstract

BACKGROUND: Rabbits have been used for establishing a new animal experimental model. The rabbit experimental model of maxillary sinus augmentation was firstly introduced by Watanabe et al. They stated that the advantages of the rabbit model were low cost, ease of experimentation, and easy distinction of membrane perforation. After their introduction of this model, successful experiments using the rabbit sinus model were performed by others. However, the previous studies had mainly focused on the response of various graft materials in the sinus without implant placement.

AIM: This study aimed to assess the histopathological and bacteriological outcomes of sinus lifting procedure on the maxillary sinus in a rabbit model.

MATERIALS & METHODS: This experimental animal study was conducted on 42 rabbits. The rabbits are divided into three groups: Group I (n=14):  the operation was conducted in rabbits with intact sinus mucosa where the bone graft was placed under an intact sinus mucosal membrane, group II (n=14): the operation was conducted in rabbits with intentionally perforated sinus mucosa.  Where the bone graft material was placed under the sinus membrane and inside the sinus cavity after a swab was taken for bacteriological culture and group III (n=14): the same procedure was done as in group two, but after two weeks, removal of the graft material with another swab was taken for bacteriological culture to detect changes in the sinus bacterial flora.

RESULTS: In the current study at baseline evaluation 25% had Pasteurella multocida, 14.3% had staphylococcus aureus and 3.6% had streptococcus pneumonia. There was statistical insignificant difference in bacterial growth among the studied groups (p=0.707). As group II had higher growth (50%) than group III (35.7%) with insignificant difference. In group II, 28.6% had Pasteurella multocida, 14.3% had staphylococcus aureus and 7.1% had streptococcus pneumonia. Among group III, 21.4% had Pasteurella multocida and 14.3% had staphylococcus aureus. After two weeks, among group III, there was significant increase in bacterial growth from (35.7%) to (64.3%) with statistically significant difference (p=0.004). After 2 weeks, microbiological evaluation detected 2 cases with Streptococcus Pneumonia, one case with Escherichia coli and one case with pseudomonas aeruginosa. In the present study, regarding thinning and perforation of the Schneiderian membrane, we found that there were no thinning nor perforation of the Schneiderian membrane among group I, while 85% of group II and 20% in group III showed thinning and perforation of the Schneiderian membrane with statistically significant difference (p<0.001). Group I had intact mucosa, 90% new bone mineralization and 10% inflammatory infiltrate. In group II, mucosa showed Perforation with attempts for healing, absence of new bone mineralization and 75% showed inflammatory infiltrate. In group III, there was focal ulceration of mucosa, 35% new bone mineralization and 45% inflammatory infiltrate.

CONCLUSION: If the maxillary sinus lifting is performed on top of an undamaged Schneiderian membrane, it is a rather safe and effective treatment. Although a little inflammatory response is anticipated, our data clearly shows new bone growth. The graft material is exposed by Schneiderian membrane penetration within the sinus cavity, which may impede the deposition of new bone for the intended implant installation and cause inflammatory cell aggregation. In order to improve patient outcomes by increasing the predictability and safety of maxillary sinus

lifting operations, this research also emphasizes the need of multidisciplinary cooperation between the otolaryngologist and oral surgeon..