Rabbit maxillary sinus augmentation model with simultaneous implant placement: differential responses to the graft materials

Abstract

Purpose: This study was performed to establish an experimental rabbit model for single-stage maxillary sinus augmentation with simultaneous implant placement.

Methods: Twelve mature New Zealand white rabbits were used for the experiments. The rabbit maxillary sinuses were divided into 3 groups according to sinus augmentation materials: blood clot (BC), autogenous bone (AB), and bovine-derived hydroxyapatite (BHA). Small titanium implants were simultaneously placed in the animals during the sinus augmentation procedure. The rabbits were sacrificed 4 and 8 weeks after surgery and were observed histologically. Histomorphometric analyses using image analysis software were also performed to evaluate the parameters related to bone regeneration and implant-bone integration.

Results: The BC group showed an evident collapse of the sinus membrane and limited new bone formation around the original sinus floor at 4 and 8 weeks. In the AB group, the sinus membrane was well retained above the implant apex, and new bone formation was significant at both examination periods. The BHA group also showed retention of the elevated sinus membrane above the screw apex and evident new bone formation at both points in time. The total area of the mineral component (TMA) in the area of interest and the bone-to-implant contact did not show any significant differences among all the groups. In the AB group, the TMA had significantly decreased from 4 to 8 weeks.

Conclusions: Within the limits of this study, the rabbit sinus model showed satisfactory results in the comparison of different grafting conditions in single-stage sinus floor elevation with simultaneous implant placement. We found that the rabbit model was useful for maxillary sinus augmentation with simultaneous implant placement.

Keywords: Animal models; Bone substitutes; Dental implants; Guided tissue regeneration; Sinus floor augmentation.

Figure 1

An experimental site. The lateral window position and installed mini-implant (arrow) are shown in a schematic drawing (A). The sinus membrane, original sinus floor, and mini-implant (arrow) are seen in the photograph (B).

Figure 2

Area of interest (AOI). The AOI (A) was virtually selected in each specimen. B and C are the magnified view of AOI from A. The vertical dimension of AOI was set as the distance from the peak of 1st thread to the peak of 4th thread and the horizontal dimension was 1 thread pitch distance from the valley of the thread (B). In C, the area of newly formed bone and graft particles was yellow-highlighted for histomorphometric analysis. Basic fuchsin & methylene blue stain (A, ×20; B and C, ×40).

Figure 3

Photographs of 4 weeks (basic fuchsin & methylene blue stain, ×20). Yellow line indicates original sinus floor (OSF). (A) The BC group, the sinus membrane descended below the level of implant apex. New bone formation was restricted near OSF. (B) The AB group, the sinus membrane observed beside the implant apex. The grafted autogenous bone particles were found. (C) The BHA group, the sinus membrane was supported by BHA particles above the implant apex. New bone was deposited on BHA particles. The sinus membrane was indicated by arrowheads. BC group: blood clot filled group, AB group: autogenous bone filled group, BHA group: bovine-derived hydroxyapatitie filled group, NB: newly formed bone.

Figure 4

Photographs of 8 weeks (basic fuchsin & methylene blue stain, ×20). Yellow line indicates original sinus floor (OSF). (A) The BC group, the sinus membrane descended below the implant apex. (B) The AB group, the sinus membrane retained over the implant apex. Note the newly formed bone and central marrow spaces. (C) The BHA group, the sinus membrane was supported by BHA particles and retained above the screw apex. New bone was found between BHA particles. The sinus membrane was indicated by arrowheads. BC group: blood clot filled group, AB group: autogenous bone filled group, BHA group: bovine-derived hydroxyapatite filled group, NB: newly formed bone, BHA: bovine-derived hydroxyapatite.