Dimensional topography of the canine frontal sinus as an experimental model

Abstract

Sinus floor elevation is implemented widely to overcome unfavorable anatomical conditions on which standard length implants could not be placed. There have been maxillary sinus models in various animals to evaluate the efficacy of surgical interventions. Dogs are widely used as experimental subjects. However, the canine maxillary sinus is difficult to be approached and too small to be manipulated for dental implant placement. The dog frontal sinus may represent an alternative candidate for surgical interventions pertaining to dental implants; its topographical resemblance to the maxillary sinus renders it a potentially favorable experimental environment. The aim of this study was thus to elucidate the anatomical configuration of the canine frontal sinus (e.g., its thickness at different locations) and histological characteristics, and to determine whether it could be a new canine experimental model for dental implant research.Twenty-four sides of canine frontal bones were harvested from 12 mongrel dogs. The specimens were scanned with a microcomputed tomography system. After three-dimensional reconstruction of the images, the distance from the nasion to the emerging point of the lateral frontal sinus was measured with the aid of Lucion software. The specimens were sectioned in a coronal plane from the emerging point of the lateral aspect of the canine frontal sinus, posteriorly at 1mm intervals, and named coronal sectioned image CS1 (the emerging point of the lateral frontal sinus) to CS16 (the 16th coronal section that was 16mm posterior to CS1). The thicknesses of the canine frontal sinus wall were measured at distances of 3, 6, 9, 12, and 15mm from the midsagittal plane in sections CS1 to CS16. In two of the specimens, the samples were sectioned at a thickness of 7㎛ and stained with hematoxylin and eosin.The mean distance from the nasion to the emerging point of the lateral frontal sinus was 16.0mm (range, 10.2~23.0mm). The emerging point of the lateral aspect of the canine frontal sinus differed significantly according to the location of the septa within the frontal sinus. The mean thicknesses at 3, 6, 9, 12,and 15mm lateral to the midsagittal plane were 2.3mm (range, 2.0~2.7mm), 2.7mm (range, 2.5~3.4mm), 3.2mm (range, 2.9~3.9mm), 3.8mm (range, 3.1~4.2mm), and 3.7mm (range, 3.2~4.0mm), respectively. There was a tendency toward a greater thickness on proceeding laterally from the midsagittal plane and on proceeding posteriorly from the nasion. The canine frontal sinus was lined with pseudostratified ciliated columnar epithelium comprising cilia and abundant single-layered cells in a manner suggestive of multiple cell layers comprising goblet cells.The thickest region was from the nasion at 7~8mm and 14~16mm posteriorly, and from the midsagittal plane 12mm laterally (range, 4.0~4.2mm), and from the nasion 6~8mm posteriorly and from the midsagittal plane 15mm laterally (4.0mm). The thinnest region was from the midsagittal plane 3mm laterally (range, 2.1~2.7mm). These data suggest that the canine frontal sinus is a suitable alternative to the canine maxillary sinus as a model for studying various sinus augmentation protocols.