the area involved. Because a bladevent occupies the bone for some distance, the simple clinical method of differentiation is not possible.

If the patient complains of pain in the area, radiographs must be used to detect excessive bone resorption, which always accompanies a failing bladevent. In addition, a failing bladevent will always be loose. Prior to implantation, the dentist should explain the situation in detail to the patient with a history of chronic or occasional sinusitis to avoid anxiety about the bladevent as a causative agent.

The Nasal Cavity

The maxillary and palatine bones separate the oral cavity from the nasal cavity, and provide a firm floor for the latter. The anterior, and major, portion of the floor is formed by the palatine process (1) of the maxillae, and the posterior by the horizontal process (2) of the palatine bones.

The nasal floor is smooth and concave, with that process toward the midline rising to join the process of its bilaterally paired opposite. This prominence (3) serves as a base for the cartilaginous septum (4) that divides the air passage into two fossae. The most anterior part of the prominence, the anterior spine (5), forms the cleft of the upside-down, roughly heart-shaped outline seen in radiographs as the piriform aperture.

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