Implant-Guided Volumetric Analysis of Edentulous Maxillary Bone With Cone-Beam Computerized Tomography Scan. Maxillary Sinus Pneumatization Classification

The primary goal of this anatomic study was to measure the average bone volume of the edentulous maxilla with a cone-beam computerized tomography (CBCT) scan and to determine its suitability for implant treatment without additional bone grafting. The secondary goal of the study was to estimate the degree of sinus pneumatization (SP) in reviewed CBCT scans, assess the sinus-to-maxillary bone interrelationship in edentulism, and attempt to classify maxillary sinuses based on the degree of their pneumatization. This retrospective radiographic quantitative study consisted of the analysis of CBCT scans of 30 randomly selected maxillary edentulous patients who presented in 2008-2010 to the University of the Pacific, Arthur A. Dugoni School of Dentistry, for evaluation and treatment of their edentulism. A volume of edentulous maxillary bone mesial to the maxillary sinuses (intersinal region) that can be used for a full-arch implant treatment was evaluated based on specifically selected and clinically relevant measurement criteria. There were 30 CBCT scans of maxillary edentulous patients reviewed (9 men, 21 women) with a mean age of 67.3 years (range, 41 to 92 years). The total mean maxillary bone volume (MMBV) suitable for implantation was 4408.1 mm(3) and ranged from 1489.7 to 7263.1 mm(3). The MMBV in the study was higher than an assumed or hypothetical bone volume minimally suitable for 4-implant treatment as proposed by the authors for comparative purposes (3500 mm(3)). The degree of SP as seen on a CBCT scan (60 sinuses analyzed on panoramic images of 30 CBCT scans) had the following results in the study: SP0 (clear: not interfering with implant treatment in cases of high/small sinus), 2 sinuses or 3.3%; SP1 (mild sinus enlargement), 29 sinuses or 48.3%; SP2 (moderate SP), 16 sinuses or 26.7%; SP3 (severe SP), 9 sinuses or 15.0%; and SP4 (extreme), 4 sinuses or 6.7%. Most analyzed maxillary sinuses (47 of 60, or 78.3%) were in the clear, mild, or moderate categories of SP (SP0, SP1, and SP2), which have a sufficient amount of maxillary bone beneath the maxillary sinuses to allow a full-arch implant treatment. An inverse correlation between SP and MMBV was observed. Although many other clinical criteria are important (bone quality, alveolar crest anatomy, etc), the results of this CBCT radiographic study indicate that in many maxillary edentulous cases, the existing bone quantity (volume) can be sufficient for a full-arch maxillary implant treatment with at least 4 implants without the additional trauma or expense of bone grafts and sinus lifts. A variety of implant treatment options can be proposed based on maxillary bone availability and bone-to-sinus interrelationship. It appears that with age and edentulism, the amount of available maxillary bone is steadily decreasing.