Relative bone width of the edentulous maxillary ridge. Clinical implications of digital assessment in presurgical implant planning.

BACKGROUND: Healthy, well-structured mucosa may clinically disguise atrophic jawbone in preimplant diagnosis.

PURPOSE: To analyze bone width in relation to the complete ridge thickness comparing the anterior with the posterior edentulous maxilla.

MATERIALS AND METHODS: Data of 52 patients (mean age 62 ± 9 years) who were edentulous for at least 1 year and who received implant treatment were analyzed. Computed tomography (CT) scans were obtained and virtually analyzed in perpendicular sections of 12 maxillary positions (central and lateral incisors, canines, premolars, and first molars) using an implant planning software. Absolute thickness of complete jaw, bone, and mucosa were digitally measured at crestal and basal ridge levels allowing for relative bone width (B-rel) calculation.

RESULTS: Mean B-rel at crestal levels was lower than at basal levels (38.6% vs 51.5%, p < .001). Bone width increased significantly (p < .001) in the posterior maxilla at both levels, whereas the thickness of palatal and buccal mucosa was considerably stable. Mean basal B-rel ranged from 49% (6.2 ± 2.0 mm) at incisors to 59% (9.0 ± 2.3 mm) at first molars (p < .001). Mean proportion of regions showing B-rel < 50% were 43% at basal and 80% at crestal levels.

CONCLUSIONS: The osseous volume of a large edentulous ridge might be clinically overestimated in preimplant diagnosis, as the relative bone width was generally lower than 50%. Clinicians can use the present results of the virtual bone and mucosa measurements to have a better first estimation of the osseous proportion depending on the maxillary area. However, up to date implant therapy for the edentulous maxilla requires CT-based prosthetically driven implant planning and preferably combination with guided implant placement by transferring planning information to a surgical template.