Relevant anatomic and biomechanical studies for implant possibilities on the atrophic maxilla: critical appraisal and literature review.

PURPOSE The purpose of this review was to highlight anatomic and biomechanical aspects of atrophic maxillae for implant possibilities. MATERIALS AND METHODS A MEDLINE electronic search of the years 1966 to 2009 was conducted with the keywords "atrophic,""resorbed,""edentulous," and "maxilla." RESULTS Twenty papers presented the following findings: (1) previous use of a removable prosthesis is a risk factor for resorption, with flabby tissues related to the severity of resorption; (2) implants in the reconstructed maxilla (< or =5 mm) and supporting overdentures had a higher risk for bone loss based on the worse periimplant soft-tissue health observed; (3) bleeding on probing was found with pocket depths > or =5 mm in half of the zygomatic implants; (4) prevalence of bone septa is higher in atrophic maxillae, and changes on nasopalatine canal can reduce up to 44.4% of the full length of buccal bone plates; (5) female patients have less medullar bone quantity and connectivity than male patients; (6) transectioning of nutrient vessels is easier and accelerates resorption; (7) stress does not concentrate on maxillary sinus base cortical bone contiguous to trabecular bone; (8) splinted implants receive nine times less load than nonsplinted implants even under oblique loading; (9) implant stability quotient (ISQ) values for implants ranged between 60 and 65; (10) in vivo force transfer to implants is similar between fixed prostheses and overdentures; (11) inclined implants generate better biomechanical responses; (12) masticatory efficiency and bite forces improve in maxillectomized patients who receive obturators with milled bar attachments. CONCLUSION Sound implant-supported choices for an atrophic maxilla must be made with a thorough understanding of its anatomic and biomechanical factors.