雖然上顎後牙區，在殘存牙嵴高度小於5mm時，用骨鑿做上顎實上提術併立即植牙的可預測性較低，但並非所有解剖上的構造都適合以上顎實側壁開窗進行增高術。本病例患者為44歲健康男性，齒位15，16缺牙，齒位16的殘存牙嵴高度達7mm，但與對咬牙之咬合間隙僅3mm：齒位15為一剛拔牙傷口，頰側及顎側骨缺損嚴重，齒槽底部至上顎竇底部約2mm。為獲得足夠的咬合間隙，在齒位16先進行骨修形後，殘存牙嵴高度約剩下3mm，但因上顎實解剖構造上兩顆牙之間有很大的落差，若由側壁開窗的方式，會有困難，所以以骨鑿做上顎實增高術，同時齒位15做骨嵴保存術。約六個月後於齒位15再做一次骨鑿式上顎實增高術，同時將15，16植體放入。當殘存牙嵴高度不足6mm時，有時會因為解剖構造上的受限，而不適合由側壁開窗做上顎竇增高術，此時以階段性骨鑿上顎增高術進行，仍可得到不錯的結果。

Although osteotome Sinus floor elevation with simultaneous implant placement in the cases of less than 5mm of residual bone height is less predictable than lateral window method, buy not all anatomic situations are suitable for lateral approach. Limitation of this case includes 5mm residual bone heiglt, insufficient interarch distance about 6mm, and a limited anatomic situation of sinus floor, that great difficulty of lateral window method was expected. In this case, crestal bone reduction was performed first to gain enough inter-arch space, then utilized staged osteotome technique, to augment the subantral alveolar bone height. After 6 months of healing, implantation was performed, and the primary stability was good. Definitive restoration was fabricated 3months later, and no significant bone loss was found. Conclusion: When there's not only insufficient residual bone height, but also anatomic limitation of implant site, the staged osteotome sinus floor elevation approach could be an alternative method.