A year later, we requested cone beam computed tomography for both posterior maxilla sites, and we found incomplete bone growth in the sinus. On the right side, bone growth had occurred only distal to the desired implant site, and there was an ovoid extension of sinus into the area planned for implant placement (Fig. 4). On the left side, a finger-like extension of sinus had developed between grafted bone and the former inferior medial wall of the sinus (Fig. 5). After explanation of findings, treatment alternatives, and risks and benefits of proposed treatments, the patient agreed on continuing with additional bone grafting.

For the right side, we decided to augment the area of insufficient bone using a balloon dilation technique through a subantral approach since the area of the missing bone was nearly spherical and centered at the no. 3 site. We also decided to place an implant simultaneously since primary stability seemed likely with the consistent thickness of 5 mm available bone at the no. 3 site, consistent with the recommendation by Pjetursson and Lang [19]. We created sinus access in a similar fashion as developed by Tatum in the 1970s and described by Misch [20] and performed sinus augmentation with a balloon technique as described for lateral window augmentation by Muronoi et al. [6]. (See Fig. 6 for the actual procedure, Fig. 7 for a diagram.) For this surgery, we created a mucoperiosteal flap with buccal releases for improved access (Fig. 6a, b) and created an osteotomy using osteotomy drills (Fig. 6c; Zimmer implant surgical kit, Zimmer, Carlsbad, CA, USA). Since there was sufficient ridge width and the bone was hard, we opted not to use Summer’s technique [21] but used drills to take the osteotomy to its final width that was slightly undersized for a 4.7-mm implant, but wide enough to allow insertion of a balloon dilator (straight model, Osseous Technologies of America, Hamburg, NY, USA). Drilling of the osteotomy stopped short 1 mm of the sinus floor. Prior to balloon dilation, we mobilized the Schneiderian membrane by gently infracturing small segments of the osteotomy floor using thin flat-ended osteotomes (ACE Surgical Supply, Brockton, MA, USA). For this, we started in the center of the osteotomy, advanced the depth of the infracture by 1 mm with a mallet and worked in a spiral fashion to the outer limits of the osteotomy floor and apical most 2 mm of the osteotomy wall. We then used a larger flat osteotome to advance the entire floor of the osteotomy by another millimeter, which resulted in a rubber-like mobility of the osteotomy floors. We verified the integrity of the membrane by gentle probing with a WHO probe and inserted the balloon dilator (Fig. 6d–g). We then slowly inflated the balloon dilator with 1 ml of saline, verified integrity of the membrane again, placed two sheets of 1 cm × 1 cm × 1.5 resorbable collagen tape, followed by 0.5 ml allograft and a 4.7 × 10 mm rootform implant (Fig. 6h–j; Tapered Screw-Vent TSVWB10, Zimmer, Carlsbad, CA, USA), which achieved good primary stability in excess of 30 Ncm. We placed a cover screw, replaced the flap, and sutured it with a continuous chromic gut 4-0 suture (Fig. 6k). Postoperative radiographs verified implant placement and showed good confinement of graft material around the implant (Fig. 6l). Healing was uneventful with only mild short-lived postoperative pain for a few days, and implant uncovery 12 months later revealed a firmly embedded implant.