Dennis G. Smiler (DDS, MScD)
Private practice, Encino, California. USA.

The sinus lift operation continues to be one of the most successful graft procedures in the surgeon’s armamentarium. Loss of posterior teeth with subsequent atrophy of the alveolus and increased pneumatization of the sinus results in the decrease of available bone for implant placement. The surgical procedure to elevate the sinus membrane with simultaneous grafting can produce sufficient bone for the placement of endosseous implants. A 39-year-old woman presented for implant consultation. The evaluation revealed a severely resorbed maxilla secondary to missing posterior teeth on both the left and right. The amount of bone between the sinus and the crest of the bone ridge on both the upper right and left side was radiographically shown to be very thin (< 4 mm) with loss of both height and volume. The patient was treatment planned for bilateral sinus lift surgeries.

SURGICAL PROCEDURES.

A crestal incision was made from tuberosity to canine fossa with a vertical relaxing incision in the area of the canine fossa. The mucoperiosteal flap was reflected, exposing the malar buttress region of the infratemporal fossa and the area of the canine fossa. A No. 8 round bur was used to create a quadrilateral window on the outer maxillary wall (Fig. 1). The osteotomy exposed the Schneiderian membrane. The membrane was elevated with the lateral wall in a superior position. At the superior osteotomy site, a molt curette was inserted to elevate the membrane 5 mm higher than the superior bone cut (Fig. 2). The procedure was exactly the same on the contralateral side. The left sinus lift surgical site was grafted with a mixture of 60% by volume anorganic bovine material (ABM) (OsteoGraf/N-300, CeraMed Dental, LLC, Lakewood, CO) and 40% by volume decalcified freezedried bone allograft (DFDBA) (Allo- Gro, CeraMed Dental, LLC) (Fig. 3). The right sinus lift site was grafted with a 60% by volume ABM/P-15 (PepGen P-15, CeraMed Dental, LLC) and 40% by volume DFDBA (AlloGro, CaraMed Dental, LLC) (Fig. 4). Both sides were covered with a BioMend (Sulzer Calcitek, Carlsbad, CA) resorbable collagen membrane (Fig. 5).

Fig. 1. A, quadrilateral windows left;
B, quadrilateral windows right.



Fig. 2. Elevation of Schneiderian membrane.



Fig. 3. Graft placement (OsteoGraf/N-300, AlloGro).



Fig. 4. Graft placement (PepGen P-15, AlloGro).



Fig. 5. BioMend (Sulzer Dental, Inc., Carlsbad, CA) membrane positioned.

Histological Bone Analysis.
At four months postgraft, the patient returned to the office for surgical placement of endosseous implants. Before implant placement, 3-mm core biopsies were taken in the maxillary right and left first molar regions with a trephine drill. The low power (magnification, 32.5) histological sections dramatically show the effect of the P-15 upon bone formation. The ABM shows trabeculae with new bone formation in contact with the particulate ABM. ABM/P-15 shows greater new bone contact with the particulate (Fig. 6) Higher magnification (310) shows new bone on the ABM surface and bridging between the particulate ABM. The ABM/P-15 again shows a very dense pattern of bone and ABM particulate (Fig. 7). Histomorphometric analysis compared the volume of vital bone in both the ABM and ABM/P-15. The analysis of both grafted sites revealed a high volume of vital bone in the ABM/P-15/DFDBA side. ABM/P-15 yields 45% vital bone compared with the 13% vital bone on the ABM in the absence of P-15 (Table 1).

Fig. 6. A, histology: trabeculae with new bone formation in contact with particulate ABM (32.5);
B, histology: ABM/P-15 shows greater new bone contact with the particulate (32.5).



Fig. 7. A, histology: a higher magnification shows new bone on the ABM surface (310);
B, histology: the ABM/P-15 shows a very dense pattern of bone and ABM particulate (310).



Table 1. Histmorphometric analysis.

DISCUSSION.
It has long been appreciated that accelerated healing time with corresponding greater graft quality would affect implantology. Most recently, the time factor has been addressed with the introduction of an anorganic bovine mineral impregnated with a synthetic, 15 amino acid sequence representing the cell-binding domain of Type-I collagen (P-15). This tissue engineered matrix is designed to enhance cell attachment and provide an optimal matrix for differentiation of cells into osteoblasts. The increase in the quality and quantity of bone associated with the P-15 graft suggests that re-entry into a grafted sinus may be possible in a reduced time frame to accelerate the insertion of implants.

References.

Tatum H Jr. Maxillary and sinus implant reconstruction. Dent Clin North Am. 1986; 30:207-229.
Smiler DG. The sinus lift graft: Basic technique and variations. Pract Periodontics Asthet Dent. 1997; 9:885-893.
Smiler DF, Holmes RE. Sinus lift procedure using porous hydroxylapatite: A preliminary clinical report. J Oral Implantol. 1987; 13:239-253.
Smiler DG, Johnson PW, Lozada JL, et al. Sinus lift grafts and endosseous implants. Treatment of the atrophic posterior maxilla. Dent Clin North Am. 1992; 36:151-186.
Froum SJ, Tarnow DP, Wallace SS, et al. Sinus floor elevation using anorganic bovine bone matrix (OsteoGraf/N) with and without autogenous bone: A clinical, histologic, radiographic, and histomorphometric analysis-Part 2 of an ongoing prospective study. Periodontics & Restorative Dentistry. 1998; 18:528-543.