Maxillary sinus floor augmentation using a beta-tricalcium phosphate (Cerasorb) alone compared to autogenous bone grafts.

PURPOSE: A prospective human clinical study was conducted to determine the clinical and histologic bone formation ability of 2 graft materials, a beta-tricalcium phosphate (Cerasorb; Curasan, Kleinostheim, Germany) and autogenous chin bone, in maxillary sinus floor elevation surgery. MATERIALS AND METHODS: Ten healthy patients underwent a bilateral (n = 6) or unilateral (n = 4) maxillary sinus floor elevation procedure under local anesthesia. In each case, residual posterior maxillary bone height was between 4 and 8 mm. In cases of bilateral sinus floor elevation, the original bone was augmented with a split-mouth design with 100% beta-tricalcium phosphate on the test side and 100% chin bone on the contralateral control side. The unilateral cases were augmented with 100% beta-tricalcium phosphate. After a healing period of 6 months, ITI full body screw-type implants (Straumann, Waldenburg, Switzerland) were placed. At the time of implant surgery, biopsy samples were removed with a 3.5-mm trephine drill. RESULTS: Sixteen sinus floor elevations were performed. Forty-one implants were placed, 26 on the test side and 15 on the control side. The clinical characteristics at the time of implantation differed, especially regarding clinical appearance and drilling resistance. The increase in height was examined radiographically prior to implantation and was found to be sufficient in all cases. After a mean of nearly 1 year of follow-up, no implant losses or failures had occurred. DISCUSSION: The promising clinical results of the present study and the lack of implant failures are probably mainly the result of requiring an original bone height of at least 4 mm at the implant location. CONCLUSION: Although autogenous bone grafting is still the gold standard, according to the clinical results, the preimplantation sinus floor elevation procedure used, which involved a limited volume of beta-tricalcium phosphate, appeared to be a clinically reliable procedure in this patient population.

Localisation of osteogenic and osteoclastic cells in porous beta-tricalcium phosphate particles used for human maxillary sinus floor elevation.

We and others have shown earlier that porous beta-tricalcium phosphate (TCP) (Cerasorb) can be used in patients to augment the maxillary sinus floor prior to placement of oral dental implants. To better understand the transformation of TCP particles into bone tissue, we analyse here the appearance of cells with osteogenic or osteoclastic potential in relation to these particles. In biopsies taken at 6 months after sinus floor augmentation we observed bone growth into the TCP particles but also replacement by soft connective tissue. To identify possible osteoprogenitor cells in this tissue, histological sections were immunostained with an antibody to Runx2/Cbfa1, an essential and early transcription factor for osteoblast differentiation. The osteogenic potential of cells was further confirmed by immunostaining for bone sialoprotein (BSP) and osteopontin (OPN). Other sections were stained for Tartrate Resistant Acid Phosphatase (TRAP) activity to identify cells with osteoclastic capacity. Runx2/Cbfa1 positive connective tissue cells were found in abundance throughout and around the TCP particles, even at a distance of several millimetres from the maxillary bone surface. About 95% of the cells found within TCP particles stained positive for Runx2/Cbfa1. Fewer cells stained positive for BSP and OPN, suggesting more mature osteoblastic properties. Mono- and binucleate TRAP-positive cells, but no multinucleate TRAP-positive osteoclasts, were found in the soft tissue infiltrating the TCP and at the surface of the TCP particles. Both the Runx2/Cbfa1 positive and the TRAP-positive cells decreased apically with increasing vertical distance from the maxillary bone surface. This data suggests that the TCP particles attract osteoprogenitor cells that migrate into the interconnecting micropores of the bone substitute material by 6 months. The lack of large multinucleate TRAP positive cells suggests that resorption of the TCP material by osteoclasts plays only a minor role in its replacement by bone. Chemical dissolution, possibly favoured by a high cell metabolism in the particles, seems the predominant cause of TCP degradation. The abundance of Runx2/Cbfa1 positive cells would indicate that with a greater time of healing there will be further bone deposition into these particles.

Histomorphometry of human sinus floor augmentation using a porous beta-tricalcium phosphate: a prospective study.

Tricalcium phosphate (TCP) has been historically a well-accepted material for bone augmentation. We examined the use of a porous beta-TCP (100%) in a split mouth model for sinus floor augmentation. Five patients were treated bilaterally, receiving 1-2 mm-sized beta-TCP particles (Cerasorb) on one side (test side) and autologous chin bone particles on the other (control) side. Four other patients were treated with a unilateral sinus floor augmentation using 100% beta-TCP (no controls). Biopsies of the augmented sites were taken at 6 months. Histomorphometry measurements were carried out in order to quantify bone augmentation at test and control sides. The average bone volume (BV) formed in the augmented sinus at the control side was 41% (32-56%) and 17% (9-27%) in the test side when all nine patients were included (statistically significant, P=0.04). When only the five bilateral patients were included, mean BV of the test side was 19% (13-27%), which was also significantly different from the control side (P=0.009). Osteoid formation tended to be higher in the test side biopsies (1.3%) than in the controls (0.3%) (marginally significant, P=0.1), indicating ongoing bone formation in the TCP material. The amount of lamellar bone at the test side was less than half the amount in the control side, indicating that remodelling had only recently started in the TCP-augmented side. The resorption surface, however, did not differ significantly between the two sides. These histological results indicate that Cerasorb is an acceptable bone substitute material for augmentation of the maxillary sinus. Due to the osteoconductive, but not osteoinductive properties of this material, the rate of bone formation is somewhat delayed in comparison to autologous bone.

Fate of monocortical bone blocks grafted in the human maxilla: a histological and histomorphometric study.

Local bone defects in the anterior maxilla are commonly grafted with monocortical blocks of autologous bone in order to restore the defect site prior to the placement of dental implants. Increasing evidence suggests that osteocytes are involved in the control of bone remodelling and thus may be important for optimalisation of bone structure around implants, and thus for implant osseointegration. However, it is not well known whether osteocytes will survive when bone blocks are grafted into defects. We grafted 19 patients with monocortical bone blocks derived from the symphysis, to the defect site in the maxillary alveolar process. The bone grafts were left to heal for times varying from 2.5 to 7 months. During implant installation, bone biopsies were removed using a trephine burr, and processed for hard tissue histology. Bone histology and histomorphometry were then carried out in order to gain insight into the density, viability and remodelling of the graft. Clinically, all the bone grafts were successful, with no implant failures, and little resorption was seen. Histologically, bone volume expressed as percentage of tissue volume at the implant site varied from 27% to 57% with an overall average of 41%. Bone fields with empty osteocyte lacunae were observed and measured. The amount of this so-called nonvital bone (NVB) varied between 1% and 34% of the total tissue volume. The amount of NVB decreased significantly with the time of healing. The data suggest that the majority of the osteocytes of the monocortical bone do not survive grafting. The results indicate that the NVB is progressively remodelled into new vital bone 7 months after grafting.