The aim of this study was to evaluate the effect of the use of deproteinized bovine bone as a filler material of critical-sized (diameter >=20 mm) bony defects derived from the excision of maxillary and mandibular cysts. 20 patients were considered.

Patients were randomly divided into 2 groups according to the type of treatment: the bone defect was filled with granules of deproteinized bovine bone (test); no filling material (control). Clinical parameters were recorded at 7 days, 1, 6 and 12 months after surgery. Radiological follow up consisted of an orthopantomograph and a CT scan taken at the baseline (pre-operatory) and 12 months after surgery.

In order to evaluate the difference in percentage of filling of the bone defect between the two groups, the pre-op and the 1-year radiolucent volumes were evaluated in the CT scans.

The healing of extensive alveolar bone defects secondary to cyst removal is not predictable. Residual voids of various entity may persist. Some Authors proposed the use of grafting materials to reconstitute the loss of hard tissue. The primary objective was to determine the efficacy of bone grafting.The secondary objectives were to evaluate the incidence rate of wound dehiscence, pus drainage, recurrence and other complications 7 and 30 days and 6 months after surgery. Recurrence at 12 months of healing was also evaluated. For all patients included, surgeries were performed in conscious sedation and local anesthesia.Full-thickness flap of the appropriate shape and dimensions were lifted, and the bone exposed. When necessary, osteotomy was done, in order to enucleate the cystic lesion. The residual bone cavity was filled with deproteinized bovine bone (test), or not filled with any graft material (control). The flap was finally repositioned and sutured in order to achieve primary closure.

In both test and control groups antibiotic therapy with amoxicillin tablets of 1 g every 12 hours for six days (alternatively, for allergic patients, clarithromycin 500 mg tablets twice daily were given) and proper analgesics were prescribed. Postoperatory physical, therapy was prescribed as well.

Radiological follow up consisted of an orthopantomography and a CT scan taken at 12 months after surgery.For bone volume evaluation, a computerized method was adopted to compare the pre-operatory and the 12 months post-operatory CT scan. The Digital Imaging and Communication in Medicine (DICOM) obtained files were transferred to a Mac Pro Quad 2.66- GHz work- station (Apple Corp., Cupertino, CA, USA) and analyzed using an open-source medical image processing software (OsiriX v. 5.8.5, Pixmeo Sarl, Bernex, Switzerland). The margin of the radiolucent areas of each CT slice was traced manually on each axial view, and the volume calculated by the software with the ROI (Region Of Interest) tool. Volumes in mm3 and 3D images were obtained for each pre-op and post-op ct scan, for every test and control patient. Each exam was evaluated by two assessors (GL and SR) who were trained in radiological diagnosis and measurement detection. The volumetric reduction of the cysts was calculated by subtracting the preoperatory from the post operatory volumes, both in test and control groups.

Inclusion Criteria:

• no smoking for at least 6 months;
• preoperative radiological diagnosis of radiolucent lesion of probable cystic origin;
• bone defect > 2 cm (diameter);
• ASA1;
• consent to the study inclusion.

Exclusion Criteria:

• subjects in need of treatment with a hemostatic material;
• active infection or inflammation in the treatment area;
• uncontrolled diabetes;
• bone diseases ( Paget's disease, patients undergoing bisphosphonate therapy, multiple myeloma, bone metastases);
• previous radiation therapy in the head and neck region;
• patients not able to take part to the follow-up program.