Influence of a collagen membrane and recombinant platelet-derived growth factor on vertical bone augmentation in implant-fixed deproteinized bovine bone--animal pilot study.

OBJECTIVES: Combinations of bone substitute block materials with membrane techniques as well as with growth factors are possible options to enhance the prognosis of vertical bone augmentation. Therefore, the aim of the pilot study was to compare the influence of a collagen membrane and a signal protein (rhPDGF-BB) on vertical bone augmentation with a stable fixed block material (deproteinized bovine bone [DBB]). MATERIALS AND METHODS: In 12 rabbits, a DBB-block was implant-fixed on the tibia in a split-leg-design. Included were: DBB only (control), DBB + collagen membrane (test), DBB + rhPDGF-BB (test) and DBB + rhPDGF-BB + collagen membrane (test). 24 samples were examined after 3 (n = 12) and 6 weeks (n = 12). Calculated parameters were new bone area (NBA;%), new vertical bone height (VBH; mm). Due to the pilot character of this study, single values are shown descriptively only. RESULTS: After 3 weeks, there were constant higher NBA values in the rhPDGF-BB-group without membrane (NBA (%) DBB: 30/16/4; DBB + membrane: 25/17/7, DBB + rhPDGF-BB: 40/33/34, DBB + rhPDGF-BB + membrane: 0/30/16; VBH (mm) DBB: 1.2/1.2/1, DBB + membrane: 0.7/0.9/1, DBB + rhPDGF-BB: 0.7/0.9/1, DBB + rhPDGF-BB + membrane: 0/1.1/1). After 6 weeks, both membrane groups showed a constant higher NBA and VBH independent to the use of rhPDGF-BB (NBA DBB: 3/0/5, DBB + membrane: 20/35/31, DBB + rhPDGF-BB: 5/8/4, DBB + rhPDGF-BB + membrane: 31/35/40; VBH DBB: 0.3/0.3/0.6, DBB + membrane: 1.6/2.4/2.1, DBB + rhPDGF-BB: 0.4/0.7/0.8, DBB + rhPDGF-BB + membrane: 1.8/2/1.8). CONCLUSIONS: For vertical augmentation, the addition of rhPDGF-BB to DBB-blocks may increase early bone growth. In the later phase, the use of a collagen membrane enhances new bone volume and height to a significant greater extend. Even if the results are higher than those in the non-membrane groups, the low gain of bone after the short time periods still needs improvement.

Methotrexate-loaded polymethylmethacrylate bone cement for local bone metastasis therapy: pilot animal study in the rabbit patellar groove.

Local chemotherapy is an option in bone metastasis treatment. On the other hand, evaluation of side effects on bone is a difficult issue in drug development and biomaterials research. Most animal models to date are inappropriate or not feasible. Rabbits are an alternative to other bigger mammals and have an appropriate bone structure compared to rats and mice. The patellar groove model of the rabbit offers a standardized and sensitive model to evaluate bone-compromising drug effects. We tested the system with a reproducible polymethacrylate implant as carrier and loaded this system with methotrexate. Three methotrexate concentrations were used in the test samples (250 mg, 1 g and 4 g per 40 g polymethacrylate bone cement; 2 per group) for a descriptive histology approach. Eight German giant rabbits were operated on both knees and received test and control implants in a randomized manner in this bilateral study design. The histological results after 35 days were convincing, encouraging the use in preclinical drug development and biomaterials research and warranting further development of this metastasis treatment approach.

Histological examination of drill sites in bovine rib bone after grinding in vitro with eight different devices.

The way in which bone is processed may affect the quality of the specimen and how much information may be gleaned on histological examination. We investigated eight widely used rasps and drills and compared the results. All large chip cutters damaged the bed and marrow of the bone. The tool that caused the least damage was the wet grinding diamond tool.

Vertical bone augmentation procedures: basics and techniques in dental implantology.

An appropriate bony situation is essential for dental implant placement and bony support of soft tissues (pink esthetic). Loss of teeth often results in complex horizontal and vertical alveolar ridge defects. They demand advanced bone augmentation techniques for reconstruction. We present the different techniques and materials used in complex bone augmentation. Clinical cases show the application of the methods in the clinical setting. We present current techniques and materials used in complex bone augmentations. Clinical cases show the application of the methods in the clinical setting. Applied techniques include stabilized-guided bone regeneration (GBR), autologous local block augmentation, modified techniques such as Gellrich shell technique including piezosurgery, pelvic bone blocks, complex materials such as graft-derived bone blocks and their unique handling problems. Successful basic principles are reduction of cortical bone healing due to long remodeling time and possible late loss; extended application of materials with interconnecting porous system and particulate material resulting in fast healing analogous to cancellous bone; mechanical stabilization of the augmentation to allow bony healing in vertical defect situations. GBR and autologous bone blocks with minimal cortical thickness and a high volume of particulated material are most favorable techniques.

Evaluation of demineralized bone and bone transplants in vitro and in vivo with cone beam computed tomography imaging.

OBJECTIVES: The objective of this study was to determine the ability of two flat panel cone beam CT (CBCT) devices to identify demineralized bone and bone transplants in vivo and in vitro. METHODS: Datasets from patients with autologous bone grafts (n = 9, KaVo 3DeXam (KaVo, Biberach, Germany); n = 38, Accuitomo 40 (Morita, Osaka, Japan)) were retrospectively evaluated. Demineralized and non-demineralized porcine cancellous bone blocks were examined with the two CBCT devices. A SawBone skull (Pacific Research Laboratories, Vashon, WA) was used as a positioning tool for the bone blocks. Descriptive evaluation and image quality assessment were conducted on the KaVo 3DeXam data (voxel size 0.3 mm) using the OsiriX viewer as well as on the Morita Accuitomo data (voxel size 0.25 mm) using proprietary viewer software. RESULTS: Both in vivo and in vitro, the descriptive analysis of the images of the two devices showed well-visualized bone transplants with clearly defined cancellous bones and well-defined single bone trabeculae in all cross-sections. In vitro, demineralized samples showed lower radiographic opacity but no significant loss of quality compared with fresh bone (P = 0.070). Single cancellous bone trabeculae were significantly better visualized with the Morita 3D Accuitomo device than with the KaVo 3DeXam device (P = 0.038). CONCLUSION: Both the KaVo 3DeXam and Morita 3D Accuitomo devices produce good-quality images of cancellous bones in in vivo remodelling as well as after in vitro demineralization.

Maxillary sinus anatomy: a cadaveric study with clinical implications.

This study measured maxillary sinus volume, evaluated the location of the semilunar hiatus in correlation to the nasal floor, and the incidence, location, and height of antral septa and discusses their clinical implications. Maxillary sinus volume was quantified in 65 cadavers (130 sinuses) by water application through the semilunar hiatus and measuring the used amount. The location of the semilunar hiatus was identified as distance from the nasal floor. The septa were counted, evaluated, and the size measured from the antral floor. The medium maxillary sinus volume was 12.5 mL (range, 5-22 mL). The medium location of the semilunar hiatus was 25.6 mm above the nasal floor (range, 18-35 mm). Thirty-five septa were counted in 130 maxillary sinuses. This equals an incidence of 27%. The medium height of the septa was 5.4 mm (2.5-11 mm). The main location of the septa was the region of the first molar (29%), the second molar (23%), and the second premolar (23%). The height, location, and number of septa as well as the height of the semilunar hiatus and volume of the maxillary sinus have to be taken into consideration to correctly plan the procedure and amount of grafting material in maxillary sinus floor elevation operations.

Beam hardening artefacts occur in dental implant scans with the NewTom cone beam CT but not with the dental 4-row multidetector CT.

OBJECTIVES: The aim of this study was to examine beam hardening artefacts of the NewTom 9000 cone-beam computed tomography (CBCT) device compared with the Philips MX 8000 (4-row multidetector CT (MDCT)). METHODS: We modified a SawBone skull to become a standardized model for our study. The skull was used for scans with the NewTom 9000 CBCT device and a standard dental multi-detector CT (MDCT) at a comparable reconstruction resolution with a standard Straumann ITI 4.1 mm implant in four implant positions in the maxilla (first permanent premolar in the right maxilla region, second permanent molar in the right maxilla region, first permanent premolar in the left maxilla region and second permanent molar in the left maxilla region). Results were compared with construction data of the dental implant. An image quality assessment of the images from both devices was performed with four experienced physicians and statistically analysed with the two-tailed Wilcoxon test. RESULTS: Scans with the NewTom 9000 CBCT showed strong beam hardening artefacts in the form of a radiation beam shadow in all reconstructions compared with the MDCT. These imaging artefacts became stronger with greater distance from the centre of the scanned volume. These differences in the imaging quality were proved as significant in a quality evaluation by four experienced physicians (P<0.05). CONCLUSIONS: Visual spatial resolution of the NewTom 9000 CBCT was less accurate than the Philips MX 8000 MDCT in the imaging of metallic dental implants.