[Measurement of facial bone wall thickness of maxillary anterior teeth and premolars on cone beam computed tomography images].

OBJECTIVE: To measure the thickness of facial bone wall of maxillary anterior teeth and premolars based on cone beam computed tomography (CBCT) images. METHODS: CBCT images from 118 patients were collected from the Affiliated Stomatology Hospital of Zhejiang University. The thickness perpendicular to the long axis of facial bone wall was measured at two locations: 4 mm apical to the cementoenamel junction (point 1) and the middle of the root (point 2). RESULTS: The thickness of the facial bone walls of central incisors, lateral incisors and canines ranged from 0.5 to 1.5 mm. A thin facial bone wall (<1.0 mm) was quite frequent in central incisors (44.1% at point 1, 56.8% at point 2), lateral incisors (65.2% at point 1, 89.8% at point 2) and canines (45.8% at point 1, 61.0% at point 2). In contrast, the majority of examined first premolars (77.1% at point 1, 68.7% at point 2) and second premolars (94.1% at point 1, 94.1% at point 2) exhibited a thick facial bone wall (>1.0 mm). CONCLUSION: A thin facial bone wall of teeth in the anterior maxilla is common. Radiographic analysis of facial bone wall using CBCT is recommended for selection of appropriate treatment approach.

Chiral separation of D,L-mandelic acid through cellulose membranes.

This work reports the chiral separation of D,L-mandelic acid with cellulose membranes. Cellulose was chosen as membrane material because it possesses multichiral carbon atoms in its molecular structure unit. The flux and permselective properties of membrane using aqueous solutions of D,L-mandelic acid as feed solution was studied. The top surface and cross-section morphology of the resulting membrane were examined by scanning electron microscopy. When the membrane was prepared with 8.1 wt % cellulose and 8.1 wt % LiCl in the DMA casting solution, and the operating pressure and feed concentration of racemate were 0.0125 MPa and 0.5 mg/ml, respectively, over 90% of enantiomeric excess could be obtained. This is the first report that the cellulose membrane is used for isolating the optical isomers of D,L-mandelic acid. Chirality, 2011.

Bone formation at porous titanium implants coated with multiple layers of recombinant human bone morphogenetic protein-2 cDNA plasmid in the posterior mandible in dogs.

PURPOSE: The objective of this study was to evaluate peri-implant bone formation and osseointegration at titanium implants coated with multiple layers of recombinant human bone morphogenetic protein-2 (rhBMP-2) cDNA placed into canine mandibles. MATERIALS AND METHODS: The rhBMP-2 plasmid was assembled on sandblasted/dual-acid-etched pure titanium implant surfaces using layer-by-layer assembly. The rhBMP-2 plasmid-coated implants were placed into the edentulous posterior mandibles of 12 adult beagle dogs. Implants without the rhBMP-2 plasmid coating served as controls. Treatments were randomized between jaw quadrants, and four implants were placed in each mandibular quadrant. After 4, 8, and 12 weeks in situ, mandibles were retrieved and prepared for removal torque testing and histomorphometric evaluation. RESULTS: Eight layers of rhBMP-2 plasmid were assembled onto the implant surfaces. Histomorphometric analysis showed that, after 4 and 8 weeks of healing, the intrathread bone area (BA) was slightly higher for test implants (54.21% and 59.56%) than for control implants (38.48% and 54.98%), respectively, but no statistically significant differences were seen at any time points. Mechanical tests showed that the mean removal torque values of the rhBMP-2 cDNA-coated implants were greater than those of the control implants after 8 weeks of healing (91 Ncm versus 61 Ncm; P = .31). CONCLUSION: Coating implants with multiple layers of an rhBMP-2 plasmid did not promote peri-implant bone formation and osseointegration in this model.