Modified method of recording and reproducing natural head position with a multicamera system and a laser level.

INTRODUCTION: As computer-assisted surgical design becomes increasingly popular in maxillofacial surgery, recording patients' natural head position (NHP) and reproducing it in the virtual environment are vital for preoperative design and postoperative evaluation. Our objective was to test the repeatability and accuracy of recording NHP using a multicamera system and a laser level. METHODS: A laser level was used to project a horizontal reference line on a physical model, and a 3-dimensional image was obtained using a multicamera system. In surgical simulation software, the recorded NHP was reproduced in the virtual head position by registering the coordinate axes with the horizontal reference on both the frontal and lateral views. The repeatability and accuracy of the method were assessed using a gyroscopic procedure as the gold standard. RESULTS: The interclass correlation coefficients for pitch and roll were 0.982 (0.966, 0.991) and 0.995 (0.992, 0.998), respectively, indicating a high degree of repeatability. Regarding accuracy, the lack of agreement in orientation between the new method and the gold standard was within the ranges for pitch (-0.69°, 1.71°) and for roll (-0.92°, 1.20°); these have no clinical significance. CONCLUSIONS: This method of recording and reproducing NHP with a multicamera system and a laser level is repeatable, accurate, and clinically feasible.

[Comparison of genetic damage in mice exposed to black carbon and ozone-oxidized black carbon].

OBJECTIVE: To make an assessment on the genotoxicity caused by black carbon (BC) and ozonized black carbon (O3-BC). METHODS: In this study, 74 healthy male ICR mice [weighed (28 ± 1.5) g] were randomly divided into 7 groups, including one phosphate buffer solution (PBS) control group and six particles exposed groups by intratracheal instillation with either BC or O3-BC at the doses of 50, 100, 200 µg/mouse, respectively. There were 12 mice in the groups of 200 µg/mouse and 10 mice in others. The mice were sacrificed 24 h after four intratrachealinstillations. The activities of catalase (CAT) in serum and the levels of malondialdehyde (MDA) in lung tissue homogenate were measured. As the DNA damage mark, 8-hydroxyguanosine (8-OHdG) in urine and serum were quantified with ELISA method. Micronucleus test was used for potential genotoxicity of BC and O3-BC. Hematoxylin and eosin staining was used to stain lung paraffin section. RESULTS: The mice were in good condition during instillation, and the liver coefficient of the test groups was significantly lower than that of the control group (P<0.05). The activities of CAT in serum significantly increased in the 100 µg/mouse and 200 µg/mouse groups after being exposed to these two kinds of particles. The micronucleus rate in allthe BC and O3-BC exposed groups increased (P<0.05), but there was no statistically significant difference among the groups in the levels of 8-OHdG in serum and urine and MDA in lung tissue homogenate. Inflammatory response was found in the lung tissue under the microscope after exposure to BC and O3-BC. CONCLUSION: Intratracheal instillation of BC and O3-BC induced increasing of oxidative stress and genetic damage in mice. But there was no significant difference between these two particles in toxicity. Whether the genotoxicity of O3-BC is higher than that of BC or not is uncertain. Further research is needed.