The efficacy of collagen-hydroxyapatite composite membrane on bone regeneration / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the efficacy of a new collagen-hydroxyapatite (COL-HA) composite membrane on bone regeneration of SD rat cranial defects.</p><p><b>METHODS</b>Four defects were produced in the calvaria of 24 SD rats. The animals were divided into four groups: Empty defects without membrane (group 1); defects covered by COL-HA single-layer dense membranes (group 2); defects covered by COL-HA double-layer membranes (group 3); defects covered by Bio-Gide membranes (group 4). At 2, 4, 8 and 12 weeks after surgery, 6 rats were sacrificed and the following parameters were analyzed: Macroscopic observation, X-ray examination, descriptive histology, regenerate bone quantitative histology. Statistical analysis consisted of generalized linear models/factorial design analysis of variance and LSD-t test was performed.</p><p><b>RESULTS</b>Since two weeks after surgery, there were a small amount of bone regenerated in three groups except group 1. At 12 weeks after surgery, the opaque sclerous tissues filled with the defects in three groups, and residual membrane fragments still could be found. X-ray pictures showed the density of regenerate bone in group 3 and group 4 was closed to the original bone and greater than that of group 2. Quantitative analysis of regenerate bone showed that in initial stage, group 4 had more bone regeneration than the other groups (P < 0.05), and at 12 weeks after surgery the differences between group 4 and group 2/group 3 had no statistically significant.</p><p><b>CONCLUSION</b>The COL-HA composite membranes can guide bone regeneration of rat cranial defects. The efficacy of bone regeneration of COL-HA double-layer membrane is superior to COL-HA single-layer dense membrane, because its property is more propitious to the adherence and proliferation of osteoblasts.</p>

Influence of MgO and TiO2 on mechanical properties of zirconia toughened alumina ceramics formed by gel-casting technique / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The objective of this study is to investigate the influence of mechanical properties and sintering performance by adding 5% weight percentage aids to nano-compound zirconia toughened alumina (ZTA) ceramics.</p><p><b>METHODS</b>Micrometer Al2O3 and nanometer ZrO2 (quality ratio 4:1) were used to get 55% volume percentage slurry. Magnesium oxide and titanium oxide were taken as aids which were 5% weight percentage of the Al2O3 and ZrO2 powder. Five groups (number 0, 1, 2, 3, 4 group) were divided according to different proportion of aids. After gel-casting, the porcelain pieces were sintered at 1150, 1200, 1300, 1400, 1450, 1500, 1600 degrees C for 2 hours. Static three-point flexure strength, line shrinkage, relative density were measured and scanning electron microscopy (SEM) was used to observe section.</p><p><b>RESULTS</b>Number 1 (MgO 1%, TiO2 4%) group had the highest bending strength. It was (401.78+/-19.50) MPa after sintering at 1600 degrees C for 2 hours and was higher than 0 group (380.64+/-44.50) MPa. Bending strength became lower than 0 group when MgO was more than 2% or more than that weight percentage of ZTA powder. When MgO content was higher than 2% or more than that weight percentage, there was no difference in relative density raising rate between each sintering assistants groups. When the sintering temperature was higher than 1200 degrees C, all groups showed obvious line-shrinkage and the groups which contained sintering assistants were all was higher than 0 group.</p><p><b>CONCLUSION</b>Adding MgO and TiO2 aids from 1% to 4% weight percentage of ZTA will promote fritting and increase ZTA nano-compound ceramics mechanical properties. Adding 2% MgO aids or more than that weight percent will has no obvious help to increase the relative density raising rate of ZTA nano-compound ceramics and will degrade the mechanical properties of ZTA nano-compound ceramics.</p>

Influence of ambient light and adjacent tooth in anterior tooth color measurement / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the influence of different intensity and directions of ambient light and adjacent tooth in anterior tooth color measurement by using colorimeter.</p><p><b>METHODS</b>Fiber lite MI-150 was used as ambient illuminant and it irradiated from three or twelve o'clock direction through 45 degrees angle above. The light magnitude 0, 50, 75, 100, 125, 150 W were applied in this experiment. The values of CIE L* a* b* were measured by Minolta Chroma meter CR-321 colorimeter on the center labial surface of ten extracted human maxillary central incisors with or without adjacent teeth, then those data were analyzed statistically by using SPSS 11.5.</p><p><b>RESULTS</b>Neither different intensities nor different directions of ambient light could influence the results of color measurement by using Minolta Chroma meter CR-321 colorimeter, so did the adjacent teeth whether those were exist or not.</p><p><b>CONCLUSION</b>There is no influence of ambient light and adjacent teeth in the color measurement of anterior teeth under this experiment condition, and Minolta Chroma meter CR-321 colorimeter can be used to measure the color directly aside the chair with light.</p>