PubMed Health⌕ Search

Biomedical subjects

C T Kao

Publications and source records attributed to C T Kao.

At least 19 recordsLinked to original sources
PubMed2001

Root canal sealers cause cytotoxicity and oxidative damage in hepatocytes.

Elutable substances and degradation products from root canal sealers may gain access to periodontal tissue in many ways. The aim of this study was to investigate damage and oxidative stress caused by treatment with root canal sealers in primary cultured rat hepatocytes. Four root canal sealers were used: Canals, Sealapex, AH 26, and AH Plus. Toxicity was detected by assessing lactate dehydrogenase (LDH) leakage, and oxidative stress was determined by analysis of glutathione (GSH) levels. One-way analysis of variance was performed on the data. As the concentrations of sealer were increased, LDH leakage increased (p < 0.01). Increased GSH depletion accompanied LDH leakage increase. GSH levels were reduced to zero at a concentration of 0.05% for Canals and 0.10% for AH 26. These results confirmed the hypothesis that root canal sealers can cause cytotoxicity in hepatocytes. The Canals and AH 26 sealers can also cause oxidative stress in hepatocytes.

Animals↗
PubMed2001

Comparison of ion release from new and recycled orthodontic brackets.

Bracket corrosion can occur in the oral environment. The purpose of this study was to compare the release of metal ions from new and recycled brackets in artificial saliva and buffers with different pH values over a 12-week immersion period. The brackets were divided into 2 groups: new and recycled. The recycled bracket bases were coated with adhesive and the brackets were heat treated. Nickel, chromium, iron, and manganese ions were detected by atomic absorption. The surface characteristics of the brackets were examined by energy dispersive radiographic analysis. The results were as follows: (1) Recycled brackets released more ions than did the new brackets. (2) Greater amounts of nickel, iron, and manganese ions were released in artificial saliva than in the other buffers tested. (3) Ion release from brackets in a pH 4 buffer was greater than that observed in pH 7 or pH 10 buffers. (4) The total amount of ion release increased with time. (5) After a 12-week immersion, the total ion release averaged over the period did not exceed the recommended daily intake.

Adhesives↗
PubMed2001

The shear bond strength of composite brackets on porcelain teeth.

Recent advances in materials and techniques suggest that direct bonding of orthodontic attachments to surfaces other than enamel may now be possible. To test the effectiveness of bonding orthodontic attachments to porcelain teeth, composite brackets (Spirit MB) were bonded to 64 porcelain teeth by means of a self-cure non-mixed resin system (Unite). The 64 porcelain teeth were divided into groups of eight and after roughening with a green stone they were subjected to a combination of treatments. Some were etched, some primed with a silane coupling agent and some received both treatments before the brackets were bonded to them. Half of the teeth were then thermally-cycled 500 times between 4 and 60 degrees C before all the brackets were removed in a shear test. The shear data was analysed by one way analysis of variance and the Student-Newman-Keul test. The results showed that the highest bond strength existed in the group which had been both etched and primed but not thermocycled (P < 0.05). The factors that affected the bond strength, beginning with the most significant, were acid etching, primer application, and then thermocycling. A mechanical based composite bracket can offer good bond strength to porcelain teeth.

Acid Etching, Dental↗
PubMed2001

Evaluation of the genotoxicity of zinc oxide eugenol-based, calcium hydroxide-based, and epoxy resin-based root canal sealers by comet assay.

Three main types of root canal sealer are currently commonly used in pulp treatment: zinc oxide eugenol-based, calcium hydroxide-based, and epoxy resin-based sealers. In the present study, the genotoxicity of sealer on oral carcinoma cells was evaluated by single-cell gel electrophoresis assay (comet assay). The whole length of the comet and the diameter of the head were measured using an image analysis system. The results were analyzed by one-way analysis of variance to compare the various means. The zinc oxide eugenol-based sealers (Canals, Canals-N, and Tubilseal) did not always cause a dose-dependent increase in genotoxicity. The resin-based sealers (Topseal, AH 26, and AH Plus) caused a dose-dependent increase in genotoxicity, but no such effect was seen with the calcium hydroxide-based sealer (Sealapex). The highest level of DNA damage was induced by the resin-based sealers.

Analysis of Variance↗
PubMed2000

Lactate dehydrogenase leakage of hepatocytes with AH26 and AH Plus sealer treatments.

Numerous root canals filling materials are available in the field of dentistry, based on various formulas that contain a variety of different and partly mutagenic components, such as epoxy resin sealers, Ca(OH)2-based materials, and zinc oxide-eugenol cements. AH Plus root canal sealer will not release formaldehyde according to the manufacturer, although AH26 does. The purpose of this study was to analyze the leakage of lactate dehydrogenase (LDH) from rat hepatocytes after treatment with AH26 and AH Plus root canal sealers in vitro. Hepatocytes from male Sprague-Dawley rats were used to test the cytotoxicity of AH26 and AH Plus. The root canal sealers were mixed and then dissolved in the dimethyl sulfoxide to final concentrations of 0.01%, 0.04%, and 0.1% (wt/vol), with a dimethyl sulfoxide concentration of < 0.05%. Dosage-dependent and time-dependent lactate dehydrogenase leakage values were measured and tested by one-way ANOVA. The results showed that both AH26 and AH Plus are toxic to rat hepatocytes. At a low concentration, AH26 had a higher toxicity than AH Plus to rat hepatocytes.

Analysis of Variance↗
PubMed1998

pH measurement of root canal sealers.

The purpose of this study was to compare the surface pH level of three different type sealers after mixing at various time intervals in vitro. The cements were mixed according to the manufacturer's instructions. They were incubated to set in 100% humidity at 37 degrees C for 1 h, 24 h, 5 days, 8 days, 2 wk, 3 wk, 4 wk, 5 wk, and 7 wk. pH was calculated by a Twin pH meter. The pH levels of the three sealers were different at various time intervals (p < 0.0001). The resin-based cement had a acid pH level (pH < 7.0). The calcium hydroxide-based cement showed a higher alkalinity pH level (pH > 7.0). The zinc oxide-eugenol-based cement showed a similar pH level to the calcium hydroxide cement at the end of the measurement. We postulated that, in endodontic therapy when those healing is needed, the alkaline-based sealer is the choice.

Analysis of Variance↗
PubMed1997

Evaluation of four prescriptions of traditional Chinese medicine: syh-mo-yiin, guizhi-fuling-wan, shieh-qing-wan and syh-nih-sann on experimental acute liver damage in rats.

Syh-Mo-Yiin (SMY), Guizhi-Fuling-Wan (GFW), Shieh-Qing-Wan (SQW) and Syh-Nih-Sann (SNS) are four prescriptions of Traditional Chinese Medicine (TCM) used in the remedy of liver trouble in various types. The hepatoprotective effects of water extracts of these four recipes against D-galactosamine (D-GalN) and carbon tetrachloride (CCl4)-induced acute hepatic damage were determined in rats. The results indicated that the serum glutamate-oxalate-transaminase (sGOT) and the serum glutamate-pyruvate-transaminase (sGPT) levels provoked by D-GalN and CCl4 decreased after treatment with these prescriptions of TCM. Histological changes around portal area (D-GalN-induced hepatotoxicity) and central vein (CCl4-induced hepatotoxicity) were simultaneously improved by the treatment with TCM mentioned above.

Alanine Transaminase↗
PubMed1997

The arc index in evaluation of Class III malocclusion.

Lateral cephalometric radiographs were obtained for 46 individuals (18 men and 28 women) aged 20 to 30 years. The sample consisted of Taiwanese with Class III malocclusions and prognathic facial profiles. A modification of the Sassouni arch analysis was used to evaluate this group. All parameters were compared with the norms for adult Taiwanese. The facial pattern of the Class III group was similar to that reported in other studies. The maxilla was in a retrusive position; the lengths of the maxilla and the mandible were significantly different from those in the normal group; the mandibular central incisor was retroinclined; and the total gonial angle, upper gonial angle, and lower gonial angle in the Class III group were significantly different from those angles in the normal group in both sexes. The arc index represented the maxillomandibular positional relationship. There was a statistically significant difference between the mean arc indexes of the Class III and the normal groups. The results indicated that the more negative the arc index, the greater the Class III tendency.

Adult↗
PubMed1996

Over-expression of p55Cdc inhibits granulocyte differentiation and accelerates apoptosis in myeloid cells.

p55Cdc is a protein identified in cycling mammalian cells. It is highly expressed in proliferating but not in differentiated or growth-arrested cells. Structurally, p55Cdc is similar to the Cdc4 and Cdc20 proteins, which have been proposed to regulate DNA synthesis and mitosis in Saccharomyces cerevisiae. To define the role of p55Cdc during myelopoiesis, we studied the expression and regulation of this protein in response to the hematopoietic growth factors, granulocyte-macrophage colony stimulating factor (GM-CSF) and granulocyte-colony stimulating factor (G-CSF). We analysed the time course of expression of p55Cdc in response to GM-CSF and G-CSF stimulation in the murine factor-dependent myeloid leukemic cell line, 32Dc13, and demonstrated differential regulation of p55Cdc in response to these two growth factors. Over-expression of p55Cdc resulted in acceleration of apoptosis in growth factor- and serum-free conditions, although no difference was observed in the rate of cell proliferation. Decreases in p55Cdc protein levels correlated with cells undergoing apoptosis. p55Cdc over-expression also inhibited granulocyte differentiation of 32Dc13 cells treated with G-CSF. Our studies suggest that p55Cdc regulation is critical for normal cell cycle control during myeloid cell proliferation and differentiation.

Animals↗
PubMed1996

The morphologic structure of the openbite in adult Taiwanese.

Anterior openbite (AOB) is an intricate occlusal problem. Treatment of AOB is one of the most challenging tasks in orthodontics. An ethnic-specific norm for craniofacial skeletal patterns would be valuable in diagnosing and treating patients with AOB. To establish this norm for the people of Taiwan, a cephalometric study was conducted using the quadrilateral analysis developed by DiPaolo. The sample consisted of 15 males and 25 females in their 20s and 30s. The patients were randomly selected and were diagnosed with AOB. Various craniofacial skeletal patterns were measured, and these measurements were compared with values taken from a group of normal Taiwanese as well as with published values from a hyperdivergent group of westerners. The results support the following generalizations: (1) The growth pattern of subjects in the AOB group is hyperdivergent. (2) Both the maxillary and mandibular corpora of subjects with AOB are shorter than those of normal subjects. (3) The sagittal angle, average lower facial height, and the maxillary and mandibular sagittal ratio of subjects with AOB are larger than those of normal subjects. Abnormalities in the maxillomandibular complex causing changes in the vertical dimension of facial patterns are involved in AOB.

Adult↗
PubMed1995

The craniofacial morphologic structures of the adult with Class III malocclusion.

The morphologic study of adults with true Class III malocclusion has seldom been reported. Tracings of lateral cephalograms of 51 Taiwanese adults with true Class III malocclusion were subjected to quadrilateral analysis. Means and standard deviations, t test, correlation analysis, and regressive analysis were used to compare the differences between this group and a reference population of adults with normal occlusion. The results indicated that the maxillary base is shorter and in a more retrusive position in adults with Class III malocclusion. Furthermore, the mandible is in a more protrusive position. The pattern of growth in the Class III malocclusion was found to be horizontal, that is hypodivergent. In diagnosis of the abnormality, the rule of the quadrilateral can provide assistance. That is, the maxillary base length, mandibular base length, anterior lower facial height, and posterior lower facial height can be used to evaluate the abnormality. In postural relationships the sagittal angle, vertical sagittal ratio, and horizontal sagittal ratio can be used as a reference.

Adult↗
PubMed1992

Effect of heart rate on pressure half-time in patients with mitral stenosis.

The effect of heart rate on pressure-half time has been controversial. This study attempted to clarify this issue in patients with mitral stenosis. Twenty cases were enrolled, 10 with atrial fibrillation and 10 with sinus rhythm. Twenty beats were analyzed for each patient. The results showed that in patients with atrial fibrillation the pressure half-time was hardly measurable in the cardiac cycles with a ventricular rate more than 100/min; by excluding these fast beats, the pressure half-time showed no relationship with the heart rate. Similarly, there was no significant correlation between heart rate and pressure half-time in patients with sinus rhythm when the heart rate was less than 70/min. However, if the sinus rate was more than 70/min, the correlation became statistically significant. We conclude that when using pressure half-time to derive mitral valve area we should avoid to use the beats with ventricular rate greater than 100/min in patients with atrial fibrillation. In patients with sinus rhythm, we should try to use those beats with heart rate greater than 70/min if possible. Otherwise, significant error may occur.

Adult↗
PubMed1991

[Survey on oral hygiene status in children with Down's syndrome and mental retardation].

The purpose of this study was to compare the periodontal condition of children with Down's syndrome and other types of mental retardation with normal children. We used two indexes: a plaque index and a gingival index. By means of the student t-test and ANOVA statistical procedure, we found the following. Mentally retarded children had a higher average intelligence than children with Down's syndrome, and significant differences existed among the three groups on both the plaque index and the gingival index, while sex had no influence on these results.

Analysis of Variance↗