Biomedical subjects

Chun-Cheng Hung

Publications and source records attributed to Chun-Cheng Hung.

8 recordsLinked to original sources

PubMed2006

Reducing, by pulse width modulation, the curing temperature of a prototype high-power LED light curing unit.

Third-generation LEDs have high irradiance and efficiency, but the associated temperature rise is potentially hazardous to the pulp of teeth. We evaluated, during composite polymerization, the irradiance and temperature rise of a prototype high-power LED light curing unit (LCU) with optimal pulse width modulation (PWM), and then compared the results with four off-the-shelf high-power LCUs. A cavity was prepared in a tooth, and a composite resin layer was applied and cured. For each LCU, the irradiance and temperature changes at the pulp-dentin junction were measured. Microhardness (Vickers hardness) of cured composite samples was measured for each LCU. Our prototype had a final temperature of 36.4 +/- 1.3 degrees C and irradiance of 1,182 +/- 1 mW/cm2. The unit with the highest temperature had a temperature of 48.7 +/- 1.2 degrees C and an irradiance of 1,194 +/- 1 mW/cm2. Based on the results of the present study, it was shown that PWM technology reduced the curing temperature while retaining the polymerization effectiveness of a high-power LED LCU.

Analysis of Variance↗

PubMed2006

Effects of welding pulse energy and fluoride ion on the cracking susceptibility and fatigue behavior of Nd:YAG laser-welded cast titanium joints.

In this study, the cracking susceptibility and fatigue behavior of Nd:YAG laser-welded cast Ti joints (welding pulse energy: 11, 15, and 18 J) in fluoride-containing (0 and 0.5% NaF) artificial saliva were evaluated using constant elongation rate test (CERT) and fatigue test (FT), respectively. Both CERT and FT were also carried out in open air as controls. Results showed that increasing the welding energy increased the elongation and fatigue life, but decreased the tensile strength, of cast Ti joints in open-air environment. With a welding energy of 11 J, the fluoride ions in the artificial saliva increased the cracking susceptibility and decreased the fatigue life of Ti joints. When the welding energy exceeded 15 J, the presence of fluoride ions still increased the cracking susceptibility, but did not reduce the fatigue life of Ti joints. Rupture of Ti joints--if it occurred--occurred only at the welded metal (versus the non-welded part).

Cariostatic Agents↗

PubMed2005

Interleukin-12 and interleukin-16 in periodontal disease.

The immune system plays an important role in the pathological process of periodontitis. Interleukin-12 (IL-12) is produced by monocytes, macrophages and neutrophils. These cells are proinflammatory infiltrates in periodontitis tissues. High IL-12 will contribute to the immune reaction to Th1 type. IL-12 is an inducer of INF-r production. IFN-gamma itself can also activate IL-12 production. Lipopolysaccharides (LPS) of periodontopathogens are also activators of IL-12. Interleukin-16 (IL-16) can cause the high affinity of IL-2 receptors on CD4+ cells and is chemotaxis to Th1 cells and CD4+ T cells. IL-16 can stimulate monocytes to produce proinflammatory cytokines and is highly associated with inflammation including arthritis, enteritis and allergic rhinitis. However, the information on IL-12 and IL-16 in periodontitis is not clear. In this study, 105 GCF samples were collected from 19 periodontal disease patients and 6 healthy ones. The clinical periodontal indices, the habits of cigarette smoking and alcohol drinking were recorded. ELISA was used to determine the levels of IL-12 and IL16 in the GCF. In the non-smoking/non-alcohol-drinking individuals: (1) the total amount of IL-12 (but not IL-16) was significantly higher in chronic periodontitis (CP) sites than gingivitis (G) or healthy (H) sites; (2) the diseased sites (CP + G) had a significantly higher total amount of IL-12 (but not IL-16) than the H sites. Among CP sites, both the concentration and total amount of IL-16 (but not IL-12) were significantly higher in alcohol drinkers/cigarette smokers as compared to the non-drinkers/non-smokers. CP sites of the drinkers/smokers also had significantly deeper probing pocket depth than sites of those without these two habits. IL-12 and IL-16 may be related to the pathogenesis of periodontal disease, but within the periodontitis sites, IL-16 may be related to disease severity in alcohol drinkers/smokers.

Alcohol Drinking↗

PubMed2005

Topographic study of root trunk type on Chinese molars with Class III furcation involvements: molar type and furcation site.

This study investigated the relationship between root trunk length and prognosis for molars with furcation involvement. Molars with furcation involvement were obtained from 169 patients affected with periodontitis. The test group consisted of 174 hopeless molars screened from a total of 441 molars with Class III involvement; the remaining 267 molars formed the control group. Both arches showed a significantly higher missing rate for teeth with a long root trunk length (type C) in second molars (41.3% and 32.4% in the maxilla and mandible, respectively), with a high degree of Class III furcation involvement for the test group (extracted hopeless or poor prognosis), compared to first molars (9.9% and 0.9% in the maxilla and mandible, respectively). Both arches had a significantly higher prevalence of long root trunk lengths in the second molars compared to first molars, irrespective of furcation site. Although first molars had an early and higher prevalence of Class III furcation involvement than second molars, the latter reached a significantly higher missing rate. Molars with longer root trunk lengths had a higher risk for poor prognosis than shorter root trunks when teeth were affected by Class III furcation involvement. For extracted furcation-involved maxillary second molars that failed to respond to periodontal therapy, long root trunk length (C) accounted for the greatest prevalence at the mesial furcation site (41.8%), followed by the distal (33.0%) and buccal sites (25.2%); the greatest prevalence of root trunk length C was found at the lingual (47.9%) and buccal furcation sites (45.1%) of mandibular second molars. When a molar with root trunk type C has a Class III involvement, the prognosis is poor; for the disease to reach that level, greater amounts of attachment must be destroyed.

Adult↗

PubMed2004

Pure titanium casting into zirconia-modified magnesia-based investment molds.

OBJECTIVE: Molten titanium is highly reactive with common mold materials at elevated temperatures. The aim of this investigation was to improve the accuracy of pure titanium casting by adding unreactive zirconia into magnesia-based investment material. METHODS: An automatic thermal expansion laser-recording machine (TEM-1000/Pantos, Nippon Co.) was used to measure thermal expansion of investment materials. An automatic argon-casting machine (Castmatic-S, Iwatani Co.) was used to cast pure titanium samples. A stereomicroscope was used (Nikon SM-2T, Japan) to measure marginal discrepancy on a metal die. A Vickers microhardness indenter (MXT-50, Matsuzawa Seiki Co.) determined the Vickers hardness (VH) of the titanium samples. Interfacial reactivity of the titanium was evaluated with an X-ray diffractometer (Rigaku D/max VIII, Tokyo, Japan). A dental X-ray machine was used to examine internal porosity of the castings. Data was analysed with paired t-test (p < 0.05), ANOVA/Tukey's HSD test (p < 0.001) and Spearman's correlation test (p < 0.05). RESULTS: Addition of 5.0-6.0 mass% of zirconia to a magnesia-based investment material significantly increased its thermal expansion value (p < 0.05). ANOVA indicated significant marginal discrepancy differences within the zirconia-added group (p < 0.001). There was a significant correlation between thermal expansion at 750 degrees C and marginal discrepancy (p < 0.05). The addition of zirconia decreased interfacial reactivity and the VH of titanium. SIGNIFICANCE: Under appropriately adjusted conditions, the addition of zirconia to magnesia-based mold materials may be used to produce high quality pure titanium castings.

Analysis of Variance↗

PubMed2003

Topographic study of extracted molars with advanced furcation involvement: furcation entrance dimension and molar type.

This study investigated the topography of the furcation entrance dimension (FED) on molars with advanced furcation involvement (FI). The sample pool consisted of 169 maxillary and mandibular molars from a group of 165 individuals with severely advanced periodontal destruction. The subjects included men and women aged 24 to 84 years (mean, 47.8 +/- 7.2 years). The FEDs of the maxillary buccal, mesial, and distal surfaces as well as the mandibular buccal and lingual surfaces were measured under a stereomicroscope and clarified into grades I (FED < 0.55 mm), II (0.55-0.75 mm), and III (> 0.75 mm) using automatic grading system software designed by our research associates. The differences and relationships among molar location, furcation site, and FED grade were analyzed using the chi-square test. There was a significant difference among buccal (BFED), mesial (MFED), and distal (DFED) FEDs in both the maxillary first (chi2(4) = 58.915, p < 0.001) and second (chi2(4) = 66.839, p < 0.001) molars. The relationship between molar type and FED grade was statistically significant for both the BFED (p < 0.001) and the DFED (p < 0.001) of maxillary molars, as well as for both the BFED (p < 0.0001) and LFED (p < 0.0001). The difference in FED grade between the first and second molars was statistically significant in both maxillary (p < 0.001) and mandibular (p < 0.0001) molars. There was a significant relationship between FED grade and tooth location at molars with advanced FI.

Adult↗

PubMed2003

Effect of zirconia-modified magnesia investment on the casting of pure titanium.

Several investigations have examined magnesia-based investments for pure titanium casting. However, the thermal expansion value was insufficient at low casting temperatures and high interfacial reactivity occurred at high casting temperatures. The purpose of this investigation was to modify a magnesia-based investment by adding a heat-resistant mold material, zirconia, in different ratios to produce a more accurate titanium casting. The thermal expansion value was measured using a new precise automatic laser recording machine and pure titanium was cast using an argon casting machine. The marginal accuracy was measured using a stereomicroscope and the interfacial reactivity of the titanium was evaluated using X-ray diffraction analysis. The results indicate that adding different amounts of zirconia to a magnesia-based investment can increase its thermal expansion value and decrease the interfacial reactivity of the titanium. Maximal thermal expansion in the zirconia-modified investments significantly increased by 5-6 weight % (wt%) and peaked at 1.62% expansion. Selevest with 5 wt% zirconia had the smallest mean marginal discrepancy, 21.70 microm at 750 degrees C. Analysis of variance indicates significant differences in marginal discrepancy between zirconia-modified investments (p < 0.001). Adding zirconia can also decrease the interfacial reactivity of the titanium. The data indicated that proper amounts of zirconia (5-6 wt%) added to a magnesia-based investment can produce a more accurate and less interfacial reactive pure titanium casting.

Dental Casting Investment↗

PubMed2002

Periodontal bone loss in Chinese subjects with untreated early-onset and adult periodontitis: a cross-sectional study using digital scanning radiographic image analysis.

The purpose of this investigation was to evaluate the differences in radiographic alveolar bone loss (RABL) in Taiwanese subjects with early-onset periodontitis (EOP) and adult periodontitis (AP) using the digital scanning radiographic image analysis (DSRIA). A total of 4,262 teeth from 178 individuals (96 males and 82 females) were examined for RABL due to EOP and AP. The subjects with EOP and a comparison group with AP were identified from the Periodontal Clinic population (College of Dental Medicine, Kaohsiung Medical University). The following criteria were used to classify subjects with EOP and AP during the past 20 years. The RABL of teeth were calculated using a computer system equipped with Microstation 95 software, under 10 X magnification of the radiographs. Quantity assessment of RABL using the DSRIA showed that: (1) the means of RABL of maxillary and mandibular anterior teeth in the EOP group were significant greater than those in the AP group when the two sample t-test was used. (2) The greatest values of mean RABL of affected sites in the EOP group occurred most commonly in the first molars and mandibular incisors, whereas, in the AP group, the greatest values of mean RABL of affected sites occurred most commonly in the first and second molars. (3) Molars had the greatest mean RABL followed by incisors, premolars and canines. (4) The mean RABL increased with increasing age. We conclude that the features of naturally progressing alveolar bone loss at the molar and incisor sites in untreated subjects with the EOP and AP revealed that the mean RABL in the EOP group was faster and greater than that in the AP group.

Adult↗