Biomedical subjects

Wan-Hong Lan

Publications and source records attributed to Wan-Hong Lan.

32 records · Page 2Linked to original sources

PubMed2004

Successful treatment of oral verrucous hyperplasia with topical 5-aminolevulinic acid-mediated photodynamic therapy.

Previous studies have shown a selective accumulation of 5-aminolevulinic acid (ALA)-derived protoporphrin IX (PpIX) in oral premalignant and malignant tissues. This provides a biologic rationale for the clinical use of ALA-mediated PDT (ALA-PDT) for oral premalignant and malignant lesions. In this study, five patients with oral verrucous hyperplasia (OVH) were treated with a new protocol of ALA-PDT composed of multiple 3-min irradiations with a light emitting diode (LED) red light at 635+/-5 nm separated with several 3-min rests for a total of 1000 s (fluence rate, 100 mW/cm(2); light exposure dose, 100 J/cm(2)) after topical application of 20% ALA for 1.5 or 2 h. Topical ALA-PDT was repeated once a week until the complete regression of the lesion. Complete regression of all OVH lesions was observed after 1-3 treatments (average, 2 treatments) of topical ALA-PDT. At an average follow-up of 5.6 months (range, 3-11 months), all the five OVH patients were free of tumor recurrence. We conclude that topical ALA-PDT with fractionated irradiations by an LED red light at 635+/-5 nm is an effective and successful treatment modality for OVH.

Adult↗

PubMed2004

Effects of physiological environments on the hydration behavior of mineral trioxide aggregate.

Utilizing scanning electron microscope, X-ray diffraction (XRD) and microhardness tests, we evaluated how various physiological environments affect the hydration behavior and physical properties of mineral trioxide aggregate (MTA). We found that the microstructure of hydrated MTA consists of cubic and needle-like crystals. The former comprised the principal structure of MTA, whereas the later were less prominent and formed in the inter-grain spaces between the cubic crystals. MTA samples were hydrated in distilled water, normal saline, pH 7, and pH 5. However, no needle-like crystals were observed in the pH 5 specimens, and erosion of the cubic crystal surfaces was noted. XRD indicated a peak corresponding to Portlandite, a hydration product of MTA, and the peak decreased noticeably in the pH 5 group. The pH 5 specimens' microhardness was also significantly weaker compared to the other three groups (p<0.0001). These findings suggest that physiological environmental effects on MTA formation are determined, in part, by environmental pH and the presence of ions. In particular, an acidic environment of pH 5 adversely affects both the physical properties and the hydration behavior of MTA.

Aluminum Compounds↗

PubMed2004

Effectiveness of an educational program in reducing the incidence of wrong-site tooth extraction.

OBJECTIVES: The aim of the study was to investigate the effectiveness of an educational program on the reduction of the incidence of wrong-site tooth extraction at the outpatient department of a university hospital in Taiwan. STUDY DESIGN: Data collected from cases of wrong-site tooth extraction during 1996 to 1998 were used to develop a specific educational intervention that was implemented from 1999 to 2001. The annual incidence of erroneous extraction was compared between the preintervention and intervention periods. The factors contributing to wrong tooth extraction were also analyzed. RESULTS: The annual incidence rates of erroneous extraction from 1996 to 1998 were 0.026%, 0.025%, and 0.046%, respectively. During the intervention period from 1999 to 2001, wrong-site tooth extraction did not occur at the department. There was a significant difference in the incidence of erroneous extraction between the preintervention and intervention periods (P<.01). Cognitive failure was the most frequent form of active failure responsible for wrong-site tooth extraction, whereas communication and training were found to be major latent factors contributing to these errors. CONCLUSIONS: Our results suggest the effectiveness of an educational program comprising case-based materials, information feedback, and clinical guidelines in reducing the incidence of wrong-site tooth extraction.

Adolescent↗

PubMed2004

Thermal effect and morphological changes induced by Er:YAG laser with two kinds of fiber tips to enlarge the root canals.

OBJECTIVE: The aim of this study was to assess the application of Er:YAG laser root canal preparation using two fiber tip systems. BACKGROUND DATA: Previous studies have not shown the thermal effect of Er:YAG laser using cone-shaped fiber tip. MATERIALS AND METHODS: The ability of Er:YAG laser to enlarge root canals at a pulse energy set at 30 or 20 mJ and constant pulse rate of 10 pps (pulses per second) was tested. A cone-shaped (84 degrees top angle) or a flat fiber tip of Er:YAG laser was used for comparison. Four groups of 15 artificial root canals with fixed dimension were prepared from bovine teeth. Irradiation was accompanied by sterilized distilled water spray (2 mL/min). The temperature changes on the root surface were recorded with an infrared apparatus, and the thermal images were captured with a thermocamera. The morphological changes of irradiated root canals were examined by a scanning electron microscope (SEM). RESULTS: The mean temperature rises were 9.4 degrees C and 7.1 degrees C with the cone-shaped fiber tip at a pulse energy of 30 and 20 mJ, respectively, and were 11.0 degrees C and 6.5 degrees C with flat fiber tip at a pulse energy of 30 and 20 mJ, respectively. Marked difference in temperature change between the cone-shaped and flat fiber tips was noted at pulse energy of 30 mJ, but not at 20 mJ. The thermal distribution using the cone-shaped fiber tip (in contrast to the flat tip) had an elliptical shape around the fiber tip and was limited to the apical end of the root canals. SEM observation found that irradiation with cone-shaped fiber tip (in comparison to the flat tip) produced a cleaner surface. CONCLUSION: Our results suggest that the cone-shaped fiber tip of Er:YAG laser produced fewer thermal effects and morphological changes as compared to the other type of fiber tip.

Animals↗

PubMed2004

Structural changes of Er:YAG laser-irradiated human dentin.

OBJECTIVE: The aim of this study was to investigate the phase, compositional, and morphological changes of Er:YAG laser-irradiated dentin. BACKGROUND DATA: To date, nothing comprehensive has been reported about the phase and compositional changes of human dentin after Er:YAG laser irradiation. METHODS: The human dentin was irradiated by Er:YAG laser with irradiation energies from 300 mJ/pulse-10 pps-10 sec to 700 mJ/pulse-10 pps-10 sec with and without water spray. After irradiation, the specimens were analyzed by means of x-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). RESULTS: After exposure to Er:YAG laser, dentin showed no phase changes on the x-ray diffractometer. In Fourier transform infrared analysis, two absorption bands at 2200 and 2015 cm(-1) could be traced on dentin treated by Er:YAG laser with irradiation energies beyond 300 mJ/pulse-10 pps-10 sec and without water spray. The OH(-) band disappeared at 1630 cm(-1). Scanning electron micrographs revealed that laser energy of 500 mJ/pulse-10 pps-10 sec was sufficient to prompt melting and recrystallization of dentin crystals. CONCLUSIONS: Our study demonstrated that Er:YAG laser irradiation on dentin with water spray would not significantly change the structure and composition. Therefore, water cooling is important for reducing the thermal effect of Er:YAG laser.

Dentin↗

PubMed2004

Morphologic study of Nd:YAG laser usage in treatment of dentinal hypersensitivity.

Our previous in vitro study indicated that Nd:YAG laser irradiation on dentin could melt normal dentin surface and close the exposed dentinal tubule orifices without creating surface cracks. This study evaluated the morphologic changes of hypersensitive dentin after Nd:YAG laser irradiation. Thirty patients with clinically diagnosed cervical dentin hypersensitive teeth were treated with a Nd:YAG laser of 30 mJ intensity at 10 pulses per second for 2 min. An impression of the sensitive area was taken before and after laser treatment and then examined with a scanning electron microscope. The impression of the dentin surface after Nd:YAG laser treatment showed no protrusive rods, in contrast with the presence of numerous rods before laser irradiation. Because protrusive rods are a measure of open dentinal tubules, we interpret these data to support the hypothesis that Nd:YAG laser irradiation at specifications of 30 mJ, 10 pulses per second, and 2 min can be used to seal the exposed dentinal tubules.

Adolescent↗

PubMed2003

Auto-fluorescence spectra of oral submucous fibrosis.

BACKGROUND: Oral submucous fibrosis (OSF) is a chronic oral mucosal disease characterized by progressive deposition of collagen in the subepithelial connective tissue and epithelial atrophy. Previous studies have shown that at 330-nm excitation, the 380- and 460-nm emission peaks of the auto-fluorescence spectra for oral mucosal tissues reflect the collagen content in the subepithelial connective tissue and the nicotinamide adenine dinucleotide phosphate (NADH) content in the epithelial cells, respectively. Therefore, at 330-nm excitation OSF mucosa may have a higher 380-nm emission peak and a lower 460-nm emission peak than the normal oral mucosa (NOM). METHODS: To test the above hypothesis, we measured the in vivo auto-fluorescence spectra of 59 OSF mucosal sites and compared the measured spectra with auto-fluorescence spectra obtained from 15 NOM samples from 15 healthy volunteers, five samples of friction hyperkeratosis (histologic diagnosis, hyperkeratosis and acanthosis) on OSF buccal mucosa (FHOSF), and 29 samples of oral leukoplakia (histologic diagnosis, hyperkeratosis and acanthosis) on OSF buccal mucosa (OLOSF). RESULTS: We found that the spectrum of the OSF mucosa had a significantly higher 380-nm emission peak and a significantly lower 460-nm emission peak than the spectra of NOM, FHOSF, and OLOSF samples. When the mean (+/-SD) fluorescence intensities at 380 +/- 15 nm (I380 +/- 15 nm) and 460 +/- 15 nm (I460 +/- 15 nm) emission peaks and the mean ratio of I460 +/- 15 nm/I380 +/- 15 nm were compared between groups, we found that OSF group had a significantly higher mean value of I380 +/- 15 nm, a significantly lower mean value of I460 +/- 15 nm, and a significantly lower mean ratio of I460 +/- 15 nm/I380 +/- 15 nm than the NOM, FHOSF, and OLOSF groups (P < 0.001). However, no significant differences in the mean values of I380 +/- 15 nm, I460 +/- 15 nm, and ratio of I460 +/- 15 nm/I380 +/- 15 nm were found between NOM and FHOSF or OLOSF samples as well as between FHOSF and OLOSF samples (P > 0.05). CONCLUSION: Because OSF mucosa has a very unique pattern of auto-fluorescence spectrum, we conclude that auto-fluorescence spectroscopy is a good method for real-time diagnosis of OSF.

Adolescent↗

PubMed2003

Bond strengths of orthodontic bracket after acid-etched, Er:YAG laser-irradiated and combined treatment on enamel surface.

Laser ablation has been proposed as an alternative method to acid etching: however, previous studies have obtained contrasting results. The purpose of this study was to compare the bond strengths after acid etching, laser ablation, acid etching followed by laser ablation, and laser ablation followed by acid etching. Forty specimens were randomly assigned to one of the four groups. Two more specimens in each group did not undergo bond test and were prepared for observation with scanning electron microscope (SEM) after the four kinds of surface treatment. After the bond test, all specimens were inspected under the digital stereomicroscope and SEM to record the bond failure mode. Student's t-test results showed that the mean bond strength (13.0 +/- 2.4 N) of the laser group was not significantly different from that of the acid-etched group (11.8 +/- 1.8 N) (P > .05). However, this strength was significantly higher than that of the acid-etched then laser-ablated group (10.4 +/- 1.4 N) or that of the laser-ablated then acid-etched group (9.1 +/- 1.8 N). The failure modes occurred predominantly at the bracket-resin interface. Er:YAG laser ablation consumed less time compared with the acid-etching technique. Therefore, Er:YAG laser ablation can be an alternative tool to conventional acid etching.

Acid Etching, Dental↗

PubMed2003

Repair of perforating internal resorption with mineral trioxide aggregate: a case report.

A case of internal resorption with buccal perforation was found in a maxillary central incisor. Because of the extensive lesion and continuous exudation, surgical intervention was used. The apical third was obturated with gutta-percha, and the perforated lesion was repaired with mineral trioxide aggregate. The residual canal space was filled by thermoplasticized gutta-percha technique, and the coronal cavity was restored with composite resin. The symptoms and signs ceased, and the results were satisfactory at 1-year follow-up.

Adult↗

PubMed2003

Nitric oxide promotes infectious bone resorption by enhancing cytokine-stimulated interstitial collagenase synthesis in osteoblasts.

This experiment was undertaken to determine the role of macrophage-derived nitric oxide (NO) in mediating lipopolysaccharide (LPS)-induced bone resorption by using an in vitro co-culture system and an in vivo model of infectious bone resorption. Our results demonstrated that LPS stimulated the expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor (TNF)-a mRNAs and nitrite synthesis in the J774 mouse macrophage cell line but not in the UMR-106 (rat) and MC3T3-E1 (mouse) osteoblast cell lines. Conditioned media (CM) from LPS-stimulated J774 triggered only low to moderate levels of iNOS mRNAs in MC3T3-E1 and a trivial effect in UMR-106. On the other hand, CM induced matrix metalloproteinase-1 (MMP-1) gene expression in both osteoblast cell lines. The NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA) did not alter this effect in MC3T3-E1 and UMR-106, whereas TNF-a antibody diminished the CM-induced MMP-1 gene expression in both cell lines. Interestingly, SNAP, a NO donor, although by itself is not a MMP-1 stimulator for UMR-106, augmented the TNF-alpha-stimulated MMP-1 mRNA production in UMR-106. In a J774/UMR-106 co-culture system, LPS stimulated significant MMP-1 gene expression in UMR-106, and this upregulation was abolished by L-NMMA and TNF-alpha antibodies. Immunohistochemical analysis in a rat model of infectious bone resorption (periapical lesion) showed co-distributions of iNOS+ macrophages and MMP-1+ osteoblasts around the osteolytic areas. Administration of L-NMMA markedly reduced the extent of bone loss and the percentage of MMP-1-synthesizing osteoblasts. These data suggest that NO derived from macrophages after LPS stimulation may enhance bone loss by augmenting the cytokine-induced MMP-1 production in osteoblasts.

3T3 Cells↗

PubMed2002

Sequential expressions of MMP-1, TIMP-1, IL-6, and COX-2 genes in induced periapical lesions in rats.

To elucidate the pathogenesis of periapical lesion-associated bone resorption, a disease model of Wistar rat molar was employed. After lesion induction, the mRNAs encoding for matrix metalloproteinase-1 (MMP-1), tissue inhibitor of metalloproteinase-1 (TIMP-1), interleukin-6 (IL-6), and cyclooxygenase-2 (COX-2) in the developing lesions were detected by in situ hybridization at day 5, 10, 15 and 20, respectively. At day 5, MMP-1, IL-6 and COX-2 mRNAs appeared predominantly in macrophages. During day 15 to day 20, increased expressions of these mediators were also found in osteoblasts but to a lesser extent compared with those in macrophages. MMP-1 mRNA was also detected in osteoclasts. In contrast, expression of the TIMP-1 gene was noted primarily in osteoblasts and was less pronounced compared with that of MMP-1. The mediator-expressing cells aggregated in the vicinity of bone resorption areas and their numbers increased with time. These data suggest that macrophages and osteoblasts are involved in the development of periapical lesions, and that they promote bone resorption by producing MMP-1, IL-6 and COX-2. In addition, administration of a specific COX-2 inhibitor, meloxicam, reduced the extent of periapical bone resorption by 43% and simultaneously diminished the numbers of cells synthesizing MMP-1 and IL-6 mRNAs. These results further elucidate the significance of COX-2 in disease progression of periapical lesions as it modulates indirectly the production of MMP-1 and IL-6.

Animals↗

PubMed2002

Cyclic fatigue of endodontic nickel titanium rotary instruments: static and dynamic tests.

Endodontic instruments upon rotation are subjected to both tensile and compressive stress in curved canals. This stress is localized at the point of curvature. The purpose of this study was to evaluate the cyclic fatigue of 0.04 ProFile nickel titanium rotary instruments operating at different rotational speeds and varied distances of pecking motion in metal blocks that simulated curved canals. A total of 150 ProFile instruments were made to rotate freely in sloped metal blocks at speeds of 200, 300, or 400 rpm by a contra-angle handpiece mounted on an Instron machine. The electric motor and Instron machine were activated until the instruments were broken in two different modes, static and dynamic pecking-motion. The fractured surfaces of separated instruments were examined under a scanning electron microscope. All data obtained were analyzed by a stepwise multiple regression method using a 95% confidence interval. The results demonstrated that the time to failure significantly decreased as the angles of curvature or the rotational speeds increased. However, as pecking distances increased, the time to failure increased. This is because a longer pecking distance gives the instrument a longer time interval before it once again passes through the highest stress area. Microscopic evaluation indicated that ductile fracture was the major cyclic failure mode. To prevent breakage of a NiTi rotary instrument, appropriate rotational speeds and continuous pecking motion in the root canals are recommended.

Compressive Strength↗

PubMed2002

In vitro effect of laser irradiation on cementum-bound endotoxin isolated from periodontally diseased roots.

BACKGROUND: In a previous study, we evaluated the in vivo effects of an Nd:YAG laser on periodontal disease by measuring crevicular interleukin (IL)-1beta levels before and after laser application. It was found that laser therapy was less effective than traditional scaling and root planing. These results might be due to incomplete removal of microbial residues and cementum-bound endotoxin on root surfaces by the laser. In this study, we explored the in vitro effectiveness of an Nd:YAG laser for the elimination of cementum-bound endotoxin by measuring IL-1beta changes in stimulated monocytes. METHODS: Fresh human monocytes were harvested from adults without periodontitis and grown in RPMI 1640 medium. Diseased cementum particles were collected and prepared from teeth with untreated periodontitis and were irradiated with 5 levels of laser energy. Cementum particles were subjected to endotoxin testing by a limulus amebocyte lysate (LAL) assay and then were incubated with cultured monocytes. Production of IL-1beta in stimulated monocytes was measured by enzyme-linked immunosorbent assay and quantified by spectrophotometry. RESULTS: The endotoxin unit (EU) of diseased cementum was 18.4 EU/mg, which seemed to be remarkably lower than that of common periodontal pathogens including Porphyromonas gingivalis (381) at 15,300 EU/mg/ml, Prevotella intermedia (ATCC 25611) at 227 EU/mg/ml, and Fusobacterium nucleatum (ATCC 25586) at 1,987 EU/mg/ml. Monocytes subjected to stimulation by diseased cementum particles without laser irradiation produced 124 to 145 pg/ml IL-1beta, 9- to 18-fold higher than that of unstimulated monocytes (7.07 to 15.95 pg/ml). Diseased cementum particles after irradiation with various energy levels of the Nd:YAG laser could still stimulate monocytes to secrete 89 to 129 pg/ml IL-1beta. No statistically significant difference was found in the production of IL-1beta induced by diseased-bound cementum with or without laser irradiation. CONCLUSIONS: The Nd:YAG laser varying from 50 mJ, 10 pps to 150 mJ, 20 pps, for 2 minutes, did not seem to be effective in destroying diseased cementum endotoxin.

Adult↗

PubMedDate not supplied

Cytotoxicity of conventional and modified glass ionomer cements.

Various glass ionomer cements (GICs) and resin-modified GICs are widely used as tooth-colored restorative materials. However, their potential effects on pulp tissues are not fully understood. In this study, the authors compared the toxicity of nine types of GICs on cultured human dental pulp cells. Exposure of pulp cells to GICs for five days led to differential growth inhibition as analyzed by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Exposure of pulp cells to ProTec CEM, Fuji II LC, Compoglass and GC Lining cement for five days decreased the cell numbers to 11%, 12%, 19% and 25%, respectively, of the control. Exposure of pulp cells to Fuji IX, GIC FX and Fuji II SC also decreased cell numbers by 62%, 33% and 24%, respectively. By contrast, Hy-Bond and Fuji I showed only mild suppression on the growth of pulp cells, with 12% and 16% decreased cell numbers. Morphologically, marked retraction and rounding of pulp cells were noted following exposure to GC Lining cement; in addition, cell surface blebbing was noted following exposure to Compoglass, Fuji II LC and ProTec CEM. Exposure of the pulp cells to Fuji II SC and Fuji IX, however, led to decreases in the cell density, with no obvious morphological changes. These results indicate that resin-modified GICs, such as Compoglass, Fuji II LC, ProTec CEM and GC Lining cements, are more toxic to pulp cells than conventional GICs. It is not recommended that resin-modified GICs be directly applied onto dental pulp cells. However, additional in vivo studies are needed to evaluate the potential toxicities of these resin-modified GICs during clinical operative procedures.

Analysis of Variance↗