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Biomedical subjects

W N Wang

Publications and source records attributed to W N Wang.

At least 19 recordsLinked to original sources

Postgraduate year does not influence operating time in laparoscopic cholecystectomy.

BACKGROUND: Surgical resident education may contribute to increased operating time, thus increasing costs at teaching institutions. It is possible that junior residents, in particular, with less experience could contribute to longer operating times for laparoscopic cholecystectomy. We hypothesized that all general surgery residents, regardless of level of training and with proper supervision, could complete a laparoscopic cholecystectomy in a safe and timely fashion. MATERIALS AND METHODS: A retrospective study was performed using data collected from laparoscopic cholecystectomies completed under the supervision of one attending surgeon over a 2-year period. Operating times were recorded, the operating surgeon was identified, and cases were assigned an acuity level based on pathologic findings. Operative times were compared after dividing surgeons into three groups (junior residents, senior residents, and staff). RESULTS: Seventy-one cases were entered into the study. There were no differences when comparing mean operating times among the three groups (P = 0.2, analysis of variance). The pathologic acuity in each group was similar (P = 0.8, Fisher's exact test). There was a difference when evaluating the operating times for the pathologic level of acuity (P = 0.002, Kruskal-Wallis test). CONCLUSIONS: Resident level does not affect the operating time in performing laparoscopic cholecystectomy. The pathologic acuity of the gallbladders was distributed similarly for all three groups. There was a difference in mean operating time based on pathologic acuity. Laparoscopic cholecystectomy can be performed in a safe and efficient manner at a teaching institution.

Acute Disease↗

Effect of pH and Zn(2+) on subcultured muscle cells from Macrobrachium nipponense.

A cell culture system was devised for muscle cell of Macrobrachium nipponense in the study. The juvenile and adult shrimps were held in laboratory aquaria with penicillin 1000 IU/ml and streptomycin 1000 microg/ml for 12-24 hours. Cell cultures were established in medium 199 supplemented with 20% fetal bovine serum, 1 g/L glucose, 5.2 g/L NaCl, 1.43 g/L CaCl(2), 0.05 g/L MgCl(2), 100 IU/mL penicillin and 100 microg/ml streptomycin. Fibroblast-like cells were passaged up to three times and survived for 54 days. The results showed the optimum for subculture in vitro was in medium 199 with pH 7.6. Moreover, basal medium supplemented with Zn(2+) 60 microg/L could enhance the growth of the muscle cells. It was found that better results for cell culture would be obtained more easily with juvenile shrimps caught in spring than adults in summer or autumn; and shrimps caught within 12 hours after ecdysis could grow much better than the intermoult shrimps.

Animals↗

Bond strength with APF applied after acid etching.

One tenet of successful orthodontic therapy is to complete treatment without decalcification, hypocalcification, or discoloration of the natural dentition. Fluoride application has been shown to reduce demineralization of enamel. The purpose of this study was to see if fluoride could be incorporated into enamel before orthodontic bracketing without adversely affecting bond strength. Forty extract adolescent human premolars were randomly divided into two equal groups with 20 teeth each. Group 1 served as control group, and group 2 (experimental) was immersed in 1.23% acidulated phosphate fluoride for 4 minutes after acid etching. The buccal surfaces of all 40 teeth were then bonded with the same type of metal bracket and debonded with an Instron machine. The debonding interface was observed with scanning electron microscopy (SEM). The mapping was calculated with energy dispersive x-ray spectrometry. The results showed that the bond strength of group 1 was significantly greater than that of group 2. The enamel detachment (enamel fracture) was found in the experimental group only. Although the application of acidulated phosphate fluoride to a tooth can prevent dental decay or decalcification, the bond strength decreases and enamel detachment is found after debonding. The result shows that the application of acidulated phosphate fluoride after acid etching enamel has an adverse effect on orthodontic bond strength of human enamel.

Acid Etching, Dental↗

Fluoridated etching on orthodontic bonding.

Enamel demineralization that occurs adjacent to directly bonded orthodontic attachments is of great concern to orthodontists. One procedure suggested to overcome this problem is to use fluoride treatment in an acid etch. The purpose of this study was to evaluate the bond strength and the debonding interface distribution of adhesive, with and without the use of fluoridated etch on enamel, before bonding. Ten teeth were etched with 37% phosphoric acid (H3PO4), incorporated with 1.23% sodium fluoride (NaF) for 15 seconds. The control group of 10 teeth was etched with the 37% H3PO4 solution for 15 seconds without fluoride. Fluoride on enamel was first detected with scanning auger microscribe/photoelectron spectroscopy in the fluoridated etching group. The brackets were then bonded on the labial surfaces of the crowns of both groups of teeth. The bracketed teeth were tested, with an Instron machine, to determine the tensile bond strength, as well as with a scanning electron microscope, and by mapping with an energy dispersive x-ray spectrometer to detect the debonding interfaces. The results showed that the fluoride was found on the enamel after fluoridated etching for 15 seconds. The bond strength and debonding interface distribution between the two groups were not statistically significantly different. Enamel detachment was not present in either group. Hence, the fluoridated etching with 1.23% NaF may have a clinical application in the prevention of demineralization or caries surrounding and under orthodontic brackets bonded to enamel.

Acid Etching, Dental↗

Bond strength: a comparison between chemical coated and mechanical interlock bases of ceramic and metal brackets.

Two types of chemically coated bases, two types of mechanical interlock base polycrystalline ceramic brackets, as well as one type of mechanical interlock base metal bracket were selected for bonding with Concise orthodontic resin on 60 extracted premolars. Bond strength was measured with an Instron testing machine and the debonded interface and enamel detachment were examined with scanning electron microscope and energy dispersive x-ray spectrometer. The results showed the greater bond strength with a chemically coated base of ceramic brackets had a greater debonded interface between enamel and resin, and the weaker bond strength of mechanical interlock base of ceramic and metal brackets had a greater debonded interfaces between bracket and resin. There was no significant statistical difference in bond strengths with mechanically interlock bases between ceramic and metal brackets. The enamel detachment was found on only the stronger bond strength in which there was a chemically coated base on the ceramic bracket. Ceramic bracket fractures were not found during debonding in this specially designed specimen with 1 mm/min speed of crosshead. The mechanical interlock base of the ceramic bracket combines the strength, durability and retention of a metal bracket along with an aesthetic advantage and no enamel detachment after debonding.

Adolescent↗

Orthodontic resin under water immersion.

The absorption and desorption of water by a polymer matrix of composite orthodontic resin could cause debonding of the filler-matrix or hydrolytic degradation of fillers and loss of bond strength. In this study, the bond strength of brackets directly bonded with orthodontic composite to the enamel surface of premolars was measured with an Instron machine; the debonding interface distribution was analyzed by scanning electron microscope and energy dispersive x-ray spectrometry following water immersion for 1, 2, and 3 days, and 1, 2, 4, 8, 16, 24, and 32 weeks, respectively. The results show that, under water immersion, bond strength may gradually weaken over time. The greatest loss occurs initially, followed by a period of relative stabilization, and then a weaker reduction after 24 weeks. The greater the time in water immersion, the less the bond strength and the greater the destruction of the composite resin. The debonding interface occurs between bracket and resin.

Absorption↗

Effect of H3PO4 concentration on bond strength.

Prior to bonding, the enamel surface of the tooth is normally etched using a solution of 37%-50% phosphoric acid (H3PO4) for 60 seconds. The purpose of this study was to evaluate the tensile bond strength, debonding interface distribution and enamel surface detachment of various concentrations of H3PO4 solution, from 2% to 80%, applied for 15 seconds. Statistically significant differences in bond strength were found among the various concentrations tested: concentrations in the 10% to 60% range produced greater bond strengths than both the weaker and stronger concentrations. The weaker the bond strength, the greater the debonding interface between resin and enamel. The greater the bond strength, the greater the debonding interface between the bracket and resin. Enamel detachment occurred as the H3PO4 concentration rose above 30%. To obtain greater bond strength and less enamel detachment, 10%-30% concentrations of phosphoric acid for 15 seconds etching are suggested for clinical bonding.

Acid Etching, Dental↗

Force decay of elastomeric chain--a serial study. Part II.

This study was designed to evaluate the relaxation of elastomeric chain over time. The purposes were to compare the force decay curves of three variously stretched lengths, as well as to compare transparent and grey elastomeric chains. The elastomeric chains were fixed on a stainless steel framework that was submerged in 37 degrees C water bath for 6 weeks. The elastic forces of the chains were measured by a Dial-Type dynamometer, and recorded at the initial activation, first hour, eighth hour, twenty-fourth hour, third day, and then weekly to 6 weeks. The stretched length of the chains were decreased 0.5 mm per week. The results showed: (1) The sequence of stretch force at each time measurement of the Rocky Mountain clear energy chain was 40 mm > 35 mm > 30 mm. However, the percentage of remaining force was 40 mm < 35 mm < 30 mm. (2) The remaining force and the percentage of remaining force of the American Orthodontic short transparent chain were greater than the remaining force of the gray chain. (3) The remaining force and the percentage of remaining force of the Rocky Mountain clear chain with 40 mm stretch were greater than that of the American Orthodontic transparent and grey chains. (4) The effective force for canine retraction (184 gm) can be maintained by the Rocky Mountain energy chain with 40 mm, 35 mm, and 30 mm stretch for about 3 weeks, 1 week, and 3 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

Comparison of bond strength between lingual and buccal surfaces on young premolars.

The purpose of this experiment was to compare the bond strength and the failure interfaces on lingual and buccal surfaces of young human premolars. Premolar buccal brackets were adapted and bonded on the lingual or buccal surfaces of crowns after etching with a 37% phosphoric acid solution for 15 seconds. The bond strengths were 7.2 MPa and 7.0 MPa for lingual and buccal surfaces, respectively. The bond failure interfaces were located between the bracket and the resin, within the resin itself, or between the resin and the enamel. Tooth fragmentation was not found. There were no statistically significant differences (p > 0.05). This indicates that it is not necessary to specially treat a lingual surface for increasing the bond strength.

Adolescent↗

Bond strength of younger and older permanent teeth with various etching times.

The purpose of this study was to analyze the tensile bond strength and debonding failure mode in younger and older permanent teeth after etching for 15 and 60 seconds. Bond strength did not change significantly when etching time was increased from 15 to 60 seconds in younger or older permanent teeth. However, regardless of etching time, the bond strength of the older permanent teeth was greater than that of the younger teeth with statistically significant differences. Four types of debonding interface were found; bracket base-resin, within the resin, resin-enamel and enamel detachment. There were no statistically significant differences noted among younger and older permanent teeth with 15 or 60 second etching fracture mode incidence at debondings. Enamel detachment was found only at etching times of 60 seconds. To reduce enamel destruction and save chair time, 15 second etching on either younger or older permanent teeth is suggested.

Acid Etching, Dental↗

A study of bond strength between light- and self-cured orthodontic resin.

Light-cured orthodontic composite resin has been widely advertised recently for use in bonding. However, the curability of light-cured resin when light waves are diffused through metal, ceramic, or resin brackets is doubtful and questionable. This study evaluated the effectiveness of a visible light source in curing the resin under a solid metal bracket, compared the tensile bond strength at different exposures, and analyzed the broken interface distribution between light-cured resin with various light exposure times and self-cured resin. The bond strength results revealed that the difference between light-cured resin (Transbond) with 60, 40, and 20 seconds of light exposure, respectively, and self-cured resin (Concise) was 1.05, 0.92, 0.61, and 0.71 kg/mm2, respectively. The bond strength of Transbond with 60 and 40 seconds of light exposure was greater than both the bond strength of Transbond with 20 seconds of light exposure and the strength of the self-cured resin of Concise, with statistical significance (p less than 0.01). There were also no statistical differences between Transbond with 60 and 40 seconds of light exposure or Transbond with 20 seconds of light exposure and Concise. The bond failure interfaces were located between the bracket and the resin, within the resin itself, or between the resin and the enamel. Tooth fragmentation was rarely found. There were no statistical differences (p greater than 0.05) among broken interfaces. This indicates that visible light is powerful in curing the visible light-activated composite resin under solid metal brackets.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗

Bond strength with various etching times on young permanent teeth.

Tensile bond strengths of an orthodontic resin cement were compared for 15-, 30-, 60-, 90-, or 120-second etching times, with a 37% phosphoric acid solution on the enamel surfaces of young permanent teeth. Fifty extracted premolars from 9- to 16-year-old children were used for testing. An orthodontic composite resin was used to bond the bracket directly onto the buccal surface of the enamel. The tensile bond strengths were tested with an Instron machine. Bond failure interfaces between bracket bases and teeth surfaces were examined with a scanning electron microscope and calculated with mapping of energy-dispersive x-ray spectrometry. The results of tensile bond strength for 15-, 30-, 60-, or 90-second etching times were not statistically different. For the 120-second etching time, the decrease was significant. Of the bond failures, 43%-49% occurred between bracket and resin interface, 12% to 24% within the resin itself, 32%-40% between resin and tooth interface, and 0% to 4% contained enamel fragments. There was no statistical difference in percentage of bond failure interface distribution between bracket base and resin, resin and enamel, or the enamel detachment. Cohesive failure within the resin itself at the 120-second etching time was less than at other etching times, with a statistical significance. To achieve good retention, to decrease enamel loss, and to reduce moisture contamination in the clinic, as well as to save chairside time, a 15-second etching time is suggested for teenage orthodontic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗

Evaluation of the sealant in orthodontic bonding.

In the two-paste self-polymerizing orthodontic bonding systems, sealants are routinely used to protect enamel, to decrease marginal leakage, to enhance bond strength, and to increase interfacial permeability for the etched enamel, the bonding resin, and the bracket base. However, some studies have questioned the need for the sealant. Bond strengths with and without sealants in orthodontic bonding were compared in this study. The results indicated no statistical differences between the tensile bond strengths of the two evaluated groups. The distributions of debonding interface between groups were similar and also had no statistical difference. This study therefore indicated that use of the sealant in the two-paste orthodontic bonding system for enhanced strength is unnecessary. However, the use of a sealant may offer extra protection to the enamel during debonding procedures.

Acrylic Resins↗

The effect of pretreatment with fluoride on the tensile strength of orthodontic bonding.

White spot decalcifications and caries occurring adjacent to bonded orthodontic brackets have long been a concern to orthodontists. One procedure suggested to overcome this problem is fluoride treatment prior to bonding. The purpose of this study was to compare the tensile bond strength of orthodontic self-cured resin from Concise on teeth rinsed 4 minutes in 1.23% APF with untreated controls. Measurements were made on an Instron machine. Debonding interfaces were observed with a scanning electron microscope and energy dispersive x-ray spectrometry. Distributions were calculated. The tensile bond strengths of the fluoride-treated teeth and the untreated teeth were not significantly different. The debonding interfaces between resin and bracket base, within the resin itself, and between enamel and resin were similar in the two experimental groups. However, greater enamel detachment was seen within the fluoride pretreatment group. So while fluoride pretreatment does not significantly affect tensile bond strength, it may cause enamel detachment after debonding.

Acid Etching, Dental↗

[A study on mechanism of skin penetration by cercaria of S. japonicum and screening of preventive drugs].

Mice pretreated with PG cyclo-oxygenase inhibitor aspirin, at 300 mg/kg/d x 5, and ibuprofen, at 100 mg/kg/d x 5 orally and 20 mg/kg/d x 3 intraperitoneally revealed moderate chemoprophylactic effects and the reduction of the penetration of worms by 23% when compared to controls. Daily oral administration of aspirin, at 300 mg/kg for 15 days the worms reduction increased to 41.7%. In estimation of PGE1 in cercariae of S. japonicum by radioimmunoassay, the PGE1 was 49 pg/100 cercariae. In normal mouse skin PGE1 has been measured to amount to 3105 +/- 691.7 pg/10 mg on average. In cercarial penetrated mouse skin, 1.5 hours after exposure the PGE1 assessed in 100 and 250 cercariae in the infected skin were 5506 +/- 1127.1 and 12085 +/- 2622.9 pg/10 mg respectively, which were significantly higher than that of the non-penetrated skin. These studies in conjunction with our previous work indicate that: 1.PGs, similar to S. mansoni, were probably necessary for cercarial penetration. 2.PG inhibitors could reduce cercarial penetration. Receptors antagonist etc. e.g. diphenhydramine, chlorpheniramine, atropine, practolol could not reduce cercarial penetration, but praziquantel in the pretreated mice could reduce cercarial penetration significantly. e.g. 400 mg/kg orally 2 hours prior to affection of cercariae about 100% reduction of the penetration, but if pretreated with praziquantel, 4, 8, 24, 36 hours prior to the affection the reduction penetration decreased to 51.7, 46.1, 9.4, 8.9% respectively.

Alprostadil↗

Tensile bond strength of orthodontic resins on the human tooth surface.

Composite resin has been used in the field of orthodontics for more than twenty years. Although there have been many studies and discussions regarding the bond strength of orthodontic brackets to the human tooth surface, a definitive conclusion has not yet been established. In this study, sixty bicuspids extracted from teenagers were employed for testing, in conjunction with 6 different brands of orthodontic resins: Concise, Unitek, Ormco, American, Mono-lok and Right-on. On the buccal surface of the crown, the tensile bond strength for the various resins were tested and recorded. The bond strength was 0.69 kg/mm2 for Concise, 0.64 kg/mm2 for Unitek, 0.58 Kg/mm2 for Ormco, 0.55 kg/mm2 for American, 0.54 kg/mm2 for Mono-log and 0.45 kg/mm2 for Right-on, respectively. The broken surfaces were examined by scanning electron microscopy, as well as energy dispersive x-ray spectrometry. The broken surfaces were either at interface between the resin and bracket base, at the resin itself, interface between tooth surface and resin or in a combination of them. On the broken surface of the bracket base, components of broken tooth fragments were also detected. The percentage for the frequency of samples of each type of orthodontic resin of broken tooth fragments found was 30% for Concise, 10% for Unitek, 50% for Ormco, 40% for American, 50% for Mono-lok and 80% for Right-on.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗