[Cytopathological characteristics of SMARCA4-deficient thoracic undifferentiated tumors in serous effusion]

Objective: To investigate the clinicopathological characteristics of SMARCA4-deficient thoracic undifferentiated tumors, and the diagnostic value of the cells in serous effusion. Methods: Eleven cases of SMARCA4-deficient tumor were collected from the Affiliated Hospital of Hebei University, China from January 2018 to July 2023, which were diagnosed using cell block of serous effusion. The clinical, histopathological, immunohistochemical and molecular genetic features were reviewed, along with related literature. Results: All the 11 patients were males with ages ranging from 54 to 77 years (median 64 years). Nine patients were smokers and two had an unknown smoking history. Most of them complained of cough and dyspnea with pleural effusion. The primary tumor sites included lung (9 cases), thoracic wall (1 case), and mediastinum (1 case), while 3 patients had a history of lung surgery. Histologically, tumor cells were large and pleomorphic, with increased nuclear-cytoplasmic ratio. They also showed round nuclei, conspicuous nucleoli, and basophilic cytoplasm in serous effusion. Immunohistochemically, tumor cells in all cases were negative for SMARCA4/BRG1, CKpan and CK7, but positive for SMARCB1/INI1. Some of the cases were positive for CD34 (7/11), synaptophysin (4/11) and SALL4 (2/11). Histologically, monotonous tumor cells formed solid sheets or anastomosing islands with poor cell adhesion and rhabdoid morphology. Brisk mitotic figures were accompanied by large areas of necrosis. Some cases focally exhibited syncytia, and some had bright cytoplasm and vesicular chromatin. The immunohistochemical profiles in the tumor tissues were consistent with those of cytology. Six cases were negative for PD-L1 (22c3). Among the 6 cases analyzed by targeted next generation sequencing, concurrent SMARCA4 and TP53 mutations were detected in all 6 cases. Some of the 6 tumors showed mutations of STK11, CDKN2A, and MET, and amplification of ERBB2, exon deletion of BRCA2, etc. Follow-up information was available in all cases and ranged from 2 to 24 months. The patients showed metastases to various sites, including lymph node, liver, kidney, adrenal gland, brain, bone and other sites. Four patients died of the tumor. The survival time of 4 patients who underwent radical resection or radiofrequency ablation was more than 13 months. Conclusions: SMARCA4-deficient thoracic sarcoma is a rare but highly aggressive tumor with dismal prognosis and rhabdomyoid features. It is difficult to diagnose this disease using only serous effusion samples. This tumor thus warrants careful consideration. Accurate diagnosis can greatly improve early diagnosis and treatment of these tumors.

Glucosamine: fructose-6-phosphate amidotransferase in the white shrimp Litopenaeus vannamei: characterization and regulation under alkaline and cadmium stress

Heavy metal residues and chemical contaminators considered as relevant sources of aquatic environmental pollutants have a generally immunosuppressive effect on aquatic organisms, depressing metabolic activities and immune response. Glutamine: fructose-6-phosphate aminotransferase (GFAT, EC2.6.1.16) is the first, and rate-limiting, enzyme in the hexosamine biosynthetic pathway, and is involved in the regulation of chitin biosynthesis and glycosylation of proteins. We have isolated and characterized GFAT from the white shrimp Litopenaeus vannamei. Amino acid sequence similarity of the Lv-GFAT (L.vannamei-GFAT) was highest to GFATs isolated from insects and mammals (83 % similarity to that of Haemaphysalis longicornis). The open-reading frame of the Lv-GFAT codes for a protein of 41.6 kDa with a calculated isoelectric point of 5.03. RT-PCR assays showed that endogenous Lv-GFAT mRNA is most strongly expressed in the intestine. Further analysis of Lv-GFAT gene expression in hepatopancreas by quantitative real-time PCR demonstrated that Lv-GFAT transcript levels increased when the shrimp were exposed to alkaline pH (9.3) and cadmium stress, but the time when its mRNA expression level peaked differed under these stresses. We also first expressed the recombinant protein of GFAT from shrimps in Escherichia coli. Western blot analyses confirmed that the Lv-GFAT protein was strongly expressed in the hepatopancreas after exposure to the LC-Cd stress. These results suggest that Lv-GFAT expression is stimulated by alkaline pH and cadmium stress and that it may play important roles in resistance of shrimp to environmental stresses.

Protective effects of hydrogen-rich medium on lipopolysaccharide-induced monocytic adhesion and vascular endothelial permeability through regulation of vascular endothelial cadherin

We observed the effect of hydrogen-rich medium on lipopolysaccharide (LPS)-induced human umbilical vein endothelial cells (HUVECs), hyaline leukocyte conglutination, and permeability of the endothelium. Endotheliocytes were inoculated on 6-well plates and randomly divided into 4 groups: control, H2, LPS, LPS+H2, H2, and LPS+H2 in saturated hydrogen-rich medium. We applied Wright's stain-ing to observe conglutination of hyaline leukocytes and HUVECs, flow cytometry to determine the content of vascular cell adhesion protein 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1), enzyme-linked immunosorbent assay to measure the E-selectin concentration in the cell liquor, the transendothelial electrical resistance (TEER) to test the permeability of endothelial cells, and Western blot and immunofluorescence to test the expression and distribution of vascular endothelial (VE)-cadherin. Compared with control cells, there was an increase in endothelium-hyaline leukocyte conglutination, a reduction in VCAM-1, ICAM-1, and E-selectin, and the TEER value increased obviously. Compared with LPS, there was an obvious reduction in the conglutination of LPS+H2 cells, a reduction in VCAM-1, ICAM-1, and E-selectin levels, and a reduction in the TEER-resistance value, while the expression of VE-cadherin increased. Fluorescence results showed that, compared with control cells, the VE-cadherin in LPS cells was in-complete at the cell joints. Compared with LPS cells, the VE-cadherin in LPS+H2 cells was even and complete at the cell joints. Liquid rich in hydrogen could reduce LPS-induced production of adhesion molecules and endothelium-hyaline leukocyte conglutination, and influence the expression and distribution of VE-cadherin to regulate the permeability of the endothelium.

Negative appendicectomy rate as a quality metric in the management of appendicitis: impact of computed tomography, Alvarado score and the definition of negative appendicectomy

INTRODUCTION

The negative appendicectomy rate (NAR) is a quality metric in the management of appendicitis. While computed tomography (CT) has been associated with a low NAR, Alvarado scoring produces an acceptable NAR. The definition of negative appendicectomy may affect the NAR. This study examined the impact of CT, Alvarado score and definition on the NAR.

METHODS

The charts of 1,306 emergency appendicectomy patients from 1996 to 2010 were reviewed. Three five-year cohorts were created (Cohort A: 1996-2000, Cohort B: 2001-2005, Cohort C: 2006-2010) and the NAR was calculated for each cohort using two definitions of negative appendicectomy: absence of inflammation (NAR-STD) and absence of intramural neutrophils (NAR-STR). NAR-STD was correlated to the CT rate for Cohorts B and C and also to Alvarado score for Cohort C.

RESULTS

When the definition of negative appendicectomy was changed, the NAR rose from 9.2% to 15.8% (p=0.0097) for Cohort A, from 2.8% to 8.6% (p=0.0180) for Cohort B (CT rate: 80.6%) and from 3.0% to 6.7% (p=0.0255) for Cohort C (CT rate: 92.4%). The introduction of CT lowered NAR-STD from 1996-2000 (9.2%) to 2001-2010 (2.9%) but increasing the CT rate from 2001-2010 had no impact on the NAR. The positive predictive value for Alvarado score (98.60%) and CT (99.03%) were similar.

CONCLUSIONS

The definition of a negative appendicectomy determines the NAR. CT reduces the NAR regardless of definition but routine CT is unnecessary for male patients with positive Alvarado scores. Early/mild appendicitis may resolve without surgery and CT may contribute to unnecessary surgery. Alvarado scoring allows selective use of CT in suspected appendicitis.

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.

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.

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.

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.

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.

Moebius syndrome: report of case

This is a review of diagnosis, etiology and abnormalities of Moebius syndrome. The Moebius syndrome is rare and the cause is still unclear. It presents a case of a premature newborn baby with Moebius syndrome, showing unilateral facial nerve palsy, asymmetry of facial expression, inability to tightly close the right eyelids, asymmetry of the angles of the mouth with frequent drooling, poor sucking ability, dysphagia, extremity abnormalities and other cranial nerve involvement (VIII, IX, X, XI). He also had hypoplasia of the pons, a heart defect, and bilateral cryptorchism. The baby died of apnea on the 41st day after birth.

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)

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.

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)

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.

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)

[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.

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)

Clinical observations on Blauth's total endoprosthesis of the knee joint

This article reports on 207 implantations of the Blauth hinged endoprosthesis of the knee joint. Follow-up was possible in 188 (91%) of the implanted cases. The results could be clearly evaluated with a comparison between the time before and after operation, by means of a four-point system. They were very good in 85% and good in 11% of the cases, with an average follow-up period of 33 months, maximum longer than 8 years. The rheumatoid patients showed somewhat better results than those with osteoarthrosis. One of the main features of the success of the implanation in our follow-up patients was the relief from pain. To date, neither aseptic loosening nor fracture of prosthesis has been observed. The follow-up results, based on clinical aspects and constructional characteristics of the model during an observation period as long as 8 years, were encouraging. There was convincing evidence that because of the efficiency and predominance of the Blauth endoprosthesis no modification of the model was needed for further implantations. Technical complications could be prevented by careful manipulation. However, infection was still the most serious complication, affecting predominantly rheumatoid arthritis patients [6]. It always caused troublesome problems in management and jeopardized the success of the arthroplasty. The patella syndrome was another postoperative problem, though it was less serious than infection.

[Suggestion for technical facilitation of Blauth's knee endoprosthesis implantation]

Unsatisfactory seats of the prosthesis in femur and tibia within our clinical and roentgenological materials have been analysed. Upon this basis, the authors suggest some technical improvements with implantation of Blauth's prosthesis of knee joint as follows: 1) Preoperative exact plan of bone resections according to a.p. and lateral X-ray films of knee joint with the aid of cut-out X-ray films of the prosthesis and/or of our test-apparatus of femoral shaft. 2) Ascertain the horizontal line of tibia with the help of a vertical line of tibial shaft drawn preoperatively. 3) It should be emphasized, that finger groping during operation is indispensable.

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.

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.

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.