The effect of different porcelain conditioning techniques on shear bond strength of stainless steel brackets

A 51-year-old man was admitted because of bilateral fatigable blepharoptosis with diurnal fluctuation. He had a tendency to take much instant foods before onset. On admission, he showed symmetrical bilateral ptosis, supranuclear upward gaze palsy and vertical diplopia. Ptosis mildly improved on lateral or upward gaze. Bell's phenomenon and pupillary response were intact. Intravenous edrophonium infusion test and serum antiacetylcholine receptor antibody were negative. Cranial MRI and CT demonstrated the lesion in the periaqueductal gray (PAG) region from superior colliculus to upper pontine level, which was remarkably enhanced by Gd-DTPA infusion. He was diagnosed as midbrain ptosis, probably due to atypical Wernicke's encephalopathy. It was conceivable that the PAG lesion might be contributory to fatigable blepharoptosis (pseudomyasthenia) and supranuclear upward gaze palsy in the present case, because the PAG controls levator palpebrae neurons of central caudal nucleus in oculomotor nucleus complex and receives afferents from the limbic system., reticular formation and posterior commissure.     

The effect of microetching on the bond strength of metal brackets when bonded to previously bonded teeth: an in vitro study

The purpose of this in vitro study was to answer the following questions for three different metal brackets: (1) when rebonding a previously bonded tooth, how do shear bond strengths compare for new brackets, new microetched brackets, and debonded microetcher cleaned brackets? and (2) how do the different bracket types compare with respect to the time required to remove composite resin from their bonding pads with a microetcher? Ninety human premolars and canines previously debonded of metal brackets were randomly assigned to 9 groups of 10 teeth each. New, new etched, and debonded etched cleaned brackets of each type were bonded with composite resin onto teeth, and the bonds tested to failure for shear bond strength. An analysis of variance and Duncan's multiple range test were used to compare bracket/enamel bond strength. Within each bracket type no significant differences were found between mean bond strengths for new, new etched, and debonded etched conditions, a finding that supports the use of microetching to clean accidentally debonded brackets. Mean times for removal of resin from bonding pads with a microetcher varied from 9.3 seconds to 11.9 seconds, with bracket (M) requiring significantly less time for removal of resin.     

Shear bond strength of orthodontic brackets cemented with a zinc oxide-polyvinyl cement

The purpose of this study was to compare the shear bond strengths and enamel surface structure after debonding a conventional metal bracket and a polycrystalline ceramic bracket bonded with a bipolar zinc oxide-polyvinyl cement (F-21) or a light-cured resin cement (Transbond). Forty extracted human premolars were used. The buccal enamel surfaces were used, and the teeth randomly divided into four groups of 10 teeth each: group 1: conventional metal bracket (Unitek) bonded with Transbond; group 2: metal bracket bonded with F-21; group 3: ceramic bracket (Transcend 2000) bonded with Transbond; and group 4: ceramic bracket bonded with F-21. The brackets were bonded to the etched enamel surfaces according to manufacturer's instructions. All specimens were stored in distilled water for 24 hours and then thermocycled for 300 cycles between 5 degrees C and 55 degrees C. The specimens were mounted in dental stone and placed in the Instron at a crosshead speed of 0.5 mm/min with a knife-edged blade. Immediately after debonding, the enamel surface and bracket-enamel interface were evaluated visually and with a stereomicroscope. Representative samples were then examined with the scanning electron microscope. The analysis of variance and Student-Newman-Keuls tests were performed. The results in megapascals were Group 1: 19,6 (+/- 9,6); group 2: 14,3 (+/- 4,6); group 3: 28,8 (+/- 12,6); and group 4: 18,5 (+/- 7,5). Group 3 was statistically significantly different (P < 0.008) from all other groups. Groups 1, 2, and 4 were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of the stresses developed in tension, shear peel, and torsion strength testing of direct bonded orthodontic brackets

Strength testing of direct bonded orthodontic bracket systems is commonly performed with tension, shear peel, or torsion loads. In general, the results of these tests are reported as an average stress that is computed by dividing the experimentally measured force at failure by the area of the bracket base. The average value, obtained in this manner, implies an evenly distributed stress field. In this project, finite element model (FEM) calculations were used to determine the more realistic stress distributions generated within the cement. The results indicate that the three loading modes produce very different non-uniform stress field patterns. Furthermore, the calculated stress peaks and the stress component proportions depend on the loading method. It was therefore concluded that the manner of loading affects the strength measurements and that the average stress does not adequately characterize bond strength.     

Effect of polymerization mode of a dual-cured resin cement on time-dependent shear bond strength to porcelain

PURPOSE: To evaluate the shear bond strengths to porcelain and setting times of a dual-cured resin cement with light/chemical curing (dual) or chemical only curing versus time. MATERIALS AND METHODS: Variolink resin cement was bonded to specimens of etched, silanated porcelain. Groups of specimens were cured by dual cured or by chemical curing only. Shear bond strengths were recorded at 2, 3, 5, 60 minutes and 24 hours for dual cured and at 10, 20, 40, 50, 60 minutes and 24 hours for chemical-cured only after mixing. Kinetic-temperature profiles of dual and chemical curing modes of cement were calculated. RESULTS: Maximum bond strengths and time to attainment were 17.5 +/- 2.7 MPa at 60 minutes for chemical-cured and 26.1 +/- 2.3 MPa at 5 minutes for dual-cured. The peak in the kinetic-temperature setting profiles were 14.1 +/- 0.9 minutes for chemical curing and 52.2 +/- 5.2 seconds for dual curing. Dual curing provided significantly higher shear bond strengths versus chemical curing at both the 60-minute and 24-hour time periods.     

Effects of various methods of chlorhexidine application on shear bond strength

We report a simple new method for measuring the conduction velocity (CV) of A delta fibers in normal subjects. A large positive component of somatosensory evoked potential (SEP) whose peak latency was approximately 250 ms was clearly recorded only when strong electrical stimulation causing a definite painful feeling was applied to the skin. The CV of the peripheral nerve was calculated by measuring the latency difference of this component between the distal-stimulated SEP and proximal-stimulated SEP and the distance between two stimulus sites. The CV was approximately 11.4 m/s, (range 8.8-15.9 m/s), in the range of A delta fibers. The sleep effect on pain-related SEP was also observed in 3 subjects. The amplitude of pain-related SEP decreased with the progress of sleep stage. This simple and novel method is available in most clinics and should be very useful in investigating the physiologic functions of peripheral nerves in patients as well as normal subjects.     

In vitro peel/shear bond strength evaluation of orthodontic bracket base design

OBJECTIVES: The adhesive capacity of 17 different bracket types was evaluated in an in vitro peel/shear test. METHODS: Silane-treated metal bars were used as substrates with all bonding being performed using the orthodontic adhesive Concise. The effect of aluminium oxide air abrasion on the bonding performance of recycled metal bracket bases was evaluated. Morphological examination of the bracket bases was carried out under scanning electron microscopy. Statistics analysis included one-way ANOVA with Tukey's Studentized Range Test, two-way ANOVA and Weibull analysis. RESULTS: Mean peel/shear bond strength values range from 13.9 MPa for Allure Accu Arch, a ceramic bracket type, to 1.6 MPa for the plastic bracket CeramaFlex Advant Edge. Allure Accu Arch performed the best of all the ceramic brackets. However, bracket wing fracture was observed. The metal brackets Mini masters and Omni Arch showed no significant difference in bond strength compared with the ceramic bracket Allure Accu Arch (P < 0.01). CONCLUSION: The type of the bracket base determines its adhesive capacity. Sandblasting the base of recycled metal brackets had no uniform effect.     

Parametric stress analysis of bonded "combination-materials" type of orthodontic brackets

The finite element analysis method and a two-dimensional idealization were used to conduct a detailed parametric study of the stresses in and displacement of models of bonded edgewise "combination-materials" type of orthodontic brackets when subjected to loading and constraint conditions that are deemed to be the same as those that exist in vivo. A "combination-materials" type bracket is herein defined as one in which different materials are used in fabricating the main body and the archwire slot. The present study was conducted in three parts. In Part 1, 16 model cases were analyzed, involving 4 different combinations of materials (for the main body of the bracket and its archwire slot) and 4 different overall bracket configurations (comprising main body, base and slot). The focus of Part 2 was the model bracket configuration that was, on the basis of Part 1 results, deemed to show the "optimum performance". In this part, the parameter investigated was the value of the modulus of elasticity of the adhesive, Eadh. In Part 3, the concept of an efficiency index of the bonded bracket-archwire system, eta, was introduced and explained. The dependence of eta on stated characteristics of a rectangular archwire, for the "optimum performance" model, was explored. Part 1 results led to the conclusion that the "optimum performance" model has equally angulated buccal and lingual edges and the main body and archwire slot are fabricated from glass fiber-reinforced polycarbonate and stainless steel, respectively. Part 2 results showed that, for the aforementioned "optimum performance" model, the longitudinal displacement of the archwire slot is fairly insensitive to Eadh. Part 3 results showed that eta is intimately related to each of the wire characteristics studied (namely cross-sectional dimensions, "interbracket distance" and modulus of rigidity of the material).     

Assessment of shoulder dimensions and angles of porcelain bonded to metal crown preparations

This research examined hand preference for a bimanual task in 45 tufted capuchin (Cebus apella) and 55 rhesus macaque (Macaca mulatta) monkeys. Investigators presented subjects with plastic tubes lined with food and noted which hand the animals used to hold the tubes and which hand the animals used to remove the food. Several significant findings emerged from this investigation. First, rhesus macaques, but not tufted capuchins, exhibited a population-level bias toward use of the right hand (although the difference in direction of hand preference between species was not significant). Second, capuchins exhibited greater hand preference strength than did macaques. Third, among capuchins, but not among macaques, hand preference strength was greater for adults than for immatures. Finally, both species used their index digit to remove food most frequently when compared with other digits. Findings of hand preference direction and strength in this study were compared with other findings noted for chimpanzees which performed a bimanual tube task in a previous study. The authors conclude that using the same procedure to compare hand preference across species represents a powerful research tool that can lead to a more complete understanding of the evolution and ontogenesis of primate handedness.     

不同酸蚀处理方法对氟斑牙托槽脱落率的影响

目的:观察不同酸蚀方法对氟斑牙粘结托槽的脱落率的影响,筛选一种降低氟斑牙托槽脱落率的临床可行的酸蚀方法.方法:选择14例中度氟斑牙患者的226颗牙齿为研究对象,按左右分为28个区,随机分为4组(每组7个区):分别为酸蚀1 min组(n=56)、酸蚀2 min组(n=57)、酸蚀3 min组(n=57)和酸蚀2次组(n=56),记录第4、8和12周托槽脱落率和托槽脱落后牙面上残留的粘接剂残留指数(ARI).结果:酸蚀2次组和酸蚀2 min组的托槽脱落率明显低于酸蚀1 min组和3 min组(P<0.05);ARI高于酸蚀1 min组和3 min组(P<0.05).酸蚀2次组的托槽脱落率低于酸蚀2 min组,但差异无统计学意义(P>0.05);ARI高于酸蚀2 min组,但差异亦无统计学意义(P>0.05).各组前磨牙脱落率均明显高于前牙(P<0.05),酸蚀2次组的前磨牙脱落率低于其他各组(P<0.05).结论:酸蚀2 min能明显降低氟斑牙托槽脱落率,2次酸蚀比1次酸蚀托槽脱落率降低,尤其是前磨牙托槽脱落率明显降低.     

Effects of different surface treatment methods on the bond strength of composite resin to porcelain

In this study failures of composite resin/ porcelain interfaces under shear loading were examined. Porcelain firing were made onto metal cylinders and porcelain surfaces were roughened with burrs or treated with hydrofloric acid gel and/ or sandblasted with a Microetcher. Two silane coupling agents were used in five groups, each of which had 22 samples. All of the treated samples were restored with a hybrid-type composite resin. Then each group was divided into two subgroups according to storage times of 24 h and 30 days. After thermocyling the samples which were stored for 30 days, all of the groups were subjected to shear force at the composite resin/porcelain interface until fracture occurred. The results showed that there were differences both in the 24-h and 30-day storage period bond strengths between the various surface treatment methods. The samples treated with all three of the Microetcher, hydrofloric acid and silane exhibited the highest shear bond values after 24 h storage, followed by the microetched/silane and the hydrofluoric acid/silane groups (F: 570.31, P: 0.00). After 30 days, the highest mean shear bond strength values were again with samples treated by all three processes. The storage period and thermocycling decreased the bond strength of samples, however, there was a significant difference among groups (F: 1388-55, P: 0.00). Silane pre-treatment of porcelain was important as the mean bond strength of sandblasted/etched specimens were significantly lower than the other groups which were treated mechanically, in 24 h. Sandblasting seems to have little effect on the bonding. The comparison of 24-h and 30-day samples have also significant difference (F: 91.4376, P: 0.00).     

Preparation of bonded porcelain inlays and onlays using a milling-coping system

The Celay-system offers an interesting alternative to existing systems for esthetic posterior restorations with ceramics. The basic idea of the concept is to prepare, either directly on the patient or indirectly on a plaster model, a pro-inlay using a light-curable precision material. The modelling also covers the occlusal surface. This pro-inlay is then used with the help of a milling center to machine a precise replica out of a ceramic block. The copying process is carried out via three-dimensional mechanical scanning and milling using eight axes of freedom. In this way additional corrections on the ceramic within the mouth can almost completely be avoided. The system is designed to be used as a direct chairside method by the dentist or as an indirect method by the dental technician. It is a promising but unproved restoration, more research and long-term clinical evaluation is recommended.     

In vitro shear strength of bonded amalgam cores with and without pins

After ileo-pouch-anal anastomosis (IPAA) there is an increased risk of incontinence due to intraoperative damage of the anal sphincter. We present a new concept to identify a potential incontinence prior to the closure of ileostomy by clinical and anal manometrical examinations. In 11 of 121 (9.1%) patients we diagnosed a potential incontinence. By biofeedback training we could achieve in this way a sufficient continence after the closure of ileostomy. After an average of 5.0 +/- 4.3 months of training rest pressures improved from 19.3 +/- 2.1 mmHg to 33.0 +/- 3.5 mmHg and squeeze pressures from 60.5 +/- 27.7 mmHg to 93.5 +/- 17.3 mmHg. Prior to IPAA patients with potential incontinence show significantly reduced rest pressures of 51.0 +/- 18.4 mmHg.     

The effect of air abrasion on shear bond strength to dentin with dental adhesives

This study compared the effects of different dentin surface treatments on the shear bond strengths of three adhesive systems. The adhesive systems included a resin-modified glass ionomer, Fuji II LC, and two dentin bonding systems, One Step and Scotchbond Multi-Purpose Plus. The surface treatments compared for each adhesive system were as follows: 1) the controls, which were conditioned, 2) air abrasion at 120 psi without conditioning, 3) air abrasion at 160 psi without conditioning, 4) air abrasion at 120 psi with conditioning, and 5) air abrasion at 160 psi with conditioning. The KCP 1000 Whisperjet was used for all air-abrasive specimens. Controls for each adhesive material (Fuji II LC, One Step, Scotchbond Multi-Purpose Plus) were bonded using manufacturers' recommendations. Results showed that air abrasion significantly lowered bond strength of the resin-modified glass ionomer, conditioned or nonconditioned (P < 0.01). Air abrasion alone significantly lowered bond strengths of the dentin bonding agent systems (P < 0.01). However, air abrasion plus conditioning of the dentin surface resulted in bond strengths that were similar to the conditioned-only specimens (P < 0.01).     

Effects of different types of light guides on shear bond strength

Several patients with end-stage renal disease went to Bombay for renal transplantation from nonrelated living donors and then returned to Turkey for posttransplantation follow-up. The aims of this study are to evaluate the long-term results of renal transplantation from nonrelated living donors in Turkish patients with end-stage renal disease and to discuss the ethical and social aspects of nonrelated kidney donation. One hundred and twenty-seven patients (89 males, 38 females; mean age 38.1, range 17-63 years) were investigated retrospectively. None of the patients went to Bombay on our advice. All transplantations were performed between 1991 and 1995. The mean follow-up period after transplantation was 34.2 (range 1-68) months. Graft survival rates were 85, 83, and 57% after 3 months and 1 and 5 years, respectively. Patient survival rates were 94, 93, and 92% after 3 months and 1 and 5 years, respectively. Seven patients died within the first 3 months after the transplantation. Surgical problems, infections, acute rejection, ciclosporin nephrotoxicity, and hepatic problems were common complications. We conclude that medical and surgical complications occur frequently in paid kidney transplantation, but most of these complications can be prevented by adequate preoperative management, and precautionary measures should be taken to prevent commercialization of renal transplantation before the spread of emotionally related living kidney donation.     

Resin to metal bond strengths using two commercial systems

This study in Senegal compared the feeding preferences of Anopheles gambiae and A. arabiensis while controlling for equal accessibility to hosts located outdoors under bed net traps. All fed A. gambiae complex females were identified with the aid of the polymerase chain reaction and their blood meal sources were identified by enzyme-linked immunosorbent assay. A total of 605 anophelines, including 281 A. gambiae and 301 A. arabiensis, were captured, 32.2% in the human-baited traps and 67.8% in bovine-baited traps. 30.3% of A. gambiae fed in the former and 69.7% fed in the latter; the corresponding figures for A. arabiensis were 29.6% and 70.4%. Thus, when the hosts were located outdoors and made equally available, the feeding preferences of A. gambiae and A. arabiensis were similar (P = 0.81). These results suggest that biases existed in previous studies, most of which suggested that A. arabiensis was more zoophilic than A. gambiae. Alternatively, the feeding behaviour of these 2 species may differ in various parts of Africa.     

Interfacial bond strengths of amalgam bonded to amalgam and resin composite bonded to amalgam

A preparative method for the preparation of large peptides is described. An advantageous theoretical weight of peptide/weight of starting resin ratio (tPw/Rw) of about 0.3 was successfully experimented. The esterification of the first amino acid was realized with a racemization of less than 1%. The study of the coupling conditions led to the use of a diluted acylating mixture that allowed a 56% consumption of the amino acid derivatives (percentage use of amino acids) introduced in the synthesis. The cost analysis of the synthesis showed that the recovery of the amino acid derivatives was not worthwhile.     

Effects of tin plating on base metal alloy-ceramic bond strength

Recombinant Der p 2, expressed in the baker's yeast Saccharomyces cerevisiae, was used as a tool to determine IgE- and monoclonal antibody (mAb)-binding sites on this allergen. For this purpose, mutant molecules were produced by application of site-directed mutagenesis. The amino-acid residues spanning cys21-cys27 and cys73-cys78 were deleted, thus preventing loop formation through disulfide bonds. Charged residues in three predicted antigenic sites (residues 45-48, 67 + 69, and 88-90) were replaced by alanine residues, IgE- and mAb reactivity to these mutants was compared to that to "wild type" Der p 2. Residues spanning cys73-cys78 were involved in the antigenic binding site for mAb alpha DpX. Mutations in the areas adjacent to this loop (i.e., 67 + 69 and 88-90) had similar effects on this mAb (10- to 20-fold decreases in reactivity were observed), supporting the suggestion that these areas are involved in this antigenic structure. The area of residues 45-48 was shown to be involved in an epitope for mAb 2B12. The reactivity of mAb 7A1 was influenced by substitutions of residues 45-48 as well as 88-90. Deletion of the residues spanning cys21-cys27 resulted in decreased reactivity to three mAbs (10E11, alpha DpX, and 7A1). From these observations, it may be concluded that binding of different mAbs is influenced by the same mutations and that the binding of single mAbs is influenced by two or more mutations scattered over the allergen molecule. These findings can point in two directions: minor amino-acid changes result in disruption of the overall conformation of the allergen, or distant sites are close together in the three-dimensional structure of the allergen. Decreased IgE reactivity was observed with all mutant molecules, varying between patients. The observed effects ranged from 5- to 1000-fold. Deletion of the amino-acid residues spanning cys21-cys27 and cys73-cys78 had the strongest effect on IgE reactivity, where decreases up to 1000-fold were observed. Such mutants might be useful tools to improve the safety of allergen-specific immunotherapy.     

Effect of etchant, etching period, and silane priming on bond strength to porcelain of composite resin

The purpose of this study was to evaluate the effect of etching and silane priming on bond strength to a feldspathic porcelain (VMK 68) of a composite resin (Clearfil APX). Two hydrofluoric acid etchants (2.5% and 5%) and seven different etching times (0, 30, 60, 90, 120, 150, and 180 seconds) were used to etch the porcelain specimens respectively. A self-curing bonding agent containing a silane coupler (Clearfil Porcelain Bond) was used on both etched and unetched porcelain surfaces. Etched relief patterns were observed by means of a scanning electron microscope, and the bond strengths between the photocured composite resin and the porcelain were determined. Scanning electron micrographs revealed complicated etching patterns with increased etching time periods. Shear testing results showed that the bond strength to the unetched porcelain of the composite resin was very low, and that etching periods for more than 30 seconds effectively enhanced the bond strength. Of the two etching agents applied to the unsilanated porcelain, the buffered 2.5% etchant produced higher bond strengths than the 5% etchant for all etching time periods except for 180 seconds. Silane priming was effective and critical for improving bond strength to the porcelain. Application of the silane bonding agent to the porcelain after hydrofluoric acid etching appeared to be suitable for achieving consistent bonding between the composite resin and the porcelain.