bluuebunny/crossref_metadata_2025 huggingface dataset:
THE OUTPUT OF THE SWEDISH EDUCATION SECTOR
Authors: Ahlroth Sofia , Björklund Anders , Forslund Anders
Published: March 2005

The output of the Swedish education sector is defined as the addition to lifetime incomes generated by the schooling system. Using cross‐sectional information on wages, employment rates, working hours, school‐participation and leisure time, all by years of schooling, we compute new output‐based measures of the education sector. Measures that include and exclude leisure, and that are counted before and after taxes are computed for the years 1967, 1973, 1980 and 1990. Our most important conclusion is that the output‐based measure differs so markedly from conventional input‐based ones that a replacement of the latter with the former would change the picture of the overall performance of the Swedish economy over the period.
FAMILY SAFETY NETS AND ECONOMIC TRANSITION: A STUDY OF WORKER HOUSEHOLDS IN POLAND
Authors: Cox Donald , Jimenez Emmanuel , Okrasa Wlodek
Published: March 2005

Can Eastern European families most severely impoverished during the transition to capitalism rely on private family safety nets? This question is likely critical for the transition's success, but little is known about family networks in Eastern Europe. We analyze newly available Polish household surveys, conducted both before and after Poland's economic transition, which measure private inter‐household transfers. Such transfers are large and widespread in Poland, and in many ways appear to function like means‐tested public transfers. They flow from high to low‐income households and are targeted to young couples, families with many children and those experiencing illness. Private transfer patterns also suggest that they are responsive to liquidity constraints. Our results from 1987 data indicate that private transfers could fill a non‐trivial portion of the income gap left by unemployment. However, we also find evidence from 1992 data suggesting that family networks weakened somewhat after the transition.
POPULATION AGING AND CONSUMPTION INEQUALITY IN JAPAN
Authors: Ohtake Fumio , Saito Makoto
Published: March 2005

This paper analyses how consumption inequality within a fixed cohort grows with age using Japanese household microdata. Following the method developed by Deaton and Paxson (1994), we obtain the following results. First, consumption inequality starts to increase at the age of 40. Second, younger generations face a more unequal distribution from the beginning of their life‐cycle. Third, half of the rapid increase in the economy‐wide consumption inequality during the 1980s was caused by population aging, while one‐third was due to the increasing cohort effect. The paper compares the above results with those of Deaton and Paxson.
INEQUALITY AND MOBILITY OF WEALTH IN SWEDEN 1983/184–1992/193
Authors: Bager‐Sjögren Lars , Klevmarken N. Anders
Published: March 2005

Using longitudinal data which include real estate wealth, financial assets as well as consumer durables, changes in the distribution of wealth in Sweden are related to major changes in asset prices and in incentives to hold various assets in the 1980s and the beginning of the 1990s. Our analysis of the mobility of wealth indicates that decile mobility is higher in Sweden than in the U.S., while the analysis of who is gaining and who is loosing shows results similar to those of previous studies.
The In Vivo Wear Resistance of 12 Composite Resins
Authors: Lang Brien R. , Bloem Thomas J. , Powers John M. , Wang Rui‐Feng
Published: March 2005

Purpose The in vivo wear resistance of 12 composite resins were compared with an amalgam control using the Latin Square experimental design. Sixteen edentulous patients wearing specially designed complete dentures formed the experimental population.

Materials and Methods The Michigan Computer Graphics Measurement System was used to digitize the surface of the control and composite resin samples before and after 3‐month test periods to obtain wear data. The 12 composite resins selected for this investigation based on their published composite classification types were seven fine particle composites, three blends, and two microfilled composite resins. The Latin Square experimental design was found to be valid with the factor of material being statistically different at the 5% level of significance. Wear was computed as volume loss (mm3/mm2), and all of the composites studied had more wear than the amalgam control (P= .001).

Results After 3 months, the mean (error) of wear of the amalgam was 0.028 (0.006). Means (error) of wear for the 12 composites were ranked from most to least wear by mean wear volume loss.

Conclusions The absence of any relationship between mean wear volume loss and the volume percentage filler was confirmed by the correlation coefficient r= ‐0.158.
The Use of Light–Cured Acrylic Resin to Bond and Seal Castings Into Denture Teeth
Authors: Williams Earl O. , Seals Richard R.
Published: March 2005

In order to satisfy their personal perception of esthetics, some patients request that gold castings be incorporated into their denture teeth. The use of light‐cured acrylic resin to bond and seal gold castings into denture teeth overcomes many of the problems traditionally associated with cementing castings to denture teeth or processing tooth‐colored acrylic resin around castings.
Full‐Arch Implant Framework Casting Accuracy: Preliminary In Vitro Observation for In Vivo Testing
Authors: Carr Alan Brooks , Stewart Robert Bruce
Published: March 2005

Purpose Conventional techniques for implant metal framework fabrication produce error of a magnitude that is inconsistent with the passive‐fit requirement for osseointegrated implants. To understand the correlation between prosthesis fit and the implant‐tissue response, evaluation of the interface tissue reactions to customary levels of fit is required. The purpose of this study is to determine the accuracy of torch casting full arch frameworks using a high palladium alloy and a ringless phosphate‐bonded investment technique.

Materials and Methods Three different variables were considered relative to casting accuracy effect. The first variable, completeness of mold‐fill, compared cast specimens where the entire sprue system was filled as part of the casting and cast specimens without the sprue system filled. The second variable, phosphate‐bonded investment special liquid concentrations, compared groups of castings produced from 0%, 12%, 25%, and 50% special liquid. The third variable, investment mold shape, compared casting produced from a conventional ringless mold shape with a modified ringless mold shape where the investment in the same horizontal plane as the pattern was equal in thickness at the internal and external surfaces. Horizontal and vertical distances on the wax pattern and resulting framework were measured using a machinists microscope to determine casting error. Combined vertical and horizontal error was used for comparison between groups (one‐way analysis of variance).

Results No significant differences existed among the three groups compared (P > 0.05). The mean error comparison between the complete and incomplete mold‐fill groups showed no statistical difference, while the incomplete fill group was found to be more porous. The mean error of all groups (0.130 mm) exceeded the recommended level of fit needed to satisfy the passive fit requirement by more than 10‐fold.

Conclusions These results verify clinical observation and suggest that the use of conventional lost wax casting technique to cast one‐piece full arch implant frameworks is both imprecise and inaccurate as judged against the passive fit requirement. The consequences of screw‐fastening misfitting prostheses to osseointegrated implants is currently under investigation.
Cobalt‐Chromium and Nickel‐Chromium Alloys for Removable Prosthodontics, Part 1: Mechanical Properties
Authors: Bridgeport David A. , Brantley William A. , Herman Paul F.
Published: March 2005

Purpose This investigation compared the mechanical properties of three base metal casting alloys (Vitallium2, Neoloy N [Regular], and Regalloy T) for removable partial denture (RPD) frameworks with those for two base metal RPD alloys (Vitallium, Jelenko LG) whose mechanical properties had been previously reported.

Materials and Methods Plastic patterns with dimensions meeting ADA specification no. 14 requirements were used with appropriate casting investments to cast tensile test bars of the five alloys. Nine specimens of each alloy were loaded to failure, and the mechanical properties of modulus of elasticity, 0.1% yield strength, 0.2% yield strength, and tensile strength were obtained from five well‐behaved load‐elongation plots. Values of percentage elongation were also determined, along with Vickers hardness of the work‐hardened alloys from polished cross‐sections of fractured tensile specimens. The fracture surfaces for representative specimens of each alloy were examined with a scanning electron microscope.

Results Although the measured values of mechanical properties generally agreed with those reported by the manufacturers, differences found for Vitallium and Jelenko LG with previous investigations suggest that there may have been some changes in alloy compositions and processing by the manufacturers. The investment burnout procedure adopted for the plastic patterns and the present casting conditions may also have affected the mechanical properties of some alloys. Two alloys, Jelenko LG and Regalloy T, had mean values of percentage elongation exceeding 10%, but caution is recommended for clinicians and dental laboratories when performing clasp adjustments with all five alloys because of the substantial work hardening that can occur.

Conclusions In general, all of the alloys met the requirements in ADA specification no. 14 for base metal RPD alloys. Further research will be necessary to determine the relationships between the mechanical properties, particularly yield strength, rate of work hardening and percentage elongation, and the clinical requirements for these alloys.
Use of an Axisymmetric Finite Element Method to Compare Maxillary Bone Variables for a Loaded Implant
Authors: Clelland Nancy L. , Lee June K. , Bimbenet Oliver C. , Gilat Amos
Published: March 2005

Purpose This study determined the effect of various bone models on the stresses and strains generated under occlusal loading of a dental implant.

Materials and Methods A two‐dimensional finite‐element model was created for stress analysis. The geometric and elastic properties of a 3.8 × 10‐mm Steri‐Oss implant embedded in a segment of premaxilla were modeled. Computed tomography scanning of a dried maxilla half was used to determine representative geometry and density of this region. Material properties for bone were varied to simulate the following: all‐cancellous bone, cancellous bone with a thin (1.5‐mm) crestal isotropic cortical layer, cancellous bone with a thick (3‐mm) crestal isotropic cortical layer, and cancellous bone with a thick (3‐mm) layer of transversely isotropic (orthotropic) cortical bone.

Results Low stresses and high strains surrounded the fixture apex for the all‐cancellous bone model. When a layer of cortical bone was added, higher crestal stresses and lower apical strains were observed. The thicker layer of isotropic cortical bone produced stresses at least 50% less than the thinner layer. The assumption of transverse isotropy (orthotropy) increased stresses and strains by approximately 25% compared with isotropic bone.

Conclusions Crestal cortical layer thickness and bone isotropy have a substantial impact on resultant stresses and strains. Clinical assessment of these parameters is recommended.
A Measurement of Torque Values Obtained With Hand‐Held Drivers in a Simulated Clinical Setting
Authors: Dellinges Mark A. , Tebrock Otto C.
Published: March 2005

Purpose This study measures the amount of torque that can be applied to the heads of implant screws via hand‐held drivers and wrenches in a simulated clinical setting.

Materials and Methods Sixty second‐year dental students applied their maximum controlled torque to the head of a hex instrument attached to a Tonichi torque gauge mounted in a mannequin. The torque values obtained were recorded, and a mean torque value was calculated.

Results The mean torque value obtained in this study was 11.55 N · cm.

Conclusions Small‐diameter, 10 N · cm gold screws can be adequately tightened with manufacturer‐supplied instrumentation. Larger screws requiring more than 10 N · cm of torque cannot be tightened manually using currently available hand‐held screwdrivers and hand wrenches.
Comparison of “Look‐Alike” Implant Prosthetic Retaining Screws
Authors: Jaarda Merle J. , Razzoog Michael E. , Gratton David G.
Published: March 2005

Purpose The maximum preload torque of implant prosthetic retaining screws from four manufacturers and of two alloy types was measured to determine one index of interchangeability of intersystem components.

Materials and Methods Implant prosthetic retaining screws from four manufacturers (3i Implant Innovations Inc, West Palm Beach, FL; Impla‐Med Inc, Sunrise, FL; Nobelpharma USA Inc, Chicago, IL; and Implant Support Systems Inc, Irvine, CA) and of two metal types (gold and titanium) were investigated using an in vitro simulation model. Five screws of each type were tightened down against a gold cylinder using a Tohnichi BTG‐6 torque gauge (Tohnichi American Corporation, Northbrook, IL) until fracture occurred.

Results The 3i Implant Innovations gold and the Nobelpharma gold were not significantly different. The 3i Implant Innovations titanium and the Impla‐Med gold were able to withstand less preload torque than the 3i Implant Innovations gold and the Nobelpharma gold. The Implant Support Systems titanium was able to withstand significantly more preload torque than all of the other screws.

Conclusions Interchanging implant prosthetic retaining screws could introduce new and unknown variables that may affect the long‐term survival of implant fixtures and/or the implant prostheses.
A Comparison of Infrared‐ and Torch‐Soldering of Au‐Pd and Co‐Cr Metal‐Ceramic Alloys Using a High‐Fusing Solder
Authors: Dominici John T. , Sobczak Kenneth P. , Mitchell Richard J.
Published: March 2005

Purpose The purpose of this study was to compare the bond strengths and fracture modes of soldered joints formed by infrared and gas‐oxygen torch heating of a high‐fusing, gold‐based solder in two metal‐ceramic alloys.

Materials and Methods Pairs of half‐dumbbell–shaped specimens of either an Au‐Pd or a Co‐Cr alloy were positioned with a 0.25‐mm gap and were joined using a high‐fusing, gold‐based solder by either gas‐oxygen torch heating or infrared heating. The resulting specimens were subjected to a heat treatment that simulated ceramic firing. Each specimen was fractured in tension at a loading rate of 0.5 cm/min, and its bond strength was measured. The halves of the specimen were rejoined using the other heating method and were heat treated, and the specimen's bond strength was again measured. Fractured cross‐sections were examined at a magnification of 40× to determine the following: the fracture mode (adhesive, cohesive, or mixed); the percentage of adhesive fracture; the presence or absence of voids, porosities, or flux inclusions; and the percentage of the cross‐section that was discolored.

Results Three‐factor analyses of variance showed that neither the heating method, the particular specimen tested, nor the order of testing significantly affected the bond strength (P < .05). For each alloy, significantly fewer infrared‐heated joints than torch‐heated joints contained voids, porosities, or flux inclusions visible at 40× (χ2 test, P < .05). All fractures were either entirely cohesive in the solder or mixed cohesive and adhesive. When infrared heating was used, entirely cohesive fractures occurred more frequently in the Au‐Pd alloy specimens than in the Co‐Cr alloy specimens (χ2 test, P < .05). The coefficients of variation of the bond strengths for the infrared‐heated joints were smaller than those for the torch‐heated joints.

Conclusions Although the two heating methods produced solder joints that had strengths that were not significantly different, infrared‐heated joints showed less scatter in bond strengths. It was suggested that, in the hands of most technicians, fewer infrared‐heated joints would contain defects visible at a magnification of 40×. The presence of such defects may increase the probability of in vivo failure caused by cyclic stresses.
Marginal Discrepancy of All‐Ceramic Crowns Cemented on Implant Abutments
Authors: Sutherland J. Kenneth , Loney Robert W. , Syed Sara
Published: March 2005

Purpose The purpose of this investigation was to determine the mean marginal discrepancy of all‐ceramic crowns cemented on implant abutments.

Materials and Methods Five Brånemark CeraOne abutments were connected to implant fixtures embedded in acrylic resin blocks. The marginal discrepancy was measured using a video camera connected to a digitizing board at four locations on each abutment for five samples in each of the following groups: all‐ceramic caps (caps), all‐ceramic crowns (crowns), and all‐ceramic crowns cemented with zinc phosphate cement (cemented crowns).

Results The mean marginal discrepancies were as follows: caps, 99.0 μm (SD, 16); crowns, 117.8 μm (SD, 20); and cemented crowns, 168.8 μm (SD, 23). Statistically significant differences were found between all three groups at the 99% level of confidence. In addition there were two significant differences between abutments.

Conclusions Subgingival marginal discrepancies of the magnitude measured in this study have been shown to cause periodontal problems. It is probable that the marginal discrepancy of CeraOne restorations, as tested, can be improved. Efforts should be made to enhance the marginal accuracy of these restorations.
Compressive Characteristics of an Internally Threaded Post System
Authors: Laurell Kim Allen , O'Neilly Paul , Johnston William M.
Published: March 2005

Purpose

The effects of oblique compressive forces were evaluated for extracted teeth restored with posts of solid and internally threaded designs.

Materials and Methods

A group of 25 roots was restored with crowns supported by Para‐post dowels and pin‐retained composite resin cores, and a second group was restored with gold copings cast to internally threaded stainless steel‐post prototypes. Samples were then embedded in epoxy resin and loaded at 45° until failure. Failure force and type were statistically analyzed to determine statistical difference (P < .05) between groups.

Results

No statistical difference was shown between groups for either fracture force or type.

Conclusions

The internally threaded post system resisted oblique loading forces similarly to a solid post system.
Comparison of the In Vitro Fatigue Resistance of an Acrylic Resin Removable Partial Denture Reinforced With Continuous Glass Fibers or Metal Wires
Authors: Vallittu Pekka K.
Published: March 2005

Purpose

The fatigue resistance of heat‐polymerized acrylic resin test specimens reinforced with continuous glass fibers or metal wire was investigated.

Materials and Methods

Test specimens in the shape of maxillary removable partial dentures were reinforced with one of the following: (1) circular steel wire (cross‐sectional diameter, 1.0 mm); (2) semicircular steel wire (cross‐sectional diameter, 1.0 × 2.0 mm); or (3) continuous unidirectional E‐glass fibers. Ten specimens were fabricated for each test group. The specimens were tested by a constant force flexural fatigue test at a force of 180 N while immersed in 37°C water. The number of loading cycles required to generate a fatigue fracture and the position of the fracture were measured.

Results

Results showed that the test specimens, which were either unreinforced or reinforced with metal wires, fractured after 13,197 to 39,237 loading cycles. For the glass fiber‐reinforced test specimens, the fracture did not coincide with the region of the strengthener but with the opposite side of the test specimen after 1,239,298 loading cycles. The position of the fracture showed a statistically significant variation between the test groups (P < .001).

Conclusions

This study suggests that the fatigue resistance of acrylic resin removable partial dentures reinforced with glass fibers are superior to those removable partial dentures reinforced with conventional metal wire.
A Technique for Shielding Electron Beams Used in Radiotherapeutic Management of Head and Neck Cancer
Authors: Coleman Allyn J.
Published: March 2005

One of the major complications of radiation therapy in the management of maxillofacial tumors is the postradiation damage to the healthy tissues adjacent to the tumors. The success of radiation therapy is often limited by the treatment sequelae. The use of shielding prostheses reduces the number of potential treatment sequelae caused by the administration of therapeutic radiation for head and neck tumors. A technique for shielding uninvolved tissues from external electron beams used in therapeutic radiation treatment of head and neck cancer is described. The materials required are readily available and the shielding prosthesis can be easily fabricated by any dentist with a thorough understanding of radiation therapy, dosimetry, and the goals of treatment with radiation therapy.
Metallurgical Structure and Microhardness of Four New Palladium‐Based Alloys
Authors: Vermilyea Stanley G. , Cai Zhuo , Brantley William A. , Mitchell John C.
Published: March 2005

Purpose This investigation compared the Vickers hardness and microstructures of four recently marketed, palladium‐based alloys for metal‐ceramic restorations.

Materials and Methods Wax patterns simulating copings for maxillary central incisors were invested in a fine‐grained, carbon‐free, phosphate‐bonded investment. Following burnout, the palladium alloys were fused with a gas‐oxygen torch, centrifugally cast, and bench‐cooled. Representative castings were embedded in transparent metallographic resin and sectioned to yield two mirror‐image specimens. The specimens were evaluated in either the as‐cast condition or following heat treatment simulating the firing cycles for Vita VMK porcelain. Vickers hardness measurements (n = 50) were made using a 1‐kg load, and photomicrographs of polished and etched specimens were obtained with a scanning electron microscope.

Results The measured values of microhardness for the as‐cast alloys were in excellent agreement with values reported by the manufacturer. The hardness in the as‐cast condition was significantly greater for the Pd‐Cu‐Ga‐In alloy, compared with the other three alloys, which did not contain copper. For the three high‐palladium (≥ 75 wt%) alloys, there were small (4%‐8%) decreases in hardness following heat treatment, whereas a larger decrease (13%) in hardness occurred for the Pd‐Ag‐In‐Sn alloy after heat treatment. The porcelain firing cycles caused microstructural homogenization for all four alloys, and the relatively thick near‐surface oxidation region in the Pd‐Cu‐Ga‐In and Pd‐Ag‐In‐Sn alloys was not observed in the two heat‐treated Pd‐Ga‐Ag‐In‐Au alloys.

Conclusions The multiphasic microstructures of these alloys may have some significance for the in vitro and clinical corrosion behavior and the metal‐ceramic bond strength. The hardness for the three high‐palladium alloys may be controlled by submicroscopic precipitates that remain unaltered by heat treatment. The significantly greater hardness for the Pd‐Cu‐Ga‐In alloy may cause greater difficulty for finishing castings in the dental laboratory compared with the other three alloys studied. The strengthening mechanism for the Pd‐Ag‐In‐Sn alloy has significant temperature dependence, which might be exploited to achieve optimum mechanical properties.
Short‐Term Results of IPS‐Empress Full‐Porcelain Crowns
Authors: Lehner Christian , Studer Stephan , Brodbeck Urs , Schärer Peter
Published: March 2005

Purpose A leucite‐reinforced, glass‐ceramic material was recently introduced for clinical use. In this clinical trial, IPS‐Empress material was tested in the form of full‐porcelain crowns.

Materials and Methods Thirty‐four patients were restored with 78 full‐porcelain crowns. After etching the crowns with hydrofluoric acid, they were silanized and luted using dentin bonding agents and resin composite cement, which was primarily a dual‐cured type. The 41 anterior and 37 posterior crowns were evaluated clinically with a mirror and probe, radiographically, and using clinical photographs, according to the modified United States Public Health Service criteria. Restorations having neither charlie nor delta criteria were defined as successful, and their survival rate was calculated according to Kaplan‐Meier analysis.

Results The mean observation period for the 78 restorations was 19.7 ± 8.5 months. Seventy‐four crowns were defined as successful. Four restorations failed because of fractures. Three of the four failures occurred in the first 2 months after cementation. The survival rate was estimated to be 95% successful after 2 years in service. Eighty percent of the crowns demonstrated an excellent esthetic result.

Conclusions The initial clinical results of this esthetic full‐porcelain crown system are encouraging. However, because of fatigue phenomena for all ceramic materials, a longer observation period is needed to provide a definitive prognosis about the long‐term clinical behavior.
Microwave Pressure Chamber Processing of a Denture Repair Polymer
Authors: Ewoldsen Nels O. , Sheridan Paul J. , Koka Sreenivas
Published: March 2005

Most denture base repairs are made using a chemically activated acrylic resin polymer for reasons of cost and expediency. Heat‐activated polymers are not typically used because they require a custom split cast gypsum mold, longer polymerization time, and higher laboratory fees. Repairs made using a chemically activated polymer compared with a heat‐activated polymer generally have reduced transverse strength, poorer color stability, increased water sorption, and weak bond strength to existing acrylic resin. A method of utilizing a microwave polymer in a commercially available microwave flask is described. This technique allows denture base repairs to be made with a heat‐activated polymer in a manner similar to that of chemically activated repairs.
Die Stone Disinfection: Incorporation of Sodium Hypochlorite
Authors: Breault Lawrence G. , Paul James R. , Hondrum Steven O. , Christensen Loren C.
Published: March 2005

Purpose Previous research has shown that dental gypsum casts may be effectively disinfected by the substitution of 10% of the gauging water with 5.25% solution of sodium hypochlorite. The purpose of this investigation was to determine the properties of gypsum produced from such a solution as opposed to tap water alone.

Materials and Methods Tests included setting time, compressive strength, rigidity, diametral tensile strength, setting expansion, hardness, and detail reproduction.

Results The addition of sodium hypochlorite to the gauging water resulted in a statistically significant increase in the compressive strength and rigidity, and a decrease in setting time (p .5). All other properties remained unchanged.

Conclusions This substitution may be an effective and convenient method of disinfecting gypsum casts in the laboratory without adversely effecting physical and mechanical properties.
Compositional and Weave Pattern Analyses of Glass Fibers in Dental Polymer Fiber Composites
Authors: Vallittu Pekka K.
Published: March 2005

Purpose This study compared weave patterns and glass compositions of five glass fiber materials found in commercial fiber‐reinforced dental composites.

Materials and Methods A scanning electron microscope (SEM) was used to investigate the woven structure of five glass fiber products, and an energy‐dispersive x‐ray spectrometer (SEM/EDS) was used to determine the elemental composition of these glass fibers in the bulk and at the surface of the fiber. Five fibers of each product were analyzed.

Results The fiber products were either unidirectional rovings or bidirectional weaves. More precisely, the woven structures were linen weave, twill weave, or twill weave ribbon. SEM/EDS analysis revealed that the composition of the glass fibers was typical for E (electrical)‐glass fibers with one exception. One product intended for use in fixed prosthodontics included unidirectional fibers with a composition consistent with a modified high‐tensile‐strength R‐glass. Boron oxide found on the surface of glass fibers would likely contribute to an increased potential for corrosion of fiber‐reinforced composite.

Conclusions The predominant fiber composition in these products is E‐glass. Because the degree of hydrolytic stability of polymer‐fiber composites over time may lead to material failure in permanent restorations, this property should be investigated further.
Survey of Educationally Qualified and Board‐Eligible Prosthodontists on the Board‐Certification Process
Authors: Nimmo Arthur , Taylor Thomas D.
Published: March 2005

Purpose A survey of prosthodontists who have not achieved diplomate status from the American Board of Prosthodontics was conducted to identify the reasons why they have or have not pursued and/or achieved board certification in prosthodontics.

Materials and Methods A survey was sent to 500 educationally qualified or board‐eligible prosthodontists in the summer of 1997. A total of 364 responses were received, for a response rate of 73%. The responses and comments were analyzed.

Results The majority of respondents listed private practice as their primary area of professional activity. Personal accomplishment was cited by 80% of the respondents as a major motivational factor. Three major impediments to taking the examination included: time away from practice (65%), time away from family (59%), and financial sacrifice (57%). More than one third of the respondents believed there was no advantage to attempting the board examination. Less than half of the respondents have attended The American College of Prosthodontists (ACP)‐sponsored Board Preparation Course, and half have used the ACP Study Guide. The respondents have perceived these to be useful in their preparation efforts. The survey presented four potential changes in the exam format that might encourage greater participation in the board‐certification process. Respondents showed the greatest support (64%) for the concept of a written examination only (ie, elimination of Parts 2, 3, and 4).

Conclusions Personal accomplishment was the most important motivational factor in starting the examination process. The greatest impediments to pursuing board certification were the time involved and financial resources expended. The greatest interest in a potential change in the examination format was the use of a written examination only.
A Technique to Stabilize Record Bases for Gothic Arch Tracings in Patients with Implant‐Retained Complete Dentures
Authors: Raigrodski Ariel J. , Sadan Avishai , Carruth Philip L.
Published: March 2005

Clinicians have long expressed concern about the accuracy of the Gothic arch tracing for recording centric relation in edentulous patients. With the use of dental implants to assist in retaining complete dentures, the problem of inaccurate recordings, made for patients without natural teeth, can be significantly reduced. This article presents a technique that uses healing abutments to stabilize the record bases so that an accurate Gothic arch tracing can be made.
Reinforcement of Denture Base Resin with Glass Fillers
Authors: Marei MScD Mona K., BDS
Published: March 2005

Purpose

This study evaluated the effect of short glass fibers on the transverse strength of a heat‐polymerized acrylic resin denture base material.

Materials and Methods

Four groups of specimens (n = 10) were fabricated according to the ISO standard for the transverse strength test. E‐glass fibers were triturated to produce short fibers of different lengths. Specimens for Group 1 (control) were made of unfilled polymethylmethacrylate (PMMA). For group 2, the PMMA powder was modified with 0.1 g of dry glass fibers. For group 3, the PMMA powder was modified with 0.1 g of silanized glass fibers. For group 4, the PMMA powder was modified with 0.2 g of silanized glass fibers. A three‐point loading test was used to determine the transverse strength of the tested specimens. The fracture surface of each specimen was evaluated using SEM.

Results

The addition of untreated glass fibers increased the transverse strength by 11% but produced some porosity in the polymeric matrix. The addition of silane‐treated glass fibers increased the transverse strength of PMMA by 28% for group 3 and by 26% for group 4, and produced a dense structure for the polymer‐fiber composite.

Conclusion

The transverse strength of PMMA can be slightly increased by the addition of short glass fibers.
Using Two Surgical Protocols to Restore the Edentulous Patient with Implant‐Supported Overdentures
Authors: Raigrodski Ariel J. , Finger Israel M.
Published: March 2005

Long‐term success rates are reported for dental implant systems using both the two‐stage and one‐stage surgical protocols. Although the one‐stage offers several advantages, prudent diagnosis is a key factor for selecting the appropriate surgical protocol. This article will review the relevant literature for both protocols and will illustrate their use in patient treatment.
Ovarian follicular development stimulated by leuprorelin acetate plus human menopausal gonadotropin in chimpanzees
Authors: Yoshimoto Nobuhiko , Shimoda Kohji , Mori Yusuke , Honda Ritsuo , Okamura Hitoshi , Ide Yukie , Nakashima Tatsuyuki , Nakagata Naomi , Torii Ryuzo , Yoshikawa Yasuhiko , Hayasaka Ikuo
Published: March 2005

Abstract:  We attempted ovarian stimulation using gonadotropins in 14 chimpanzees. Subjects were given a single administration of leuprorelin acetate, followed by repeated administration of human menopausal gonadotropin (hMG) for 16–21 days. During the dosing period, the ovarian follicle diameter and count were measured by transvaginal ultrasonography. The hormone administration induced the development of multiple follicles, and multiple oocytes were subsequently retrieved. However, the follicle count was decreased, suggesting atresia, in some subjects. Statistically, the final follicle diameter was dependent on the dosing duration and the hMG dose in the late stage, while the maximum follicle count during hMG administration was dependent on age and the hMG dose in the early stage. Five subjects showed mild ovarian hyperstimulation syndrome (OHSS)‐like symptoms with a high serum estradiol (E2) concentration. These results suggest that leuprorelin acetate plus hMG administration successfully stimulates the development of multiple ovarian follicles for oocyte retrieval and that the serum E2 concentration is predictive of OHSS‐like symptoms in chimpanzees.
Sudden Loading During a Dynamic Lifting Task: A Simulation Study
Authors: Andersen T. Bull , Simonsen E. B.
Published: March 2005

It is believed that nurses risk the development of back pain as a consequence of sudden loadings during tasks in which they are handling patients. Forward dynamics simulations of sudden loads (applied to the arms) during dynamic lifting tasks were performed on a two-dimensional whole-body model. Loads were in the range of −80kg to 80 kg, with the initial load being 20 kg. Loading the arm downwards with less than that which equals a mass of 20 kg did not change the compressive forces on the spine when compared to a normal lifting motion with a 20 kg mass in the hands. However, when larger loads (40 kg to 80 kg extra in the hands) were simulated, the compressive forces exceeded 13 000 N (above 3 400 N is generally considered a risk factor). Loading upwards led to a decrease in the compressive forces but to a larger backwards velocity at the end of the movement. In the present study, it was possible to simulate a fast lifting motion. The results showed that when loading the arms downwards with a force that equals 40 kg or more, the spine was severely compressed. When loading in the opposite direction (unloading), the spine was not compressed more than during a normal lifting motion. In practical terms, this indicates that if a nursing aide tries to catch a patient who is falling, large compressive forces are applied to the spine.
Autopsy
Authors: Camp Paul R.
Published: March 2005

The teaching literature is filled with accounts of successful course experiments. Unsuccessful experiments go largely unreported. Believing that the knowledge of how others have met trouble is often of as much use to the experimenter as is knowledge of successful ventures, we break with tradition and report a failure. The course discussed is a one-semester general physics course for nonscience majors who had already taken a one-semester descriptive physics course. There was much we tried to do and, in retrospect, much which we would do otherwise or not at all. But, some things we would do again, and again.
Spin flip enhancement at resonant transmission
Authors: de Menezes O. L. T. , Helman J. S.
Published: March 2005

The spin flip cross section for an electron which interacts by exchange in going through a layer of magnetic impurities can be greatly enhanced in a situation of resonant transmission. We describe this effect by a one-dimensional model which contains the essential physics and can be exactly solved. Besides its eventual application in problems related to the emission and reflection of spin polarized electrons, this model provides a nice and instructive quantum mechanical example.
On the motion of an ice hockey puck
Authors: Voyenli K. , Eriksen E.
Published: March 2005

Some easily observed, but surprising properties, of a homogeneous, circular ring or disk sliding on a smooth horizontal surface under the action of friction are pointed out and discussed.
Acceleration without radiation
Authors: Abbott Tyler A. , Griffiths David J.
Published: March 2005

We study the radiation generated by electric currents in (1) infinite cylinders with longitudinal flow, (2) infinite cylinders with solenoidal flow, and (3) infinite planes. In each case we work out four specific examples, for which the retarded fields can be calculated exactly, and we derive a ‘‘Larmor-like’’ formula for the power radiated, in the limit of infinitesimal cross section. We then consider sinusoidal currents with finite cross section, and discover that for certain special frequencies the external fields are zero and there is no radiation. We relate our results to the work of Goedecke and others, and conclude with some remarks on the radiation reaction in these configurations.
Instructional video in a university physics program
Authors: Kenealy Patrick F.
Published: March 2005

Wayne State University is located in an urban setting where daytime scheduling of intermediate and advanced courses presents severe access problems to working students. Five years ago we began videotaping entire classroom lectures and offering registration in special video sections. The video student has the benefit of flexible scheduling, access to regular faculty, and the same treatment as regular students. Another video-based program involves production of brief videotaped introductory modules for the introductory laboratories. Undergraduate laboratories staffed by TAs are beset by a number of chronic problems which are addressed by this program. We describe the production facilities, the everyday operation, the advantages and disadvantages, and the affordable economics of the programs.
Rebuttal to ‘‘On the adequacy of Newtonian particle mechanics for solving the rigid double pendulum problem’’
Authors: Stadler W.
Published: March 2005

This article comments on the remarks by Felszeghy [Am. J. Phys. 53, 230 (1985)] regarding an earlier article in this journal [W. Stadler, Am. J. Phys. 50, 595 (1982)].
Bell’s theorem and the foundations of quantum physics
Authors: Stapp Henry P.
Published: March 2005

A locality property expressing the idea that causal influences can propagate only forward in time, from earlier cause to later effect, and no faster than light is shown to be mathematically incompatible with certain predictions of quantum theory. The contradiction is proved without invoking any additional assumptions such as realism or hidden variables that contravene conventional quantum thinking. The failure of this locality property refines ideas about the theory of relativity, and opens the way to an objective interpretation of quantum theory that may expand its domain of applicability outside the one circumscribed by the orthodox Copenhagen interpretation.
Straight boomerang of balsa wood and its physics
Authors: Vos Henk
Published: March 2005

Construction of a light straight boomerang of balsa wood and the method of throwing it are described. The physical explanation of its return flight is given. The theory is entirely different from the usual one for boomerang flight. A reproducible transition from an unstable rotation to a stable, longitudinal spin plays an essential role.
Energy levels of a finite-step three-dimensional potential box: A perturbation approach
Authors: Ghatak A. K. , Kumar Arun , Thyagarajan K.
Published: March 2005

We present a simple and accurate first-order perturbation approach for calculating the energy levels in a finite-step three-dimensional potential box for which exact analytical solutions are not available.
Picture of an essential singularity
Authors: Daniels J. M.
Published: March 2005

The structure of an essential singularity is described in terms of concepts, such as multipole moments and phasors, familiar to students of physics and electrical engineering. This is illustrated with the exponential, trigonometric, and gamma functions, using the transformation z=1/w to transform the point at infinity to the origin. It is shown that the familiar property of rational functions—that their properties are determined by the positions of their poles and zeros—can be extended to transcendental functions.
Fourth component of relativistic forces
Authors: Stephas Paul
Published: March 2005

The Lorentz scalar interaction gives rise to a fourth component of the relativistic four-force which has a different form than that of the vector interaction, the difference arising from the variable mass for particles interacting through the scalar potential as compared to the constant mass for particles interacting through the vector potential. The Lorentz scalar potential, with its pedagogically interesting dynamics, is rarely mentioned in intermediate-level or first-year, graduate-level textbooks.
Energy balance in the superposition of light waves with lossless beam splitters
Authors: Pi F. , Orriols G.
Published: March 2005

The energy balance in the superposition of light waves with a lossless beam splitter is analyzed along with its connection with some general relations between the parameters describing beam-splitter effects on the two incoming waves. These general relations are derived either from the electromagnetic theory or from energy conservation considerations. The apparent paradox of a symmetric beam splitter producing complementary outputs is explained.
Study of the eigenvalues of a nonuniform string
Authors: Fulcher Lewis P.
Published: March 2005

Eigenvalues and eigenfunctions of a string whose ends are fixed and whose density is a linear function of position are presented. Some of the results are obtained using analytic expressions for Airy functions, but most are obtained with a Runge–Kutta numerical scheme. A simple formula for the eigenvalues is derived in the limit of a large nonuniformity parameter.
Simple first-order test of special relativity
Authors: Byl John , Sanderse Martin , van der Kamp Walter
Published: March 2005

This paper reports on a simple experiment for testing the isotropy of the speed of light. It is based on a method which yields a first-order sensitivity in (v/c).
Sphere rolling down a grooved track
Authors: Bachman R. A.
Published: March 2005

The motion of a uniform sphere rolling without slipping down a grooved track is discussed in detail. Using elementary mechanics, a formula is derived for the final speed as a function of groove width, sphere radius, and track height. The physical mechanism causing this functional dependence is explained. It is shown that a minimum coefficient of static friction must be available to maintain the motion. An experimental procedure is described for measuring the sphere’s speed using projectile physics. Results are in good agreement with theoretical predictions, clearly showing that the presence of the groove can significantly reduce the translational motion of the sphere.
A cartoon-assisted proof of Sarkowskii’s theorem
Authors: Kaplan Harvey
Published: March 2005

Much of the present article serves as an introduction to a set of ideas familiar in dynamical systems theory. No familiarity with these ideas is assumed on the part of the reader. The ideas are then combined in simple, geometric arguments to prove Sarkowskii’s theorem. This theorem is important in the study of one-dimensional, deterministic, dissipative dynamical systems. It provides a unified framework for the occurrences of both orderly and chaotic motions. The relationship of the mathematical models discussed here to real physical and biological systems is discussed briefly and the reader is referred to the literature for descriptions of diverse, beautiful, relevant experiments.
A comparison of explanations of the aerodynamic lifting force
Authors: Weltner Klaus
Published: March 2005

The frequently used explanation of the aerodynamic lifting force using Bernoulli’s law is shown to have fundamental drawbacks and incomplete reasoning. On the other hand, an explanation based on repulsion forces is shown to be complete, easier to assimilate, more powerful, and better related to the basic principles of mechanics. Furthermore, it is shown that the high streaming velocity at the upper side of the aerofoil is not the reason for the low pressure. To the contrary, the low pressure generated by the aerofoil is the reason for the high streaming velocity.
The fly ball trajectory: An older approach revisited
Authors: Tan A. , Frick C. H. , Castillo O.
Published: March 2005

An older approach to the problem of projectile motion with quadratic drag force is presented with the fly ball as an example. In this approach, analytical solutions for the velocity, curvature, and arc length are obtained as functions of the slope angle. It is shown that the velocity and curvature do not have their extrema at the top of the trajectory but during the early phase of descent. The entire problem is reduced to simple integrations over the slope angle.
The floating plank
Authors: Delbourgo R.
Published: March 2005

The stable floating configuration of a long plank of rectangular cross section depends on the relative density of the plank to the fluid and on the ratio of the sides. The complete solution of this metacentric problem is given.
Proper treatment of the delta function potential in the one-dimensional Dirac equation
Authors: Calkin M. G. , Kiang D. , Nogami Y.
Published: March 2005

It is pointed out that the usual treatment of the delta function potential in the one-dimensional Dirac equation is incorrect. Steps leading to such incorrect results are identified. The delta function potential is also examined from the limiting case of a nonlocal potential V(x,x′). In this general case, the strength g=∫dx ∫dx′V(x,x′) is no longer a sufficient parameter to characterize a potential.
A simple geometrical model of spontaneous symmetry breaking
Authors: Aravind P. K.
Published: March 2005

A common, everyday phenomenon has a geometrical aspect that, in some respects, is analogous to a second-order phase transition. Concepts such as spontaneous symmetry breaking, order parameter, critical point, and critical exponent can thus be exhibited in a purely geometrical context. The purpose of the model, which is entirely pedagogical, is to illustrate in an elementary and amusing way some of the concepts associated with phase transition theory.