bluuebunny/crossref_metadata_2025_split huggingface dataset:
A SYSTEM OF HEALTH STATISTICS TOWARD A NEW CONCEPTUAL FRAMEWORK FOR INTEGRATING HEALTH DATA
Authors: Wolfson Michael C. 
Published: March 2005

In this paper the author outlines a broad new conceptual approach to the organization of health statistics data for Canada. It represents the initial thinking in a longer term project directed towards the review of the basic form and content of Statistics Canada's program of health statistics. Two major concerns have given rise to the project. First is the general lack of coherence in health data, as compared for example to the System of National Accounts. Second is a widely perceived imbalance in data collection efforts that places too much weight on the resources devoted to provision of health care and not enough on the health status of the population–both in terms of distribution and temporal trends. These concerns are reviewed, and then a new conceptual framework within which these concerns could be met is suggested.“Her account of the voyage was considerably more interesting than the account of expenses incurred; but she was asked to account for spending so much of the voyage visiting minor satellites rather than seeking a broad overview of the entire system.”
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.
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

PurposeThe effects of oblique compressive forces were evaluated for extracted teeth restored with posts of solid and internally threaded designs.Materials and MethodsA 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.ResultsNo statistical difference was shown between groups for either fracture force or type.ConclusionsThe 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

PurposeThe fatigue resistance of heat‐polymerized acrylic resin test specimens reinforced with continuous glass fibers or metal wire was investigated.Materials and MethodsTest 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.ResultsResults 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).ConclusionsThis 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.
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.
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.