bluuebunny/crossref_metadata_2025 huggingface dataset:
CHINA'S GDP LEVEL AND GROWTH PERFORMANCE: ALTERNATIVE ESTIMATES AND THE IMPLICATIONS
Authors: Wu Harry X.
Published: March 2005

This study critically evaluates alternative estimates of China's GDP level and growth, as well a s its PPP GDP conversions, and, based on this evaluation, it draws important implications for the understanding of China's economic performance in both historical and international perspectives. It finds that although almost all empirical results have supported the downward‐bias hypothesis for China's GDP level and the upward‐bias hypothesis for China's GDP growth, they vary greatly, and that PPP estimates for China are also diversified. These estimates, if accepted, may substantially alter the existing views on the Chinese economy, particularly, its size, TFP level and catch‐up performance. The discussion focuses on the theories, methodologies and data used in these studies, and particularly, the possible biases in their results thereby. It argues, however, that despite differences in estimates, they could still provide sensible boundaries for researchers to gauge the “real” values and hence assess China's “real” living standard and growth performance.
Color Stability of Selected Dual‐Cure Composite Resin Cements
Authors: Berrong Joseph M. , Weed Roger M. , Schwartz Ivy S.
Published: March 2005

Purpose This in vitro study was conducted to determine the color stability of five dual‐cure composite resin cements: Kerr Porcelite (Kerr Manufacturing Co, Romulus, NY), Jelenko PVS System (J.F. Jelenko and Co, Armonk, NY), Vivadent Heliolink (Vivadent USA, Amherst, NY), Mirage FLC (Chameleon Dental Products, Inc, Kansas City, KS), and Den‐Mat Ultra Bond (Den‐Mat Corp, Santa Maria, CA).

Materials and Methods Each cement was used to lute two 10 mm circular Vita VMK porcelain disks 0.75 mm in thickness. The surfaces to be luted were sand blasted and a silane coupling agent applied. The natural glaze was unaltered. Manufacturer's directions were followed for manipulation of the cements. A jig was used during the application of the resins to control cement thickness. The samples were stored in distilled water at 37°C. Using a Hunter Tristimulus Colorimeter (Hunter Associates Laboratory, Inc, Reston, VA), values were obtained for each specimen immediately, at 24 hours, and at 1,2,3,4,8,12,16,20, and 24 weeks.

Results An analysis of variance (ANOVA) showed significant differences for all specimens. Using the Scofield Hunter formula for identifying color differences (ΔE), at 24 hours, and 24 weeks, Vivadent Heliolink showed the least color changes (24 hours ΔE = 0.82, 24 weeks ΔE = 0.98) and Kerr Porcelite the greatest (24 hours ΔE = 3.94, 24 weeks ΔE = 4.73).

Conclusions All dual‐cure composite resin cements in this study showed short‐term and long‐term color change. Vivadent Heliolink showed the least color change, while Kerr Porcelite showed the most change.
Infection Control in a Prosthodontic Residency Program
Authors: Brandt Robert L. , Coffey James P. , Baker Philip S.
Published: March 2005

Awareness of the need to incorporate an effective infection control program within a prosthodontic practice requires the faculty of a prosthodontic residency program to present a clear and workable model that will allow the flexibility necessary to accommodate the changes in infection control procedures and materials. The use of the barrier system to insulate the operatory, resident, faculty, and dental laboratory is discussed. Current disinfection and sterilization methods used to maintain the barriers are recommended.
An Investigation of the Rheological Properties of 10 Vinyl‐Polysiloxane Impression Materials
Authors: Chai John , Pang Iok‐Chao , Leong Dennis , Kim Jung E. , Torres Pablo
Published: March 2005

Purpose The time required for 10 vinyl‐polysiloxane impression materials to reach a viscosity of 5000 poise (Tcv) was estimated. This viscosity was selected based on previous work that suggested that an impression material might not be workable if its viscosity exceeded this limit. The effect of variations in the time of placement of the impression materials into a simulated oral‐temperature environment was also studied.

Materials and Methods The change in the viscosity of the impression materials was recorded with a viscometer at oral temperature. Impression materials were placed at either 20 seconds, 30 seconds, or 40 seconds from the start of mixing.

Results There were statistically significant differences in Tcv among various impression materials. Variations in placement time significantly affected the Tcv of six impression materials.

Conclusions Knowledge of the viscosity change of an impression material is beneficial in the clinical selection of an impression material.
Fabricating Crowns to Fit Existing Removable Partial Dentures: An Illustration of Two Techniques
Authors: Macpherson Jeff R. , Evans Douglas B.
Published: March 2005

The prosthetic treatment of a structurally compromised abutment tooth supporting a removable partial denture may present a variety of restorative modalities. Ideally, a surveyed crown is made for the individual tooth, which is later followed by a new removable partial denture fit to the contours of the crown. Frequently, however, the removable partial denture is clinically acceptable, and remaking the prosthesis is not indicated. In these cases, the crown can be made to fit the existing removable partial denture. Fabricating crowns to fit existing removable partial dentures can be accomplished using a direct method, an indirect method, or combinations of these techniques. Direct techniques traditionally use acrylic resin and inlay wax intraorally to develop a custom pattern that captures the contours of the clasp assembly. Indirect techniques use a pick‐up impression to allow the crown pattern to be waxed against the denture framework on a cast in the laboratory. Combination methods use either a direct‐indirect or indirect‐direct approach. The direct‐indirect method develops the preliminary resin pattern directly on the tooth and finalizes the contours in wax on a master cast. The indirect‐direct technique initiates a crown pattern on a die and completes it either intraorally or on the die after the intraoral refinements. This article reviews the literature for methods of fabricating surveyed crowns under existing removable partial dentures. Additionally, two cases are presented that illustrate an indirect and combination direct‐indirect technique for making the restorations.
Effect of Immersion Disinfection on Properties of Impression Materials
Authors: Davis Bianca A. , Powers John M.
Published: March 2005

Purpose

Dimensional change and wettability were determined for three addition silicones and a polyether impression material after disinfection by immersion for two 30‐minute cycles in 2% acid‐potentiated glutaraldehyde.

Materials and Methods

Contact angles of water on disks were measured on a goniometer. Dimensional change was determined by change in distance between two reference lines. Contact angle (degree) and dimensional change (percent) of five samples were measured after 0‐, 30‐, 60‐, and 1,440‐minute intervals of storage in air and disinfectant.

Results

The contact angle in air increased for two addition silicones and remained constant for the remaining materials. In disinfectant, the contact angle increased for all four materials, with the contact angle of the polyether increasing the least. In air, dimensional change decreased significantly for an addition silicone and a polyether. In disinfectant, the dimensional changes of the addition silicones were not significant, but the polyether increased in dimension after 1,440 minutes.

Conclusions

Two 30‐minute cycles of disinfection in 2% acid‐potentiated glutaraldehyde reduced wettability, but had little effect on the dimensional change of the addition silicones and polyethers tested.
Comparison of the Photoelastic Stress for a Split‐Shank Threaded Post Versus a Threaded Post
Authors: Cohen Brett I. , Lee Musikant Barry , Deutsch Allan S.
Published: March 2005

Purpose

This study compared the stress distribution during insertion and after cementation for two prefabricated endodontic posts, (1) a split‐shank threaded post, and (2) a threaded post with no split in the shank.

Materials and Methods

Three test blocks of photoelastic material were prepared with simulated endodontic canals for each group studied. Specimens were then photographed after insertion and cementation.

Results

Mininal stresses were observed for the post with a split (group 1) throughout the length of the shaft, whereas asymmetric patterns of stresses for the post without a split (group 2) were present. Stress distribution for the post without a split were concentrated more apically rather than coronally.

Conclusions

The presence of a split reduces insertion and cementation stresses for this post system. The split also acts as a vent during the cementation of the post into the canal and minimizes stress concentration during cementation.
Adhesion Promotion Between Metadent and a High Palladium Alloy With a Pyrolytically Fused Porcelain Opaque Layer
Authors: van Putten Meade C. , Culbertson Billy M.
Published: March 2005

Purpose

Several authors have reported a preference for the use of high palladium alloys in the construction of implant‐fixed partial denture (IFPD) substructures. Heat‐polymerized polymethyl methacrylate resins (PMMR) are used to secure denture teeth to IFPD substructures. Metadent (Sun Medical Co, Kyoto, Japan), a heat‐polymerized PMMR containing 5% 4‐methacryloxyethyl trimellitate anhydride (4‐META), could possibly improve the overall design of the prosthesis because this resin adheres to resin and ceramic denture teeth and noble metals. However, adhesive bonding between Metadent and elemental palladium has been shown to be poor. The purpose of this study was to evaluate the potential for adhesive bonding between Metadent, titanate primers, and a ceramic layer pyrolytically fused to a high palladium alloy.

Materials and Methods

Five groups of 10 specimens were prepared. A layer of opaque porcelain was baked on all of the specimens under vacuum at 1760°F. The specimens were grouped as follows: (1) Metadent resin processed on ceramic with no primer, (2) Metadent resin with 10% ethyl acetoacetate titanate (DC) processed on ceramic with no primer, (3) Metadent resin with 10% DC processed to ceramic with a 2% tetraisopropyl (TPT) surface primer, (4) 4‐Metadent resin with 10% DC processed to ceramic with a 2% isopropyl dimethacryloyl isostearoyl titanate (KR‐7) surface primer, and (5) Metadent resin with 10% DC processed to ceramic with a titanium dioxide layer on the opaque and a KR‐7 surface primer. The primers were in a methyl methacrylate (MMA) solution. All of the specimens were heat‐polymerized under pressure at 212°F for 1 hour. One‐half (25) of the specimens (5 from each group) were hydro‐thermocycled at 4°C to 55°C, 0.5 minute dwell per bath for 3,000 cycles. All specimens were tested in shear on an MTS Universal machine at cross head speed of 0.5/mm/min.

Results

The results showed adhesion between the resin‐ceramic layer in virtually all groups regardless of thermocycling effects. The control (heat cure without 10% DC and no primer) and the 10% DC with KR‐7 and TPT primer groups had an average MPa of 7.5, 7.7, and 7.0, respectively. The failure mode of the specimens was adhesive, with the site of failure being the porcelain‐metal interface

Conclusion

It was concluded that adhesion between palladium alloy and Metadent was possible when a ceramic layer was used as an intermediary interface. The limitation seemed to be the adhesion of the ceramic to the metal.
Postsurgical Timing of Restorative Therapy: A Review
Authors: Dowling Embree A. , Maze Glenn I. , Kaldahl Wayne B.
Published: March 2005

Knowledge of wound healing is necessary for the clincian when determining the time of prosthodontic treatment after periodontal surgery. Wound healing and longitudinal clinical studies indicate that the clinician should wait approximately 8 weeks before proceeding with the final restoration. Restorative procedures could be considered as early as 6 weeks if (1) the patient shows good systemic health; (2) injury is not inflicted on the gingiva by the restorative technique; (3) restorative margins are supragingival; and (4) esthetics are not critical. With a thick periodontium, more common in posterior areas, the gingiva often will move coronally as the tissue matures. Thin periodontal tissues may recede postsurgically, and in areas of esthetic concern, postponement of final restoration for up to 5 to 6 months may be desirable to assure gingival margin stability. Modifiers that may affect time and quality of healing, such as the patient's smoking frequency and age, should be considered when scheduling restorative treatment after periodontal surgery.
Endotoxin Affinity for Provisional Restorative Resins
Authors: Gagnon François , Knoernschild Kent L. , Payant Lise , Tompkins Geoffrey R. , Litaker Mark S. , Schuster George S.
Published: March 2005

Purpose

This study compared the relative affinity of Porphyromonas gingivalis and Escherichia coli endotoxin, bacterial cell envelope lipopolysaccharide (LPS), for three provisional resins.

Materials and Methods

As‐polymerized and pumiced polymethyl methacrylate and polyethyl methacrylate resin discs were exposed to 1,000 endotoxin U/mL P.gingivalis or E. coli LPS in water for 24 hours at 37°C, whereas control discs were placed in LPS‐free water. LPS‐treated discs were transferred at 24‐hour intervals to fresh, LPS‐free water for up to 96 hours, and the incubated eluates were tested for the presence of LPS.

Results

Initial adherence of P. gingivalis LPS to as‐polymerized and pumiced‐finish resin was a function of resin type, but surface characteristics modified adherence levels. When steady rates of elution were reached at 72 to 96 hours, as‐polymerized specimens released significantly greater LPS levels than pumiced samples. Comparison of initial adherence of P. gingivalis and E. coli LPS with pumiced resins showed that adherence was based on a combination of LPS and resin type. P. gingivalis LPS had a greater relative affinity for polyethyl methacrylate, and E. coli LPS had a greater relative affinity for polymethyl methacrylate. Regardless of resin type, P. gingivalis LPS eluted at levels greater than E. coli LPS.

Conclusions

The affinity of LPS for provisional resins seems to be a function of selective interactions based on the chemical nature of the resin, the surface finish of the resin, and the molecular structure of the LPS.
Durability of Resin Bonds to Pure Titanium
Authors: Kern Matthias , Van Thompson P.
Published: March 2005

Purpose This study evaluated the bond strength and bond durability of new adhesive systems to pure titanium.

Materials and Methods Plexiglass tubes filled with composite were bonded to titanium discs. Groups of 24 samples were bonded using six different bonding systems. Subgroups of eight bonded samples were stored in an isotonic artificial saliva solution (37°C) for 1, 30, or 150 days. In addition, the 30‐ and 150‐day samples were thermal cycled for 7,500 or 37,500 cycles between 5°C and 55°C, respectively. After these storage conditions, all samples were debonded in tension.

Results The bond strength of a conventional bisphenol‐A glycidyl methacrylate composite to sandblasted titanium was significantly lower than using chemomechanical bonding systems and decreased slightly during the storage time of 150 days. The additional use of a silane on sandblasted titanium resulted in an insignificant increase in bond strength and decreased over storage time to the same level as on sandblasted‐only titanium. Statistically significant higher bond strengths were achieved either with the combination of silica coating and use of a conventional bisphenol‐A glycidyl methacrylate composite or with the combination of sandblasting and the use of composites modified with a phosphate monomer. In the latter systems, the bond strengths were only limited by the cohesive strength of the composite resins. A new phosphate monomer containing composite showed a tendency to lose cohesive strength over time (statistically not significant).

Conclusions Using chemomechanical bonding systems, ie, silica‐coating systems or modified composites with adhesive monomers, resulted in 2 to 2.5 times increased bond strength to titanium compared with the bond strength of a conventional bisphenol‐A glycidyl methacrylate composite. With chemomechanical bonding systems, the resin bond to titanium was durable over 150 days, even after being stored in water and thermal cycled.
The Use of Clinical Computer Workstations as an Educational Adjunct in Prosthodontics
Authors: van Putten Meade C.
Published: March 2005

Current computer systems improve the health professional's ability to store, retrieve, and present visual data in a way never before possible. Health professionals in general are beginning to use computer‐based digital imaging to improve the diagnosis and treatment planning of disease processes. The use of computer‐based networks to transmit medical and dental data is in its infancy but promises to be the main form of data transmission of the future. This article outlines a few applications presently being used and developed at the Ohio State University College of Dentistry in the preclinical and clinical courses in prosthodontics.
Modifications in the Design and Fabrication of Mandibular Osseointegrated Fixed Prostheses Frameworks
Authors: von Gonten Ann Sue , Medina Teofilo , Woolsey Gerald D. , Hill David R.
Published: March 2005

This article presents the advantages of design modifications and fabrication techniques for mandibular osseointegrated fixed prostheses. These design features provide definite mechanical advantages and access for oral hygiene maintenance. A review of implant surface properties is presented that affect bacterial plaque and food debris adherence. The suggested design involves a lingual contour of the cast alloy suprastructure to yield an environment for reduced plaque and debris accumulation. The right angle cross‐section ensures strength and increased stress distribution in structurally compromised areas when compared with conventional implant framework designs.
Implant‐Supported Restoration of a Mandibular Reconstruction With an Osteocutaneous Microvascular Free Flap: A Clinical Report
Authors: Baima Robert F.
Published: March 2005

The microvascular osteocutaneous fibula free flap can provide an esthetic restoration of mandibular discontinuity defects. When the graft is favorably positioned, osseointegrated implants may be placed and a functional restoration completed. When tongue function is not compromised, the patient is able to control saliva and the food bolus and can show excellent speech. This clinical report of a patient who has undergone a mandibular resection, fibula free flap reconstruction, and implant‐supported fixed prosthodontic restoration shows such treatment.
Patient Appointments During Interim Obturation: Is It Cost‐Effective?
Authors: King Gordon E. , Chambers Mark S. , Martin Jack W.
Published: March 2005

Purpose The purpose of this study was to quantify the number of patient appointments needed during the interim obturator service period in the Department of Dental Oncology at MD Anderson Cancer Center (Houston, TX).

Materials and Methods A retrospective study evaluating 100 patient records of patients who underwent maxillectomies between 1989 and 1993.

Results Of the 100 patients analyzed, 42 patients had a definitive prosthesis fabricated within 90 days after surgery. On average, 12 appointments (range, 6‐24 appointments) were recorded for each patient during this 90‐day global interim obturator period.

Conclusions The 12 appointments reflect a considerable amount of clinical and laboratory effort and reinforces the national concern of proper reimbursement.
Contact Damage as a Failure Mode During In Vitro Testing
Authors: Harvey Charles K. , Kelly J. Robert
Published: March 2005

Purpose

The purpose of this study was to identify the failure mode(s) for all‐ceramic crowns tested in vitro and to determine whether measured failure loads in this type of testing would be influenced by indenter radii (a classic Hertzian cone‐crack variable) and specimen thickness.

Materials & Methods

Fracture surfaces and failure probability data from glass‐ceramic cuspids (50 = n) tested in a previous in vitro study were examined to determine their mode of failure. To further evaluate the failure mode identified for the crowns, 100 ceramic platelets (50 glass‐ceramic, 50 feldspathic porcelain) were loaded to failure beneath spherical indenters (radii, 0.75‐94 mm).

Results

Glass‐ceramic cuspids failed from blunt contact damage at the point of loading (with Hertzian stress‐state damage evident). Ceramic platelets exhibited failure from either the indentation surface (Hertzian cone‐cracking present) or from the supported surface (ie, mimicking bending failure). Failure‐loads increased with the indenter radius for both failure modes. Failure from blunt contact damage occurred at markedly higher loads than did failure from support‐surface sites.

Conclusions

Blunt indentation damage was identified as being the failure source for the glass‐ceramic cuspid crowns and a major failure mode for both feldspathic porcelain and glass‐ceramic platelets loaded beneath spherical indenters. This failure mode is not similar to that reported for clinically failed glass‐ceramic crowns. Influential testing variables were contact radius, ceramic thickness, and the surface finish of both the ceramic specimen and test platen.
Geometric Analysis of Occlusal Plane Orientation Using Simulated Ear‐Rod Facebow Transfer
Authors: Santos José dos , J. Nelson Stanley , Nummikoski Pirkka
Published: March 2005

Purpose

Ear‐rod facebow techniques may position casts high or low between the upper and lower members on the articulator when using orbitale or nasion as anterior reference positions. This study assessed the effect of changing the anterior reference position on simulated mountings utilizing simulated ear‐rod facebow.

Materials and Methods

Tracings from lateral cephalographs made on seven subjects were superimposed with an outline model of a semiadjustable articulator. Three simulated mountings were performed for each subject in which the plane of occlusion was positioned (1) high, (2) midway, and (3) approaching the lower member (low). Maxillary and mandibular occlusal planes representing intercuspal position were determined from the cephalographs and positioned on the articulator model in a simulated centric relation position for each mounting. Condylar guidance was determined from a simulated protrusive position.

Results

Analysis of the three mounting positions demonstrated no change in intercuspal position within subjects; however, angles formed between upper member and condylar guidance were 14.9% smaller for the mid‐distance mounting, 42.9% smaller for the high mounting, and 13.4% higher for the low mounting positions when compared with a standard Frankfort horizontal plane reference.

Conclusions

The cephalographs showed extreme variability in the position of the ear piece to bony structures of the skull, but this deviation appeared to be compensated by a change in the horizontal condylar guidance relative to mounting. Results also suggest that casts may be mounted in a convenient mid‐position for routine articulation.
Effect of Firing on the Color Stability of a Light‐Cured Ceramic Stain
Authors: Reis Rodrigo S. , Neiva Gisele F. , Yaman Peter , Razzoog Michael E.
Published: March 2005

Purpose

This study evaluated the color stability of four stains of a light‐cured porcelain stain system between the light‐cured and fired stages.

Materials and Methods

Thirty‐six ceramometal discs 20 mm in diameter and 2 mm in thickness were cast to provide the substrate on which Ceramco II porcelain was applied. The porcelain was polished to a uniform thickness of 2 mm, and the samples were divided into four groups and assigned a color (yellow, orange, green, or blue). Orbit LC stain was applied in a thin layer and light‐cured for 40 seconds. After light‐curing, three color readings were made with a Minolta Chroma Meter II. The porcelain discs were then fired in a porcelain oven and three color measurements were again made. The pre‐ and postfired Commission Internationale de I'Eclairage L*a*b* values were recorded and the color difference (ΔDLE) was calculated for each specimen. The clinical significance for the computed ΔDLE ratings was completed according to previously modified criteria.

Results

The results show that the mean ΔDLE between the light‐cured and fired stages of Orbit LC are clinically acceptable. No statistically significant differences (p < .05) were observed between any of the four groups.

Conclusions

A light‐cured porcelain stain system was evaluated for color stability between light‐cured and fired stages. Within the conditions of this study, the following conclusions can be made: (1) There was no clinically significant color difference between light‐cured and fired stages for the stain colors evaluated; and (2) the final color of the restorations altered with light‐cured stains can be predicted before firing.
Comparison of Strains Transferred to a Bone Simulant Between As‐Cast and Postsoldered Implant Frameworks for a Five‐Implant‐Supported Fixed Prosthesis
Authors: Clelland Nancy L. , Carr Alan B. , Gilat Amos
Published: March 2005

Purpose

To measure and compare the strains transferred by screw‐fastening one‐piece full‐arch prostheses as cast and after sectioning and soldering.

Materials and Methods

Photoelastic resin was applied directly to five 3.75 × 13‐mm Brånemark implants, situated 7 mm apart, in a silicone mold of an edentulous mandible. Four strain gauge rosettes were also incorporated in the resin to allow strain measurements at four locations. Three frameworks were made from a single master cast produced from an impression of the five‐implant model with 4‐mm abutments. These frameworks were sequentially secured to the master model with five gold slot screws tightened to 10 N cm. Strain indicator readings were recorded at a standardized time following the initial fastening of each prosthesis. The test was repeated three times. Each of the three castings were subsequently sectioned and soldered in two locations, mesial to the two terminal fixtures. After soldering, the three superstructures were returned to the master model for measurement of postsolder strains three times each. A one‐way repeated‐measures ANOVA was performed to determine differences between mean principal strains between the as‐cast and postsoldered groups.

Results

A statistically significant difference was found in the principal strains between the as‐cast and soldered frameworks. Overall, there was a decrease in the magnitude of strain for the soldered frameworks.

Conclusions

Sectioning and soldering improved the as‐cast accuracy as far as the amount of strain transferred to the bone simulant.
An Evaluation of Microwave‐Polymerized Resin Bases for Removable Partial Dentures
Authors: Loh Poey Ling , Munoz Carlos A. , Goodacre Charles J. , Andres Carl J. , Moore B. Keith
Published: March 2005

Purpose The hardness, porosity, and adaptation of removable partial dentures fabricated with one heat‐polymerized denture base resin and two resins designed for microwave polymerization were evaluated.

Materials and Methods Five prostheses were evaluated for each resin. Adaptation of the denture bases to the master cast was evaluated by spatial orientation and mean weight of residual impression material. The prostheses were then embedded in epoxy resin and sectioned for evaluation of resin hardness (Knoop hardness) and microporosity.

Results There were no significant differences in the adaptation of the acrylic resin bases for Acron MC and Ch Lucitone. There was no significant difference in the mean Knoop hardness values for any of the resin bases near and away from the metal. None of the denture bases showed porosity greater than 100 μm.

Conclusions Both resin bases formulated for microwave polymerization were effectively polymerized around metal frameworks without adverse effects on resin hardness or porosity. Justi Denture Base material had poorer base adaptation than the other two resins.
Transverse Strength, Ductility, and Qualitative Elemental Analysis of Cobalt‐Chromium Alloy After Various Durations of Induction Melting
Authors: Vallittu Pekka K.
Published: March 2005

Purpose The aim of this study was to compare the transverse strength and ductility of bars cast from cobalt‐chromium alloy that had been melted for various lengths of time (n = 5 per group). To determine its elemental composition, the cobalt‐chromium alloy was also analyzed qualitatively.

Materials and Methods Transverse strength and ductility of the cobalt‐chromium bars was measured by a three‐point loading test. Scanning electron microscopy (SEM) and energy‐dispersive spectroscopy (EDS) were used to determine the composition of the samples compared with unmelted cobalt‐chromium alloy.

Results The transverse strengths of the test bars cast from the cobalt‐chromium alloy, which had been induction‐melted for various lengths of time, did not differ significantly (p= .056); but the ductility of the test bars was affected by the duration of induction melting of the alloy (p < .001). According to the SEM/EDS analysis, the amount of silicon in the cobalt‐chromium alloy decreased with lengthening duration of induction melting of the alloy.

Conclusions This study supports the previous finding that good resistance to deflection fatigue is correlated with increased ductility of cobalt‐chromium alloy and vice versa.
Placement and Restoration of Implants by Predoctoral Students: The Creighton Experience
Authors: Wilcox Charles W. , Huebner Gene R. , Mattson John S. , Nilsson Dennis E. , Blankenau Richard J.
Published: March 2005

Teaching of implant dentistry in the predoctoral dental curriculum has evolved dramatically over the past 20 years. In 1974, only one third of American dental schools addressed the topic of implants. Today, 48 of the 54 American dental schools have predoctoral curricula. The Creighton University experience offers some unique and instructive insights into a 10‐year process of developing and implementing a predoctoral implant dentistry curriculum. All interested students may perform both the surgical placement and restoration of implant prostheses. Clinical instruction involves all restorative and surgical faculty members. Favorable 3‐year (91%) and 5‐year (87%) surgical success rates have been maintained. This article presents one university's program for examination and discussion.
Wear of Visible Light‐Cured Restorative Materials and Removable Partial Denture Direct Retainers
Authors: Latta George H. , Wicks Russell A. , Huget Eugene F. , Murray Granville A.
Published: March 2005

Purpose This study measured the in vitro wear of visible light‐cured restorative materials and removable partial denture direct retainers.

Materials and Methods An aluminum test die was produced by replicating the facial contours of an extracted human molar (model). The replica's cervical contour was modified by placement of a restorable Class V cavity preparation. The test die became a fixed component of a testing apparatus. The restorative materials tested were Z100 (fine particle filled resin composite), Silux Plus (microfilled resin composite), and Photac‐Fil (hybrid glass ionomer). Cast round, half round, I bar, and wrought‐wire retainers were designed to engage a 0.254‐mm undercut. Caliper measurements of the wear of restorative materials were made at intervals during testing, and after 7,500 retainer placements and removals. The measurements of material‐ and retainer‐wear were subjected to ANOVA and Tukey tests.

Results Generally, retainers with round profiles caused less wear of the restorative materials than those featuring flat contact surfaces. Wear of the materials ranged from 14 ± 5.5 μm (Silux Plus by cast round) to 70 ± 10.0 μm (Photac‐Fil by cast half round). Mean wear of retainers, however, ranged only from 2 ± 4.5 μm for six of 12 possible retainer‐material pairings up to 12 ± 4.5 μm (cast half round by Z100).

Conclusions Regardless of their design features, the direct retainers of this study exhibited little wear when paired with any of the restorative materials. Overall, material wear appeared to be greater than retainer wear by a factor of five. When paired with practically any retainer type, the hybrid glass ionomer (Photac‐Fil) exhibited more wear than either of the two resin composites (Z100 or Silux Plus). Although not established clearly, retainers with round profiles (wrought‐wire and cast round) appeared to produce less wear of restorative materials than their I bar and cast half round counterparts.
Effectiveness of Computer‐Aided Removable Partial Denture Design
Authors: Lindquist Terry J. , Clancy James M. S. , Johnson Lynn A. , Wiebelt Frank J.
Published: March 2005

Purpose Computer programs have been developed for removable partial denture (RPD) design, but their educational impact has never been investigated. This study measured the effectiveness of computer‐based RPD design simulations in a traditional RPD design course for second‐year dental students.

Materials and Methods Thirty‐six students were randomly assigned to four groups, two simulation and two control groups, at the beginning of the RPD design module. A cross‐over design compared the two strategies during laboratory exercises. First, the simulation group worked with the simulation, while the control group met in small‐group seminars with faculty. Post‐test 1 was given, and then students switched teaching methods and post‐test 2 was given. Each post‐test had two parts. Part 1 involved designing an RPD based on specific patient criteria. Part 2 involved choosing the more correct of the two designs.

Results Results showed a significant difference (p= .0072) in two of four test groups. Although it was an initial evaluation, the computer simulation was shown to be equivalent to faculty‐led small‐group seminars. Students also responded positively to a questionnaire on their perceived effectiveness of the simulations.

Conclusions The results suggest that RPD design can be taught as effectively with computer‐based simulations as with faculty‐led seminars.
Use of a Surgical Template for Autologous Bone Grafting of Alveolar Defects
Authors: Misch Craig M.
Published: March 2005

This article describes the fabrication of a surgical template for planning and performing the harvest and placement of autologous bone grafts for the reconstruction of alveolar defects before implant placement. A diagnostic cast is altered to replicate the anticipated bone anatomy. The ideal bony contours for implant placement are then created on the cast to form the template. This template may then be used for treatment‐planning donor sites for the harvest of corticocancellous bone grafts. The template is sterilized and used by the surgeon in procuring and placing the bone graft. This template allows communication of the prosthetic requirements of the ridge augmentation, as well as ensuring adequate volume and proper positioning of the block graft for eventual implant placement.
Oral Rehabilitation of a Child with Primary Failure of Tooth Eruption
Authors: Siegel Sharon Crane , O'Connell Anne
Published: March 2005

This article describes the prosthetic evaluation and treatment of a 10‐year‐old female patient with primary failure of tooth eruption. This case is unique in that the failure of eruption affected both the deciduous and permanent dentition in all quadrants, in the absence of any other systemic abnormalities. After diagnostic articulation and a thorough discussion of the treatment with the patient and her parents, complete maxillary and mandibular overdentures were fabricated. The process followed with this preadolescent patient to ensure maximum compliance, success, and encouragement toward a positive attitude in wearing complete dentures is reported.
Hematological and serum biochemical values in cynomolgus monkeys anesthetized with ketamine hydrochloride
Authors: Kim Choong‐Yong , Lee Hyun‐Sook , Han Su‐Cheol , Heo Jeong‐Doo , Kwon Myung‐Sang , Ha Chang‐Su , Han Sang‐Seop
Published: March 2005

Abstract:  The effects of ketamine anesthesia on both hematological and serum biochemical variables were investigated in 19 male and 15 female cynomolgus monkeys. Blood samples were obtained from the cephalic vein within 30 minutes of an intramuscular injection of ketamine hydrochloride (10 mg/kg). Ketamine anesthesia caused a reduction in leukocyte counts and a significant reduction in lymphocytes percentages. Ketamine anesthesia also increased the serum activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatine phosphokinase (CPK), but reduced the serum concentrations of glucose, inorganic phosphate, sodium and potassium. The alterations of hematological and serum biochemical values will be discussed. These alterations should be considered when designing studies for and interpreting data from cynomolgus monkeys.
Dental trauma incidence and mouthguard use in elite athletes in Turkey
Authors: Keçeci Ayşe Diljin , Eroḡlu Erdal , Baydar Metin Lütfi
Published: March 2005

Abstract –  Contact sports may lead to dental trauma, which often can be reduced with appropriate preventive measures. While numerous studies exist on this topic for several countries throughout the world, there is a lack of comprehensive descriptive studies in Turkey. The purpose of this study was to investigate the incidence and type of dental injuries associated with three different sports among Turkish elite athletes, who do not contact (volleyball), contact directly (taekwondo) or indirectly (handball) with competition rivals. Additionally, awareness and use of mouthguards were also compared. Thus, during the 2003 and 2004 Turkish National Championships in three sports, 50 taekwondo, 62 handball and 50 volleyball male athletes were interviewed by questionnaire. Results showed that taekwondo and handball athletes experienced significantly more dental trauma than volleyball athletes (P < 0.05). Twelve of the taekwondo (24%), 16 of the handball (26%) and four of the volleyball athletes (8%) experienced at least one type of dental injury. Awareness of mouthguards as a preventive measure against dental trauma was significantly higher among taekwondo and handball athletes (P < 0.05), although a very small percentage in either of these sports actually wore a mouthguard (10 and 0%, respectively). Trauma incidence between direct contact with rival competitors and indirect contact with rival competitors was not significantly different. The incidence of dental trauma in contact sports shows that the awareness and use of mouthguards must be intensified. Mouthguard use should be made compulsory, especially in those sports with high risk for dental trauma.
Veterinary Drug Usage and Antimicrobial Resistance in Bacteria of Animal Origin
Authors: Aarestrup Frank M.
Published: March 2005

Abstract: In the production of food animals, large amounts of antimicrobial agents are used for therapy and prophylaxis of bacterial infections and in feed to promote growth. There are large variations in the amounts of antimicrobial agents used to produce the same amount of meat among the different European countries, which leaves room for considerable reductions in some countries. The emergence of resistant bacteria and resistance genes due to the use of antimicrobial agents are well documented. In Denmark it has been possible to reduce the usage of antimicrobial agents for food animals significantly and in general decreases in resistance have followed. Guidelines for prudent use of antimicrobial agents may help to slow down the selection for resistance and should be based on knowledge regarding the normal susceptibility patterns of the causative agents and take into account the potential problems for human health. Current knowledge regarding the occurrence of antimicrobial resistance in food animals, the quantitative impact of the use of different antimicrobial agents on selection of resistance and the most appropriate treatment regimes to limit the development of resistance is incomplete. Programmes monitoring the occurrence and development of resistance and consumption of antimicrobial agents are strongly desirable, as is research into the most appropriate ways to use antimicrobial agents in veterinary medicine.
2,3‐Dimercapto‐1‐propanol does Not Alter the Porphobilinogen Synthase Inhibition but Decreases the Mercury Content in Liver and Kidney of Suckling Rats Exposed to HgCl2
Authors: Roza Taciane , Peixoto Nilce Coelho , Welter Aurea , Flores Erico Marlon Moraes , Pereira Maria Ester
Published: March 2005

Abstract: Heavy metals have received great attention as environmental pollutants mainly because once introduced in the biological cycle they are incorporated in the food chain. Especially the mercury toxicity due to a diversity of effects caused by different chemical species should be emphasized. Heavy metal intoxication has been treated with chelating agents such as 2,3‐dimercapto‐1‐propanol (BAL). However, the efficacy of this treatment is questionable due to the lack of specific effect on the toxic metal. The present study examined the effects of HgCl2 exposure (five doses of 5.0 mg/kg between ages 8 to 12 days) on physiological parameters, on porphobilinogen synthase activity, and on mercury content in liver, kidneys and brain from suckling rats. The effect of BAL (one dose of 12.5–75 mg/kg) applied 24 hr after mercury intoxication on these parameters was also investigated. The results demonstrate that HgCl2 intoxication induced a decrease of corporal weight gain as well as brain weight and an increase in renal weight. The inhibition of porphobilinogen synthase from liver and kidney, is still significant and was not modified by subsequent BAL treatment. However, BAL altered two effects induced by mercury: increase in death percentage and decrease in mercury contents in liver and kidney. The increase of mortality induced by mercury was not promoted by metal redistribution to brain nor by the increase of porphobilinogen synthase inhibition induced by metal. More investigations are necessary to determine if the different effects of BAL on intoxication by metals are possibly related to other tissues and/or if the probable metal‐chelating complex formed is more toxic than the metal itself.
TASTE COMPONENTS OF CHEDDAR CHEESE: FRACTIONATION AND OPTIMIZATION OF CHEDDAR CHEESE TASTE IN WATER
Authors: YANG BIN , VICKERS ZATA
Published: March 2005

To determine the taste components of Cheddar cheese, we fractionated one mild Cheddar cheese and one aged Cheddar cheese by water extraction, freeze‐drying and gel filtration. Salty, sour and umami were the three predominant tastes present in the fractions. Neither trigeminal sensations nor astringency was perceived. We used response surface methodology to reconstruct a mild Cheddar cheese taste and an aged Cheddar cheese taste in water. Less salt and less acid were needed to simulate the taste of mild Cheddar cheese, compared with aged Cheddar cheese. Our optimized water solutions (containing sodium chloride, lactic acid and monosodium glutamate) were as similar to the real cheese samples as were the water extracts of the standard cheeses. However, neither our optimized solutions nor the water extracts matched the taste of the actual cheeses.
Influence of Cervical Disc Degeneration after Posterior Surgical Techniques in Combined Flexion-Extension—A Nonlinear Analytical Study
Authors: Ng Hong-Wan , Teo Ee-Chon , Zhang Qinghang
Published: March 2005

Laminectomy and facetectomy are surgical techniques used for decompression of the cervical spinal stenosis. Recent in vitro and finite element studies have shown significant cervical spinal instability after performing these surgical techniques. However, the influence of degenerated cervical disk on the biomechanical responses of the cervical spine after these surgical techniques remains unknown. Therefore, a three-dimensional nonlinear finite element model of the human cervical spine (C2–C7) was created. Two types of disk degeneration grades were simulated. For each grade of disk degeneration, the intact as well as the two surgically altered models simulating C5 laminectomy with or without C5–C6 total facetectomies were exercised under flexion and extension. Intersegmental rotational motions, internal disk annulus, cancellous and cortical bone stresses were obtained and compared to the normal intact model. Results showed that the cervical rotational motion decreases with progressive disk degeneration. Decreases in the rotational motion due to disk degeneration were accompanied by higher cancellous and cortical bone stress. The surgically altered model showed significant increases in the rotational motions after laminectomies and facetectomies when compared to the intact model. However, the percentage increases in the rotational motions after various surgical techniques were reduced with progressive disk degeneration.
Simulating Dynamic Activities Using a Five-Axis Knee Simulator
Authors: Maletsky Lorin P. , Hillberry Ben M.
Published: March 2005

This work describes the design and capabilities of the Purdue Knee Simulator: Mark II and a sagittal-plane model of the machine. This five-axis simulator was designed and constructed to simulate dynamic loading activities on either cadaveric knee specimens or total knee prostheses mounted on fixtures. The purpose of the machine was to provide a consistent, realistic loading of the knee joint, allowing the kinematics and specific loading of the structures of the knee to be determined based on condition, articular geometry, and simulated activity. The sagittal-plane model of the knee simulator was developed both to predict the loading at the knee from arbitrary inputs and to generate the necessary inputs required to duplicate specified joint loading. Measured tibio-femoral compressive force and quadriceps tension were shown to be in good agreement with the predicted loads from the model. A controlled moment about the ankle-flexion axis was also shown to change the loading on the quadriceps.
A survey of high-school physics teachers in New Jersey
Authors: Lindenfeld Peter
Published: March 2005

This paper presents the results of a survey of high-school physics teachers in New Jersey, with some comments.
Electronic speech synthesis with microcomputer control
Authors: Fegan D. J. , Grimley H. M.
Published: March 2005

An undergraduate physics laboratory project is described which utilizes a dedicated speech processor microchip and a series of read-only memories to produce a limited vocabulary of high quality spoken English under the interactive control of a Commodore 64 microcomputer for use in courses in acoustics. The project affords a cheap and simple introduction to electronic speech synthesis and also offers experience in microcomputer interfacing and control.
Velocity dependence of friction on an air track
Authors: Keig William E.
Published: March 2005

An experiment to measure the velocity dependence of friction on an air track using a photogate timer is described. This experiment is suitable as a laboratory exercise or a demonstration experiment in an upper division level course in mechanics.
A lecture demonstration of the incompatibility of quantum predictions with those of a local realistic theory
Authors: Stedman G. E.
Published: March 2005

A logic circuit is used to light bulbs in accordance with quantum predictions and in violation of the predictions of a local realistic theory. This makes Mermin’s gedanken experiment, in which the Einstein–Podolsky–Rosen paradox (as sharpened by Bell) is presented with the minimum of technicalities, a feasible and instructive lecture demonstration. We give circuit details, a useful order of presentation, the reactions of a class of nonscience majors, and a simple general proof of the incompatibility.