bluuebunny/crossref_metadata_2025 huggingface dataset:
New Guidelines for Preparation Taper
Authors: Parker Merle H. , Calverley Mickey J. , Gardner Michael , Gunderson Ronald B.
Published: March 2005

The purpose of this article is to provide new guidelines for minimally acceptable preparation taper by developing a theoretical mathematical foundation based on principles of resistance form. Yes and no are the possible answers to the question, “Does a preparation have resistance form?” This dual nature is useful because in graphing resistance form as a function of taper, potential tapers on the x axis are divided into two groups with an exact dividing point. Tapers less than this dividing point provide resistance form; tapers larger or equal do not provide resistance form. This dividing point makes a reasonable standard for minimally acceptable taper. Average tapers are defined as the limiting average taper and are mathematically determined to equal 1/2 arcsin (H/B), where H is the height of the preparation and B is the base. From this equation, the taper required to provide resistance form for an individual preparation can be calculated by using the preparation's height to base ratio. The equation can also be used to provide guidelines by tooth group. Dies of a prosthodontist were saved and sorted by group (incisors, canines, premolars, and molars). Measurements of 30 dies from each of these groups were used to calculate the average (H/B) ratios and standard deviations. Calculating the limiting average taper by using the average height‐to‐base ratio minus two standard deviations provides the dividing point taper that is acceptable for over 97% of the preparations. The values calculated are: 29° for incisors, 33° for canines, 10° for premolars, and 8.4° for molars. These values are recommended as guidelines for minimally acceptable taper. They are not ideals for which to strive, but the boundary of unacceptable tapers to avoid. Evaluating reported clinical average tapers based on these guidelines shows that anterior preparations easily exceed the standard, and premolars are acceptable, whereas the average taper reported for molars is unacceptable.
Dentinal Exposure Resulting From Ball Rest Seat Preparations on Mandibular Canines
Authors: Haisch Larry D. , Hansen Carl A.
Published: March 2005

Twenty extracted mandibular canine teeth were prepared with lingual ball rest seats. The preparations were placed in the area with the greatest horizontal component. The depth of tooth penetration was determined by the establishment of a positive seat. In all specimens, the enamel was penetrated and the dentin exposed. The authors note that, when ball rests are placed in mandibular canines, one should assume dentin exposure. The authors also recommend that suitable restorations be placed on a routine basis.
The Potential for Bonding Titanium Restorations
Authors: Lorey Robert E. , Edge Marion J. , Lang Brien R. , Lorey Hilary S.
Published: March 2005

Purpose The use of titanium for implants has shown the biological acceptance of the metal. Recently, methods of using titanium for restorations, crowns, and bridges have been introduced using both cast and spark erosion systems for fabrication. A potential also exists for using titanium for bonded (Maryland) bridges.

Materials and Methods In this study, the potential for bonding titanium was investigated by cementing with various adhesives: (A) metal to metal, (B) metal to enamel, and (C) comparing with a known procedure of bonding nickel‐chromium. Truncated cones of pure titanium were fabricated with a 5‐mm circular face for bonding to a larger titanium disc embedded in a plastic ring. A special jig was used to pull the bonded cone from the disc on an Instron tensile testing machine (Instron Corporation, Canton, MA). The resin‐metal adhesives used were: (1) Infinity, (2) Metabond, (3) All‐Bond 2, and (4) Panavia. These were compared with (5) nickel‐chromium cones sandblasted and bonded to nickel‐chromium with Panavia. Titanium cones were also bonded to human enamel with (6) Panavia and (7) Metabond. The 10 samples in each group were subjected to tensile force, and point of fracture was recorded. The data were subjected to an analysis of variance with a Scheffe F test at the 95% level of significance.

Results The results of tensile forces in MPa were (1) Infinity, 28.1 ± 3.6; (2) Metabond, 28.1 ± 1; (3) All‐Bond 2, 49.5 ± 4.3; (4) Panavia, 57.9 ± 3.1; (5) Panavia to nickel‐chromium, 42.9 ± 6.6; (6) Panavia to enamel, 18.5 ± 4.7; and (7) Metabond to enamel, 19.3 ± 3.5. Titanium was most effectively bonded with All‐Bond 2 and Panavia, with Panavia samples significantly better than Panavia to nickel‐chromium samples.

Conclusions It was concluded that titanium bonded restorations with certain adhesive cements were a definite possibility.
Determination of the Existence of Hinge Movements of the Temporomandibular Joint During Normal Opening by Cine‐MRI and Computer Digital Addition
Authors: Yustin Daniel C. , Rieger M.R. , McGuckin R.S. , Connelly M.E.
Published: March 2005

Purpose The purpose of the first phase of this two‐part investigation was to determine if the opening motion of the mandible could be illustrated and described using a dynamic imaging method. The purpose of the second phase of the investigation was to determine if a center of rotation would be discovered.

Materials and Methods Five volunteer subjects, 2 female and 3 male, whose temporomandibular joints had previously been determined to be asymptomatic, were examined by magnetic resonance imaging (MRI) during opening from a standardized position. The serial static images were reconstructed by the MRI's computer in “cine mode'’to simulate dynamic motion, similar to a motion picture. For the second phase, each patient's series of static images were digitally added and manipulated by a computer graphics program to locate the center of hinge motion.

Results After reviewing the animated images recorded on videotape, three independent dentist observers confirmed that the opening movement of the mandible was initially rotational, followed by translation within the glenoid fossa. A center of rotation was calculated to be in the anatomic center of the condylar head of all of the subjects in this study.

Conclusions This study showed that opening dynamics of the mandibular condyle could be studied by cine‐MRI and that an opening hinge axis appears to be located in the anatomic center of the condylar head.
Adapting a Dental Surveyor to Function in Two Planes
Authors: Johnson Dean L.
Published: March 2005

Many bilateral distal extension removable partial dentures possess insufficient guidance to control their dislodgement. When such a situation is observed, the tips of retentive clasps must be located in both an occlusogingival and mesiodistal (away from the denture base area) undercut. The specific location can be identified with a dental surveyor that has been adapted to function in two planes. Details of the adaptation process and use of the surveyor are described.
Verifying the Reliability of Interchanging Casts Between Hanau Modular Articulators
Authors: Sanchez Robert A. , Moore Dorsey J. , Cowan Robert D. , Spencer Paulette
Published: March 2005

Purpose The purpose of this study was to test the Hanau Modular Articulator system with programmed fossae to determine its interchangeability.

Materials and Methods Eight Hanau Modular Articulators were tested using the same measuring system as previously developed in a similar investigation on a different instrument.

Results It was determined that the Hanau Modular System with programmed fossae did possess accuracy when a measuring device was transferred between the eight articulators tested.

Conclusions Laboratory procedures for multiple restorations can be accomplished with accuracy when master casts and mountings are transferred between Hanau Modular Articulators.
The Effect of Tooth Preparation on Retention and Microleakage of Cemented Cast Posts
Authors: Lund Peter S. , Wilcox Lisa R.
Published: March 2005

Purpose

Vibration from the high‐speed handpiece may adversely affect the cement layer between a casting and a tooth, causing loss of retention or increased microleakage. This study assessed the effect of crown preparation on retention and microleakage of cemented cast post and cores.

Materials and Methods

Post and cores were fabricated for extracted teeth and cemented. Specimens were prepared for crown restorations, varying the preparation time and the rotary diamond instrument used. After thermocycling and immersion in a dye bath, tensile unseating force and linear dye penetration were measured.

Results

In general, retention decreased with increased severity of crown preparation; however, differences were not statistically significant (α= .05). Although the differing preparation conditions resulted in significant differences in microleakage, no consistent trends were evident.

Conclusions

Crown preparation using high‐speed rotary diamond abrasives of cast post and cores luted with zinc phosphate cement had no significant effect on their retention, but had varying effects on subsequent microleakage at the cement‐tooth interface.
Computer‐Generated Slide Technology
Authors: Palmer David S.
Published: March 2005

Presentation technology is available, and it does not have to be expensive. This article describes computer hardware and software concepts for graphics use, and recommends principles for making cost‐effective buying decisions. Also included is a previously published technique for making custom computer graphic 35‐mm slides at minimal expense. This information is vital to anyone lecturing without the support of a custom graphics laboratory.
Use of Tissue‐Tinted Porcelain to Restore Soft‐Tissue Defects
Authors: Duncan J. David , Swift Edward J.
Published: March 2005

Anterior, partially edentulous residual ridges often have hard‐tissue and soft‐tissue defects that create esthetic and functional problems when conventional fixed prostheses are used to replace the missing teeth. However, tissue‐tinted porcelain can be used in conjunction with fixed prostheses to solve many of these problems. Proper prosthesis design and shade matching are important considerations in the fabrication of fixed prostheses that incorporate tissue‐tinted porcelain to restore hard‐tissue and soft‐tissue defects.
Surface Cracking Identified in Polished and Self‐Glazed Dental Porcelain
Authors: Edge Marion J. , Wagner Warren C.
Published: March 2005

Purpose

Polishing and glazing porcelain surfaces of restorations is thought to help reduce the wear on the opposing occlusion because of reduced roughness.

Materials and Methods

To test this theory, samples of a variety of dental porcelains were prepared and subjected to various polishing and self‐glazing treatments commonly used in dentistry and then viewed using scanning electron microscope (SEM). Fine cracks were discovered in the surface of the samples that had been polished and then self‐glazed. These cracks were typically greater than 50 μm in length with submicron surface openings and crack depths less than 20 μm. To establish the treatments responsible for the formation of these cracks, a more controlled study was performed. Samples of Vita VMK 68 no. 559 incisal porcelain (Vita Zahnfabrik, Bad Såchingen, Germany) were prepared and subjected to six treatments (sample size = 3): treatment no. 1, as‐fired condition; treatment no. 2, self‐glazed (32°C per minute to 960°C, then cooled); treatments no. 3 and 4, wet ground followed by 1 μm diamond polish (no. 4 was then self‐glazed); treatments no. 5 and 6, ground and polished using a Shofu porcelain adjustment kit (Shofu Inc, Kyoto, Japan) (no. 6 was then self‐glazed). The samples were observed using SEM.

Results

Treatments no. 1, 2, 3, and 5 showed no cracking; however, treatments no. 4 and 6 showed cracking in all specimens (approximate levels 5,100 μm/mm2 and 3,600 μm/mm2, respectively).

Conclusions

Polishing followed by self‐glazing produces fine surface cracks. The rougher surface resulting from the surface cracks and subsequent porcelain chipping may cause wear of opposing occlusal surfaces.
An Investigation of the Rhelogical Properties of Several Interocclusal Registration Materials
Authors: Chai John , Leong Dennis K. , Pang Iok‐Chao
Published: March 2005

Purpose

To study the viscosities of eight interocclusal registration materials at 30 seconds after the start of mixing and to compare the time (Tcv) required for various interocclusal registration materials to reach a proposed critical viscosity of 5,000 poise.

Materials and Methods

One zinc‐oxide eugenol, one polyether, and six vinyl‐polysiloxane interocclusal registration materials were studied. The viscosities of the polymerizing materials were monitored with a cone and plate viscometer.

Results

One‐way analysis of variance showed significant difference in the viscosity at 30 seconds and in the Tcv among the materials. A zinc oxide eugenol interocclusal registration material was found to possess the lowest viscosity at 30 seconds and the longest Tcv.

Conclusions

The criteria for the selection of an interocclusal registration material should include its viscous properties because all materials behaved differently.
A Comparison of Impression Techniques for the CeraOne Abutment
Authors: Schmitt James K. , Adrian Eric D. , Gardner F. Michael , Gaston Max L.
Published: March 2005

Purpose

This study measured the accuracy of two impression techniques recommended by Noblepharma to be used with their CeraOne single tooth implant restoration. The first technique was to lute the impression transfer coping to the impression tray with autopolymerizing acrylic resin. The second was to leave the transfer coping free‐standing in the impression material.

Materials and Methods

Thirty‐five samples were made of a polyvinyl impression of the CeraOne transfer coping free‐standing in the set impression material. Thirty‐five samples were made of a polyvinyl impression of the CeraOne transfer coping luted to the impression tray with autopolymerizing acrylic resin. A jig was fabricated and used to record the spatial relations of the impressions and the transfer copings in reference to the jig. A light microscope was used to measure the distance between fixed markings on pressure sensitive paper, representing impression variations.

Results

The mean discrepancy in the horizontal plane for nonluted impressions was 0.094 mm, and for luted impressions, it was 0.275 mm. The mean discrepancy in the vertical plane for nonluted impressions was 0.154 mm, and for luted impressions, it was 0.192 mm. The differences found between the group with the luted impression tray and the group with the nonluted impression tray were found to be statistically significant.

Conclusions

The more accurate of the two techniques is to transfer the impression coping without luting it to the impression tray.
A Survey of Private Prosthodontic Practice
Authors: Dickey Keith W.
Published: March 2005

This article reports the data of a survey of private prosthodontic practitioners. It reports incomes, overhead expenses, staff size, and character of prosthodontic practices. The study also develops a profile for a median prosthodontic practice and practitioner.
Bonding of Composite Resin to Contaminated Human Enamel and Dentin
Authors: Powers John M. , Finger Werner J. , Xie Jianxiu
Published: March 2005

Purpose The purpose of this in vitro study was to evaluate the bond strengths of a bonding agent and composite resin system to human enamel and dentin treated with five contaminants (saliva, plasma, zinc oxide–eugenol cement, noneugenol zinc oxide cement, and handpiece lubricant) using air, moisture, and water as controls.

Materials and Methods A commercial bonding agent (Gluma 2000; Bayer AG, Dormagen, Germany) and its composite (Pekafill; Bayer AG) were applied to tooth structure under two conditions (contaminated and re‐etched). Samples were debonded in tension after 24 hours using an inverted, truncated cone bond test.

Results Among the controls, the highest bond strengths were obtained to enamel (20 MPa) and dentin (12 MPa) with air drying. Contaminants lowered the bond strength by 20% to 100%. Re‐etching without additional mechanical preparation resulted in bond strengths similar to the air control.

Conclusions Bond strength of Gluma 2000/Pekafill to tooth structure is sensitive to common forms of contamination but can be improved by re‐etching after contamination occurs.
Evaluation of a New Silicone Elastomer for Maxillofacial Prostheses
Authors: Polyzois Gregory L.
Published: March 2005

Purpose Although numerous advances in maxillofacial materials have been made in the past several years, the need for improvement continues. Currently, the most widely used materials are the silicones, especially the room temperature‐vulcanizing type. This study compared the physical properties of a new silicone material Cosmesil K10 (Cosmedica Ltd, Cardiff, United Kingdom) with those of MDX4‐4210 (Dow Corning Corporation, Midland, Ml), a popular material for maxillofacial prostheses.

Materials and Methods The properties that were investigated were tensile strength, modulus at 100% elongation, percentage of elongation, tear strength, and hardness. The properties tested were selected because of their clinical significance for fabricating maxillofacial prostheses. Tensile strength and elongation were measured with a Monsanto Tensometer (Monsanto Ltd, Swindon, England) and dumbbell‐shaped specimens according to the International Organization for Standardization (ISO) specification no. 37. The tear test was performed on the Monsanto machine with unnicked 9° angle–shaped specimen following the ISO specification no. 34. The type A Shore durometer was used to measure hardness on specimens 25 × 25 × 10 mm according to the American Society for Testing Materials specification no. D2240.

Results The results showed that MDX4‐4210 had a greater tensile strength and modulus (P= .0002; P= .0015). No significant difference (P= .1986) was found for the percentage of elongation between MDX4‐4210 and Cosmesil K10. Cosmesil K10 had a greater tear strength and was slightly harder (P= .0022; P= .0421) than MDX4‐4210.

Conclusions Cosmesil K10 showed physical properties similar to those of MDX4‐4210. An improvement in the predictability of the mechanical behavior of Cosmesil K10 would further enhance the value of the material.
Comparison of Strains Transferred to a Bone Simulant Among Implant Overdenture Bars with Various Levels of Misfit
Authors: Clelland Nancy L. , Papazoglou Efstratios , Carr Alan B. , Gilat Amos
Published: March 2005

Purpose To measure and compare strains transferred to a bone simulant by screw‐fastening implant overdenture bars with various levels of fit or misfit.

Materials and Methods Photoelastic resin was cast directly to two 3.75 × 13‐mm Branemark fixtures (Nobelpharma USA Inc, Chicago, IL) situated 20 mm apart in a silicone mold of an edentulous mandible. Two strain‐gauge rosettes were also incorporated in the resin to allow precise determination of principal stresses at two locations. Four groups of three overdenture bars with 0‐, 180‐, 360‐, and 500‐μm vertical gaps were fabricated. These bars were sequentially secured to the abutments with gold slot screws tightened to 10 N · cm. Strain indicator readings were recorded at a standardized time following the initial fastening of each bar. The test was repeated three times for each overdenture bar.

Results Mean principal stresses and strains at the location of the rosettes were determined. The magnitude of these stresses and strains increased significantly with each increase in gap size. Strains were several times larger mesial to the fixture than they were distal.

Conclusions Strains are transferred to the bone when misfitting prostheses were secured. Some of the strains mesial to the fixture appeared to be unfavorable for regions of lower bone density when the groups with designed gaps were secured. These data will be compared with those in ongoing animal studies regarding the cellular response to prosthesis misfit.
Book Reviews
Authors: Kaugars George
Published: March 2005

Current Oral and Maxillofacial Imaging

Thomas F. Razmus, DDS, MS, and Gail F. Williamson, RDH, MS. W. B. Saunders Company, Philadelphia, Pennsylvania, 1996. ISBN 0‐7216‐4805‐2. (279 pages, with numerous radiographic images, price $35.00)
Allergic Reaction Following Insertion of a Pd‐Cu‐Au Fixed Partial Denture: A Clinical Report
Authors: Hansen Paul A. , West Lesley A.
Published: March 2005

A severe allergic reaction to a porcelain‐fused‐to‐metal fixed partial denture containing 79% palladium, 2% gold, and 19% copper, resulting in a variety of symptoms and hospitalization of the patient, is reported. The reaction occurred 4 hours after cementation of the fixed partial denture. Suggestions for use of nongold metal alloys are discussed.
The Effect of the Use of Dental Gloves on Mixing Vinyl Polysiloxane Putties
Authors: Matis Bruce A. , Valadez Domingo , Valadez Elena
Published: March 2005

Purpose The purpose of this study was to determine the delay in setting times that occurs with selected brands of gloves or residual powder from those gloves on eight popular brands of vinyl polysiloxane putties.

Materials and Methods The putties were mixed and rolled into a round 3‐inch‐long cylinder without gloves on hand, with gloves on hand, and with powder residue on hands, immediately after degloving. The end of a cement spatula was drawn over the putty at various intervals with a force of 3 ounces. The setting time was recorded to be when no permanent indentation of the putty occurred.

Results All materials set within 5 minutes without gloved hands. Eighty‐eight percent of the putties set within 5 minutes when mixed with Friction Grip Powder Free and Medical Gloves on hands. When mixed with Pharmaseal gloves on hands, 50% of the putties set in 5 minutes. When mixed with Micro‐Touch Latex Medical Gloves, 38% of the putties set in 5 minutes. When the putties were mixed with the residual powders left on ungloved hands, the same results occurred with the above‐mentioned gloves. With residual powder on hands from Natraflex and Medical Exam Tex, 25% of the putties set in 5 minutes.

Conclusions Gloved hands interfered with the setting of more brands of putties than did residual powder on hands immediately after degloving. There are gloves available that do not interfere with the setting of most of the vinyl polysiloxane putties.
Retention of Cemented Implant‐Supported Restorations
Authors: Kent Dennis K. , Koka Sreenivas , Froeschle Mary Lynn
Published: March 2005

Purpose This investigation compared cement failure loads of a gold cylinder luted to a CeraOne titanium abutment (5‐mm‐high chimney) 24 hours postcementation when either zinc phosphate, Tempbond NE, or Tempbond luting agent was used.

Materials and Methods Luting agent (0.01 mL) was applied to the internal aspect of the gold cylinder, and the cylinder was seated with finger pressure followed by a load of 5 kg for 10 minutes. The specimens were stored in 100% humidity at 37°C for 24 hours before a uniaxial tensile force was applied to the gold cylinder by a mechanical testing instrument. A load‐displacement chart was plotted and the cement failure load (CFL) calculated in kilograms. CFLs were determined for each luting agent with the access opening for the CeraOne gold screw on the internal of the abutment either unfilled or filled with autopolymerizing resin.

Results A two‐way ANOVA and Tukey's HSD revealed that zinc phosphate resulted in significantly higher (p < .05) mean CFLs than Tempbond or Tempbond NE. In general, filling the access opening did not affect mean CFLs for zinc phosphate and Tempbond NE. However, mean CFLs for gold cylinders cemented with Tempbond and a filled access opening were significantly higher than mean CFLs with an unfilled access opening. However, neither the filled nor the unfilled Tempbond group mean CFL was significantly different from either Tempbond NE mean CFL.

Conclusions Twenty‐four hours postcementation, zinc phosphate luting cement significantly enhanced CFLs of a CeraOne gold cylinder luted to a 5‐mm CeraOne titanium abutment compared with Tempbond and Tempbond NE. Filling the gold screw access opening of the abutment with autopolymerizing resin only led to higher mean CFLs when Tempbond was used as the luting agent. Filling the access opening had no effect (p > .05) on mean CFLs when Tempbond NE or zinc phosphate was used.
The Dental Student as Technician: An 18‐Year Follow‐Up of Clinical Laboratory Programs
Authors: Weintraub Gerald S. , Weintraub Annette M.
Published: March 2005

In 1977, a survey of American and Canadian dental schools was conducted by Weintraub to determine the delegation of laboratory procedures in preclinical and clinical complete and removable partial denture programs. This was performed in light of challenges raised to the value of requiring dental students, rather than laboratory technicians, to perform the various laboratory procedures involved in the fabrication of complete and removable partial dentures. Since 1977, the rate of edentulism has declined in the United States, and fewer edentulous patients have sought regular dental care. In addition, approximately 20% fewer curriculum hours have been spent in dental schools in removable prosthodontic instruction; a declining number of graduating dental students have felt comfortable with their level of knowledge of removable prosthodontics, especially complete dentures, and have performed fewer removable prosthodontic procedures in practice because of a perceived lack of treatment cost‐effectiveness. The present study, an 18‐year follow‐up to the 1977 survey, was designed to determine if such trends toward a deemphasis on removable prosthodontic treatment have affected the mechanisms of instruction in and the extent to which dental schools instruct students about removable‐prosthodontics laboratory procedures. The 1995 survey was mailed to 53 American dental schools. Forty‐six schools returned the completed survey, for a response rate of 87%. Results showed that the relative amount of material presented to students in clinical removable prosthodontics programs increased, primarily through the enhancement of laboratory technician support, both in‐house and commercial, of student clinical removable prosthodontic laboratory procedures. The increase was greater than in preclinical removable prosthodontic programs, which were described in a companion article. The conflict between these outcomes and the call by the dental community, as well as that of the 1995 Institute of Medicine Study, for a reduced emphasis on teaching students about the technical details involved in removable prosthesis fabrication is recognized and explored.
A Technique for Improved Maxillary Record Base Adaptation Through Controlled Polymerization of Light‐Activated Dental Resins
Authors: Hopkins Derek S. , Phoenix Rodney D. , Abrahamsen Thomas C.
Published: March 2005

A technique for the fabrication of light‐activated maxillary record bases is described. The use of a segmental polymerization process provides improved palatal adaptation by minimizing the effects of polymerization shrinkage. Utilization of this technique results in record bases that are well adapted to the corresponding master casts.
Prosthodontic Rehabilitation Using Surgical Space Modification
Authors: NaBadalung Darunee P.
Published: March 2005

Treatment using a LeFort I osteotomy and sequential prosthodontic rehabilitation is presented. This treatment combination is a viable alternative therapy for the severe extrusion of posterior maxillary dento‐osseous segments.
Erosion Caused By Gastroesophageal Reflux: Diagnostic Considerations
Authors: Gregory‐Head Belinda , Curtis Donald A.
Published: March 2005

Dental erosion occurs with a high prevalence in the general population, but its impact on prosthodontic care is often unrecognized. The etiology of dental erosion is difficult to establish because it may result from a variety of causes and may have different presentations. Our purpose was to review the literature relevant to dental erosion and to report a patient presentation in which an unusual pattern of severe erosion was the dental manifestation of asymptomatic gastroesophageal reflux disease.
Effectiveness of Adhesive Systems for a Co–Cr Removable Partial Denture Alloy
Authors: NaBadalung Darunee P. , Powers John M.
Published: March 2005

Purpose In vitro bond strengths of traditional denture base acrylic resin (Lucitone 199) to a cobalt‐chromium partial denture alloy (J.D. Partial Denture Alloy) were tested using two surface pretreatments (sandblast, sandblast and electrochemical etch) with three adhesive primers: Lee Metal Primer, Acrylic Solder, and CR Inlay cement. A sandblasted group with no primer served as the control.

Materials and Methods The alloy specimens (8.0‐mm bonding diameter) were cast and invested to receive a traditional denture base resin after surface treatments (sandblasted, and sandblasted‐electrochemically etched) and application of adhesive primers. The bonded specimens were stored in distilled water at 37°C for 24 hours and divided into two groups. The first group was debonded in tension on a testing machine at a cross‐head speed of 0.05 cm/min. The second group was subjected to thermocycling of 1,000 cycles and then tested for tensile bond strength. The force at which the bond failed was recorded, and the bond strength was calculated in megapascals (MPa). The sites of bond failure were examined, quantified under (20x) magnification, and recorded. Ten specimens were evaluated for each experimental condition for a total of 160 specimens. Data were analyzed by ANOVA with a factorial design. Means were compared by Tukey intervals at the 0.05 significance level.

Results Significant differences in bond strength were observed, with primers being the most important factor, followed by pretreatment and storage and thermocycling with significant interactions. Sandblasted‐electrochemically etched alloy with primers more effectively enhanced bond strength of the denture base resin to the treated alloy than sandblasted alloy with primers. Thermocycling had a greater effect on bond strength of the specimens with Acrylic Solder when compared with Lee and CR Inlay primers. The highest bond strengths (>18.0 MPa) were observed for the conditions involving electrochemical etching and the priming with CR Inlay cement (both after 24 hours and thermocycling of 1,000 cycles). For primed specimens, the bond failures occurred cohesively within the primers or the denture resin and adhesively between the primers and the denture base resin, or between primers and alloy. For nonprimed, the bond failures occurred adhesively at the denture base resin‐metal interface.

Conclusions Nonprimed specimens (both sandblasted and electrochemically etched) had lowest bond strength (0.4 ± 0.1 MPa; 0.3 ± 0.4 MPa). The bond strengths of the primed treated specimens were improved significantly. The CR Inlay‐treated specimens exhibited the highest bond strength (20.6 ± 6.3 MPa). After thermocycling for 1,000 cycles, the bond strengths of the specimens were significantly lower than the bond strengths of the specimens after 24 hours.
A Review of Preweighed, Packaged Die Stone Versus Bulk Die Stone Use in a Dental School
Authors: Price Richard B. T. , Doyle M. Gorman , Bannerman Ronald A.
Published: March 2005

Purpose This study compared the quantity of preweighed, packaged die stone use to bulk die stone use by dental students.

Materials and Methods Starting in September 1994, all the bulk die stone was removed from the dental clinic, and only preweighed packages of die stone (Silky‐Rock, Whip Mix) were available to students. At the end of August 1995 and August 1997, the amount of preweighed die stone used by the students was determined and compared with the amount of bulk die stone (DieKeen, Modern Materials) used during the period of September 1993 to August 1994.

Results Between September 1994 and August 1997, the students used 42% less per annum of the preweighed, packaged die stone than the previous annual use of bulk die stone. The laboratories were much cleaner when the preweighed packages were used, and fewer cleaning staff were required. The environment was also cleaner for the laboratory staff, who used to fill the bulk containers with gypsum products.

Conclusions Students used 42% less die stone per annum when using the preweighed packages.
Restoring the Edentulous Maxilla Using an Implant‐Supported, Matrix‐Assisted Secondary Casting
Authors: Finley Jon M.
Published: March 2005

The selection of appropriate implant treatment modalities for the edentulous maxillary arch is complex. Although many patients are candidates for an implant‐supported removable prosthesis, two major considerations affecting choice of treatment type are the amount of residual alveolar bone and soft tissue, and cost. A technique is described that employs a cast milled primary bar and a secondary casting constructed using a vacuum‐formed 0.040‐in plastic matrix. The secondary casting is intimately adapted to the primary bar and incorporates the retentive elements within it. The resulting prosthesis is less expensive than comparable designs, and retentive elements are easily replaceable. The technique is adaptable to most implant systems. The matrix‐assisted secondary casting technique provides a design that is esthetic and hygienic. The prosthesis may also be easier to insert and remove than implant‐supported removable prostheses that use plunger‐ or latch‐type retention.
Impression Technique for Arches Requiring Both Implant and Natural Tooth Restorations
Authors: Chee Winston W. L. , Alexander Marc L.
Published: March 2005

Implant impression copings reduce access to prepared teeth during the impression‐making process. If the impression copings and teeth are in close proximity, it may be difficult to extrude impression material circumferentially around the margins of the tooth preparations. A technique is described that allows the impressions of the prepared teeth to be made without the implant impression copings interfering. The advantages and disadvantages of the technique are discussed.
Marginal Adaptation of Implant‐Supported Metal‐Ceramic Crowns Fabricated With Gold Cylinders
Authors: Sutherland J. Kenneth , Ritsco Ronald G. , Budd Scott R.
Published: March 2005

Purpose The purpose of this investigation was to determine the mean marginal discrepancy of metal‐ceramic crowns fabricated with gold cylinders and cemented on implant abutments. These discrepancies were then compared with those measured previously for implant‐supported ceramic crowns.

Materials and Methods Fifteen Nobel BioCare CeraOne abutments were connected to implant fixtures embedded in acrylic resin blocks. Marginal discrepancies were determined for gold cylinders, gold cylinders plus ceramic alloy (metal frameworks), completed metal‐ceramic crowns, and cemented metal‐ceramic crowns using a stereomicroscope equipped with a video camera linked to a computer. A Hotelling's T2 test (p .05) was used to evaluate potential differences in mean marginal discrepancies among groups.

Results The mean marginal discrepancies were: 1) gold cylinders, 7.56 ± 2.73 μm; 2) metal frameworks, 6.21 ± 1.34 μm; 3) metal‐ceramic crowns, 11.06 ± 3.21 μm; and 4) zinc‐phosphate cemented crowns, 31.47 ± 6.65 μm. No significant difference between gold cylinders and metal frameworks was found. Mean marginal discrepancies for metal‐ceramic crowns were significantly greater than discrepancies for cast gold cylinders. Cemented‐crown mean marginal discrepancy was significantly greater than all other means.

Conclusions Cemented metal‐ceramic crowns fabricated using proprietary gold cylinders exhibited well‐fitting margins (31.47 μm).
Tear Strength of Four Irreversible Hydrocolloid Impression Materials
Authors: Cohen Brett I. , Pagnillo Mark K. , Lee Musikant Barry , Deutsch Allan S.
Published: March 2005

Purpose The purpose of this investigation was to examine the tear strength of four irreversible hydrocolloid (alginate) impression materials (Tare‐Free Alg, Jeltrate, Identic, and Kromopan).

Materials and Methods Eighty specimens, 20 for each alginate tested, were according to the manufacturers' instructions. A cutting die described in American Standard Test and Material document D‐1004‐94a was used to prepare test specimens. Immediately after removal from the cutting die, test specimens were measured at five points with an electronic caliper. Test specimens were placed into a specialized jig, and a Shimpo force gauge was used to measure tear strength. The tear test was performed no more than 10 minutes after mixing the alginate material with water. The tear strength was then calculated. One‐way ANOVA was used to compare the mean force required to induce tearing for each of the four groups, followed by the Newman‐Keuls pairwise multiple comparisons test.

Results Results were considered statistically significant at p < .05. There was a statistically significant difference between alginate materials (p < .0001). The Newman‐Keuls multiple comparisons procedure showed that Tare‐Free Alg (514.5 g/cm) had a significantly higher tear strength value (p < .0001) than Jeltrate (259.0 g/cm), Identic (289.9 g/cm), and Kromopan (323.9 g/cm).

Conclusions Tara‐Free Alg had the highest tear strength value, followed by Jeltrate, Identic, and Kromopan.
Two‐Piece Occlusion Rim for Screw‐Retained Implant Prosthesis
Authors: Orenstein Jonathan H. , Appleby David C. , Blitzer Robert M. , Cohen Stephen R.
Published: March 2005

The record base for a multiple, implant‐supported, fixed prosthesis may be attached to the implants by screws. The screw attachment provides a stable record base for recording maxillo‐mandibular relationships. Extraoral adjustment of the occlusion rim requires that it be unscrewed to allow removal from the mouth. The rim must be reattached with screws for the next intraoral evaluation. Although this cycle of removal and replacement provides stability, retention, and accuracy, it is time‐consuming and inefficient. To resolve this problem, a two‐piece record base/occlusion rim can be used. The screw‐retained record base remains intraoral for the duration of the clinical appointment. The occlusion rim is designed to fit over the record base, with retention and stability, without screw retention. Use of the two‐piece record base/occlusion rim facilitates convenient removal, adjustment, and replacement of the occlusion rim.
Computed Tomographic Scan Template for Maximum Accuracy of Reformatted CT Scan Images
Authors: Lee Sang‐Jik , Toothaker R. W.
Published: March 2005

The dental computed tomographic (CT) scan is useful in presurgical planning for implant prosthodontics. To provide accurate information, the patient must be positioned properly during the scan procedure. This article describes a method for fabricating a template that provides guidance to the CT technologist for desired head orientation of the patient.
Facilitated Cement Removal Technique Between Splinted Crowns
Authors: Sato Yuuji , Kubo Takayasu , Okane Hideaki
Published: March 2005

A technique for facilitating cement removal between splinted crowns is described. The technique involves tying dental floss with the large‐diameter yarn portion around the embrasure of the splinted crown before cementing, and pulling it through before the cement has reached a final set. This simple, quick technique achieves removal of cement without damage to the interproximal crown surface.
Fabricating a Gold Occlusal Platform on a Removable Partial Denture to Help Prevent Extrusion of Mandibular Incisors
Authors: Cobb George W. , Metcalf A. Max , Duncan J. David
Published: March 2005

A clinical procedure is presented in which a maxillary removable partial denture (RPD) replacing anterior teeth was fabricated with a cast gold anterior occlusal platform. This treatment is indicated to correct abrasion caused by extruded mandibular anterior teeth on the maxillary RPD. The advantages compared with prosthetic teeth supported by an acrylic resin base or metal‐backed facings are discussed. This technique allows for development of optimal esthetics, strength, and durability, while preventing further extrusion and excessive wear of the teeth occluding against prosthesis.
Comparison of Perceptions of Computer‐Animated Left‐ and Right‐Facing Profiles
Authors: Anderson Nina K. , Evans Carla A. , Giddon Donald B.
Published: March 2005

Purpose

Although scientific publications differ in displaying left‐ or right‐facing profiles, there are few systematic studies of the possible effects of directional biases and laterality on patients' and clinicians' perceptions of treatment need, outcomes, and satisfaction. As part of a research program to quantitate the physical bases of the perceived zone of acceptability and most‐pleasing facial profiles, responses to computer‐animated left‐ and right‐facing soft‐tissue profile images were compared and related to eye and hand preference.

Materials and Methods

Standardized left‐facing, soft‐tissue profile images were captured in color and digitized. The right‐facing profile was created by reversing the left profile image to display a mirror image. Using imaging and customized morphing software, retrusive and protrusive extremes were created, from which transitional frames were developed to display five features of the soft‐tissue profile: upper lip, chin, bimaxillary position, lower face height, and mandible. One left‐ and one right‐facing profile for a Class II division 1 female, and Class III male were randomly presented to 24 subjects who were asked to indicate: 1) acceptability by pressing a mouse button and releasing the button when the images were no longer acceptable; and 2) most‐pleasing image by pressing the mouse button once.

Results

No differences were found between left‐ and right‐profile images for zone of acceptability, midpoint of the zone of acceptability, or most pleasing; nor was there any relation to laterality measures. However, consistently higher intercorrelations among the features for the zone of acceptability were found for the left‐ than for the right‐facing profiles for retrusive to protrusive and protrusive to retrusive excursions measured in millimeters (p < .001). The bimaxillary position accounted for most of the variance in judgments of acceptability with greater influence on the left than on the right profile.

Conclusion

With the increasing use of computer‐imaging in dental practices, the influence of psychophysical and other environmental variables on perception must be considered.
Evaluation of a Computer‐Aided Learning Program in Removable Partial Denture Framework Designing
Authors: Lechner Sybille K. , Lechner Katherine M. , Thomas Graham A.
Published: March 2005

Assessment of a computer‐assisted learning (CAL) program dealing with designing removable partial dentures was performed as both formative and summative evaluation. Formative evaluation was obtained through open‐ended questions in a written questionnaire administered to 60 junior students from two Australian Dental Schools and through observation of four groups of these students as they worked through the program. Formative evaluation, fundamental to completion of the program, led to several changes and additions. Observation of the students using the program during its final stages of development was one of the most informative and helpful parts of the evaluation. It allowed nuances of expression and body language to be noted that would not have been apparent in written or numerical data. Summative evaluation was obtained through structured questions in the questionnaire and through a post‐CAL test under examination conditions. Summative assessment showed that students could attain a desired standard of knowledge if a lecture series was replaced by the CAL program; that the program was user‐friendly, even for students with little or no computer experience; and that most students considered it to be a useful learning resource. More than half the students were concerned about using CAL to replace human instruction. It is significant that students were particularly impressed by aspects of the program that could not be duplicated by a book; the interactive nature of the learning process and the ability to rotate the diagnostic casts. This highlights the need for CAL programs to use the full potential of computer capability, rather than merely replicate a textbook on a screen.
Silicone Thermoplastic Sheeting for Treatment of Facial Scars: An Improved Technique
Authors: Bradford Brant A. , Breault Lawrence G. , Schneid Thomas , Englemeier Robert L.
Published: March 2005

Silicone thermoplastic sheeting has been used successfully in the management of hypertrophic and keloid scars resulting from thermal burn injuries. A technique is described that incorporates silicone thermoplastic sheeting for fabrication of a compression face mask. This technique combines the moldability of thermoplastic splinting materials with the therapeutic surface of silicone, yielding the advantages of both in a one‐step process.
Distortion of Three‐Unit Implant Frameworks During Casting, Soldering, and Simulated Porcelain Firings
Authors: Zervas Photios J. , Papazoglou Efstratios , Beck F. Michael , Carr Alan B.
Published: March 2005

Purpose

The aim of this study was to assess distortion inherent in casting, soldering, and simulated porcelain firings of screw‐retained, implant‐supported three‐unit fixed partial dentures (FPDs).

Materials and Methods

Ten wax patterns were fabricated on a die‐stone cast containing two implants, 20 mm apart from center to center. Five specimens were cast in a high‐palladium alloy, exposed to simulated porcelain firings, sectioned, and then soldered with low‐fusing solder. Five specimens were cast, sectioned, soldered with high‐fusing solder, and then exposed to simulated porcelain firings. For each specimen, two horizontal and six vertical distances between appropriately scribed reference points were measured with a traveling microscope. Comparisons were made among the various measurements taken after wax‐pattern fabrication, casting, high‐ and low‐fusing soldering, and each porcelain firing. Data were analyzed using a repeated‐measures factorial ANOVA (α= 0.05).

Results

Significant difference was detected in the amount of horizontal distortion during casting (53 ± 24 μm) and high‐fusing soldering (−49 ± 50 μm), as well as in the amount of horizontal distortion during high‐fusing soldering (−49 ± 50 μm) and low‐fusing soldering (17 ± 26 μm). However, no clinically significant difference was found in the amount of horizontal distortion during casting, low‐fusing, and high‐fusing soldering. The greatest amount of distortion during the simulated porcelain firings took place during the oxidizing cycle.

Conclusions

Soldering did not improve the casting misfit of a three‐unit implant‐retained FPD model. Metal‐ceramic implant frameworks should be oxidized before intraoral fit evaluation.