bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retention of cast posts cemented with zinc phosphate cement using different cementing techniques
Authors: Fakiha Zaki , Al‐Aujan Arwa , Al‐Shamrani Saleh 
Published: August 2004

Purpose This study compares the effect of different cementation techniques on the retention of cast posts and cores.Materials and Methods Twenty‐four extracted single rooted human teeth were used in this study. After routine preparation of the root canals, the canal space was enlarged with reamers. Direct post patterns were made with acrylic resin. Castings were fabricated using Ni‐Cr‐Mb alloy. Zinc phosphate cement was used as a luting agent using 4 different methods of cement introduction to the root canal space. This created 4 treatment groups consisting of 6 teeth in each group. In Group A, the cement was applied over the posts only. For the specimens in Group B, the cement was introduced into the root canals with a spiral filler and applied over the posts. In Group C, cement was injected into the root canals and then applied over the posts. Finally, for the specimens in Group D, cement was injected into the root canals and a spiral was used to spread it into the root canals, and cement was also applied over the posts. After cementation, teeth were stored in saline solution. The tensile retentive force of cast posts was evaluated using the Instron testing machine (Instron, Canton, MA).Results The retention obtained by the 4 techniques differed significantly (p < .05). The highest tensile force to post dislodgment was observed in Group D, and the least was in Group A. Analysis of variance test revealed a highly significant difference between groups (p < .0001). According to the Fisher exact test, there was a significant increase in retention from Group A to Group D (p < .05).Conclusions Under the conditions of this study, the injection of cement into a root canal space followed by the use of a spiral resulted in the highest level of post retention. Retention was reduced when cement was placed using a Lentulo spiral alone (Kerr/Sybron Corp, Romulus, MI), a Jiffy tube (Teledyne Water Pik, Allegheny Teledyne Co, Fort Collins, CO) alone, or by application to the post only.
Factors influencing optical 3D scanning of vinyl polysiloxane impression materials
Authors: DeLong Ralph , Pintado Maria R. , Ko Ching‐Chang , Hodges James S. , Douglas William H. 
Published: August 2004

Purpose Future growth in dental practice lies in digital imaging enhancing many chairside procedures and functions. This revolution requires the fast, accurate, and 3D digitizing of clinical records. One such clinical record is the chairside impression. This study investigated how surface angle and surface roughness affect the digitizing of vinyl polysiloxane impression materials.Materials and Methods Seventeen vinyl polysiloxane impression materials were digitized with a white light optical digitizing system. Each sample was digitized at 3 different angles: 0°, 22.5°, and 45°, and 2 digitizer camera f‐stops. The digitized images were rendered on a computer monitor using custom software developed under NIH/NIDCR grant DE12225. All the 3D images were rotated to the 0° position, cropped using Corel Photo‐Paint 8 (Corel Corp, Ottawa, Ontario, Canada), then saved in the TIFF file format. The impression material area that was successfully digitized was calculated as a percentage of the total sample area, using Optimas 5.22 image processing software (Media Cybernetics, LP, Silver Spring, MD). The dependent variable was a Performance Value calculated for each material by averaging the percentage of area that digitized over the 3 angles. New samples with smooth and rough surfaces were made using the 7 impression materials with the largest Performance Values. These samples were tested as before, but with the additional angle of 60°. Silky‐Rock die stone (Whip Mix Corp, Louisville, KY) was used as a control.Results The Performance Values for the 17 impression materials ranged from 0% to 100%. The Performance Values for the 7 best materials were equivalent to the control at f/11 out to a surface angle of 45°; however, only Examix impression material (GC America Inc, Alsip, IL) was equivalent to the control at f/11^16. At the 60° surface angle with f/11^16, the Performance Values were 0% for all the impression materials, whereas that for the control was 90%. The difference in the Performance Values for the smooth and rough surface textures was 7%, which was not significant.Conclusions The digitizing performance of vinyl polysiloxane impression materials is highly material and surface angle‐dependent and is significantly lower than the die stone control when angles to 60° are included. It is affected to a lesser extent by surface texture.
Development of a nondestructive compliance test for resilient denture liners
Authors: Pesun Igor J. , Villar Anamaria , Hodges James S. , DeLong Ralph , Lai Juey H. , Schneider Donald 
Published: August 2004

Purpose Resilient denture liners are prescribed for patients who cannot adjust to hard‐based dentures because of a thin mucosa or severe alveolar ridge resorption. A nondestructive test to evaluate compliance of new soft liner materials will be useful in clinical trials. The purpose of this study was to evaluate a nondestructive compliance testing technique designed to characterize long‐term, silicone‐based resilient denture liner materials.Materials and Methods Samples of thicknesses of 1.1, 2.2, 3.3, and 4.4 mm of 2 materials (MPDS‐SL [Lai Laboratories, Inc, Burnsville, MN] and Molloplast‐B [Buffalo Dental, New York, NY]) were assessed for compliance using a closed‐loop servohydraulic testing system, applying a 3 lb force following a squarewave pattern; force and position values were recorded using a storage oscilloscope. The oscilloscope values were analyzed using computer software to determine compliance values. The effect of material thickness was examined by testing wedges of the 2 materials.Results The testing technique used showed that differing thicknesses had significantly different compliance values (p < .0001). In the materials used to evaluate the technique, MPDS‐SL behaved more elastically than did Molloplast‐B (p < .0001). Material thicknesses beyond 2.2 mm did not increase compliance, although MPDS‐SL had a steeper thickness‐compliance curve than Molloplast‐B.Conclusions The method used to test compliance proved to be sufficiently sensitive to distinguish between 2 materials and between varying thicknesses. The sensitivity and nondestructive nature of this test show its suitability for clinical evaluation of resilient denture liners.
Effect of light source and time on the polymerization of resin cement through ceramic veneers
Authors: Rasetto Flavio H. , Driscoll Carl F. , von Fraunhofer Joseph A. 
Published: August 2004

Purpose The purpose of this study was to evaluate the efficiency of 3 different light sources to polymerize a light curing resin cement beneath 3 types of porcelain veneer materials.Materials and Methods A conventional halogen light, a plasma arc light, and a high intensity halogen light were used to polymerize resin cement (Variolink II; Ivoclar North America Inc, Amherst, NY) through disks of veneer materials. Equal diameter and thickness disks of feldspathic porcelain (Ceramco II; Ceramco Inc, Burlington, NJ), pressable ceramic (IPS Empress; Ivoclar North America Inc), and aluminous porcelain (Vitadur Alpha; Vident Inc, Brea, CA) were used as an interface between the curing light tips and the light polymerized resin cement. The resin cement/veneer combinations were exposed to 4 different photopolymerization time protocols of 5 seconds, 10 seconds, 15 seconds, and 20 seconds for high intensity light units (Apollo 95E [Dental Medical Diagnostic Systems Inc, Westlake Village, CA] and Kreativ 2000 [Kreativ Inc, San Diego, CA]), and 20 seconds, 40 seconds, 60 seconds, and 80 seconds for conventional halogen light (Optilux; Demetron Research Inc, Danbury, CT). A surface hardness test (Knoop indenter) was used to determine the level of photopolymerization of the resin through the ceramic materials with each of the light sources. The data were analyzed by one‐way analysis of variance and a post‐hoc Scheffe test (p < .05).Results The data indicates that the Variolink II Knoop Hardness Number values vary with the light source, the veneer material, and the polymerization time. For a given light and veneer material, Knoop Hardness Number increases with longer polymerization times. The Kreativ light showed statistically significant differences (p < .05) between all test polymerization times. Use of this light required a polymerization time of greater than 20 seconds to reach maximum resin cement hardness. For samples polymerized with the Apollo light, there were statistically significant (p < .05) differences in surface hardness between samples polymerized at all times, except for the 15‐second and 20‐second times. Samples polymerized with the halogen light showed no statistically significant (p < .05) differences in hardness between polymerization times of 60 seconds and 80 seconds.Conclusions High intensity curing lights achieve adequate polymerization of resin cements through veneers in a markedly shorter time period than the conventional halogen light. However, the data in this report indicate that a minimum exposure time of 15 seconds with the Kreativ light and 10 seconds with the Apollo 95E light should be used to polymerize the Variolink II resin, regardless of the composition of the veneer. Conventional halogen lights required a correspondingly greater polymerization time of 60 seconds.
A comparison of palatal adaptation in acrylic resin denture bases using conventional and anchored polymerization techniques
Authors: Laughlin Gayle A. , Eick J. David , Glaros Alan G. , Young Leslie , Moore Dorsey J. 
Published: August 2004

Purpose The study investigated the effects of palatal depth and a resin anchoring system on the adaptation of denture base resin to the master cast after compression molding and heat polymerization.Materials and Methods Forty‐eight virtually identical polymethyl methacrylate dentures were fabricated on master casts with either a deep or shallow palatal vault. One half of the master casts of each palate type were altered by the addition of anchoring holes along the posterior land area, as well as perpendicularly in the midsaggital area. Anchoring holes were made with a #8 round bur to a depth of 5 mm. Twenty‐four hours after polymerization, the bases on their casts were sectioned at the posterior border and evaluated for degree of adaptation using a traveling microscope. Maladaptation at the interface of the denture base and master cast was measured at predetermined mediolateral locations. A split‐plot analysis of variance (α= 0.05) was performed followed by a post‐hoc Dunn Multiple Comparison Test.Results In general, depth of the palatal vault did not significantly influence denture palatal discrepancy (p= .0780), but the use of the anchoring system significantly reduced mean gap distances (p= .000). At lateral and midpalate locations, gap distances between the denture bases and their casts were reduced from approximately 0.3 mm to approximately 0.1 mm when the anchoring system was used.Conclusion Mean gap distances for steep palate dentures were significantly less than shallow palate dentures at vestibule and lateral palate locations, and anchoring holes placed in an edentulous master cast along the posterior land area and at the midline significantly improved the adaptation of denture bases.
Color stability of provisional restorative materials after accelerated aging
Authors: Doray Pamela G. , Li Dongfang , Powers John M. 
Published: August 2004

Purpose Color of 11 provisional restorative materials (4 acrylic resins and 7 resin composites) was evaluated by reflection spectrophotometry immediately after fabrication, after aging for 15 kJ/m2, and after aging for 60 kJ/m2 to determine relative color stability under experimental aging conditions.Materials and Methods Specimens of provisional restorative materials were polymerized according to manufacturers' instructions and aged in an artificial aging chamber with exposure to a total ultraviolet irradiation of 60 kJ/m2 in increments of 15 kJ/m2. Color was measured by CIE L*a*b* on a reflection spectrophotometer before and after aging. Color change (ΔE*) was calculated and analyzed statistically by analysis of variance with repeated measures after 15 and 60 kJ/m2 intervals of aging.Results Statistically significant changes in color were observed after accelerated aging at both the initial and final aging intervals. Five of the 11 provisional materials tested showed perceptible color change (ΔE* from 3.6 to 9.3) after accelerated aging of 15 kJ/m2. Seven of the 11 provisional materials tested showed perceptible color change (ΔE* from 3.4 to 9.4) after accelerated aging of 60 kJ/m2.Conclusion Clinically perceptible color changes (ΔE*Δ 3.3) can be expected in some acrylic resin and composite resin provisional materials after accelerated aging.
Effect of dowel space preparation and composite cement thickness on retention of a prefabricated dowel
Authors: Hagge Mark S. , Wong Ralan D. M. , Lindemuth James S. 
Published: August 2004

Purpose This investigation examined what effect cement thickness had on retention of prefabricated endodontic dowels luted with a composite resin cement (Panavia 21 OP; J Morita, Irvine, CA) into canals previously obturated with gutta percha and a eugenol‐based sealer.Materials and Methods Sixty‐four single‐rooted teeth were decoronated, filed, cleaned, and sequentially shaped with sizes 2–5 Gates Glidden drills (Dentsply/Maillefer, Tulsa, OK) and 0.12 taper rotary instrumentation. Teeth were then divided into 4 groups of 16 specimens each. All specimens were obturated with gutta percha and a eugenol‐based sealer. Dowel space preparation and dowel cementation were completed 1 week after obturation. Ten‐millimeter‐deep dowel spaces were prepared using dowel drills with 4 different diameters: size 5 Parapost drill (Group 1; Coltene/Whaledent, Mahwah, NJ); size 5.5 Parapost drill (Group 2; Coltene/Whaledent); size 6 Gates Glidden drill (Group 3; Dentsply/Maillefer); size 6 Parapost drill (Group 4; Coltene/Whaledent). Size 5 Paraposts were then cemented with Panavia 21 OP. After 48 hours of storage, specimens were mounted in polyvinyl chloride (PVC) pipe with acrylic, and the dowels were removed in tensile mode using a universal testing machine at 1 mm/min, with data recorded in kilograms.Results (all values in kilograms) Group 1 (Parapost 5) mean = 15.07, 95% confidence interval (CI) =±6.11; Group 2 (Parapost 5.5) mean = 25.60, 95% CI =±7.39; Group 3 (Gates‐Glidden 6) mean = 43.15, 95% CI =±7.81; Group 4 (Parapost 6) mean = 37.75, 95% CI =±6.35. Analysis of variance and Bonferroni tests revealed that Group 3 had significantly greater mean retention strength values than Group 1 and Group 2 (p < .05), and that Group 4 had significantly greater mean retention strength values than Group 1 (p < .05).Conclusions Paraposts cemented with Panavia 21 OP showed significantly greater retention in oversized dowel spaces compared with dowel spaces prepared with the manufacturers' matched dowel‐drill set.
In vitro evaluation of the retention of composite fiber and stainless steel posts
Authors: Gallo John R. , Miller Troy , Xu Xiaoming , Burgess John O. 
Published: August 2004

Purpose This study compared the tensile retentive strength of composite fiber‐reinforced dowels luted with a resin cement to stainless steel dowels luted with zinc phosphate cement.Materials and Methods The crowns of 40 extracted human mandibular premolars were removed with a separating disc 1‐mm coronal to the cementoenamel junction. The teeth were randomly divided into 4 groups (n = 10). A post space was prepared in each specimen to a depth of 9 mm, using the drill supplied by the respective manufacturer. For the stainless steel post group, 1.25‐mm‐diameter posts were cemented with zinc phosphate cement. For the composite fiber reinforced groups, posts with diameters of 1.00, 1.25, and 1.50 mm were luted with a Bisphenol A‐Glycidyl Methacrylate (BIS‐GMA) resin bonding system (Jeneric/Pentron, Wallingford, CT) according to manufacturer specifications. The specimens were stored in a sealed container with a moist environment for 24 hours, placed in a fixture in an 801 Materials Test Systems (MTS) machine (MTS Systems Corp, Minneapolis, MN), and loaded in tension at a rate of 5.0 mm/min until failure. Differences among the 4 groups were determined using a one‐way analysis of variance and Tukey‐B post‐hoc tests (α= 0.05).Results The mean loads to failure ranged from 43.9 ± 10.4 kg for the stainless steel dowel group to 19.9 ± 5.7 kg for the composite fiber–reinforced 1.00‐mm‐diameter group. The stainless steel post luted with zinc phosphate cement provided significantly greater tensile resistance than all composite fiber dowel groups. The retention of the 1.00‐mm composite fiber–reinforced post was significantly less than the remaining groups.Conclusions Under the conditions of this study, the stainless steel dowel luted with zinc phosphate cement provided significantly greater retention.
Finite element analysis on dental implant–supported prostheses without passive fit
Authors: Kunavisarut Chatchai , Lang Lisa A. , Stoner Brian R. , Felton David A. 
Published: August 2004

PurposeThe purpose of this study is to use finite element analysis to investigate the effect of misfit prostheses, cantilever prostheses, and various occlusal forces on the stress distribution in the prostheses, implant components, and surrounding bone.Materials and MethodsTwo 3‐dimensional finite element models were constructed: (1) a 2‐implant–supported, 2‐unit fixed partial denture and (2) a 2‐implant–supported, 2‐unit fixed partial denture with a distal cantilever. Variations of the standard finite element models were made by placing a 111‐μm gap between the gold cylinder on either the mesial or distal implant. The effects of load of 100 N were tested on all models. Subsequently, loads of 50 N, 200 N, and 300 N were evaluated on the cantilever model.ResultsWhen the gap was positioned near to the applied force, the stress in both models increased significantly in the implant components and surrounding bone. The stress increase in each component ranged from 8% to 64% in the non‐cantilever models and 43% to 85% in the cantilever models. The greatest stress was found in the distal gold screw. The effect of the gap was clearly shown by the pattern of stress distribution in both models. Additionally, the presence of a cantilever and excessive occlusal force amplified the effect of prosthesis misfit.ConclusionsProsthesis misfit influenced the pattern and magnitude of stress distribution in the prosthesis, implant components, and surrounding bone, and the presence of the cantilever or greater occlusal force amplified the effect of misfit.
The effect of disinfectants on the properties of dental gypsum, part 2: Surface properties
Authors: Abdelaziz Khalid M. , Combe Edward C. , Hodges James S. 
Published: August 2004

Purpose This study is part of an ongoing investigation to evaluate the surface properties of dental stones mixed with disinfection solutions, and to determine the effect of adding gum arabic and calcium hydroxide on the same properties.Materials and Methods Aqueous solutions of 2 chemical disinfectants were used in mixing 2 types of dental stones (type III and type V). These dental stones were modified further by adding 1% gum arabic and 0.132% calcium hydroxide to their hemihydrate powders before mixing. Five specimens prepared from each type of dental stone were classified into 7 groups according to the hemihydrate powder modification and mixing liquid/powder ratio. Surface roughness was tested by 2‐dimensional profilometery and scanning electron microscopy (SEM). Knoop hardness testing was carried out, and detail reproduction was assessed using ADA specification 25 in addition to SEM and 3‐dimensional profilometer studies.Results Dental stones mixed with chemical disinfectants showed higher average roughness (Ra) values than those of the controls. However, adding gum arabic and calcium hydroxide to the hemihydrate powders before mixing restored values to the level of the control. The additives seemed to have a role in the improvement of surface hardness. There was no significant difference between the experimental and the control group in the terms of detail reproduction.Conclusions Using SEM, 3‐dimensional profilometry, and ADA testing methods, we found that the surface roughness of stone casts was adversely affected by using the disinfectant solutions as mixing water substitutes. Gum arabic and calcium hydroxide additives can yield a harder stone surface without compromising other surface properties.
The influence of plasticizer loss on the viscoelasticity of temporary soft liners
Authors: Aloul Raed K. , Shen Chiayi 
Published: August 2004

Purpose This study examined the changes in mechanical properties of temporary soft liners introduced by the differential loss of alcohol and plasticizer in different storage media.Materials and Methods Four brands of temporary soft liners were used to prepare 128 specimens on Lucite LS substrates. Each group of specimens was stored in a different medium (air, 10% ethanol, water, and artificial saliva), selected to affect the levels of plasticizer and alcohol over time. Data on weight changes, plasticizer leaching, and recovery rate were recorded at the following intervals: baseline, 2, 7, 14, 28, 56, and 176 days. The storage media were periodically renewed except during the drying stage between day 56 and 176. Two‐way analysis of variance and Duncan multiple‐range tests were performed.Results Plasticizer leaching occurs at higher levels in artificial saliva than in other storage media (P <.0001). The mean recovery rates exhibited a statistically significant increase (indicating reduced viscoelasticity) in more of the artificial saliva specimens than in all other test groups (P <.0001). Comparatively, the rates of recovery were lower in the 10% ethanol storage medium (except Lynal) with a statistically significant difference attained with the higher air‐stored specimens in Tempo and Coe‐Comfort (P <.0001). During the drying phase, weight changes in the 10% ethanol group were higher than those in the other storage media.Conclusions The study supports the contention that alcohol may have been retained in the 10% ethanol group in a manner that extended the viscoelasticity of the material. The roles of alcohol and plasticizer content in the mechanical properties of temporary soft liners depend on the type of temporary soft liners and on the nature/duration of service desired. Storing dentures lined with tissue conditioners under dry conditions and those lined with true soft‐liners in an ethanol humidor may be justified to extend serviceability by minimizing the loss of the component most relevant to viscoelasticity.