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The compatibility of different dental materials (root canal sealer and composite core build-up restoratives) is an important factor for a successful restoration. The aim of this in vitro study was to determine the effects on compressive and diametral tensile strength of a classical chemical cure composite resin (Henry Schein Composite Anterior-Posterior dental restorative) when in contact with either eugenol or an epoxy-resin (EZ-Fill) in a variety of situations: (a) eugenol or epoxy-resin added during mixing of a composite resin before curing; (b) vapor exposure to cured samples; and (c) specimens placed directly in eugenol or epoxy-resin (after curing). Compressive strengths and diametral tensile strengths were tested for each group. Only the addition of eugenol during mixing with the composite resin (directly before curing) resulted in specimens that were unable to be tested, because they did not achieve a full cure or hardness. For all other groups, there were no significant differences with respect to either compressive strength (p = 0.17) or diametral tensile strength (p = 0.39). Group 1 (mixed directly with eugenol) was found to be statistically different from groups 2 through 7.

The use of dental amalgam as a direct restorative material has been a subject of controversy for many years. The potential safety of amalgam has been questioned because of leakage of elements such as mercury, copper, tin, and silver.This study evaluated the elemental leaching from Tytin dental amalgam placed in deionized water for 2 months. Both mercury vapor and elemental (silver, copper, tin, and mercury) analyses were performed.Two capsules of Tytin amalgam were triturated (one for the precipitate and liquid analysis, and the other for the mercury vapor analysis) and stored in a polypropylene tube with 10 mL deionized water for 60 days at room temperature. The amalgam pellet then was removed and rinsed with deionized water. The resulting liquid was separated from a precipitate, and 2 separate analyses were run: one on the liquid without any precipitate and another on the precipitate. Elemental analyses for copper (Cu), tin (Sn), mercury (Hg), and silver (Ag) were determined by inductively coupled plasma-emission spectroscopy with a Perkin-Elmer P2000 spectrometer. Mercury vapor analyses were performed daily for 60 days with a Jerome 431-X vapor analyzer.The maximum amount of copper (80 microg), silver (2.6 microg), mercury (15 microg), and tin (550 microg) was found in the precipitate. The maximum amount of mercury vapor released was 67 microg/m(3)/d.Under the conditions of this in vitro study, there was a significant amount of elemental leaching and mercury vapor release from the Tytin amalgam over a 60-day period.

Statement of Problem: There are no studies analyzing the effects of a crown in relationship to torsional resistance for a titanium-reinforced core material supported by a post. Purpose: This study investigated the effects of post design on the torsional resistance of a crown supported by a titanium-reinforced composite core material (Ti-Core) and 3 endodontic posts (AccessPost, Flexi-Post, and ParaPost). Material and Method: Three groups of 10 specimens per group were studied. A total of 30 recently extracted human single-rooted (incisors) teeth with their crowns removed were used. Post holes preparations were created according to manufacturer's instructions. All posts were cemented using Flexi-Flow with titanium cement. Scotchbond Multi-Purpose bonding system was used as the bonding system for all groups. All cores were fabricated with Ti-Core with titanium core material with hard copper bands as the matrix. The Ti-Core core material was allowed to set for 1 hour. Metal crowns were fabricated and cemented with zinc phosphate cement. Specimens were placed in a special jig and a clockwise torsional force was applied. Torsional force was measured on a Lebow 1102-200 torque transducer and recorded on a Hewlett Packard 7015B X-Y recorder in inch × ounce. A 1-way analysis of variance (ANOVA) was used to test for statistical significance ( P Results: The torsional values (inch × ounce) were AccessPost 77.2 ± 30.3, Flexi-Post 162.2 ± 51.2, and ParaPost 60.9 ± 28.4. SNK and Scheffe comparison tests revealed that the Flexi-Post group had significantly greater resistance to torque loading than the AccessPost and ParaPost groups, which were statistically similar to each other. Conclusion: Post design has an effect on torsional resistance of a crown supported by titanium-reinforced core build-up and post. The threaded split-shank design of the Flexi-Post dowel offers significantly greater resistance to torsional loading than the passive posts studied. (J Prosthet Dent 2000;84:38-42.)

Statement of Problem: There are few studies on the retention of core build-up materials to prefabricated post head designs, especially for a new ceramic post design. Purpose: This in vitro study compared the retention of 2 types of core build-up materials (Ti-Core titanium-reinforced composite and a GC Miracle Mix silver-reinforced glass ionomer) supported by 3 post head designs (Flexi-Post, AccessPost, and Cerapost dowel). For all test groups, heads of the posts were placed into the core material at a 90-degree angle to the surface. Test specimens (unloaded) were then placed into a special jig and retention test was performed using an 810 MTS testing machine. Material and Methods: This study consisted of 6 groups with 10 specimens per group. A 3 × 2 factorial design was used to test for statistical significance and results were considered significant when P Results: Results of the retention test were as follows: group 1, Flexi-Post/Ti-Core 220.0 lb (982.1 N), group 2, AccessPost/Ti-Core 212.7 lb (949.6 N), group 3, Cerapost/Ti-Core 41.8 lb (186.6 N), group 4, Flexi-Post/Miracle Mix 43.4 lb (193.8 N), group 5, AccessPost/Miracle Mix 61.6 lb (275 N), and group 6, Cerapost/Miracle Mix 7.5 lb (33.5 N). Results of the ANOVA revealed a highly significant difference between posts and cores ( P Conclusion: Post head designs of the stainless steel AccessPost and Flexi-Post dowels offers greater retention then the smooth ceramic head design of the Cerapost dowel. In addition, the composite core material (Ti-Core) offers greater retentive strength values than the glass ionomer material (Miracle Mix). (J Prosthet Dent 2000;83:624-8.)

This pilot study concerned the cyclic fatigue of five different endodontic post systems (AccessPost(R), Flexi-Flange(R), Flexi-Post(R), ParaPost(R), and Vlock(R)) with four different core materials (Tytin(R) Silver amalgam, Ti-Core(R), Ketac-Silver(R) and G-C Miracle Mix(R)). In vitro cyclic fatigue was performed using a fatigue machine that simulates masticatory fatigue forces. An instantaneous force of 5 lb was applied to each post and core combination for a test configuration of 4 000 000 repetitions or until failure occurred. The type of failure and number of repetitions at failure was recorded for each sample tested. Two-way ANOVA was used to compare groups. All posts/core samples with Ti-Core and Tytin Silver amalgam completed the test configuration of 4 000 000 cycles without failures. All posts/core samples with Ketac-Silver failed before the 4 000 000 test cycle configuration, all as a result of core failures. All posts/core samples with G-C Miracle Mix failed in a similar way. The Newman-Keuls multiple comparison test illustrated that Ti-Core and Tytin Silver amalgam were similar to each other and were superior to both G-C Miracle Mix and Ketac-Silver. Similar fatigue test results are found in the literature.

There are no studies analyzing the effects of a bonding agent on torsional resistance for a titanium-reinforced core material bonded with a multistep bonding system.This pilot study investigated the effects of multistep bonding agents on torsional resistance of a titanium-reinforced composite core material (Ti-Core core material).A total of 40 recently extracted human molars with their crowns removed were placed into acrylic resin blocks and divided into 4 groups of 10 specimens. Only multistep bonding systems were used (AllBond-2, ScotchBond Multi-Tenure AB, and the control without bonding agent). Specimens were prepared according to manufacturer's instructions. The control group was etched with a 37.5% phosphate acid. All cores were fabricated with Ti-Core titanium core material with No. 1 hard copper bands as the matrix. Ti-Core core material was applied and allowed to cure for 1 hour, then the cores were placed in 100% humidity (water) for 1 week. Test specimens were placed in a special jig and a clockwise torsional force applied. Torsional force was measured on a Lebow 1102-200 torque transducer and recorded on a Hewlett Packard 7015B X-Y recorder in inch x ounce then converted into Newton-meter. One-way analysis of variance (ANOVA) was used to test for statistical significance (P.05).Torsional values (Newton-meter) were AllBond-2, 0.1980, ScotchBond Multi-0.1890, Tenure AB, 0.2142; the control group recorded a value of zero. Statistical analysis revealed that bonding systems did not differ from one another.Use of a bonding agent increased the core's resistance to torsional forces. Lack of a bonding agent dramatically reduced the resistance to torque.

There are no studies that have investigated the effects of bonding agents on the resistance to torque of a composite core supported by a prefabricated post.This study investigated the ability of bonding agents to resist rational forces applied to titanium-reinforced composite cores supported by 2 post designs.Two post designs (AccessPost and ParaPost dowels) with titanium-reinforced core material and 4 bonding conditions (AllBond-2, ScotchBond Multi-Purpose, Tenure AB, and without a bonding agent) were studied. A total of 80 specimens in 8 experimental groups were prepared and subjected to clockwise torsional forces until failure.Torsional values ranged from 53.31 in. x oz (ParaPost/ScotchBond Multi-Purpose) to 72.31 in. x oz (AccessPost/ScotchBond Multi-Purpose). Two-way of analysis of variance failed to demonstrate a significant difference among posts or type of bonding system.The use of a multistep bonding agent had no significant effect on the torsional resistance of a core supported by a passive endodontic post.

Statement of problem. The retention of a post is believed to be a major factor in restoration survival. Therefore the cement with the greatest in vitro retention property should give the best performance for a restoration. Purpose. This study compared retentive values of three posts (Flexi-Post, AccessPost, and ParaPost) cemented with five cements (Flexi-Flow, zinc phosphate, Advance, Duet, and Ketac-Cem) plus a control group that consisted of a Flexi-Post No. 2 dowel without cement. Material and methods. A total of 160 recently extracted human single-rooted teeth with crowns removed at the cementoenamel junction were divided into 16 groups of 10 samples. Post holes were prepared according to manufacturers' instructions. Posts were then cemented with one of the five cements. Each sample was placed into a specialized jig and on a tensile testing machine with crosshead speed of 0.638 cm/minute, applied until failure. A two-way analysis of variance and Newman-Keuls multiple range comparison tests were performed for all cemented groups. A one-way analysis of variance and a Student-Newman-Keuls multiple range comparison test were performed only for the groups with the Flexi-Post dowel, this included the no cement condition, with significant results if p Results. Flexi-Post dowel with Flexi-Flow Natural cement obtained the highest retentive value (303.91 pounds). ParaPost dowel with Duet cement exhibited the lowest retention value (21.23 pounds). The Flexi-Post dowel demonstrated higher mean retention than AccessPost or ParaPost dowels; AccessPost dowel was higher than ParaPost dowel. Flexi-Flow cement had the highest overall mean retention followed, in decreasing order, by zinc phosphate, Advance, Ketac-Cem, and Duet cements. Conclusions. Flexi-Post dowel was the most retentive post studied with values ranging from 303.91 pounds with Flexi-Flow Natural cements to 150.93 pounds without cement. Flexi-Flow cements had a higher overall mean retention than other cements studied. (J Prosthet Dent 1998;79:520-5.)

The aim of this study was to compare the fracture strengths of three restorative materials, a lanthanide reinforced composite (Ti-Core Natural), a silver amalgam (Tytin), and a hybrid glass ionomer (Advance), supported by either a multitiered, threaded split-shank post (Flexi-Flange) or with a dentin spur without a post.A total of 60 recently extracted single-rooted human teeth were divided into six groups of 10. All groups were stored at 100% humidity at room temperature for 1 week before testing. Each specimen was placed in a special jig at a 45-degree angle to the buccolingual axis and subjected to a load that was recorded in pounds and converted to Newtons on a universal testing machine, with a crosshead speed of 0.63 cm/minute until failure. Two-way analysis of variance followed by the Newman-Keuls pairwise multiple comparisons test were used to compare the results.There was a statistically significant difference between core materials (p0.001), but not regarding post conditions. Ti-Core Natural material had a significantly larger mean failure threshold for fracture than either Tytin silver amalgam or Advance material and the letter two core materials (Tytin and Advance) do not differ from each other. There was no statistical difference between Ti-Core material supported by a post and Ti-Core material supported without a post.

Purpose. This pilot study examined the cyclic fatigue of five endodontic post systems (AccessPost, Flexi-Flange, Flexi-Post, ParaPost, and Vlock) with four core materials (Tytin silver amalgam, Ti-Core, Ketac-Silver and G-C Miracle Mix). Material and methods. In vitro cyclic fatigue was performed with a machine designed to simulate masticatory fatigue forces. An instantaneous force of 22.2 N (5 pounds) was applied to each post and core combination for a test configuration of 4,000,000 repetitions, or until failure occurred. The type of failure and number of repetitions at failure was recorded for each sample tested. Two-way analysis of variance (ANOVA) was used to compare groups. Results. All posts/core samples with Ti-Core composite and Tytin silver amalgam completed the test with no failures. All posts/core samples with Ketac-Silver material failed before the 4,000,000 test cycle configuration and all failures were core failures. All posts/core samples with G-C Miracle Mix material failed in a similar manner. Newman-Keuls multiple comparison test illustrated that, with this simulated fatigue test, Ti-Core material and Tytin silver amalgam were superior to both G-C Miracle Mix and Ketac-Silver materials. (J Prosthet Dent 1997;78: 458-64.)

The aim of this study was to determine the maximum amount of power, in watts, that a Holmium YAG laser could deliver via a 245-micron fiberoptic to the canal surface and still not raise the temperature (delta T) of the cementum by5 degrees C. Sixty single-rooted teeth were divided into three groups according to power selection (0.50, 0.75, and 1.00 W). The three main outcome variables were: change in apical temperature, change in coronal temperature, and maximum size of an endodontic file that could fit into the canal after lasing. The group means for apical delta T were: 1.00 W = 2.2 degrees C, 0.75 W = 2.68 degrees C, and 0.50 W = 1.58 degrees C. The group means for coronal delta T were: 1.00 W = 1.15 degrees C, 0.75 W = 0.99 degree C, and 0.50 W = 0.56 degree C. The group means for file size were: 1.00 W = 41.25, 0.75 W = 38.75, and 0.50 W = 40.75. The canal size was increased from a size 25 file up to approximately a size 40 file with all power groups. There were no significant differences between the groups for change in apical temperature (p = 0.32), coronal temperature (p = 0.17), or maximum file size (p = 0.86) when adjustments were made for tooth dimensions. In all groups studied, the delta T was5 degrees C. This represents a safe and predictable laser procedure.

The purpose of this in vitro study was to determine the fractural load of four core materials supported by five post designs. This study was divided into 20 groups with 10 samples per group. Specimens were placed in a special jig at a 45-degree angle, and the fracture load values, in pounds, were obtained with the use of a universal testing machine. A 5 x 4 factorial design was used to assess and compare the fractural strength, and a two-way analysis of variance was used to determine whether the buccolingual, mesiodistal, and height dimensions differed across groupings. Mean fracture load values were obtained. Flexi-Post dowel/Ti-Core material at 277.1 pounds and ParaPost dowel/ Tytin silver amalgam at 277.3 pounds recorded the greatest mean values. These values were not statistically different. ParaPost dowel/Ketac-Silver material had the lowest mean value (49.6 pounds). For all posts Tytin silver amalgam and Ti-Core material were significantly stronger than Ketac-Silver and G-C Miracle Mix material. Ketac-Silver and G-C Miracle Mix materials did not differ from each other. Results indicated that Ti-Core composite material is at least as strong as Tytin silver amalgam.

In this study two precision overdenture attachment designs were tested for retention—a nylon overdenture cap system and a new cap and keeper system. The new cap and keeper system was designed to reduce the time involved in replacing a cap worn by the conditions of the oral environment. Six groups were tested at two different angles and retentive failure was examined at two different angles (26 and 0 degrees). Failure was measured in pounds with a force gauge over a 2000 pull cycle. The amount of force required to remove caps for two overdenture caps and a replaced cap for the metal keeper system was determined. Two dependent variables were absolute force and relative force. Repeated measures analysis of variance (RMANOVA) was used to compare the between-subjects effects of cap and angle, and the within-subjects effect of pull. The results indicated a significant difference between cap types (p < 0.0001) with respect to the relative force required to remove the cap. There was no effect of angle. For absolute force, RMANOVA revealed a highly significant interaction between pull and cap (p < 0.0001). Thus, the way that force changed over pulls depended on which cap was used (no effect of angle). For relative force, RMANOVA revealed no interaction between pull and cap, but there was a main effect of cap type (p < 0.0001) (no effect of angle). The nylon cap design required less force for removal but showed more consistency in the force required over the course of the 2000 pulls when compared with the keeper with cap insert. The results obtained in this study were consistent with similar studies in literature.

This in vitro study measured the time required to instrument and shape canals by conventional reamers and files compared with a newly introduced reamer and file system. This experiment was divided into four groups with 10 block samples for each group. The results of instrumentation time demonstrate that the noninterrupted flat-sided design (EZ-Fill SafeSider reamers) produced the fastest times for comparably shaped canals because of reduced engagement of the instrument with the walls of the canal compared with conventional instruments. The conventional designs for both reamers and files result in increased instrumentation time compared with their EZ-Fill SafeSider counterparts.

Purpose The purpose of this study was to evaluate the dimensional stability of three different alginate impression materials (Jeltrate [Caulk Dentsply, LD Caulk Division, Dentsply International, Milford, DE], Hydrogum [Zhermack, Padoua, Italy], and a new hydrophilic alginate material [Essential Dental Systems, South Hackensack, NJ]) under five different storage conditions. Materials and Methods The study was divided into four groups with at least eight samples in each group. The five storage conditions were as follows: immediate, 10 minutes with a wet towel, 30 minutes without a wet towel, 1 hour with a wet towel, and 24 hours with a wet towel. A 4 × 5 factorial two-way analysis of variance (P < .05) was used on each dependent variable. Dunnett's test was used to compare each alginate with Jeltrate. Results The new hydrophilic alginate (group 4, 2:2) showed smaller measurements in the buccolingual and diagonal dimensions compared with Jeltrate (control). Conclusions The immediate method (measured buccolingually and diagonally) produced more accurate casts for the alginate materials studied. All other materials studied were similar statistically. The new hydrophilic alginate in group 3 resulted in similar dimensional accuracy compared with Jeltrate and Hydrogum and incorporated 25% less water.

The binding and subsequent reactivity of dioxygen (O 2 ) upon binding to copper ion centers is of fundamental interest in chemical and biological processes. We provide here a detailed account of the reaction of O 2 with dicopper(I) complexes, involving O 2 -reversible binding, followed by the stoichiometric aromatic hydroxylation of the ligand. Thus, tricoordinated dicopper(I) complexes [Cu 2 (R-XYL)] 2+ (R=H, MeO, t-Bu, F, CN, NO 2 ; 1a-f possess dinucleating meta-substituted xylylene ligands with two chelating tridentate bis[2-(2-pyridyl)ethyl]amine (PY2) moieties and a 5-R substituent

The retention of a post in a root is critical for the successful restoration of an endodontically treated tooth. This study compared the retention of two hollow-tube post designs (Access post and World post) cemented with zinc phosphate cement or a titanium-reinforced composite resin cement (Flexi-Flow cement with titanium) with that of the control Para-Post system, a solid post design cemented with zinc phosphate cement. The experiment was divided into 11 groups of 10 samples. Retentive values were measured with a universal testing machine and the data were recorded in pounds. A one-way analysis of variance was computed and included Duncan's multiple comparisons test, Tukey's Student range test, and Dunnett's test. Duncan's multiple comparison test and Tukey's test were inconclusive. Only Dunnett's test revealed a significant difference between group 5, Access post, grooved dentin with Flexi-Flow cement with titanium (mean of 89.7 lb), and the control, group 11, Para-Post dowel cemented with zinc phosphate cement (mean of 61.3 lb). All other groups exhibited similar results with retentive values that ranged from 62 to 76 lb.

Purpose This study tested the comparative cyclic fatigue of six prefabricated post systems (Flexi-Post (Essential Dental Systems, South Hackensack, NJ), Flexi-Anterior (Essential Dental Systems), Vlock (Brasseler USA, Inc, Savannah, GA), Parapost (Whaledent/Coltenen, New York, NY), Cytco (L.D. Caulk, Milford, DE), and Access post (Essential Dental Systems). Materials and Methods Cyclic fatigue testing was obtained with an in vitro fatigue machine that simulated clinical fatigue conditions. An instantaneous applied force of 5.0 pounds was applied to each post specimen and data was recorded when post breakages occurred. If no breakages occurred, then the test was stopped after 2,000,000 repetitions. Results Failures only occurred with the Cytco and Vlock post designs. The Flexi-Post, Flexi-Anterior, Parapost and the Access post all had greater resistance to cyclic fatigue with no failures. Conclusions This experimental design may simulate biting forces and stresses seen for posts in a clinical situation.

This study determined the retention, in pounds, of Nos. 1 through 3 stainless steel attachment sleeves for the threaded split post system cemented with various cements. Post heads and matching sleeves were also sandblasted and compared with attachments not sandblasted. Four luting agents were selected, zinc oxyphosphate cement (ZOP), and three brands of composite resin cement (CRC). The experiment was divided into two parts; in part 1, samples were not treated, and in part 2, samples were sandblasted. Retentive values were recorded with a universal testing machine. A 2 × 3 × 4 factorial three-way analysis of variance was used to compute the effects sandblasting, sleeve and post type, and the luting agent. No statistical differences were recorded for sleeves not sandblasted, Nos. 1 and 2, regardless of the luting agent. The nonsandblasted No. 3 sleeve cemented with Panavia CRC had significantly greater retention than All-Bond CRC or ZOP. There were no statistical differences in retention of sandblasted sleeves for the No. 1 sleeve despite the type of luting agent. For sandblasted sleeves Nos. 2 and 3, ZOP and Panavia CRC recorded significantly greater retention than All-Bond CRC. However, there was no difference between sandblasting and not sandblasting for the No. 1 sleeve. Mean loads for Nos. 2 and 3 sleeves were substantially greater for sandblasted compared with attachments not sandblasted.

The binding of O 2 to copper(I) and its subsequent reactivity is important in a variety of chemical and biological processes. We previously studied functional models of hemocyanins (arthropodal and molluscan O 2 carriers) involving a class of O 2 adducts [Cu 2 (Nn)(O 2 )] 2+ , where Nn are dinucleating ligands which employ two tridentate bis(2-pyridylethyl)amine (PY2) moieties, connected by a variable alkyl chain.

This study compared the retention of posts in the root for various diameters (1.3 mm and 1.6 mm) of three prefabricated post systems (Unity, Filpost, and Brasseler) with that of the previously reported No. 1 and No. 2 Flexi-Post systems. The experiment was divided into three groups comprising 10 samples for each post system studied. In group 2, the Filpost system was cemented both with a resin cement and zinc phosphate cement. Retention values were obtained with a modified universal testing machine. The retention of 1.3 mm posts from most to least retentive was Flexi-Post (zinc phosphate) greater than Filpost (zinc phosphate) greater than Filpost (resin) greater than Brasseler (zinc phosphate), greater than Unity (resin). The retention of 1.6 mm posts from most to least was Flexi-Post (zinc phosphate) greater than Filpost (zinc phosphate) greater than Brasseler (zinc phosphate), Unity (resin) greater than Filpost (resin). The Filpost system achieved higher retention with zinc phosphate cement than it did with resin cement.

The mechanism of aromatic hydroxylation for 2-methyl substituted analogues of copper complexes studied previously, namely [Cu{sub 2}(Me{sub 2}XYL-CH{sub 3})]{sup 2+} (4) and [Cu{sub 2}(XYL-CH{sub 3})]{sup 2+} (5) are described in detail. Manometric O{sub 2} uptake experiments and labeling studies were used to unravel the reaction pathway. The NIH shift mechanism is said to be operative in a copper monooxygenase model system involving dicopper ion complex mediated O{sub 2} hydroxylation of an arene substrate. Manometric O{sub 2} uptake experiments and labeling studies were used to unravel the reaction pathway. 66 refs., 7 figs.

The formation of amide bonds from the reaction of metal carboxylates with amines was observed for the first time; complexes of titanium(IV), zirconium(IV) and tantalum(V) were investigated.

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.

The in vitro study measured the time required to instrument and shape canals by conventional reamers and files compared with a newly introduced reamer and file system. This experiment was divided into four groups with 10 block samples for each group. The results of instrumentation time demonstrate that the noninterrupted flat-sided design (EZ-Fill SafeSider reamers) produced the fastest times for comparably shaped canals because of reduced engagement of the instrument with the walls of the canal compared with conventional instruments. The conventional designs for both reamers and files result in increased instrumentation time compared with their EZ-Fill SafeSider counterparts.

SUMMARY Advantages of a new post design, Flexi-Flage® are described. It incorporates a split-shank parallel threaded post with a flange that seats into an occlusal countersunk dentine space. This case report desecribes placement of three Flexi-Flange posts in a first bicuspid, canine and central incisor. The Flexi-Flange system was designed to offer high retention of the post in the root, superior distribution of stresses on insertion and under function, and longterm resistance to metal fatigue.

The basics for the sound restoration of endodontically treated teeth have not changed despite the advent of new materials and techniques. Adequate retention for posts and crowns, resistance to cyclic shearing forces, minimal insertional stresses, and even distribution of functional stresses are prime requirements that cannot be compromised without jeopardizing the longevity of the final restoration.

It has been reported in the literature that after lasing dentin the dentin surface has a glassy or globular appearance. Many authors believe this to be recrystallized hydroxyapatite. The purpose of this elemental analysis was to see if any of the silica fiber optic was melted and deposited as these globular structures on the canal wall. Two teeth were used. One was hand-instrumented with files and used as the control, the other was lased with a holmium:YAG laser. A 245-micro low OH- fiber was used with a power setting of 0.75 W, 5 Hz, 94.2 J, and 1134 V to lase the root. The roots were microanalyzed for oxygen, phosphorus, silicon, nitrogen, hydrogen, calcium, and carbon. The percentages for all elements tested were the same for both teeth. Therefore, there was no silicon deposited onto the canal wall of the tooth that was lased. It is concluded that the low OH- silica fiber optic was not melted and deposited onto the dentinal canal wall.

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.

This paper describes the use of a GABA-transaminase agonist for the treatment of infantile autism. An approximate one third reduction of GABA and ammonia levels for an autistic patient with noticeable improvement of verbal/language skills and a reduction of repetitious ritualistic self-stimulatory behavior (stimming) was observed. A reduction of the plasma GABA (by administrating a GABA-T agonist, Imipramine) probably results in more axon(s)-to-oligodendrocyte signaling in the corpus callosum and it is postulated that this could result in a reduction of the autistic features for the patient.

The retention of posts in tooth roots is vital to the success of the restoration. This study compared the retention of posts of various sizes and diameters cemented with a titanium-reinforced composite cement with that of posts previously reported cemented with zinc phosphate cement. Four groups made up of 10 samples each were used and retention values were compared using a universal testing machine. Two-way analysis of variance and the Newman-Keuls multiple range comparison test were performed. Larger diameter posts cemented with titanium cement had better retention than similar posts cemented with zinc phosphate cement. The statistical increase in retention for the larger size posts is probably the result of the deeper channels (threads) in the dentin and the higher cohesive strength for the titanium-reinforced composite resin.

Statement of problem. There are few research studies concerning prefabricated posts overdenture attachment systems using multiple pull cycles. Purpose. This study tested 6 prefabricated post overdenture attachment systems (AccessPost Overdenture, ERA white and ERA grey, Flexi-Overdenture, O-SO and ZAAG) measured to simulate wear over a 2000 pull cycle and compared the in vitro retention, measured (pounds). Material and methods. Records of the pounds of force necessary to separate each system were made at the beginning of testing, at pull 10 and then at every 50th pull until the 2000th pull was attained. All pulls were performed manually with a Shimpo force gauge. Absolute force (AF) and relative force (RF) were compared, AF being the force required at any pull to separate the overdenture device, whereas RF is the force required at the first pull. Results. There was considerable difference of the force required at pull 1 for the ERA white, O-SO and ZAAG anchor systems, then the AccessPost overdenture, and finally the Flexi-Overdenture and ERA grey attachment systems. Conclusion. At pull 2000, there was no statistical difference between any of the attachments studied. The amount of force necessary to offer functional retention to a specific patient wearing an overdenture may vary considerably, depending on the many factors in fabricating the overdenture, and the age, strength, musculature, and the expectations of the patient. (J Prosthet Dent 1999;82:579-84.)

This in vitro study compared the retention and photoelastic stress patterns from two loading conditions, vertical (133.2 N, 30 pounds) and oblique at a 26 degrees angle (133.2 N, 30 pounds) for two prefabricated post systems. The post studied were: (1) Flexi-Post (a split-shank threaded post) and (2) C-Post (a carbon fibre bound in an epoxy resin, passive double taper tier post). Two groups with 10 specimens per group were subjected to retentive forces with a universal testing machine (MTS 810 Material Testing Machine). In addition, two photoelastic test blocks were prepared with simulated root canals for each post studied. After cementation the photoelastic blocks were photographed before vertical and oblique loading and after loading. One-way analysis of variance (ANOVA) for retention data revealed a highly significant difference (P

We report a novel case of a metal ion induced oxidative dehalogenation ,the first copper mediated hydroxylation induced dechlorination of an aromatic substrate.

The aim of this study was to determine if there is an increase in temperature at the root surface as the canal is enlarged when using a Holmium:YAG laser. An increase might be expected because, as the canal is enlarged, there is less dentin between the canal walls and the outer cementum surface of the root to absorb the heat. Sixty single-rooted human teeth were randomly assigned to 1 of 3 groups according to laser power settings: 0.50, 0.75, and 1.00 W. Each tooth in each power group was subjected to lasing using fiber sizes of 140, 245, 355, and 410 microns. The dependent variables in these analyses included: (a) change in temperature, measured with T-type thermocouples placed 2 mm from the coronal and apical ends of the root; (b) depth of laser in the tooth; (c) depth that a conventional fiber could be inserted after lasing; and (d) tooth physical dimensions. ANOVA for coronal temperature showed no interaction between fibers and power settings. Repeated-measures ANOVA for apical temperature showed a significant difference between fibers, but not between power settings. No interaction between fibers and power settings was observed. For the depth of tooth during lasing (how far the fiberoptic guide penetrated into the tooth), no interaction between fibers and power settings was observed. Pairwise contrasts revealed that all fibers were different from one another, with depth decreasing as fiber size increased. Depth files could be inserted that showed the depth significantly decreased as file size increased from 50 through 70. ANOVAs illustrated that there were no significant differences between power settings for any of the five tooth physical dimensions. All temperature differences observed apically and coronally were between 0 degree to 10 degrees C, with the majority (98%) being between 0 degree to 5 degrees C. After lasing with the 410-micron fiber, the root canals were widened to at least 45 or 50 K-files (450 or 500 microns). However, by using a 410-micron fiber, the laser did not seem to widen the canal beyond a 500-micron diameter.

Recently introduced single-step bonding agents reduce the number of steps involved in the bonding process. Nevertheless, there are few studies on the bond strengths obtained with these new systems.This in vitro study evaluated the shear bond strength of a titanium-reinforced cores bonded with 5 multistep bonding systems (ScotchBond Multi-Purpose, OptiBond, All Bond-2, Tenure, and ProBond) and 5 single-step bonding systems (Single-Bond, OptiBond Solo, One-Step, Tenure Quik, and PrimeBond 2.1).The experiment was divided into 10 groups with 10 specimens per group. The shear bond strengths were evaluated after 24 hours on an MTS universal testing machine with a crosshead speed of 6.35 mm/minute.A 2-way ANOVA showed that All Bond-2 and One-Step recorded the highest means and differed significantly from the Den-Mat systems (Tenure AB and Tenure Quik), the Kerr systems (OptiBond and Opti-Solo), and the Caulk systems (ProBond and PrimeBond 2.1). ProBond and PrimeBond 2.1 bonding systems had the lowest mean and differed from the 3 other brands. Tenure AB and Tenure Quik bonding systems and OptiBond and Opti-Solo bonding systems did not differ from one another.The single-step bonding agents did not produce an improvement in shear bond strengths. The wide range of shear bond strength reported for the single-step systems appeared to indicate that these bonding systems are technique sensitive.

Cohen [1] , [2] has illustrated that extremely high Gamma-aminobutyric acid (GABA) levels in the urine and blood and high plasma ammonia were observed for an autistic male child diagnosed with infantile autism. GABA is a major inhibitory neurotransmitter of the mammalian brain and the enzyme responsible for catabolism is GABA-Transaminase (GABA-T). Elevated levels of ammonia in the plasma results in a decrease in the efficiency for the GABA-T enzyme and this results in higher GABA concentrations after regulation in the liver. It is postulated that a link between plasma ammonia and plasma GABA exists where the concentration of GABA in the plasma is directly related to the ammonia plasma concentration. A ratio of approximately 0.30 (plasma ammonia/GABA) is a consistent finding for normal subjects and for subjects with infantile autism and liver diseases such as hepatic encephalopathy.

This study compared the in vitro shear bond strength of an autopolymerizing composite resin system (CR) (Ti-Core) with two third-generation dentinal bonding agents (DBA) (Tenure and Scotchbond 2) to glass ionomer cements (GIC) (Ketac-Silver, GC Miracle Mix, and Ketac-Cem). The experiment was divided in five groups. The shear bond strengths were evaluated on a universal testing apparatus at three different intervals; 15 minutes, 24 hours, and 7 days. Statistically, (twoway analysis of variance), the shear bond strengths from the greatest to least were: Ti-Core CR with Tenure DBA > Ti-Core CR with Scotchbond 2 DBA > Ketac-Silver GIC, GC Miracle Mix GIC > Ketac-Cem GIC. There were no differences in shear bond strengths according to time, and no interactions between groups and time. The shear bond strengths for Tenure DBA with Ti-Core CR were two and a half to three times greater than the silver-filled glass ionomers, KetacSilver GIC and GC Miracle Mix GIC. Tenure DBA with Ti-Core CR also had consistently greater shear bond strengths than Scotchbond 2 DBA with Ti-Core CR, and this trend is in agreement with similar research.

The retention of the post to the root of an endodontically treated tooth is critical for a successful restoration. Modification of the post length to accommodate a specific clinical situation is common. This study compared the retention of No. 1 and No. 2 Flexi-Post restorations shortened apically from 1 to 5 mm with that reported for full-length control No. 1 and No. 2 Flexi-Post dowels. The experimental material was divided into 10 groups with 10 samples in each group. Retentive values were recorded in pounds with a universal testing machine. Analysis of variance with a Tukey-Student range, multiple-comparison test showed no statistical differences from apical reductions of 1, 2, 3, and 5 mm including the full-length control FlexiPost No. 1 system. With 4 mm of apical shortening statistically greater retention was recorded. No statistical differences resulted with apical reductions of 1 to 4 mm or with the full-length control Flexi-Post No. 2 system, but 5 mm of apical shortening caused significantly less retention.

This study determined whether cold treatment at -96 degrees C affected the mechanical properties of different compositions and sizes of Flexi-Post systems, various sizes of dental reamers, and external wrenches. The experiment was divided into eight groups. The four control groups were untreated and consisted of (1) 50 stainless steel posts, (2) 40 titanium posts, (3) 50 stainless steel reamers, and (4) 10 stainless steel external wrenches. The four experimental groups were cold treated once and twice and included (1) 100 stainless steel posts, (2) 80 titanium posts, (3) 100 stainless steel reamers, and (4) 20 stainless steel external wrenches. The bending or breaking forces were tested on a universal testing machine. Stainless steel Flexi-Post dowels, stainless steel reamers, and external wrenches all showed a significant (ANOVA) (p < 0.05) increase in strength as a result of the single and double cold treatment. Titanium posts showed no strength increase following a single cold treatment, while they were weakened by a double cold treatment.

This study determined whether cold treatment at -96 degrees C affected the mechanical properties of various compositions and sizes of the Flexi-Post system. The experiment was divided into four groups of posts. The two control groups were made up of untreated stainless steel (50 posts) and titanium alloy (40 posts). The two remaining cold-treated groups were made up of stainless steel (50 posts) and titanium alloy (40 posts). In each instance the bending or breaking forces were tested on a universal testing machine. Stainless steel Flexi-Post samples showed a significant (p less than 0.05) increase in strength, whereas titanium alloy posts showed no significant increase in strength as a consequence of the cold treatment.