The influence of zirconia coping designs on maximum principal stress distribution in all-ceramic premolar crowns: A finite element analysis.

PURPOSE: To evaluate the effects of different coping designs on maximum principal stresses in the veneering material using a finite element analysis method. METHODS: A maxillary first premolar tooth model was prepared. The primary and prepared tooth model were scanned with a 3D (three dimensional) scanner. Four different coping and veneer models were designed with 3D computer-aided design software: conventional design (DC); design with 3 mm palatal shoulder (DP); design with 1 mm buccal shoulder and 3 mm palatal shoulder (DB); and design with buccal facet (DF). After the models were designed, they were transferred to the finite element analysis (FEA) software for analyses. The middle points of the buccal, mesial, distal and palatal surfaces were determined in the cervical region. For all models, the maximum principal stress distributions and values of porcelain veneer were evaluated under centric occlusion loading and laterotrusive loading conditions with a FEA. RESULTS: The maximum principal stress area decreased gradually from model DC to model DB on the buccal cervical region under centric occlusion loading. However, models DF and DP showed similar stress distribution. The maximum principal stress at the distal point decreased from DC (14.7 MPa) to DP (13.5 MPa) and DB (9.6 MPa), whereas increased in model DF (33 MPa). Under laterotrusive loading, both the palatal maximum principal stress area and the stress value at the palatal point (model DC: 13.1 MPa, model DP: 3 MPa, model DB: 4MPa) decreased with the palatal shoulder. CLINICAL SIGNIFICANCE: Increasing the height of the palatal shoulder may be a practical and efficient approach to reduce the maximum principal stress in all-ceramic crowns. Thus, the clinical failure as chipping in the all-ceramic crowns may be reduced.

Effect of different surface-cleaning techniques on the bond strength of composite resin restorations.

STATEMENT OF PROBLEM: Different techniques have been suggested for cleaning dentin surfaces after the removal of an interim prosthesis and before the application of a bonding agent. How different surface-cleaning techniques affect the bond strength of the composite resin restorations is not clear. PURPOSE: The purpose of this study was to investigate the effects of different surface-cleaning techniques on the bond strength of composite resin restorations and the surface topography of the prepared tooth surfaces. MATERIAL AND METHODS: The occlusal surfaces of 25 molars were ground until the dentin was exposed. A bonding agent and interim cement were applied on the teeth. The teeth were divided into 5 groups (n=5) according to the method used for surface-cleaning (microairborne-particle abrasion, alcohol, rubber-rotary instrument, desiccating agent, and control). Once the surfaces of the teeth had been cleaned, the same bonding material was applied to the teeth. A 5-mm-thick composite resin layer was built up. Each specimen was sectioned to microbars, and 6 centrally located beams were selected for microtensile testing (n=30) (1.10 ±0.10 mm). The data were statistically analyzed with 1-way ANOVA (1-sample Kolmogorov-Smirnov test). The Bonferroni test was used for significantly different groups (α=.05). One specimen from each group was observed under a scanning electron microscope and an atomic force microscope. Energy dispersive x-ray analysis also was performed. RESULTS: Bond strength values were in the following descending order: microairborne-particle abrasion, desiccating agent, alcohol, rubber-rotary instrument, control. Differences between the microairborne-particle abrasion group and the remainder of the groups, desiccating agent--rubber-rotary instrument, desiccating agent-control, alcohol--rubber-rotary instrument, and alcohol-control groups, were statistically significant (P<.05). The microairborne-particle abrasion group displayed the roughest surface and a different surface topography from the remainder of the groups. Increased aluminum was observed in the microairborne-particle abrasion group. CONCLUSIONS: Surface-cleaning techniques, except for the rubber-rotary instrument, increased the bond strength of composite resin. The roughest dentin surfaces and highest bond strength were achieved with the microairborne-particle abrasion technique.

A clinical comparison of cordless and conventional displacement systems regarding clinical performance and impression quality.

STATEMENT OF PROBLEM: It is not clear whether newly introduced cordless displacement systems are better able to manage gingiva than conventional systems. PURPOSE: The purpose of this in vivo study was to evaluate the gingival management ability of 4 different displacement methods with a standardized subgingival preparation finish line. MATERIAL AND METHODS: The effects of 4 displacement techniques on gingival management and impression quality were evaluated by means of 6 evaluation criteria. A subgingival preparation finish line of between 1 and 2 mm was ensured, and the buccal aspects of 252 (n=63) teeth were clinically assessed for ease of application, time spent, bleeding, remnants, and dilatation. The complete reproduction of the preparation finish line and the bubble and void formations on polyether impressions were also evaluated. The data were statistically analyzed with the χ(2) test (α=.05). The Bonferroni correction was used to control Type I error for the pairwise comparison groups (α=.008). RESULTS: Statistically significant differences were found for all criteria among the groups (P<.05). The nonimpregnated displacement cord group was the least effective group in terms of bleeding and impression quality (P<.008). The aluminum chloride impregnated cord group and the displacement paste with cap group were found to be comparable in terms of remnants, dilatation, and impression quality (P>.008). The retraction cap with paste group showed better results for ease of application, time spent, and bleeding than the aluminum chloride impregnated cord group (P<.008). Although the group with aluminum chloride impregnated cord, displacement paste, and cap showed better results for dilatation, it was time consuming and difficult (P<.008). CONCLUSIONS: Except for the nonimpregnated cord group, all of the groups were comparable and clinically useful, with perfect or acceptable impression qualities.

Surface detail reproduction under simulated pulpal pressure: a 3-dimensional optical profilometer and scanning electron microscopy evaluation.

STATEMENT OF PROBLEM: It is not clear whether more hydrophilic impression materials are better able to copy and transfer dentin surface detail than less hydrophilic ones. PURPOSE: The purpose of this study was to evaluate the reproduction of dentin surface detail by means of hydrophobic and hydrophilic elastomeric impression materials under simulated pulpal pressure and their ability to transfer surface detail onto casts produced from such impressions. MATERIAL AND METHODS: The wettability of the impression materials (n=8) was determined by contact angle measurement with an evolution period of 135 seconds. Dentin moisture was provided by means of pulpal pressure simulation, and objective analyses were performed by measuring the average roughness value (Ra) with a 3-D optical profilometer (n=10). One specimen from each group was analyzed with scanning electron microscopy. Contact-angle values were analyzed with a repeated measures ANOVA, and detail reproduction was tested with 3-way ANOVA (α=.05). The Bonferroni correction was used to control Type I error for follow-up analyses. RESULTS: Contact angle measurements revealed significant differences depending on the impression material used and time of the measurement (P<.001). The Ra values of the hydrophilic impression materials, which were made from dry specimens, and the pulpal pressure simulated dentin surfaces did not differ from the dentin surfaces (P>.013). The hydrophobic impression material showed similar detail reproduction ability in a dry field, but loss of detail (evaluated subjectively) and increased roughness values (evaluated objectively) were recorded in a moisturized field (P=.004). Polyurethane-based cast material successfully reproduced the surface texture (P≥.006), whereas Type IV gypsum material was unable to reproduce this texture to the same extent. CONCLUSIONS: The hydrophilic impression materials tested showed similar ability to reproduce detail under simulated pulpal pressure. Polyurethane-based cast material successfully reproduced the surface texture.

Management of interproximal soft tissue with a resin-bonded prosthesis after immediate implant placement: a clinical report.

This report describes immediate implant placement after the extraction of a vertically fractured tooth. During the healing phase, a resin-bonded prosthesis was inserted as a provisional restoration. After the creation of the optimal emergence profile and papillae with the provisional restoration, the definitive metal ceramic crown was fabricated.

Repositioning a prosthetically unfavorable implant by vertical distraction osteogenesis.

Prosthetically unfavorable implant positions challenge patients and restorative dentists. Surgical correction of malpositioned implants may be an alternative technique for esthetically and biomechanically acceptable prosthetic restorations. This case report describes an alveolar distraction technique used to coronally reposition a dental implant and the 3-year results in the maintenance phase. To our knowledge, long-term follow-up of this method of correction is unprecedented. The present case report describes the repositioning of an apically positioned and fully osseointegrated implant at the right maxillary canine region using an alveolar distraction technique. Distraction was performed at 1 mm per day and ended when the implant moved 6 mm coronally. After a consolidation phase of 8 weeks, an implant-supported fixed prosthetic restoration was performed. Healing was uneventful after removal of the distractor. During the 3-year follow-up, the implant was fully functional with minimal probing depths, negligible signs of inflammation, and no further bone loss. This intervention illustrates the promise of an alveolar distraction osteogenesis procedure for vertical repositioning of apically positioned implants. This technique also provided soft and hard tissue remodeling to obtain an esthetic and stable restoration.

Effect of sodium ascorbate on bond strength of different adhesive systems to NaOCl-treated dentin.

The aim of this study was to evaluate the effects of sodium ascorbate on bond strength of different adhesive systems to NaOCl-treated dentin. Eighty extracted molar teeth were used in the study. The buccal enamel surfaces were removed to obtain a flat dentin surface. The teeth were mounted in self-curing resin and dentin surfaces were irrigated with NaOCl for 10 min. Half of the specimens were treated with sodium ascorbate for 10 min. The teeth were randomly assigned to four subgroups according to the adhesive systems used (Clearfil SE Bond, Clearfil Tri-S Bond, Adper Prompt-L-Pop, Adper Single Bond 2). Bond strengths were determined with a Universal Testing Machine, at a crosshead speed of 0.5 mm/min. Data were statistically analysed using anova at a significance level of 0.05. Two-way ANOVA revealed that the effect of sodium ascorbate application on bond strength of adhesive systems to NaOCl-treated dentin was statistically significant (P < 0.05). The bond strength results were significantly influenced by the application of sodium ascorbate (P < 0.05) and there was a significant difference between the adhesive systems (P < 0.05). Although statistically significant differences were not demonstrated in all adhesive resin groups, sodium ascorbate application after NaOCl treatment improved the bond strength values.

Effect of laser irradiation and cavity disinfectant application on the microtensile bond strength of different adhesive systems.

OBJECTIVE: The aim of this study was to evaluate the effect of two different cavity disinfection procedures (chlorhexidine gluconate-based cavity disinfectant and Er,Cr:YSGG laser irradiation) on the bond strength of two different types of adhesive systems (Adper Single Bond 2 [SB] and Clearfil SE Bond [SE]). MATERIALS AND METHODS: Thirty human third molars were ground flat to expose midcoronal dentin. After the dentin surfaces were polished with 600-grit silicon carbide paper, the teeth were randomly assigned to six groups (n = 5) according to the cavity disinfection procedure and the adhesive resin: Group I, etch and rinse adhesive (SB); Group II, self-etch adhesive (SE); Group III, cavity disinfectant application (cavity cleanser) + SB; Group IV, cavity disinfectant application + SE; Group V, laser irradiation (Er,Cr:YSGG laser, 20 Hz; 0.75 W; 15% water, 15% air) + SB; Group VI, laser irradiation + SE. For each group, the composite crown was incrementally fabricated with a composite resin. Following storage in distilled water at 37 degrees C for 24 h, the bonded specimens were serially sectioned into rectangular beams (n = 32). Bond strengths were determined using a microtensile tester at a crosshead speed of 0.5 mm/min. Data were analyzed using two-way ANOVA, and multiple comparisons were performed using post hoc Duncan's test (p < 0.05). RESULTS: Cavity disinfectant application and laser irradiation produced significantly higher bond strength values compared to the control group for SB. For SE, only laser irradiation improved the bond strength values compared to the control. There was a statistically significant decrease in the bond strength values of the specimens that were subjected to cavity disinfectant before SE application. The failure mode was mainly adhesive in all groups. CONCLUSION: Cavity disinfectant application and laser irradiation may influence bond strength, depending on the adhesive system used. As a cavity-disinfecting procedure, laser irradiation might enhance the bond strength of etch and rinse and self-etch adhesive systems.

Effect of bleaching on staining susceptibility of resin composite restorative materials.

STATEMENT OF THE PROBLEM: Effect of bleaching procedures on staining susceptibility of resin restorative materials is still questionable. PURPOSE: The aim of this study was to evaluate the staining susceptibility of restorative materials bleached with 20% carbamide peroxide home bleaching agent and subsequently immersed in coffee and tea. MATERIALS AND METHODS: Forty-two disk-shaped specimens were fabricated for each of the resin composites (Filtek Supreme XT [3M ESPE, St. Paul, MN, USA], Ceram-X Mono [Dentsply, Konstanz, Germany], and Aelite All Purpose Body [BISCO, Inc., Shaumburg, IL, USA]). The baseline color values were measured with a spectrophotometer. The specimens of each restorative material were randomly divided into two groups (N = 21). While the first group specimens were stored in distilled water (nonbleaching group-control), bleaching agent (Opalescence PF 20% [Ultradent Poducts, South Jordan, UT, USA]) was applied on the top surface of each specimen of the second group (bleaching group). After color change values were measured, the specimens were randomly divided into three subgroups (N = 7) according to the staining solutions. The color change values (DeltaE*ab) were calculated and the data were subjected to analysis of variance. Statistical significance was declared if the p value was 0.05 or less. RESULTS: There was no statistically significant difference within each restorative material's DeltaE*ab values after bleaching (p = 0.714). Also, the staining solutions did not cause a statistically significant difference between DeltaE*ab values of bleaching compared with nonbleaching groups (p = 0.146). Significant interaction was found only between restorative materials and staining solutions (p = 0.000). CONCLUSION: Bleaching of the tested resin composites did not increase their susceptibility to extrinsic staining in vitro. CLINICAL SIGNIFICANCE Bleaching did not affect staining susceptibility of the tested resin composite restorative materials. (J Esthet Restor Dent 21:407-415, 2009).

The effects of extraoral porcelain polishing sequences on surface roughness and color of feldspathic porcelain.

The aim of this study was to evaluate the surface properties and color of porcelain modified by extraoral polishing sequences. Six different surface treatment regimens (diamond burs, self-glaze, overglaze, reglaze, Pearl Surface polishing system, and Diamond Twist SCL) were applied to 60 porcelain disks (n = 10 per group). Profilometry and atomic force microscopy (AFM) were used for the determination of surface roughness (Ra); color changes (deltaE*) were investigated by spectrophotometry. Statistical comparisons were made using analysis of variance, the Kruskal-Wallis test, and the Pearson correlation coefficient test. Surface treatments significantly affected Ra values (P < .001) but had no effect on color (P > .05). AFM findings were consistent with Ra values. Color did not appear to be correlated with surface roughness (P > .05). The findings concluded that the Pearl Surface system helps to decrease chairside time and may be used as an alternative to overglazing.

Microleakage in overflared root canals restored with different fiber reinforced dowels.

This study evaluated microleakage in overflared root canals restored with four different types of adhesively-luted fiber-reinforced dowels: DT Light Post (LP), Glassix (GL), Ribbond (RB) and StickTech Post (ST). Forty non-carious, single-rooted mandibular human premolars with straight root canals were prepared using a step-back technique and obturated with gutta-percha using lateral condensation. The restored roots were randomly divided into four groups (n=10). The root canals were overprepared, creating an overflared dowel space, and each dowel was adhesively luted using a total-etched adhesive (Single Bond) and dual-polymerizing luting agent (RelyX ARC). All specimens were thermal cycled 1000 times between 5 degrees C and 55 degrees C and stored in 2% methylene-blue solution for one week. The teeth were cut horizontally into three consecutive sections: apical (A), middle (M) and coronal (C). Each section was digitally photographed from the occlusal direction under a stereomicroscope. The images were transferred to a PC and stored in TIFF format. For each image, dye penetration was estimated as the ratio of methylene-blue-infiltrated surface divided by total dentin surfaces. The data were compared and statistically analyzed using the Kruskal-Wallis test (p<.05). The Mann-Whitney U test was used to compute multiple pairwise comparisons to determine differences between the experimental groups (p=.083). Dentin-luting agent fiber-reinforced dowel (FRD) interfaces were evaluated under a scanning electron microscope. Scanning electron microscopy (SEM) showed detachment of the luting resin from the dentin surface in varying degrees in all specimens evaluated. All groups showed considerable leakage at the sections evaluated. Significant differences were demonstrated between LP-RB for the apical and middle sections and between GL-RB, LP-RB and ST-RB for the coronal sections (p<.0083). Among the FRDs evaluated, the individually shaped polyethylene-reinforced dowel (Ribbond) showed the least overall leakage.

Effects of mouth rinses on color stability of resin composites.

OBJECTIVES: The aim of this study was to evaluate the effects of 3 commercially available mouth rinses on the color stability of 4 different resin-based composite restorative materials. METHODS: Forty disc-shaped specimens (10x2 mm) were prepared from each of the following materials: A nanofill composite Filtek Supreme XT (3M/Espe, St. Paul, MN, USA); a packable low-shrinkage composite, AeliteLS Packable (BISCO, Inc, Shaumburg, IL, USA); nanoceramic composite resin Ceram-X (Dentsply, Konstanz, Germany); a microhybrid composite, and Aelite All-Purpose Body (BISCO). The specimens were then incubated in distilled water at 37 degrees C for 24 hours. The baseline color values (L*, a*, b*) of each specimen were measured with a colorimeter according to the CIELAB color scale. After baseline color measurements, 10 randomly selected specimens from each group were immersed in 1 of the 3 mouth rinses and distilled water as control. The specimens were stored in 20 mL of each mouth rinse (Oral B Alcohol-free, Listerine Tooth Defense Anti-cavity Fluoride Rinse and Klorhex) for 12 hours. After immersion, the color values of all specimens were remeasured, and the color change value DeltaE*ab was calculated. Data were analyzed using a 2-way analysis of variance at a significance level of .05. RESULTS: All specimens displayed color changes after immersion, and there was a statistically significant difference among restorative materials and mouth rinses (P<.05); however, the change was not visually perceptible (DeltaE*ab<3.3). The interaction between the effect of mouth rinses and type of restorative materials was not statistically significant (P>.05). CONCLUSIONS: It may be concluded that although visually nonperceptible, all resin restorative materials tested showed a color difference after immersion in different mouth rinses.

Forced eruption and implant treatment in posterior maxilla: a clinical report.

Periodontal disease can result in bone defects that surround periodontally compromised teeth. After the loss of those teeth, remaining defects may compromise successful treatment with dental implants. Forced eruption, induced by applying light orthodontic forces in the coronal direction, provides enhancement of the implant recipient site by enabling the extraction of the periodontally hopeless teeth. This report describes the use of forced eruption to promote the formation of new bone and soft tissue in the resorbed maxillary posterior region, followed by placement of an implant-supported fixed partial denture.

Influence of previous provisional cementation on the bond strength between two definitive resin-based luting and dentin bonding agents and human dentin.

This study evaluated the effect of two different types of provisional luting agents (RelyX Temp E, eugenol-based; RelyX Temp NE, eugenol-free) on the shear bond strengths between human dentin and two different resin-based luting systems (RelyXARC-Single Bond and Duo Link-One Step) after cementation with two different techniques (dual bonding and conventional technique). One hundred human molars were trimmed parallel to the original long axis, to expose flat dentin surfaces, and were divided into three groups. After related surface treatments for each specimen, the resin-based luting agent was applied in a silicone cylindrical mold (3.5 x 4 mm), placed on the bonding-agent-treated dentin surfaces and polymerized. In the control group (n = 20), the specimens were further divided into two groups (n = 10), and two different resin-based luting systems were immediately applied following the manufacturer's protocols: RelyX ARC-Single Bond (Group I C) and Duo Link-One Step (Group II C). In the provisionalization group (n = 40), the specimens were further divided into four subgroups of 10 specimens each (Group I N, I E and Group II N, II E). In Groups I N and II N, eugenol-free (RelyX NE), and in groups I E and II E, eugenol-based (RelyX E) provisional luting agents (PLA), were applied on the dentin surface. The dentin surfaces were cleaned with a flour-free pumice, and the resin-based luting systems RelyX ARC (Group I N and E) and Duo Link (Group II N and E) were applied. In the Dual bonding groups (n = 40), the specimens were divided into four subgroups of 10 specimens each (Group I ND, ED and Group II ND, ED). The specimens were treated with Single Bond (Groups I ND and ED) or One Step (Groups II ND and ED). After the dentin bonding agent treatment, RelyX Temp NE was applied to Groups I ND and II ND, and RelyX Temp E was applied to Groups I ED and II ED. The dentin surfaces were then cleaned as described in the provisionalization group, and the resin-based luting systems were applied: RelyX ARC-Single Bond (Group I ND and ED) and Duo Link-One Step (Group II ND and ED). After 1,000 thermal cycles between 5 degrees C and 55 degrees C, shear bond testing was conducted at a crosshead speed of 0.5 mm/minutes. One-way ANOVA, followed by a post hoc Tukey test (alpha = 0.05) was done. The dentin-resin-based luting system interfaces were evaluated under a scanning electron microscope. There was a significant reduction in the mean shear bond strength values of groups subjected to the provisionalization compared to the control and dual bonding technique groups (p < 0.05). The composition of provisional luting did not create a significant difference with regard to reducing shear bond strength values (p > 0.05). With regard to resin based luting systems, the shear bond strength values of the double-bond technique groups were not significantly different from the controls (p > 0.05).

Modification of glass fibers to improve reinforcement: a plasma polymerization technique.

OBJECTIVES: This study evaluates the effect of plasma treated E-glass fiber to improve the mechanical properties of acrylic resin denture base material, polymethylmethacrlyate (PMMA). Plasma surface treatment of fibers is used as reinforcement in composite materials to modify the chemical and physical properties of their surfaces with tailored fiber-matrix bonding strength. METHODS: Three different types of monomer 2-hydroxyethyl methacrylate (HEMA), triethyleneglycoldimethylether (TEGDME) and ethylenediamine (EDA) were used in the plasma polymerization modification of glass fibers. A radiofrequency generator was used to sustain plasma in a glass vacuum chamber. Glass fibers were modified at the same glow-discharge power of 25 W and exposure time of 30 min for each monomer. Fibers were incorporated into the acrylic with 1% (w/w) loading except control group. Specimens were prepared using a standard mold of 3 cmx0.5 cmx0.8 cm in dimension with eight specimens in each group. Samples were subjected to a flexural strength test set up at a crosshead speed of 5mm/min. Scanning electron microscopy (SEM) was used to examine the microstructure and X-ray photoelectron spectroscopy (XPS) was used for chemical analysis of the surface. RESULTS: Data were analyzed by means of ANOVA and Duncan's tests. Test results revealed that fiber reinforcement had a significant effect on the flexural strength of the specimens (p<0.05). Among the fiber reinforced groups, plasma treatment with EDA monomer resulted in the most significant increase in flexural strength values (p<0.05). XPS results have shown an increasing number of nitrogenous compounds in EDA treated fibers. The chemical structure of the surface, especially with the increase in nitrogenous compounds could give an idea for the amine film deposition and SEM figures showed an increase in surface roughness. SIGNIFICANCE: The results showed that plasma treatment with EDA monomer was an effective alternative method of increasing the flexural strength of PMMA based denture base polymers through fiber reinforcement.

An innovative approach to chairside provisional replacement of an extracted anterior tooth: use of fiber-reinforced ribbon-composites and a natural tooth.

Immediate chairside replacement of an extracted anterior tooth may contribute to a patient's comfort, treatment acceptance, and expectations of treatment; however, fabrication of a custom restoration in the anterior region of the mouth may result in an esthetic compromise for patients during the fabrication period. Chairside tooth replacement is an excellent application of fiber-reinforced composite resin technology. This article presents an innovative, affordable chairside procedure in which Ribbond Multi-Purpose Bondable Reinforcement Ribbon is used to replace a single extracted anterior tooth using the patient's own tooth.

Alveolar distraction osteogenesis and implant placement in a severely resorbed maxilla: a clinical report.

Atrophy of maxillary alveolar bone can result in severe defects of the alveolar ridge. Such defects can make it difficult to achieve esthetic and functional restorations. This clinical report describes the use of alveolar distraction osteogenesis to promote the formation of new bone and soft tissue in a large, severely resorbed segment of maxillary alveolus.

Effects of glow-discharge and surfactant treatments on the wettability of vinyl polysiloxane impression materials.

STATEMENT OF PROBLEM: Although surfactant-modified vinyl polysiloxane (VPS) is described as hydrophilic by manufacturers, interaction with dental gypsum is relatively poor. PURPOSE: The purpose of this study was to compare and evaluate the wettability of surfactant-modified VPS after different surface treatments. MATERIAL AND METHODS: Eighty-four impression-material specimens (20 x 10 x 1 mm) were prepared from 3 different brands of VPS (Aquasil, Panasil Contact Plus, and Accuflex). Four groups (n = 7) of specimens were established according to the surface treatment method used: no treatment, topical application of 2 different surface wettability agents (Silwet Copolymer L-77 or Delar surfactant), or coating with an acrylic acid plasma in a glow-discharge reactor. Plasma treatment specimens were coated with acrylic acid in a glow-discharge system at a radio frequency of 13.56 MHz with 20-W discharge power and 5 minutes of exposure time. Wettability was measured using the contact-angle method. Values were recorded after the drop contacted the surface at 0.6 second, 30.7 seconds, and 210.8 seconds. Contact-angle mean values were compared using 3-way analysis of variance with repeated measures on 1 factor, followed by a post hoc Duncan test (alpha=.05). RESULTS: As the sphericity assumption was not satisfied, the Greenhouse-Geisser correction was used for contact-angle values. Glow-discharge treatment proved to be effective for increasing the surface energy of the VPS compared to controls at all time points studied (P <.0001). At 0.6 second, Silwet significantly decreased the contact-angle values for Aquasil and for Panasil Contact Plus (P <.0001). Delar treatment, at this time point, significantly increased the contact-angle values of GC (P <.0001) and decreased the contact-angle values of Aquasil (P <.0001). At 30.7 seconds, Silwet significantly increased the wettability of Aquasil and Panasil Contact Plus ( P <.0001) but did not significantly increase the wettability of GC. Delar treatment, at 30.7 seconds, increased the contact-angle values of GC (P <.0001), whereas contact-angle values of Aquasil significantly decreased (P <.0001). At 210.8 seconds, all surface-modification methods used were effective in increasing the wettability of VPS tested over untreated controls (P <.0001). CONCLUSION: Wettability of VPS-based impression materials can be increased by coating the surface with acrylic acid in a glow-discharge reactor. The change in wettability achieved by the application of topical surfactants resulted in variations among surfactant-VPS combinations.

A technique for restoring an overflared root canal in an anterior tooth.

This article describes a technique for fabricating a dowel and core for a tooth with an overflared root canal. The technique involves supporting a glass fiber-reinforced prefabricated dowel with chopped silanated glass fibers.