A comparison of root fracture resistance using two root canal sealers.

AIM: The aim of this study was to compare in vitro root fracture resistance following root canal filling with either Ketac-Endo or Roth's root canal sealer. METHODOLOGY: The roots of 40 teeth with single canals were instrumented and placed randomly into four groups of 10 teeth. The prepared canals were obturated with lateral compaction using gutta-percha and Roth's 801 sealer, lateral compaction and Ketac-Endo sealer or with a single cone and Ketac-Endo sealer; the fourth group acted as unfilled controls. The roots were stored for 2 weeks in 100% humidity prior to being mounted in acrylic resin blocks. A steel tipped rod attached to an Instron testing machine was positioned against the canal opening and a slowly increasing force was applied until root fracture occurred. The results were subjected to statistical analysis using Kruskal-Wallis one-way ANOVA. RESULTS: There were no significant differences between the groups in terms of force required to vertically fracture the roots. CONCLUSIONS: Under the conditions of this study, the use of Ketac-Endo sealer in conjunction with lateral compaction or single-cone obturation techniques does not increase the fracture resistance of root-filled teeth.

Disinfection of denture base acrylic resin.

STATEMENT OF PROBLEM: During repair or adjustments of acrylic resin removable complete and partial dentures, particles of the acrylic resin from the interior of the prosthesis may expose dental personnel to microbial health hazards if the prosthesis has not been thoroughly disinfected. PURPOSE: This study investigates the efficacy of a commercially prepared microbial disinfectant (Alcide) on the external and internal surfaces of acrylic resins. MATERIAL AND METHODS: Four groups of acrylic resin were incubated in an experimental model to simulate the oral environment over time. Specimens were treated in 2 groups, disinfected and not disinfected, and then further grouped by breaking and not breaking. Analysis was performed with microbial colony counts, SEM, and statistical analyses. RESULTS: Viable microorganisms still remain on the internal and external surfaces of treated resins. CONCLUSION: Chlorine dioxide reduces, but does not eliminate, viable microorganisms on these dental prostheses.

Photoelastic comparison of stress induced by using stainless-steel versus nickel-titanium spreaders in vitro.

The vertical force applied to an endodontic spreader generates stress along the canal walls. Recognizing the potential for this stress may reduce the incidence of vertical root fractures. A photoelastic acrylic model was fabricated to exhibit the stress produced during obturation of curved canals using the lateral condensation technique. Twenty standardized models simulating curved canals (32 degrees) were formed within PL-2 photoelastic acrylic resin blocks. The canals were fitted with a gutta-percha point, and either a stainless-steel or nickel-titanium finger spreader was inserted. An Instron 4502 universal testing machine applied a vertical force of 20 Newtons to the spreader. Quarter wave and polarizing filters were used with backlighting to generate the fringe patterns in the models. Photographs of the resulting stress lines showed that the stainless-steel spreaders created three areas of concentrated stress. The nickel-titanium spreaders induced stress patterns spread out along the surface of the canals, thus reducing the concentration of stress and the potential for vertical root fracture.

Nickel-titanium versus stainless-steel finger spreaders in curved canals.

Placement of endodontic spreaders to within 1 to 2 mm of the root canal working length has been advocated for optimum gutta-percha obturation. Due to their stiffness, stainless-steel (SS) spreaders will often fail to achieve this position in curved canals. Newly marketed nickel-titanium (NiTi) spreaders may offer an advantage in this regard due to the increased flexibility of these instruments. Seventy mesial and distal mandibular molar canals were instrumented to a #35 master apical file size. Measurements of the canal curvature were made from preoperative radiographs. Canal curvature angles ranged from 0 to 51 degrees. The teeth were placed in a radiographic mount to ensure a constant focal length, and postoperative radiographs were exposed with comparably sized SS and NiTi spreaders inserted into each prepared canal. Measurements of spreader tip to apex distance were made with a micrometer to the nearest 0.02 mm on the radiographs. Using a t test for paired samples, it was shown that NiTi spreaders penetrated to a significantly greater depth than SS spreaders in curved canals (p < 0.001).

Effectiveness of chlorine dioxide in disinfection on two soft denture liners.

STATEMENT OF PROBLEM: Soft tissue denture liners frequently require replacement that necessitates complete removal from the denture base. A high speed lathe located in a "clean laboratory" is often used to facilitate removal of these materials, but it is unclear whether routine disinfection procedures reduce bacterial contamination sufficiently to prevent contamination of the laboratory. PURPOSE: The first phase of this study evaluated the effectiveness of 3-minute chlorine dioxide spray and immersion disinfection procedures on 2 denture liners (Coe Soft and Coe Comfort) and stainless steel specimens used as controls. The second phase evaluated the effectiveness of spray disinfection at time intervals of 1, 3, and 10 minutes. MATERIAL AND METHODS: Specimens made of soft denture liners attached to acrylic resin bases (10 per group) were contaminated with Escherichia coli, Staphylococcus aureus, and Candida albicans. Colony-forming units were counted after different disinfection techniques were applied. Kruskal-Wallis 1-way analysis of variance on ranks and an all pairwise multiple comparison procedures (Dunn's method) were used to test for significant differences among test groups at the P <.05 level of significance. RESULTS: Chlorine dioxide was effective against nonporous stainless steel specimens but was inadequate for denture liners at the recommended 3-minute time of disinfection. The immersion technique was more effective than the spray technique, but the difference was not significant. Increasing the time of disinfection did not significantly reduce the numbers of microorganisms. CONCLUSION: Coe Soft and Coe Comfort denture liners should be removed before entering the laboratory. These materials contain sufficient viable bacteria after routine disinfection procedures to cause contamination of the "clean laboratory."

Interpretation of periapical lesions comparing conventional, direct digital, and telephonically transmitted radiographic images.

The purpose of this study was to evaluate direct digital radiography (DDR) and telephonically transmitted images versus conventional radiography in the interpretation of artificial periapical bone lesions. Five teeth were chosen from four cadaver jaw specimens. Three types of DDR images were evaluated: DDR stored images, DDR transmitted images, and DDR reversed images. A total of 150 DDR computer monitor images and 56 D-speed film images were evaluated by three endodontists and one endodontic graduate student. The Wilcoxon signed-ranks test was used for statistical analyses of the results. DDR reversed images were statistically inferior to DDR stored images, DDR transmitted images, and conventional radiography images (p < 0.0001). There were no statistically significant differences between DDR stored images, DDR transmitted images, and conventional film images in the ability of the evaluator to identify artificial periapical bone lesions (p > 0.05).

In vitro failure load of metal-collar margins compared with porcelain facial margins of metal-ceramic crowns.

PURPOSE: This in vitro study compared the load necessary to cause porcelain failure on traditionally fabricated metal-ceramic crowns cemented to metal tooth analogs with two different types of margins. MATERIAL AND METHODS: Metal-ceramic crowns were constructed with either metal facial collars or porcelain facial margins. The metal tooth analogs were embedded in polymethyl methacrylate resin blocks, so that a load applied to the lingual surface compressed the facial margins. Increasingly greater loads were applied to specimens until failure occurred and the failure load values of all specimens were statistically evaluated. RESULTS: The load required to cause porcelain fracture in the crowns with porcelain facial margins was statistically significantly greater than the load required to cause porcelain fracture for crowns with metal collars (p < 0.02).

The effect of primers and surface characteristics on the adhesion-in-peel force of silicone elastomers bonded to resin materials.

Facial prostheses, when used in conjunction with craniofacial implants, require a retentive matrix to hold attachments and/or magnets. The retentive matrix is usually fabricated with autopolymerizing acrylic resin or a visible light-polymerized resin. The purpose of this study was to compare the adhesion-in-peel force of a silicone adhesive to autopolymerizing polymethyl methacrylate and light-polymerizing urethane dimethacrylate gel with two surface textures: (1) pumice polish only or (2) pumice polish and bead retention, and two surface primers: (1) Dow Corning 1205 primer or (2) Dow Corning S-2260 primer. The 1205 primer produced an adhesion-in-peel force that was statistically significantly stronger (p < 0.05) regardless of which type of resin or surface preparation was used.

The effect of plasma-treated polyethylene fiber on the fracture strength of polymethyl methacrylate.

The effect of a plasma-treated polyethylene fiber on the fracture strength of polymethyl methacrylate was evaluated in this study. Sixteen treated and 16 untreated polymethyl methacrylate bars were tested by use of a three-point compression loading apparatus. Under the conditions of this experiment the treated bars showed a mean fracture strength of 12.56 MPa compared with 9.81 MPa for the untreated samples. In addition to the increased fracture strength, the treated bars also demonstrated resistance to crack propagation. The bars remained in one piece, held together throughout the compression loading by the polyethylene fiber. The clinical implication of these findings is a reduced incidence of fixed provisional restoration failure.

Vertical extrusion: literature review and report of a case.

To date, the scientific literature has documented, primarily, successful methods and techniques of treatment involving vertical extrusion. The purpose of this article is to review the literature and report on a case that demonstrates the multidisciplinary approach required to successfully manage a reversible complication involving the restoration of an adult maxillary central incisor that had sustained an oblique crown-root fracture.

Treatment for acute craniomandibular dysfunction symptoms in edentulous patients with unserviceable or no existing complete dentures.

This article describes techniques to make unserviceable complete dentures rapidly serviceable and to facilitate using them in the diagnosis and treatment of acute craniomandibular dysfunction symptoms in edentulous patients. A technique is described to make complete dentures rapidly in the event that the complete dentures cannot be made serviceable or the patient has no complete dentures. This technique uses the TRIAD visible light-cure system. Once the complete dentures are made, they can be used alone or in conjunction with an occlusal splint for the diagnosis and treatment of acute craniomandibular dysfunction symptoms.

Fluid absorbency of retraction cords after soaking in aluminum chloride solution.

Soaking retraction cord in an aluminum chloride solution before placing into gingival sulci does not lessen the cord's ability to absorb fluid. Black silk suture is clinically ineffective and should be replaced with a dark, size 0 impregnated retraction cord.