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Results for “Post and Core Technique”

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PubMed2004

Fiber-reinforced post and core adapted to a previous metal ceramic crown.

A technique to create a fiber-reinforced anatomic post and core adapted to an existing crown is described. This technique is performed with a quartz post adapted to root canal anatomy, using a core composite material. With this technique, a well-adapted anatomic post and core may be achieved in a clinical session.

Bicuspid↗
PubMed1986

Multiple cast post and cores for severely worn anterior teeth.

A technique has been presented to simplify the fabrication of multiple direct post and core patterns. When combined with techniques for indirect provisional restorations, this technique merely requires the fabrication of an additional plastic template to form the direct core patterns.

Acrylic Resins↗
PubMedDate not supplied

Post and core reconstruction for fixed prosthodontic restoration.

If the previous restorative therapy or dental caries has resulted in substantial loss of tooth structure, the abutment teeth for fixed prosthodontic restorations require a core reconstruction or a post and core. Small dentin defects can be restored with bonded cores; more extensive dentin defects that are often accompanied by previous endodontic treatment generally require additional support for the core material. A direct procedure with a bonded post is a viable treatment method. The decision to use either light-conducting all-ceramic zirconium or titanium as a post material depends on the aesthetic requirements present. The indications for a cast post and core as an indirect procedure for prosthodontic reconstructions appear to be decreasing. The learning objective of this article is to review the past and current post and core materials and techniques. Indications for core reconstruction with vital teeth and posts and cores for pulpless teeth are discussed.

Aged↗
PubMed1994

Post-and-core assemblies made with an accelerated pattern elimination technique.

PURPOSE: Accelerated pattern elimination has the potential for increasing productivity. This study evaluated the accelerated pattern elimination technique using three commonly used phosphate-bonded investments. MATERIALS AND METHODS: Part one of this study determined the mean time interval from start of mixing to the maximum exothermic setting reaction temperature for each investment. A chromel/alumel thermocouple was placed at the heat center of a methylcellulose lined casting ring, using wet or dry ring liner. Investments were vacuum mixed at the recommended ratio for the accelerated technique. Colloidal silica solution and ddH2O were combined at a 50:50 ratio to meet the manufacturer's recommended liquid volume. Part two determined the dimensional reproduction of a standardized pattern and its casting using both casting techniques. Mixing ratios were the same as in part one for the accelerated technique and 75% colloidal silica to 25% double-distilled water (ddH2O) for the conventional technique. The accelerated technique used the mean setting time established in part one followed by a 15-minute furnace holding time at 725 degrees C (1350 degrees F). The conventional technique used a 1-hour bench setting time, followed by placing the mold into a cold furnace. A controlled rate of climb to a maximum temperature of 725 degrees C (1350 degrees F) was used with a 1-hour soak time. Each pattern and its casting were measured at four sites: (1) Length of the post-and-core assembly, (2) maximum core diameter, (3) post diameter at the core base, and (4) post diameter at its apex. RESULTS: A significant difference was found between the time interval to maximum exothermic setting reaction temperature for all the investments (P < .01). The accelerated technique produced castings with a relative dimensional increase of 0.11% to 4.80%. The conventional technique ranged from a 0.04% decrease in size to an increase of 3.65%. Castings made with the accelerated technique were significantly different than those made with the conventional technique (P < .01). CONCLUSIONS: Differences in the time interval to maximum exothermic setting reaction temperature indicate that each phosphate investment should have a recommended setting time before introduction into the furnace. The carbon-containing investment showed the least relative change of the three investments evaluated for both casting techniques.

Analysis of Variance↗
PubMed1984

An in vitro comparison of two dowel and core techniques for endodontically treated molars.

A laboratory study was designed to compare the shear-compressive strength of two post and core systems in mandibular molars. A buildup with cemented posts and an amalgam core proved to have greater strength than a system in which only amalgam was used to create a dowel and core. The addition of crowns to the buildups did not produce a significant increase in the shear strength of the specimens. Most specimens prepared by a specific restorative technique fractured in a consistent predictable pattern. The dentist should be aware of the incidence of lingual wall fractures in planning the restorations for endodontically treated molars. Careful evaluation of the remaining amount of tooth structure should influence the selection of the dowel and core technique.

Crowns↗
PubMed2002

Corono-radicular reconstruction of pulpless teeth: a mechanical study using finite element analysis.

STATEMENT OF PROBLEM: Following endodontic therapy, teeth need to be protected, particularly in the cervical region, where the majority of fractures occur. The likelihood of a fracture depends on the condition of the crown and the type of reconstruction performed. PURPOSE: This simulation study was designed to compare the effect of different corono-radicular reconstruction methods on stress transmission to dental tissues. MATERIAL AND METHODS: The study software performed stress analysis of complex structures by finite element analysis. Seven 3-dimensional models were created, each representing a tooth embedded in a bony medium. The following parameters affecting corono-radicular restoration were studied: 2 levels of coronal destruction, core materials, post materials when present, and absence of post. The 2 levels of coronal tissue loss were (1) total tissue loss of the coronal dentin and (2) partial tissue loss of the coronal dentin with 2-mm surviving dentin walls. Teeth with 2 different levels of tissue loss (first study parameter) were reconstructed by 4 different techniques: nickel chromium (NiCr) cast post and core, NiCr post and composite core combination, carbon fiber post and composite core combination, and composite restoration without post. A NiCr crown covered each of the models and received a 30 degrees oblique occlusal load at a constant intensity of 100 N. The software computed the stresses (local tensile stress inducing cracks and compressive stress) for each of the models, comparing maximum intensity observed, localization, and concentration. RESULTS: Whatever the type of stress (tensile or compressive), the greatest stress was observed in the cervical region, regardless of the model. Only tensile stresses potentially responsible for fractures were compared. Cervical tensile stresses exceeded 230 Pa in the absence of a ferrule and were less than 140 Pa when a ferrule was present. In the absence of a ferrule, the NiCr composite/post combination generated greater cervical stress (254 Pa) than the cast post and core (235 Pa). Results with a ferrule showed 92 Pa for the NiCr composite/post combination and 90.5 Pa for the cast post and core. In the presence of a ferrule, the tensile stress intensities generated by the composite restoration with no root canal post (139 Pa) were 51% greater than those generated by the NiCr/composite combination and approximately 26% greater than those generated by the composite/carbon combination. CONCLUSION: Within the limitations of this study, it was confirmed that all simulated reconstructed teeth were more subject to stress in the cervical region. The absence of a cervical ferrule was found to be a determining negative factor, giving rise to considerably higher stress levels. When no ferrule was present, the NiCr post/composite combination generated greater cervical stress than cast post and cores. Nevertheless, the peripheral ferrule seemed to cancel the mechanical effect of the reconstruction material on the intensity of the stresses. With a ferrule, the choice of reconstruction material had no impact on the level of cervical stress. The root canal post, the purpose of which is to protect the cervical region, was also shown to be beneficial even with sufficient residual coronal dentin. In the presence of a root canal post, cervical stress levels were lower than when no root canal post was present. Moreover, the higher the elasticity modulus, the lower the stress levels.

Carbon↗
PubMed2002

Indirect fabrication of multiple post-and-core patterns with a vinyl polysiloxane matrix.

In the described technique, a vinyl polysiloxane material is used as a matrix for the indirect fabrication of multiple custom-cast posts and cores. The matrix technique enables the clinician to fabricate multiple posts and cores in a short period of time. The form, harmony, and common axis of preparation for all cores are well controlled before the definitive crown/fixed partial denture restorations are fabricated. Oral tissues are not exposed to the heat of polymerization or the excess monomer of the resin material when this technique is used.

Acrylic Resins↗
PubMed1984

The effect of a corrugated channel on the retentive properties of an obturator-reinforced composite resin dowel-core system.

A study was conducted to compare the retentive properties of the obturator-reinforced composite resin dowel and core systems with and without corrugated dentin surfaces in the dowel channels. A commercially available tap with a diameter of about 1.4 mm and a thread groove depth of 100 micron was used to accomplish this dentin roughening. To compare whether methods of placement affect the retentive capacities of this dowel and core system, a Lentulo spiral, Jiffy tube, and Centrix C-R syringe were used to insert the resin mixes into the corrugated channels. The following conclusions can be drawn. By corrugating or roughening the dentin surface of the prepared channel, the retentive properties of this dowel and core system are significantly increased. In this system using minimal amounts of composite resin, the three methods of placement exhibited no significant difference in retention. The retentive failure seemed to occur at the resin-tooth interface. Increasing the degree of corrugation (deeper grooves) increased the retention, but caution must be exercised to prevent weakening the tooth.

Crowns↗
PubMed1997

The behaviour of post-retained core materials supported by coronal tooth structure in vitro.

This study was designed to investigate the effect of retaining coronal tooth substance on the performance of post-retained core materials, and to compare the fracture resistance of the system with an intact tooth prepared to similar dimensions. Ten teeth restored with post-retained silver amalgam, and 10 teeth restored with silver-glass cermet, all with a retained single wall of coronal tooth substance, were compared with 10 unrestored teeth prepared to similar dimensions when subjected to a shearing load. The results showed no statistically significant difference between the unrestored teeth and those restored with a silver-glass cermet. Whilst the teeth restored with silver amalgam had a significantly higher fracture resistance (P > 0.01) there was greater tendency to root fracture.

Analysis of Variance↗
PubMed1982

Photoelastic stress analysis of cast-gold endodontic posts.

Two-dimensional photoelasticity was used to compare stresses generated upon loading of cast gold endodontic posts of two different diameters. Ten models were used, five for each diameter size tested. The models were constructed to simulate maxillary central incisors. Drill bits were used to prepare the root canal, and after root canal preparation was completed the post preparations were constructed using the Parapost system. The gold posts, made of type III gold, were cast using the Beauty Cast technique. A composite core was then placed on each of the posts to be tested. These models were positioned in a circular polariscope and vertical loads of 30 and 60 pounds were applied to each of the models, with the fringe patterns photographed immediately after each load was applied. The stresses were evaluated by determining the maximum fringe order in the simulated root and periodontium of the model. The results of this study suggest that (1) the diameter of a post with a core affects the magnitude of stress, (2) stress generally increases as post diameter increases, and (3) stress increases as the vertical load increases. It seems advisable to restrict the diameter of the post used in providing support for restorations, particularly when large occlusal for forces are exerted by the patient. The use of smaller diameter posts reduces the stresses exerted upon the dentin of the tooth and the tooth supporting structures, limits the amount of tooth material removed during preparation and, possibly, aids operative procedures by limiting the amount of tooth preparation.

Crowns↗