In vitro and In vivo Evaluationof Different Gingival Retraction Cords

Modern impression techniques used in restorative dentistry require displacementof gingival tissue to expose the subgingival finish lines on the tooth preparation. Many different medications are used on gingival retraction cords in order to minimize hemorrhage from the gingival sulcus during impression making. A common method of accomplishing gingival displacement is by packing cord into the gingival crevice. This is especially critical when using hydrophobic impression materials such as polyvinyl siloxanes. The purpose of this study was to determine whether any of the commonly used gingival retraction medications could inhibit the polymerization of polyvinyl siloxane impression materials when they are in direct contact with the setting material and to evaluate the clinical performance of retraction cords. Many gingival retraction cords in various shapes, sizes and medications are available on the market. The literature is replete with reports on the effects of medicated and non-medicated cords on impression and gingival tissue. In this study, the number of the criteria of evaluation was increased and both in vitro and in vivo studies were conducted together by three prosthodontists

Intraoral Repair of Metal Ceramic Restorations Following Preparation of the Endodontic Access Cavity (Case Reports)

The Manufacture of dental crowns and bridgework of porcelain fused to metal, a technique that results in highly functional and esthetic restorations, has been widely used for about 45 years. Bonded porcelain is exceptionally strong. However, the reasons for porcelain fracture may be multifactorial, and include where the bridge or crown substructure has been weakened by excessive occlusal adjustment or by the introduction of an endodontic access cavitiy. An esthetic and functional repair, wherever possible, has many advantages over time-consuming and expensive remakes of crowns and/or bridges. This report is a presentation of a simple method for both the dentist and the patient to repair a tooth with root canal treatment. In cases where the fracture is due to an endodontic access cavity, intraoral repair was performed using various porcelain repairing kits. The patients were recalled for follow up on a 3-month basis after treatment. This technique can be considered as a treatment of choice regarding the successful results

Stress distribution on dentin-cement-post interface varying root canal and glass fiber post diameters. A three-dimensional finite element analysis based on micro-CT data

OBJECTIVE: The aim of the present study was to analyze the influence of root canal and glass fiber post diameters on the biomechanical behavior of the dentin/cement/post interface of a root-filled tooth using 3D finite element analysis. MATERIAL AND METHODS: Six models were built using micro-CT imaging data and SolidWorks 2007 software, varying the root canal (C) and the glass fiber post (P) diameters: C1P1-C=1 mm and P=1 mm; C2P1-C=2 mm and P=1 mm; C2P2-C=2 mm and P=2 mm; C3P1-C=3 mm and P=1 mm; C3P2-C=3 mm and P=2 mm; and C3P3-C=3 mm and P=3 mm. The numerical analysis was conducted with ANSYS Workbench 10.0. An oblique force (180 N at 45º) was applied to the palatal surface of the central incisor. The periodontal ligament surface was constrained on the three axes (x=y=z=0). Maximum principal stress (σ(max)) values were evaluated for the root dentin, cement layer, and glass fiber post. RESULTS: The most evident stress was observed in the glass fiber post at C3P1 (323 MPa), and the maximum stress in the cement layer occurred at C1P1 (43.2 MPa). The stress on the root dentin was almost constant in all models with a peak in tension at C2P1 (64.5 MPa). CONCLUSION: The greatest discrepancy between root canal and post diameters is favorable for stress concentration at the post surface. The dentin remaining after the various root canal preparations did not increase the stress levels on the root

Preventing aspiration or ingestion of fixed restorations

WOS: 000181401500019PubMed ID: 1261624

Fracture resistance of five different metal framework designs for metal-ceramic restorations

WOS: 000179420400011PubMed ID: 12475164Purpose: This study evaluated fracture resistance of five different metal framework designs for metal-ceramic restorations. Materials and Methods: Twenty-five artificial crowns were fabricated with different degrees of facial metal reduction: metal collar (group 1), and 0, 0.5, 1, and 1.5 mm (groups 2 to 5, respectively). All of the crowns were thermocycled in two different baths of 5 and 60degreesC for 20 seconds and had a dwell time of 10 seconds in a resting bath at 37degreesC for 510 cycles. The artificial crowns were then subjected to vertical loading until fracture with a Shimadzu testing machine at a cross-head speed of I mm/min. The load at fracture was recorded. Results: There were no statistically significant differences between mean fracture strength of groups I and 2 or between groups 4 and 5. There were significant differences between group 3 and groups 1, 2, 4, and 5. Conclusion: As the amount of metal reduction increased, the vertical fracture resistance decreased. Failure loads for all test groups exceeded normal biting forces