Torsional resistance of crowns cemented to composite cores involving three stainless steel endodontic post designs

All about Dowels - A Review Part I. Considerations before Cementation

The optimal way of restoring a non vital tooth with dowel-core technique has long been a controversial matter. The purpose of this review was to assess the factors that may influence the successful restoration of root filled teeth with root canal dowels. The first part of the review discusses indications and physical parameters of dowel. Searches were performed in PubMed/Medline database using single or combined key words to obtain the most relevant list of references. Articles selected in the search process were obtained from the journals and reviewed with every aspect of dowel system for reconstruction of endodontically treated teeth. Medline search showed 228 articles for dowels but after applying exclusion criteria, only 51 articles remained to be included in Part I of this review. Out of which, 49 were in vitro studies and two were clinical studies. Reviewing the literature revealed that clinical data is still missing. Literature emphasizes that dowels should only be used for the retention of core material and not in view of reinforcing the remaining tooth structure. The dowel length is limited by the apical seal of four mm to six mm. Dowel width should be as small as possible. Canal configuration determines the selection between prefabricated and custom cast dowel. Fiber based dowel may be clinically appropriate for restoration of endodontically treated anterior tooth, although clinical studies are lacking.

Resistance of core materials against torsional forces on differently conditioned titanium posts

STATEMENT OF THE PROBLEM

The separation of core materials from titanium posts, which have a low modulus of elasticity, has been identified as a problem in restorative dentistry.

PURPOSE

This study evaluated the resistance to torsional forces of various core materials adapted to differently conditioned titanium posts.

MATERIAL AND METHODS

Seven hundred and twenty specimens were tested consisting of: 6 core materials and 5 surface conditioning techniques for 2 kinds of opaquers with 10 specimens in each group (6 x 5 x 2 x 10=600) plus 6 core materials and 2 opaquers were tested and considered as control groups on nonconditioned titanium posts, each group containing 10 specimens (6 x 2 x 10=120). The custom-made pure titanium posts were conditioned with the following products: Silicoater Classical, Silicoater MD, Rocatec, Kevloc, and Siloc surface-conditioning systems. Subsequently, 6 core materials with different compositions (Durafill, Adaptic, Coradent, Ti-Core, Hytac Aplitip, and Photac-Fil Aplitip) were applied to titanium posts that were previously coated with 2 types of light-polymerized opaquers, either Artglass or Dentacolor. Sixty air-abraded titanium posts (250 microm, 30 seconds) were used as controls for each core material. Following thermocycling (5 degrees -55 degrees C, 30 seconds, 5,000 cycles), maximum torsional forces were determined with an electronic torque movement key. Data were statistically analyzed by 1-way analysis of variance followed by 2-way analysis of variance (P<.05).

RESULTS

Significantly higher mean torsional forces were observed with respect to Siloc (20.4 Newton decimeter [dNm]), Silicoater Classical (18.6 dNm), Silicoater MD (18.2 dNm), and Rocatec (17.0 dNm) systems compared with the mean for the untreated control group (14.6 dNm) (P<.001). The Kevloc system (10.4 dNm) demonstrated no significant difference compared with the control group (P>.001). The Kevloc system in combination with the Artglass opaquer and Photac-Fil Aplitip (0.00 dNm) core material showed no resistance against torsional forces. Significant differences were observed between hybrid core materials and microfilled composite, compomer, or resin-modified glass ionomer core materials (P<.001).

CONCLUSION

Within the limitations of this study, the resistance to torsional forces for the core materials on titanium posts increased with the use of chemical surface-conditioning techniques and varied in accordance with the opaquer type. Type of core material also significantly influenced the resistance after thermocycling.