I ssN 1 985 -7047

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New Generation of DentalPosts for EndodonticApplication

Assoc. Prof. Dr. Noor Hayaty AbuKasimHead,Dept. of Conservative Dentistry,Faculty of Dentistry, University of Malaya,50603 Kuala Lumpur, Malaysianhayaty@um.edu.my

Co-ResearchersDr. Ahmed Abdullah Ali MadfaProf. Dr. Mohd HamdiAbd ShukorDr. Reza Rahbari Ghahnavyeh

apical part of theconcentrations at thelikely to be due to thethe compromisedstress concentrationsare generally due to

The restoration of endodontically treated teeth is a challengingtask as it usually involves the rehabilitation of teeth withsignificant loss of tooth structure. Tooth fracture has beendescribed as a major failure for endodontically treated teeth, andis the third most common cause of tooth loss after dental cariesand periodontal disease.

In endodontics, two types of post systems are usually used torehabilitate root canals and provide retention for the crowns: castand prefabricated posts which are commercially available indifferent geometries, dimensions and made from variousmaterials. There is also significant mismatch between materialproperties such as stiffness of the posts and surrounding dentaltissues. Moreover, the difference between thermal properties ofthese dental posts and tooth structure gives rise to thermo-mechanical stresses. High stress concentration can develop at therestorative-materials/tooth interfaces and thus increase thesusceptibility of fracture in endodontically treated teeth.

tooth. Stress

Ideally, a dental post should stabilize the coronal part of the restoration and at the same time does notweaken the root. When occlusal forces are applied coronally, the force is transferred to the dentinethrough the coronal and post system. In such situation, stresses tend to top concentrate at the cervical and

Tooth fracture has beendescribed as a major failure for

endodontically treated teeth

cervical region areincreased flexure oftooth structure, whileat the apical regionthe characteristics of

the post and the taper of the root canal apically. Therefore, it has been suggested that the ideal dental postshould have high stiffness at the cervical region and this stiffness should be gradually reduced apically.

Scanning electron micrograph analysis of the interface showed a continuous and graded phase distributionthat confirmed the functionally graded structure design (Figure 1). The linear shrinkage after sinteringalong the layers also confirmed linearity of properties changes inside these Functionally Graded StructureDental Posts (FGSPs).

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Figure 1: Functronally graded dental post composition (A) FGSP design, (B) Prototype FGSP.

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Figure 2: Von Mises stress distributions along central axis of FGSP under oblique loading.

FGSPs showed lower Von Mises stress concentration compared to the commercial dental posts asillustrated in Figure 2. The Ti concentration variation in xTi-yHA provided a smooth change in theproperties of FGSP offering advantages such as reduction of stress concentration. The FGSPs improved thestress dissipation and barred stress propagation into the structure successfully.

Figure 3: Von Mises stress distributions at post/tooth interface under oblique loading.

The FGSPs also dissipated the interface stress efficiently compared to commercial dental posts as shown inFigure 3. The high stress concentration at the middle and the apical parts are undesirable, which mayeventually cause debonding between the post and the root canal. This new generation of dental posts willdefinitely enhance the clinical durability of endodontically treated tooth and thus uplifting the patients'quality of life.