Heat Treatment May Improve Dentin Fracture Toughness

Non-vital or pulpless teeth, being brittle, are more prone to fractures. Now, in a new research article published in the recent issue of the Journal of Dental Research, it has been reported that heat treatment strengths the human dentin, and can be very useful in preventing fractures of the non-vital tooth. Buy online from NHS Heroes at https://www.nhsheroes.co.uk/

Based on the fact that heat increases the flexural strength of type I collagen, a major organic component of human dentin, the team of researchers, led by Mikako Hayashi at the Osaka University Graduate School of Dentistry, Osaka, Japan, hypothesized that the strength of human dentin can also be increased by heat treatment. From the crowns of third molars, beam-shaped dentin specimens were obtained, on which load was applied, either parallelly or perpendicularly to the dentinal tubular orientation.

Following one hour of heat treatment at temperatures between 110 and 140°C, the parallel specimens showed 2-2.4 fold greater flexural and microtensile strength, and an increase in the stress intensity factors at fracture. On x-ray diffraction analyses, the lateral packing of collagen triple-helices in these samples decreased from 14 A to 11 A. This was thought to be the most probable cause for the increased dentinal strength. The authors thereby concluded that human dentin can be strengthened by heat treatment.

Dentin, the mineralized layer formed by odontoblasts, is found between the enamel and pulp chamber and forms the bulk of the tooth. Compared to the enamel, which is the hardest tissue in the body, dentin is less mineralized and ranks 3-4 on the Mohs hardness scale. In a non-vital tooth, blood supply to the dentinal layers is compromised, making the tooth brittle and more susceptible to fractures.

Extensive research has been done to study dentin fracture toughness. A study by Laura Tam (Journal of Dental Research, 2007) from The University of Toronto, Canada, evaluated the response of dentinal structures to peroxide tooth bleaching. The study concluded that bleaching techniques reduce the dentin fracture toughness. In another study by Zhang DS (Zhonghua Kou Qiang Yi Xue Za Zhi, 2007) it was documented that dehydrated dentin due to its brittleness, had decreased fracture toughness compared to hydrated dentin.

From a clinical standpoint, restoration of endodontically treated tooth is challenging due to the fact that the teeth has lost substantial tooth structure as a result of caries, previous restoration or access opening for endodontic therapy. The brittleness of the endodontically treated tooth, due to compromised blood supply to the dentin, can be another cause of concern as brittle teeth are more prone to fracture. As this new study emphasizes on heat treatment in the successful increase of dentinal strength, this technique may help avert fracture of non-vital tooth and improve its long-term prognosis after restoration.