Very Dental Classics: Sugar, Science and Dr. Rella Christensen

This classic Dental Hacks episode features a long-form interview with Dr. Rella Christensen of TRAC Research (formerly CRA). The discussion covers the history of independent product evaluation, the challenges of maintaining objectivity in dental research, and significant findings regarding restorative materials and caries management. The original interview had really poor sound quality but a little help from an Adobe AI filter really cleared it up. This interview was worth another listen, I think!

Key Interview Highlights

1. The Origins and Ethics of TRAC Research

• History: The organization began in 1976 (founded by Gordon Christensen) with the goal of collecting subjective data from clinicians to create objective "Consumer Reports" style rankings for dentistry.

• Unbiased Stance: Dr. Christensen emphasized that TRAC is a non-profit foundation that accepts no funding from manufacturers. If a company refuses to provide a product for testing (often fearing a negative review), TRAC purchases it on the open market to ensure the data is captured.

• The "File Drawer" Effect: They discussed how negative research is rarely published in journals due to corporate influence in dental schools and editorial boards. TRAC aims to publish the truth, even when it is negative.

2. Restorative Materials: The Zirconia Revolution

• 10-Year Study Results: Dr. Christensen detailed a 10-year study comparing various ceramic systems.

  • The Failure: Zirconia substructures (like Lava) survived well, but the veneering ceramics (porcelain layered on top) had massive failure rates (chipping and cracking).

  • The Winner: The study pointed toward monolithic zirconia (specifically BruxZir) and lithium disilicate (e.max) as the most durable options.

• Translucency Warning: She noted that as manufacturers push for more translucent (anterior) zirconia, they often lower the flexural strength (from ~1200 MPa to ~600 MPa). She cautioned that the long-term fracture toughness of these newer, "prettier" zirconias was still unknown at the time

3. The "Bombshell": Enamel Remineralization & Caries

• The Study: TRAC performed an in-depth clinical study on 330 orthodontic patient