A happy PhD candidate Yasser Haddadi, with his primary supervisor, and the committee after the examination.  From the left; NIOM CEO professor Jon E. Dahl, the candidate, professor Ann Wennerberg, Gothenburg, professor Flemming Isidor (primary supervisor), Aarhus, and associate professor Ellen Frandsen Lau, Aarhus.

On Friday June 28, NIOM’s CEO, prof. Jon E. Dahl acted as public opponent when PhD candidate Yasser Haddadi defended his doctoral dissertation in Aarhus, Denmark. The dissertation is titled: “Intra-oral scanning in fixed prosthodontics – Laboratory and clinical comparative studies.”

The study

Dr. Haddadi’s study centered on the accuracy of eight different intra-oral scanners, which were compared to conventional impression (CI) taking of a single tooth preparation.

A master tooth (MT) was digitized using a high-accuracy optical industrial scanner. Ten impressions were taken of the MT with eight different intraoral scanners as well as ten CI. The MT was scanned twice with the CEREC Omnicam with two different software versions (4.4.0 and 4.4.4).

Nineteen patients needing crowns on posterior teeth that allowed a split-mouth experimental design were recruited. Two crowns were produced for each patient. One, based on an intra-oral scanning, the other based on a CI. All elements of the impression taking were timed for both methods.

6 and 12 months

Immediately after impression taking, all patients filled out a questionnaire on discomfort associated with the treatment they had just gone through. Prior to cementation of the crowns, the internal and marginal fit was checked using the replica technique.

The clinical fit was also assessed after 6 and 12 months by blind and non-blind examiners using California Dental Association’s (CDA) quality evaluation system.

The examination took place at Section for Periodontology, Department of Dentistry and Oral Health, University of Aarhus, Denmark.