Disputas: Kjersti Refsholt Stenhagen
Cand.odont. Kjersti Refsholt Stenhagen ved IKO vil forsvare sin avhandling for graden ph.d.: Effect of fluoride solutions on enamel erosive wear and validation of methods used for analyses
Tid og sted for prøveforelesning
- Oberassistentin PhD Dr. Anette Wiegand, University of Zürich (førsteopponent)
- Senior research scientist B.Sc. and Ph.D. John Earl Tibbals, Nordic Institute of Dental Materials AS, Oslo (andreopponent)
- Professor Dr. odont. Bjørn Øgaard, komiteens leder
- Professor Ståle Petter Lyngstadaas
- Professor Anne Bjørg Tveit, Det odontologiske fakultet, Universitetet i Oslo
- Førsteamanuensis Lene Hystad Hove, Det odontologiske fakultet, Universitetet i Oslo
Effect of fluoride solutions on enamel erosive wear and validation of methods used for analyses
The reported prevalence of dental erosive wear varies from 20-58 % in adolescents. In addition to minimizing the acidic risk factors, preventive strategies are important to slow down the tooth substance loss and thereby avoid aesthetic and functional problems resulting in the need for advanced restorative treatments. When studying the effect of preventive measures against dental erosive wear in the laboratory, a variety of measurement techniques have been used, often with insufficient validation procedures. A technique where enamel loss was measured by the use of a white light interferometer has been developed and it can possibly be used to measure on impressions of teeth as well. This could overcome one challenge in clinical studies since most measurement techniques cannot be used directly in the mouth. Metal fluoride solutions with titanium or stannous have reduced dental erosion in vitro and in situ, but their biocompatibility has often been questioned due to the high concentration and low pH.
The objective of the thesis was first to validate and compare five measurement techniques commonly used in studies of dental erosion (mechanical and optical profilometer, white light interferometer, atomic absorption spectroscopy and hardness tester), by investigating the accuracy and precision of the respective methods. To study if a white light interferometer could measure enamel loss on impressions of eroded enamel was also an aim of the thesis. The second objective was to investigate in vitro if reducing the concentration and buffering the pH of titanium fluoride solutions would reduce the protective effect against dental erosion. It was also investigated if daily applications of metal fluorides like titanium- and stannous fluoride solutions in mouth-rinse concentrations could inhibit or reduce enamel loss from erosion and toothbrush abrasion in situ.
The studies showed that mechanical and optical profilometer, white light interferometer and atomic absorption spectroscopy all gave reliable measurements of erosive enamel wear and that the white light interferometer gave accurate and precise measurements on impressions of eroded tooth surfaces. Lowering the concentration (from 0.5M F to 0.05M F) and buffering the pH of titanium fluoride solution applied once, reduced the protective effect against dental erosion from repeated acid attacks. However, stannous- and titanium fluoride solutions used daily as mouth-rinse (0.05M F and native pH 2.5 and 2.1) reduced enamel wear from frequent erosion and toothbrush abrasion by 94 % and 90 % respectively. Eight healthy and young students participated in the study and wore intraoral appliances with tooth specimens.
The very good protective effect of both titanium- and stannous fluoride solutions against dental erosive wear is very promising, although the biocompatibility of the solutions must be tested further before they can be introduced for clinical use. The technique by which dental erosive wear is indirectly measured on impressions could be relevant for clinical studies into progression of dental erosion and intervention studies into the effect of preventive treatment.