The present summary and the following papers (I-VIII) are submitted in partial fulfillment of the requirements for the degree of Doctor Philosophiae at the University of Oslo.I. Composition of dental resin and composite materials. Acta Odontol. Scand. 1981, 39, 133–146Co-author: I.J. SjøvikII. Remaining methacrylate groups in composite restorative materials. Acta Odontol. Scand. 1978, 36, 75–87Co-author: S.A. SvendsenIII. Conversion in different depths of ultraviolet and visible light activated composite materials. Acta Odontol. Scand. 1982. 40, 179–192 Co-author: H.øysædIV. Compressive creep of light cured resin based restorative materials. Acta Odontol. Scand. 1982. 40, 319–324Co-author: H.øysædV. Flexural properties of denture base polymers. J. Prosthet. Dent. 1980, 43. 95–104Co-author: S.A. SvendsenVI. Compressive creep of denture base polymers. Acta Odontol. Scand. 1980, 38, 169–177Co-author: S. EspevikVII. Conversion in denture base polymers. J. Biomed Mater. Res. In press Co-author: H.øysædVIII. Release of formaldehyde from denture base polymers. Acta Odontol. Scand. 1980, 38, 17–27In this summary these papers will be referred to as Papers I-VIII. Other literature cited will be referred to in the conventional manner.