Physical Studies of Dental Pit and Fissure Sealants

Dentistry

Young, Kenneth Charles

University:University of Glasgow

关键词: Dentistry;   

Others  :  http://theses.gla.ac.uk/78760/1/13804123.pdf

来源: University of Glasgow

【 摘 要 】

The application of sealants to pits and fissures on occlusal surfaces of teeth as a caries preventive measure has been evaluated in numerous clinical studies. However, the duration of sealant cover and the caries reductions found in these different trials were extremely variable, even where the same materials, and ostensibly the same techniques, had been used. The primary objective of this study was to investigate physical factors involved in applying sealants and to devise changes in materials and application procedures to ensure long term sealant retention and caries reduction. A second objective was to explain the very poor retention found by Stephen, Sutherland and Trainer (1976) for the TP2206 (Alphaseal) fissure sealant system. The effects of various clinical factors, including moisture contamination and surface treatments, on the adhesion between sealant and enamel were assessed using a new tensile testing technique. These tests also indicated the importance of applying sufficient u. v. radiation to set the resins. A subsequent investigation of the output and distribution of radiation from u.v. sources supplied for clinical use, showed a wide range in performance for different units of the same type. In particular, one of the sources used by Stephen et al. (1976) had a very low output. Studies with microhardness measurements showed that Nuva-seal set more rapidly and to a greater final hardness when higher u.v. intensities were used. Alphaseal set more slowly than Nuva-seal, and did not set readily in depth. U.V. absorption measurements indicated that the transmission through Nuva-seal was sufficient to allow setting to the depths normally expected of fissure sealants. Alphaseal showed much stronger absorption, which was partly due to a fluorescent dye incorporated to aid long term sealant detection, and partly due to the high concentration of catalyst used (5% w/w). The setting behaviours of three u.v. activated sealants (Nuva-seal, Alphaseal and Nuva-cote) were compared using a new method, which relied on the passage of acoustic vibrations to determine the set. The nature of the dependence of the rate of set on the u.v. intensity was similar for all three materials. However at any given intensity Nuva-seal set faster than Nuva-cote and Alphaseal by factors of about 4 and 13, respectively. The slow setting of Alphaseal was largely due to the strong absorption of the u. v. radiation in the surface layers. Removing the fluorescent dye and reducing the catalyst concentration to 1% w/w, resulted in an increase in the rate of set of Alphaseal by a factor of 1