Investigation into the Effects of Filling Materials on the Dental Tissues

Nixon, George S (1959) Investigation into the Effects of Filling Materials on the Dental Tissues. PhD thesis, University of Glasgow.

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This Thesis describes an investigation into the effects of zinc phosphate cement, silver nitrate and silver-tin amalgam on the dental tissues. In the introduction a review is given of the irrational use in the past of filling materials and of previous investigations into the effects of filling materials on the vital dental tissues. The importance of the close physiological relationship between dentine and dental pulp is emphasised. The development of the use of radioactive isotopes in biological research and their suitability for further use in investigating the effects of filling materials is discussed. Methods of detecting and measuring these radioactive materials are described with particular application of these methods to this investigation. A description of the filling materials used in this treatise is given with the methods of preparing them for radiochemical examination. The selection of teeth, both human and animal, is also described together with a standardized method for preparing the tooth cavities. The history of zinc phosphate cement is reviewed and the complex reaction which takes place when the powder and liquid of this cement are mixed is described. It is shown that phosphoric acid and primary acid phosphate are present when the cement is in the plastic state. The importance of variations in the consistency of the plastic cement is stressed. Measurements of acidity are also given which show that this cement is strongly acid when placed in the tooth cavity, and remains acid after setting. The results of the experimental work on this material are incorporated into a discussion. These results confirm that, a reaction of some degree will occur in the dental pulp when this cement is placed in contact with vital dentine. Radioactive tracers show that the phosphoric acid and primary acid phosphate present during the setting reaction penetrate along the dentinal tubules cut during cavity preparation. The degree of penetration of the acids and the severity of the pulpal reaction vary with the consistency and time/ time of insertion of the cement into the tooth cavity. Penetration and reaction are most severe with thin consistencies inserted immediately after mixing. A layer of calcium hydroxide paste placed between the cement and the dentine is effective in reducing the severity of the pulpal reaction. The results also show that no diffusion of arsenic takes place from zinc phosphate cement into dentine. A chapter on silver nitrate describes the history of this material and methods of applying it to the dental tissues. The results of the investigations are given and a discussion is included. In assessing the results of the silver nitrate experiments, the variations which may occur in the permeability of dentine are stressed. It is demonstrated that silver nitrate is taken up by the enamel of the teeth at a constant rate in relation to the duration of the application. The penetration of silver nitrate through vital dentine is also shown. The use of the medicaments, alcohol and phenol, on the cavity floor is shown to increase the permeability of the dentine to silver nitrate; and it is advised that/ that neither phenol nor alcohol should be applied to freshly cut dentine. A possible explanation is given to the varying results on dentine permeability to different dyes.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Dentistry
Date of Award: 1959
Depositing User: Enlighten Team
Unique ID: glathesis:1959-79312
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 10:57
Last Modified: 05 Mar 2020 10:57

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