Chemomechanical Removal of Dental Caries: An In Vitro Study

Yip, Hak Kong (1992) Chemomechanical Removal of Dental Caries: An In Vitro Study. PhD thesis, University of Glasgow.

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Abstract

The removal of dental caries is usually carried out by mechanical excavation using hand and /or rotary instruments. The carious process in human teeth, in particular dentine caries, and the development of various techniques of caries removal have been reviewed. The evolution of the dental engine has enabled gradual improvements in the mechanical devices used to prepare cavities. No chemical means of removing caries has ever gained general acceptance in restorative dentistry. This is partly due to the advantages to the dentist of mechanically prepared cavities and partly because of the difficulties in finding a reagent that would remove caries effectively without causing any damage to the underlying sound dentine and pulpal tissue. Although a purely chemical caries removal system has never been devised, a chemomechanical caries removal system was first introduced in the early nineteen seventies in the USA. The system was marketed as the Caridex Caries Removal System in the early nineteen eighties after approval by the Food and Drug Administration (USA). The active ingredient of the caries removal agent is N-monochloro-D,L-2-aminobutyric acid (NMAB) which is generated by mixing sodium hypochlorite and aminobutyric acid. It has been suggested that NMAB reacts with the partially degraded collagen of the carious dentine making it more soluble thereby enabling the carious material to be more easily excavated. In this study a simulated system in which the parameters are more strictly controlled than in the Caridex system was constructed. Possible improvements in the effectiveness of chemomechanical caries removal were studied by incorporating various protein de-naturing agents into the existing system. Initially a series of in vitro studies was carried out to investigate the effectiveness of various caries removal agents in extracted permanent and deciduous teeth with carious lesions and attempts were made to improve the present formulation. The results have indicated that NMAB containing urea resulted in an improvement in the effectiveness of caries removal when compared with NMAB alone. This improvement seemed to be more effective in carious deciduous than permanent teeth, the difference was, however, not statistically significant. Attempts were made to assess whether caries removal was complete by means of two caries detector dyes (0.5% basic fuchsin and 1.0% acid red in propylene glycol) but neither reagent had adequate specificity. In a subsequent in vitro study, a more "standardised" group of extracted carious deciduous teeth was used and these showed a higher percentage of teeth in which complete caries removal was achieved than in the preliminary study. The microscopic features of the dentine remaining after caries removal were studied using light and scanning electron microscopy. The surfaces of the cavities after chemomechanical caries removal had a very uneven appearance with many undermined areas; "dentine scales", patent and occluded dentinal tubules could also be observed. The differences in the dentinal surfaces of cavities with complete caries removal may represent a range of differences in the interface between carious and sound dentine. Few bacteria were found after chemomechanical caries removal. Backscattered electron imaging and electron probe X-ray microanalysis of the dentine remaining after chemomechanical caries removal showed the dentine was sound and normally calcified and suitable for the application of restorative materials. The advantages and disadvantages of the chemomechanical caries removal system using the improved reagents are discussed and future research suggested.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J A Beeley
Keywords: Dentistry
Date of Award: 1992
Depositing User: Enlighten Team
Unique ID: glathesis:1992-75202
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 21:47
Last Modified: 19 Nov 2019 21:47
URI: http://theses.gla.ac.uk/id/eprint/75202

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