Removal of Dental Caries Using a Pulsed Nd:YAG Laser - In Vitro and In Vivo

Ansari, Ghassem (1996) Removal of Dental Caries Using a Pulsed Nd:YAG Laser - In Vitro and In Vivo. PhD thesis, University of Glasgow.

Abstract

The pulsed Nd:YAG laser energy was tested for its effect on carious lesions in both primary and permanent teeth. Four individual experiments were designed to assess the different effects of this laser wavelength on the hard tissue of the teeth. The first experiment assessed the effect of three different laser energy densities on carious dentine. These energies were also tested for their effect on sound, unaffected dentine, to clarify the effect of the different laser energies on the sound underlying dentine after the dentine caries had been removed. The power of 60 mJ at 15 pps (1.25 W) was confirmed to be the optimal power setting amongst the powers tested in this study. This laser energy was therefore used for the following experiments. The degree of pulp temperature rise following the exposure of the laser during caries removal was evaluated and compared to the routinely used heat- producing pieces of equipment in vivo, namely: the conventional drill and the polymerising blue light. The temperature rise caused by the laser energy of 1.25 W for 30 sec was found to be considerably higher than that of the other two. However, this peak temperature was shown to drop to lower levels, close to the baseline temperature, immediately after the irradiation stopped. The changes of the dentine surface following laser/drill caries removal was tested by assessing the margins of restorations for the presence of any gap and any microleakage. Results showed that the restorations of teeth in both laser- and drill-treated groups indicated some degrees of microleakage but with no significant differences between the two. The gap sizes measured were also found to have no significant differences between the two groups of laser- and drill-treated teeth. It was suggested, therefore, that preparation of the cavities by the laser can be as efficient as conventional drilling for the adhesion of adhesive restorative materials. And finally, the applicability of the laser for the removal of dental caries in anxious children was evaluated. This also permitted observations to be made on the in vivo effects of this laser on a group of vital pulps. Patients' anxiety was assessed by employing all three parties involved in the child's dental treatment: operator, child, parent. Results of this study indicated that patients had a higher preference for the laser caries removal technique when compared to conventional drilling. Both patient and parent were asked as to their views about the two techniques of caries removal. In addition, the patient's reactions were recorded before, during, and after each treatment. Each child received both treatment modalities to enable the assessment of the effect of individual techniques on patients' anxiety. Pulps of the treated teeth were assessed by means of ethyl chloride and the Electric Pulp Tester, in addition to the radiographic and clinical examination of the surrounding structures. Results of these investigations revealed that pulpal status was not only different in those teeth treated with the laser, when compared with the drill, when they were examined after 18 to 24 months follow-up. The clinical assessment of restored teeth was also carried out over the same period (18-24 months) and indicated comparable success to conventional cavity preparation for the laser irradiated teeth. In conclusion, it seems that the pulsed Nd:YAG laser, with the energy level of 1.25 W for a maximum of 30 sec for each exposure may be used with minimal pulpal damage for the treatment of caries in primary teeth. This may provide an acceptable alternative to conventional drilling for young, fearful patients and may, therefore, reduce the amount of dental fear and anxiety in this group of the society.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: S L Creanor
• Keywords: Dentistry, Biomedical engineering
• Date of Award: 1996
• Depositing User: Enlighten Team
• Unique ID: glathesis:1996-75298
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 21:17
• Last Modified: 19 Nov 2019 21:17
• URI: https://theses.gla.ac.uk/id/eprint/75298