Einfluss des Wassersprays auf die Ablation von Zahnschmelz mit dem Er,Cr:YSGG-Laser

The aim of the present thesis was to examine the influence of external water spray occurring with the application of Er,Cr:YSGG laser on ablation of dental enamel. For this purpose, the combined dose of water and gas was defined and varied in order to gain a maximum of substance ablation avoiding any thermal damage of dental hard tissue. Therefore, 3, 4, and 5 watt power adjustments were combined with water doses of 1, 1.5, 2, and 3 ml/s. A third parameter, which comprises three different mixing ratios of water and gas, was combined with the first mentioned factor of influence. Each test series consisted of two samples of tooth tissue so that the scale of samples resulted in 96 extracted human wisdom teeth free of caries altogether. The series of experiments was conducted with an Er,Cr:YSGG laser (Biolase®) at a wavelength of 2,78 µm. This way it was for the first time possible to determine a threshold of ablation in relation to the amount of water flow which finally resulted in 0.7-0.8 ml/s. Below this level a hard tissue ablation by means of a laser was impossible. As far as the power adjustments are concerned, a second threshold for ablation was identified. The series of experiments showed that power adjustments of less than 2 watt, which corresponds to an energy density of 14.2 J/cm², did not lead to any ablation of hard tissue at all. The results showed that the amount of water flow within the chosen parameters had an impact on the volume of ablation. The maximum volume of ablation per pulse with a water flow of 1 ml/s was reached at 3 watt. Any increase of the amount of water flow resulted in a reduction of ablation. Opposite results were achieved at 5 watt. At this power level larger amounts of water flow were needed in order to ablate more hard tissue. The amount of water flow had a statistically significant influence (p=0.03916) on the volume of ablation at 3 watt, while with 4 and 5 watt the influence of the amount of water flow was insignificant (p=0.48662 at 4 watt, and p=0.54977 at 5 watt). Even if the results partially failed to meet the level of significance, tendencies were detectable. These tendencies highly depended on the quantitative composition of water and gas but apparently did not depend on its quality. This parameter exclusively showed a statistically significant influence at 4 watt (p=0.03587). The analysis under consideration of both features, that is, the amount of water flow and the composition of water and gas, resulted only in significant differences at a power adjustment of 3 watt (p=0.01736). With 4 and 5 watt the influence was in turn insignificant (p=0.27236 at 4 watt, and p=0.53273 at 5 watt). Although it was possible to show that the amount of water flow had an impact on the volume of ablation per pulse, it is to be proved by further experiments with an appropriate scale whether the statistically significant results achieved during the analysis are actually maintainable. Apart from the volume of ablation per pulse, the energy of ablation was additionally examined by describing an optimized and specific energy of ablation in a sense of an efficient ablation related to the energy per ablated volume. It was observable that the specific energy of ablation continually declined with increasing density of energy. Additionally, the density of energy declined more rapidly with an increasing amount of water flow. This means that a low specific energy of ablation can only be achieved at a low density of energy within the defined limits between 21.6 and 36 J/cm² in combination with high rates of water flow, or can be achieved at a high density of energy in combination with as little as possible a dose of water flow.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2006

Author dc:creator

• Feld, Jennifer

Contributors dc:contributor

• Apel, Christian

• info:eu-repo/classification/ddc/610
• Medizin

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-122215%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:60509