Abstract

A possible cause for root canal failure is the persistence of bacteria that have colonized dentinal tubules. To reduce this risk and, if possible, to also shorten the time consuming endodontic therapy, new equipment and materials are constantly being introduced. The aim of the present investigation was to study the effect of disinfection of dentinal tubules by intracanal laser irradiation using an in vitro model. The groups irradiated by various lasers were compared with calcium hydroxide, a material frequently used as intracanal medication between appointments. Freshly extracted, intact bovine incisors were used. The root cementum was removed and the teeth cut to produce 180 standardized specimens. For bacterial colonization, specimens were kept in test tubes with Tryptic Soy Broth containing Enterococcus faecalis and incubated at 37°C. In order to restrict the growth to this strain only, E. faecalis carrying a plasmid that allowed resistance to chloramphenicol was used as the test organism. The specimens were divided in five treatment groups and three control groups. For irradiation, pulsed delivered Ho:YAG laser at 2.1 µm, Nd:YAG laser (1.06 µm), and Er:YAG laser (2.94µm) with and without air/water coolant, were used. Lasers groups received three different laser settings for treatment: output energy below the physical modification threshold (½ of PMT) for 60 sec, at the PMT for 60 sec and above the PMT (120 sec). As controls, three specimens for each treatment group received sterile water instead of bacteria (negative control), three received iodine potassium-iodide (IKl) after bacterial exposure (negative control), and three did not receive treatment after bacterial exposure (positive control). Group 5 received a seven-day treatment with calcium hydroxide. The number of bacteria was estimated by counting CFU using Tryptic Soy Agar after dilution. Statistical analysis showed the bacterial reduction as follow: Ho:YAG laser > calcium hydroxide > Nd:YAG laser > Er:YAG laser with air/water coolant > Er:YAG laser without air/water coolant. There was a significantly higher bacterial reduction in the group irradiated by the Ho:YAG at the PMT (50mJ, 10 Hz, 66 J/cm2 for 120 sec), followed by Ho:YAG irradiated at 50mJ, 10 Hz, 33 J/cm2 for 60 sec, and the group that received calcium hydroxide. The latter two groups were not significantly different.

Department

Dentistry

School

Graduate School

First Advisor

Mahmoud Torabinejad

Second Advisor

Hafid Abaibou

Third Advisor

Leif K. Bakland

Fourth Advisor

Jay S. Kim

Fifth Advisor

Joel M. White

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2000

Date (Title Page)

12-2000

Language

English

Library of Congress/MESH Subject Headings

Dentin; Disinfection; Lasers; Dental Disinfectants; Dental Pulp Cavity

Type

Thesis

Page Count

ix; 84

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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