Er:YAG Laser Irradiation Induces Behavioral Changes in V. harveyi.

OBJECTIVE: Laser technologies have many different applications in medical, agricultural, and industrial fields. Studies have shown several effects of laser energy on different bacterial species, in a wide variety of settings. Recent reports have found that one of the unique features of bacteria is their ability to communicate among themselves (quorum sensing). We sought to investigate whether low-energy laser irradiation affects bacterial behavior, which is regulated by quorum sensing. METHODS: Laser irradiations were performed using Er:YAG laser (2940 nm wavelength) at output powers of 0.5, 1.5, 2.5, and 4 W on wild-type Vibrio harveyi. Bioluminescence, motility, and biofilm forming capability were assessed on the bacteria after irradiation. RESULTS: After irradiation of bacteria, positive dose/output power dependencies were found in the bioluminescence omitted from tested experimental groups. Motility of colonies on semi-solid media was inhibited as irradiation output power was increased. However, after irradiation, biomass analysis of biofilm samples showed negligible differences between the irradiated samples and controls. CONCLUSIONS: Results indicate the impact of low-energy laser irradiation on bacterial behavior such as quorum sensing and motility, without affecting bacterial growth patterns.

Effect of ethylenediaminetetraacetic acid and sodium hypochlorite irrigation on Enterococcus faecalis biofilm colonization in young and old human root canal dentin: in vitro study.

INTRODUCTION: The alterations in dentin tissue depending on increasing age might cause different adhesion capability of bacteria, yielding differences in clinical approaches regarding root canal irrigation. This study, therefore, aimed to evaluate the effects of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) on Enterococcus faecalis biofilm growth in root canal dentin of young and old individuals. METHODS: The root canals of extracted young (<30 years) and old (>60 years) single-rooted human teeth were sectioned at the crown and the apical parts. The root canals of the mid-root sections were enlarged with #2 Gates-Glidden burs. After treatment with 17% EDTA + 2.5% NaOCl, 17% EDTA alone, 2.5% NaOCl alone, or saline, the samples were incubated in E. faecalis suspension for 24 hours. Thereafter, root canal samples were enlarged again with #3 Gates-Glidden burs, and the removed dentin chips were collected. Bacteria were dispersed by using sonication, serially diluted, and then plated for counting on agar plates as colony-forming units. Scanning electron microscopy and confocal laser scanning microscopy investigations were also carried out to examine the biofilm formation on the dentin. Data were analyzed with Kruskal-Wallis test and Mann-Whitney U test with Bonferroni adjustment. RESULTS: Combination of EDTA and NaOCl significantly reduced the amount of intracanal biofilm in both age groups (P < .01). However, the bacterial counts of E. faecalis in the old group were still higher (P < .05). CONCLUSIONS: It might be suggested that root canals from elderly population are more susceptible to canal infection. However, combined application of EDTA and NaOCl significantly reduces the amount of intracanal biofilm.

Chemical analysis and surface morphology of enamel and dentin following 9.6mu CO2 laser irradiation versus high speed drilling.

OBJECTIVES: The purpose of the present in vitro study was to determine whether there is a change in the chemical composition and surface morphology of enamel and dentin following 9.6mu CO2 laser irradiation and high-speed drilling. MATERIALS AND METHODS: Ten permanent, non-carious, young premolars, extracted for orthodontic reasons, were selected. The crowns were separated longitudinally into two equal parts at their mesiodistal axis. Two areas on the inner enamel surface of each specimen and two on the dentinal surface were selected. A high-speed drill and 9.6mu CO2 laser irradiation were applied to the selected enamel and dentinal areas. A random area on the unlased enamel and on the unlased dentin of each specimen served as controls. The morphology of the specimens was evaluated using scanning electron microscopy. Calcium, phosphorus and oxygen levels were measured using an energy dispersive spectrometer. RESULTS: Mineral analysis revealed no significant difference in the mineral content of the enamel and dentin after laser irradiation or high speed drilling versus the control. Use of the high-speed drill on enamel and dentin resulted in very clear cavity margins, with characteristic grooves, whereas laser irradiation of enamel and dentin did not produce clear margins and the floor of the cavity displayed an irregular surface. CONCLUSIONS: The 9.6mu CO2 laser appears to be a promising tool in the clinical setting. However, further investigation is indicated to ensure maximum effectiveness.

Lasers in endodontics.

With the rapid development of laser technology, new lasers with a wide range of characteristics are now available and being used in various fields of dentistry. In the past two decades, much experience and knowledge has been gained. This article provides an overview of the current and possible future clinical applications of lasers in endodontics, including their use in alleviating dentinal hypersensitivity, modification of the dentin structure, pulp diagnosis, pulp capping and pulpotomy, cleaning and shaping of the root canal system, and endodontic surgery. Endodontic procedures for which conventional treatments cannot provide comparable results or are less effective are emphasized.

The use of lasers in dentistry: principles of operation and clinical applications.

This article describes the principles of laser operation and the clinical application of laser technology in the different fields of dentistry. It discusses the use of the Er:YAG laser in restorative dentistry, pediatric dentistry, and periodontics, as well as the introduction of a new side-firing spiral tip for efficient cleaning of the root canal system by means of lateral laser irradiation. Although the Er:YAG laser is used mostly on enamel and dentin, the gingival depigmentation procedure using this laser also is described. Clinical applications of the CO2 and diode lasers on soft tissues, particularly in the fields of oral and maxillofacial surgery and perodontics, are explained. Because teeth whitening for esthetic reasons has gained increasing popularity in dentistry, the application of diode lasers for this purpose is discussed. All the dental laser procedures described in this article are conducted at the Hebrew University-Hadassah School of Dental Medicine and are further investigated in various clinical research projects.