Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin

Abstract

Background and Objectives: A reliable method to eradicate the bacteria of residual carious dentin has not yet been developed. The aim of this study was to evaluate the antibacterial effect of a diode laser on Streptococcus mutans through different thickness (500, 1,000, and 2,000 mm) of human dentin. The thermal effect of laser irradiation was also investigated. Study Design/Materials and Methods: Dentin specimens were inoculated with 2 ml of S. mutans on one side and irradiated by a diode laser on the other side with a power output ranging from 0.5 to 7 W. The laser tip was swept with the whole irradiation area of 7 mmÂ3 mm at a speed of about 10 mm/second with a total irradiation time of 30 seconds. Cooling with distilled water (30 ml/minute) was applied simultaneously during laser irradiation. After laser irradiation, the bacteria was removed from the dentin surfaces and cultured for 48 hours at 378C anaerobically to assess the colony forming units (CFU) per ml. The morphology of the lased bacteria and the temperature rise during laser irradiation were observed by scanning electron microscope (SEM) and measured by thermocouple, respectively. Results: The results revealed that 7 W of laser power could kill 97.7% of CFU through 500 mm thickness of dentin. However, the bactericidal efficiency was significantly reduced as the dentin thickness was increased. The morphological changes of lased bacteria ranged from less affected such as loss of their wall bands and existence of minicells to more severely degenerated, such as disintegration and fusion of cells with pores on the cell wall. Only the dentin specimens with a thickness of 500 mm exhibited a temperature rise greater than 5.58C after receiving 5 or 7 W of laser irradiation. Conclusions: A diode laser can eliminate the Streptococcus mutans of the residual carious dentin without inducing high pulpal temperature rise when the remaining dentin thickness is greater than 1 mm.

Bactericidal Effects of 2.94μm and 1.67μm Laser

“…3 Temperature change of plate after laser irradiation Almost no increase in temperature of anhydrous quartz at 1.67m or 2.94m, but temperature of dentin plates increased to more than 90°C at both wavelengths. provide sufficient sterility for caries, periodontal disease or infected root canals 2,[4][5][6][8][9][10]13,18) . In this study, S. mutans was selected as the target from the perspective of prevention of secondary caries.…”

“…Lasers have been used clinically in dental practice for various purposes, including tooth cutting, washing in root canals, scaling, and pain relief in soft tissues 14,15) ; and many studies have reported the bactericidal effects of lasers. 2,[4][5][6][8][9][10]13,18) However, lasers have different properties depending on wavelength; for example, the Nd:YAG laser has high tissue permeability and is able to affect deep tissue, whereas the Er:YAG laser has good absorption properties in water and acts on the surface of tissues.…”

The bactericidal effect of carbon nanotube/agar composites irradiated with near-infrared light on Streptococcus mutans

“…Therefore, many methods have been established to eliminate S. mutans from the oral cavity [1,2]. One such approach is photodynamic therapy [3][4][5]. A series of studies have demonstrated the photodynamic inactivation of bacteria by the exogenous application of a photosensitizer such as methylene blue or toluidine blue [4].…”

Effect of Different Cavity Disinfectants on Bond Strength of a Posterior Composite

“…22 Lazerlerin antibakteriyel etkisi, lazer enerjisi, absorpsiyon özellikleri, hücrenin hacmi ve su içeriği, bakterilerin dentin tübüllerin-deki hareketi gibi birçok faktöre bağlıdır. 23,24 Çalış-malarda, farklı lazer tiplerinin farklı bakterilere karşı antibakteriyel etkilerinin olduğu gösterilmiş-tir. 10,23,25 Lazerlerin kavite dezenfeksiyonunda olumlu etkilerine rağmen, adezif sistemlerin dentine bağlanmasında negatif etkilerinin olduğunu belirten çalışmalar mevcuttur.…”

“…23,24 Çalış-malarda, farklı lazer tiplerinin farklı bakterilere karşı antibakteriyel etkilerinin olduğu gösterilmiş-tir. 10,23,25 Lazerlerin kavite dezenfeksiyonunda olumlu etkilerine rağmen, adezif sistemlerin dentine bağlanmasında negatif etkilerinin olduğunu belirten çalışmalar mevcuttur. [26][27][28] Araştırmacılar, bu olumsuz etkiyi lazerlerin kollajen fibril ağlarını denatüre etmesine bağlamışlardır.…”