Research articles

By Dr. Ahmed Al-habeeb , Dr. Maan Nayif , Prof. Mahmoud Y Taha
Corresponding Author Prof. Mahmoud Y Taha
College of Dentistry, College of Dentistry, mosul University - Iraq
Submitting Author Prof. Mahmoud Y Taha
Other Authors Dr. Ahmed Al-habeeb
College of Dentistry, - Iraq 964

Dr. Maan Nayif
College of Dentistry, - Iraq


Diode Laser, Streptococcus mutans, Antibacterial activity.

Al-habeeb A, Nayif M, Taha MY. Antibacterial Effects of Diode Laser and Chlorhixidine gluconate on Streptococcus mutans in Coronal Cavity. WebmedCentral DENTISTRY 2013;4(8):WMC004179
doi: 10.9754/journal.wmc.2013.004179

This is an open-access article distributed under the terms of the Creative Commons Attribution License(CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submitted on: 22 Aug 2013 10:45:25 PM GMT
Published on: 23 Aug 2013 10:52:55 AM GMT


Background : The principal objective of caries removal is to eliminate the infected and necrotic tissues and microorganisms that may cause a persistent inflammation and treatment failure. The aim of this study was to compare the antibacterial activities of diode laser), commercially available chlorhexidine gluconate (CHX)  and the prepared one as a cavity disinfectant.
Methodology: 70 extracted sound human premolar teeth used. Crown of teeth was cut horizontally to obtain flat dentinal surfaces. One cylindrical cavity (2 mm in diameter, 1 mm in depth) prepared on the flat surface. Samples were divided into 7 groups, each consisted of 10 prepared teeth. The first twenty samples disinfected with (commercially available) Chlorhexidine (2% and 0.2%), the second twenty samples (prepared) chlorhexidine gluconate (2% and 0.2%), and the last twenty diode laser (1w and 1.30 w). Dentin chips from the cavity walls collected immediately after treatment and put into sterile tubes containing 0.5mm of sterile normal saline. A 200µm from this saline was  dispensed over Petri-dish contain Mitis-Salivarios agar.
Results: The results showed that the CHX solution, CHX powder and diode laser have a significant difference from the control group. Highest antibacterial effect on S. mutans achieved by CHX solution (2%) followed by CHX solution (0.2%). In the second order group, CHX powder (2%) followed by CHX powder (0.2%) showed comparably higher mean values of bacterial colonies than the first two groups mentioned above, and there is a difference between them but not significant.
Conclusion: The antibacterial effect of CHX (solution, powder) at all concentrations (2% and 0.2%) and diode laser at all powers (1w and 1.30w) in the infected coronal cavities with S. mutans was significantly different from untreated control group.



The principal objective of caries removal is to eliminate the infected and necrotic tissues and microorganisms that may cause a persistent inflammation and treatment failure. Thus, thorough removal of the infected dentin has a direct influence and impact on the clinical success of a restoration. However, the caries treatment procedures used presently not always assuredly eliminates all of the microorganisms in residual tissues. Bacterial sources which contribute to cavity infection come from: Invasion from the tooth surface via marginal gap formation between a tooth and the restorative material, bacteria present in the smear layer, bacteria present in the dentinal tubules, bacteria present at the dentinoenamel junction and bacterial recontamination of the surface prior to restoration placement. A number of studies have demonstrated that the bacteria left in the dentin of a cavity due to any of the above mentioned infection sources could maintain their activities for a long time [1].

Chlorhexidine gluconate-based solutions are the most popular cavity disinfectants. The chlorhexidine application reported a significant decrease in the number of bacteria in the dentinal tubules. The effectiveness of chlorhexidine lies in its chemical charge, as it is a compound which exhibits strong cationic properties. The positive charge of chlorhexidine accounts for its adherent ability and prolonged antimicrobial effect [1].

Using the antibacterial effect of laser depends on the effects produced by laser light in the target cell, tissue, or organism. These effects may be photochemical (the production of free radicals and other reactive species), photothermal, photoablative (the breaking of chemical bonds), or photomechanical (the shock waves produced by the dissipation of a plasma). In general, soft lasers induce only photochemical changes while hard lasers may produce any, or all, of the above mentioned effects depending on the laser type and the conditions under which it is operating [2].

A number of studies demonstrated that different types of lasers have antibacterial effects on different microorganisms. In particular, diode and erbium lasers are able to produce an antibacterial effect on enamel, dentin, and carious tissue with a minimal amount of thermal disruption to the residual tooth [3].

To eliminate the residual caries thoroughly and efficiently, it is important to know the possible antibacterial effect of diode lasers on the microorganisms related to dental caries [4].



The antibacterial effect of CHX (solution, powder) at all concentrations (2% and 0.2%) and diode laser at all powers (1w and 1.30W) in the infected coronal cavities with S. mutans was significantly different from untreated control group.



Our thanks to the College of Dentistry, Mosul University for financial support. We are grateful to the technical help by Basic Sciences staffs.



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