To investigate the bactericidal effect of probiotics (Streptococcus salivarius M18 and Lactobacillus reuteri) on two types of bacteria (Aggregatibacter actinomycetemcomitans and Actinomyces naeslundii) causing black stains of teeth in vitro.

In vitro:

An unstimulated salivary sample will be taken from patients having black stains. The two types of bacteria of each condition will be cultured, amplified, and measured in the laboratory from the saliva of these patients. After that, one type of probiotics will be applied to these bacteria separately and the same bacterial measurement will be done to evaluate the bactericidal effect of the probiotics on these bacteria, aiming to find the minimal inhibitory concentration of the probiotics.

Inclusion Criteria:

• Patients with black stains on teeth scored via modified Lobene index scores 1-3.
• Medically free patients

Exclusion Criteria:

• Stains other than black.
• Patients on antibiotic treatment or any other medication for the last 2 weeks.
• Patients allergic to prophylaxis powder.
• Parents refusing to participate