Experimental: Group 1 - probiotic The use of Streptococcus salivarius M18 containing tablets ("Dentoblis", registration number: AM.01.06.01.003.R.000061.07.20; 15.07.2020, MEDICO DOMUS, d.d.o.; 18116, Nis, Serbia)) once a day for 4 weeks (before bedtime after evening brushing).

Ingredients: basic active ingredients - Streptococcus salivarius M18 (≥5×108 CFU in 1 tablet), Vitamin D (320 IU (8 mcg) in 1 tablet); excipients - isomalt (sweetener), magnesium stearate (vegetable), mint flavoring.

The use of placebo tablets once a day for 4 weeks (before bedtime after evening brushing).

Ingredients: isomalt (sweetener), magnesium stearate (vegetable), mint flavoring.

Dissolve the tablets in the mouth once a day for 4 weeks

GI is used to assess visual symptoms of gingivitis on mesial, distal, vestibular, and oral areas of each scorable tooth (1.6, 1.2, 2.4, 3.6, 3.2, 4.4). Each area is given a score from 0 to 3. Values are presented as means across all tooth surfaces with minimum and maximum scores in agreement with minimum and maximum index values (i.e., 0-3). Scoring is performed using standard dental light: 0 = absence of inflammation; 1 = mild inflammation - slight change in color and little change in texture; 2 = moderate inflammation - moderate glazing, redness, oedema, and hypertrophy, bleeding on pressure; 3 = severe inflammation - marked redness and hypertrophy, tendency to spontaneous bleeding, ulceration. Lower scores indicate better results.

GI is used to assess visual symptoms of gingivitis on mesial, distal, vestibular, and oral areas of each scorable tooth (1.6, 1.2, 2.4, 3.6, 3.2, 4.4). Each area is given a score from 0 to 3. Values are presented as means across all tooth surfaces with minimum and maximum scores in agreement with minimum and maximum index values (i.e., 0-3). Scoring is performed using standard dental light: 0 = absence of inflammation; 1 = mild inflammation - slight change in color and little change in texture; 2 = moderate inflammation - moderate glazing, redness, oedema, and hypertrophy, bleeding on pressure; 3 = severe inflammation - marked redness and hypertrophy, tendency to spontaneous bleeding, ulceration. Lower scores indicate better results.

GBI is used to assess bleeding elicited on probing as a measure of gingival condition. Gingivae are air dried and examiner assesses bleeding using a probe which is gently inserted into gingival crevice to depth of app 1 mm and run around tooth (angle of app 60 deg to long axis of tooth), gently stretching epithelium while sweeping from interproximal to interproximal along sulcular epithelium. BI is assessed on mesial, distal, vestibular, and oral areas of each scorable tooth (whole mouth). Values are presented as means across all tooth surfaces with minimum and maximum scores in agreement with minimum and maximum index values (i.e., 0-1). BI score:0=no bleeding after 10 sec, 1=bleeding upon probing after 10 sec or immediate bleeding. Lower scores indicate better results.

A plaque detection solution is used to detect the presence of plaque on both the vestibular and oral surfaces of all teeth except the third molars. Each surface is divided into 3 segments: mesial, central and distal. Thus, 6 segments are evaluated for each tooth. Evaluation criteria: 0 - no staining;

1. - separate areas of plaque in the cervical part;
2. - plaque in the form of a thin continuous band up to 1 mm wide in the cervical part;
3. - cervical part is covered by plaque that is more than 1 mm wide, but less than 1/3 of the tooth crown;
4. - plaque covers 1/3 to 2/3 of the crown;
5. - plaque covers more than 2/3 of the crown.